Simulation Study On Operation Performance Of Computer Room Temperature Control System Based On Non-uniform Environment Concept

In order to solve the problems of large energy consumption and poor cooling effect of data center air conditioning system,a computer room air conditioning system based on non-uniform environment concept was proposed.First of all,from the cold preparation level,the system combines evaporative cooling technology and power-type split heat pipe technology with vapor compression refrigeration technology,and can realize free switching between three operating modes according to different working conditions.Secondly,from the transmission and distribution level of the cold amount,the two-phase refrigerant is used as the brine carrier,and the carrier cooling density is effectively improved compared with the carrier coolant such as air and water,which is advantageous for improving the cooling and distribution efficiency.Finally,from the supply level of the cold quantity,the system uses the distributed cooling end to directly cool the electronic equipment inside the closed cabinet,which is beneficial to improve the accuracy and cooling effect of the system.The operating performance of the system is affected by many factors,in order to determine the main factors affecting system performance,and to study its impact law,firstly,structural parameters or performance parameters of system components including evaporators,condensers,compressors,refrigerant pumps,and electronic expansion valves were determined by design calculations.On this basis,according to the basic operation and control principle of the system,the mathematical models of the main components and systems are established.Finally,using the mathematical model,the effects of the environmental parameters(cabinet design temperature:inlet air temperature of the evaporator inside the cabinet),operating parameters(cabinet air volume and outdoor unit air volume),design and structural parameters(refrigerant charging rate,evaporator and condenser heat exchange area),cooling capacity and cooling unevenness on system performance under two operating modes were simulated.Based on this,the operating parameters under different conditions were optimized.The study found that as the cabinet design temperature increases,the compressor discharge temperature,the compressor frequency required by the system,or the refrigerant pump frequency(heat pipe mode)decrease,and the system COP increases.In addition,under the different working conditions,the optimal outdoor air volume and the optimal cabinet air volume make the system COP the largest.In the air-cooled heat pipe mode,as the liquid filling rate increases,the refrigerant pump frequency required by the system decreases,and the COP increases slowly.In the evaporative cooling vapor compression refrigeration mode,the refrigerant charging rate increases so that the compressor discharge temperature increases,the required compressor frequency decreases,and the system COP has a maximum value,thus,there is an optimum refrigerant charging rate.Finally,as the heat exchange area of the evaporator or the heat exchange area of the condenser increases,the compressor discharge temperature and the compressor frequency or refrigerant pump frequency required by the system decrease,and the system COP increases.By studying the effect of cooling unevenness on system performance,it is found that as the cooling unevenness increases,the compressor discharge temperature,the required frequency of compressor or refrigerant pump increases,the system COP decreases,and the rate of decline gradually increases.In addition,compared with the system performance under different cooling capacity conditions,the system’s optimal outdoor unit air volume and optimal cabinet air volume are reduced as the system cooling capacity decreases.In the evaporative cooling vapor compression refrigeration mode,the optimal refrigerant charging rate of the system also decreases with the decrease of the cooling capacity.Through optimization analysis,it is found that in the air-cooled heat pipe mode,when the outdoor temperature rises from 0℃ to 10℃,the optimal cabinet air volume,the optimal outdoor unit air volume and the required refrigerant pump frequency increase by 77.78%,30.77%and 33.00%,respectively.In the evaporative cooling vapor compression refrigeration mode,when the outdoor temperature is raised from 32℃ to 42℃,the optimal cabinet air volume is always 1100 m3/h,and the optimal outdoor unit air volume and system required compressor frequency are increased by 22.22% and 9.64%.