The rack backdoor cooling is an efficient way for server temperature contral and energy saving. In this paper, a coupled model of multiple-heat-sources model of 42U rack and mathematical models of the microchannel vertical evaporator are established and mathematical models are verified by experimental results. Inhomogeneous air temperature and flow velocity data after being heated by servers and before coming in evaporator can be obtained with the rack model. It is discovered that the maximum temperature difference is up to 9.5℃ under uniform load conditions, and 15℃ under non-uniform load conditions. When upper, middle and lower parts of the rack are set to zero load, the overall air-side outlet temperature difference can reach 6.5℃, 8℃ and 8.5℃ separately. Compared with full load working, the air temperature uniformity of evaporator outlet can be improved when some severs are standby, and it improves with the height of inactive servers. These simulation results can provide an effective guidance for the optimization design and application of the micro-channel vertical evaporator in the rack backdoor cooling.
Keywords data center, backdoor cooling, microchannel, vertical tube evaporator, non-uniform load conditions