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Home , Absorption refrigerator, Heat transfer

THE ABSORPTION SYSTEM

tain domestic applications have moving this was accomplished he extinguished parts reduced to a minimum. the flame under the powder and pro- Chapter 13 Fig. 13-2 illustrates a simple ah- ceeded to observe the characteristics sorption system of the liquidabsorbent of the newly discovered substance. A few moments after the flame had been extinguished, Faraday began to THE ABSORPTION note a most unusual occurrence. The , instead of remaining quietly in the sealed test tube, beganto SYSTEM t bubble and then to boil violently. Itwas rapidly changing back into a vapor, and the vapor was being reabsorbed by the powder. Upon touching the end of the The absorption system differsfrom so tube containing the boilingliquid, Fara- the compression system in that it uses th day was astonished to find it intensely instead of mechanical en- duced for the purpose of compariso cold. Ammonia, in changingfromliquid ergy to make a change in the condi- with mechanical types of 13.2. Elementary liquid absorbent cycle. A. Generator: form' extracted heat andit took tions necessary to complete a refrig- The condensing coil, receiver, an 6. condenier: C. ueceiver; D. cooiing coil; E. Burner: this heat from thenearestthingathand, eration cycle. This system uses . c F. -in: G. water-~~t. which was the test tube itself. kerosene, or an ele- u The diagram inFig. 13-3 illustrates ment as a source of heat supply. 13-3. THE ABSORPTION the Faraday experiment.

13-1. TYPES OF ABSORPTION system does not so simply 13-4. ABSORPTION SYSTEM SYSTEMS the illustration portrays, but functio , in 1824, perform- CHEMICALS ed a series of experiments to liquefy There are several usable combina- certain "fixed" -- gases which Several different chemical com- tions of chemicals that have the prop- certain scientists believed could exist binations have heen used in absorption erty that one may absorb the other with- only in vapor form. Among them was units, out any chemical action taking place. ammonia, for it had always been re- Ammonia as the and The 'substance bas the property to ab- garded as a "fixed" gas. Faradayknew sorb the other chemical when cool, but that silver chloride, a white powder, will release the chemical when heated. had the peculiar property of absorbing If the substance is a solid, the process large quantities of ammonia gas. He CHILLING is sometimes called adsorbing while if therefore exposed silver chloride to the substance is a liquid, the process dry ammonia gas. When the powderhad ABIORBER is called absorbing. absorbed all of the gas it would take. There are two principal types of he sealed the ammonia-silver chloride absorption refrigerators: one utilizing compound in a test tube which was bent a solid absorbent material, the other to form an inverted "V." He then ...... : . 'P, using a liquid absorbent. The liquid ab- ted the end of the tube containing :.... 4 sorbent machine is the most popular. powder and at the same time cooled - t - These two types of absorption re- opposite end of the tube with water. -- frigerators are typified by the Fara- day, which is a solid absorbent type 13-1. Elementary solid absorbent cycle. and by the Electrolux, which uses a liquid absorbent. by leaving out the various cont A CONOENSER that are explained in detail later. 13-2. THE ABSORPTION SYSTEM The most appealing feature of araday continued the heating pro- * system is the elimination of m ess until sufficientliquidammoniahad 13-3. Elementary operation of the interrniitent abiorp- tion cycle. Fig. 13-1 illustrates a simple ah-r parts down to a few valves, while een produced for his purpose. When (Faraday Reirigerator Carp.)

316 317 MODERN ,

water as the absorbent is the most paratus is so constructedthat it canob- : popular. tain this ammonia only fromthe . High units (air condi- unit, which necessitates anevaporation iioning) are now using water as the re- taking place there. From elementary frigerant and bromide or lithi- physics one knows that this will cause urn chloride as the absorbent. Thepres- the removal of beat from the cooling sure in these systems varies between 15 unit and its surroundings, and if this psia in the cooling coil to 1 psia in the cooling unit is located in an insulated condenser. box (a box) that box will One company is using methylene be refrigerated' chloride as the refrigerant and di- AS the ammonia methyl ether of tetraethylene the cooling unit it is replaced by liquid as the absorbent. The are ammonia from the receiver. This oper- 3psig and 24 in Hg. . ation continues until the properamount of ammonia is reahsorhed by the gen- erator, when heat is again applied and 13-5. TYPICAL SOLID ABSORBENT ammonia is again moved to the re- SYSTEM ceiver. From the description it is seenth Froan Fig. 13-1 the followingelem- the cycle.is intermittent and that the entary cycle =Y he traced. Heat is ap- completecycle embraces both a gen- plied the generator Or erating period and anabsorbingperiod. FOOD SPACE which will liberate ammonia gas from This cycle may be easily traced from its absorbent and will increase the Fig. 13-2, to the point where the air or This in principle is the Faraday re- water cooled condenser will remove frigerator and its cycle is explained RECTIFIER sufficient heat from the high pressure in detail in Chapter 14, gaseous ammonia to reduce it to a liquid. The liquid refrigerant is forced 13-6. TYPICAL LIQUID from the condenser to the receiver or ABSORBENT SYSTEM storage tank by the pressure of the vipor entering the condenser. The liquid absorbent system seems After sufficient ammonia is driven to possess some very desirable char- into the condenser and receiver, the acteristics. Water at ordinary pres- heat is discontinued and the generator sures and will absorb or absorber cools. When the tempera- great quantities of ammonia. Ammonia lure of the absorber is lowered suffi- absorbed in water may be easily driven ciently, it hegins taking back or re- from the water by the addition of heat. absorbing the ammonia gas. As theah- Also liquid ammonia has a high latent sorber cools it attracts the gas am- heat of vaporization. monia molecules and as they enter the The Serve1 is a domestic ~friger- ahsorber and are changed to a liquid atqr which is designed to operate in a AMMONR HYOROGLN SOLUTION two things happen. First, the absorber continuous cycle and has no moving up and this heat must he removed. parts or valves other than to control I+ C) Second, the pressure in the container the burner flame. The refrigerant is is reduced to the level where theliquid ammonia with water used as the ab-

