Numerical simulation of film boiling heat transfer in the presence of a uniform electric field using front tracking

Abstract

Film boiling has many applications in various industries, such as industrial furnaces, heat exchangers in nuclear and fossil power plants. In this paper, film boiling on a horizontal plate in the presence of a uniform electric field is simulated in two dimensions by a finite difference/front tracking method with constant heat flux and constant wall temperature boundary conditions. Applying an electric field is an active method that is widely used to enhance heat transfer. Simulation of this phenomenon is of great importance in industry to predict the growth and movement of steam bubbles produced. The electric field is applied by an electric potential difference to the upper and lower boundaries. It is assumed that the working fluid is a completely dielectric fluid. The electric force is a volumetric force that is added directly to the Navier-Stokes equations. The present numerical method is validated by simulation of film boiling in the presence and absence of electric field and comparing with available experimental and numerical results. The effect of the electric field on the Nusselt number for constant heat flux and constant wall temperature boundary conditions are investigated. The effect of dimensionless numbers is also studied. Generally, the Nusselt number increases by applying an electric field. The bubble growth time, bubble thickness and vapor film thickness are reduced by applying an electric field. Small bubbles are formed on the surface with increasing electric field for constant heat flux boundary condition. The number of bubble growth sites increased with increasing electric field in the constant wall temperature boundary condition, or in other words, the instability wavelength decreased.