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

同时进行了两个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，该系统由卧式蒸发器、测试芯片、竖直管、卧式冷凝器、降液管、液体过冷器和维持大气压的胶袋组成。测试了一个光滑的测试芯片和4个带有微销-翅片的测试芯片(尺寸分别为30×60、30×200、50×190、50×270μm^2)。测试芯片尺寸为10×10×0.5 mm^3，位于横截面为5×14 mm^2的水平通道底面。在液柱高度为300 mm、蒸发器输入功率为100~250W的条件下，FC-72W的循环流量为120~270g/min，在W=150、200g/min、液体过冷度分别为10、25、35K时进行了换热实验，除临界热流密度Q&lt；CHF&gt；显著降低外，与池沸腾的换热特性基本相同。W=150g/min和200g/min时的比较结果表明，W-150g/min时，沸腾核区的换热系数稍高，而临界热流密度最大降低了10%。Q&lt；CHF&Gt；的最高值为56W/cm~2。第二个实验是关于微针刺翅片尺寸对FC-72池沸腾的影响。翅片的厚度范围为10~50μm，高度范围为60~270μm。液体过冷度分别设置为0、3、25和45K，所有微针翅片的核沸腾曲线斜率都非常陡峭，临界热流点处的壁面过热度小于大规模集成电路芯片的最高允许温度(=85℃)。Q&lt；CHF和GT；随着翅片高度和液体过冷度的增加而增大。获得的Q&lt；CHF&Gt；最高值为85W/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.