Abstract

The paper describes the results of boiling heat transfer during FC-72 flow in minichannels, obtained on the basis of time-dependent experiments. The main goal of the work was to determine the heat transfer coefficient by means of the finite element method with the spacetime Trefftz-type basis functions based on the Hermite interpolation. The crucial part of the experimental stand was the test section with minichannels of 1.7 mm depth. One wall of the minichannels constituted a heated foil which was resistive heated. Temperature of outer foil surface was measured due to thermocouples in the test minichannel. The onset of flow boiling was induced by two ways: lowering the pressure in the circulating system or increasing the heat flux supplied to the heater. Dynamic changes in thermal and flow experimental parameters accompanying the onset of flow boiling, including: temperature of the heater, pressure and mass flow rate, were illustrated. The results were performed as: foil temperature and heat transfer coefficient versus the distance from the minichannel inlet or time. It was observed that heat transfer coefficient values increased at the boiling incipience region for both analyzed experiments. Boiling curves were discussed. The error analysis of the results was provided. Mean relative errors of the heat transfer coefficient did not exceed 11%. Our results were compared with selected correlations from the literature.

摘要

本文描述了在时间相关实验的基础上获得的 FC-72 在微通道中流动过程中的沸腾传热结果。这项工作的主要目标是利用基于 Hermite 插值的时空 Trefftz 型基函数的有限元方法确定传热系数。实验台的关键部分是具有 1.7 毫米深度的微型通道的测试部分。微型通道的一个壁构成了电阻加热的加热箔。由于测试微通道中的热电偶，测量了外箔表面的温度。流动沸腾的开始由两种方式引起：降低循环系统中的压力或增加提供给加热器的热通量。说明了伴随流动沸腾开始的热和流动实验参数的动态变化，包括：加热器的温度、压力和质量流量。结果执行为：箔温度和传热系数与距微通道入口的距离或时间的关系。观察到，对于两个分析实验，传热系数值在沸腾起始区域都有所增加。讨论了沸腾曲线。提供了结果的误差分析。传热系数的平均相对误差不超过11​​%。我们的结果与文献中选定的相关性进行了比较。箔温度和传热系数与距微通道入口的距离或时间的关系。观察到，对于两个分析实验，传热系数值在沸腾起始区域都有所增加。讨论了沸腾曲线。提供了结果的误差分析。传热系数的平均相对误差不超过11​​%。我们的结果与文献中选定的相关性进行了比较。箔温度和传热系数与距微通道入口的距离或时间的关系。观察到，对于两个分析实验，传热系数值在沸腾起始区域都有所增加。讨论了沸腾曲线。提供了结果的误差分析。传热系数的平均相对误差不超过11​​%。我们的结果与文献中选定的相关性进行了比较。