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Proceedings of the World Congress on 2014 Vol II, WCE 2014, July 2 - 4, 2014, London, U.K.

Fabrication of Pilot Multi-Tube Fire-Tube Designed For Teaching and Learning Purposes in Mechanical Laboratory

Gbasouzor Austine Ikechukwu, Member IAENG

Abstract - The aim of this research is to design and The first reaction-type was built by Hero of fabricate pilot multi-tube boiler using a diesel fired Alexandria in the 1st century AD. In his , was burner (C13H25)9 to generate 80kg of steam per hour. The fed into a sphere that rotated as steam expanded through two boiler tank is made of pure mild steel. Mild steel is used tangentially mounted nozzles. No useful was produced to fabricate the fire tubes and other parts such as the by the aeolipile. Not until the 19th century were attempts , smokestack and return chamber that make up made to utilize steam for practical purposes. In 1837 the boiler. The heating surface area was increased for a rotating steam chamber with exhaust nozzles was built to sake of efficiency and fast steam generation by reversing drive gins and circular saws. A single-stage impulse the direction of the gas through a second and third turbine was designed by the Swedish engineer Carl Gustaf de parallel tube (three pass). The boiler (which is fired by a Laval in 1882. A later American design had multiple impulse diesel burner) generates dry saturated steam at a wheels mounted on the same shaft with nozzle sections of 1. Stars and of 111.40C. It can be located between each wheel. Subsequent advances in the used for domestic and industrial purposes. design of steam turbines and allowed for higher and . These advances led to the huge Keywords: Diesel fired burner, pure mild steel, sake of and efficient modern , which are capable of efficiency Domestic and Industrial purposes. converting more than 40 percent of the energy available in the into useful work. I. INTRODUCTION The word 'boiler', in everyday use, covers a wide range of Watt is credited as being the first inventor to separate the equipment, from simple domestic hot water boilers to boilers steam , and the boiler, into two separate units in the housed within a power generation plant to convert latter part of the . In these early times, the to electricity. Generally, domestic hot water boilers do not primary use of the boiler was to generate steam for steam produce steam and should operate at low pressure. While driven . some combination boilers now operate at the pressure of the incoming cold water mains, this is still far below the normal As steam driven engines replaced the horse, as a means operating pressure of steam-raising boilers. of motive power, it followed that steam driven engines were The basic operation of steam turbines employs two rated in ''. concepts, which may be used either separately or together. In Boiler design progressed from what was essentially a kettle an impulse turbine the steam is expanded through nozzles so to a relatively large-diameter flue pipe submerged in water - that it reaches a high velocity. The high-velocity, low- thus the first fire-tube boiler, pressure jet of steam is then directed against the blades of a As power and pressure requirements increased, boilers spinning wheel, where the steam's kinetic energy is extracted became larger and the single-flue pipe became a larger while performing work. Only low-velocity, low-pressure number of smaller diameter flue tubes combined with an steam leaves the turbine. external, or internal, furnace for the combustion of the fuel. In a reaction turbine the steam expands through a series The modern-day 'modified Scotch Marine' boiler, generally of stages, each of which has a ring of curved stationary comprising horizontal steel furnace combustion chambers) blades and a ring of curved rotating blades. In the rotating and/or fire-tube convective pass(es), in 'dry-back' or 'water- section the steam expands partially while providing a reactive back' configurations, owes its heritage to these early multi- force in the tangential direction to turn the turbine wheel. The tube boilers and their application in constructed on stationary sections can allow for some expansion (and 's River Clyde. increase in kinetic energy) but are used mainly to redirect the The primary application of the boiler was still motive steam for entry into the next rotating set of blades. power; whether for pumping water from mines, driving In most modern large steam turbines, the high-pressure machinery in mills, propelling steam or ships. steam is first expanded through a series of impulse stages sets Therefore, boiler ratings were based on the size of the steam of nozzles that immediately lower the high initial pressure so engine that they were capable of driving. The quantity of that the turbine casing does not have to withstand the high steam required to operate a 1 horsepower pressures produced in the boiler. This is then followed by became known as 1 Boiler Horsepower. (Note that the water- many subsequent impulse or reaction stages (20 or more), in tube boiler was not prevalent until after the first water-tube each of which the steam continues to expand. boiler design of 1867; thus, the term Boiler Horsepower (Bhp) has been associated with fire-tube boilers Gbasouzor Austine Ikechukwu is a PhD researcher and Lecturer in the from the earliest days of boiler development). Department of , Anambra State University, P.M. B. During this period, variations in steam 02 Uli. Nigeria, Email: [email protected] Phone: made it difficult to assign a qualified rating (i.e. Pounds per +2348034247458. Hour (PPH)) to the amount of steam required to drive a 1

ISBN: 978-988-19253-5-0 WCE 2014 ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online) Proceedings of the World Congress on Engineering 2014 Vol II, WCE 2014, July 2 - 4, 2014, London, U.K.

