Journal of Information and Computational Science ISSN: 1548-7741

REVIEW - DESIGN OF SYSTEM DRIVEN BY ENGINE EXHAUST GAS FOR VEHICLES

1 2 3 VINEETH P. BABU , R. VASANTH , VARUN BABU M K

1Post Graduate in Thermal Engineering, R.V.S College of Engineering And Technology, Coimbatore, TamilNadu. 2Assistant Professor, Department of Mechanical Engineering, R.V.S College of Engineering And Technology, Coimbatore, TamilNadu. 3Post Graduate in Thermal Engineering, R.V.S College of Engineering And Technology, Coimbatore, TamilNadu.

Abstract

Heat generated cooling is a technique of refrigeration where the required cooling effect is obtained by using heat energy as input. At present, the conventional cooling systems used in automobiles are engine driven Vapour Compression Refrigeration (VCR) systems. Some of the alternative heat generated cooling technologies suggested by researchers in their work, which can replace engine driven systems are - solid adsorption cooling systems, absorption cooling, Sterling cycle cooling, thermo acoustic refrigeration etc. In this study, a comparison of vapour compression, vapour absorption and vapour adsorption refrigeration systems is carried out. Literature review suggests that the adsorption refrigeration can be a suitable option for mobile applications and for smaller capacities. The vapour adsorption system has a strong potential to be used as an alternative cooling system. The estimated availability of exhaust gas energy suggests the capacity of cooling which can be greatly enhanced for a dedicated system. This thesis proposes an innovative, compact, and improved adsorption refrigeration system design review, powered by engine exhaust heat.

1. Introduction

In India road transportation is a major mode of transport for goods over large distances using trucks. In summer the atmospheric temperature in some parts of India touches 45oC. In such a condition, the temperature inside the cabin of a transport truck can even exceed 50oC and it becomes extremely difficult to operate for the driver and the other operators. It may affect the driver’s health as well as may cause accidents. It affects the economy as transportation time increases. So there is a need for a cooling system to keep the temperature of the cabin in control. But presently the transport trucks in India and in most parts of the world are not provided with system for cabin cooling, as it is not economically viable with current technology.

At present, the conventional cooling systems used in automobiles are engine driven Vapor Compression Refrigeration (VCR) systems. The cycle runs on engine power and consumes around 10 to 15% of the total power produced by the engine and thereby increases

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the fuel consumption also by 10 to 15% and thus increases the per kilometer running cost [1, 2]. At present no cooling technology is commercially d e v e l o p e d , w h i c h can provide cooling in automobiles w i t h o ut a f f e c t i n g f u e l consumption. This is a major reason for which the cabin cooling of the truck is avoided presently. Considering present energy crises all over the world, it is very much necessary to explore new technologies and potential to satisfy the need of society. At the same time, the efficient management of production and energy conservation is also equally important. Therefore, a solution for cabin cooling of truck is required without increasing fuel consumption. Cabin cooling of truck or air conditioning in automobiles is just an application, there are many other applications where cooling can be provided using energy available in waste heat. Therefore, from energy conservation point of view also there is need for a technology which can provide solution of cabin cooling of trucks using waste heat thereby saving a large amount of energy required for cooling and refrigeration [2, 3].

1.1 Engine Exhaust Heat as a Source of Energy

From heat balance calculations it is clear that in automobiles, around 30% of the total heat energy supplied is going away with exhaust gases at very high temperature and around 30% of the total heat supplied is going away with cooling water. The breakup of energy consumption is shown in Fig. 1.1. In automobiles, the exhaust gas temperature is in the range of around 200 to 600oC. A part of this heat energy can be used to produce the required refrigerating effect for cabin cooling. The literature in the field of refrigeration and air conditioning suggests that there are some systems, which run on heat to produce a cooling effect [3].

The trucks which are used for transport generally have engine capacities more than 100 kW. The heat required for operating a heat powered cooling system for capacity of 1 TR (3.5 kW), with a minimum Coefficient of Performance (COP) of 0.25 is 14 kW. The COP for a heat generated cooling system is defined as the ratio of cooling effect to the heat supplied. The useful available heat in engine exhaust is more than 50 kW, so it is clear that the required heat for running a heat operated cooling system is very less as compared to the available heat in the engine exhaust. Thus it can be stated that there is enough potential for the development of a system that runs on heat rather than engine power for cabin cooling of the truck.

