ASHRAE - American Society of Heating@ Refrigerating and Air-Conditioning Engineers@ Inc.
Scope
Abstract During power outages servers in the data centers are generally powered by uninterruptible power supplies (UPS). At the same time the sources for active cooling such as CRACs@ CRAHs@ and chillers stop operating for a period until powered by alternate power sources. During this period servers continue to generate heat without any active cooling. This results in increase in the room air temperature within a short period that can be detrimental to the servers. This paper@ with the help of a mathematical model@ indicates that the rate of heating of a data center can start initially at a certain maximum level@ and can then gradually reduce to a certain minimum level@ which is the lowest possible rate of heating that a data center can attain. The rate of such exponential decay is a function of the time constant@ which is the characteristic of a data center design and layout. The time constant depends on the heat capacity ratio and the specific surface area of racks in a data center. This paper analyzes various factors that affect these parameters and demonstrates how the time constant can be employed as a matrix to compare the thermal performance of data centers during the power outage period.