horsepower steam engine. Tests, conducted in 1876,  Compliance with the ASME Boiler and determined approximately 30 pounds of steam per hour was Code. required to produce 1 horsepower of mechanical work. In  Compliance with required safety and installation Codes. 1889, the American Society of Mechanical Engineers  The ability to meet the required efficiency and other (ASME) standardized the term "Boiler Horsepower" as being performance standards. based on a conventional steam engine evaporation rate of 30  The ability to meet the required level of pollutant pounds of steam per hour (PPH), at 70 PSIG pressure, and a emissions, feed water temperature of 100° F. This definition was  Compliance with the requirements of the National Board subsequently modified to: Boiler Horsepower - the unit of of Boiler and Pressure Vessel Inspectors through local capacity expressed as the equivalent evaporation of 34.5 jurisdictions having authority (JHA), pounds of water per hour, from and at 212° F (33,475  The ability to meet the perceived needs of the customer Btu/hr.). in terms of operational performance, reliability and maintenance costs. Also, it was determined that for the steel fire-tube boilers of  The ability to produce a competitively priced product the day, which utilized brick set bases incorporating large

amounts of refractory, and generally fired, 10 square Fire-tube boiler manufacturers have established over the feet of fireside heating surface was necessary for a steam years that these criteria can be satisfied with varying fire-side engine to generate I mechanical horsepower. As a result it heating surface specifications. Thus, the nominal 5 square became an industry standard practice to rale lire-tube boilers feet of fire-side heating surface per boiler horsepower axiom in Boiler Horsepower, and to base this rating on fire-side is less important as a critical design consideration. heating surface (1 Bhp per 10 square feet of fire-side heating

surface). B. High-pressure Competition between fire-tube boiler manufacturers While the advances of 18th century, the call was for higher eventually forced improvements in boiler design and fuel pressures; this was strongly resisted by Watt who used the burning equipment. This, together with a broad shift towards monopoly his patent gave him to prevent others from liquid and gaseous fuel utilization, resulted in cleaner and building high-pressure engines and using them in vehicles. more reliable combustion and improved within He mistrusted the materials' resistance and the boiler the boiler. Progressive reduction in the fire-side heating of the day. surface required, per Boiler Horsepower, was therefore The important advantages of high pressure were: consistent with these advancements. By the I960's, the 10 1) They could be made much smaller than previously for a square feet of fire-side heating surface per Boiler given power output. There was thus the potential for Horsepower criterion decreased to 5 square feel of fireside steam engines to be developed that were small and heating surface per Boiler Horsepower - an axiom which is powerful enough to propel themselves and other objects. commonly cited today, particularly in the United States. As a result, steam power for transportation now became During the latter part of the 20 Century, many a practicality in the form of ships and land vehicles, manufacturers of fire-tube boilers designed which revolutionised cargo businesses, travel, military and marketed boilers with greater input capacity burners with strategy, and essentially every aspect of society. requisite steam nozzle and safety (s) characteristics 2) Because of their smaller size, they were much less which therefore permitted operation at less than 5 square feet expensive. of fire-side heating surface per boiler horsepower with 3) They did not require the significant quantities of acceptable reliability and efficiency; condenser cooling water needed by atmospheric engines. It was during this same period that certain jurisdictional 4) They could be designed to run at higher speeds, making mandates were promulgated that required licensed boiler them more suitable for powering machinery. operators for boilers in excess of a certain defined fire-side The Disadvantages were: heating surface criterion. These limitations generally 1) In the low pressure range they were less efficient than afforded opportunity to employ less than 5 square feet of fire- condensing engines, especially if steam was not used side heating surface per Bhp. This furthered development of expansively. fire-tube boiler designs specifically for particular 2) They were more susceptible to boiler explosions. jurisdictional requirements, again with acceptable reliability The main difference between how high-pressure and low- and efficiency. pressure steam engines work is the source of the force that Manufacturers of other boiler types, such as vertical, moves the . In Newcomen's and Watt's engines, it is the water-tube and cast sectional boilers, have used the Bhp of the steam that creates most of the pressure output rating as a means of comparison with fire-tube boilers. difference, causing (Newcomen) or They have not, typically, related Bhp output to a certain low-pressure steam. (Watt) to push the piston; the internal square feet of fire-side heating surface criterion, opting • pressures never greatly exceed atmospheric pressure. In a generally to rate by net output generated by the boiler; steam high-pressure engine, most of the pressure difference is boilers expressed in measurements of PPM, 34.5 pounds per provided by the high pressure steam from the boiler; the low Boiler Horsepower from and at 212° F, or millions of Btu/Hr pressure side of the piston may be at atmospheric pressure or, (MBH), and hot water boilers expressed in measurements of if it is connected to a condenser, this only provides a small 33,475 Btu/hr per Boiler Horsepower, or millions of Btu/Hr proportion of the pressure difference. (MBH). C. Considerations for the Future A. Basic Design Requirements Criteria which govern the It is apparent that the powerful analytical tools available design and manufacture of fire-tube boilers include: today will continue to be applied to improve fire-tube boiler ISBN: 978-988-19253-5-0 WCE 2014 ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online) Proceedings of the World Congress on Engineering 2014 Vol II, WCE 2014, July 2 - 4, 2014, London, U.K.

