Heat is the primary enemy of any electronic component. In order for an electronic device to have a long, problem-free life, cooling must be an important design consideration. The problem of cooling CPUs, in particular, has grown as processors have become more powerful. Water cooling systems are one option for keeping blazing- fast CPUs cool. As an example, engineers used finite element analysis (FEA)-based, multiphysics analysis software to consider whether a proposed water cooling system design would regulate CPU temperature in order to meet the manufacturer’s recommendations.

Simple heat dissipation methods, such as adding heat fins and relying on natural convection, have often been sufficient for electronics. However, as devices become more powerful, it becomes increasingly important to produce the flow of a fluid to create forced convection for greater cooling capacity. The fluid may be air-moved by a fan or water within a water cooling system. The key is to produce a sufficient amount of forced convection to keep a device within its recommended operating temperature range during sustained use.

FEA-based, multiphysics analysis software provides engineers designing electronic components with a tool to determine the required flow velocities. As an electronics OEM and provider of wireless communications equipment, Wytec of Santa Clara, CA, needed to know what fluid flow velocity was necessary to cool the electronics. ALGOR’s forced convection capability determined what level of fluid flow would produce the desired temperatures and prevent the electronics from overheating and failing.

The water cooling system was modeled in ALGOR. A fluid flow analysis was then performed based on an inlet velocity of 20 in./sec. to obtain a velocity profile throughout the water tube. The inlet velocity of 20 in./sec. was used because it is a common flow rate for an off-the shelf small pump. This velocity profile was then used as input to the heat transfer analysis to simulate forced convection. In addition to the forced convection input, an internal heat generation load considered 29.5 watts of energy from the CPU, a specified temperature of 70°F was applied at the inlet, and another convection load accounted for heat loss through natural convection to ambient air. The steady-state heat transfer analysis produced a temperature profile throughout both the water and cooling block with the maximum temperature reaching 82°F.

The multiphysics analysis was then repeated with a water inlet velocity of 0 in./sec. In this case, the maximum temperature reached 220°F. The analysis verified that the system would successfully cool the CPU with a water flow rate of 20 in./sec. and thereby support reliable performance over the life of the computer.

For more information on using ALGOR’s multiphysics analysis products, including the forced convection capability, contact ALGOR, Inc., 150 Beta Drive, Pittsburgh, PA 15238; Tel: 1-800-48-ALGOR; or visit the Web site at: www.ALGOR.com.

NASA Tech Briefs Magazine

This article first appeared in the June, 2002 issue of NASA Tech Briefs Magazine.

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