ammonia can convert again to a gas at sorbent; gas is utilized to 13-4. Diagram of the Servel absorption cycle I, la, lb generator, 2, 2a. Zb, condenser, 3. 3a, 3b. coolingcoil, such a low heat level that refrigerating create a (Dalton's 4 absorber, 5 hydrogen reserve vessel, 6 analper. 7 rectifier, 8 gas . 9 liquid heat exchanger, 10 temperatures are produced. The ap- Law, Paragraph 1-18) to allow th percolator tube, separator, I2 precooler. (Copyright 1955 by Servel lnc.) MODERN REFRIGERATION, AIR CONDITIONING THE ABSORPTION SYSTEM ammonia to evaporate at a low pres- the liquid ammonia flows by gravity The solution, now a strong solution A more detailed study is made of the sure. through the liquid ammonia tube and f ammonia and water, drops tothebot- Servel in Chapter 14. In Fig. 13-4, A represents am- spills into the cooling unit. om of the absorber 14). . and continues monia, and H is hydrogen. As the liquid ammonia falls intothe ,$$,2,$ down through the liquid heat exchanger 13-7. KEROSENE BURNING When the burner is lighted and its cooling unit, (3a and 3h) it forms in I,$),& (9). REFRIGERATORS heat applied through the center of the large shallow pools on a series of generator, ammonia vapor is released horizontal baffle plates. The hydrogen A very convenient refrigerator cy- from the solution. This hot vapor in that is being fed to the cooling unit cle for localities not furnished with part (Ib) passes upward through the permits the liquid ammonia to evap- gas or is the Superfex and percolator tube (lo), and as the hot orate, (Dalton's principle) at a low Trukold cycle. The Superfex cycle is ammonia vapor rises through this tuhe temperature. During this process of basically the Faraday priqciple but it carries the solution to the upper , the ammonia absorbs heat incorporates features which warrant level of the separator (11). from the food compartment of the re- a description. Most of the liquid solution settles frigerator and causes the water in the Ammonia is mixed with water in a in the bottom of (11) and flows through -cube containers to freeze. The tank or generator (A) under which are the liquid heat exchanger (9) into the more hydrogen and less ammonia the located some kerosene burners (M). absorber (4). The hot ammonia vapor lower the temperature. The The burners are lighted and the heat being rises to the top of (1l)tube. vapor formed by the evaporating of the produced drives the ammonia in vapor The hot ammonia vapor then passes liquid ammonia, mixes with the hydro- form out of the mixture. This am- downward through the center tuhe, into gen. This mixture is heavier than hy- monia vapor is forced up a pipe (D) the analyzer (6). Here any water vapor drogen alone and moves downward and through a coil (E) which is im- is removed while the hot ammoniavapor through the middle of the gas head ex- mersed in water contained in a tank rises into the rectifier (7). changer (8) into the absorber (4). This .. 1B) . , on too of the refricerator- (note The rectifier consists of a series circulation is continuous in the cooling L arm\vs Fig. 13-5). 'The lower ttm- of small baffle plates, surrounding the unit. The mixed gases that pass through ~~FP~~uPECJ~~SUS the anmonin vaDor to tube. If the hot ammonia vaporstillhas the gas heat exchanger cool the hy- change back to a liquid at the high some traces of water vapor, it mustbe drogen rising in the outer tuhe. 13-5. The generation or heating inteivai in a typical generating pressure. This liquid am- ;,termittent vpeabsorption refrigeratar. monia drops through a pipe into the removed toinsure pure ammoniavapor. During this time a weak solution of (Perfection Stove Co.. Inc.] The heat has at this point com- ammonia and water is flowing fromthe liquid receiver (C) and from here it pleted its work. For the remainder of generator (11) to the top of the absorber passes to the cooling unit (K) which The liquid heat exchanger carries the cycle, the natural force of gravity (4) by way of the liquid heat exchanger is surrounded by a brine (H). The li- the strong liquid, or refrigerant, back is depended upon to create circulation. (9). Here it meets the mixture of hydro- quid receiver is insulated (F) to pre- to the analyzer (6) and to the generator The pure hot ammonia vapor con- gen and ammoniavapor coming from the vent this container from overcooling it again starts its cycle. tinues into the condenser (2). evaporator by way of the gas heat ex- the food compartment by acting as the The rectifier (7) insures that any The air, passing through the fins changer. The weak solution absorbs the cooling coil. This process continues for vapor still in the ammonia will takes out the heat from the ammonia ammonia vapor. The hydrogen is left a relatively short time until all the condense and drainback to the analyzer. vapor, thus condensing some of the free; since hydrogen is insoluble in kerosene is consumed and the burners The a~~aratusis a welded assemblv. vapor in liquid in (2a). This ammonia w-ater and is very light, it now rises to . . automatically go out. As the absorber There are no moving parts to wear out is now in a pure state, and it flows the top of the absorber and returns to cools to , the am- and go out of adjustment. The totalpres- into the evaporator (3d). the cooling unit by way of the gas heat monia will evaporate at a very low sure throughout the cycle is about 200 The ammonia gas that does not con- exchanger (8). temperature in the cooling unit be- psig, necessitating a rugged construc- dense in (2b) where the rest is con-. The absorber (4) has fins and is air cause as the generator cools it tends tion which insures a long life. densed drains to the upper tube or cooled. The cooling of the weak solution to re-absorb the ammonia gas, there- To produce a 0 F refrigerant in the trap. helps it to absorb the ammonia gas out by reducing the pressure and permit- cooling coil the ammonia must boil at The U-tube is the receiving and of the mixture of ammonia and hydro- ting the liquid ammonia in the eva- 15.7 psig, which means that the hydro- storage compartment inthe cycle where gen. Also when the weak watersolution porator to boil at low temperatures. gen must make up the remainder of the the liquid ammonia is allowed to build absorbs the ammonia gas, considerable This evaporation causes the cooling pressure (184.3 psig). This refrigera- up to a predetermined level; then it heat is liberated and the aircooledfins effect on the contents of the food com- or is considered to be unique among the flows into the cooling coil (3a).Because ml~stremove this heat to permit refrig- partment which is called refrigera- domestic ones sold intbe United States. a liquid will always seek its own level, eration to continue. tion. MODERN REFRIGERATION, AIR CONDITIONING THE ABSORPTION SYSTEM

In detail, the water in the genera- oil burners drives the ammonia from REVIEW QUESTIONS tor (A) cools very quickly after the the generator (A) to the cooling unit burners have gone out, and as cool (K) in a short time; the ammonia in Name the lettered parts of Fig- cold? water bas a strong affinity for am- the cooling unit vaporizes and passes ure 13-2. 9. Why is the storage cylinder or monia, the ammonia vaporized in the hack to the generator slowly wer a Why is the ammonia and water receiver in the Superfex refrig- period of twenty-four to thirty-six comhination so popular? erator insulated? hours. The vaporization of the am- What purpose does the hydrogen 10. Why are these mechanisms pro- monia in the cooling unit produces the serve in the Electrolux? vided with a fuse plug? refrigerating effect. What localities are especially in 11. Name three substances used in For additional efficiency in unusu- need of the kerosene-fired in- absorption refrigerators to ab- ally hot climates or for handling ex- termittent absorption refrigera- sorb the refrigerant gas. tra large loads, a depression (L) in tors? 12. In absorption refrigerators, does the top of the condenser tank may be Who first discovered the absorp- the liquefication of the refriger- filled with water which will evaporate tion principle? ant depend upon compression? rapidly and aid the cooling of the tank. Why must the absorberbe cooled 13. Does the generator serve any This refrigerator is also explained in the Servel cycle? other purpose in the Superfex? in Chapter 14 along with the Trukold What is the purpose of a heat What? and Icy-ball which are fundamentally exchanger? 14. Have absorption refrigerators similar to it. How can burning more gas in using sulphur dioxide ever been Without exception the absorption the Servel cycle produce more used? mechanisms are provided with a fuse plug which will release the charge from the mechanism when the tem- perature of the unit becomes excess- ive 175-200 F. This device prevents any. possibility. of the complete mech- 13.6. The period in an intermittent type ab- anism exploding. ~orptionrefrigerator. An using [Pedectian Stove Co., Inc.] sulphur dioxide as the refrigerant was produced a few years ago but did not cooling unit passes back (note arrows continue on the market. It was of the Fig. 13-6) to the generator through a intermittent type wing silica-gelas the connecting pipe (G)and is re-absorbed absorbent material. The action was by the water in the generator main- very similar to action in the inter- taining a low evaporating pressure in mittent types just explained. This ab- the cooling unit. sorption system is used on some rail- In other words, the heat from the road freight cars. ABSORPTION SYSTEMS, CONSTRUCTION FEATURES

the cabinet behind and above the cool- ing coil. This location is to preventthe Chapter 14 receiver from acting as the cooling coil. The burners are mounted on racks to make shifting of them very simple. ABSORPTION SYSTEMS The water reservoir must be kept filled to the correct depth at all times.