design, as well as that of the fuel burning equipment. This firing, heat source or circulation (for example, oil-fired, will inevitably result in smaller, higher efficiency fire-tube gas-fired, coal-fired, or -fired). boilers with lower pollutant emissions. • According to their method of fabrication. Combustion technology, with specific regard to NOx • And boiler can be pack aged or field erected. reduction, is rapidly approaching the point of diminishing returns. Should further emission reductions develop, one A. TYPES OF BOILERS method of achieving compliance will be a significant Fire Tube Boilers: increase in boiler efficiency, and thus reducing fuel input Fire tube boiler consists of boiler shell which is filled with consumption. Combined with an obvious general tendency water and perforated with tubes, there are different by end users, architects and engineers, to minimize the boiler configurations of these tubes but horizontal configuration is the room footprint in building construction, the resultant more common one. Water is partially filled in the water tank and compact and higher efficiency boilers, requiring lower volume is left inside the tank to accommodate the steam. Long heating surface per Boiler Horsepower, will be furthered. horizontal tubes arc called flues and these carry the hot Albeit, the resulting improvements will remain predicated combustion gases through the water tank and heating the upon the particular fire-tube boiler system application water. The furnace is situated at one end of a fire tube requirements, materials and manufacturing limitations. which elongates the path of the hot gases, thus expanding Manufacturers of fire-tube boilers, recognizing the the heating surface which can be further increased by benefit of enhanced design and materials technology, making the gases reverse direction through a second tube or currently apply these resources to advance product design, bundle of multiple tubes. performance and manufacturing competitiveness. The water and steam in fire-tube boilers contained within a Individually, and together with the US Department of large diameter drum or shell, and such unit arc often referred Energy, programs have been initiated to further development to as 'shell type boiler'. Heat from the products of of these, and other , to meet with the ever combustion is transferred to the by tubes and it increasing expectation of fire-tube boiler capabilities. goes out from the smokestack. Fire-tube boilers are approximated to 360psi of steam pressure. In case of fire- D. Scope of Research tube boiler the whole lank is under pressure so if tanks burst The research work provides guidance on how to design a it creates a major explosion and if one need to increase the simple model fire-lube boiler for domestic and industrial use. steam pressure of fire-tube boiler then it is necessary lo This design guideline can assist upcoming engineers to increase the thickness of the shell and material of tube sheet. understand the basic design of boiler and a suitable size, The water is confined by the outer shell of boiler. To material and heat of combustion, The choice of fire-tube avoid the need for a thick outer shell fire-tube boilers are used boiler and its design is crucial to give the best performance of for lower pressure applications. Generally, he heat input boiler; good performance of boiler is influenced by capacities for fire-tube boilers are to 50mbtu per hour or less, maximum heat absorbed and minimum heat loss. The design but in recent years the size of fire-tube boilers has increased. of boiler may be influenced by factors including process Fire-tube boilers are subdivided into three groups; requirements, economics, and safety. All the important horizontal return tubular (HRT) boilers typically have parameters used in the guideline are explained in the horizontal self-contained fire-tubes with a separate definition section which helps the reader to understand the . Scotch, scotch marine, or shell boilers meaning of the parameters or term used have the fire-tubes and combustion chamber housed within the same shell. boilers have a water-jacketed firebox II. THE ORGAN OF BOILER and employ at most three passes of combustion gases. A boiler is a closed vessel in which steam is produced from Most modern fire-tube boilers have cylindrical outer water by combustion of fuel. Steam boilers is made up of two shells with a small round combustion chamber located inside major parts, that is, the combustion chamber, which provides the bottom of the shell. Depending on the constructions heat by the combustion of fuel, and the which details, these boilers have tubes configured in one, two, three transforms water into steam through heat exchange in the or four pass arrangements, because the design of fire-tube medium (Saidur et al., 2010). boilers is simple, they are easy to construct in a shop and can be shipped fully assembled as a package unit. Fire-tube boilers typically have a lower initial cost, are more fuel efficient and are easier to operate.

Advantages of Fire-Tube Boilers; i. Low cost. ii. Fluctuations of steam demand can be met easily. iii. It is compact in size.

B. Water-Tube Boilers; Fig 1: A schematic diagram of a steam boiler. In water-tube boilers the rack of tubes are positioned vertically in the firebox and through these tubes water flows Boiler systems are classified in variety of ways. They can be which gets heated upon flowing 'through these tubes, these classified; vertical pipes are called riser and these extends from the • According to the end use, such as foe heating, power water drum which is at the bottom of the boiler to the stem generation or process requirements. headers which are at the top of the boilers. These typically • According to pressure, materials of construction, surround the firebox in many layers like a dense forest. As size tube contents (for example waterside or fireside), ISBN: 978-988-19253-5-0 WCE 2014 ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online) Proceedings of the World Congress on Engineering 2014 Vol II, WCE 2014, July 2 - 4, 2014, London, U.K.

