This study focuses the effect of uneven loading on the flow distribution across the data racks subject to a raised flow simulated small data center. A total of 10 data racks having a total thermal power of 50 kW is investigated. Tests are conducted for both semi-enclosed and fully enclosed cold aisle. For the even power case, all the data racks are operated with 5 kW, and for uneven case, one side of the data racks contains 7.5 kW heat generation for each data rack and the other side of data racks is 2.5 kW. The tested flowrates are 2.4 CMS and 3.4 CMS, respectively. Yet both semi-enclosed and fully enclosed cold aisle are tested in this study. It is found that for a higher supply volumetric flowrate of 3.4 or 2.4 CMS, the effect of maldistribution for even power case is rather small for the case of uniform heating load. Conversely, for semi-enclosed cold aisle, load, the difference in air volumetric flowrate on both sides has increased significantly, the hotter racks contain higher flowrate. The flow mal-distribution accounts for 6% at a flowrate of 3.4 CMS, and the difference is amplified to 12% for a smaller air flowrate of 2.4 CMS. For the fully enclosed cold aisle at a higher flowrate of 3.4 CMS subject to uneven heating load, the flow mal-distribution in both sides is insignificant. However, mal-distribution for uneven heating load may occur when the supplied flowrate is reduced to 2.4 CMS for the fully enclosed arrangement.

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