Flat-plate oscillating heat pipes and thermal spreading analysis of heat spreaders
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Electronic components have and will continue to miniaturize. Therefore, the need for efficient thermal management devices will continue to be a driving force in engineering. In the current investigation, the effects of form factor and channel configuration - including the three dimensional channel and Tesla-type check valve - on the heat transport capability in a flat-plate oscillating heat pipe (FP-OHP) - have been investigated. Based on experimental results, it has been concluded that the three-dimensional channel configuration allows for the FP-OHP to operate more independently of gravity and to manage higher heat fluxes. Via neutron radiography, it was quantitatively concluded that Tesla-type check valves are able to rectify oscillating fluid motion within an FP-OHP - allowing for bulk circulation which is accompanied with a marked reduction in thermal resistance. Statistical learning methods were employed to determine the effects of internal flow rectification on the oscillatory wall temperature of a valved FP-OHP. It was found that the oscillating temperature signal is multi-Gaussian (mixture model) and that a valved FP-OHP provides for less variance in number of mixture components and provides for higher Shannon entropy. Because the effective thermal conductivity of a FP-OHP largely depends on its form factor and heating/cooling configuration, a mathematical model predicting the thermal spreading performance of a heat spreader embedded with OHPs has been developed. The mathematical model utilizes a non-dimensional contact area ratio and unique non-dimensional temperature scheme to allow for characterization of novel heat spreaders.
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