steam bubbles form, they rise to the where the rib on an object for fixing it to another object, holding it in place steam exist through the header. or strengthening it. Flanges are often found on pipes and shafts) of both the burner and furnace respectively. The Water-tube in furnace can be arranged in many different flange specifications are given as follows; configurations and they are often used to connect water • Outer diameter of circular flange drums at the bottom and water, and steam drum at the top, (d0) = Ø0.017 x 2m there exist a mono-tube boiler used to circulate water • Inner diameter of circular flange through a succession of coils, this type of boiler has very (dj) = Ø0.013 x 2m fast production of steam but has very less storage • Number of opening for bolts and nuts of flange = 4 capacity. Water-tube boilers are preferred for high openings pressure application because of the high pressure • Diameter of the bolts and nuts used (db) = Ø00.014m

steam/water is contained in smaller diameter pipes which The furnace which is located inside the boiler pressure vessel withstand the high pressure. (shell) and situated at one end of 5 section of longitudinal Water tube boilers require less weight of metal for a given fire-tubes connected to it serially which elongates the path of size, are less liable to explosion, produce higher pressure, the hot gases, thus expanding the heating surface. The idea of are accessible and can respond quickly to change in steam placing the furnace inside the boiler shell is to maximize the demand. Tubes and drums of water-tube boilers are heat of the boiler rather than losing it to the surrounding. The smaller than that of fire-tube boilers and due to smaller furnace serves as a pre-heater in this case as it raises the size of drum, higher pressure can be used easily in water- temperature of the water. tube. The fire-tubes extend to a compartment known as the return Advantages of Water-Tube Boilers. chamber situated at another end in the boiler vessel (shell). i. High pressure of the order of 140kg/cm2 can be obtained. The return chamber itself which is serving as an intermediary ii. Heating surface is large; therefore steam can be for hot gases transfer has another set of 5 fire-tubes generated easily, connected to it in the same manner as that at the furnace. iii. Large heating surface can be obtained by use of large This was done to further increase the heating surface area by number of tubes, making the gases reverse direction through a second 5 sets of iv. iv. As a reason of high movement of water in the tubes parallel tubes. The heat emitted by this other set of 5 the rate of heat transfer becomes large resulting into a longitudinal fire-tubes at the return chamber goes out from a greater efficiency. smoke stack. The following are the specifications of the inner components in the boiler vessel (shell): III. DESIGN PROCEDURE OF THE BOILER i. Total of 15 pieces of fire-tubes In the design of multitude fire boiler in this report, many things ii. A furnace were considered when analyzing the system: iii. Two return chamber • Design specification iv. Smoke stack. • Design consideration • Detailed design B. Design Consideration for Material Selection. • Technological details. For an intelligent design to be done, the knowledge of the materials available as well as the properties they posses are A. Design Specification very important For the selection of the proper material to be The fire tube boiler consists of various components and it will used for the design of the fire-tube boiler, we shall consider be great importance to have a detailed specification before the the factors which affect the choice of material selected and design. The arrangement of the fire-tube boiler is illustrated used for design and there reasons.

below. Factors considered are: 1. Suitability of the material for the working conditions in service, considering characteristics such as; appearance, thermal conductivity, rate of emissivity, strength, stiffness, creep, etc. 2. Availability of the material: the ease at which the materials are seen or purchased in the market. 3. Workability of the material: considering possible methods of processing material selected into desired shape such as; weldability, machinability, formability, and workability. 4. Expected load or force as well as adequate strength in conformity so as to function satisfactorily without Fig 2: Dimensioned diagrams of the three pass fire-tube boiler failure. 5. Cost of the material (economic consideration). The diesel burner used to heat up the furnace of the fire-tube has the following specifications: Choice of Material • Mass firing rate = 2.5 - 5kg/hr Based on the above considerations, the materials used for the • Orifice diameter for exit (d) = Ø0.0005m design of the fire-tube boiler were thus selected and tabulated • Motor rating = 0.5 horse power. below; The burner is connected to the furnace by the means of both external and internal circular flange (a projecting collar, rim, or ISBN: 978-988-19253-5-0 WCE 2014 ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online) Proceedings of the World Congress on Engineering 2014 Vol II, WCE 2014, July 2 - 4, 2014, London, U.K.

