A Numerical Study of Transient Mixed Convection Flows in a Thermal Storage Tank

Abstract

Transient, two-dimensional, mixed convection flows in a thermal storage tank have been studied using a previously developed numerical technique based on the marker and cell method. The governing equations are the conservation equations for laminar, natural convection flow based on the Boussinesq approximation. Forced convection flow is superimposed through the use of appropriate boundary conditions (inflow and outflow conditions). The transient heat transfer and fluid flow characteristics are examined for different boundary conditions. Typical transient temperature and velocity distributions are presented. The effect of inflow and outflow configurations on the storage tank thermal performance is also investigated. It is found that the device can store energy at a faster rate when hot water is discharged into the tank from the top and colder water is extracted from the bottom. However, the discharge direction into and from the tank, which can be either vertical or horizontal, is found to have negligible effect on the thermal storage efficiency.