Study On Characteristics Of Dual-sources Activated Absorption-compression Combined Refrigeration Cycle

The development of the economy promotes the increase of car ownership,which leads to the increase of oil demand year by year and the increase of greenhouse gas and particles to the environment.Therefore,the energy saving and emission reduction of automobile has become one of the focuses of various countries.At present,the effective thermal efficiency of the engine is between 35 to 40%,and the remaining 60 to 65%of the heat is mainly discharged into the atmosphere through exhaust and engine coolant.With the gradual reduction of traditional energy,how to efficiently recover and utilize engine waste heat is one of the focuses of many scholars and research institutions.This paper proposes a dual-sources activated absorption-compression combined refrigeration cycle(ACCRC),in which 2-chloro-1,1,1,2,-tetrafluoroethane-N,N-dime-thylacetamide(R124-DMAC)is used as the working pair.And the refrigeration cycle uses engine exhaust and coolant as the driving heat source.Under the design conditions(the cooling capacity is 30 kW,evaporation temperature is 5℃,condensation temperature is 40℃,exhaust temperature is 300℃,coolant temperature is 90℃,exhaust flow rate is 0.25 kg/s,coolant flow rate is 0.34 kg/s,solution pump mass flow rate is 0.461 kg/s),the thermodynamic cycle calculation and the design calculation of heat exchange equipment are carried out for the cycle.The multi-head spiral coil generator and air-cooled vertical tube bubble absorber are proposed.The characteristics of the refrigeration cycle are analyzed by changing the generation pressure,generation temperature,absorption temperature and condensation temperature.Considering that the heat source of the refrigeration system is greatly affected by the operating conditions of the vehicle,it is necessary to conduct quantitative analysis on the temperature and flow of the engine exhaust gas,as well as the temperature and flow of the coolant.In this paper,the parameter models of engine exhaust and coolant are analyzed,and the steady-state models of engine exhaust and coolant are compiled.On this basis,the steady-state model of absorption compression hybrid refrigeration cycle driven by double heat sources is established.The circulation characteristics of the dual-heat source driven absorption-compression hybrid refrigeration system are analyzed,and the influences of exhaust gas temperature and flow rate,coolant temperature and flow rate,condensation temperature,evaporation temperature,solution pump flow rate and ambient temperature on the characteristics of the dual-heat source driven absorption-compression hybrid refrigeration system are further studied.Simulation results indicated the cycle had a high performance coefficient generally exceeding 10 and low circulation ratio lower than 3.6.Further investigations showed a high temperature and flow rate of exhaust gas were beneficial for the promotion of cooling capacity and coefficient of performance.A high temperature and flow rate of cooling liquids could increase cooling capacity.but would reduce the performance coefficient.In addition,the simulation results showed cooling capacity reduced from 31.52 to 24.76 kW and coefficient of performance of ACCRC(COPACCRC)also had an obvious decrease from 19.33 to 12.21 with the rise of ambient temperature from 30 to 38℃.