2 2 3  rLr (1) 3 TABLE 1: MATERIALS USED AND REASONS To know the maximum pressure and temperature of the Parts Material formally Material used and reasons boiler, using the hoop law; used or preferred and We know that, reasons Furnace Aluminum; good Mild steel; affordable, available, Tensile stress of a mild steel = 60Mpa Ultimate tensile stress conductivity, high weldable, malleable, strength, of a mild steel = 410Mpa corrosion resistance but high conductivity, and corrosion Hoop stress of mild steel = 140Mpa Pressure of steam at high melting point. resistance. 111.40C (p) = 1.5bar = 0.15Mpa Fire-tubes Copper; high thermal Mild steel; affordable, available, conductivity, better weldable, malleable, strength, Thickness of pressure vessel (t) = 6mm Diameter of vessel formability. high conductivity, and corrosion (d) = 620mm resistance. The hoop of stress of the steam Return Aluminum; good Mild steel; affordable, available,  dp chamber conductivity, high weldable, malleable, strength, h  (2) corrosion resistance but high conductivity, and corrosion 2t high melting point. resistance. The estimated maximum pressure of the vessel Pressure Wrought iron; Steel; low cost of fabrication,  2t P  max (3) vessel toughness, malleable, stronger, quick weldability, max 620 and ductile. cheaper and less labor. E. Design of The Furnace Smoke sack Copper; high thermal Mild steel; affordable, available, conductivity, better weldable, malleable, strength, The furnace made of mild steel located at one end of the formability high conductivity, and corrosion boiler connected to a heat supply (diesel burner located resistance. outside the boiler vessel) in this case by means of a flange with specifications stated above, serves as the central system C. Detailed Design for heat (hot gases) distribution to the fire tubes. The furnace Having completed the material selection for the fire-tube has a length of 0.40m, thickness 10mm and a diameter of boiler, the design of the various parts of the boiler is typified by 0.170m. Other dimensions are given below; the following features; Volume of the furnace 2 • The volumetric boiler pressure vessel (tank or shell). d 2  L .0 17  .0 40 (4) • The furnace. 4 4 • The lire-tube. • The return chamber. F. Design of The Fire-Tubes • The smoke stack. The fire-tubes made of mild steel is a total 15 in numbers and • Actual volumetric capacity of the boiler. is sub-divided into three sections namely • Pressure gauge.  Furnace section = 5 fire-tubes of length 0.30m and • Temperature gauge. diameter 0.030m each. • .  Return chamber section = 5 fire-tubes of length 0.30m • Thermal stresses and creep analysis. and diameter 0.030m each.  The third pass section (section to the smokestack) - 5 fire-tubes of length 0.50m and diameter 0.030m each. Other dimensions are as shown; Volume of the fire-tubes in the furnace section

d 2 .0 03 2  L   3.0 (5) 4 4 Volume multiplied by the number of fire-tubes on this section Volume of fire-tubes in the return chamber section Fig 3: Schemetic diagrams of the three pass fire-tube d 2  .0 032  L   3.0 (6) boiler 4 4 Volume multiplied by the number of fire-tubes on this D. Design of The Volumetric Boiler Pressure Vessel. section The boiler volumetric tank measures the quantity of water Volume of fire-tubes in the third passes section delivered to it at a given time. It has a capacity of 292 liters d 2 .0 03 2 and it is made of steel metal of 0.006m thickness for pressure  L   5.0 (7) 4 4 resistance, Ø0.62m and length of 0.76m three holes were Volume multiplied by the number of fire-tubes on this bored on the surface of the tank for both steam outlet section (Ø0.50m), turbine outlet (Ø0.50m) and exhaust or

smokestack outlet (Ø0.05m). A hole of Ø0.178m is also G. Design of The Return Chamber provided at one end of the longitudinal section of the tank for The return chamber made of mild steel which serves as an the cylindrical furnace placed inside it. Other dimensions are intermediary of heat transfer between the above mention sets as follows; of fire-tubes has a length of 0.15m and diameter of 0.30m. Volumetric capacity of the drum (tank) = volume of The volume of the return chamber + volume of hemisphere.

ISBN: 978-988-19253-5-0 WCE 2014 ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online) Proceedings of the World Congress on Engineering 2014 Vol II, WCE 2014, July 2 - 4, 2014, London, U.K.

d 2 3.0 2 Thus, by proper design of the boiler (for which the in-deep  L   15.0 (8) 4 4 knowledge of heat transfer is of primary importance), as demonstrated in this work, a sizable intensification of heat H. Design of The Smokestack (Exhaust) transfer and noticeable savings in boiler manufacturing cost The smokestack made of mild steel used to the flue can be achieved. We can identify three modes of heat out of the system has a length of 0,20m and diameter of 0. transfer; 15m, The volume of the smokestack 1. Conduction d 2 15.0 2  L   20.0 (9) 2. Convection 4 4 3. Radiation

I. Actual Volumetric Capacity of The Boiler However, they have part to play in the boiler. Though Actual capacity (i.e. volume) of the boiler = volume of the conduction is not considered in simple boiler calculation. drum - total volume of the inner compartment of the boiler. Volumetric capacity of the dram = 292 liters (10) K. Heat Transfer By Convection In Boilers Convection in boilers takes place simultaneously with Total volumetric capacity of the inner compartments = radiation. In tubes of fire-tube boilers more than 90% of heat volume of furnace + volume of fire-tubes on each sections + exchange takes place by convection, while in the the volume of the return chamber + volume of the smokestack radiant part is greater than in tubes. Calculation of convection = {0.0091m + (0.001061m3 + 0.001061m3 4 0.001767m3) + is conducted by standard equations for flows in straight tubes 0.010603m3 + 0.0035343m3} = 0.0271263m3 Therefore, and channels it is also true for the boiler furnaces, whether they are circular or rectangular in cross-section. This picture Actual capacity of the boiler = 0.2918431m3-0.0271263m3 = totally changes when gas flow directly hits the surface 0.2647168m3 =264.721iters involved in convection, such as in the case of the rear of the furnace. The rate of convection is much higher in these cases

