Performance Research On The Fresh Air Handling Unit Used In Temperature-humidity Independent Control System

This paper proposed a novel fresh air handling unit(FAHU)which can be used in temperature and humidity independent control(THIC)air conditioning system.Further,the working principle of the unit has been detailedly illustrated.The FAHU consists of an air handling unit,a compressor,a heat exchanger outside and a throttling device.The air handling unit is composed of two heat exchangers which are directly cooling the fresh air.The air handling unit can achieve a variety of fresh air handling requirements under the whole year condition.Under cooling and dehumidification condition,this device can achieve two-stage cooling and dehumidification;thus,the coefficient of performance(COP)of refrigeration system could be improved.A steady-state numerical model of evaporator is established in order to investigate the influence on the area and COP under two-stage cooling condition.Based on Matlab,the design program and the simulation program of evaporator are established and compared with reference.The results showed that the accuracy of the simulation program meets the needs of practical engineering.Under the condition,which the low evaporation temperature is 1~5°C;the high evaporation temperature is 12~16°C and the medium temperature is 20~24°C,the results showed that the COP under two-stage cooling operation is 8.22%~23.13% higher than that under single-stage cooling operation;the areas of evaporator is 85.67%~174.55% of the areas under single-stage cooling operation.Under the same medium air temperature condition,the COP and area will be improved with the low or high evaporation temperature increased.Under the condition of steady low and high evaporation temperature,the COP and area will decrease with the medium air temperature increased.Taking Xi'an as an example,under the constant air volume and humidity condition,the simulation of fresh air handling unit has been conducted.The results showed that the COP of unit under two-stage cooling operation is 22.7%~24.9% higher than that under single-stage operation with average increase of 23.8%.Under the same two evaporation temperature and medium air temperature condition,the COP of system could be considered to be the function of ambient air dry bulb temperature.