Experimental evaluations and numerical analyses of a dual-loop automotive air-conditioning system

A dual-loop automotive air-conditioning system is studied experimentally and numerically in this dissertation. The objective on the first part of the research project was to design, fabricate and implement experiments on a dual-loop air-conditioning system used in a conventional car. In the second step, analytical and numerical analyses were done on the experimental data to quantify the performance of the components and system.; Most cars use separate cooling and heating systems to control cabin temperature. Since the heating system uses the heat supplied from the engine, there is still a continuing problem with the heating systems in most cars because it takes some time for the engine to warm up, especially in cold seasons. This warm up period, depending on the car, size and manufacturer, can take from 3 to 10 minutes in a cold ambient condition of -10°C. On the other hand, the cooling system which normally uses a vapor compression refrigeration cycle is effective right after starting the engine in warm climates. So a dual heating and cooling system design, which can work in both cooling and heating modes, may overcome this problem and make the air conditioning system more comfortable and efficient. Researching and developing such a dual system is the main objective of this study.; The air conditioning system is basically a refrigeration cycle in which a refrigerant like R134a is circulated through a loop by a compressor. This loop removes heat from the passenger cabin using an evaporator, and rejects heat to the surroundings using a condenser. Furthermore, the heat pump is a system that is utilized to heat the passenger cabin in cold conditions. This is mainly the same system as the refrigeration loop but with an opposite direction of energy flow. The heat rejected from the condenser is used to warm up the cabin and the cold ambient air heats the evaporator depending on the pressure and temperature of refrigerant. The most important benefit of using this system for heating the cabin in cold climates is to reduce the time required to warm the cabin after starting the engine. This system of course uses part of the engine power to run the compressor of the refrigeration loop and the liquid pump used for circulating the warm water from the radiator consumes a small fraction of engine power as well. The integrated system would include both the air conditioning and heat pump modes, so that by switching some valves these two modes can be switched for appropriate conditions.