Local Thermal Non-Equilibrium in Entrance Region of a Porous Channel

ABSTRACT

This research considers a cross flow over square tubes in a channel between two parallel plates for different aspect ratios by direct numerical method. The array of tubes is in line arrangement and resembles the porous medium within the channel. The governing equations include two dimensional Navier–Stokes equations along with energy equations of fluid. The present work indicates that the pressure drop through the cross flow heat exchanger is a function of distance. The average heat transfer coefficient of each tube column rapidly approaches to its asymptotic value as flow passes over each of the tubes. The result reports that the heat transfer coefficient of the second column of tubes is a maximum and after that decreases slightly. This maximum value of heat transfer coefficient is caused by the vortices generated by the first column of tubes. After the second column, the flow pattern and generation of the vortices are remained unchanged and the heat transfer coefficient remains constant. The overall heat transfer coefficient over all tubes within the channel for a fixed set of the aspect ratios reduces monotonically against the axial distance.

Keywords: Porous media, Heat transfer, Heat exchanger, Numerical method.

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