INFO 0620

CA9600429

VOL 27N817

Atomic Energy Commission de contrôle Control Board de l'énergie atomique Canada INFO-0620

Two-Phase Counter-Current Flow Limitations in Complex Piping Systems

by

D.G. Noel, M. Shoukri and A. Abdul-Razzak Mechanical Engineering Dept. McMaster University

• i- '":SB|

; mi 1 ' Vi 1 Prepared for the Atomic Energy Control Board i under its Regulatory Research ; and Support Program Ottawa, Canada {

AECB Project No. 2.177.3

December 1995

Atomic Energy Commission de contrôle 1*1 Control Board de l'énergie atomique Canad'â - iii -

TWO-PHASE COUNTER-CURRENT PLOW LIMITATIONS IN COMPLEX PIPING SYSTEMS

A report prepared by D.G. Noel, M. Shoukri and A. Abdul-Razzak, Mechanical Engineering Dept., McMaster University, under contract to the Atomic Energy Control Board.

ABSTRACT

Experiments have been performed to investigate two-phase air-water counter- current flow limitations in two complex geometry test sections. One of the test sections was chosen to represent the complexity of CANDU feeders, at a 1:4 scale. In the second configuration, the effect of declining the horizontal parts of the test section was investigated. For the tested geometry, the results showed that the onset of flooding occurs at lower gas velocity as compared to those required to initiate flooding in vertical tubes or single 90° vertical bends. However, the critical gas velocity at the zero liquid penetration limit was found to be comparable to that of a 90° vertical bend.

RÉSUMÉ On a effectué des expériences pour analyser les limitations de débit à contre- courant air-eau à deux phases dans deux sections d'essai à géométrie complexe. On a choisi une section d'essai pour représenter la complexité des circuits d'alimentation CANDU à une échelle de 1:4. Dans la deuxième configuration, on a étudié l'effet d'une inclinaison donnée aux éléments horizontaux de la section d'essai. Dans le cas de la géométrie analysée, les résultats ont montré que le noyage commence à se manifester à une vitesse de gaz moins élevée comparativement à celle qu'il faut pour amorcer le noyage dans des conduits verticaux ou des coudes verticaux simples à 90°. On a toutefois constaté que la vitesse critique du gaz à la limite zéro de pénétration du liquide est comparable à celle d'un coude vertical de 90°.

DISCLAIMER The Atomic Energy Control Board is not responsible for the accuracy of the statements made or opinions expressed in this publication and neither the Board nor the authors assume liability with respect to any damage or loss incurred as a result of the use of the information contained in this publication. - iv -

EXECUTIVE SUMMARY The objectives of this project were to experimentally examine the nature of counter-current flow limitations in complex piping geometries which are geometrically similar to a CANDU feeder, and to develop empirical relations for the onset of flooding and the zero-liquid penetration limits in such a geometry.

Experiments were performed for adiabatic two-phases, air-water counter-current flow in two test sections. One of the test sections was a representation of the complexity of CANDU feeders (at 1:4 scale). In the second test section, the effect of declining the horizontal parts of the original test section was investigated. The experiments were designed to investigate the effect of test procedure on the flooding limits. Accordingly, for a given liquid flow rate, the flooding limits were obtained by both increasing and decreasing the gas flow rate.

The results obtained for the first test section showed that the onset of flooding limit was encountered at lower gas flow as compared with data available for tubes and single bends. However, the zero-liquid penetration limit obtained in the present work was in reasonable agreement with published data for a single 90° vertical bend. It was also found that, for a given liquid flow, the gas velocities required to cause the onset of flooding and zero-liquid penetration were significantly increased by declining the horizontal parts of the test section. The effect of test procedure, i.e. decreasing vs. increasing gas flow, was found to be less pronounced in the present test section in comparison with published data on vertical tubes. The flooding limits results were empirically correlated. The experimental results also included visual observation of the various flow regimes encountered between the two flooding limits. These observations were summarized in flow regime maps. - V -

TABLE OF CONTENTS

ABSTRACT iii EXECUTIVE SUMMARY iv A. INTRODUCTION 1 1. Background 1 2. Objectives 3 B. EXPERIMENTAL ARRANGEMENTS 4 1. The Test Facility 4 2. The Test Sections 4 3. Instrumentation and Measurements 5 4. Test Procedures 5 4.1 Procedure I 5 4.2 Procedure 2 6 4.3 Procedure 3 6 5. Test Conditions 6 C. FLOW REGIME OBSERVATIONS 7 1. Procedure 1 7 1.1 Flow Patterns Before the Onset of Liquid Penetration . . 7 1.2 Flow Regimes Between the Onset of Liquid Penetration & Deflooding 9 2. Procedures 2 and 3 14

D. LIQUID PENETRATION CURVES 15 1. The 0° Inclined Test Section 15 1.1 Procedure 1 15 1.2 Procedure 2 15 1.3 Procedure 3 15 2. The 5° Declined Test Section 16 2.1 Procedure 1 16 2.2 Procedure 3 16 3. Effect of Test Section Inclination On Liquid Penetration ... 16 E. THE FLOODING LIMITS 18 1. The Zero-Liquid Penetration Limit 18 2. The Deflooding / Onset of Flooding Limit 19 F. CONCLUSIONS AND RECOMMENDATIONS 22

REFERENCES 24 - 1 - A. INTRODUCTION 1. Backoround Flooding is the term given to the phenomenon of two-phase counter-current flow limitations. The two limits which exist for gas-liquid counter-current flow are the onset of flooding, and the zero-liquid penetration limit. The onBet of flooding is reached when, for a given upward gas flow, the amount of water that penetrates the tubing cannot be increased by an increase in the water injected at the top. Increasing the gas flow from this point will restrict the water penetration more and more until zero water penetration occurs. The flooding phenomenon is important in many practical applications, the most critical being some postulated loss of coolant accidents (LOCAs) in nuclear reactor safety. For instance, the CANDU feeders, which emergency cooling water must travel through to reach the fuel channels, are very complex in geometry and prediction of the flow limitation in them is very important. Over the years, work has been done in order to predict flooding in various simple geometries, however, widely applicable models are lacking because the mechanisms involved are not yet really understood. Most of the earlier work has been done for vertical and horizontal channels, but more recently geometries such as vertical-to-horizontal or near-horizontal pipes, and vertical-to-inclined pipes have been studied. Excellent reviews for flooding in vertical tubes were published by Bankoff and Lee (1986) and Tien et al. (1979). The most widely, used correlation for the onset of flooding is that from Wallis (1969),

Pc where the dimensionless group j£ represents the ratio between inertia and buoyancy forces for phase k (k=G for the gas phase and k=L for the liquid phase). J'J* is defined by, '/4 .

where j, p, D, and g are the superficial velocity, density, tube diameter, and gravitational acceleration respectively. The constant m is close to unity if no mass transfer occurs between phases. The constant C depends on entrance effects, and has been found to range between 0.7 and 1.0. This model will predict liquid delivery throughout partial flooding as well as the point of complete flooding. The correlation was found to be reasonable, however it does not take into account the effect of tube length. The critical gas flow required to cause zero-liquid penetration, can be

obtained from the above model by setting jL =0, giving

jr = c2 = Constant (A. 3)

Wallis (1969) proposed the following correlation: jr = 0.5 (A.4) JG Critical ' which implies a dependence on tube diameter of the form

JG«JD (A.5)

Pushkina & Sorokin's (1969) correlation for complete carry-up is based on the Kutateladze number, given by Ku- & j° (A.6) 9 o (PL ~ PG)1 where o is the surface tension. The Kutateladze nunnber is similar to JQ , except that it is based on a characteristic wavelength, £, instead of tube diameter, where

(A.7) - PG) Pushkina & Sorokin found that at zero penetration, Ku = 3.2 for different size pipes. This implies that the superficial gas velocity must also be constant independent of D, contrary to Wallis' findings. Later, Wallis and Kuo (1976) and Richter (1981) reconciled the disagreement by Bhowing that the critical gas velocity at the zero-liquid penetration limit to be independent of pipe diameter only for D>10 cm. Wallis & Dobson (1973) did experiments over a wide range of horizontal channels for co-current, counter-current, and zero liquid flow. During their experiments, they adjusted the channel slope to keep a uniform average liquid depth. The onset of flooding was attributed to the formation of large waves or slugs. They proposed the correlation for the onset of slugging as

1 jG = 0.5 a?' (A.8) where a is the void fraction. Because the liquid velocity was much smaller than the gas velocity, this correlation fit the data well regardless of direction of liquid flow. In the case of counter-current flow, the slugs caused flooding in that they limited the allowable liquid flowrates. Wallis & Dobson explained the factor of two between their correlation and the criterion from the classical Kelvin-Helmholtz instability by the fact that the latter is based on one dimensional theory whereas the real situation of two dimensional flow facilitates slug formation. A theoretical analysis was done to predict the onset of horizontal slugging by Mishima & Ishii (1980). Their analysis was based on theory of finite waves and the formation of a "most dangerous wave". The final result was the slug formation criterion for the deep water case.

VG - VL S 0.487 the jump was very weak and difficult to observe. AB the air flow was increased, the jump was dragged toward the elbow and eventually a slight increase in air flow initiated slugging at the crest of the jump, where the gas velocity is maximum. Siddiqui et al. briefly studied the effect of a slight inclination (about 0.6 deg.) of the horizontal leg. They found that the hydraulic jump was very sensitive to pipe inclination. For a slight upward inclination, the gas flow required for flooding was greatly reduced. For a slight downward inclination, the jump was difficult to see, and the gas flow for flooding was greatly increased. These observations were also seen by Wan & Krishnan (1986) and Krishnan (1987). Ardron S Banerjee (1986) used a two-fluid model to develop a theoretical model - 3 - to predict the flooding limit based on the formation of a hydraulic jump. They included the effects of horizontal tube length, diameter, and inclination. The resulting model agreed reasonably well to the experimental data of Siddiqui et al. (1986). Kawaji et al. (1991a) studied the flooding mechanisms in vertical to inclined pipes, using inclinations of 112.5, 135, and 157.5 degrees from the vertical. They found that the gaB flowrates for flooding were well above those for vertical to horizontal tubes. These results are attributed to the fact that no hydraulic jump was observed in the inclined tube. This allowed the liquid velocities to remain high, and the liquid levels to be significantly lower than those where a hydraulic jump was present. Furthermore, flooding was found to occur just downstream of the elbow, and the mechanism changed with liquid flowrate. At lower liquid flowrates, flooding was attributed to counter-current slugging, and at higher liquid flowrates the flooding mechanism becomes that of entrainment/carryover of droplets generated from the "turbulent jet-like stream" which formed through the elbow.

Recent work by Kawaji et al. (1991b) investigated flooding in three different piping systems containing multiple elbowB and an orifice. All three systems consisted of differently arranged vertical, horizontal, or inclined sections connected by three elbows. In all cases (for no orifice), the onset of flooding data agreed well with, or was less restrictive than Ardron & Banerjee's onset of flooding curve for 90 degree elbows. The mechanism of flooding in the most restrictive system was attributed to a prolonged hydraulic jump throughout multiple continuous horizontal sections.

