Performance Analysis Of An Hybrid Indirect Evaporative Cooling-Variable Frequency Vapor Compression Air Conditioning System

Compared with vapor compression refrigeration system,evaporative cooling technology has huge potential in the field of refrigeration and air conditioning with the advantages of energy saving,economy,environmental protection and health.However,the performance of evaporative cooling technology depends on the environmental climate,which limits the scope of application,especially in hot and humid areas.Therefore,exploring a hybrid air conditioning system combining evaporative cooling technology with traditional vapor compression refrigeration technology to integrate the advantages of the two technologies is of great significance to further improve the performance of air conditioning systems and achieve the purpose of energy conservation and emission reduction.In this paper,a hybrid IEC-VCR system is proposed by combining indirect evaporative cooling technology with vapor compression refrigeration technology.Firstly,the steady-state simulation model of the IEC-VCR system is established,and the influences of compressor operating frequency and inlet air parameters(temperature,relative humidity,mass flow)on the main performance parameters(COP and air outlet temperature)of the hybrid system are theoretically analyzed.Furthermore,the performance of the hybrid system is compared with a standalone indirect evaporative cooling system(IEC)and a standalone variable frequency vapor compression refrigeration system(SVCR)under different environmental conditions.Finally,When the air supply temperature of the system is fixed by adjusting the operating frequency of the compressor,the performance of the IEC-VCR and the SVCR systems under different inlet air temperature and humidity are studied.The results show that the performance of IEC-VCR system is better than SVCR system in the given range of air conditions.When the outdoor air temperature is higher and relative humidity is lower,the performance improvement is better.Furthermore,the air flow mode and air flow rate allocation of the IEC-VCR system are further studied and optimized.In the IEC-VCR system,the secondary air can be mixed by indoor return air,primary air return air and outdoor fresh air in different proportions,and the air entering the condenser can be mixed by outdoor fresh air and secondary air outlet of indirect evaporative cooler in different proportions.Through the theoretical optimization,it is found that the performance of the IEC-VCR system can be improved by optimizing the air flow rate allocations ratios for the secondary air and the cooling air entering the condenser.In addition,an experimental facility of the IEC-VCR system is built.The test-bed is mainly composed of two subsystems in series: indirect evaporative cooler and variable frequency vapor compression refrigeration system.The influences of compressor operating frequency and inlet air parameters(temperature,relative humidity,mass flow)on system performance(COP and air outlet temperature)are experimentally studied.The error between experimental data and theoretical data is compared and analyzed to verify the reliability of the model.It is apparent that the air outlet temperature calculated by the numerical method agrees well with the measured values with a maximum discrepancy of 18.6%,and the relative error of 96.53% data is within 20%;the maximum relative error of COP is 15.93%,and the relative error of 99%data is within 15%.