By solving the problem of cabin cooling of the truck, the truck driver will be provided with better working conditions, which will result in a reduction in fatigue to the driver and ultimately reduction of transportation time. And this can be achieved with a small initial cost and small addition of weight to truck. As the system is using the heat available in exhaust the temperature of exhaust gases going to atmosphere is reduced and thereby the reduction in global warming can be an additional advantage. is proposed to be the which is an environmentally friendly refrigerant so it may replace the Chlorofluorocarbon (CFC) , used in vapor compression refrigeration. The solution of the problem can further be used as a model for development of cooling system operated by waste heat for other applications. This system can solve many energy conservation problems and has the potential to become a technology of the future [4].

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(a) Losses of energy along with exhaust and proposed cooling system

35% 30%

25% 20% S . 15% I 10% C 5% . 0% I

POWER COOLANTEXHAUSTRADIATION

(b) Losses of energy (heat balance)

Fig. 1.1 Breakup of energy supplied to the engine and proposed cooling system [40]

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1.2 Vapour Adsorption System as Alternative Technology

The cabin cooling of the truck can be achieved by using Vapour Compression Refrigeration (VCR) system, Vapour Absorption Refrigeration (VAR) system or by using Adsorption Refrigeration (AR) system. The dependence on engine power and the use of Chlorofluorocarbon (CFC) refrigerants are the two main limitations of vapour compression refrigeration systems, which make it an unacceptable solution for cabin cooling of the truck. So there is a need for the development of a cooling system for truck which can operate on the available engine exhaust heat. From literature review it is observed that vapour absorption refrigeration and adsorption refrigeration are the two heat generated cooling technologies, which have potential to become alternatives of vapour compression refrigeration. The use of vapour absorption refrigeration or adsorption refrigeration system can solve the problems associated with vapour compression refrigeration. A comparison of vapour compression refrigeration, vapour absorption refrigeration with adsorption refrigeration is presented in Table 1.1. The working principle and the main features of these three systems are as follows:

The systems which have been used over the years for automobile air conditioning are based on vapour compression refrigeration technology. Vapour compression refrigeration system mainly comprises four principal components namely compressor, condenser, evaporator and expansion valve. The working fluid which flows through these components is called refrigerant. The refrigerant changes its phase from liquid to vapour and vapour to liquid and thereby transfers heat to develop the required refrigerating effect. The working principle is explained with the help of a schematic diagram as shown in Fig.1.2 (a). The compressor of the vapour compression refrigeration system is driven by the power of the engine. Many developments have taken in automobile air conditioning but most of them are concentrated towards improvement in the system or system components. No alternative technology could come up which can replace vapour compression refrigeration system for automobile air conditioning.

Efforts to address the problem of dependence on engine power for air conditioning in automobiles motivated researchers towards heat generated cooling systems. Vapour absorption refrigeration system is one of the potential alternatives, which can replace the vapour compression refrigeration. Vapour absorption refrigeration system is a refrigeration system, where the compressor of the vapour compression refrigeration system is replaced by a combination of an absorber and a generator. In vapour absorption refrigeration a combination of liquid absorbent and refrigerant is used.

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Table 1.1 Comparison of vapour compression, vapour absorption and vapour adsorption refrigeration system

Vapour Vapour Absorption Adsorption Compression Refrigeration Refrigeratio Refrigeration (VCR) (VAR) system n (AR) system system 1. The VCR system is The VAR system is a The AR system is driven by mechanical heat driven system. a heat driven power. system. The commonly used 2.The refrigerants used refrigerants are environment- Commonly used are not environment- friendly. refrigerants are friendly environment- The refrigerants used in friendly 3. The refrigerants used in VAR VCR cause Ozone depletion does not cause Ozone The refrigerants used in depletion VAR does not cause 4. More number of ODP moving parts Less number of moving parts Less number of 5. COP is in the range of moving parts 2.5 to 3.5 COP is less than that of VCR COP is less than that of 6. The VCR systems system VCR system. are available in small . sizes AR system can be VAR is uneconomical developed for 7. The VCR system is and difficult to build for less smaller cooling used in automobile air than 10 capacities conditioning TR cooling capacity The AR system is 8. The overall weight suitable for automobile and size are suitable for The VAR system is not air conditioning automobile suitable for automobile air applications. conditioning The overall weight The overall weight and size is and size is at par not suitable for automobile with the VCR system application

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(a) Vapour compression refrigeration system

(b) Vapour absorption refrigeration system

(c) Vapour adsorption refrigeration system

Fig. (1.2) Schematic working cycles of (a) Vapour compression, (b) Vapour absorption and (c) Vapour adsorption refrigeration system