CONSTRUCTION FEATURES 14-5. ICY-BALL A refrigerator, called the Icy-Ball, was made by the Crosley Corp. It was an insulated box with a top door (chest The refrigeration systems of the These units were operated by a absorption type have entirely different which when lighted construction features and service aper- heated the generator- for approximate- ations than the compression cycle sys- ly one hour. After the burner used up tems. In Chapter 13 the absorption its and ceased to burn, the re- cycles are explained in detail. It is the frigerator would provide excellent re- endeavor of this chapter to bring out frigeration for about twenty-three (23) the construction features of these re- hours. Therefore, the housewife only SUB frigerators. needed to fill and light the special AN% kerosene units once each day. 14-1. DOMESTIC ABSORPTION 14-1. The Trukold cycle and burnen. SYSTEMS (Montgomery Ward) 14-3. SUPERFEX Absorption system domestic refrig- -*: erators have been marketed since the The Superfex refrigerator was de- iF be Fpt up to the indicated level, es- 20's. These units have several advan- signed to produce good refrigeration 6 pecially just before lighting. Thekero- tages. They have no moving parts and using kerosene as the source of ener- & sene burners must be clean, dry, and therefore are virtually noiseless. Some gy. The system had the generator on in good condition. They must be filled 14-2. he Icy-Ball refrigerator. do not require electricity and can pro- the left side of the cabinet with the to the correct indicated level and must vide refrigeration where electricity is kerosene burners mounted on racks be in a level position when burning or model), and a portable generator and a not available. and accessible through a small door will result. No ob- cooling unit, Fig. 14-2. It is the ab- I. There are two types of absorption on the lower left side. The condenser be placed over the sorption type and operates as follows: machines; the intermittent type andthe was immersed inatank of water mount- as this will restrict the each refrigerator is provided with a i continuous type. The intermittent type ed on the top of the cabinet. of the cycle. kerosene stove and a water bucket. To however has practically ceased to ex- The system used ammonia as the start operating, place the generator ist. The continuous type is becoming refrigerant and water as the absor- 14-4. TRUKOLD i over the lighted stove and the cooling I increasingly popular. bent. Note that the cooling coil Was unit in the bucket filled with coldwater 1 surrounded by a cold retainer which Another kerosene-fired absorption for about 90 minutes. Then place the 14-2. INTERMITTENT TYPE served to keep the refrigerator cold .-refrigerator was distributed by Mont- cooling unit in the refrigerator box and ~ ABSORPTION SYSTEMS during the heating portion of the cycle. gomery Ward. This refrigerator was the generator out in the open air. Re- 1 intermittent in operation; it used am- frigeration will be obtained fpr about The intermittent absorptionmachine The cycle is explained in Chapter .monia and water as the refrigerant 24 to 36 hours, Fig. 14-3. An inkert was very popular in the 30's. The 13. With this unit there were two pre- and absorbent. A kerosene stove was in the cooling unit is provided with an Crosley Corp. manufactured the Icy- cautions to be observed: The water- located under the box and the heating ice-tray to make ice cubes. The unit Ball, the Superfex was made by the cooled condenser is immersed in a was behind the box, Fig. 14-1. weighs 39 pounds. and is inexpensive Perfection Stove Co. and the Tdold non-flowing water tank located in the Note the location of the liquid am- to operate. It uses ammonia as the re- was sold by Montgomery Ward. top of the box. This water level must monia receiver inside the insulation of frigerant and water as the absorbent. ~ MODERN REFRIGERATION, AIR CONDlTlONlNG

14-6. CONTINUOUS TYPE cooling. The ammonia condenser was ABSORPTION SYSTEMS air cooled and the absorber was cooled by a methyl chloride coil and the hot The continuous type absorption sys- methyl chloride was in turn cooled by tem has been used in the United States an air cooled condenser located just since about 1927. Two systems have beneath the ammonia condenser. been manufactured. The Servel system Starting in 1936, the secondarysys- tem was discontinued and both the am- monia condenser and the absorber are now directly air-cooled. See Big. 14-4.

14-8. THE SERVEL WATER COOLED SYSTEM

The first absorption refrigeratorto become popular on the market was the Servel. In both Chapters 13 and 15 the operation and control of the Servel re- frigerator- are discussed in detail. In Chapter 13 the cycle is discussed, 143. The refrigerating mechanism used in the Icy-Ball Refrigerator. while in Chapter 15 the valves and their adjustments are explained. originated in and the Serv~l Gas is used to supply the heat ener- Inc. organization has the manufactur- gy necessary for operation, and water ing rights. The Faraday unit was made is used as the cooling medium. When during the early 30's. It was not a true connecting the refrigerator to the continuous system but operated the sources of supply of gas and water, generating and freezing portions of the valves both manual and automatic must cycle automatically. be installed. A manually adjustable The continuous absorption system pressure reducing valve, a strainer, is one that can simultaneously con- and a mahual shut-off valve are in- dense and evaporate the refrigerant. stalled in the water line. A pressure reducing valve, amanualshut-offvalve, 14-7. THE SERVEL ABSORPTION a strainer, an automatic temperature SYSTEMS shut-off, a temperature control, and a safety cut-out are installed in the gas As explained in Chapter 13, the Ser- line to handle the gas supply to the vel system operates on the principle burner. of Dalton's Law of partial pressures. The Servel, besides being. offered The Servel has been manufactured in in the domestic cabinet, is also ob- three basic styles. The Original unit tainable in water coolers. used water to cool the condenser and the absorher. In Europe, an electric 14-9. THE AIR COOLED heating- element was used, while in the ELECTROLUX SYSTEM United States all the units were heated Servel, Inc. announced their second- with artificial or natural gas. The ary system air-cooled unit in 1933 and water-cooled units were produced be- continued the model with cabinet re- tween 1927 and 1933. finements in 1935. In 1934 and 1935, a secondarycool- The Servel air-cooledunitischarg- ing system was used in place Of Water ed with a small quantity of aqua-am- ABSORPTION SYSTEMS, CONSTRUCTION FEATURES