The need to examine the flooding characteristics in geometries similar to those of CANDU feeders was identified by Shoukri (1990) and accordingly the present work was initiated. 2. Objectives The overall objective is to investigate the two-phase counter-current flow phenomena in a complex geometry relevant to that of the CANDU feeders. The experimental observations and data are used to: (i) examine the nature of the phenomena leading to the onset of flooding and zero liquid penetration limits under conditions of increasing and decreasing gaB flow in a complex pipe geometry,

(ii) develop empirical correlations for the above limits, and (iii) examine the existence of a "critical section", in which onset of flooding is likely to start. To achieve these objectives, air-water experiments were carried out using two test sections. The first is modelled after a typical CANDU reactor feeder tube, with multiple elbows, vertical, and horizontal sections (referred to as the "0° inclined test section"). The second is basically the same construc- tion except that all the horizontal sections have a 5 degree downward inclination (referred to as the "5° declined test section"). - 4 -

B. EXPERIMENTAL ARRANGEMENTS

1. The Teet Facility The test sections examined in the present work are modelled as representations of the complexity of feeder pipes in a CANDU reactor at approximately 1/4 scale. The test facility is shown schematically in the accompanying figure B.I. In addition, the test facility can be Been in figure B.2. The main components of the loop are the mixer (sometimes referred to as a sinter), the lower tank, the separator tank, and the test section. Diagrams of these components can be found in figures B.4 to B.6. Water from the storage tank was pumped, filtered, metered and introduced to the mixer. The mixer schematic is shown in figure B.4 and a photograph is included in figure B.3. The mixer consisted of two concentric tubes; the inner was an extension of the 3/4" I.D. test section tube, which had about 300 holeB of 1 mm diameter drilled into it. The inner tube extended about 5" up inside the separ- ator tank, as shown in figure B.4. The water was pumped between the concentric tubes and entered the inner tube through the fine matrix of holes which promoted an even water film on the inner wall.

Before the air was injected to the lower plenum, the pressure was regulated, and the flowrate measured. From the lower plenum the air went through the test section from the lower end, and was exhausted from separator tank.

Water which penetrated the test section was collected in the lower tank. The air/water mixture that was carried up to the upper tank, was separated. The air was vented, while the carry-up water was measured and then drained. The first test section analyzed was that most resembling the complex geometry of a typical CANDU reactor feeder. It consists mostly of vertical and horizontal sections connected by 90 degree elbows, except the two uppermost elbows of 45 degrees. This test section will be referred to as the 0° Inclined Test Section.

The second test section was built with the same configuration as the first, but all the horizontal sections have been given a 5 degree decline. The overall height of the test section was kept the same by decreasing the length of the vertical sections on a weighted basis. This test section will be refereed to as the 5° Declined Test Section.

2. The Test Sections The 0° Inclined test section, depicted in figure B.7, was made of transparent PVC tube of a nominal 3/4" I.D. (actual I.D. was 0.804"). All elbows were 90 degrees except the two uppermost which were 45 degrees (not Bhown in figure). Much consideration was given to keep each individual section as horizontal or as vertical as possible, to avoid any effects of inclination. The lower end of the test section was connected by a sharp edged flange to the large lower tank. The upper end was connected to the sinter mixer, where the water was introduced to the inner wall of the test section. Attempts were made to have a smooth tube to elbow transition. The 90 degree elbows had a radius of curvature about 0.5", and an inner diameter of just under 1". Due to the difference in tube and elbow inner diameters, there was a small step encountered from the tube to the 90 degree elbows which could have some effect on the water flow pattern. This step is not present in the 45 degree elbows.

To facilitate the discussion of specific parts of the test section, the elbows have been numbered from 1 through 9, starting at the uppermost 90 degree elbow. Also, the small section above this uppermost elbow, consisting of three short sections and two 45 degree elbows, is referred to simply as the "neck" of the test section [see figure B.7]. The pressure gradient along this test section was measured from five carefully placed pressure tappings. Tappings were placed at the upper and lower ends of the test section so that the total pressure drop could be measured while the - 5 - remaining three were placed in intermediate positions, as shown in figure B.8. The tapping at the lower end of the teBt section was attached to a 5 psi pressure transducer. The other four tappings were connected to the other Bide of the transducer by means of a four position valve. The pressure tappingB have been numbered from 1 through 5, beginning with the uppermost tapping [figure B.8). The 5° Declined test section, depicted in figure B.9, was made with the same transparent PVC tube as the first test section. Seven 95° elbowB were constructed as close as possible to the 90° elbows with respect to radius of curvature and inner diameter. The lower end of the test section is connected at a 5° decline to the lower tank by a sharp edged flange. The upper end is connected, as before, to the sinter mixer.

The elbows have been numbered in the same way as were those of the previous test section [see figure B.9]. Just two pressure tappings were employed in this test section, measuring only the total teBt section pressure drop. One tapping was located just under the mixer, and the other just before the lower tank. The pressure tap locations are shown on figure B.10.

3. Instrumentation and Measurements

The air flow rate was measured through one of three rotameters connected in parallel. Dwyer rotameters were used for moderate and high air flows, between 60 and 600 SCFH. A low range Fischer and Porter rotameter was used for flows from 5 to 66 SCFH. The rotameter pressure was measured with a 0-100" H2O pressure gauge. The measurements were corrected for the operation using standard procedure.

The water feed rate was measured through two parallel Dwyer rotameters which cover the range of 0.2 to 3.0 GPM (US). Pressure measurements were made between lmm tappings placed in the test sections. The tappings were connected by short tubes to 6" long X 2" diameter horizontal cylindrical reservoirs. The reservoirs collected water which leaked through the tapping holes, but were periodically drained to maintain a constant water level. The upper reservoirs were connected to one side of a 5 psi pressure transducer by water filled tubing, while the lowermost reservoir was used as the reference on the other side. The transducer was in turn connected to a signal processor which drove a Phillips chart recorder.

The lower tank pressure was measured by a 0-15 psi gauge, which was supplemented by a 1 metre water manometer for the 5° declined test section experiments.

Water carry-up was measured by collecting it in a graduated container while timing it with a stopwatch. 4. Teat Procedures Three different test procedures were performed in order to gain insight into the effect of procedure on the flooding mechanism. In order to facilitate discussion, the three procedures will be referred to numerically as procedures 1, 2, and 3.

4.1 Procedure 1 The first test procedure was started by establishing high air flow through the teBt section, leaving the test section walls dry. A prescribed water flow was then injected into the mixer, all of which was initially carried upward because of the high air flow. The air flow was then slowly decreased in steps, allowing stability to be reached, until the air injection to the lower tank reached zero. Care was taken to ensure constant water injection throughout the test. The onset of liquid penetration was determined by the point where water first succeeded to penetrate the test section. The point of deflooding (onset of flooding) was determined by the air injection rate at which water no longer was carried above the injection point. Because flooding actually ceases here, this point is sometimes referred to as 'deflooding'. - 6 -

4.2 Procedure 2 The second test procedure was an extension of procedure 1 which was studied only during the 0° inclined tests. At the end of procedure 1, once the air injection was reduced to zero and without venting the lower tank, the air was increased in increments until all water was carried up. The onset of flooding was determined by the air injection rate at which water was first carried into the upper tank. The zero-liquid penetration limit was determined by the point at which water ceased to penetrate the test section.

4.3 Procedure 3 The third test procedure was started with no air injection, allowing all of the water injected to penetrate the test section. The lower tank was vented to negate any air being forced into the test section. The lower tank vent was then closed, which forced the displaced air through the test section, however zero air was injected into the upper tank. The air injection to the lower tank was then slowly increased in steps, allowing the system to stabilize between each, until sufficient air flow existed to carry all injected water into the upper tank. The flooding limits were determined in the same manner as in procedure 2.

The difference between procedures 2 and 3 is that in procedure 2, the initial condition in the lower tank is a slightly compressed air. 5. Test Conditions

In tests on the 0° inclined test section, the nondimensional water velocity was in the range of 0.06 < jL* < 1.0. For tests on the 5° declined test Bection, the dimensionless water velocity was varied in the range 0.06 < jL* < 0.52, due to limitations of the facility. In all testB the dimenBionless air velocity was varied in the approximate range of 0 < JQ* < 0.65.

The tests were all conducted near room temperature and atmospheric pressure. - 7 -

C. FLOW REGIME OBSERVATIONS

During the tests, a number of flow regimes were observed over the range of water injection. These flow regimes can be 'mapped' into a graphical form. This presentation will give the reader an idea of the flow regimes that occurred under different air and water injection rates.

The flow regime maps are presented in figures C.I to C.4. The transitional boundaries varied according to test section inclination and test procedure. The boundaries which appear on the figures are subjective, and were drawn only to group the observed flow regimes.

In the following description of the observations, many references to specific test section elbows, which are numbered from 1 to 9, are made. Please refer to figure B.7 for elbow identification and location. Also, numerous references are made to specific sections of the test section. A reference Buch as 'section 4- 5', for example refers to the section between elbows 4 and 5.

In addition, many references to flow patterns such as churn flow, slug flow, or pulsing are made. These flow patterns are defined as follows.

Churn flow is the term given to chaotic air-water flow observed in the vertical tubes of the test sections. Chaotic agitation of the water existed, but no clear slugs or bridging was observed. Slug flow is the term given to flow in which clear slugs were observed. A slug was considered to be associated with the water bridging or nearly bridging the tube.

Puising is defined by the flow pattern where large waves were formed aB water attempted to flow through an elbow from a horizontal (or 5° declined) section. The counter-current air flowing through the elbow would catch the water as it attempted to pass the elbow and create a large wave which it would push back away from the elbow in a pulse.

To describe the typical flow regimes, procedure 1 is considered first. In following sections, procedures 2 and 3 will be described in terms of their differences to procedure 1. 1. Procedure 1

The flow regime maps corresponding to the 0° and 5° test sections for procedure 1 appear in figure C.I and C.2, respectively. Firstly, the flow patterns observed before the onset of liquid penetration for each test section will be described. Secondly, the flow regimes observed between the onset of liquid penetration and deflooding will be described. 1.1 Flow Patterns Before the Onset of Liquid Penetration

The following description concerns the range of the procedure from the point where the first water entered the test section from the mixer to the onset of liquid penetration. From the figures, these two limits were highly independent of the water injection rate for either test section. Accordingly, the flow patterns observed between these limits were also highly independent of water injection.

The gap between the point where water first entered the test section and the onset of liquid penetration (shown on the figures) represents the air flow reduction required to allow the water to penetrate through the test section. It is obvious that larger reduction in air flow is required to cause water penetration for the 0° test section compared to the 5° teBt section. a) The 0° Inclined Test Section

For high air flow rates at the beginning of the procedure, all of the injected water was pushed into the upper tank from the mixer. It was only when the air flow was decreased between 290 and 260 CFH (/jo* = 0.72) that some water began - 8 - to trickle from the mixer into the upper neck of the test section. At this point the water entered the test section in an annular film and descended through the neck aB churn to elbow 1 [figure C.5). The water only advanced about 1" past elbow 1, and was held there as the air flowing upward held the water back.

When the air flow was decreased to about 200 CFH (/jc* = 0.61), the water advanced as a stratified layer, which was thicker at the front as the water tried to advance over the dry surface. The thick water front was very susceptible to the counter-current air flow. Accordingly, surface waves were regularly formed from the water front.

Eventually, the water advanced to elbow 2 and pulsing began in section 1-2 as large, regular waves were formed from elbow 2 because the air flowing around this elbow caught the advancing water at its front. These waves would then hit elbow 1. causing agitation above this elbow and sending a reflected wave back to elbow 2. It was this reflected wave that produced the next pulse from elbow 2. This effect may have been enhanced by the lack of a completely smooth transition at the elbows.

