Adsorption Refrigeration System for Cabin Cooling of Trucks

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1 Adsorption Refrigeration System for Cabin Cooling of Trucks Harish Tiwari 1, Dr. G. V. Parishwad 2 1 Associate Professor, Mechanical Department, Pimpri Chinchwad College of Engineering, Nigdi, Pune India 2 Professor, Mechanical Department, Government College of Engineering, Pune India Abstract - The work presented in this paper is design development and experimentation of an adsorption refrigeration system powered by exhaust heat with only two control valves. The cooling capacity for a truck cabin is estimated as 1 TR a scale of 3.5:1 is decided and a prototype of 1 kw has been designed and developed and tested in laboratory. A cooling effect of 1 to 1.2 kw has been obtained. The COP of the system is in the range of 0 4 to The dimensions of the system are compact. It can be easily accommodated on a Transport Truck. The total weight of the system for a cooling capacity of 1 kw is 30 kg. The heating time required to achieve the cooling effect is around 10 minutes. Keywords - Prototype, Truck cabin cooling, Engine exhaust, Adsorption cooling. I. INTRODUCTION For automobile air conditioning normally vapour compression refrigeration cycle is used. The cycle run on engine power and consumes around 10% of the total power produced by the engine and thereby increases the fuel consumption (Lambert and Jones, 2006). In case of truck large amount of heat of input around 30% of the total heat supplied is going away with exhaust gases at very high temperature and around 25%to 30% is going away with cooling water. This can be effectively used to develop a heat generated cooling system.(alam,2006) II. LITERATURE REVIEW The first refrigerator automobile air conditioning system was vapour compression refrigeration system and was introduced by Packer in In the last 70 years, automobile air conditioning system has undergone gradual and continual improvements in performance and efficiency as a result of improvements in the individual components (McLaughlin, 2005). Alternative systems powered by heat which can be used in automobiles are solid adsorption cooling systems, thermo acoustic refrigeration, active magnetic regenerator system thermo electric devices and vapour absorption refrigeration (VAR) systems (Zoontjens, 2005),(Johnson,2002).VAR systems were found to be more suitable and efforts have been made to develop (VAR) systems (Koehler, 1997), (Mclaughlin 2005), (Kim and Park, 2007). 337 The feasibility proved theoretically for automobiles but very little could be done to demonstrate it practically for mobile applications. At present no VAR system is available in market for capacities up to 10 kw (Jacob, 2006). A. Adsorption Systems Solid vapour adsorption is similar to liquid vapour absorption system, except that the refrigerant is adsorbed at the surface of another solid known as adsorbent. A report, presented by Metrons transportation centre suggests the suitability of Adsorption systems for vehicles (Christry, 2001). In that report the performance of VCR system and VAR system has been compared. Series of carried experimental results suggest about the feasibility of adsorption systems. NH 3 - activated carbon has been suggested as refrigerant - adsorbent pair. Wang et al. (2009) after comparing the performances of various suitable systems has claimed that adsorption system is more suitable for automobile cooling. Saha et al (2003) in the presented work have demonstrated dual mode silica gel water adsorption chillers design along with various temperature ranges and obtained optimum results for temperature range of 50 o C and 55 o C. Comparison of COP has been presented for three stage mode and single stage multiple modes. Simulation has been presented and the COP is in the range of 0.2 and 0.45 respectively. Wang and Oliveira (2005) have presented the achievements in solid sorption refrigeration prototypes, obtained since the interest in sorption system was renewed at the end of 1970s. The applications included ice making and air conditioning. Wang (2005) in his work claimed to obtain COP of 0.15 for solar application. In the review work the details of performance of adsorption system for different applications with COP has been presented in a tabular form. The COP is in the range of 0.3 to 0.6. Kong et al. (2005) have presented an experimental investigation of the performance of a micro combined, cooling heating and power system driven by a gas engine. In the described system a COP of 0.3 for refrigeration at 13 o C has been obtained successfully. The suggested system can supply electricity of 12 kw and heat load of 28 kw and cooling load of 9 kw simultaneously.

