Numerical study of buoyancy and inclination effects on transient mixed convection in a channel with two facing cavities with discrete heating

In this work, the two-dimensional mixed convection flow and heat transfer from a rectangular channel with two facing identical open cubic cavities with discrete heating is studied numerically. The walls facing the opening are isothermal and all other bounding walls of the cavities and the channel are non-adiabatic. A parametric study has been conducted using water (Pr=7) as the working fluid. The effect of buoyancy strength or Richardson number, Ri=Gr/Re ² , and its corresponding sensitivity to duct orientation on the overall flow and thermal evolution in space and time is studied for Reynolds numbers from 100 to 1000, channel inclination of 0 ^o ≤ γ ≤ 90 ^o and cavity aspect ratios (AR, ratio between the width and height of the enclosures) of 0.25, 0.5 and 1. The complex flow features are comprehensively presented in the form of velocity, vorticity and temperature contours for a wide range in the parametric space. The results reported herein demonstrate that the cavity aspect ratio plays a significant role on the achieved flow and temperature fields, oscillation frequencies and heat transfer characteristics of the double cavity. In addition, it has been found that the Reynolds and Prandtl numbers as well as the heat losses through the channel walls have a strong influence on the dynamical response of the system for all values of the heat loss parameter.