As the air flow was then decreased from 200 to 120 CFH (VjG* «= 0.61 to 0.47), the water front progressively moved toward elbow 3 [figure C.6]. The photograph shows the water advancing as a relatively smooth stratified layer, with a small single pulse wave from the counter-current air flow. When the air flow reached about 120 CPH (VjG* = 0.46), the water front was right at the edge of elbow 3, but was not able to advance further as the air came up and around elbow 3 [figure C.7). Flow pulsations continued in section 1-2, aB described aoove, originating from elbow 2. These were now accompanied by lower frequency pulsations (because of a longer section length) in the horizontal section 2-3, originating from elbow 3. In general, the stratified liquid layer was thicker upstream and the pulsating flows were more violent in the upstream section 1-2 as compared to section 2-3, sustaining churn and slugging in the upper neck of the test section. These surface waves tended to be larger with decreasing air flow as more water was allowed into the test section.

Water finally advanced past elbow 3 once the air flow was reduced between 115 and 100 CFH (OG = 0-45). Elbow 3 was the last point of complete water restriction, so the water would eventually reach the lower tank without further air flow reduction, identifying the onset of liquid penetration. The interaction between the advancing thick liquid film and the counter-current air flow at the vertical-to-horizontal elbow 7 resulted in the formation of a churn-like flow in the vertical section 6-7. But once the liquid passed elbow 8, the liquid level in section 7-8 decreased noticeably and the churning effect at elbow 7 disappeared accordingly. However, the same phenomenon was repeated at the vertical-to-horizontal elbow 9.

The water depth in the horizontal section from elbow 9 to the lower tank remained thicker than that in section 7-8; even after the water front reached the lower tank. This suggests that entrance effects somehow restricted the water from exiting the test section as compared to entering a horizontal to vertical elbow such as elbow 8. The end result was sustained churn and/or slugging in section 8-9 as depicted in figure C.8. It iB also interesting to note that this churn pattern did not generally occur at the upstream vertical to horizontal elbow 4, suggesting that the length of the vertical and/or the horizontal sections can influence this behaviour.

At this point, the air flow was high enough to cause water obstructions in elbow 9, as seen in figure C.8, sustaining the churn. No hydraulic jump was observed to initiate the churn or slugging at the elbow. This is partly attributable to the fact that a small radius of curvature to diameter ratio (Rc/D) existed (=0.6). The formation of a hydraulic jump in the horizontal section of a vertical elbow was observed by Kawaji (1991a) for elbows having Re/D = 3. However, Siddiqui et al. (1986) observed the hydraulic jumps to become weaker with smaller elbow radius. The churn seemed to start instead during the water transition from the vertical annular flow to horizontal stratified flow. As the air travelled through the relatively small passage above the liquid surface, it entrained the water as it descended, and created the churn above the elbow. - 9 -

Although only a small amount of water actually came down/ more water fell into section 8-9 than was allowed to pass through the churn at elbow 9. As a result, the churn grew higher in section 8-9, and slugB became more and more prevalent. The above was observed in almost every case, regardless of water injection, however some variance occurred as the system was left to reach steady Btate. In mo3t cases, the slugs and churn continued to grow in section 8-9, until the complete section was engulfed. As the slugs encountered elbow 8, blockage occurred and slugB formed that were sent from elbow 8 toward elbow 7. The longer this occurred, the more violent it became. Shortly after, the slugs reached elbow 7, churn and slugging in section 6-7 were established. When strong, this process continued to spread upward until pulses and/or Blugs eventually reached the neck and were pushed to the upper tank. However, some instances occurred where the flow pattern was not strong enough to push water all the way to the upper tank. This flow pattern will be referred to as section-to-section carryover. The pulsing and slugging in section 1-2 continued to occur through the whole refilling process. b) The 5° Declined Test Section

The flow patterns encountered in the 5° declined test section before the onset of water penetration were generally similar to those encountered in the 0° inclined test section. The major difference was that the water was able to penetrate the test section further as compared with the original test section at a given air flowrate. Moreover, the intensity of flow pulsation between elbows 1 and 2 encountered in this test section was weaker than in the original one, and accordingly, the agitation above elbow 1 was weaker.

Interestingly, elbow 3 was observed to control the onset of water penetration as it did in the original test section by being the location where, once reached, the water would eventually penetrate the test section without further reduction of air flow. Figure C.9 shows a pulse or wave shot upstream from elbow 3 as the water tried to flow past it.

Finally, because of the declined sections of this test section, the first water penetration into the lower tank was not in a continuous stream, but instead did so in a piece-wise manner. The water would collect in section 4-5 after a wave of water 'splashed' past elbow 3. Once enough water was collected, it would advance past elbow 6, and continue on down to elbow 7. No more water would follow until sufficient water again collected in section 4-5. Each time that water advanced past elbow 6, it would advance as a separate water front, with waves formed as the air flowed over the crest of the front. This discontinuous water penetration is what is meant by piece-wise flow. As each separate water accumulation moved down the test section, waves from the water front caused churn as it moved by elbow 7, then pulses at elbow 8, then churn again at elbow 9.

1.2 Flow Regimes Between the Onset of Liquid Penetration S Defloodina As mentioned above, a number of distinct flow regimes were observed during the experimental testB which for procedure 1, were mapped on figures C.I and C.2, for the 0° and 5° test sections, respectively.

When looking at the flow regime maps, it is important to realize that the flow regimes are closely related to one another. Each regime can be related to an increase in the restriction of a specific portion of the test section, however the flow is always restricted in varying degrees by a number of portions of the test section. This will be elaborated in the following discussions. a) The 0° Inclined Test Section

In figure C.I the flow regimeB observed between the onset of liquid penetration and deflooding are shown. From the figure, it is evident that the flow regimes not only varied during the procedure as the air injection was decreased, but also that they are dependent on the water injection rate. i) Pulse Flow in Section 1-2 (Calm below) This flow regime was characterized by strong pulsations in section 1-2 while the test section below elbow 2 remained calm. As described in section 1.1 a, the - 10 - pulse flow was originated from elbow 2 as the air caught the water waveB as they tried to round the horizontal elbow. Because section 1-2 was quite short, the frequency of the pulses was rather high. The waves or pulBes colliding with elbow 1 sustained strong slugging and churn through the test section neck up into the upper tank. The fact that the lower sections remained calm suggests that these sections were less restrictive to water flow than section 1-2. This flow regime was consistently observed in a thin band just below the onaet of water penetration (0.43 > ^JQ* > 0.41) across the entire range of water injection. It was also observed in a small section to the right of the onset of flooding curve at low air injections (OG*< 0.18).

ii) Pulse Flow in Section 1-2 (Slugging from Elbow 9\ This flow regime was characterized by strong pulsation in section 1-2, just as described above, however, this was accompanied by significant slugging above elbow 9. This slugging above elbow 9 was too strong to ignore, yet not strong enough that slugs and/or waves were carried over to upper sections aB was the case during section-to-section carryover. In this flow regime, the restriction from elbow 9 began to emerge, but did not affect the liquid penetration through the test section.

This flow regime appeared for moderate and high water injection rates, once the air injection was decreased below about /JQ* = 0.41. The lower air flow allowed more water to penetrate past elbow 2, which allowed the slugging above elbow 9 to initiate. iii) Section-to-Section Carryover This flow regime was characterized by the section-to-section carryover that was described in section 1.1 a. This flow regime was mainly observed at the lower end of the water injection scale (\/JL* < 0.45).

For low water injection rates, as the air was gradually reduced from about 90 CFH (^JG* = °-41)/ tne general observation waa continued section-to-section carryover, which iB depicted in figures CIO to C.14. Figure C.ll shows the flow at elbow 8 while the cycle was relaxed, and slugs from elbow 9 did not reach elbow 8. Figure C.12 shows a clear slug just after formation at elbow 8 as it headed towards elbow 7. The slugs were not always strong enough to bridge the tube, as shown in figure CIO. Once a slug reached elbow 7, a temporary blockage occurred while the downstream air pressure recovered, as depicted in figure C13. Churn and slugging then ensued above elbow 7. This section-to-section carryover generally appeared to get weaker with decreasing air^injection. For instance, with reduced air flow the slugs formed at elbow 8 were less frequent and severe, which in turn made the slugging process in adjacent sectionp less severe and less likely to send slugs into the upper tank. Usually, the] process diminished to the point where the churn and slugs from elbow 9 no longer reached elbow 8 at all, as shown in figure C.14. Throughout the process, however, the water was continually being restricted and carried up due to the persistent pulse flow in section 1-2.

When the entire test section was consumed in churn and slugging during strong section-to-section carryover, less water actually reached elbow 9 which insti- gated the whole process. The decreased water flow into section 8-9 relaxed the slugging and slowly the test section returned to a calmer state. From this point, the process above started over again and continued in a perpetual cycle. The total pressure drop recordings of figures C.15 and C.16 show the characteristics of these fluctuations during section-to-section carryover.

iv) Violent Cyclic Flooding (VCF^

This flow regime waB observed as the air injection was decreased below >/jG* = 0.33 for high water injection rates. A very Bimilar regime was observed by Ohnuki (1986) for flow through 40 and 45 degree inclined sections connected to a horizontal leg. MoBt interestingly however, is that he observed the flow regime to occur once the air injection was decreased between \/ jG* = 0.3 and 0.4 (depending on the length of the horizontal leg), which is very comparable to the - 11 - value observed for both test sections of the present work. The flooding cycle typically started when a large water slug waB formed in section 1-2 creating a water blockage, which momentarily reduced the air flow to near zero as shown in figure C.17. In every case the blockage was initiated by a large slug from elbow 2. This blockage allowed the water below this level to drain down to the horizontal sections creating blockages in the longer ones near elbows 9 and 7. This water drainage process is clearly depicted in figures C.18, C.19, and C.20. As the water continued to drain down, water columns started to form in the vertical sections at these vertical elbows as shown in figures C.21, C.22, C.23, and C.24. Meanwhile, almost complete blockage of air flow through the test section resulted in slow pressure rise in the lower tank.

Describing the test section at this point from the bottom to the top, there was a stratified water layer at the entrance to the lower tank followed by water blockage to the top of the water column above elbow 9. An air pocket existed above this column which extended into section 8-7. The air pocket terminated at the water blockage near elbow 7 which continued to the top of the column over elbow 7. Again, an air pocket existed above this column which extended up in between elbows 5 and 4, Another column existed over elbow 4, which pushed another air pocket which exiBted above it and extended to a point near elbow 2. The test section from elbow 2 on up through the neck and into the mixer was completely filled with water at this point. Summarizing, the teBt section consisted of a series of water blockages at the vertical to horizontal elbows, coupled with large air pockets which were pushed upward as the columns grow.

Meanwhile, the air pressure in the lower tank built up as the air was being injected into the tank but could not be vented. At the same time, the water was not completely stopped from penetrating the test Bection. In fact, at this point of the cycle there was substantial water penetration. Finally, the air pressure in the lower tank approached that required to overcome the hydrostatic head of the water columnB, and the air pocket from the tank approached elbow 9. This air pocket is visible in figure C.23. As the air pocket advanced, more of the tube cross section was occupied by air. Because of the increased water restriction, the water column over elbow 9 rose, and the air pocket in section 8-7 approached elbow 7. However, the governing section was elbow 9. If the air pocket in section 8-7 reached elbow 7 before the air pocket from the lower tank reached elbow 9, the excess air was merely vented through the water column at elbow 7 in the form of Taylor-type bubbles as shown in figures C.25 and C.26. The air pocket in the horizontal section of figure C.25 was clearly at the very edge of elbow 7, yet the system did not erupt. It was not until the air plug from the lower tank reached elbow 9 that the air accumulated in the tank was released through the test section in a violent cocurrent burst. As the air rushed upward, most of the water in the test section was carried up into the upper tank. Figure C.27 shows the air pocket at elbow 9 just after it started to ascend the section. Simulta- neously the air pockets in the rest of the test section start their ascent. Once the air pockets begin to climb the test section, the violent air burBt ensues, as seen in the figures C.28 to C.32, inclusively.