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Vapour absorption refrigeration system is a heat operated system of refrigeration where the generator is heated by using a heat source. When the generator is heated the refrigerant is separated from the absorbent and is compressed in the generator. The compressed refrigerant is passed to the condenser and the liquid absorbent is pumped back to the absorber to absorb the refrigerant coming out from evaporator. The other principle components condenser, evaporator and expansion valve are the same as those of the vapour compression refrigeration system. The other processes of refrigeration are also the same as those in vapour compression refrigeration [5]. The working principle of the system is explained in the schematic diagram Fig.1.2 (b). The working of the system is explained in the schematic diagram Fig. 1.2 (c) The adsorption refrigeration principle and the related theory of adsorption are explained in the next chapter of the report.

2. Literature Review

Automobile air conditioning has a history of more than 70 years. The first automobile air conditioning system was introduced by Packer in 1939 for car air conditioning. This air conditioner was based on the principle of vapour compression refrigeration system. The compressor of the vapour compression refrigeration system requires power and this power is taken from the engine. As mentioned earlier the additional power required to run the system increases fuel consumption. 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. But the principle technology (i.e. VCR) remains the same, no significant advances took place in this long- existing technology over the decades [7].

In the last few years with the increase in the fuel prices and depleting oil reserves the energy resource availability problems are becoming more and more critical. Researchers and scientists from different parts of the world have been focusing on the issue of energy conservation. Automobile air conditioning is one such area where there is a potential for energy conservation as there is a huge amount of energy available in engine exhaust, which can be used for air conditioning. Many researchers in different parts of the world have been working to develop a solution for automobile air conditioning using the energy from exhaust gases. A review of this work is presented here in the following sections.

2.1 Heat generated cooling techniques

Heat generated cooling is a technique of refrigeration where the required cooling effect is obtained using heat energy as input. Some of the alternative heat generated cooling technologies suggested by researchers in their work, which can replace engine driven systems are - solid adsorption cooling systems, absorption cooling, Stirling cycle cooling, thermoacoustic refrigeration, active magnetic regenerator system, thermoelectric devices. The comparison of various features and performance, the economical feasibilities and state of research of these heat driven systems have been presented in the reviewed papers. The various other issues associated with these technologies like material issues, advantages, and shortcomings, applications have also been outlined in these papers [3, 8, and 9].

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Iyer et al. [9] in his work has presented an experimental study to explore the heat potential of car engine exhaust gases to run a turbine of 1 kW. The power developed by the Turbine has been used to run the compressor of vapour compression refrigeration system. A cooling effect with temperature drop of 4oC has been achieved successfully. In this study it was observed that a minimum engine speed required to run such system is more than 1400 rpm.In the last few decades vapour absorption refrigeration and solid adsorption refrigeration are two heat generated cooling techniques that have attracted the attention of many researchers, and a lot of research is in progress on these technologies. Considering the proposed work a literature review in the field of automobile air conditioning has been carried out and, is presented in the following sub- sections on vapour absorption and adsorption refrigeration technologies and their applications.

2.2 Vapour Absorption Refrigeration System

Vapour absorption refrigeration (VAR) is one of the oldest refrigeration technologies. French scientist Fero Dinonel developed the first absorption refrigeration machine in 1816. Practically the vapour absorption cycle was first developed as Ammonia water system around the start of the 20th century. VAR is a heat operated cooling system, which attracted the attention of researchers for automobile air conditioning mainly from early 90s [10]. Researchers working in the field of refrigeration have been trying to explore the potential of waste heat available in engine exhaust for operating absorption refrigeration system. Some such efforts are briefly discussed below.

Mclaughlin [10] has done an exhaustive study of an alternative refrigeration system for automobile applications. In this study absorption refrigeration has been considered as an alternative technology of cooling. The design and modeling of the absorption refrigeration system have been proposed with Li Br and water as working pair. In this study the engine coolant water has been proposed as a source of heat. It has also been stated that the generator temperature should be more than 93oC and the system can work at atmospheric temperature less than 38°C.

Koehler et al. [11] studied the absorption refrigeration system using waste heat. In this work a computer simulation has been presented for a prototype of an absorption system for food transport truck refrigeration using engine exhaust heat. The Coefficient Of Performance (COP) values of this non-optimized single-stage ammonia-water absorption cycle varied between 0.23 to 0.3. In this work the result shows that the system can be realized for long- distance driving on flat roads.