monia (distilled water and ammonia) turned by gravlty to the generator. Con- and hydrogen. The charge dlstrihutes tinued refrigeration is merely a repeti- naturally in the umt; the liquid seeks tion of this cycle. the lowest levels and the hydroeen. - and ammonia gas fill the remaining space. Referring to Fig. 14-4, the appli- cation of heat at the generator, am- monia vapor is driven from the strong solution, is raised through the pump tube to the weak liquid separator. Am- monia vapor withtraces of watervapor, is driven off in the separator, leaving the aqua-ammonia solution compara- tively weak inammonia (weak solution). The hot ammonia vapor then passes from the separator to the condenser. When the hot ammonia vapor reaches the condenser it is liquefied by cool- ing. The condenseris finned, and natur- al produces a steady flow of air over it. The liquid ammonia main- tains a level in the condenser, causing the liquid ammonia to flow into the cabinet evaporator. The ammonia evap- orates and absorbs heat inthe evapora- tor. An atmosphere of hydrogen gas, continually sweeping the surface of liquid ammoniainthe evaporator, keeps 145. An air-cooled Senel System whish user a kero- removing the ammonia vapor and sene burner as the heat rource. causes continued evaporation. The am- monia vapor thus formed in the evap- The refrigeration mechanism that orator mixes with hydrogen gas, and contains the ammonia is made ofweld- the mixture is made to flowthroughthe ed steel. The fins on the ammoniacon- evaporator. The long column of heavy densers are made of copper, although

gas, rich in ammonia (ammonia and the tubing is steel. The gas- controls hydrogen mixture) readily overhal- are almost identical with those used in ances the short column of heavy gas in the water-cooled unit (Chaoter. . 15). the evaporator, thereby causingthe de- Several different types have been sired flow in the cooling coil. A flow manufactured. The refrigerators can of weak solution, being returned from he obtained with: the generator, contacts the ammonia 1. Gas heat and hydrogen gas mixture entering the 2. Electric heat absorber, and the ammonia is dis- 3. Kerosene heat, Fig. 14-5. solved. The hydrogen being light re- Another difference in the models is turns to the evaporator. the type of generator. These genera- The heat, which is liberated by ah- tors have been made in both horizontal sorption of ammonia in the absorber and vertical models. is carried away by air cooling. From Fig. 14-6 illustrates a late model the absorber the strong solution is re- Serve1 unit with an across the top - MODERN REFRIGERATION, AIR CONDlTlONlNG ABSORPTION SYSTEMS, CONSTRUCTION FEATURES freezer. The freezer inner door is each ice tray came directly in contact open. A phantom view of a Servel re- with a section of the cooling unit con.. frigerator with a horizontal generator taining liquid refrigerant. is shown in Fig. 14-7. The Faraday refrigerator required The units are now equipped with a water and gas supply and employed automatic defrosters and some of the adjustable valves to cut downandmain- units use an automatic ice cube maker. tain constant pressure in both the sup- ~lvlines. As ewlained before. thp ." . (i) DEFROST HEATER MAIN Faraday cycle was intermittent; there- TERMINAL BOX fore the main gas burner operatedonly CONNECTIONS a portion of the time. This necessitated a constant pilot burner and suitable control devices to open and close the ICE MAKER gas supply to the main burner at the SWITCH BOX proper time. CONNECTIONS

ICE MAKER TERMINAL BOX CONNECTIONS

14-6. A late model Sewel cabinet. Note the acrorr-the- top freezer. Thir cabinet use3 a kerosene burner that is located in the bare of the cabinet. (Sewel in=.)

The electrical system for the more - recent Servel units is shown in Fig. 14-8. The electrical circuits on the Serrel. Thir model hai both aviomatic defrost and automatic ice cube maker. 14-8.

14-10. THE FARADAY SYSTEM monia over to the other portion of the locked in the chamber constructed system, but the method of transferring around the ammonia absorbent. The Faraday AbsorptionRefrigera- the refrigerant was more involvedthan As this vapor heated the heat was tor was built by the Faraday Refrigera- in the original setup. transferred to the absorbent powder, tor Gorp, It was of the solid absorbent 147. A Sewel rhowing the installation of First of all, in order to give a uni- released the ammonia ingaseous form, a harirontal generator unit. which passed up into the water-cooled type. The generator or absorber as- (Servel, Inc.] form heat application to the ammonia sembly was built as a complete unit in the absorber generator, a steam condenser. From here the ammonia which is located either in the bottom bath of a low temperature passed on through the liquid line to of the refrigerator cabinet, installed liquid, called F-11.' was used. the cooling unit, where it was stored. remotely, as installationconditions re- 14-1 1. THE GENERATING PERIOD From the illustration it may be However, because ammonia gas quired. seen that as this vapor became heated, condenses at the coolest point of its The evaporator or cooling unit was As in the original Faraday experi- its pressure rose; as the valve in this circuit, a provision had to be made SO of the plate type, and so arranged that ment, the gas burner forced the am- vapor circuit was closed, thevaporwas the would take place in MODERN REFRIGERATION, AIR CONDITIONING ABSORPTION SYSTEMS, CONSTRUCTION FEATURES the condensing unit rather than in the reabsorb the ammonia driven away omethane) which was the the valve chamber to the condenser cooling unit, which was naturally very from it. This it did as rapidly as it or bath surrounding theabsorber, past the water valve. The water then cold, being inside the refrigeratorbox. could. If it were allowed to reabsorb and water which was used to condense flowed through the condenser cbam- All that was necessary was a pres- the ammonia uncontrolled, a very low both of the above . ber, returning to the opposite end of sure-controlled needle valve in the temperature would be achieved in the The system used about three pounds the water valve. ammonia line which would prevent the refrigerator box. of ammonia and two pounds of F-11. Surrounding this bellows was a ammonia from seeping into the cooling However, this was prevented by the These were, of course, sealed in the liquid which expanded and contracted unit untll its pressure has reached that temperature control unit and storing system. with the temperature of the outlet point where it was condensable at the unit as illustrated. This unit operated The temperature control valve and water. This expansion and contraction temperature of the coolingwater. When as follows: It had a valve bellows and the gas trip valve were also designed of liquid caused the metal bellows to this pressure was reached the valve a spring tension manually adjusted as service valves. The one (tempera- mwe, operating the water valve. Any would open and allow the condensed which allowed the evaporated ammonia ture control valve) was used tosealthe changes of temperature of the dis- ammonia to collect in the cooling unit. gas in the cooling unit to go backto the cooling unit and the pressure tripvalve charged water would change the ad- absorber and be reabsorbed only after sealed the absorber generator unit. justment of the valve; that is, if the 14-12. ABSORBING PERIOD the gases reached a certain pressure Whenever a remote installationwas discharged water became too hot, the corresponding to thefreezingtempera- made, the chief precaution to take was water supply valve would be opened After all of the ammonia had been ture desired in the cooling unit. in connection with theinstallationofthe farther or if it became too cold, the driven into the cooling unit, some When this pressure had beenreach- tubing connecting the above twovalves. valve would be closed more. This tubing had to be dehydrated, that method had to be em~loyed. - to shut off ed, it overcame the spring tension on The gas supply was controlled by a the gas burner. The method used was the bellows; the valve opened and then is, freed from water. It also had to be leather valve and the gas, before it very clean. After hooking up this tubing V-FY. --a qimnle closed again after the pressure had passed through this valve into the When all of the ammonia had been dropped. to the two valves, it had to be sealed burner. was passed through a filter. driven from the absorber there was Because this valve was manually tightly to the temperaturecontrolvalve A further safety feature was in- nothing to remove the heat applied to adjustable, a temperature rangingfrom and only loosely to the gas trip valve. troduced in a safety device operating the absorber and naturally the vapor about 0 F. to 20 F. was obtainable in The temperature controlvalve was then on the thermostatic strip controlling surrounding the absorber became hot the cooling unit. his continued until opened a little and the added tubing the gas operating valve. This device and developed a higher pressure. This the generator had reabsorbed as much purged; that is, cleared of air by the was so arranged that if the absorber pressure operated upon the F-llvapor ammonia as possible after which the ammonia leaking out. Then the connec- assembly reached too high a tempera- valve and when it had become high pressure in the absorber approached tion of the gas trip valve was sealed. ture, either from the failure of water enough forced it open, shutting off the the pressure of the cooling unit. If by chance the gas pilot lightwere supply or any other unusual condition, gas supply and allowing the F-llvapor When this condition was reached it extinguished, by becoming clogged or the device would trip the gas valve to recirculate. was desired that the gas valve be re- smothered, a thermostatic control at- and shut off the gas supply. The opening of this valve naturally opened. This was accomplished by in- tached to a -zas valve in the circuit caused a great drop in the F-11 pres- stalling a pressure bellows valveinthe and the cooling of this thermostatic 14-13. REVIEW QUEST~ONS sure and due to its original spring ammonia line, whichwasattachedtothe valve tripped to shut off the gas sup- pressure it tends to close. This, how- trip arrangement on a combination gas ply. 1. What three substances are used ever, was prevented by a trip arrange- and F-11 valve. The water supply was practically inside a Serve1 mechanism? ment and lock. This was designed so that, aspres- continuous, because part of the time 2. What was the purpose of the It will be noticed from the main sure rose in the line located between it was used to cool the ammonia vapor F-11 in the Faraday? diagram that theabsorberheatingmed- the temperature control valve and the and the remainder of the time to cool 3. Why was a pilot flame used in ium, the F-11, was so circulated that absorber, the bellows contracted and the heat transfer fluid. However, the the Faraday? it came in contact with the condensing tripped the gas valve arm, which was amount of water flowing was so con- 4. Why was copper tubing used in water. When the vapor valve was open- already under spring pressure. It re- trolled by actual requirement that the the Faraday? ed and this heat transfer gas allowed opened simultaneously with the closing minimum amount was used most of the 5. How was the Faraday watervalve to recirculate, the absorber became of the vapor valve which was attached time. manipulated? surrounded immediately with a cold to the same arm. The water valve was mountedonthe 6. What did the water cool during- fluid. This caused a very rapid drop From the above explanation it will side of the absorber assembly at the the freezing portion of the Fara- in the temperature of the ammonia ab- be seen that there were three liquids rear so that connections could be con- day cycle? sorbent in the absorber, which natur- used in the system--ammonia as the veniently made. The inlet water en- 7. What two purposes did the tem- ally put this absorbent in a position to refrigerant. F-11 (trichloromonofluor- tered the opening (A) and passed from perature control valve serve in 332 MODERN REFRIGERATION, AIR CONDITIONING

