Research On Air Flow Organization Simulation Of Data Center With Rack Air-Conditioning

With the development of Internet technology,the energy consumption in data centers is increasing rapidly,which poses a greater challenge to the cooling system in data centers.Now three kinds of cooling solutions in date centers could be summarized: the room-level cooling program represented by accurate air-conditioned floor air system;the line-level cooling program represented by inter-row air-conditions system,and the cabinet-level refrigeration program represented by rack air-conditioning system.Among them,the cabinet-level cooling program has been widely installed due to the short distance of air supply,high cooling utilization,easy to plan and other features.The author Focused on a kind of rack air-conditioner designed by one company,a detailed calculation model was established and its operation in the cabinet was simulated in this paper.The numerical simulation results revealed that the air temperature of the rack air-conditioner was too high,which was up to 53.6 ?.Based on the analysis,the major causation could be attributed to the unreasonable relative position of the return air inlet and the heat exchanger in the rack air-conditioner,resulted in inhomogeneous cooling air volume inside the heat exchanger.Specifically,the cooling volume was too large at the back of the heat exchanger,however,the cooling volume at the side of the heat exchanger was too small,thus the cooling efficiency of the heat exchanger was impacted,eventually leading to temperature of rack air-conditioner was too high.Moreover,for the problem of inhomogeneous distribution of air volume in the heat exchanger of the rack air-conditioner,two kinds of schemes,installing a return air inlet on the side of the rack air-conditioner and replacing the L-type heat exchanger with a V-type heat exchanger,were proposed.Simulation studies found that both of these optimization schemes were able to solve the problem of inhomogeneous distribution of air volume in the heat exchanger.Once these optimizations had been taken,the air temperature in the rack air-conditioning was decreased by nearly 64.5%.The server in the cabinet was in a reasonable operating environment.Finally,the air-conditioner model optimized by the air return was used to simulate and analyze the influence of the cabinet blind plate and the relative position of the rack air-conditioner in the cabinet on the operation performance.(1)The installation of the blind plate could prevent the emitted hot air to reflow into the inlet of server,avoiding the mixing of hot and cold air.The IOM index could be used to evaluate the thermal environment inside the cabinet.The calculation showed that the IOM of the cabinet with the blind plate was much lower than the value of cabinet without the blind board.(2)If the inlet air area in the cabinet was too small(such as simulated working condition A),the inlet air volume of the lower server would be small and the exhaust air temperature could be high.If the inlet air area in the middle and upper server was large,the exhaust air temperature would be low.If the inlet air area in the cabinet was too large(such as simulated working condition D),the lower part of the server would have a larger air volume and a low exhaust temperature;in the upper and middle part of the server,the inlet air volume would be small,exhaust temperature would be high.(3)If the air return area in the cabinet was too small(such as simulated working condition D),the return air volume at the air return side of the air conditioner would be larger,return air volume at the rear air return port would be smaller,the air volume of the heat exchanger would not be uniform,which further caused the decreased efficiency of heat exchanger and a emitted high exhaust air temperature.(4)Placing rack air-conditioner too closed to the front and rear panels of the cabinet would result in increased airflow loop impedance,increased fan pressure drop,reduced air volume,and increased fan energy consumption.Compared with simulated working conditions A and D,energy consumptions of the fan are diminished by 27.4% in simulated working conditions B and C.