The effect of introducing tip clearance to a liquid cooled array of shrouded pins fins is examined. Three arrays of height to diameter ratio ranging from 0.5 to 1.1 were evaluated experimentally. The arrays were exposed to a uniform heat flux of 0.02 to 0.26 W/mm2 and cooled with water through a nominal Reynolds number range of 200 to 10,000. Tip clearance of 0 to 25% of pin height was assessed. Mean heat transfer rates and adiabatic pressure drop across the array were determined and empirical correlations are proposed. The introduction of clearance was seen to increase overall heat transfer in some cases.

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Thermoelectric cooling (TEC) modules which are rated for operation up to 200°C are now widely available commercially, making them potential candidates for use in the thermal management of high temperature electronics applications. Through the use of these TECs, traditional electronic devices could be employed at much higher temperatures than they might otherwise tolerate, by creating a low temperature "micro-environment'' around the specific components of interest. To gage the feasibility of using TECs for high temperature thermal management, a single stage TEC was operated at constant current, near its maximum temperature limit for up to 1500 hours to assess the long term effect of elevated temperature on the module's performance. Results of the test showed a gradual decline in the overall temperature differential generated by the TEC during powered operation. Analysis of the exposed module by E-SEM suggests diffusion of Te from the thermoelements into the Bi solder region and a degradation of the Ni diffusion barrier between the copper tabs and the bismuth solder layer.