Manzella et al. [12] have presented an experimental study of an ammonia-water absorption refrigeration system using engine exhaust. The experimental studies were conducted on an stated that it took a time of 3 hours to reach a steady- state temperature of 3 to13oC. It has been claimed in this paper that introduction of absorption cooling system does not cause a significant pressure drop in the engine exhaust system. In the experimental study a cooling effect of 14.9 to 18.4 W could be achieved with a very low COP of around 0.05.

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Hilali and Soylemez [13] have presented an optimization analysis for estimating the proper size of the absorption type automotive air conditioning system that uses waste exhaust heat as input. In this paper a dynamic simulation of an ammonia-water absorption system has been presented for 10.5 kW absorption system. This optimization analysis suggested the optimum effectiveness of the generator as 0.75 with a heat transfer area of 1.07 m2 at a COP of 0.5.

Venkatesan et al. [14] in their study have analyzed the possibility to drive a vapour absorption system using exhaust gases from the engine for car air conditioning. In this study the cooling load required to cool a car cabin up to a temperature of 20oC is calculated as 0.714 TR. The minimum theoretical heat required to drive this system has been calculated as 2.63 kW. The minimum useful heat available in the exhaust of a Honda City car, considered for this study, has been calculated as 5.77 kW. Hence it was claimed that it is possible to drive an absorption refrigeration system by car engine exhaust.

Salim [15] in his theoretical study and analysis has claimed that exhaust heat energy is capable of powering and producing a cooling effect up to 1.2 tons of refrigeration using vapour absorption cycle. The theoretical COP for absorption cycle has been obtained as 0.46. In his study Ozone Depletion Potential (ODP) and the Global Warming Potential (GWP) of R-134a, which is the current refrigerant employed in today’s vehicle has also been discussed. The technical paper stated that Ozone Depletion Potential (ODP) of R-134a is zero but the GWP of R-134a has been stated as 1300 as appose to the base that is carbon dioxide, that has GWP value of 1 by definition.

Pongtornkulpanich et al. [16] in their work have presented an absorption cooling system powered by solar energy. The system has been designed and experimented using solar energy for a cooling capacity of 10 TR using LiBr/H2O. The collector area for an evacuated tube solar collector and the cost analysis has been presented. It states that the initial cost of the proposed system is higher but the system can become cost-effective if the operating costs are compared.

Jacob et al. [17] in their technical paper investigated the development and testing of single- stage solar or waste energy heated ammonia/water (NH3/H2O) diffusion- absorption cooling machines (DACM). The designed cooling capacity of the cooling machine was 2.5 kW at evaporator temperatures of -10°C. The pilot plants were gradually analyzed and stepwise improved the second pilot plant now reaches a maximum cooling performance of 2 kW and a coefficient of performance of 0.45.

The above literature on the absorption refrigeration shows that there is potential in the engine exhaust to drive an absorption air conditioning system. A careful examination of the work presented in the literature reviewed, reveals that very few of the proposed designs have ever been built even as a prototype. The COPs obtained are very low, in some cases less than 0.1 with a cooling power less than 100 W. In some cases some experimentation has been done

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but that too in stationary conditions. The vapour absorption systems for automobile air conditioning are not feasible from thermodynamic and manufacturing point of view for mobile applications [18, 19]. Lambert and Jones [18] in their work have presented a review of heat generated cooling techniques. In this study, they have presented the analysis of various heat operated cooling systems and suggested the use of adsorption technology over the other heat generated technologies, including VAR for automobile air conditioning application. It is claimed that adsorption system is the best alternative for mobile air conditioning using the heat of engine exhaust. A review of adsorption refrigeration system is presented in the next section.

2.3 Vapour Adsorption Refrigeration System

Adsorption refrigeration system with zero Ozone Depletion Potential (ODP) refrigerants, powered by heat received increased attention from the last two decades. Unlike a conventional refrigeration system driven mechanically by a compressor, an adsorption refrigeration system is a heat-driven machine. Wang et al. [19] in their review paper have presented a comparison of absorption and adsorption refrigeration technology. In this review paper adsorption refrigeration has been claimed as a better alternative over absorption refrigeration systems. It has been stated that adsorption refrigeration system can handle wide range of temperatures from 50 to 500oC, whereas, in VAR the source temperature should be at least 70oC and further the source temperature should not be more than 200oC. The study also stated that absorption systems are not suitable for mobile conditions as the absorbent is in liquid state, whereas in the adsorption system the adsorbent is in solid state. The review paper further claimed that the adsorption system is much simpler than the absorption system.

