Simulation And Parameter Analysis Of Water-side Free Cooling System In Data Center

At present,with the rapid development of the global information technology?IT?,the number of data centers is increasing rapidly,and the energy consumption occupies1.12¹.5%of total electricity consumption in the world.Also,manufacturing technology is progressing.Moore's law states that the number of electrical components doubles every 18 months.Although Dr.Moore does not refer to servers directly,the performance improvement of servers and related devices mostly followed this law in recent decades.It shows that the heating density of EIE equipment was over 120kW/m² in 2014.Due to the high energy consumption and high thermal density in the data center,the natural free cooling technology has already received extensive attentions and research in the data center field.It reduces the running time of the chiller through the use of the natural cold sources,and then greatly reduce the energy consumption of the cooling system in data center.This paper aims to simulate the natural water cooling system with the cooling tower as the core economizer in data center.The annual operating characteristics were studied in five typical climate regions of China,combining with micro channel heat pipe backplane.In addition,the key parameters of the cooling system were also analyzed.First,the simulation models of the water cooled natural cooling system were developed in the TRNSYS modeling platform.Therein the models of the chiller,cooling tower and computer room air handler?CRAH?were verified,with the average relative error at 4%,4.2%and 2.7%,respectively.Second,with the simulation platform,simulations were carried out with the terminal of CRAH and the micro channel heat pipe backplane in typical data center respectively.The results show that the total energy consumption of the cooling system decreases through the use of the microchannel backplane heat pipe by 3.0%³.8%,and the power usage efficiency?PUE?decreases by about 0.04,and the1230000¹470000 kWh electricity per year is reduced.Moreover,the temperature of the data room fluctuates smaller than that of CRAH,and the temperature field is more uniform,which is more suitable for data center.It also found that the heat transfer performance of the micro-channel backplane has a stronger adjustment ability than CRAH at the study of the maximum load change of Rack.The maximum load level is from 10kW to 7kW/Rack,7kW to 4kW/Rack,and the energy consumption of the terminal air conditioner reduces by 30%and 42.9%respectively.Finally,the key parameters of the natural water cooling data center were studied.The sensitivity study of the switching temperature shows that T_a1 and T_a2 will play a decisive role in the cooling tower free cooling system.A general design calculation method was proposed based on the performance formula of the cooling tower.The simulation case study shows that the proposed design method is more energy-efficient and reasonable.At the same time,the study of the number of cooling units of the cooling tower shows that increasing the number of cooling units is beneficial to reduce the approximation and enhance the heat transfer performance of the cooling tower,thus prolonging the use time of the natural cooling source,but the low approximation degree may lead to the low the server air supply temperature in the northern winter and even the condensation phenomenon,which refer to consider carefully in engineering practice.