TT TT 23 TT 34 and cannot be assessed by classical equations for straight  KQ 12  K  K (11) 12 23 34 flow in tubes and channels. Tests showed much lower gas X12 X 32 X 43 exit temperatures from the furnace than had been calculated  TTTTTTTT For the complete 2312 34 14 which was found to be attributable to lack of taking into wall as a whole; account the heat transfer from impinging jet of the flue-gases.  TTUQ 14 Also test shows an overall improvement in heat transfer in Where, U is the overall heat transfer coefficient of the wall boilers with use of cylinder of high temperature and T is the temperatures of inner and outer wall corrosion resistant material (to have less scaling of surfaces 1 X X X by unburned fuel sulfur, less soot, while also affecting 12 23  34 (12) U K K K radiation and convection). 12 23 34 Heat transfer by convection relies on the bulk movement of a 1 X X X Therefore, 12 23  34 (13) heated fluid in relation to a surface. It features strongly in the U K12 K23 K34 design of plant items such as super-heaters and re-heaters,

where there is gas-to-metal and metal -to-steam convective J. Modes of Heat Transfer in Fire Tube Boiler heat transfers. The importance of heat transfer in boiler design is self- Qconv = h (Th -Tc) Ac ...... (i) evident. In conventional 3 pass fire tube and 4 pass fire tube boilers, only a smaller portion of total heat is transferred in TABLE 3: COMBUSTION TEMPERATURES, SPECIFIC HEAT CAPACITY AND FLUE-GAS ENTHALPY AT THAT the furnance as it has as much as 90% and more heat transfer TEMPERATURE. surfaces in the tubes. The radiation in the tubes is almost non COMBUSTION ENTHALPY DENSITY SPECIFIC HEAT SPECIFIC HEAT TEMPERATURE (H) DIESEL OF DIESEL CAPACITY (CP) OF CAPACITY(CP) OF existent compared to convection, while in the furnance, the OF DIESEL OIL FUEL DIESEL AIR radiation can be even smaller then convection, as the test 540 – 6500C 44500kj/kg 840kg/m3 1.75kj/kg0C 1.006kj/kg0C boilers demonstrated. This is in total contradiction to water-

tube boilers where convection represents less than 20% of Burner Heat Transfer Rate Per Unit Time total amount of heat exchange in furnance can be as high as A burner that should be able to fire a boiler to generate 80%. Hot water test boilers showed additionally that the 80kg/hr, assuming that the water will be heated from ambient percentage of surfaces in tubes could be close to that found in 0 condition that is temperature of 30 C to a temperature of the furnance. The industrial-sized steam test boiler has as low 0 111.4 C at 1.5bar. as 2.3 times more area in the tubes then in the rest of the Quantity of heat energy needed to generate this quantity of boiler. Furthermore it was proved that the convection in the steam is given by furnance of fire-tube boilers can be made even higher than Q = M h g the radiation. s f Where, Ms = mass of steam produced per second The number of boiler tubes is limited by burner fan capability Hfg = Enthalpy of vaporization of water Ms = 80/3600 = 0.0222kg|s to overcome internal pressure loss. By that fact, the general 0 From steam table hfg of water at 111.4 C and 1.5bar is equal direction in designing fire-tube boilers is given; namely to 3 install only as many tubes as are necessary. This requires the to 222 x 10 j/kg Therefore; Q = MS hfg exact analytical assessment of heat transfer in particular boiler sections to which this research work was devoted. Fuel Consumption Rate of The Burner Power output = fuel consumption x calorific value of fuel ISBN: 978-988-19253-5-0 WCE 2014 ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online) Proceedings of the World Congress on Engineering 2014 Vol II, WCE 2014, July 2 - 4, 2014, London, U.K.

