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

同时进行了两项针对大规模集成电路芯片高通量液体冷却的实验。第一个实验是关于自然循环液体冷却系统的性能，该系统由一个水平蒸发器、一个测试芯片、一个垂直管、一个水平冷凝器、一个下降管、一个液体过冷却器和一个用于维持大气压力的橡胶袋组成。测试了一个光滑测试芯片和4个尺寸分别为30×60、30×200、50×190、50×270 μm^2的微针鳍测试芯片。测试芯片的尺寸为10×10×0.5 mm^3。它位于横截面为5×14 mm^2的水平风管的底面。FC-72作为试验液。当液柱高度为300 mm，蒸发器输入功率为100-250 W时，fc - 72w的循环速率为120 ~ 270 g/min。换热实验分别在W = 150和200 g/min，液体过冷10、25和35 K下进行。除临界热流密度q_<CHF>显著减小外，换热特性与池沸腾情况基本一致。对比W= 150和200 g/min时的结果表明，当W= 150 g/min时，核沸腾区的传热系数略高，但临界热流密度最大降低10%。q_<CHF>的最大值为56 W/cm^2。第二个实验研究了微鳍尺寸对FC-72池沸腾的影响。翅片厚度范围为10 ~ 50 μm，高度范围为60 ~ 270 μm。液体过冷分别设置为0、3、25和45 K。对于所有的微针翅片芯片，核沸腾曲线的斜率都非常陡，临界热流点处的壁过热小于LSI芯片的最高允许温度（= 85℃）。q_<CHF>随翅片高度和液体过冷度的增加而增大。q_<CHF>的最大值为85 W/cm^2。

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.