Thermal Management Of Electronics Experiencing Large Power Dissipation Transients.
AdvisorWirtz, Richard A
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Recent developments with micro-porous surfaces have led to the introduction of very high heat flux boiling surfaces. For example, Wirtz and coworkers have introduced a structured porous surface that achieves in excess of 1.5MW/m2 in saturated pool boiling of water at 0.2atm (Tsat = 60°C); and, this increases to 2.1MW/m2 at 1.0atm (Tsat = 100°C). In this case, onset of nucleate boiling (ONB) occurs at approximately 2K superheat, and the high heat flux noted occurs at 9K superheat, so the boiling curve slope is very high, approximately 0.3MW/m2 per Kelvin superheat. This suggests that a viable thermal management approach to systems that experience large transient heat loading would be to design the heat sink so that the heat sink-to-coolant heat transfer surface would “ride” its boiling curve. At baseline power dissipation levels, boiling would occur at near ONB; and, the heat transfer surface would climb the (very steep) boiling curve as the power dissipation level rises, so that there would be only a moderate electronics temperature excursion. Vented (constant pressure), sealed and hybrid immersion cooled electronics systems are considered. A thermal response model, based on boiling curves having differing ONB and CHF points (boiling curve slopes) and boiling correlation calculates the thermal response of the system. Response time constants and maximum temperature excursions are correlated with boiling curve characteristics, and system geometric and thermo physical properties. We have obtained the temperature response with respect to time were obtained with different system parameters and have been compared with each other.