Volume of Fluid-Based Numerical Simulation of Single Bubble Growth on Constant Temperature Surface

Abstract

Nucleate boiling is considered an efficient mechanism of heat transfer. Its applications can be found in many industries including nuclear, processing, solar, power, microelectronics and HVAC. However, applications of nucleate boiling are not matured enough so that they can be implemented with safety. The utilization of boiling for transferring heat has led to flow instability and flow reversals in nuclear reactors and microchannels respectively. To avoid such incidents and pave a way for safe commercial application of nucleate boiling, the physics behind nucleate boiling needs to be elucidated completely. For this purpose, several mechanistic and empirical models have been proposed after decades of research. But nucleate boiling depends on range of parameters including surface properties, heat flux, nucleation density, fluid properties and adopted applications. A comprehensive model which can incorporate all these variables has not been proposed so far. Neither such perfect experimental setups can be devised in near future which could depict the physics of the whole phenomena with predictable accuracy. So, an alternative approach that could reveal the physics behind nucleate boiling and provide a baseline for experiment is needed. The advances and diversity in numerical simulation can help in understanding the phenomenon of nucleate boiling. This study utilizes these advances and focuses on numerical simulation of nucleate boiling. A 2-dimensional axi-symmetric domain is considered for performing the simulation. Nucleation and thermal boundary layer development process are bypassed. For this purpose, a hemi-spherical bubble and linear thermal boundary layer are patched in domain. Source of mass and energy due to phase change are implemented in governing equations through additional subroutines written in C language. The accuracy of numerical model is assessed by comparing the results of bubble shape, evolution of bubble contours and its size with experimental datum in available literature. Relatively a good agreement is found in shape and departure time except the size of the bubble, which is larger than the results of experiment due to extensive evaporation at interface between the two phases. In addition, an insight into temperature and velocity fields obtained from simulation are analyzed which cannot be revealed by experimental results.