2 Maggio et al. (2006) presents the results of a predictive two dimensional mathematical model of an adsorption cooling machine consisting of a double consolidated adsorbent bed with internal heat recovery. Internal heat recovery enhances the COP. It is suggested that the adsorbent thickness should be limited to 2 to 3 mm for optimum results. Lambert and Jones (2006) has presented a detailed study of vapour adsorption refrigeration system specifically for automobile air conditioning. Adsorption cooling has been compared with other heat generated cooling technologies and it is claimed that adsorption system is the best alternative in terms of size and mass. In the second part of his work he has demonstrated air conditioner for a car successfully. The detailed design of the critical components has also been presented. It has been claimed that the overall weight of the system is ~3.5 percent to the total vehicle mass, which is at par with the mass of current systems. Similar work has been done to demonstrate a cooling system for a car developing 2 kw cooling power with COP 0.22, bed thickness ( δ ad ) of 4 mm and an eight way valve has been suggested in this work (Tamainot et al., 2008 ). Wang et al (2006) has presented a design of an adsorption air conditioner for locomotive driver cabin, powered by 350 o C 450 o C exhaust gases. The cooling power and COP is 5 KW and 0.25 respectively. The cycle time of 1060 s with exhaust temperature of 450 o C cooling air temp of 40 o C and chilled water temp. of 10 o C is achieved. The specific cooling power of 164 W/kg to 200 W/kg has been obtained. Huguess, and Beyene (2008) has presented an approach for the heat recovery from the automotive engine to improve COP. Some innovative methods like use of fuzzy controller, heat pipe, additives in adsorber bed, suction pump with adsorber have been demonstrated in some papers to enhance the performance of adsorption systems (Farzaneh, and Tootoonchi, 2008 ),(Fadar et al., 2009),(Tassou et al., 2009),(Hirot et al., 2008). B. Synopsis of Adsorption Systems The above review is of some selected recent paper. The other referred work is also in the same direction.it is clear that the vapour adsorption system has a strong potential to be used as an alternative cooling system. The presented design suffered from low heat available, low live mass of adsorbing material, leakage problems, inefficient heat transfer, poor thermal conductivity of adsorber bed, settling of adsorbed particles, which cause the absorbent to loose contact with the heat exchanger, and low specific cooling power. These problems can be solved by implementing the suggested improvements mentioned in the review. The surface area volume ratio is higher for activated carbon and the latent heat of ammonia is the maximum after water, so this pair is suggested as suitable adsorbent and refrigerant pair. III. PROPOSED SYSTEM AND WORKING PRINCIPLE The exhaust of an I.C. engine test rig is used to supply the necessary heat to the adsorber. The schematic diagram of the system is shown in Figure 1. The set up consists of two adsorber, two condensers and one evaporator. The condensers are connected to the evaporator through control valves. Two adsorber beds are proposed one in heating mode and another in cooling mode. One of the adsorber is charged with refrigerant ammonia. Two condensers, one evaporator.two control valves and one evaporator are connected as shown in Fig. 2.The condensers and evaporator is fitted with a fan for forced air circulation. Where, 1and 2 are adsorbers,3and 4 condensers,5 evaporator,8 fan, 9 and 10 heat input and output,11 and 12 cooling inlet and outlet, 6 and 7 control valves The Engine exhaust gases enter the adsorber filled with ammonia to heat the adsorber bed at constant mass. Adsorber rejects the refrigerant with the adsorption of heat as the adsorptivity is a function of rise in temperature. The refrigerant gets compressed because of heating at constant mass. The compressed refrigerant passes to condenser through control valve. The refrigerant which is in gaseous state is condensed in the condenser at high pressure depending on the atmospheric temperature. 338

