Second International Conference on Emerging Trends in Engineering and Technology, ICETET-09
Adsorption Air-Conditioning (AdAC) for Automobiles Using Waste Heat Recovered from Exhaust Gases A C Deshpande, R M Pillai
Abstract- According to a cautious estimate, approximately 10% of the energy available at the crankshaft in a diesel operated vehicle is used for operating the compressor of the vehicle’s air-conditioning system. This is a huge loss if one takes into account the fact that the thermal efficiencies of most diesel operated vehicles range from 2030% when in pristine condition. The bottom line is that a great deal of diesel is consumed to generate electricity. In addition to this, alternating current via an alternator is necessary for the operation of the conventional a/c system. The refrigerant, usually R12 or R22 leaks easily. Being a secondary refrigerant, it is also harmful to the environment. Conventional air conditioning systems are also questioned due to the ODP (ozone depletion potential) and GWP (global warming potential) caused by the CFCs or HCFCs. Increasing recognition of environmental problems associated with CFCs and HCFCs has opened favourable opportunities for the development of green air conditioning technologies. This project report presents a revolutionary silica gel – water adsorption system for air conditioning in automobiles. The cooling effect is achieved by recovering waste thermal energy from the exhaust gases. The system is cheap and easy to fabricate. The refrigerant, being water, is environment friendly. The report provides the details regarding the construction of a prototype fabricated on this technology, by the co-authors. The design of the generator, which is the focal part of the system, is novel yet simple. The experimental results obtained, while conducting tests on a four stroke diesel engine from Mahindra have been included.
produced by the subcooling of the refrigerant in the condenser. Conventional vapor compression air conditioning systems, however, have a number of shortcomings which make it unviable and there is a need for a better alternative. One of the alternatives being developed at present is adsorption air conditioning. Adsorption is the phenomenon in which, the liquid molecules (adsorbent) in the adsorbing pair gets deposited on the solid (adsorbate) surface. This is an exothermic process. For example, the silica gel used in many desiccating applications acts as an adsorbate, which adsorbs the water molecules on its surface. Adsorption air conditioning uses the process of adsorption-desorption and the thermodynamics associated with it to create the air conditioning cycle. We selected the adsorption air conditioning system to be the topic of our final year project. We intended to construct a working prototype of a simple adsorption air conditioning system. Our aim was to construct a model at minimum cost using available tools and scrap materials. Our choice was based on two reasons; the first being the wide scope of the concept. Our system was to provide cooling effect for automobiles using the heat generated in exhaust gases. This could, however, be easily transposed to a variety of similar systems. We could, theoretically, use any heat source to provide cooling for any cooling space. An example that comes to mind is the central air conditioning of any home using solar energy. If an affordable system of this type were to be built, it would have tremendous scope for a place like Shegaon where our engineering college was located. It would enable even the underprivileged to own an air conditioning system and survive the treacherous summers of Shegaon. In short, the scope for such a system is unimaginable. The second reason was the exciting field which we wanted to be a part of. The ongoing research in the field of adsorption systems was outstanding and the field being nascent was poised for spectacular growth. We gleaned a lot of information from research papers and journals published as recently as early 2009. The relevance of the project in today’s world is also magnified as a result of the eco conscious age we are entering. As a consequence of the Kyoto protocol further
I. INTRODUCTION The conventional air conditioning system uses a compressor to deliver the v...