Miltiphase micro-pin-fin heat sink : pressure drop and heat transfer

Thesis (M.S.)--University of Hawaii at Manoa, 2007.Includes bibliographical references (leaves 74-76).xvii, 76 leaves, bound 29 cmThis paper is a study concerning the thermal and hydrodynamic characteristics of a liquid single-phase flow and flow boiling in an array of micro-pin-fins. An array of 1950 staggered square micro-pin-fins with 200 x 200 µm2 cross-section by 670 µm height were fabricated into a copper heat sink test section. The ratios of longitudinal pitch (SL) and transverse pitch (ST) to pin-fin equivalent diameter (de) are equal to 2. Deionized water was used as the cooling liquid. Two coolant inlet temperatures of 30•C and 60•C, and six maximum mass velocities for each inlet temperature, ranging from 183 to 420 kg/m2s, were tested. The corresponding inlet Reynolds number ranged from 45.9 to 179.6. For single-phase flow, the measured pressure drop was used to calculate the average friction factor, and the measured temperature distribution was used to evaluate single-phase heat transfer coefficient and Nusselt number. Predictions of the previous friction factor and heat transfer correlations that were developed for low Reynolds number (Re < 1000) single-phase flow in pin-fin arrays were compared to the present micro-pin-fin single-phase pressure drop and Nusselt number data, respectively. Most predictions of other friction factor and heat transfer correlations were significantly different from the experimental data collected in this study. Two new heat transfer correlations were proposed for average heat transfer based on the present data, in which average Nusselt number is correlated to the average Reynolds number by power law. Also, there is indication of a strong dependence of Nusselt number on Reynolds number in micro-pin-fin arrays. A new power-law type of correlation was proposed base on the present pressure drop data too. Last, micro-pin-fin heat sink was tested at high temperatures in which pressure drop and temperature were measured and boiling curves were obtained