Performance Study Of Desiccant Wheel Evaporative Cooling Air Conditioning System

Evaporative cooling air-conditione relies on the "wet and dry bulb temperature difference"of the ambient air as the driving potential to generate cooling,which is a low-carbon green renewable energy air-conditioner.However,evaporative cooled air conditioners are limited by the wet bulb temperature and dew point temperature of the ambient air.A desiccant wheel evaporative cooling air conditioning system coupled by solid dehumidification and evaporative cooling is proposed.The system first reduces the wet bulb temperature of the ambient air through desiccant wheel air conditioning system,and then uses evaporative cooling technology to achieve cooling,and the system can be driven by low-grade thermal energy to prepare chilled air and chilled water in hot and humid regions.The specific study contents and results are as follows:The desiccant wheel evaporative cooling air conditioning system is proposed.The system can prepare chilled air and chilled water at the same time,the chilled air is sent to the room as fresh air,and the chilled water is supplied to the dry cooling terminal.Theoretical analysis of the thermodynamic process of the system and system’s exergy performance were performed.The study shows that compared with the traditional conventional desiccant wheel air conditioning system,the system regenerates 1.14 kW of heat exergy,which is 20.3%lower;and 0.35 kW of cold exergy,which is 18.6%lower;the system’s exergy efficiency is 78.4%,which is 34.2%higher,indicating that the desiccant wheel evaporative cooling air conditioning system has higher thermal perfection.The experimental platform of desiccantwheel evaporative cooling air conditioning system was designed and established,and the operational performance of the system was studied.The result shows that when the air-to-water ratio is 1.40,the temperature of both chilled air and chilled water prepared by the system reaches the lowest value of 17.2℃ and 15.4℃,respectively,with a thermal coefficient of performance of 1.51.The applicability of the system applied to three typical regions was investigated,and the result shows that the regeneration temperature of the system is higher than 60℃ in the moderate temperature and humidity regions,and the regeneration temperature is higher than 70℃ in the moderate temperature and high humidity regions and the high temperature and humidity regions.The desiccant wheel evaporative cooling air conditioning system is applied to an office building in Guangzhou,where the chilled air prepared by the system is sent into the room,and the chilled water is supplied to the dry cooling terminal of the room.The dynamic characteristics of the system were simulated and studied using TRNSYS software.The results showed that the system can maintain the temperature of the conditioned space at 25.6～26.8℃and the relative humidity at 57%～62%.Compared with dual cooling source air conditioning systems with independent temperature and humidity control,the average COP and average electricity saving rates of the system are 57.9%and 36.2%higher in a typical week,respectively,and can reduce carbon dioxide emissions by 45.9%in a typical month.The desiccant wheel evaporative cooling air conditioning system is applied to the data center.The system can realize three operation modes according to the meteorological parameters:all fresh air,evaporative cooling,and desiccant wheel evaporative cooling.The energy saving potential of data center air conditioning in Harbin,Beijing,Shanghai,Guangzhou and Guiyang is analyzed using TRNSYS software.The simulation results show that Harbin has the lowest PUE of 1.085;Beijing,Shanghai and Guiyang have similar PUE of 1.125,1.177 and 1.153,respectively;Guangzhou has the highest PUE of 1.237.Harbin has the lowest WUE of 0.282;Beijing and Guiyang have similar WUE of 0.336 and 0.376,respectively;Shanghai has a slightly higher WUE of 0.484;Guangzhou has the highest WUE of 0.661.Harbin has the lowest CUE of 0.0.271;Beijing and Guiyang have similar CUE of 0.318 and 0.351,respectively;Shanghai has a slightly higher CUE of 0.379;Guangzhou has the highest CUE of 0.450.