The Characterization Of The Absorption-compression Hybrid Refrigeration Cycle

At present, the traditional automotive cooling system uses the compression refrigeration that consumes engine power, causing a great waste of energy. Recycling vehicle exhaust waste heat to drive absorption chiller to replace traditional compression refrigeration way can achieve the purpose of energy saving. Since using the refrigeration system driven by waste heat simply cannot meet the cooling load needs of the car in any driving conditions, a novel absorption-compression hybrid refrigeration cycle (ACHRC) driven by waste heat and power from vehicle engines was proposed. It was based on the behaviors of the operation characteristics of the absorption refrigeration driven by the waste heat from automobile and the technical requirements for the vehicle cooling system.This paper taken Golden Dragon passenger as an example and calculate the cooling load of the bus air-conditioning. It is30kW. According to the air conditioning load for a bus, the thermal calculation of the ACHRC in which R124-DMAC is used as working fluid had been done under the given conditions. The given conditions are that the temperatures of cooling air, condensation and evaporation are35℃,55℃and3℃respectively and the bus air conditioning load is30kW. The loading characteristics and operation parameters of the absorption and compression refrigeration sub-systems which vary with the generator load ratio had been analyzed under two control strategies for the solution pump. The obtained results of two sub-cycles are used as the system equipment design or selection basis.This paper defined the coefficient of performance and generator load ratio and made a quantitative analysis on the parameters of engine exhaust emissions at different speed. Under two solution pump control strategies, when reaching the goal of the compressor minimum power consumption, it was analyzed that variation of the operating characteristics of the hybrid refrigeration cycle, the load characteristics of various devices and operating parameters under different generator load ratio or ambient temperatures.The results show that when the generator load ratio is100%, the cooling load of the bus air-conditioning could be solely provided by the absorption refrigeration sub-cycle at design conditions. At this time, the coefficient of performance of the hybrid refrigeration system reaches the maximum,14.85. When the compressor power consumption is0, the saved engine output power is also the largest. It is7.89%of rated output power. With the reduction of the generator load ratio, the cooling capacity of absorption refrigeration subsystem is not able to meet the bus air-conditioning required, and the insufficient part is provided by the compression refrigeration subsystem.In addition, the changes in ambient temperature will affect the absorption-compression hybrid refrigeration cycle. The results showed that under the direct air-cooled conditions, the effect of high ambient temperature is poor. At generator load ratio of100%, when the ambient temperature increased from35℃to40℃, the cooling capacity of absorption refrigeration sub-cycle is about to drop by half. When the ambient temperature is reduced, the cooling capacity of absorption refrigeration sub-cycle increases with the ambient temperature is reduced.