the Faraday? erator? 8. What is methyl chloride usedfor 12. Why was the liquid receiver in in the secondary-cooled Senrel? the Trukold placed above the Chapter 15 9. What precautions must be taken cooling coil? with the kerosene in the inter- 13. mat was the refrigerant used mittent units? in the Crosley Icy-Ball refrig- SERVICING 10. How the cahinet temperature is erator? adjusted in the Servelrefrigera- tor? 14. What was the purpose of thetank 11. why are two cooling coils used on the top of the Superfex re- ABSORPTION SYSTEMS on the air-cooled Semel refrig- frigerator?

The absorption systems differ only mended that the condensers and the mechanism forproducingrefrig- he cleaned at least twice each year. eration. The cahinet constructionis al- most identical to the mechanical re- 15-2. LOCATION OF frigerator cabinet and the installation REFRIGERATOR d care of these cabinets is explained One should be careful in regards Chapter 9. 1, to locating the absorption refrigera- $ tor, Fig. 15-1. 15 15-1. GENERAL INSTRUCTIONS ,n> 1. It must be away from the or any other source of heat, for econo- The absorption refrigerator is a mical device to move heat from the interior ,g~ 2. It must be conveniently located , of the cabinet to the outside of the indoors for efficient use. !t cabinet. This outside heat is trans- mitted to the air and this air must be removed from the vicinity of the cabi- net to allow cooler air to receive heat from the condensers. Also the kerosene or the piped gas when burned form gas (harmless) and steam vapor (harm- less). However. to provide good air flow past the hurner, these products of combustion must be mwed away from the cabinet. Because warm gases rise, the absorption cabinets must have proper air flow space beneath, inhack, and over the top of the cabinet. Inside the mechanism the liquids flow by gravity and the mechanism must be properly leveled or the move- ment of the liquids and gases inside ,, tho".-- nnit ..,ill he uncertain. "he condensers and flues of the 1. . 15-1. The proper location of an absorption refrigerator t:Umt be kept clean to allowproper to allow good air circulation. #air flow and flue gas flow. It is recom- (Servel,.1nc.j MODERN REFRIGERATION, AIR CONDITIONING SERVICING ABSORPTION SYSTEMS

kerosene burner require very little 3. It must be placed in a room that far away, the flame will notbeeffic~ent twice each year. Special flue brushes servicing. They are manual in opera- has sufficient air movement to provide because of excess air. If the burner is should be used for this purpose. enough air for combustion and cooling. tion and eliminate controls by having too close there will be insufficient air 4. It should be as near as possible the owner refill and light the kerosene for good combustion. 15-8. CABINET CARE to a gas supply if piped gas is to be burner. The previous instructions about air circulation and location of I used. 15-7. FLUES The cabinets are serviced exactly the cabinet also pertain to the kero- 1 5. It must be mounted on a firm like those described in Chapter 8. The sene heated units. floor to maintain its position. The heat from the burners must be cabinet leveling devices are the same, 6. It must be mounted with the unit efficiently transmitted into the genera- 15-5. PROPERTIES OF KEROSENE the door gaskets, and the door hard- level to allow the mechanism liquids tor. The kerosene flame and the hot ware is much the same, the shelf ar- and gases to flow properly. A spirit gases from it are conducted along a rangement and design are the same. The kerosene needed with kerosene level must be used to check for unit flue that extends around the generator Porcelain interiors and enamel ex- fired absorption units should be of the level. It is more important to level teriors are just like the other cabi- highest quality. It must burn as clean- the cooling coil and the burner than it nets. The door gaskets can be checked ly as ~ossibleto eliminate fuel odors is to level the cabinet. for with a light bulb.

