Characterization of a Server Thermal Mass Using Experimental Measurements

The inevitable increase in the heat dissipation of data center facilities is requiring more efficient approaches in the operation of a data center. Dynamic cooling has been proposed as the approach for enhancing the energy efficiency. Dynamic cooling involves close monitoring of the data center environment with time, using sensors, and taking real time decisions on allocating the cooling resources based on the location of hotspots and concentration of workloads. In order to address this approach, knowing the time it takes for a facility to reach steady state after any variation is crucial for ensuring safe operation of the electronic equipment at all times, and it is a function of thermal mass. The thermal mass of an object is the amount of mass capable of withholding heat, and the time it takes to dissipate that heat into the environment is a function of the material properties. In this study, we use a typical 2U server and explain a procedure in obtaining its thermal mass. The server is operated at different controlled power levels while measurements of fans speed, component temperatures, and inlet and outlet temperatures are taken with time. For the first set of experiments, the server is kept inside a chamber and for the second set it is kept in open space. Ultimately the experimental measurements obtained will be used to obtain a compact model to approximate thermal mass of different servers.