With the pressure in the lower tank near zero, the water again rushed down the test section, creating the water blockages and columns as before. With this, the cycle started again. Generally, the VCF was observed to become stronger as the air injection was further reduced, and was weaker at the same air injection for lower water injections. The VCF continued even when zero air was injected into the lower tank because of pressurization of the existing air already present as the water was collected in the lower tank. Typical recordings of the total pressure drop acrosB the entire teBt section are rovided in figures C.33, C.34, and C.35, corresponding to water injections of fjL* •= 0.719, 0.881 and 0.928, respectively. It is shown that VCF was characterized by a smooth, steady increase in the total test section pressure drop, followed by a sharp decline. After a short pauBe, the cycle duplicated itself quite accurately. The period of the cycles also appeared to increase with decreasing air injection in each figure. However, the amplitude of the cycles - 12 - appeared to be less affected by air injection rate once VCF began. The steady, smooth increase in test section pressure drop represents the increase in hydrostatic head in the test section as the columns of water were formed in the test section. Eventually, the air pressure in the lower tank increases to a point where the hydrostatic head was overcome. The result was the release of the pressurized air in the test section in a violent cocurrent flow which showed up on the recordings as a sudden decline in pressure drop immediately after the air was released.

In order to discern a curve for the onset of VCF, arbitrarily any cyclic flooding cycleB with an average test section pressure drop over 0.90 psi was considered to be VCF. This limit generally coincided with the point at which the cycles became clearly repetitive.

As the air injection was decreased below the onset of VCF, both the period and amplitude of the total pressure drop cycles generally increased. Interestingly, however, with increased water injection over i/jL* = 0.7, no change in cycle amplitude or period is obvious.

Another important aspect of the test facility that must be considered is the size of the lower tank. The results obtained during VCF will be somewhat dependent on the size of the lower tank. This was due to the fact that in the cases of high water injection, the air pressure accumulated in the lower tank was key to the flow process. The lower tank size also affected the experiment in that as the tank collected the penetrating water during an experiment, its air volume decreased which would affect the frequency and amplitude of the pressure fluctuations. It was attempted to keep this effect to a minimum by not allowing the lower tank to fill more than about 30%. v) Small-Scale Cyclic Flooding The small-scale cyclic flooding regime represents that in which the cyclic flooding phenomenon was observed, but was too weak to be considered as VCF. That is to say that the average amplitude of the total pressure drop through the test section was below 0.90 psi.

The SCF began with a water pulse from elbow 2 temporarily blocking the test section at elbow 1, and allowing water to rush down the test section, much as was described for VCF. The water rushing down the test section, without counter- current air flow, again caused blockages at elbow 9 and/or elbow 7. The blockages would induce periodic cycles, much like the VCF cycles described above, however these cycles were much smaller, less violent, and less distinct. The water blockages would not hold the air in the lower tank very long, and the ensuing burst of air through the test section was too weak to clean the test section of the accumulated water. The water that remained in the test section could easily penetrate the test section and enter the lower tank once the air from the lower "tank was released.

With successively lower air injection rates or increased water injection rates, these cycles were observed to become somewhat stronger in the range that they were observed.

Figure C.36 shows the total test section pressure drop recording during SCF for the water injection test /jL* = 0.511. The indicators on the figure show the points where the pressurized air was released from the lower tank. b) The 5° Declined Test Section

In figure C.2 the flow regimes observed between the onset of liquid penetration and deflooding for the 5° declined test section are shown. From the figure, it i8 evident that the flow regimes observed bear interesting resemblances to those observed for the 0° test section. These will be pointed out as the flow regimes are discussed individually. i) Water Restriction From Elbow 3

This flow regime was characterized by restriction of the flow by large waves and slugs pulsating from elbow 3, and occurred as the air injection rate was - 13 - decreased down to about 200 CFH [VjG* = 0.61]. The decline through section 1-3 increased the water flow to elbow 3 as compared to the 0° test section. A pulBe or large wave was formed from elbow 3 as the accelerating water front met the restriction imposed by the elbow and the air flow around it. However, the agitation above elbow 1 and in the test section neck was light compared to that observed in the original test section.

Also, it is important to note that during the high air flows of this flow regime, similar observations were made at elbow 9, as significant waves were pushed from the teat section exit in the lower tank toward that elbow. Some such waves are shown in figures C.37 and C.38. These waves caused continual churn above elbow 9, as the air tended to push the wave up elbow 9. ii) Section-to-Section Carryover

The section-to-section carryover observed for the 5° declined test section can be described the same way as it was for the original test section. The difference was in the way that this flow regime was initiated for the 5° test section. The slugging was initiated by the waves that were sent to elbow 9, as described in the previous section. With lower air injection, the increased amount of water which flowed down caused larger waves which allowed the slugging and churn above elbow 9 to spread up the entire test section. Figure C.39 shows a wave approaching elbow 9. The churn above elbow 9 would eventually grow into strong slugging. FigureB C.40 and C.41 show large waves travelling from elbow 8, after the churn in section 8-9 reached elbow 8. iii) Water Restriction From Mixer This flow regime was characterized by counter-current flow with smooth interfaces throughout the test section. The flow regime was observed as the air injection was decreased through the range between 180 and 100 CFH [0.58 > VjG* > 0.43], for water injections 7jL* a 0.35. At this point, the resistance to the flow from elbows 2 and 3 all but disappeared, and consequently the agitation at elbow 1 and in the test section neck also disappeared. The very calm test section neck and section 1-2 is shown in figure C.42. Also, the lack of restriction from elbow 3 is shown in figure C.43. In both figures, the air-water interfaces are smooth. The water entering the teBt section was limited by the mixer itself, as most of the water was entrained by the air and carried to the upper tank before even reaching the test section. iv) Pulse Flow in Section 1-2

This flow regime was characterized by the emergence of pulse flow in section 1-2 originating at elbow 2 in a fashion similar to that described in the other test section. The pulses from elbow 2 were also accompanied by the occasional pulse or slug from elbow 3 or even elbow 5. The test section below elbow 5 was observed to be quite calm for the most part. v) Violent Cyclic Flooding (VCF) This flow regime represents the same basic cyclic flooding phenomenon that was described in section 1.1 a. AB for the 0° test section, the onset of VCF was always initiated by a large slug from elbow 2, which caused a momentary blockage above elbow 1. Also, as in the 0° test section, elbow 9 was still observed to be the key elbow which governed the air release from the lower tank. However, due to the decline of the section between the lower tank and elbow 9, it was easier for the air pocket to reach elbow 9.

For high water injections, this effect was offset somewhat because of the faster rate of water that drained down the teBt section during the pressurization part of the cycle. In fact, at low air injections, the water penetration was so high that the air pockets in the test section were often actually pushed down by the water into the lower tank. Also, some cases were observed in which the air pocket passed elbow 9 on its way to elbow 8, only to be pushed back down toward the lower tank. - 14 -

Figures C.44 and C.45 show the total pressure drop recordings for water injection tests of •! jL* = 0.647 and 0.706. As the air injection is decreased, the increase in strength and definition of the flooding cycles is obvious. vi) Small-scale Cyclic Flooding (SCF) This flow regime was the same as that described earlier. It is differentiated from the VCF because the cycles were much weaker and often occurred only in select parts of the test section. Also, during the air release part of the cycle, often only small portions of the water accumulated in the teBt section were carried to the upper tank. 2. Procedures 2 and 3 Tests were carried out on the 0° inclined test section using both procedures 2 and 3. The 5° test section was examined using procedure 3 only. With respect to observed flow regimes, no difference was found between the two procedures. In fact, the only difference observed between the procedures was a slight deviation in the onset of flooding curve. The procedures appeared identical in the water injection range where cyclic flooding occurred, because the transient nature of the cycles negated any effect of air pressure in the lower tank (the pressure of the lower tank at the beginning of the test was the basic difference between procedures 2 and 3).

Figure C.3 shows the flow regime map for the 0° test section during procedure 2. Excepting minor boundary shiftB between flow regimes, figure C.3 was remarkably similar to the flow regime map for procedure 1 (figure C.I). The boundaries for the cyclic flooding regimes were almost identical.

Figure C.4 shows the flow regime map for the 5° declined test section during procedure 3. Again the resemblance to the map of figure C.2 for the same test section during procedure 1 was remarkable. However, it appeared that the procedure had a stronger influence on the flow regimes for the 5° test section than was Been for the 0° test section. This was probably due to the fact that the complex network of piping in the 0° test section had such an influence on the flow, that procedure did not matter. However, the 5° declined test section was much less prohibitive to the flow, and procedure showed more effect. - 15 -

D. LIQUID PENETRATION CURVES

Liquid penetration curves were generated for the test runs by plotting the water penetration against air injection, for a given water injection rate. The curves for the 0° inclined test section are presented in figures D.I to D.7, inclusively. Those for the 5° declined test section are presented in figures D.8 to D.ll, inclusively. All the values of jL* and jG* given in the figures are based on the measured flow rates as outlined earlier. 1, The 0° Inclined Test Section

1.1 Procedure 1

The liquid penetration curves obtained by decreasing air flow, i.e. procedure 1, are given in figures D.I to D.3. The curves show that the onset of liquid penetration iB independent of liquid injection rate since all curves tend to meet the horizontal axis at a single value of air injection rate. Deflooding is achieved when the water penetration rate equals the injection rate. The results show that deflooding occurred at lower air injection rate with increasing water injection [figure D.I]. However, for the higher range of liquid injection rate (figures D.2 and D.3] complete deflooding was never achieved even after the air flow was reduced to zero. This was either caused by the displaced air from the lower tank being sufficient to cause some carry-up by percolation through the upper neck and mixer, or due to the occurrence of the cyclic flooding phenomenon (SCF or VCF, as described in Section C). An interesting feature of the results shown in figure D.I is that, within the flooding range, all curves followed a common path as the air injection was reduced. This indicates that, there is a maximum amount of water that would penetrate the test section for a given air flow. At water injection rates above jL* « 0.2 (VjL* > 0.44), the liquid penetration results started to deviate from this common path as the air injection rate was decreased [figures D.2 and D.3). This condition coincided with the onset of cyclic flooding which appears to cause an increase in liquid penetration, as compared to that predicted by the common path. For the highest range of liquid injection rate, shown in figure D.3, this increase in water penetration was more pronounced and showed significant scatter. This is attributed to the occurrence of the violent cyclic flooding (VCF) described earlier.

1.2 Procedure 2

The liquid penetration results obtained by increasing the air flow for a given water injection rate following procedure 2 are given in figures D.4 to D.6. As for procedure 1, the penetration data appear to follow a common curve within the flooding region. In fact, the common curves for both procedures are very close to one another.

For the low range of water injection, shown in figure D.4, it is clear that as the air injection was increased from zero, all of the water penetrated the test section, showing up as the horizontal parts of the penetration curves. These horizontal sections tended to overshoot the common penetration curve as air injection slightly beyond those predicted by the common curve were required to initiate flooding, decreasing the water penetration. Once the onset of flooding was exceeded, the penetration curves adjusted to the common path.

Again for higher liquid injection rates, cyclic flooding was encountered causing larger water penetrations than predicted by the common curve, as shown in figures D.5 and D.6. However, for higher liquid injection rates, the penetration rates continued to be higher than the common curve even when the gas flow was increased enough that the cyclic flooding died out.