15-9. CONTINUOUS SYSTEMS

At the present time there is only one continuous absorption system in the domestic refrigeration field. The Serve1 (or Electrolux as it used to he called). These units receive tbeir ener- gy from piped gas (either artificial or natural), bottled gas, electricity or 15-2. An absorption system kerosene burner. value of about 19,000 Btu. per pound. [Senel, lnc.) kerosene, Fig. 15-3. 15-6. KEROSENE BURNERS The piped gas systems are equip- 15-3. AIR CIRCULATION ped with gas pressure regulators, ther- The kerosene burners used in the mostats for controlling flame size, The air circulation is very import- intermittent absorption refrigerators burners and burner safety shut-offs. ant. Air must be able to freely enter are of standard construction. A circu- There are now 56 different model the burner space and the condenser lar (cylindrical) asbestos wick carries R-4000 series available for replace- space. This same air must be able to the liquid kerosene by wetting action ment purposes for units dating as far back as 1833. No units were made dur- return to the same room. ~fthe air is up to the upper edge of the wick. The 15-3. The refrigerating system for a kerosene burning ing World War II 1943-44, and 45. ducted to another room or air height of the wick is adjustable. This domestic refrigerator. pressure changes mayseriouslybamp- wick should be in good condition, that [Servel lnc) These units contain less than two pounds of ammonia and use the Platen er the operation of the flame. is, it must be charred and then trim- Good air circulation can be easily med to match the guides. The wick must Munters system as devised andpatent- obtained by allowing at least a 2 in. be perfectly level to its adjustable ring or through it. These flues sometimes ed by the two Swedish scientists.Afive clearance in back of the refrigerator and the complete unit must be level, have spiral metal fins inside them to cubic foot refrigerator unit contains (small spaces may be used). At least Figure 15-2. make the hot gases more efficiently abput 1.1 pounds of ammonia. 2.6 pounds of water and 0.03 pounds of hydrogen. 12 in. clearance must beprovidedabove The correct flame, a blue flame give up tbeir heat to the flue walls. the cabinet to allow adequate escape of with faint yellow tips is obtained by Because these flues carry the com- The refrigerators carry twoidenti- the condenser airandcombustionprod- first raising the wick, igniting it, and bustion gases they must be kept open fication plates. One plate is located in ucts. then lowering the wick until the cor- or the combustion will not be complete. the control compartment and this one rect flame is obtained. The flues must also be kept clean or is the cabinet identification plate. The 15-4. INTERMITTENT SYSTEMS The burner must be accurately fitted much of the heat will be lost by poor other plate is located in either the to the generator flue. The distance must heat transmission into tbe generator. frozen food compartment or the con- The intermittent systems that usea he closely adjusted. If the flame is to0 The flue should be cleaned at least trol compartment. The latter has the

336 7' 17 MODERN REFRIGERATION, AIR CONDITIONING SERVICING ABSORPTION SYSTEMS

gas, liquid , or electricity. At heading "Absorption Refrigerating to the burners and must also have a It is seen from the above explana- pressure regulator to insure an un- present gas is the most popular, and Unit." ' tion that a great deal of the successful The units are factory tested to 800 varying pressure on the burner, Fig. the method of controlling the supply operation of domestic refrigerators is psig. which is about four times their 15-4. is explained later. dependent on the functioning of the operating pressure. It is good practice to become ac- Aside from cabinet care and clean- automatic control valves; it is obvious Each unit serial plate bas the Btu quainted withthelocal rules oninstalla- ing, the only service (outside the fac- that the more the service man knows rating of that system recorded on it. tion of -these refrigerators before at- tory) that may be needed on the refrig- of these valves and their troubles and The burner and the necessary con- tempting to install them. erator are heating controls. The ad- remedies, the less difficult the ser- trols are aboutthe only parts that may In all cases of burner difficulty, justments determine the efficiency of vicing operations will be. need adjustment or replacement. If, a check should be made to determine the unit to such a great extent that It is also important to know about however, a unit fails to operate andthe that the burner being used 'is the cor- these must be done carefully. these controls for the reasonthey must trouble is not found to be in the burner rect one for the gas used. Heating gas valves are used in the always heinexcellent conditioninorder or controls then the entire unit should The four different gases in use as a absorption system to enable the auto- to give satisfactory, dependable ser- be replaced. This is easily accom- fuel for the Servel units are: matic control of the amountof the beat- vice. It cannot he emphasized toomuch plished by removing the back from the Artificial gas (425 to 600 Btu Per ing gas. that these valves are the control board cabinet, disconnecting the gas supply cu. ft.) The systems use a continuous gas for the refrigerator. and electrical circuits and removing Natural gas (600 to 1600 Bb per flow. The Serve1 generally has its heat The refrigerators must have a heat- the entire assembly and replacing it cu. ft.) energy su~plied.. bv " a -gas burner.-. Sever-. .. with a new one. Liquid petroleum (LP) gas (1600 ing gas control of some kind. The Ser- a1 different methods have been devised ~tuper cu. ft.) vel being of continuous operation, basa for the regulation and control of this 15-10. GAS SUPPLY gas (1600 Btu Per cu. ft.) gas. In the Servel refrigerator, be- Butane gas (1600 Btu per cu. ft.) tween the gas main and the operation The fuel most commonly used for controls of the rsfrigerator, are placed the absorption system refrigerators is a manual sbut-off valve, a strainer, city or illuminating gas, altboughelec- and a pressure-regulating valve. As trical heating elements are sometimes explained previously, the Servel oper- used. It must be clean fuel in order to ates on the continuous cycle and there- prevent a pollution of the burner or fore gas is continuallybeingconsumed. deposit on the burners. The cleanertbe However, to take care of variations of fuel the less frequently the burners demand on the refrigerator itself, the have to be cleaned. amount of eas fired must be autnmatic-.-. -. The piped gas refrigerators should 15-6. The secondary system air-cooled Serve] they- ally controlled. This is done by theuse mastatic gas control. 6. Maximum flow valve: C. Maxi- of a pressure control valve operated by be supplied with gas under a steady mum flow valve spring arrembly: D. Thermostatic die. phragm: I. By-pars outiei; J. Body garlet dia. a power element located at the cooling phragm: L. Burner lighter parrage; M. Opening to unit. As the cooling unit warms up, the burner lighter: N. Burner lighter valve: 0. Burner lighier valve stem; P. Burner lighter valve stem; Q. Burner gases in the power element expand, and lighter push button; R. Burner lighter cap; 5. Gar aut- pressing upon a diaphragm in the con- lei: T. adivrting rcrew: U. Thermostat adjusting rcrew knob: W. Set screw: X. Diaphragm and trol valve, open the gas control, which allows more gas to escape to the burn- 15-5. The "Kliron" valveand the burner used an the bulb arrembly. alder model Sewel units. A. Gar in; 0. Poppet valve; C. [Servel, lnc.j er, Poppet valve *em: D. ''Klixon" snap button; E. Retaining The largerflame speeds up the cycle houcing; F. Kliron dirk haater; G. Gar parrage to the gas control and a safety con- in the mechanismand continues to speed burner; H. Manual adjvriing screw far maximum gas trol. A disk valve "Klixon," tempera- flame; I. Seat sap; J. Spring: K. Gar noale: L. Screen; it up until the cooling unitbas againbe- M. Screen retainer; N. Screen retainer rcrew: 0. Burner ture-controlled by the flameitself, will come cold enough. 154. The gar line inrtallatbn nf an early model Sewel venturi: P. Burner cap. automatically close the gas supply if refriserator. As the cooling unit cools, tbepower (Servel. Inc] 4 the flame goes out, Figure 15-5.Abulh element located there will cool, reduc- pressure-temperature control located 15-1 1. CONTINUOUS SYSTEM $ ing the pressure on the gas valve dia- at the cooling unit controls the amount pressure and should have a special CONTROLS i phragm. This reductioncloses the heat- of gas burned according to the needs burner for each type of gas. The gas ing gas opening, somewhat reducingthe of the refrigerator, Figure 15-6. ! must be strained before beingadmitted The method of heating may be by size of the flame. This valve operates MODERN REFRIGERATION, AIR CONDITIONING SERVICING ABSORPTION SYSTEMS

