HEAT-TRANSFER IN THE THERMALLY DEVELOPING REGION OF A PULSATING CHANNEL FLOW

Abstract

A study is made of the heat transfer characteristics of a fully-developed pulsating Bow in a channel. The fluid at the channel inlet is of temperature T-0, and the channel walls are at uniform temperature T-w. Concern is directed to the thermally developing region. The unsteady Navier-Stokes equations are solved numerically to simulate a relatively slow throughflow at Re = 50, Pr = 0.7. Comprehensive time-dependent flow data are obtained for wide ranges of two key parameters, i.e. the pulsation amplitude 0 less than or equal to A less than or equal to 0.75, and the nondimensional pulsation frequency M up to 10.0. When M is low, the velocity profiles resemble much of the quasi-steady solutions. When M is large, the effects of oscillation are confine to a narrow zone adjacent to the walls. The changes in the Nusselt number Nu due to pulsation are pronounced in the entrance region, say X/(Re.Pr) < 1.0, and the impact of pulsation on Nu is minor at far downstream locations. The effects of M on Nu are noticeable when M is small and moderate. At high pulsation frequencies, heat transfer is little affected by the addition of pulsation. Detailed analyses on local behavior of heat transfer are made by using Fourier-series representations of the numerical results. These exercises indicate that. due to pulsation, both heat transfer enhancement and reduction can be expected in various axial locations of the channel. Based on these numerical results, physically plausible explanations are offered to interpret the axial behavior of heat transfer.