Abstract

Nucleate boiling has been a topic of great interest due to its heat transfer enhancement capability. In the present work, a highly resolved numerical model is developed combining two submodels, a microlayer evaporation submodel and phase change sub model, to get insights on various sub-processes like bubble inception, growth, departure, waiting time and scavenging effect. Here, a new approach in contact angle modeling is implemented by using a variable contact angle which is pre-defined using curve-fitting of the experimental data with respect to bubble cycle time. For the performance evaluation of the model, two fluids, water and a refrigerant (HFE7100) under two superheat conditions are studied and results are validated with existing experimental data. The simulations are carried out to understand the individual contribution of microlayer and other sub-processes toward overall heat transfer and such individual contributions are rare in the available literature. It was concluded that microlayer heat transfer is the second most important contributing component of heat transfer for both superheat conditions and contributes ∼30% for both the fluids. Moreover, the influence of superheat over bubble dynamics is analyzed. Overall, the comparison of present simulation with existing test data indicates a satisfactory agreement.

摘要

由于其传热增强能力，核沸腾一直是一个非常有趣的话题。在目前的工作中，结合两个子模型，微层蒸发子模型和相变子模型，开发了一个高分辨率的数值模型，以深入了解各种子过程，如气泡开始、生长、离开、等待时间和清除效果。在这里，接触角建模的一种新方法是通过使用可变接触角来实现的，该接触角是使用与气泡循环时间相关的实验数据的曲线拟合来预定义的。对于模型的性能评估，研究了两种过热条件下的两种流体、水和制冷剂 (HFE7100)，并使用现有实验数据验证了结果。进行模拟是为了了解微层和其他子过程对整体传热的个体贡献，这种个体贡献在现有文献中很少见。得出的结论是，微层传热是两种过热条件下传热的第二重要贡献成分，对两种流体的贡献约为 30%。此外，还分析了过热度对气泡动力学的影响。总体而言，当前模拟与现有测试数据的比较表明了令人满意的一致性。得出的结论是，微层传热是两种过热条件下传热的第二重要贡献成分，对两种流体的贡献约为 30%。此外，还分析了过热度对气泡动力学的影响。总体而言，当前模拟与现有测试数据的比较表明了令人满意的一致性。得出的结论是，微层传热是两种过热条件下传热的第二重要贡献成分，对两种流体的贡献约为 30%。此外，还分析了过热度对气泡动力学的影响。总体而言，当前模拟与现有测试数据的比较表明了令人满意的一致性。