1.3 procedure 3 Figure D.7 shows some water penetration curves obtained for tests during procedure 3. The curves in the figure are from tests with low water injections. These curves follow a common curve as did the curves of the low water injection range for the other procedures. This just reinforces the notion that procedure had little effect on the penetration results for the 0° inclined test Bection, - 16 - except near the limits of flooding and zero liquid penetration. 2. The 5° Declined Test Section

2.1 Procedure 1

The liquid penetration curveB obtained from procedure 1 are presented in figures D.8 and D.9. As for the 0° test section, the onset of liquid penetration was independent of water injection rate.

For lower water injection rates, shown in figure D.8, deflooding occurred once the water penetration equalled the water injection rate. However, for higher water injection rates, shown in figure D.9, complete deflooding never occurred because of cyclic flooding or the persistence of agitation caused from the air displaced from the lower tank.

As for the 0° test section, within the flooding range, the penetration curves followed a common path for the lower water injection tests which did not involve cyclic flooding [figure D.8]. Interestingly, this common curve exhibited a distinct peak near jG* = 0.18. This peak coincided with a change in flow regime. Above jG = 0.18 the flow was mainly restricted from the mixer, and as the air injection was decreased, the flow became restricted by pulsations from elbow 2. Another flow regime transition occurred at about jG* = 0.34, however little effect was shown on the penetration curves.

For water injection rates above jL* = 0.26 («'JL* > 0.5), shown in figure D.9, the liquid penetration started to deviate from the common curve with the occurrence of cyclic flooding. As for the 0° test section, the deviation became larger as the cyclic flooding grew in strength. Again it appears that the cyclic flooding allowed more liquid penetration than would otherwise be expected. 2.2 Procedure 3 The liquid penetration results obtained by following procedure 3 are given in figures D.10 and D.ll.

For water injection rates below jL* = 0.26 {^JL* > 0.5) (figure D.10], the air injection had to be increased above zero to initiate flooding. As the air injection was increased, the penetration curves remained horizontal, until the onset of flooding was surpassed. After flooding occurred, the penetration curves for all the tests closely followed a common path. In fact, the common curve during this procedure was practically the same common curve that was observed for low water injections during procedure 1. The peak in the curve was again evident near j0* = 0.18.

An interesting trend apparent from the figure was that for water injections greater than jL* = 0.11 {V'JL* > 0,33) the individual penetration curves overshot the common curve by a substantial amount before flooding was initiated. For water injections above jL* = 0.11, the water flow was restricted by pulse flow from elbow 2 after the onset of flooding was surpassed. The individual penetration curves significantly overshot the common curve in this range because prior to flooding, the flow regime down the test section was one in which smooth liquid-gas interfaces were encountered. Only after a large air flow existed through the test section was the pulsing able to become established and flooding initiated.

The liquid penetration curves obtained from higher water injection rates are located in figure D.ll. The curves show very little difference from those obtained from the high water injection tests during procedure 1. Again the occurrence of cyclic flooding lifted the penetration curves above the common curve, indicating higher water penetration than would be otherwise expected. The magnitude of water penetration during cyclic flooding was very comparable for similar tests during procedure 1.

3. Effect of Test Section Inclination On Liquid Penetration The water penetration curves were previously discussed in sections 1 and 2. In those sections, the curves were compared in terms of the effect of water - 17 - injection rate for each test section. In the present section, however, the water penetration curves will be compared in terms of test section and procedure. Figures D.12 to D.18 show the water penetration curves for Bimilar water injection tests for each test section. Part (a) of the figures correspond to the air first procedure (procedure 1), while part (b) corresponds to a water first procedure (procedure 2 or 3).

As it turned out, the curve for the 0° test section in part (b) was based on procedure 2, while that for the 5° test section was based on procedure 3. Technically, direct comparisons should not be made between these procedures, but aside from small differences in the onset of flooding limit for a few cases, procedures 2 and 3 were found to be practically the same. They were at least similar enough to be generally compared as a water first procedure.

For a given test section, the liquid penetration curves appear to be similar, independent of the test procedure except near the flooding limits. However, interesting differences existed between the curves for the two test sections.

For water penetration below jL* = 0.1 (•! jL* < 0.3), the curve for the 5° declined test section resided substantially to the right of the curve for the original test section. The penetration curves for both test sections had a very similar contour in this range of liquid penetration.

It is interesting to note that for water injection rates of 0.26 < jL* < 0.45 (0.5 < /jL* < 0.67), the penetration curves for the 0° test section appear to converge closer to those of the 5° test section at low air injection. This was due to the formation of cyclic flooding, which was stronger in the 0° test section for this water injection range. Because cyclic flooding was observed to 'lift' the liquid penetration curve, as discussed earlier, the curves for the two test sections converged at low air injections [figure D.17].

However, for water injection rates of jL* > 0.45 (/jL* > 0.67) [figure D.18], the cyclic flooding became very strong in the 5° test section, and accordingly, the span between the curves from the two test sections was reestablished at low air injections.

Also, it is interesting to compare the water penetration at zero air injection, when the VCF was strongest. For the 0° test section, the percentage of water penetration decreased from about 75% to about 50% between the water injection tests for jL* = 0.26 to 0.51 (V'JL* = 0.51 to 0.71). Over the same range of water injections for the 5° test section, however, the percentage of water penetration decreased from over 90% to around 84%.

These results show that the 5° declined test section was not only more effective in allowing water penetration at high air injections, but was also more effective once the violent cyclic flooding phenomenon began. - 18 -

E. THE FLOODING LIMITS

1. The Zero-Liquid Penetration Limit For procedure 1 (air 1st) the zero-liquid penetration limit was defined by the first point that water was able to penetrate the test section to the lower tank, as the air flow was slowly decreased. This limit is alBO referred to as the onset of liquid penetration for this procedure. For procedures 2 and 3 (water 1st), this same limit was defined by the first point where water no longer entered the lower tank, as the air injection was Blowly increased. Figure E.I shows the zero-liquid penetration limits observed for each procedure and test section. It is clear that for all cases, the zero-liquid penetration limit was independent of the liquid injection rate. This result is in agreement with results obtained by other investigators for vertical tubes and bends having diameters less than 10 cm. It is alBO obvious that regardless of procedure, the zero-liquid penetration limit occurred at significantly higher air flowrate for the 5° declined test section. Moreover, the effect of test procedure appeared to be more pronounced for the 0° test Bection, comparing between air first and water first procedures. This is clearly a hysteresis effect. The figure also indicates that no difference in the zero-liquid penetration limit was apparent whether procedure 2 or 3 was applied.

The reoultB for the zero-liquid penetration limit were empirically correlated as follows. For the 0° inclined teat section: V jG* = 0.449 with decreasing gas flow (E.I) and

1 jG =0.65 independent of test procedure (E.3) Figure E.2 shows the zero-liquid penetration results for other works that were done on vertical tubes and elbows. For the 0° test section, the zero-liquid penetration limit was in the same range as that predicted by Siddiqui et al. (1986). Siddiqui's tests were done based only on a water first procedure, and the zero-liquid penetration limit represents the point where water ceased to penetrate through a vertical and horizontal section connected by a 90° elbow. If one considers that the zero-liquid penetra- tion limit is controlled by the flow through the most restrictive element of the test Bection, and that this element is a vertical to horizontal 90° elbow, then the general agreement with Siddiqui et al. (1986) is not surprising. The number or configuration of the elbows in the test section should be irrelevant because each elbow sees the same air flow rate. The same view cannot be taken in regard to the onset of flooding/deflooding, because the flow regime present in the present test section near the flooding/deflooding point are very different from those in a single elbow.

The critical dimensionless gas velocity at the zero-liquid penetration limit for the 5° test section was significantly higher than that for the 0° test section, but was below the curves for vertical tubes. However, this limit for the 5° test section was only slightly below that predicted for vertical tubes by Wallis' criteria jG* = 0.5. The limits measured by Shoukri et al. (1991) for both increasing air and decreasing air procedures for vertical tubes were reached at even higher gas flowrates. Interestingly, however, procedure showed significant hysteresis for these limits, while procedure had much less effect on the limits in both complex geometry test sections. The zero-liquid penetration limit based upon the Kutateladze criterion of Ku = 3.2 for a tube diameter of 3/4" corresponded to much higher dimensionlesB gas - 19 - velocity than for the other vertical tube data. However, it is generally accepted that prediction based on the Kutateladze number iB only valid for tube diameters greater than about 10 cm.

2. The Defloodinq / Onset Of Flooding Limit During procedure 1, the point of deflooding was defined by the firBt point at which all of the injected water succeeded to penetrate the test section to the lower tank, as the air injected was incrementally decreased. During procedures 2 or 3, the onset of flooding was defined as the first point at which water was carried to the upper tank as the air injection was incrementally increased. Figure E.3 shows the onset of flooding limits observed during procedures 1, 2, and 3, for the 0° inclined test section. The axes are based upon air and water injected into the system. A measurable value for the onset of flooding was obtained only for water injection rates below */jL* = 0.41. For higher water injections, flooding occurred with zero air injected to the lower tank. In this range, the displaced air from the lower tank was sufficient to cause flooding. The figure shows that procedure 1 was the most restrictive in terms of the onset of flooding, because the curve lay below those for procedures 2 or 3. This was expected, because during procedure 1, flooding initially occurred, and the air injection was decreased until the point of deflooding. It is logical that the air injection at which flooding Btopped was lower than that required to initiate it. This hysteresis effect was recently reported for flooding in vertical tubes by Shoukri et al. (1991) and Celata et al. (1991).

The onset of flooding also shows no real difference between the results obtained by procedures 2 or 3 except for high liquid injection rates. The reason for this was that for low water injections there always remained a clear air passage through the test section, as the thickness of the water stream in the teat section was low. For high liquid injection rates, the area available for air flow ion was restricted and minor differences in the lower plenum pressure could affect the results. At zero air injection during procedure 2, the displaced air from the lower tank was forced up the test section. This continual flow of air up the test section kept a passageway open through which the air from the lower tank could escape, as the air injected was slowly increased. At zero air injection during procedure 3, however, the air escaped the test section through an open vent before the air was injected, and did not forge a passageway up the test section. Because no air flow existed up the test section, the downcoming water tended to block the test section at the elbows. Once the vent on the lower tank was closed, the air was then forced through the test section, and because of the interrupted air passageway, the onset of flooding occurred at lower air injections.

In the water injection range around /jL* = 0.4, the onset of flooding curves for all procedures had a sudden drop off. For the procedure 1 curve, this sudden drop was caused by the persistence of slugging and agitation above elbow 1, and in the mixer. For water injection tests just below ^jL* = 0.4, the point of deflooding would occur as the air injection was decreased, but there existed a small range below the point of deflooding during which agitation remained above elbow 1. It was not until the air was decreased below this range that all agitation stopped.

This range in which agitation persisted got wider and stronger with slightly higher water injection rates. Just to the left of the sharp drop in the onset of flooding curve, agitation remained above elbow 1 beyond the point of deflooding and continued when the air injected was zero. At marginally higher water injection rates, this agitation and slugging above elbow 1 and in the mixer was Btrong enough that flooding persisted, even when the air injection was decreased to zero. Figure E.4 shows the onset of flooding curveB for both test sections during procedures 1 and 3. The figure shows that the onset of flooding curves for the 5° declined test section lay well above those for the 0° test section, and also extended out over a much higher water injection range. The main reason for this was that because of the declined sections, the water was able to penetrate much - 20 - easier, and did not accumulate to near the depths that it did in the 0° test section. As a result, the slugging above elbows such as 1 or 9 was weaker in comparison, and died out at higher air flows, which led to the higher and broader onset of flooding curves.

