Performance measurements of a forced convection air-cooled rack

Abstract

The forced air cooling rack, Tower of Cool (TOC) for the cooling of the racks in the data center was experimentally investigated and compared to a conventional raised floor cooling system (RFCS). The heat load was simulated with eleven 4U server chassis each fitted with inlet and outlet fans and an electric heater of 1 kW maximum heat output. The inlet and outlet air temperature distribution was measured over the entire front and back opening of the rack as well as the inlet and exhaust air temperatures. For the RFCS, the air flow is only established by the server fans, which contributes to the air stagnation at other air passages. This results in higher inlet air temperature to the servers at a higher position. For the TOC, the inlet air temperature profile is improved, especially at the higher positions by adding the air flow guide at the front door, the air flow streaming back door, and the outlet fans. Improved inlet air temperature profile contributes to 3 K lower and constant inlet air temperature as compared to those of the RFCS. The comparison of the temperature difference between the front and back planes proves that the TOC provides even air distribution along the server slots at a reduced air flow rate better than the RFCS. This reduces hot spots in the upper region occurring in the RFCS configuration. In the TOC, both front and back doors are equipped with mechanical solutions to evenly distribute the air flow to and from the servers, which provides better cold air distribution across the servers and along the servers to the components at reduced total air flow than the standard technology.