Research On Design And Application Of Evaporative Cooling + Mechanical Refrigeration Combined Air-conditioning Unit

The future is an important period for the innovation and development of China’s air-conditioning technology.With the continuous development of China’s air-conditioning industry,evaporative cooling technology plays an important role in it.Evaporative cooling technology is an efficient,green,low-carbon,environmentally friendly,and energy-saving refrigeration technology that uses water as the refrigerant and uses the difference between the dry and wet bulb temperatures of the air to drive cooling.However,this technology is greatly affected by outdoor air weather factors.Combining it with mechanical refrigeration technology can make up for the shortcomings of using only one technology,which not only increases the scope of application of evaporative cooling technology but also improves the performance of mechanical refrigeration,which is of great significance for energy conservation and emission reduction.With the advent of the 5G era,China has vigorously built data center equipment rooms,but its high energy consumption is particularly prominent.Reducing data center energy consumption has become a global concern.Among the energy consumption of data centers,the energy consumption of refrigeration systems accounts for 38%.If data centers want to reduce carbon emissions,power consumption and energy costs,optimizing air conditioning systems must first be considered.There is a relatively lack of research on the organic combination of evaporative cooling technology and mechanical refrigeration technology and design analysis based on the actual working conditions of the data center.Especially,the operation mode between evaporative cooling and mechanical refrigeration is based on the characteristics of the data center’s continuous operation throughout the year The research on matching and switching needs to be broken.Based on the integrated unit of evaporative cooling and mechanical refrigeration used in data centers at home and abroad,this paper proposes and designs an experimental prototype of an integrated evaporative cooling+mechanical refrigeration integrated integrated air conditioning unit.Related studies have been conducted on energy efficiency.（1）The thermal environment and return air temperature and humidity required for data center IT equipment are introduced.Three types of energy-saving operation modes corresponding to the indirect evaporative cooling technology applied to the data center are introduced and the switching conditions of the operation modes are calculated and analyzed.An application example of different indirect evaporative cooling heat exchange cores in a data center is analyzed and the main performance parameters of related products of existing enterprises at home and abroad are analyzed.（2）Introduced the structure and design plan of the unit,carried out related design calculations and introduced the control logic of the unit,and provided the basis for the operation control scheme of similar units in the future.（3）Tested and analyzed the effects of evaporative cooling air conditioning units,dry air central air conditioning units,and plate-fin heat recovery new fan units in the data center.The test data of the three units were compared to determine the evaporative cooling+machinery.The practical application effect range of the refrigeration combined integrated air-conditioning unit,the application prospect of the unit is prospected,and the reference basis for the use and promotion of the unit is provided.The test results of the following three evaporative cooling air conditioning units are analyzed:（1）During the test of the evaporative cooling air conditioning unit in the data center,the dry-bulb temperature of the outdoor air was maintained at about 24.5℃,and the corresponding wet-bulb temperature was maintained at about 17.5.By adjusting the water-air ratio and the secondary air volume ratio,η_IECincreased from 62%to 77%.When the water-air ratio Y_nis 0.28 and the secondary air volume ratio X_mis 0.53,the maximum value ofη_IECappears to be 77%.（2）The dry air energy central air-conditioning unit simulated and analyzed the meteorological parameters corresponding to the three areas of dry area,medium humidity area and high humidity area.The test found that in a dry area,the water-to-air ratio Y_nwas0.3,and the maximum value ofη_IECwas 61%when the primary and secondary air volume ratio X_mwas 1.2;in the medium humidity area,the water and air ratio Y_nwas 0.3,and the secondary and primary air volume ratio X_mwas 1.2.The maximum value ofη_IECis 60%;the maximum value ofη_IECis 62%when the water-air ratio Y_nis 0.25 in the high humidity area and the primary air volume ratio X_mis 1.4.The operating principle of the indirect section of the dry air energy unit is that the high-level cold water produced by the upper evaporative cooler of the unit is passed into the lower coil of the unit to make indirect contact with the primary air,so the temperature drop and efficiency will be lower than the plate-fin indirect evaporation.Cool the heat exchange core.In addition,in the direct evaporative cooling part,it was found through testing that when the water-to-air ratio Y_nwas 0.38,η_DECreached the peak value and the direct cooling efficiency was 95%.（3）The test of the heat recovery new fan unit found that the air-to-air sensible heat exchange in the plate-fin heat exchange core of the unit caused a small temperature difference between indoor return air and outdoor fresh air,which was only about 4℃.During the process,the unit temperature drop was maintained at about 2.4°C,and the unit air-to-air heat transfer efficiency was about 60%.The heat exchange efficiency of the plate-fin indirect evaporative cooling heat exchange core of this unit can reach 70%to 75%,and the air-to-air sensible heat exchange efficiency of the plate-fin heat exchange core can reach 60%to 65%.The use of the combined evaporative cooling+mechanical refrigeration air-conditioning unit in dry areas-Dunhuang,medium humidity-Xi’an,high humidity area-Guangzhou,with three different climate characteristics has certain energy saving significance.In dry areas,the unit in Dunhuang hardly turns on the mechanical refrigeration section throughout the year,and the operating cost savings rate is as high as 78.3%,while in Xi’an in mid-humidity areas,the operating cost savings rate is 67.3%.The operating cost savings rate still reached 44.9%.A total of 117 figures,25 tables and 61 references are cited in the article.