It was also shown in the figure that procedure had a much larger effect on the onset of flooding for the 5° declined test section, compared to the 0° teBt section. For the 0° test section, the onset of flooding points for different procedures were quite close together. But for the 5° declined test Bection, a relatively large gap existed between the curves for procedures 1 and 3. The flow patterns in the test section which existed at the onset of flooding were what caused this gap.

For low water injections (below 7jL* = 0.3), the curves were actually quite close together. In this range, at the onset of flooding, the flow was obstructed mainly from the mixer itself. And so it appeared that the hysteresis between initiating and stopping flooding from the mixer was relatively small.

However, for higher water injections, the flow pattern at the onset of flooding was pulse flow from elbow 2. During procedure 1, the water level in section 1-2 was deep prior to deflooding, and the water was driven back in pulses from elbow 2 as the counter-current air flow met the large interfacial waves in the section, until the air flow was reduced enough to allow deflooding. However, during procedure 3, prior to the onset of flooding, the gas-liquid interface in section 1-2 was smooth, and the water level was low. Before flooding could occur, the water layer had to be thickened, or an excess of water had to be amassed in section 1-2. This occurred only after the air flow was increased enough to send a slug from elbow 3 or 5 into this section. This is the reason for the large gap between the curves for procedures 1 and 3.

Figure E.5 shows the onset of flooding curves for other works that were done on vertical tubes and elbows. These works were done using procedures in which the liquid flow was first established and then the gas was increased from zero. Accordingly, the curves d> ring similar procedures (2 and 3) were included from the present work.

For the 0° inclined test section, which included only 90° elbows, the onset of flooding was the most restrictive. For low water injections, onset of flooding was very comparable to the curve proposed by Siddiqui et al. for 90° elbows. However, at increasing water injection rates, the onset of flooding points dropped off much more rapidly than Siddiqui's curve. This can be largely attributable to the pulse flow in section 1-2, which so closely governed flooding in the test section.

The pulse flow in section 1-2 was directly related to the geometry of the test section. The combination of a close proximity between elbow 1 and 2 and the long horizontal section from elbows 2 to 3 worked together to make the pulse flow in section 1-2 very dominant. Because of the length of section 2-3, the water depth in section 1-2 was kept relatively thick. The closeness of elbows 1 and 2 allowed the pulses to be frequent, which further impeded water passage. Based on the present results, one can recommend the following empirical relationships of the onset of flooding/deflooding in the present geometry.

For the 0° inclined test section:

2 2 J'G'' = [0.139-0.827jt*]" independent of procedure (E.4)

For the 5° declined test section:

m 1/2 3/2 j* = -0.455 + 10.21jL* -32.64jt* + 28.05 j^* with decreasing gas flow (E.5) and

1 2 I/2 3/2 J'G ' = 1.675-9.50j£* +25.77jL*-25.52jt* with increasing gas flow. (E.6) - 21 -

The predictions of the above correlations are superimposed on Figure E.4. It should be noted that the simple superposition model suggested be Kawaji et al. (1991b) for predicting the onset of flooding in complex pipe geometries was unable to predict the present data. - 22 -

F. CONCLUSIONS AND RECOMMENDATIONS: Experiments have been performed to investigate two-phase countercurrent flow limitations in complex geometry test sections, using different test procedures. The first test section used was essentially a 1:4 scaled-down model representing the complexity of CANDU feeders. Although geometrical similarity does not ensure hydraulic similarity, the results provide some insight into the effect of complex geometry on two-phase counter-current flow limitations, i.e. onBet of flooding and zero liquid penetration. The effect of declining the horizontal parts of the test section by a small angle of five degrees on the phenomena was investigated with the second test section. Moreover, the effect of test procedure, i.e. water first vs. air firBt flooding, was examined. Based on the present work the following conclusions are made:

(i) For a given water injection rate, the onset of flooding in the 0° test section was encountered at a lower air flow as compared to that for a single elbow, which suggests that the present teBt section is more restrictive than a single vertical elbow with respect to the onset of flooding. (ii) The zero-liquid penetration limit results obtained in the present work are in reasonable agreement with those obtained for a single 90° vertical elbow.

(iii) In all cases tested, the flooding limit curves for the 5° declined test section were well above those for the 0° test section; i.e. declining the horizontal sections relaxed the flooding conditions and accordingly higher gas velocities were required to initiate the onset of flooding and the zero-liqu.i.d penetration limit.

(iv) The effect of procedure (decreasing vs. increasing air) was found to be minimal except at the flooding limits, where some hysteresis was apparent. The hysteresis between the onset of flooding and deflooding was small for the 0° test section, but much larger for the 5° declined test section. On the other hand, for the zero- liquid penetration limit, the hysteresis effects were more pronounced for the 0° inclined test section. In general hysteresis effects appear to be less pronounced for complex geometry as compared to reported results for single vertical tubeB.

(v) It was found that distinct flow regimes existed in the flooding range, i.e. between the two flooding limits. These flow regimes resulted from tht> varying degree of restriction by various parts of the test sections throughout the procedures. These were presented in the form of flow regime maps. However, these maps reflect observations that may be pertinent to the geometry tested only.

(vi) Visual observations suggest that, in terms of flow restriction to water flow within the flooding range, the uppermost vertical-to- horizontal elbow represents a major restriction, particularly for high water injection rates. For low water injection rate, the lowest vertical-to-horizontal elbow plays a major role.

(vii) At high water injection rates, within the flooding limits, a strong cyclic flooding phenomenon (VCF) was observed for air injections below jG* = 0.33 in both test sections. Interestingly, during VCF, the liquid penetration rate was observed to be higher than would occur if the cyclic flooding was not present.

It is recommended that for global calculation of the flooding limits in CANDU feeders, the empirical correlations given in this report be used. It is realized that they are based on adiabatic tests conducted on a test section that had similar complexities to a typical feeder. However, they are believed to be more appropriate, and certainly more conservative, than those available for single vertical bends.

It is also recommended that the present data be used to verify current predictive - 23 - models that are based on calculating local flooding limits in the feeders, e.g. CATHENA code. By using such models to simulate the present experiments, these models should be able to predict the global behaviour observed herein. - 24 -

REFERENCES Ardron, K.H. and Banerjee S., (1986), Flooding in an Elbow Between a Vertical and a Horizontal or Near-Horizontal Pipe, Int. J. Multiphase Flow, Vol. 12, No. 4, pp. 543-558.

Bankoff, S.G. and Lee, S.C., (1986), A Critical Review of Flooding Literature, Multiphase Sci. and Tech., Vol. 2, pp. 95-160, Published by Hemisphere Publ. Corp., Wash., D.C., USA. Celata, G.P., Cumo, M., Farello, G.E. and Setaro, T., (1991), Hysteresis Effect in Flooding, Int. J. Multiphase Flow, Vol. 17, No. 2, pp. 283-289. Kawaji, M., Thomson, L.A. and Krishnan, V.S., (1991a), Countercurrent Flooding in Vertical Pipe to Inclined Pipes, Int. J. Experimental Heat Transfer, Vol. 4, No. 2, pp. 95-110.

Kawaji, M., Lotocki, P.A. and Krishnan, V.S., (1991b), Countercurrent Flooding in Pipes Containing Multiple Elbows and an Orifice, The 1st JSME/ASME Joint International Conference on Nuclear Engineering, Tokyo, Japan, Vol. 1, pp. 115- 120.

Krishnan, V.S., (1987), Two-phase Countercurrent Flow in Upright Pipe Elbows, Proc. Symposium on Transient Multiphase Flow Phenomena, Dubrovnik, Yugoslavia. Mishima, K. and Ishii, M., (1980), Theoretical Prediction of Onset of Horizontal Slug Flow, ASME J. of Fluids Engineering, Vol. 102, pp. 441-445.

Ohnuki, A., (1986), Experimental Study of Counter-Current Two-Phase Flow in Horizontal Tube Connected to Inclined Riser, J. Nuclear Sci. & Tech., Vol. 23, No. 3, pp. 219-232.

Pushkina, O.L., and Sorokin, Y.L., (1969), Breakdown of Liquid Film Motion in Vertical Tubes, Heat Transfer - Soviet Research, Vol. 1, pp. 56-64. Richter, H.J., (1981), Flooding in Tubes and Annuli, Int. J. Multiphase Flow, Vol. 7, No. 6, pp. 647-658. Shoukri, M., (1990), Fuel Channel Refilling-Data Analysis, Atomic Energy Control Board Report INFO-0370. shoukri, M., Abdul-Razzak, A. and Yan, C.Q., (1991), Hysteresis Effects in Countercurrent Gas-Liquid Flow Limitations in a Vertical Tube, Proc. The International Conference on Multiphase Flows, Tsukuba, Japan, pp. 119-122. Siddiqui, H., Ardron, K.H. and Banerjee, S., (1986), Flooding in an Elbow Between a Vertical and a Horizontal or Near-Horizontal Pipe. Part I: Experiments, Int. J. Multiphase Flow, Vol. 12, No. 4, pp. 531-541. Tien, C.L., Chung, K.S. and Liu, C.P., (1979), Flooding in Two-phase Countercurrent Flows, Electric Power Research Institute Report EPRI-NP-1283 72. Wallis, G.B., (1969), One-Dimensional Two-Phase Flow, McGraw Hill, New York. Wallis, G.B. and Dobson, J.E., (1973), The Onset of Slugging in Horizontal Stratified Air-Water Flow, Int. J. Multiphase Flow, Vol. 1, pp. 173-193. Wallis, G.B. and Kuo, J.T., (1976), The Behaviour of Gas-Liquid Interfaces in Vertical Tubes, Int. J. Multiphase Flow, Vol. 2, pp. 521-536. Wan, P.T. and KriBhnan, V.S., (1986), Air-Water Flooding in a 90° Elbow With a Slightly Inclined Lower Leg, CNS 7th Annual Conf., Toronto, Canada. Water Filter

Indicator/Recorder " Drain

Figure S.I Schematic Diagram,of the Test Rig - 26 -

•H g

Q» •P G H

Q)

EH

n

Q)

•H - 27 -

A 'A

5"

separator tank wall 9.8" V

gasket

18.5" A

water injection point 8" outer tube wall

inner tube # with holes

V gasket

test section connects to this counter—sunk face

* inner tube holes are: 1mm diameter 13 columns, staggered horizontally 32 holes per column 4 16 holes in total

Water enters onnulus through 14 radial 1/8" holes

Figure B A Sinter Mixer Construction - 28 -

Tank is 2' cubed Walls are 1/16" steel sheet All pipe taps are 3/8" unless otherwise noted

1/4" thermocouple topping

oir inlet pressure guoge topping

pressure relief valve

test section entronce 7.5"

1/2" drain topping

Figure B.5 Lower Tank Construction - 29 -

Tank walls are 1/16" steel sheet Pipe taps ore 3/8" unless otherwise noted

iir exhoust

3/4" tap fnot used)

carry-over to sinter water mixer droin

horizontal seporotor plate vertical separator plate 1"

t 3/4"

Figure B .6 Separator Tank Construction - 30 -

All dimensions in millimetres measured from tube centeriines Elbow numbers shown in circles

O 830 CM 95 CM r 300 o 00

780 19 In X-Z plan*

O (0

695 35 InX-Zplan»

Figure B .7 A Schematic of the Complex Geometry of the 0° Inclined Test Section - 31 -

All dimensions in millimetres measured from tube centerlines

65

64

87

35° InX-ZpUn»

Figure £.8 Locaiion of Pressure Tappings (PT) On the 0 Inclined Test Section - 32 -

All dimensions in millimetres measured from tube centerlines Elbow numbers shown in circles Dashed sections are declined by 5 degrees

m 830

300 00 ID

m o

695

Figure B .9 A Schematic of the Complex Geometry of the 5° Declined Test Section - 33 -

All dimensions In millimetres

Î43

Figure B.10 Location of Pressure Tappings (PT) On the 5° Declined Test Section Figure c. 1 ***** First Water Entered Test Section Observed Flow Patterns aaaaa Onset of Liquid Penetration 1.0 -i For the 0° Inclined &&&A& Point of Deflooding Test Section ***** Pulse Flow in Section 1-2 - Calm below ++-H-+ Pulse Flow in Section 1-2 - Slugging at elbow 9 Procedure 1 oooo* Section—to—Section Carryover >

I 0.6 - to

CM si » ? n ° ?

