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Highly efficient electronics thermal management using two-phase impinging jets
Keywords: Liquid cooling, phase change, refrigeration
This work describes the development and testing of a novel direct impingement liquid cooling technique designed to take advantage of the strengths of previous generations of liquid cooling implementations. Driven by the need to implement high performance in a small package, high performance solutions such as spray cooling were abandoned in favor of extended nozzle jets. It was found that arrays jets issuing from tubular nozzles set at an angle to the heated surface could give very high performance by minimizing the interaction between neighboring jets and allowing a large drainage path past the nozzle tubes. Next, by controlling the saturation pressure in the impingement chamber (either by fluid selection or active pressure regulation or both), it was discovered that a condition of significant bubble generation and enhance heat transfer could be created with little to no excess temperature at the surface. Finally, by using direct impingement on the electronics package, or directly on the device, TIM resistances are eliminated. Work is ongoing to optimize the nozzle characteristics and to fully characterize the heat transfer performance. Initial results show that thermal resistances of 0.33 to 0.2 K-cm^2/W are readily achievable with R-245fa as the coolant. It also appears possible to remove heat from at least 3 devices in series, each dissipating 150 W, with little penalty when operated with significant phase change. A unique facility will be described that enables the visualization of the behaviors of bubbles and moving contact lines, and these observations are being incorporated into modeling efforts.
Timothy A. Shedd, Associate Professor of Mechanical Engineering
University of Wisconsin-Madison
Madison, WI

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