Research On Recycling And Utilization Of Regenerative Exhaust Air In Desiccant Wheel Air Conditioning System

Facing the combined challenges of environmental protection,energy saving and low carbon,the desiccant wheel air conditioning system has been widely concerned and studied because it can effectively use low-grade energy and use water as refrigerant.The desiccant wheel air conditioning system is divided into treatment air channel and regeneration air channel.The treated air is directly sent to the air conditioning room after dehumidification and cooling;After the regeneration of the wheel dehumidifier,the regenerated air is directly discharged to the outdoor.The regenerative air of the wheel dehumidification air conditioning system is high temperature and humidity air,which has high value of heat and humidity recovery.Therefore,this paper puts forward the recycling and utilization methods of regenerative exhaust air in the rotary dehumidification air conditioning system,and studies the recycling of the heat and humidity of the exhaust air in summer and the application of the regenerative exhaust air in dry air humidification in winter.The recycling and utilization method of the regenerative exhaust air in the desiccant wheel air conditioning system is proposed.the feasibility of the recycling of the heat and humidity of the regenerative exhaust air in summer and the humidification of the regenerative exhaust air in winter is analyzed by using the thermodynamic theory,and the thermodynamic theoretical model of the system components is established.The heat and moisture recovery experiment of the regenerative exhaust air in summer is carried out.The relationship between the temperature and humidity of the regenerative exhaust air and the regenerative temperature is tested.the results show that the regenerative exhaust air temperature increases with the increase of the regenerative temperature.When the regenerative exhaust air temperature is 120℃,the exhaust air temperature is 50.1℃ the temperature of regeneration exhaust air is 120℃,and the moisture content of exhaust air is 39.1 g/kg,which indicates that the regeneration exhaust air has high value of heat recovery and moisture recovery.The research on heat recovery performance shows that the heat and humidity recovery device can recover the heat of the exhaust air to prepare low-temperature domestic hot water;when the regeneration temperature is 120℃,the condensate water can be recovered from the exhaust air by 4.2～5.6 kg/h;and the condensate water quality is detected,and the water quality detection results are:pH is 7.04,conductivity is 24.7 μs/cm.the exhaust air intake can be used as make-up water or domestic water for chillers,and the temperature of exhaust air after intake is lower,which can precooling the runner dehumidification air conditioning system.The performance of regenerative exhaust air recovery in summer is studied by dynamic simulation.The simulation model is established by TRNSYS,and the dynamic hourly simulation is carried out from June 1 to September 30 in typical year of Xi’an.The results show that the proposed system can provide a comfortable environment in summer,with the supply air temperature range of 18.1～23.3℃;29314 kg of condensate water can be recovered from the regenerative exhaust air in the whole refrigeration season;the COP of solar energy as the regenerative energy of the rotary dehumidifier varies from 1.0 to 2.73 in 81%of the hours,providing about 81051.7 MJ energy,saving about 39.8%,and reducing CO2 emissions by 20501 kg.The winter mode of the dehumidification air conditioning system is proposed by using the humidification performance of the regeneration air exhaust in winter.The solar energy is used for heating and the exhaust air of the desiccant wheel is humidified to improve the indoor thermal comfort.TRNSYS is used to simulate Xi’an from November 15 of the typical year to March 15 of the next year.The simulation results show that the supply air temperature of the system is 25.2～35.4℃,and the humidity content of the supply air is 8.0～12.1 g/kg.In the whole heating season,the solar energy can provide 56.6%of the heat supply;there is an optimal flow ratio of 0.57,which makes the humidification efficiency of the desiccant wheel maximum.The humidification efficiency is 1.4～1.6 when the system adopts full exhaust mode,and decreases gradually when a certain proportion of fresh air is added.In practical application,all the exhaust air should be used in the air conditioning system.When the air volume is insufficient,fresh air can be introduced to supplement.