*o0.4 H * o + + o o - x x- X" X

0.2 - *' X x

A I 0.0 . ^ / 0.2 0.4 0.6 0.8 1.0 J, 1/2 Figure c .2 Observed Flow Patterns 1.0 -i For the 5° Declined Test Section Procedure 1

0.8 - First Water Entered Test Section oaooa Onset of Liquid Penetration AÛAAA Point of Deflooding • ***• Water restricted at efbow 3 «oooo Section-to-Section Carryover a OOOOO Water restricted from Mixer * Pulse flow in Section 1-2 0.6 - O XXXXX Onset of Violent Cyclic Flooding (VCF) o en o O o xxxxx Small-scale Cyclic Flooding (SCF) .8 o I o o * o O o

0.4 - •et A tr \ •tt it x X •et it / x

it 0.2 - */ ^ 1 X x f I I 0.0 0.2 0.4 0.6 0.8 1.0 •1/2 Figure c .3 Observed Flow Patterns Onset of Flooding 1.0 -i For the 0° Inclined DODDO Complete Carry—up Limit Test Section ***** Pulse Flow in Sectfon 1—2 - Calm below I I I I I Pulse Flow in Section 1—2 - Slugging at elbow 9 Procedure 2 SctcSection—to—Sectiot n Carryoverry r XXXXX Onset of Violent Cyclic Flooding (VCF) Small-scale Cyclic Flooding (SCF) 0.8 -

0.6 - a-

a a D a D CM * * * * * * * * o o / + - -x - --X +- X x 0.2 - X

A I I I 0.0 / _ / 0.2 0.4 0.6 0.8 1.0 • 1/2 Figure c.4 Observed Flow Patterns 1.0 -i For the 5° Declined Test Section Procedure 3

0.8 - Onset of Flooding Complete Carry—up Limit

D D ***** Water restricted at elbow 3 • D s g D •* OOOO* Section —to—Section Carryover * * * * * •* * * * * *__ ^ , OOOOO Water restricted from Mixer * —* — o"' * ***** Pulse flow in Section 1-2 0.6 - " * _ _ *_ o >00< Onset of Violent Cyclic Flooding (VCF) xxxxx Small-scale Cyclic Flooding (SCF) o o o O o o o Q- se o o * o V o o o * o /* o 0.4 . X O s it — X

/• N X

0.2 J \

0.0 0.2 0.4 0.6 0.8 1.0 *1/2 JL - 38 -

Figure c.5 0° Test Section Procedure 1 ViVinj = 0.717 VJGinj = 0-710

Figure c.6 0° Test Section Procedure 1 /inj = 0.717 inj = 0.529 Figure G.7 0° Test Section Procedure 1 VjL*inj = 0.717 V}G',a} = 0.463

Figure C.S 0° Test Section Procedure 1 ' ,j = 0.717 , - 0.431 Figure c.9 5° Inclined Test Section During Procedure 1 VjL^ = 0.360, Vjo*inj = 0.655

Figure C.10 0° Inclined Test Section During Procedure 1 VJL*inj = 0.360, VjG*inj = 0.207 Figurée. 11 0° Inclined Test Section During Procedure 1 Vj * = 0.360, vj ' = 0.207

Figure Q. 12 0° Inclined Test Section During Procedure 1 VJL*inj = 0.360, VjG'inj = 0.207 Figure c•14 0° Test Section Procedure 1 VJL*in- = 0.3 60 Vj *;"J = 0.13 4 JG inj Figure C 13 0° Test Section Procedure 1 VJÛini = 0.360 =" 0-207 0.0 -,-.——-_

w 1.0 - l__ 1 _. ;. .. ; ! ! i PL, : i Lid--=!-- o -::r.:: I ' ! Q . -I ! -I u 2,0- 3 : ..u M ;. . J.'. ._ CO ex, time

O L_L_|_1 T = 2 min. --.- i-

4.0 J 0.611 0.432 0.386 | 0.335 | 0.300 0.285 0.248 Air Injection Rate (j*J/2) Figure c. 15 0° Test Section Pressure Drop Procedure 1 Vj* = 0.246 I i 0.0 -,

i •

w 1.0 Pu I I a, o

QJ 2.0-

u .1.

r—« I.... (d 3,0-

4.0 J I 0.473 10.453 j 0.410 0.335 0.272 I 0.222 | 0.157 0.099 0.000 Air Injection Rate (j*1/z)

Figure C.I6 0° Test Section Pressure Drop Procedure 1 Vinj = 0.406 Figure c 17 0° Inclined Test Section During Procedure 1

'inj = 0-717, VjVinj = 0.321

Figure CJ . 18 0° Inclined Test Section During Procedure 1

VJL*inJ = 0-717, VjG*inj = 0.274 Figure c. 19 0° Inclined Test Section During Proccduu 1 VJL*inj = 0.717, VJGV = 0.321

Figure c.20 0° Inclined Test Section During Procedure 1 4/UÙ = 0-717, ^ = 0.321 -47 -

Figurée-21 0° Inclined Test Section During Procedure 1 *j = 0.717, Vjo*inJ = 0.321

Figure c.22 0° Inclined Test Section During Procedure 1 Vh/inj = 0.717, vjG*inj = 0.321 Figure c .23 0° Inclined Test Section During Procedure 1 VJi/inj = 0.717, VjG% = 0.321

Figure c 24 0° Inclined Test Section During Procedure 1 VJL'in] = 0.717, VJG-inj = 0.274 Figure c.26 0° Test Section Procedure 1 VjL*fnJ = 0.717 v 3GG*in ini j= °

Figure c .25 0° Test Section Procedure 1 *ti\Z = °-321 Figure c-27 0° Inclined Test Section During Procedure I VjJinj = 0.717, VjG*inj = 0.321

•••••••:>•* v7

Figure c .28 0" Inclined Test Section During Procedure 1 VJL;. = 0.717, VjG*inj = 0.321 Figurée -29 0° Inclined Test Section During Procedure 1 Vj * - 0.717, vj * = 0.321

Figure c; .30 0" Inclined Test Section During Procedure 1 ^ = 0.717, Vjo*inj = 0.321 C1 Figure (; 31 O Test Section Procedure

Figure c-32 0° Test Section Procedure 1

jL*ll0 = 0.717 inj = 0.274 o.o -, — ••-

1.0 -

a, o Q

2.0-

ti o

4.0 J 0.294 0.192 | 0.1U 0.000 Air Injection Rate

Figure c.33 0° Test Section Pressure Drop Procedure 1 vj,;inj = 0.717 «•••••

o.o -, ^-•-•--•-

« 1.0 -

a o Q

to u D- r—4 CO 3.0-

4.0 J 0.000 /2 Air Injection Rate (j*G' ) Figure c.34 0° Test Section Pressure Drop Procedure 1

*in j = 0.877 0,0 -,

1.0 -1 a, a, o $_ Q

2.0

V) 5-,

o 3.0-

4.0 J 0.192 0.111 o.ooo Air Injection Rate (j*l/z)

Figure C.35 0° Test Section Pressure Drop Procedure 1 jL% =0.931 M <•>

0.0 -,

1.0 - 3: o Q

2.0- to

i «—4

3.0-

4.0 J

0.192 0.000 Air Injection Rate .(j*l/2) Figure C.36 0° Test Section Pressure Drop Procedure 1 jJinj= 0.511 - 57 -

Figure £.37 5° Inclined Test Section During Procedure 1 VJLV 0.717, Vj* =0.611

Figure c.38 5° Inclined Test Section During Procedure 1 VJL*inj = 0.717, VjG*inj = 0.611 - 58 -

Figurée.39 5° Inclined Test Section During Procedure 1 VJL*inj = 0.717, Vjc*inj = 0.611 Figure C 40 5° Inclined Test Section During Procedure I VJL*inj = 0.360, Vjo*inj = 0.574

Figurée .41 5° Inclined Test Section During Procedure 1 VjJ. • = 0.360, vjG'inj = 0.574 Figure c 42 5° Inclined Test Section During Procedure 1 ' ^Jo'inj = 0.563

Figure c.43 5° Inclined Test Section During Procedure 1 Vj^j-0.717, Vjo*lnj = 0.463 :. 1.1.: 4.0 -,

a a, o Q

2.0 - V) V) s-.

1.0 -

0.0 -1

0.335 0.272 o.ooo Air Injection Rate Q' Figure c.44 5° Test Section Pressure Drop Procedure 1 Vji/inj = 0.647 1*1 '« It '." 1 I. 4.0 -,

3.0 -

O S-,

0) 2.0 - -

1.0 -

0.0 J

0.305 0.248 0.175 o.ooo Air Injection Rate (j"l/?) Figure c.45 5° Test Section Pressure Drop Procedure 1 JL% = 0.706 Figure D 1: Low Water Injection Range 0.20 -i Water Penetration vs. Air Injection For Procedure 1 0° Inclined Test Section

..1/2 JL inj JL inj «oooo 0.0605 0.246 *•**• 0.0875 0.296 ooooo 0.130 0.360 ***** 0.162 0.403 iS 0.10 D

CD c CD

C» (D O * S

0.00 0.00 0.10 0.20 + Air Injection (jG ) Figure n.2: Moderate Water Injection Range Water Penetration vs. Air Injection For Procedure 1 0° Inclined Test Section

0.20 -

JL inj inj «oooo 0.165 0.406 * * * * *0.196 0.443 00000 0.262 0.51 1 c ooooo 0.347 0.806 a» o • —— -4—' oCD 0.10 C (D CL

(D o -t—» o O 0 o

0.00 0.00 0.10 0.20 Air Injection (jG*) Figure D.3: High Water Injection Range Water Penetration vs. Air Injection For Procedure 1 0.40 - 0° Inclined Test Section

. * • «1/2 Jtinj JLinj

.0.30 - o o 00000 0.513 0.716 x ***** 0.603 0.777 44444 0.685 0.828 X X X X X 0.771 0.878 * # • * •* 0.866 0.931 c OOOOO 1.02 1.011 I o 4 o 0.20 - *

0) c CD 0.10 - CD O

0.00 -W- 0.00 0.10 0.20 Air Injection (jG*) Figure n .4: Low Water Injection Range 0.20 -i Water Penetration vs. Air Injection For Procedure 2 0° Inclined Test Section

..1/2 JL inj JL inj ooooo 0.0605 0.246 .#.•* 0.0875 0.296 ooooo 0 130 0 360 ***** 0.162 0.403 •_B 0.10 o >>_ O CD * C CD Q_

CD -t—• O

0.00 0.00 0.10 0.20 + Air Injection (jG ) Figure n.5: Moderate Water Injection Range Water Penetration vs. Air Injection For Procedure 2 0° Inclined Test Section

