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Non-contact experiments to quantify the microlayer evaporation heat transfer coefficient during isolated nucleate boiling regime
International Communications in Heat and Mass Transfer ( IF 7 ) Pub Date : 2021-02-16 , DOI: 10.1016/j.icheatmasstransfer.2021.105191
L. Surya Narayan , Atul Srivastava

Experiments to understand the relationship between dynamics of superheat layer, microlayer evaporation and bubble growth process during single bubble formation under saturated pool boiling regime have been conducted. Thin film interferometer and rainbow schlieren deflectometry have been employed in tandem to simultaneously map the transient evolution of microlayer and superheat layer along with the bubble growth process. During initial time instances of growth process, heat flux dissipated in the microlayer region is determined to be as high as ~1 MW/m2 for the range of experimental conditions employed. As a result, a large temperature drop is observed in the microlayer region. As the bubble growth process enters its final stages, reduced temperature levels of the heated substrate result into a significant reduction in the depletion rate of the inner core region of microlayer, while the evaporation rate of its peripheral region is seen to increase. The consolidated evaporative heat transfer coefficient for the entire bubble cycle is determined to be ~140 kW/m2K for q″ = 50 kW/m2 and 170 kW/m2K for q″ = 80 kW/m2. The corresponding accommodation factor required for predicting the evaporative heat transfer coefficient values through kinetic theory-based model is determined to be ~0.015.



中文翻译:

非接触实验量化孤立核沸腾过程中微层蒸发的传热系数

为了了解饱和池沸腾条件下单个气泡形成过程中过热层动力学,微层蒸发和气泡生长过程之间的关系,进行了实验。串联使用了薄膜干涉仪和Rainbow schlieren挠度仪来同时绘制微层和过热层随气泡生长过程的瞬态演变图。在生长过程的初始时间期间,在微层区域中耗散的热通量被确定为高达〜1 MW / m 2对于所使用的实验条件范围。结果,在微层区域中观察到大的温度下降。当气泡生长过程进入其最终阶段时,受热基板的降低的温度水平导致微层内芯区域的耗竭率显着降低,而其外围区域的蒸发率则增加。整个气泡循环合并蒸发热传导系数被确定为〜140千瓦/米2 K代表q “= 50千瓦/米2和170千瓦/米2 K代表q ”= 80千瓦/米2。通过基于动力学理论的模型预测蒸发传热系数值所需的相应调节系数被确定为〜0.015。

更新日期:2021-02-16
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