Vol. 30 (2020): Volume 30 2020

ABSTRACT

In this paper laminar mixed convection in partially heated vertical channel was investigated numerically. The temperature profiles at various axial locations, axial velocity profile in the heated part of the channel and streamlines for aiding buoyancy flow are presented. The case of aiding mixed convection is considered, with the lower part of the channel is subjected to uniform heat flux. Conservation equations of continuity, momentum and energy were solved simultaneously using Finite volume method. The effect of the length of the heated section on the flow pattern and heat transfer performance is investigated for given Grashof numbers. The influence of axial diffusion and it's relevant to flow reversal at the entrance region of the channel was taken into account in the momentum and energy equations and particular attention is given to the ratio
The effect of aiding bouncy forces on the hydrodynamic and thermal fields was examined for air with Re = 500, . Reversal Flow was observed near the axis for aiding buoyancy flow. Streamlines in the channel, isotherms, temperature distribution, and velocity profiles, local Nusselt number and friction factor were presented. The numerical results presented revealed some interesting features which may be summarized as: (i) the effects of the heated part of the channel on the hydrodynamic and thermal fields are demonstrated for│Gr │≥ 105 for aiding flow. (ii) Nusselt number approaches the asymptotic value at the vicinity of the channel wall for Gr ≤ 105. For Gr ≥ 106 the Boussinesq approximation over predicts the overall heat transfer rate. (iii) For Gr up to 4x105 The Boussinesq approximation still predicts reasonably the heat transfer rate. In general, the heated section modifies the flow field and hence the wall convective heat transfer.