0.20 -

-1/2 inj inj

«oooo 0.165 0.406 c ***** 0.262 0.511 o ooooo 0.347 0.589 -4—» o "S 0.10 c CD

CD -+—» D

0.00 0.00 0.10 0.20 Air Injection (jG*) Figure ».6: High Water Injection Range Water Penetration vs. Air Injection For Procedure 2 0.40 - 0° Inclined Test Section

o • -1/2 JL inj JL in; .0.30 -• 00000 0.513 0.716 + + + +• + 0.685 0.828 X X X X X 0.77 1 0.878 * * * * * 0.866 0.931 c ooooo 1.02 1.011 o •QO.20 -

C 0 Q_ 0.10 - CD •+-> o o >0 o +

0.00 0.00 0.10 0.20 + Air Injection (jG ) Figure n.7: Low Water Injection 0.20 -i Water Penetration vs. Air Injection For Procedure 3 0° Inclined Test Section

JL in) inj

ooooo 0.1 01 0.318 »**«* 0.150 0.387 c ooooo 0.171 0.414 •_p 0.10 o o 0) c 0) Q_

CD +-*• D o

0.00 0.00 0.10 0.20 Air Injection (jG*) Figure 0.8 Low Water Injection Range Water Penetration vs. Air Injection For Procedure 1 5° Declined Test Section

0.20 - ..1/2 jLinj Jl inj •6A 00000 0.0605 0.246 ***** 0.0892 0.299 0.135 0.367 0.175 0.419 o I o ~CD 0.10 - c

Q_

0) if O o

0.00 0.00 0.10 0.20 + 0.30 0.40 Air Injection (jG*) Figure n.9 High Water Injection Range Water Penetration vs. Air Injection For Procedure 1 5° Declined Test Section 0.40 -

..1/2 jLii JL inj 0.30 - inj ooooo 0.257 0.508 ***** 0.346 0.588 00000 0.418 0.647 c ***** 0.500 0.707 o * o •

•4—> o 0.20 - o „ o CD C

Q_ * o 0.10 - 0 (D D

* o 0.00 0.00 0.10 0.20 + 0.30 0.40 Air njection (jG*) Figure D.10 Low Water Injection Range Water Penetration vs. Air Injection For Procedure 3 5° Declined Test Section

0.20 - if' '"I nj

+ + + + + 0.0605 0.246 ***** 0.0905 0.301 •httttirtt 0. 1 35 0.367 ooooo 0 174 0.417 c ÛAAAÛ 0.258 0.508 o -4—' o "S 0.10 c CD

CD -4—' O

0.00 -ftS- 0.00 0.10 0.20 ^ 0.30 0.40 Air Injection (jG*) Figure D.11 High Water Injection Range Water Penetration vs. Air Injection For Procedure 3 5° Declined Test Section 0.40 -

0.30 - jLinj JL inj 00000 0.334 0.576 c 0.410 0.640 o 0.504 0.710

O **_ 0.20 - CD C CD CL 0 + 0.10 - CD -+—> O

S +. 0.00 -t-fr- 0.00 0.10 0.20 + 0.30 0.40 + Air Injection (jG ) Figure D-12: Water Penetration Vs. Air Injection Comparison Between 0° and 5° Declined Test Sections 1 For Woter Injection Near jL*,nj - 0.0605 (jL"| nf = 0.246) 0.08 -i a) Air 1st Test (Procedure 1)

• •'••0* Inclination (JVWJ=0.0605) ooooo 5 Decline 0^=0.0605) 0.06

c o 0.04 - O 1_ CD C 0) D- 0.02 - i_ CD "o

0.00 0.00 0.10 0.20 ^ 0.30 0.40 Air Injection (jG*)

b) Woter 1st Procedure

0.08 -,

0* Inclinotion (JL'NJ=0.0605) ooooo 5° Decline (^=0.0608) 0.06 J c -£ 0.04 H o c °- 0.02 - S "o

0.00 0.00 0.10 0.20 ^ 0.30 0.40 Air Injection (jG*) - 75 -

Figure D .13: Water Penetration Vs. Air Injection Comparison Between 0° and 5° Declined Test Sections For Water Injection Near j ' = 0.09 (jùpf = 0.30) 0.12-1 t hJ a) Air 1st Test (Procedure 1)

• •••• 0° Inclination (jiVi=0.0875) 0.10 - Q ooooo 5 Decline {jL*m= 0.0892)

^0.08 -

c •S, 0.06 H o

O) 0.04 - CL JjO.02 - "o

0.00 0.00 0.10 0.20 ^ 0.30 0.40 Air Injection (jG")

b) Water 1st Procedure

0.12-1

0.10 - 0° Inclination GVWJ=0.Q875) ooooo 5° Decline (J(J"=00905L"IHJ=O.O9O5)

^0.08 -

c ~ 0.06 H o ^_

•*->

o3 0.02 - o

0.00 0.00 0.10 0.20 ^ 0.30 0.40 Air injection (jG*) - 76 -

Figure D .14: Water Penetration Vs. Air Injection Comparison Between 0° and 5° Declined Test Sections For Woter Injection Near jL*inj =0.13 (jûnj = 0.36) 0.16-1 a) Air 1st Test (Procedure 1)

0° Inclination (jl'JHJ= 0.130) ooooo 5° Decline Gi*nj=0.135) 0.12 -

% 0.08 H a

0.04 -

O

0.00 0.00 0.10 0.20 ^ 0.30 0.40 Air Injection (jG*)

b) Water 1st Procedure

0.16-1

0° Inclination (jV, =O. 130) 0 > MJ 00000 5 Decline (jL"wj=0.135) 0.12 -

$ 0.08 H o

c

0.04 -

-4—» o

0.00 0.00 0.10 0.20 m 0.30 0.40 Air Injection (jG") - 77 -

Figure D.15: Water Penetration Vs. Air Injection Comparison Between 0° and 5° Declined Test Sections For Woter Injection Near jL'iftj = 0.17 (jLYnf = 0.41) 0.20 -i o) Air 1st Test (Procedure 1)

a ....•0° [nclinotion (jt"»u=0.162) 0.16 - ooooo 5° Decline

0.12 - C o 0.08 - eu c eu

0.04 - CD O

0.00 0.00 0.10 0.20 0.30 0.40 Air Injection (jc*)

b) Water 1st Procedure

•"•«0° Inclination (JL"HJ=0.162) 0.16 - 000005 Decline (jL\u=O. 174)

0.12 - C o "o 0.08 - c

0.00 0.00 0.10 0.20 ,,0-30 0.40 Air Injection (jG*; - 78 -

Figure D.I6: Water Penetration Vs. Air Injection Comparison Between 0° and 5° Declined Test Sections For Woter Injection Neor )L'inj = 0.26 (jL'jnf = 0.51) 0.30 -i o) Air 1st Test (Procedure 1)

0° Inclinotion

iO.2O - c O o % CL i_ 0) o

0.00 0.00 0.10 0.20 0.30 0.40 Air Injection (je*)

b) Woter 1st Procedure

0.30 -i

0° Inclinotion (jL'»u=0.262) ooooo 5° Decline QC»u=0.25B)

i0.20 - c O "o •4—> 0) 0.10 - 0) CL

CD o

0.00 0.00 0.10 0.20 m 0.30 0.40 Air injection (jG*) - 79 -

Figure D.17: Water Penetration Vs. Air Injection Comparison Between 0° and 5° Declined Test Sections For Woter Injection Neor jL'ini = 0.34 (jûnj = 0.58) o) Air 1st Test (Procedure 1)

0.30 - ••••• 0° Inclination (JL'WJ=0.347) ooooo 5 Decline GLVJ=0.346)

cO.20 - O o

O

0.00 0.00 0.10 0.20 0.30 0.40 Air Injection (jG*)

b) Water 1st Procedure

0.30 - 0° Inclination .(jV-u, = 0.347) ooooo 5° Decline (jLV=0.334)

c 0.20 - O

CD I 0.10 H a) •+-•o 0.00 -, 1 " r 0.00 0.1r0 0.20 0.30 0.40 Air Injection (jG*) - 80 -

Figure D.18: Water Penetration Vs. Air Injection Comparison Between 0° and 5° Declined Test Sections For Water Injection Near jL'inj = 0.50 (jLVnf = 0.71) o) Air 1st Test (Procedure 1)

0.40 H •••••0° Inclinotion (jL*»u=0.513) ooooc 5 Decline OL"WJ=0.500)

-=i0.30 -

c o °0.20 - -t-> 0) c CD 0.10 -

O

0.00 0.00 0.10 0.20 ^ 0.30 0.40 Air Injection (jG*)

b) Water 1st Procedure

0.40 - 0° inclinotion (jL'i«j=0.5i3) ooooo 5° Decline (JÛNJ=0.504)

r 0 _1 0.30 - > '

- o io n

-»—• 0.20 - 0

•

0.10 - a s r Pent

• "o - •

0.00 - 0.00 0.10 0.20 > 0.30 0.40 Air Injection (jG") Figure E.1: The Zero —Liquid Penetrotion Limit 0.8 -, For 0° and 5° Declined Test Sections

•it È •it a a 0.6 -

* * * x* x *

0.4 - I

CD * + ***0 Inclined Test Sectfon Procedure 1 ***** Procedure 2 X X X X X Procedure 3 0.2 - ODoao 5 Declined Test Section Procedure 1 irùirùir Procedure 3

0.0 0.2 0.4 0.6 0.8 1.0 'L Figure E.2: Comparison of Other Works To The Zero-Liquid Penetration Limit

1.2 4 Based on Ku = 3.2 for 0=3/4

1.0 4 oukri et al. (1991), Vertical Tube (increasing air)

0.8 4 Shoukri et ol. (1991), Vertical Tube (decreasing air) 00 •Wallis (1969), Vertical Tube (increasing air) ro it it 6 fc a a 0.6 -i o x x* xx * * * 0.4 H * * Siddiqui et ol. (1986). 90 deg. elbow (increasing air)

***** o° Test Section Procedure 1 « * * * * Procedure 2 0.2 H xxxxx Procedure 3

DODDQ 5° Test Section Procedure 1 •Cxii-tfto-k I Procedure 3

0.0 T 0.2 0.4 0.6 0.8 1.0 J, 1/2 Figure E.3: Comparison Between Procedures Of the Onset Of Flooding Limit For the 0° Inclined Test Section

* 0.3 - 0° Inclined Test Section AAAAA — Procedure 1 (deflooding) • #•** — Procedure 2 QDODD — Procedure 3

A D CO 0.2 - D C\J *

O

A D *

0.1 - D

I

0.0 - 1 1 1 | i ' ' 1 0.4 0.2 0.31/2 Figure E.4: Onset Of Flooding Limit For 0° and 5° Declined Test Sections 0.6 -i

\ 0.5 - 0° Inclined Test Section — Procedure 1 oaaoa Procedure 3

***** 5° Declined Test Section Procedure 1 xxxxx Procedure 3 0.4 -

i 00 0.3 - o 0.2 -

\ 0.1 - \ \ \

0.0 -€2r- V 0.2 0.3 0.4 0.5 0.6 1/2 JL Figure E.5: 0.8 -i Comparison of Other Works To The Onset Of Flooding Limit Increasing Air Procedure

Siddiqui et al. (1936) Wallis (1969) 0.6 - - — Shoukri et al. (1991)

***** 0° Test Section - Procedure 2 •onao — Procedure 3 x N % •o/ xx xxx 5° Test Section - Procedure 3

0.4 - OO o

0.2 -

a * X a

0.0 p- 0.2 0.4 0.6 0.8 1/2