Performance Comparison Research Of Evaporative Cooling Hybrid Air Conditioning System

The energy consumption of mechanical vapor compression air condition er(MVC)is large,and the evaporative cooling system consumes less energy,which can recycle the energy of return air.However,the use of evaporative cooling alone requires a lot of fresh air,which has a more obvious blowing sensation,and the fan produces a lot of noise,besides,it is difficult to meet indoor temperature and humidity when the outdoor humidity is high or the indoor load is large.The evaporative cooling system can be used to pre-cool the fresh air to reduce the load of the MVC,so as to achieve the purpose of saving energy without reducing comfort.Based on the methods of energy and exergy analysis,two traditional and two improved evaporative cooling fresh air conditioners(FAC)were compared.Moreover,each FAC can be combined with a MVC to form an evaporative cooling hybrid air conditioner(HAC),and the energy-saving performance of the four HACs were also analyzed and compared.The distributed-parameter models of the packed cooling tower and finned coils,and the correlation model of the MVC were established.The mathematical models of the packed cooling tower and finned coils were validated.The effect of four independent parameters(ambient temperature,humidity,fresh air flowrate and NTU)on the dew point efficiency,COP,exergy efficiency,exergy efficiency ratio and exergy loss of each FAC,and energy-saving rate of each HAC were studied.Then,TRNSYS was used to simulate the hourly load from June to August in summer,and the seasonal energy-saving potential of the four HAC in Turpan,which has a dry and hot climate,and Changsha,which has a hot and humid climate,was evaluated.The results show that with the increase of air temperature,the dew point efficiency,COP,the exergy efficiency and exergy efficiency ratio of each FAC increase.When the primary air is not humidified and condensed,the parameters of each FAC remain unchanged.When the primary air is humidified,as the amount of humidification decreases,the dew point efficiency,COP and exergy efficiency ratio of each FAC will decrease,and the exergy efficiency will increase.When the primary air is condensed,as the amount of condensation increases,the dew point efficiency of each FAC will decrease and the COP will increase,the exergy efficiency and the exergy efficiency ratio first increase and then decrease.With the increase of fresh air flowrate,the dew point efficiency,COP,the exergy efficiency and exergy efficiency ratio of each FAC decrease.With the increase of NTU,the dew point efficiency of each FAC increase s while the COP decreases,the exergy efficiency and exergy efficiency ratio first increase and then decrease(except for FAC-C).All HACs are suitable for hot-dry climate conditions,and their energy-saving rate first increases and then decreases with the increase of fresh air mass flow and NTU.In Turpan and Changsha,the seasonal energy-saving rates of HAC are 11.3%～32.8% and 2.33%～18.5%,respectively.The energy savings from June to August are 223 k W ·h～647k W·h and59.5k W·h～376k W·h,respectively.HAC has great energy-saving potential in hot-dry climate conditions.The HAC-D has the best energy-saving effect,which is the preferred.The comparative analysis of the energy-saving potential of the four schemes in different regions provides a reference for the engineering applications of evaporative cooling hybrid air conditioner.