Wang et al. [20] have studied the adsorption refrigeration technology and presented a review of work done in the field of adsorption refrigeration. These technical papers have studied properties of different refrigerants and adsorbents, commonly used working pairs for adsorption cycles, characteristics, advantages and disadvantages of different adsorbents and refrigerants. The selection of adsorbent refrigerant working pair based on application and availability of heat has also been discussed. This paper has also presented the different adsorption refrigeration cycles, different types of adsorption systems like physical adsorption system, chemical adsorption system and a combination of both. This paper has studied the deterioration of adsorption capacity in physical adsorption systems. The methods for the measurement of adsorption capacity and the future research direction of adsorption working pairs have also been analyzed. Saha et al. [21] in the presented work have demonstrated dual-mode silica gel water adsorption design along with various temperature ranges. They obtained optimum results for temperature range of 50 and 55oC. A 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 [22] have presented the achievements in solid sorption refrigeration prototypes, obtained since the interest in the sorption system was renewed at the end of 1970s. The applications included ice making and air conditioning. In their work they have claimed to obtain COP of 0.15 for solar application. In his review work the details of performance

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of adsorption system for different applications with their COP have been presented in a tabular form. The COP is in the range of 0.3 to 0.6. A report, presented by Christy and Toosi from Metrons Transportation Centre California, have discussed the principle of adsorption refrigeration. The report suggests the suitability of adsorption systems for vehicles. In that report the performance of vapour compression refrigeration system and vapour adsorption refrigeration system has been compared. This report presented an investigation of the feasibility of meeting the cooling needs for commercial tractor-trailer refrigeration and transit bus air conditioning using engine exhaust. The report states that the system size weight and heat balance are well within a reason of a feasible design. In this study the adsorption refrigeration system has been designed for activated carbon- ammonia and activated carbon - R134a as adsorbent refrigerant pairs. In this work NH3 - activated carbon has been suggested as a suitable refrigerant - adsorbent pair for automobile application [23]. Kong et al. [24] 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 13oC has been obtained successfully. The suggested system can supply electricity of 12 kW, the heat load of 28 kW and a cooling load of 9 kW simultaneously. Maggio et al. [25] have presented 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 [26] in the second part of their work have demonstrated the design of air conditioners for a car using heat of engine exhaust. The detailed design of the main components of the proposed system has also been presented. The proposed system is an adsorption system with two adsorbers heated by thermic fluid. The thermic fluid is proposed to be heated by engine exhaust in a heat exchanger. It has been claimed that the overall weight of the system is ~ 3.5 percent to the total vehicle weight, which is at par with the weight of current vapour compression refrigeration systems. The specific cooling power (cooling power per unit mass of adsorber) for the presented design has been claimed as 0.5 kW per kg of adsorbing material with a cycle time of 900 s. Tumainot et al. [27] have designed and developed a prototype of an adsorption air conditioner using activated carbon-ammonia pair. In this work, a novel adsorber has been designed and developed which, improves the heat transfer and has low thermal mass. The prototype produced 2 kW cooling power with COP of 0.22, using engine cooling water. It has been studied the specific cooling power ranges from 0.65 to 0.80 kW/kg of adsorbing material for the developed system. The bed thickness of the adsorbing material (δad) of 4 mm and an eight- way valve has been suggested in this work. Jiangzhou et al. [28] have presented a design of an adsorption air conditioner for locomotive driver cabin, powered by exhaust gases at 350 to 450oC. The cooling power and COP are 5 kW and 0.25 respectively. The cycle time of 1060 s with exhaust temperature of 450oC cooling air temperature of 40oC and chilled water temperature of 10oC is achieved. The specific cooling power of 164 to 200 W per kg has been obtained. Salvatore et al. [29] have presented the design of an adsorption cooling system using the zeolite water system. The overall volume and weight of the machine are 0.170 m3 and 60

