The leading knowledge exchange for Data Center, IT and Mission Critical professionals.
By Kishor Khankari, Ph.D.
Rack enclosures which host servers are not just the cabinets but an integral part of the airflow system of data centers. The cold air supplied from the air conditioning units must freely pass through the rack enclosures without any obstructions. Any excessive restrictions for the airflow offered by the rack enclosures not only adversely affect the cooling performance of the servers but can also disturb the overall balance of the entire airflow system. Air is the main carrier of heat in the data center. Therefore, proper management of cold and hot air streams in the data center is crucial for maintaining the acceptable levels of inlet air temperatures to the servers. However, just following the best practices for the data center design without proper considerations to the rack enclosures design is not sufficient
for obtaining the desired cooling performance of a data center.
Interactions with Server Fans
Servers are equipped with their own fans to move the air through the server chassis. Server manufacturers conduct bench tests to test the cooling performance of individual servers and determine the optimum airflow rates required for cooling the servers. These tests are generally conducted in an open environment with a single server without any surrounding obstructions. A typical rack enclosure seldom offers such an open environment without any obstructions. These obstructions in the path of air reduce the airflow rates through the server fans, which in turn, can reduce the cooling and increase the exit air temperature from the servers.
The extent of such a reduction in the fan performance depends on individual design of racks. Figure 1 illustrates the interaction between the server fan and the system resistance offered by the racks. The intersection between the system performance curve and the server fan performance curve determines the operating airflow rate for the server-rack system.
The dotted curve shown in this figure is the system curve for a single server during the bench test analysis. This figure further indicates, due to increased resistance to 27 airflow, the operating airflows through the server rack systems are lower than the desired airflow rate of the bench test of a single server. As the restrictions in the rack enclosures increase, the operating airflow through the servers decreases. More restrictive rack enclosure designs can reduce the operating airflow rates through the servers…
Read the Full Article
(You Must Be Logged In to Continue…)
BECOME A MEMBER or LOGIN for Full Access to Member Content and Information.