Pb = Mf x CV (15) Mf = fuel consumption or mass flow rate Where, P0 = power output Cv = calorific value of fuel of the furnace = Given that calorific value of diesel is 45500kj/kg Heat thefromoutput burner 100  Fuel consumption or mass flow rate of fuel (Mf) in theHeat fuel consumed input)(heat Mass flow rate = Volumetric flow rate x Density Heat output from burner = 55kw Mf = Qf x Pf Heat in the fuel consumed = M Q  f (16)  kj  f P GCVofdiesel  f  kg  3 Where Pf = density of diesel = 840kg|m  kg  Thermal Design Calculation fuel consumptio raten   h The thermal design calculation involves the heat transfer   from all heat sources located in the boiler as outlined: Fire-tube heat transfer at the following sections: a. Furnace section to return chamber. Fire Tubes Heat Transfer Calculation b. Return chamber to 2nd pass tubes • Furnace heat transfer calculation. c. 2nd pass tubes to smokestack. • Fire-tubes heat transfer calculation Radiative Heat Transfer in The Furnace To The Return Chamber Section • Return chamber heat transfer calculation. 4 4 Qrad =  (Th -Tc ) Ac (22) • Smokestack calculation. = Where; qrad heat transfer per unit time (W) Furnace Calculation Convective heat transfer The sensible heat loss of flue gas at furnace exit = Qconv = hc x A x (T) (23) 2 Where; hc = convective heat transfer coefficient (w/m k) m x Cp x T (17) Where; m = mass of flue gas (kg) Conduction heat transfer   TAkc  Cp = specific heat of flue gas (24) 0 Qcond  T = (flue gas temperature - ambient temperature) in C l Theoretical air required from air fuel ratio Where; Kc = thermal conductivity coefficient (w/mk) = Mass of flue gas [mg (P)] = ma + mf 59w/mk πd2 Heat loss = Mp x Cp x T d = heat transfer diameter (m) 0.03 = d x 5 = 0.15m, A = /4 2 Radiation heat transfer from furnace = 0.017671m 4 4 Qrad =  (Th -Tc ) Ac (18) T = (temperature of furnace - temperature of water) °k Where; qrad = heat transfer per unit time (W) L = length of furnace 0.3 = Lx5 = 1.5m -8 2 4   5350177.059   = Stefan Boltzmann const = 5.6703 x l0 (w/m k ) Q   = emissivity of material (mild-steel) used = 0.32 cond 5.1 Th, = hot body absolute temperature (K) = temperature of = 37I.87w water = 5650C = 8380k Return Chamber Heat Transfer Calculation Tc = cold surroundings absolute temperature = temperature Radiative heat transfer 0 0 4 4 of furnace = 30 C = 303 k Qrad =  (Th -Tc ) Ac (25) 2 = Ac = area of the object (m ) Where; qrad heat transfer per unit time (W) 2 d = l 70mm: Ac = 0.02271m Convective heat transfer from furnace Convective Heat Transfer Qconv = hc x A x (T) (19) Qconv = hc x A x (T) (26) 2 2 Where; hc - convective heat transfer coefficient (w/m k) = Where; hc = convective heat transfer coefficient (w/m k) 250w/m2k Conduction heat transfer d = heat transfer diameter (m) = 0.17m,   TAkc  2 Q  (27) d cond A  = 0.02271m2 l 4 Where; Kc = thermal conductivity coefficient (w/mk) = T = (temperature of furnace - temperature of water) 0k Heat Transfer By The Fire Tubes From Return Chamber nd rd L = length of furnace = 40cm = 0.4m 1(2 Pass) To Return Chamber 2 (3 Pass) Conduction heat transfer from furnace Radiative heat transfer 4 4  TAkc Qrad =  (Th -Tc ) Ac (28) Q  (20) = cond l Where; qrad heat transfer per unit time (W)

Where; Kc = thermal conductivity coefficient (w/mk) = 59w/mk Convective heat transfer Qconv = hc x A x (T) (29) L = length of furnace 2 Where; hc = convective heat transfer coefficient (w/m k) Th - hot body absolute temperature (K) = temperature of water Conduction heat transfer Tc = cold surroundings absolute temperature = temperature   TAkc  of furnace Q  (30) 2 cond Ac = area of the object (m ) l Efficiency of furnace Where; Kc = thermal conductivity coefficient (w/mk) Thermal efficiency of the furnace by direct method; ISBN: 978-988-19253-5-0 WCE 2014 ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online) Proceedings of the World Congress on Engineering 2014 Vol II, WCE 2014, July 2 - 4, 2014, London, U.K.

Heat Transfer By The Fire Tubes From Return Chamber .73 10093 rd Boiler Efficiency  2(3 Pass) To The Smoke Stack 55 Radiative heat transfer = 68.96% 4 4 Qrad =  (Th -Tc ) Ac (31) = 69% = Where; qrad heat transfer per unit time (W) Convective heat transfer IV. TEST AND RESULT Qconv = hc x A x (T) (32) The fabricated fire tube boiler was tested to evaluate its 2 Where; hc = convective heat transfer coefficient (w/m k) performances, efficiency and determine its evaporation ratio. Conduction heat transfer The purpose of the performance test is to determine the actual kc  TA Q  (33) performance and efficiency of the oiler and compare it with design cond l values or norms. It is an indicator for tracking day-to-day and Where; Kc = thermal conductivity coefficient (w/mk) season-to-season variations in boiler efficiency and energy Smoke Stack Heat Loss Calculation efficiency improvements. Radiation heat loss Test 4 4 Qrad =  (Th -Tc ) Ac (34) When the burner is turned on and ignition occurs which = Where; qrad heat transfer per unit time (W) produces the required fire in the furnace inside the furnace, a hot flue gas is produced which is forced through the fire- Convective heat loss tubes (by the he p of blower in the burner) and heat is thus Qconv = hc x A x (T) (35) transferred into the water which in turn results in production 2 Where; hc = convective heat transfer coefficient (w/m k) of the required steam that may be used for industrial Conduction heat loss purposes. kc  TA Result Q  (36) cond l The result in this case is a produced at a steam pressure of 1.5bar and a steam temperature of 111.40C also Where; Kc = thermal conductivity coefficient (w/mk) 0 Amount of Steam Generated raising the temperature of the water from 30 C to a generated The amount of steam generated is calculated from the steam quantity of 61.34kg/hr, with a diesel quantity of formula below; 5.2Htres/hr. The efficiency of the burner after getting an adequate combustion air/fuel ratio and heat delivery from the qt M  (37) burner resulted into 64.3%. The efficiency of the boiler was s he also calculated to be 69%. Where: ms - mass of steam (kg/h) qt = calculated total heat transfer (kw) V. CONCLUSION he = evaporation energy of steam (kj/kg) The following conclusions can be drawn from the data and 0 From steam table; under saturated steam of Psat at 111.4 C research that has been mentioned in this paper. Boiler Efficiency , heat transfer and strength of materials Basically boiler efficiency can be tested by the following analysis subjected to temperature and pressure variations methods; were conducted in the theoretical framework of the 1. The direct method; where the energy gain of the laboratory fire-tube steam boiler. Dimensions of major and (water and steam) is compared with the secondary parts were estimated from computations from the content of the boiler fuel. theoretical framework and 3D modelling process for the 2. The indirect method; where the efficiency is the steam boiler was then carried out to present various working difference between the losses and the input. drawings of the steam boiler for possible construction. In working out the efficiency of our boiler we will be Good boiler design practices must take into account the applying the direct method. operation of the boiler and not simply the heat transfer, Direct Method parameters that a good boiler design addresses include; This is also known as 'input - output method' due to the a. Ample furnace volume must be included to absorb a fact that it needs only the useful output (steam) and the significant portion of Radiative heat transfer and allow heat input (i.e. fuel) for evaluating the efficiency. This the low NOx burner designs to function. efficiency can be evaluated using the formula; b. Optimized pressure drop across the boiler heat output 100 convective passes, the pressure drop determines the Boiler efficiency  fan size required for the boiler application. heat input c. Ample steam storage and steam height. The volume of steam and distance from the steam nozzle to the normal water level determine to a very large extent the steam quality and the amount of water that will be carried over into the system. Boiler design and optimization programs have been written to determine the performance of fire-tube boilers. These programs can be applied to analyze a wide variety of the boiler scenarios for many different boiler applications extending from simple gas fired systems to complex Fig 4: Input and Output applications.

