Experimental Study On Performance Of Dehumidification And Reheat Composite System For Fresh Air Of Air Conditioning

In the field of air conditioning,cooling dehumidification,as an air conditioning dehumidification technology with high dehumidification efficiency,stable dehumidification performance and low initial investment and operation cost,is widely used in all walks of life^[1].However,in practical application,the temperature of air supply after air conditioning cooling and dehumidification is often low,and it is easy to cause the uneven temperature field of air supply and increase the discomfort of indoor personnel when directly entering the room^[2].In order to solve this kind of problem,it is necessary to reheat the air after dehumidification of heat exchanger,which will produce energy waste caused by the superposition of cooling capacity and heat.Therefore,this paper designs a dehumidification and reheat composite system,which can pre cool the fresh air with the cooling capacity of the dehumidified chilled water return water,and reheat the air supply with the heat after pre cooling.In this paper,the dehumidification and reheat composite system is analyzed firstly,combined with the characteristics of dehumidification and dehumidification of air conditioning system,in order to analyze the source of moisture load in the building space and the law of heat and humidity control,and master the heat exchange process,heat exchange characteristics and the thermal calculation method of heat exchanger.Combined with the above theoretical analysis content,this paper further designs the dehumidification and reheat composite system,analyzes its working principle and air treatment process.In order to master the performance of dehumidification and reheat composite system under the actual operating conditions,the air treatment device of dehumidification and reheat composite system is designed and calculated,and the main components such as heat exchanger and circulating water pump in the device are imported A dehumidification and reheat experiment prototype is made and an experiment platform is built.Finally,the enthalpy difference method is used to carry out the exploratory experimental research on the experimental prototype under the design conditions and various conditions,such as different face-to-face wind speed,chilled water outlet temperature,air inlet dry bulb temperature and air inlet moisture content.According to the state parameters of the experimental prototype inlet,fresh air/dehumidification/reheat heat exchanger outlet and water temperature,the change of the heat exchange of the system and each heat exchanger with the flow of the bypass water is obtained According to the trend law,the influence of bypass valve opening on dehumidification and reheat of the system is analyzed,and the feasibility of dehumidification and reheat composite system structure is verified.The experimental results show that:?1?When the bypass water flow is 0.9m3/h and the water flow speed is 1.41m/s,the unit can obtain the minimum value of system heat exchange and the maximum value of reheat dry bulb temperature.Under the design condition,compared with that without opening the bypass valve,the heat exchange rate of the system is reduced by 12.0%,the moisture content of the air after dehumidification is reduced by 0.58g/kg,and the dry bulb temperature of the reheat is increased by 5.94?.?2?When the bypass water flow is 1.2m3/h and the water flow speed is 1.88m/s,the unit can get the maximum reheat temperature difference of the reheat heat exchanger.Under the design condition,the unit can raise the temperature of the fresh air after dehumidification by7.4?.?3?With the increase of bypass water flow,the difference between fresh air heat exchange and reheat heat exchange is increasing.When the bypass water flow increases to1.2m3/h,increasing the bypass water flow has little effect on reheat heat exchange.?4?The higher air temperature and lower moisture content can be obtained by properly reducing the head-on wind speed;the higher air temperature can be obtained by properly increasing the water temperature difference between the inlet and the outlet of the chilled water;the lower moisture content can be obtained by properly reducing the outlet temperature of the chilled water;the higher air temperature can be obtained by properly increasing the air inlet dry bulb temperature and moisture content.The dehumidification and reheat composite system designed in this paper can reduce the energy consumption of refrigeration and the moisture content of the air outlet state point,realize the cascade utilization of the refrigeration water cooling capacity,and reduce the energy waste caused by the superposition of cooling capacity and heat.The research results can provide some reference for the determination of design parameters of dehumidification and reheat composite system,the correct selection and calculation of equipment,and the development and utilization of the unit.