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kg respectively. The experimental results obtained showed that the system delivered an average cooling power 1 to 2.3 kW and a cooling COP 0.25 to 0.45, at a desorption temperature of about 90oC. The system consists of a double-bed adsorber connected with an evaporator and a condenser and driven by energy coming from the engine coolant. Abdullah et al. [30] in their work have presented the various techniques of production of activated carbon and the possibility to use Pam oil-based activated carbon for adsorption refrigeration. The paper also discusses the need for change from the existing technology of vapour compression refrigeration. It has been studied that the adsorption refrigeration technology can satisfy the norms set by Montreal Protocol. Some researchers have been concentrated on the modeling of adsorption refrigeration systems. COP and the specific cooling power which are the most important parameters of adsorption systems can be evaluated from these models. [31, 32] Deng et al. [33] have presented a review of thermally activated cooling technologies for combined cooling, heating and power systems. The difficulties and problems associated with adsorption systems have been discussed in this paper. It has been stated that there are three main problems in adsorption refrigeration technology, one is the low thermal conductivity of the adsorbent; the second is the relatively low cycle mass of the working pair, which means that the mass of refrigerant adsorbed and desorbed between adsorption phase and desorption phase, is low; the third is the effective utilization of heat. These problems lead to low COP (0.4 to 0.5) and a large volume and mass of the system. The innovative methods suggested in the reviewed papers to make it a practical solution are, additives in adsorber bed, use of suction pump with adsorber, finned absorber tubes, etc. The summary of literature review is as follows: The literature review suggests that a lot of work has been carried out to find a solution for automobile air conditioning using heat of engine exhaust. Many heats generated cooling techniques are available with distinctive features. Vapour absorption and adsorption refrigeration are the two potential technologies. The absorption refrigeration is a technique that is well developed and is suitable in the case of stationary application and for higher capacities. The adsorption refrigeration can be a suitable option for mobile applications and for smaller capacities. The vapour adsorption system has a strong potential to be used as an alternative cooling system. From literature review it is also clear that sufficient background is available to develop this technology to propose it as a solution for cabin cooling of truck using engine exhaust. In the literature review in the field of adsorption refrigeration, many adsorbents and refrigerants have been suggested. The various adsorbents which have been used for adsorption refrigeration include activated carbon, silica gel, zeolites. The various refrigerants which have been mainly used for adsorption system are water, ammonia, and methanol. The adsorbent refrigerant combination mainly used is activated carbon ammonia, activated carbon- methanol and silica gel- water. The adsorbent refrigerant combination for engine exhaust heated system used by the researchers was activated carbon and ammonia. The adsorption system studied in the literature review gave a specific cooling power in the range 500 to 800 W per kg of adsorbent. The COP of the presented system is in the range of 0.2 to 0.5. The adsorption systems studied in the literature uses minimum 6 to 8 valves and hence complex in operation.

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3. Conclusion

This thesis proposes an innovative, compact, and improved adsorption refrigeration system design, powered by engine exhaust heat. The system, which has been developed during the course of the presented research work, makes the following contributions in the field of adsorption refrigeration technology and automobile air conditioning using engine exhaust. 1. An innovative adsorption refrigeration system powered by heat with minimum of two control valves is being developed by using superconductivity materials for the manufacturing of valves and also by changing the design parameters. This is analysed using Computational Fluid Dynamics. 2. An adsorption heat exchanger, which is compact approximately by 20% from the existing systems is developed. 3. More heat transfer area is achieved by changing the following parameters of the valve - the diameter, pitch values and inclination of the position of valves. 4. An environment friendly cooling system has been designed that does not rely on engine power, and thus helps in reducing resulting pollution as well as global warming. The Global Warming Potential (GWP) of ammonia is zero. 5. A cooling system has been developed that does not use CFC refrigerant, and thus protect ozone layers over the atmosphere. 6. The designed system minimizes the chances of refrigerant leakages, which is a major problem associated with ammonia adsorption refrigeration system. A system has been developed with the external surfaces of the valve arrangement passing with cooling fluids to minimize the heat input in the system thereby reducing the leakage of the system. 7. The developed adsorption system design provides platform for further development of adsorption refrigeration technology and for waste heat operated cooling systems. The research work for truck cabin cooling is one amongst the many such possible applications of developed technology.

3.1 Scope for future work

Adsorption refrigeration is an emerging technology and can replace vapor compression refrigeration and vapor absorption refrigeration research work can further be carried out to develop this technology further and present it as a potential alternative. Waste heat potential can be tapped and can assist for energy conservation. 1. The system design has been presented for a cooling capacity of 1 TR. The system can be developed and tested on a 100 kW engine to verify its performance with automatic valves and water as secondary refrigerant. And also fitting the system on trucks, paramedical vehicles etc. can be considered. 2. The proposed system can operate with multiple heat sources like solar energy or other waste heat sources. Such systems can be developed and tested. 3. Research can be done with other working pairs of adsorbent and refrigerant like R 134a and activated carbon, methanol and activated carbon etc. and their performances can be compared.

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