3 On one side of control valve the pressure is high and on the other side of control valve the pressure is low. The control valve outlet is connected to the other adsorber in cooling mode through evaporator and other condenser. The control valve (number 6 in figure) is opened very gradually so that pressure in the adsober (number 1) remains constant. The liquid refrigerant starts getting converted to vapour at low pressure and refrigerating effect is produced. The vapour at low pressure enters the adsorber (number 2) through condenser (number 4). The adsorber absobs the refrigerant, ammonia. The adsober is in cooling mode and is cooled by water. Cooling of adsorber is essential to maintain the adsorptivity of the adsorber. The pressure in the adsober gradually increases. The cooling effect at the condenser is continued till there is a pressure difference in adsorber on and adsober 2. Once the the adsorber is filled with ammonia. The heating is stopped and adsorber one is cooled with water and the cycle is repeated by heating adsober 2. IV. DESIGN OF PROPOSED SYSTEM The main system components are adsorbers, condenser, and evaporator and control valves. These are basically heat exchangers and are designed by using heat transfer equations and thermal correlations. The cooling load for a transport truck is obtained considering the following points. The cooling load required for a medium size truck has been calculated as around 3, so a cooling system of 1 TR should be sufficient to maintain the desired conditions. The useful heat available in the engine exhaust of transport truck is calculated and is more than 50 kw, for a small size truck considered for reference. Whereas the required heat to operate the cooling system with minimum COP of 0.2 is 17.5 kw. So the exhaust potential to drive the system is justified. It is decided to first develop a prototype to study the effect of different variables and optimization of the system parameters. A scale of 3.5: 1 is decided and a prototype of 1 kw capacity is designed and developed in the Laboratory. The adsorber and refrigerant are selected as activated carbon granules and Ammonia. Considering the temperature of exhaust gases and high latent heat of Ammonia this combination is found to be suitable. The adsorbers, condenser, evaporator and the control valves are the main components of the system. The adsorber has been designed and developed to enhance the heat transfer. The other components are readily available like the evaporator and condenser for automobiles and the control valves used in ammonia refrigeration systems. A. Design of Adsorber In adsorption refrigeration system adsorber is the most important component Adsorber works like generator as well as absorber both of an absorption system. It is a shell and tube double pipe heat exchanger as shown in Figure 2. There are three concentric tubes of stainless steel. The adsorbing material is filled between the gap of inner tube and the middle tube. The adsorbing material is activated charcoal and the refrigerant is ammonia. End covers are fitted at the ends of these tubes to hold the adsoerbing material. The exhaust gases flow through the inner tube and the annular space between the outer tube and the middle tube. The adsorbing material is heated from both side i e from inside and outside. Fins are provided from outside of the middle tube and to the inner tube from inside to enhance heat transfer from exhaust gases to the adsorbing material. 10 % aluminum chips by weight are added to the adsorbing material to enhance the conduction in the adsorber bed. The adsorbing material is closely packed in the space. The adsorptivity of activated carbon at 60 o C is 30% and that at 160 o C is around 0 %. The system is designed for heating and cooling time of 450 s. Adsorber temperatures are decided as T ad,max = 160 o C and T ad,min = 60 o C. Designed refrigerating effect (R.E.) = 1 kw, latent heat of evaporation of ammonia (L) at evaporator pressure is 1035 kj/kg. Amount of ammonia is obtained by dividing the R.E. by latent heat as 0.45 kg. Mass of adsorber, m ad is obtained as 1.65kg. Density of adsorbing material ( ad ) is 680 kg/m 3 adsorbent thickness = 10 mm. Volume of adsorber, is calculated, V ad = m 3.. Heat required to heat or cool adsorber between 60 o C and 165 o C is the summation of sensible heat and latent heat of refrigerant at evaporator pressure. It is given by equation (1) and equation (2). Q sensible, heating = [(m ad C pad ΔT ad ) + (m st C pst ΔT st )] Δt (1) Q latent heating = [m ad (X 2 - X 1 ) x (H 2 - H 1 )] Δt (2) Q adsorber = Q asensible,heating + Q latent heating (3) From equation (3), The heat required to heat or cool the adsorber (Q ad,heating ) is calculated. Q ad,heating = 2 kw for getting a cooling effect of 1 kw. The heat transfer area is calculated from the following equation. Q = U x A x T ad (4) The overall heat transfer coefficient, U o depeds upon the inside and outside heat transfer coefficients and the conductance through steel tubes and adsorbing material. 339

It is calculated using overall heat transfer through a compound cylinder. The area required for heat transfer to supply the heat of 2 kw to the adsorber is calculated as A ad = 0.6 m 2.

