Numerical Investigation of Nucleate Pool Boiling Heat Transfer for Different Superheat Conditions
P I Shyamkumar, Suneet Singh, Atul Srivastava, Milan Visaria
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.