The gas now passes throughapres- s~milarto a temperature controlled ex- Each refrigerator has an automatic phragm (synthetic rubber, fabric rein- sure regulator to the thermostatic con- pansion valve. Turning the adjustment pressure control formaintainingacon- forced) and if the pressure attempts trol, then to the burner. clockwise or in, reduces the gas supply. stant gas pressure. This valve reduces to lower the diaphragm will move, After the installation is complete The Servel people have designed a the fluctuation in pressures which al- opening the gas valve allowing more all the joints must be tested for leaks unique valve for preventing useless ways exist in the gas mains all over gas to flow. The increased gas flow with a soap and water solution while waste of gas in case the flame should the country to a minimum. The supply will press the diaphragm up tending under pressure and before lighting the be extinguished. This valve is of the of gas must be very constant when be- to close the valve. The pressure regu- burner. dished-button type and is thermostatic- ing fed to the Servel. lator is very delicate. It is accurate to ally controlled, Figure 15-7. Being 11100 of an inch water pressure. The located adjacent to the flame it re- 15-12. CONNECTING UNIT 1 15-13. PRESSURE REGULATING pressures the regulator has to main- VALVES tain vary from 3.9 inches of water to -sin=---..- hnt --= --..mlnnrr --a- the------.0s- --i9 --irr- nited, but if the flame is extinguished, The gas lines must be installed ac- 1.6. This pressure needed varies with The purpose of the pressure regu- this disk will become cold; it is so de- cording to the local building laws, gas flow in cu-ft per hour. This gas signed that if it does it will snap and plumbing codes and recommendations. lating valve is to supply a steady flow flow is controlled by the orifice size of gas to the burner. If the burner gas hecome dished in the other direction. One should use the best materials in the burner. Thepressure alsovaries This movement closes a valve in the available; all new materials; and the with the density or specific gravity of gas line, completely shutting off the best craftsmanship. the gas. The greater the gas flow the supply of the gas. If this happens, the greater the pressure needed. The only method possible of re-igniting the pressures must be adjusted to within gas is to heat up this "Klixon" disk in .1 inch water pressure for good re- order that it will open the safety valve sults. again. This may be done with a match and a specialburnerpushbuttonmount- ed on the thermostat body provided for this purpose. 15-8. A gas line installation for a Servel gar refrig- erator. This inrtallation varies as to the type generator used.

The gas line should be either 31 8 in. 0. D. copper tubing (soft) or 318 in. 15-9. A pressure regulating valve for gar. A. Shipping 0. D. annealed aluminum tubing. The pin; B. Gar in; C. Gar connedion to the thermortatic tubing should be attached to the main control; D. Flexible diaphragm: E. Weights: F. Valve and seat; G. Bleeder Connection: H. Valve cap. gas line as close to the refrigerator (Serv.1, inc] as possible. The tubing must be pro- tected from ahuse. It should he pro- pressure should change, the flame tected from kinking or bending and it Would change and may even be extin- should be protected from heavy objects to prevent crushing. A hand shut off The pressure regulator both re- should be installed between the main duces the pressure and providesacon- gas line and the tubing. stant gas pressure, Fig. 15-9. At the refrigerator end the tubing Liquid petroleum (LP) gases do not has a hand shut off cock. The tubing need a pressure regulator at the re- is fastened by means of the 45OSAE 15-10. A diagram of the operation of the thermostat frigerator because the pressure re- on the Senel refrigerator. flare to the end fittings, Figure 15-8. lator mounted on the LP cylinder [Servel, Inc.] A strainer is mounted at the outlet erforms the same duty. The Servel company should be con- of the shut-off cock. This strainerisof 157. A safety shut OR valve. This valve will close the The pressure regulator operates sulted in reference to the best gas gn lime if the gar flame should accidentally be ex- very fine mesh and it removes any dust much as an expansion valve does. The pressures for each particular refrig- timluishad. A. Shows the valve in slored parition: B. or dirt that might injure the pressure Showr the valve in open position. outlet pressure presses against a dia- erator. They use different capacity (Seivel, 1nc.j regulator and thermostatic control. MODERN REFRIGERATION, AIR CONDITIONING SERVICING ABSORPTION SYSTEMS orifices to enable them to bring the The inner working of the thermo- and flue. The fitting at the lower right units to maximum efficiency. stat is shown in Figure 15-12. This (at the bottom) is the opening that is illustration shows the construction connected to a manometer to check the 15-14. THERMOSTAT of the minimum and maximum flame gas pressure. adjustments, and also the details of Four different types of burners are The mechanism varies the amount the burner lighter mechanism. available, each for a different kind of of cooling by varying the amount of The amount of primary air is ad- gas. Type A is for fast burning gases beat. The more heat fed to the genera- justable. The outer casing of the burn- and Type D is for liquified petroleum tor the cooler the evaporator will be- er, called the air shutter barrel, can (LP) (bottled) gas. come. A thermostat is used toperform be turned. It should be very carefully The turbulator is available in dif- adjusted to give an all-hlue-flam'e just ferent models; one groove type is for as the yellow disappears from the L P gases, the two groove type is for flame. Too much primary air will also piped gases. give a blue flame hut the flame cone The burner must be exactly the will be sharp and the flames will hiss right distance from the generator flue more sharply.

GAS 7 15-15. BURNER

The burner is the mechanism used to carefully mix the air with gas in the proper proportion and burn the mixture to provide the most efficient heat. It is basically a Bunsen type burner, Figure 15-13. The gas enters at the top, travels past the safety valve and passes through the turbulator, through the carefully sized orifice sperd, mixes with the 15.14. The effed of burner spacing on the minimum flame. 15-13. A sectional view of the horbontal type burner, 15.1 1. The Servel thermostat adjustmentr and (Servel, 1nc.l primary air, burns at the end of the the safety valve and the flame. lighter push button. mixing tube where the secondary air (Servel, 1nc.l (Servel, 1nc.j and the heat enters the generator tube this iob. A thermal bulb clamped tothe to obtain the correct amount of se- IY and then turn it on or if someone cooling coil will create pressure if the condary air, Figure 15-14. accidentally puts out the flame by cooling coil becomes warmer. This The burner can he adjusted to the Spilling mopping water the burner has pressure is carried to a diaphragm distance it is mounted from the gen- a positive safety device that prevents by a capillary tube. An increase of erator flue and it can also be moved unburned gas from escaping. pressure in the diaphragm opens the to center the flame in the center of This safety valve is operated by gas valve and more gas flows to the the generator flue. The flame must the flame. A metal plate touches this burner, Fig. 15-10. never touch the flue. Use a mirmr if flame and becomes quite hot. This The increased cooling resulting / it is difficult to see the flame loca- heat is transmitted to a bi-metal disc, from the added heat will cool the r,snrrnBUlWl tion. which will move with a snap action thermal bulb and the diaphragm pres- The products of combustion are and open the gas valve when hot. If MIHIMI RUIE sure will decrease, closing the valve. AWUITIN~ SCREW harmless and there is no odor. this disc cools somewhat the bi-metal This control was put on 1947 models disc will dish the other way pulling and later. Note the capillary tube, the 15-16. BURNER SAFETY VALVE the valve shut and stopping all gas temperature adjusting knob on the top flow. 15-12. A redional diagrammatic view of the Servel of the body, and the minimum and thermostat. ~h~ gar flowsfrom left to right. Note the It is very unlikely the burner flame It is important that the beat con- maximum devices located on the body, burner lighter button and mechanism. will ever be snuffed out. But if some- ductor strip be kept up against the [Servei, Inc.] Fig. 15-11. one should shut off the gas accidental- outer edge of the flame.