4 It is calculated using overall heat transfer through a compound cylinder. The area required for heat transfer to supply the heat of 2 kw to the adsorber is calculated as A ad = 0.6 m 2. The area available for heat transfer in this case is 0.45 m 2. Fins are provided on the middle shell and inside the central tube increases the area to around 0.8 m 2. This area should be sufficient for heat transfer. The final dimensions and main features of the adsorber of the system are given in Table I. The theoretical COP is calculated as 0.5. The pressure drop in the adsorber heat exchanger is given by following equation [5]; P = [f G 2 s (N b +1)D s ] (2 x x D e ) (5) f = e ( lnRe) (6) Pressure drop is obtained as 0.42 Pa, the design is safe, as allowable pressure drop is 4 kpa [11, 12]. B. Condenser Condenser will be exposed to atmospheric air striking with truck velocity. Temperature difference is assumed to be 7 0 C. Q c = 2 kw. The standard condenser used in automobiles has been used for the experimentation. A fan is fitted to the condenser for condensing the refrigerant in the condenser. Condensers are two in number and are connected to each adsorber. The outlet of the condenser is connected to control valves. (Photo condenser) C. Evaporator The evaporator is a cross flow box type compact heat exchanger. It is exposed to the cabin to be cooled. In the experimental set up the evaporator is provided with a fan. The designed cooling temperature is 30 0 C. The evaporator is connected to both the condensers through control valves. It has been designed to have a temperature difference of around 15 0 C. The evaporator of this system has to work in both directions as the refrigerant will be coming as inlet from one side as well as from other side also depending upon heating and cooling mode of the adsorbers. It is fitted with a fan for forced air circulation. V. DEVELOPMENT OF A PROTOTYPE A small prototype for a cooling capacity of 200 W has been designed and built as shown in the Fig. 3. Two adsorber developed and connected to condenser coil. An evaporator coil was placed between the two condenser through control valve. Two pressure gauges were fitted to the adsorber and tested as first stage of developments. TABLE I MAIN FEATURE OF THE ADSORPTION REFRIGERATION SYSTEM Refrigerant used Adsorbing (coconut shell) material Ammonia Activated charcoal 4 mm granule size Mass of adsorbing material in each adsorber Mass of refrigerant Weight of each adsorber Length and Diameter of adsorber Weight of condenser with fan Weight of evaporator Overall weight of the system 1.8 kg 0.6 kg 10.5 kg 1.1 m and 110 mm. 2.4 kg 2.4 kg 30 kg Fig. 2 Condenser Number of control valves Control valve size 10 mm

Fig3 Prototype of Adsorption system VI. EXPERIMENTAL RESULS The experiments have been carried out on the prototype using a blower stove as a heat source.

5 Fig3 Prototype of Adsorption system VI. EXPERIMENTAL RESULS The experiments have been carried out on the prototype using a blower stove as a heat source. One of the adsorber was heated and another cooled simultaneously. The results are tabulated in Table II. S. N Heating time(s) TABLE II EXPERIMENTAL RESULTS Fuel consumptio n-ion (gm) RE (W) Heat supplied (kj) COP VII. CONCLUSIONS The engine power required to run an air conditioning system can be saved by using waste heat powered cooling system. After literature review in the field of alternative cooling systems powered by heat, adsorption air cooling systems with activated carbon and NH 3 as adsorbent refrigerant pair is selected and used in the present system. In the present system solid material is used as adsorber which makes the system suitable for mobile applications. The design COP of the system is around 0.5 for a cooling capacity of 1 kw. The overall weight of the system for cooling capacity of 1 TR is estimated as 30 kg. The system is quite compact and can be installed in a truck. The reduced number of valves makes the system more reliable and leakage free. The innovative heat exchanger as adsorber reduces the heating and cooling time. The mass of ammonia in the system is 600 gms. Acknowledgments This work has been supported by Pimpri chinchwad College of Engineering (PCCOE) Nigdi Pune 44, Maharashtra India and Board of College and University Development, (BCUD) University of Pune, Pune , Maharashtra, India. The authors are thankful to PCCOE and BCUD and concerned authorities. Nomenclature A Area of heat transfer (m 2 ) C p Specific heat at constant pressure (kj/kg K) CV Calorific value of fuel (kj/kg) D Diameter of shell (m) d Diameter of tube (mm) G Mass density (kg/m 2 s) h Heat transfer coefficient ( W/m 2 K ) H Enthalpy of refrigerant (kj/kg) k Thermal conductivity (W/m K) L Length of tubes (m) m r N b n PR Mass flow rate of refrigerant ( kg/s) Number of baffle plates Number of tubes Pitch ratio 341

