Theoretical And Experimental Study On A Novel Dew Point Evaporative Cooling System

Evaporative cooling technology is a renewable and sustainable cooling technology,which offers many outstanding characteristics, including: energy savings and environmental protection. Improving the energy efficiency of the evaporative cooling system is the focus of the research. In view of the problems in traditional evaporative cooling systems, this study presents a novel dew point evaporative cooling system based on the cross flow dew point design.The main research tasks include:(1) The exergy analysis models of the traditional evaporative cooling system and the new dew point evaporative cooling system are tested and compared. Using typical operating conditions, the exergy efficiency of the two systems is calculated and analyzed. The results show that the exergy efficiency of the new system is increased by about 2%,and the effective output exergy is increased by 16.9%. In addition, the temperature and moisture content of the air supply is significantly lower than the traditional evaporative cooling system, which greatly enhances the new system's ability to bear heat and moisture loads.(2) The single-stage cross flow dew point evaporative cooler and the new three-stage dew point evaporative cooling system are tested side by side in identical conditions. According to the variation of air wet bulb temperatures in our country, eight typical climate conditions are simulated in the laboratory. The performance of the cooling systems in these eight conditions are analyzed to help identify the factors that affect cooling efficiency.(3) The mathematical models of the single-stage cross flow dew point evaporative cooler and the new three-stage dew point evaporative cooling system are established.The influences of the structure parameters, such as channel width, channel length, open porosity, ratio of heat transfer area, and air state parameters on the wet bulb efficiency,dew point efficiency and cooling capacity are calculated and analyzed. The optimized matching of structural parameters and operating parameters of the two systems is then realized. With the optimal structure parameters and operating parameters, the wet bulb efficiency of the two systems are increased by 122% and 134% respectively.(4) The cooling performance of the improved cross flow dew point indirect evaporative cooler and the traditional plate type indirect evaporative cooler is also evaluated. Under typical operating conditions, when two coolers are used alone and the air volume is relatively small, compared with the traditional plate type cooler, the maximum cooling capacity of the dew point cooler increased by 20.1%; when the two coolers are used in the first stage of the three stage evaporative cooling system and the air volume is large, compared with the dew point cooler, the maximum cooling capacity of the traditional plate type cooler increased by 9.7%; when the two coolers are used in the second stage of the three stage evaporative cooling system, compared with the traditional plate type cooler, the maximum cooling capacity of the dew point cooler increased by 42.4%. In addition, these experiments revealed weaknesses in areas of internal heat and mass transfer, and gave rise to ideas to further improve the cooling performance.