Experimental study on the evaporative cooling of densely packed LSI chips by use of a natural circulation loop

点击翻译按钮获取中文摘要

Two experiments that were aimed at high flux liquid cooling of LSI chips were conducted concurrently. The first experiment was concerned with the performance of a natural circulation liquid cooling system consisting of a horizontal evaporator, a test chip, a vertical tube, a horizontal condenser, a downcomer, a liquid subcooler, and a rubber bag for maintaining atmospheric pressure. A smooth test chip and four test chips with micro-pin-fins (dimensions of 30×60, 30×200, 50×190, 50×270 μm^2) were tested. The test chip had the dimensions of 10×10×0.5 mm^3. It was located at the bottom surface of a horizontal duct with the cross section of 5×14 mm^2. FC-72 was used as a test liquid. The circulation rate of FC-72 W ranged from 120 to 270 g/min for the liquid column height of 300 mm and the power input to the evaporator of 100-250 W. Heat transfer experiments were conducted at W = 150 and 200 g/min and the liquid subcooling of 10, 25 and 35 K. The heat transfer characteristics was basically the same as the case of pool boil ing except that the critical heat flux q_<CHF> decreased considerably. Comparison of the results for W= 150 and 200 g/min revealed that while the heat transfer coefficient in the nucleate boiling region was somewhat higher for W - 150 g/min, the critical heat flux was lower by a maximum of 10 %. The highest value of q_<CHF> obtained was 56 W/cm^2. The second experiment was concerned with the effect of the size of micro-pin-fin on the pool boiling of FC-72. The fin dimensions ranged from 10 to 50 μm for the thickness, and from 60 to 270 μm for the height. The liquid subcooling was set at 0, 3, 25 and 45 K. For all micro-pin-finned chips, the slope of nucleate boiling curve was very steep and the wall superheat at the critical heat flux point was less than the maximum allowable temperature for LSI chips (= 85 ℃). The q_<CHF> increased with increasing fin height and liquid subcooling. The highest value of q_<CHF> obtained was 85 W/cm^2.