ISBN: 978-988-19253-5-0 WCE 2014 ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online) Proceedings of the World Congress on Engineering 2014 Vol II, WCE 2014, July 2 - 4, 2014, London, U.K.

In-flame gas temperature data for lire-tube boilers has been APPENDIX II obtained. The data follows expected trends and has been very useful in the validation of predictive optimization models. This data is compared to predicted results from computational fluid dynamic combustion models and good agreement has been found. This data is used to optimize furnace and heat transfer surfaces for typical fire-tube boilers. Gas temperatures measured at the entrance to the convective tube surfaces provided excellent data that validated the heat transfer sub-models augmented surface tubes have proven to be a valuable resource in the design of fire-tube boilers for many special applications. The advantages of thee augmented tube are that it allows the designer to include larger steam storage and steam height resulting in higher steam quality and rapid load swing handling ability. Using the augmented tube also allows the designer to have a lower overall pressure drop with a boiler efficiency that is still over 81%. The augmented tube boiler may be used to reduce the boiler shell diameter and still maintain standard steam volumes, steam heights, and boiler efficiency. Conclusively, a simple laboratory lire-tube steam boiler is herein presented for fabrication, testing and further improvement. Production of a simple steam boiler of this sort will enable the availability of portable and affordable steam boilers for steam generation processes, especially in school laboratories. The availability of steam boilers in school laboratories will enhance students learning process, especially in the area of thermodynamics, heat transfer and energy studies. Recommendation

I am recommending this research work to any other research Fig 9: Difference technical views of the Boiler institute, students and public to serve as a basis for further research and improvements on fire-tube boiler design. We also recommend that other per-heater devices and feed water REFERENCES pump should be applied for higher efficiency.

[1]. American Society of Mechanical Engineers (ASME) 2010 Boiler and Pressure Vessel Code (BPVCK APPENDIX I http://go.asmc.org /bpvc10.

[2]. American Boiler Manufacturers Association (ABMA) 2004 White Paper: Historical Advancement of Fire- side Heating surface in fire-tube Boilers. PDF. [3]. Boiler and Heaters, Improving Energy Efficiency, Canadian Industry Program -for Energy Conservation, (August 2001) http://oce,nrcan. gc,ca/ pubiications/infosource/pub/cipcc/boilcryhc aters.PDF [4]. Cengel, Y. A. and Boles, M. A., (2006) "Thermodynamics: An Engineering" Approach, 5th Edition, McGraw Hill, Companies Inc. Fig 6: The fabricated Fig 7: Side view of the [5]. Department of Energy (DOE) Fundamentals Handbook fire-tub boiler Boiler "Thermodynamics, heat transfer, and fluid flow" U.S. Department of Energy, Washington, D.C. [Online]. [6]. Fred Landis, Steam Engine Source: Compton’s interactive Encyclopedia (http://www.ferm.unicamp. br/-em313/paginas/consulte/steame.htm. [7]. Kitto, J. B. and Stuitz, S. C., (2005) "Steam: Its Generation and Use", 41st Edition, the Babcock and Wilcox Company, Barberon, Ohio, U.S.A. [8]. Rajput R,K (2006) Design. Laxmi Publications (P) Ltd., New Delhi. [9]. Rajput R.K., (2006) "Thermal Engineering", Laxmi Fig 8: Plan of the Boiler Publications (P) Ltd., New Delhi.

ISBN: 978-988-19253-5-0 WCE 2014 ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online)