A Study of Critical Heat Flux During Flow Boiling in Microchannel Heat Sinks
A Study of Critical Heat Flux During Flow Boiling in Microchannel Heat Sinks
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DOI：
10.1115/1.4004715
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发表时间：
2011
影响因子：
--
通讯作者：
Tailian Chen;S. Garimella
中科院分区：
文献类型：
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作者：
Tailian Chen;S. Garimella
微通道内两相输运的冷却能力受到临界热流密度（CHF）的限制。由于该现象的性质，获得可靠的CHF数据而不对被测设备造成损坏是具有挑战性的。在这项工作中，FC-77在硅热测试模具包含60个平行的微通道流动沸腾的临界热通量进行了测量，在五个总流量通过微通道在20-80毫升/分钟的范围内。CHF是由干燥引起的壁附近的出口的微通道，这又是由于逆流上游的微通道。被推回进气室的气泡聚集;由此产生的流动阻塞是CHF发生的可能原因，CHF的特征在于出口附近的壁温突然增加和微通道两端的压降突然降低。从四个独立的研究与水，R-113，和FC-77作为冷却剂的五个实验中获得的49个数据点的数据库进行编译和分析。据发现，CHF有一个很强的依赖于冷却剂，流量和面积上的热通量定义的基础。然而，在给定的流率下，临界热输入（当CHF发生时到冷却剂的总热传递速率）仅取决于冷却剂，并且对微通道散热器的细节（通道尺寸、通道数量、基底材料和基底面积）具有最小的依赖性。在多个平行微通道中的流动沸腾的临界热输入遵循一个明确的趋势与产品的质量流量和汽化潜热。提出了一种幂律相关性，它提供了一个简单的，但准确的方法来预测CHF。在CHF的热力学出口质量也进行了分析和讨论，以提供深入的CHF现象在包含多个平行的微通道的散热器。
The cooling capacity of two-phase transport in microchannels is limited by the occurrence of critical heat flux (CHF). Due to the nature of the phenomenon, it is challenging to obtain reliable CHF data without causing damage to the device under test. In this work, the critical heat fluxes for flow boiling of FC-77 in a silicon thermal test die containing 60 parallel microchannels were measured at five total flow rates through the microchannels in the range of 20–80 ml/min. CHF is caused by dryout at the wall near the exit of the microchannels, which in turn is attributed to the flow reversal upstream of the microchannels. The bubbles pushed back into the inlet plenum agglomerate; the resulting flow blockage is a likely cause for the occurrence of CHF which is marked by an abrupt increase in wall temperature near the exit and an abrupt decrease in pressure drop across the microchannels. A database of 49 data points obtained from five experiments in four independent studies with water, R-113, and FC-77 as coolants was compiled and analyzed. It is found that the CHF has a strong dependence on the coolant, the flow rate, and the area upon which the heat flux definition is based. However, at a given flow rate, the critical heat input (total heat transfer rate to the coolant when CHF occurs) depends only on the coolant and has minimal dependence on the details of the microchannel heat sink (channel size, number of channels, substrate material, and base area). The critical heat input for flow boiling in multiple parallel microchannels follows a well-defined trend with the product of mass flow rate and latent heat of vaporization. A power-law correlation is proposed which offers a simple, yet accurate method for predicting the CHF. The thermodynamic exit quality at CHF is also analyzed and discussed to provide insights into the CHF phenomenon in a heat sink containing multiple parallel microchannels.