"APC Uses Airflow Simulation to Solve Data Center Cooling Problem", Customer Case Study by American Power Conversion (APC)
American Power Conversion (APC) helped diagnose and solve a potential overheating problem in a customer's new data center by using simulation to evaluate alternative designs prior to installing the equipment. The simulation showed that the customer's original design would result in overheating if a single computer room air conditioner (CRAC) failed for even a short period of time. "We used Flomerics' FloVENT computational fluid dynamics (CFD) software to identify the problem, evaluate its root cause, and develop a new design that can withstand loss of any one single piece of equipment," said Ben Steinberg, senior applications engineer for APC.
Steinberg used FloVENT to model the geometry of the data center and thermal and airflow characteristics of the servers and cooling units. "FloVENT is designed specifically for modeling heating and cooling applications so it is both easier to use and more powerful than general purpose CFD codes when evaluating data center cooling," Steinberg said. "FloVENT also has a team of support engineers that provide excellent support because they have a very good understanding of data center cooling issues."
Like most new data centers, this one made extensive use of blade servers, which greatly increase the amount of computing power that can be packed into a given amount of space but at the same time generate much more heat than traditional servers. The customer's initial design positioned the equipment in three rows with one CRAC in each row. Steinberg ran a steady state simulation with all CRAC units operating and then removed the CRACs from the model one after another and reran the simulation. The results showed that when one particular CRAC unit was removed, temperatures quickly reached the unacceptable 90°F level.
Steinberg suggested adding a fourth row of equipment with a fourth CRAC unit. He pointed out that the fourth row would provide each hot aisle with one CRAC unit on each side of the aisle, providing redundancy in case one unit failed. In order to confirm this assumption, Steinberg modified the FloVENT model to add the fourth row of equipment and the fourth CRAC. The results showed that regardless of which CRAC was removed, temperatures remained at safe levels of between 75°F and 80°F throughout the data center. Steinberg showed these results to the owner and the owner made the decision to go with the new design and purchase the four CRACs from APC.
"It would have been extremely costly to install the equipment in the data center, run tests, and then discover that it would not properly cool the servers in the event of an equipment failure," Steinberg said. "But it would have been far more costly for the customer to have its data center go down because of cooling problems. This helps explain why we run simulations for many of our proposals. Simulation provides a fast, relatively inexpensive, and accurate method of evaluating data center cooling performance without going to the time and expense required to actually install and test the equipment."
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