6 Q Heat duty (kw) T ad Temperature of adsorber bed ( o C) t time (s) U o Overall heat transfer coefficient (W/m 2 K) X Concentration of ammonia (%) Greek letters Density (kg/m 3 ) Subscript ad st steel eq ex r f adsorber equivalent exhaust refrigerant fuel REFERENCES [1 ] Alam, S, 2006, A Proposed model for Utilizing Exhaust Heat to run Automobile Air-conditioner, The 2 nd Joint International Conference on Sustainable Energy and Environment November 2006, Bangkok, Thailand. [2 ] Aprachi, V., Kao S. H., Selamet A., Introduction to Heat Transfer, 1999, Prentice Hall, Inc. Upper Saddle River, NJ, U.S.A [3 ] Christy.C. and Toossi,R., 2001 Absorption air conditioning for containership and vehicles, Final report metrons transportation center California state university. [4 ] Furzanchy, A., Ali, A. and Tootoonchi, 2008, Controlling automobile thermal comfort using optimized fuzzy controller, 2008, Applied Thermal Engineering, 29, [5 ] Hirota, Y., Sugiyama, M., Kubota, F.,Wutunable, N., Kobayashi, M., Hasatami, M.and Kanamori, 2008, Development of a suction pump assisted thermal and electrical hybrid absorption heat pump. Applied Thermal Engineering, 28, [6 ] Johnson, V. H., 2002, Heat-Generated Cooling Opportunities in Vehicles,SAE technical paper, [7 ] Jakob, U., Eicker. U., Schneider, D., and Teuber, A., 2007, Experimental Investigation of Bubble Pump and System Performance for a Solar Driven 2.5 KW Diffusion Absorption Cooling Machine, [8 ] Heat Set 2007, Heat transfer in components and systems for energy technologies Chambery, France. [9 ] Kim, B., and Park, J., 2007, Dynamic Simulation of a Single-effect ammonia-water absorption chiller, International Journal of Refrigeration Vol. - 30, [10 ] Kong, X., Wang, R., Wu, J., Hung, X., Huang, Y., Wu, D. and Yu, Y.,2005, Experimental investigation of a macro combined cooling, heating and power system by a gas engine. International journal of refrigeration, 28,77 87 [11 ] Lambert, M. and Jones B., 2005 a, Automotive absorption air conditioner powered by exhaust heat part 1, Automobile Engineering proc. I Mech. Vol 220. [12 ] Lambert, M. and Jones,B., 2005 b, Automotive absorption air conditioner powered by exhaust heat. Part 2, detailed design and analysis. Automobile Engineering proc. I. Mech. Vol 220. [13 ] Maggio, G., Freni, A., and Restuccia G., 2006, A dynamic model of heat and mass transfer in a double bed absorption machine with internal heat recovery, International Journal of Refrigeration 29, [14 ] Mathur, M. and Sharma,R., 2001, A corse in Internal combustion engines, Dhanpat Rai and Sons Pvt. Ltd. [15 ] McLaughlin, S., 2005, An Alternative Refrigeration for Automotive Application M.S. Thesis, Mechanical Department, Mississippi state Mississippi. [16 ] Sadik, K. and Hongtan, L., 1997, Heat exchangers selection rating and thermal design,crc Press LLC, [17 ] Saha B., Komaya, S., Kashiwagi, T., kisawa, A.A., Ng, K., and Chau, H., 2003, Waste heat driven dual mode, multistage, multiplied regeneration absorption system, International journal of refrigeration [18 ] Tassou. S., Lille,G. and Y. Ge, Y., 2009, Food transport refrigeration approach to reduce energy consumption and enviournment impacts of road transport, Applied Thermal Engineering, 29, [19 ] Tumainot, Z., Metacolf, S. and R. Critoph, 2009, Novel compact sorption generators for car air conditioning, International journal of Refrigeration [20 ] Wang L., Bao, H., Wang, R. 2009, Comparison of the performances of absorption and resorption refrigeration systems powered by the low grade heat, Renewable Energy, 34, [21 ] Wang, D., Xia, J. and Wu, 2006, Design and performance prediction of a novel zeolite water absorption air conditioner, Energy conservation and management 47, [22 ] Wang R. and Oliveira, R., 2005, Absorption refrigeration an efficient way to make good use of waste heat and solar energy, International sorption Heat Pump Conference, Denver, June 22, [23 ] Zoontjens, L, Howard C, Zander A and Cazzolato B, 2005, Feasibility Study of an Automotive Thermo acoustics Refrigerator, Proceedings of Acoustics,

Review of Experimental Evaluation of Adsorption Cooling System Powered By Exhaust Heat of an Automobile

Review of Experimental Evaluation of Adsorption Cooling System Powered By Exhaust Heat of an Automobile Prof.S.A.Wani 1, Prof.Amod.P.Shrotri 2, Mrs.S.P.Mane 3, Prof.S.M.Gheji 4 1, 3, 4 Assistant Professor,