343 4 rl SERVICING ABSORPTION SYSTEMS - - FLUE i flue. This flue is basically the chimney an electrical circuit is closed which - L and it must be kept clean to insure opens a water valve and fills the ice correct air movement. cube freezer trays. When the water is at the correct level, the water flow DILUTION AIR \* 15-18. AUTOMATIC DEFROSTER stops, Figure 15-18. Then when the water is frozen, a thermostat closes -FLUE EXTENSION Several models of the Serve1 con- a heating circuit to lwsen the ice tinuous systemhavedefrostingdevices. cubes, a small electric motor rotates The semi-automatic defroster con- the ice cube apparatus and the cubes sists of Setting the thermostat to a are unloaded into the basket. If the - FLUE ELBOW minimum flame (or defrost position) basket is still not full, the cycle is and when the cooling coilhas defrosted, repeated. the thermostat will automatically start normal operation again, Figure 15-16. 15-20. SERVlClNG THE SERVEL The automatic defroster is con- trolled by an electric timer. At what- It is strongly recommendedthatone ever time the owner prefers usually take training from a Servel service before attempting to service 1 the Serve1 units. The most important observation to CLEAN-OUT be made in servicing the Servel gas- fired refrigerator is to determine that the gas furnished the refrigerator is 15-15, ihe flue son.tructionfor bdh the horizontal and the vertical penerator type Sewel unik [Sewel. Inc.) supplied in the correct amounts and pressure.

15-17. FLUE 15-17. A wiring diagram of the automatic defrosting The flue is a circular passage system. through the generator and then up the [Servel, In..) back of the unit. Its purpose is to pro- vide passage for the flame gases. It in the early morning hours (1 a.m.) -st work efficiently to provide enough the electric clock stops the operation air movement to allow the flame to of the thermostat and sends electrical operate correctly, Figure 15-15. energy through resistance wires locat- The first section of the flue is ed under the cooling coil. The heat within the generator itself. This is the from these wires quickly defrosts the heat transfer surface and the hot gases outer portion of the cooling coil with- must transfer as much heataspossible out disturbing the frozen foods within to the generator. A twisted metal flue the coil. When the coil is defrosted, the system automatically returns to baffle is inserted in this part Of the flue to twist the hot gases to make this normal operation, Figure 15-17. beat transfer efficient. This baffle is removable and mov- 15-19. ICE CUBE MAKER able. It can be uSed to clean out the 15-16. A remi-automatic defrosting thermostat for 15-18. The Sewel avtamatis ice cube maker. Servel units. Some of the Servel units have a (Serve. 1nc.j flue periodically by moving in and out (Serve1 Inc.1 device which automatically manufac- of the generator flue (it is best to turn ~h~ amount of gas fed to the re- tures ice cubes as they are needed. the thermostat to minimum flame dur- flue extension. An air opening is pro- frigerator may be checked by the size A wire basket is used to hold the ing this operation). vided where the two meet, This open- of the flame and may be adjusted by ~h~ second section of the fluersthe ing permits dilution air to enter the e cubes. If this basket is not full, the use of the automatic temperature-

344 345 MODERN REFRIGERATION, AIR CONDlTlONlNG SERVICING ABSORPTION SYSTEMS controlled gas valve which has amanu- preventing a rapid transfer of heat when the cabinet is cold enough a1 adjustment on it. Always check the from the gas flame to the generator insufficient refrigeration in a on the continuous piped gas sys- continuous system? gas pressure using the water filled body. This soot deposit should be re- temz? 10. How are some of the Servelunits manometer. The flue must be kept moved periodically (1-2 months) to in- 9. What are the two basic causes for automatically defrosted? perfectly clean to allow a good trans- sure proper refrigeration and to re- fer of heat. Brushes are used for duce gas consumption. cleaning the flue. When scraping the flue of a genera- The fins on theammoniacondenser, tor or when removing the soot from and, or the absorber must be cleaned any surface of the generator, consider- periodically to insure good heat re- able care should be taken to prevent moval from these surfaces. injury to the surface. Always put papers First, temperature control dial set or a cloth under the refrigerator when too cold which may be the case when cleaning the flues. The gas-fired and the customer has not heen properly kerosene-fired refrigerators are instructed in its use. equipped with flues to direct the hot Secondly, the temperature of the gases around and away from the gen- cooling unit may be lower than that erating units. Occasionally these flues indicated by the temperature control are clogged by placing the refrigerator dial setting. too close to the wall, by placing oh- A time temperature graph should jects over the opening, or by having be taken of such a machine which will some obstruction fall into it. These tell much more clearly what is wrong. flues must be kept clean to insure proper functioning of the refrigerator. 15-23. LITTLE OR NO A Serve1 unit which has not been REFRIGERATION used for a period of time may refuse to freeze when started. To remedythis Little or no refrigeration may be trouble, remove the unit fromthecabi- due to an overloaded cabinet but if this net and invert it for approximately 112 is not the trouble, it may be due to one to 1 hour. Right the unit and install it of the following: little or no refrigera- in the cabinet. tion is due principally to either Im- proper condensing temperatures, or little or no heating of the generating unit. If the condenser or absorber are 15-24. REVIEW QUESTIONS dirt and lint covered, poor refrigera- tion will result, due to the high tem- 1. Why must the absorption unit be perature of these two parts. leveled? If the gas supply has been shut off, 2. How is proper airflowobtained? or if the line has become clogged, re- 3. Is kerosene sometimes used as sulting in a very small consumption of the fuel for continuous systems? gas there is naturally little or no re- 4. What is a flue? frigeration. This trouble maybe traced 5. How is the gas pressure in a by checking the gas pressures at the piped gas system measured? burner. 6. Why don't L P systems need a Two other reasons for poor heat pressure regulator in the base transfer or poor heating of the generat- of the cabinet? ing unit are: a restricted gas flue, or 7. How is the temperature regulat- an insulated gas flue. After a certain ed in a piped gas continnous sys- period of use the flue of the generator tem? may become coated with a soot deposit, 8. Why doesn't the flame go Out