Design And Optimization Of Compound Absorption Refrigeration Cycle Driven By Gas Engine Exhaust

In the background of global energy shortage and greenhouse effect increasing,the CCHP system based on gas engine,which has a high primary energy ratio because of energy cascade utilization,has developt rapidly.The performance of the absorption chiller driven by the engine exhsust is very important to the efficiency of the whole CCHP.However,the absorption chiller adopted widely in the present CCHP could not recoverthe waste heat of the engine exhaust efficiently.Therefore,it‘s significant to design efficient absorption chiller which is suitbale to the gas engine exhaust characteristic.The key of efficient absoption refrigeration cycle construction is the high temperature exergy efficient transformation and the low temperature exergy cascade transformation.In this peper,for the high temperature exergy,two exergy transformation paths,which are 'Heat Exergy-Pressure Exergy-Cooling Exergy‘ and 'Heat Exergy-Power Exergy-Cooling Exergy‘ respectively,are proposed and used to design two corresponding compound absorption cycle.By the comparing the performance of the two cycles,the advantage of the 'Heat Exergy-Power Exergy-Cooling Exergy‘ path is confirmed.For the low temperature exergy,a good match between the exhaust temperature gradient characteristic and the generation temperature gradient characteristic within the bottom cycle is realized and this makes full and deep use of the low temperature heat of the exhaust.Finally,the compressor-assisted triple-effect absorption refrigeration cycle based on the heat and work couple between the power cycle and inverse cycle is finished by the organic combination of high temperature exergy transfoamation path and that of low temperature exergy.The compound cycle characteristic has been fully reasearched in detail according to the thermodynamics analysis method.The compound refrigeration cycle improves COP more than 10% while the maximum generation temperature is 50? lower than that of the traditional absorption cooling cycle at the condition of CR=2.2 and P_v?p1=6.3MPa.While the work and heat couple between the power cycle and inverse cycle makes the compound cycle getting excellent performance,it also results the limit compression ratio at certain deflation range,which means only the deflation range is not very large?smaller than 0.015?,could the maximum temperature of the compound cycle could be controlled under 165?to get rid of severe corrosion at high temperature.It proves the good performance of the compound cycle by comparing with the compressor-assisted absorption cycle and the multi-stage power cycle and uncovers the energy saving mechanism at the same time.The influence of gas engine operation condition on the compound cycle has been reasearched.It found that as the engine is in lower load?300k W?,which means the exhaust temperature decreases a lot and the ability to drive the compound cycle weakens,COP getting down rapidly and maximum temperature could not be controlled under 165? with the potential to high temperature corrison.The improvements on the bottom cycle has been made.When the bottom cycle is changed from series cycle to inverse series cycle,the maximum temperature doesn‘t decrease a lot as happening in the traditional triple-effect cycle because of the special low temperature heat casade driving structre in the compound cycle.However,the COP and cooling capacity are increased apparently and this suggests the adaptability to the engine low load of the compound cycle is strengthened.