Heat Transfer and Fluid Flow Analysis of Interrupted-Wall Channels, With Application to Heat Exchangers

Abstract

An analysis has been made of laminar flow and heat transfer in channels whose walls are interrupted periodically along the streamwise direction. Such channels are frequently employed in high-performance compact heat exchangers. Numerical solutions of the mass, momentum, and energy conservation equations yielded local heat transfer and pressure drop results. These results were obtained for a range of Reynolds numbers and for several values of a dimensionless geometrical parameter characterizing the streamwise length L of the individual plate segments which make up the interrupted walls. The Prandtl number was fixed at 0.7 for all the calculations. The basic heat transfer and pressure drop results were employed to investigate whether an interrupted-wall channel experiences an augmented heat transfer rate compared with that for a parallel plate channel. For conditions of equal heat transfer surface area and equal pumping power, appreciably higher heat transfer rates prevailed in the interrupted-wall channel for a wide range of operating conditions. The augmentation was especially marked for relatively short channels and high Reynolds numbers. The results also demonstrated the existence of a new type of fully developed regime, one that is periodic. At sufficiently large downstream distances, the velocity and temperature profiles repeat their values at successive axial stations separated by a distance 2L and, in addition, the average heat transfer coefficient for a plate segment takes on a constant value.