Intermittent spray cooling — Solution to optimize spray cooling
Intermittent spray cooling — Solution to optimize spray cooling
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DOI：
10.1109/eptc.2012.6507150
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发表时间：
2012-12
期刊：
影响因子：
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通讯作者：
S. Somasundaram;A. Tay
中科院分区：
文献类型：
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作者：
S. Somasundaram;A. Tay
一个最佳的喷雾冷却系统将提供适量的冷却剂，以消除所需的热通量，同时避免干燥的情况和表面上的厚膜（冷却剂）沉积。在大多数系统中，热通量随时间变化，并且待冷却的物体需要保持在特定的温度范围内。促进相变有助于减少冷却剂需求。满足这三个要求的方法之一是间歇式喷雾冷却（ISC），只有当温度开始上升到设定的极限以上时，喷雾机制才会被激活。将市售的低流速喷嘴与微型电磁阀一起沿着使用以实施间歇喷雾冷却。热测试芯片（具有模拟热源的集成加热器和充当温度传感器的二极管）用作待冷却的目标表面。使用去离子水作为冷却剂，流速在0.25-0.5 ml/sec的范围内。进行了稳态（连续喷雾）和间歇喷雾冷却实验。本文的主要目的是研究不同参数（热流密度、流量和设定点温度）对表面温度波动（幅度）、传热系数、阀门频率和开关周期的影响。在高于稳态温度5 ° C、10 ° C和15 °C下，对于2巴、4巴和6巴的喷嘴压力，对于11瓦/cm 2、22瓦/cm 2和33瓦/cm 2的热通量，记录瞬态温度波动、瞬态传热系数和过程频率。本文试图了解影响和控制间歇喷雾冷却过程的各种物理因素。一个重要的结论是，当表面温度处于足够高的温度时，温度波动被最小化，这是由于在喷射期间存在于表面上的液体膜的蒸发/沸腾所提供的缓冲效应。
An optimal spray cooling system would deliver just the right amount of coolant to remove the required heat flux and simultaneously avoid both, a dry out scenario and a thick film (of coolant) deposition on the surface. In most systems, the heat flux varies temporally and the object to be cooled needs to be maintained within a particular temperature range. Promoting phase change helps in reducing coolant requirement. One of the ways to meet all the three requirements is by intermittent spray cooling (ISC), in which the spray mechanism is activated only when the temperature starts rising above a set limit. A commercially available, low flow rate, nozzle was used along with a micro-solenoid valve to implement intermittent spray cooling. A thermal test chip (with integrated heaters to simulate heat source and diodes which act as temperature sensors) was used as target surface to be cooled. De-ionized water was used as coolant and flow rate was within the range of 0.25–0.5 ml/sec. Both steady state (continuous sprays) and intermittent spray cooling experiments were conducted. The main objective of this work is to study the effect of different parameters (heat flux, flow rate, and set-point temperature) on the fluctuation (amplitude) of surface temperature, heat transfer coefficient, valve frequency and on-off periods. Transient temperature fluctuations, transient heat transfer coefficients and frequency of the process were recorded for nozzle pressures of 2, 4 and 6 bar for heat fluxes of 11, 22, and 33 Watts/cm2 at 5, 10 and 15 °C above the steady state temperature. This paper attempts to understand the various physical factors which affect and dominate the intermittent spray cooling process. An important conclusion is that the temperature fluctuations are minimized when the surface temperature is at sufficient superheat, due to the cushioning effect provided by the evaporation/boiling of the liquid film present on the surface during spray off period.