Numerical investigation of internal flows with sub-cooled nucleate boiling

Abstract

This paper discusses numerical simulations of sub-cooled nucleate boiling in a duct using Reynolds Stress Model (RSM) and conjugate heat transfer (CHT). The predictions of flow characteristics and distributions of interfacial area concentration (IAC), Sauter mean diameter (SMD), temperature of liquid and void fraction of gas are investigated using the above methods. The RSM turbulence model is used in the simulations to incorporate anisotropic turbulence, which has been reported in experimental studies, where it has been observed that the flow is affected by the drag of bubbles nucleating at a heater block. The heat flux, which leads to phase change of the fluid, has been applied in two different ways. One implementation involves the fluid-only domain with a particular boundary providing constant heat flux, whereas, in the other case, the solid duct has been made part of the computational domain and the fluid has been heated via CHT. The study first focuses on investigating the mean and fluctuating velocity components over the heated section of the domain. It is found that the bubbly layer is predicted thinner in the solid-fluid case than the fluid-only case. Amount of heat flux added to the coolant is higher in the case where the computational domain is limited to the fluid only. This results in a relatively larger amount of void fraction directly above the heated section.