Theoretical And Experimental Investigation On Absorption Compression Hybrid Refrigeration Driven By Waste Heat From Coach Engine

The demand for oil is increasing with the increase of car ownership in recent years, while large amounts of greenhouse gases and particles are discharged into environment. It is becoming a topic of concern for automobile energy saving in many countries, especial for China, the improvement of vehicle fuel efficiency and reducing emissions will be paid more attention. In addition, the vehicle engine usually have an average of35%～40%thermal efficiency, and the remaining waste heat of fuel combustion is discharged in the form of waste heat. Utilization of the waste heat from vehicle engine to drive the refrigeration system is a good automotive energy conservation program, and it is especially concerned by scholars and research institute in recent years.Based on that, a new absorption/compression hybrid refrigeration cycle driven by exhaust gases from vehicle engine is proposed for the first time, using HCFC124-DMAC as the working fluid. The new hybrid refrigeration cycle not only use effectively the engine waste heat,but will greatly reduce the car’s fuel consumption and reduce emissions. Further, the control strategies of the new cycle is proposed, when it is practically applied in vehicle air conditioning.The thermodynamic calculation of the new hybrid refrigeration and the design of the system are investigated further, especial on the design of spiral coil generator, used to recovered the exhaust waste heat. Further, the heat transfer model in the generator is built to solve the heat transfer between exhaust gases and working fluids. In addition, the water cooling device is not arranged easily in vehicle refrigeration system, and the falling film absorption has a bad effect in vehicle because of the vehicle usually running in the status of bumps, changing speed,turning direction and so on. On the basis of this, an air-cooled vertical tube bubble absorbing way is proposed and utilized on the vehicle absorption system, and further, a detailed design of the bubble absorber is made.The characteristic of the exhaust waste parameters from engine changing with the vehicle running in different status requires quantitative calculation for the exhaust gases parameters, including the exhaust temperature and flow rate. Based on this, the engine exhaust parameters model is built by analyzing the previous proposed waste heat parameters. Further coupling the vehicle running equations, and the exhaust gas temperature and exhaust flow are obtained under different driving speeds. The waste heat absorption/compression hybrid refrigeration system were simulated under the control strategy of constant solution pump flow rate. Calculation results show that when the vehicle speed is higher than100km·h-1, the waste heat absorption refrigeration sub-cycle can meet the30kW air conditioning load of the passengers car; whereas when the speed is below40km·h-1, the absorption refrigeration cycle has no cooling effect, and the air conditioning cooling load is provided by the compression refrigeration sub-cycle; and when the speed are between40km·h-1～100km·h-1, absorption refrigeration sub-cycle combining together the compression refrigeration sub-cycle work for meeting the cooling remand of theTo verifying the feasibility of absorption/compression refrigeration cycle utilized on vehicle air conditioning, the absorption/compression refrigeration cycle hybrid experimental apparatus are built based on the previous thermodynamic calculations. Further, the working characteristics of the absorption refrigeration cycle and absorption/compression hybrid refrigeration cycle are tested under different heating temperature and pump flow rate. Result shows the COP of the absorption refrigeration cycle can reach0.542; the high pressure of ACHRC is higher than that of ARSC,while the low pressure of ACHRC is lower than that of ARSC.