Analytical investigation of heat or mass transfer and friction factors in a corrugated duct heat or mass exchanger

Abstract

Heat and mass transfer design parameters are readily available for flow in circular and flat ducts for a variety of boundary conditions. However, the boundaries of the flow passages found in regenerators, rotary heat exchangers, rotary mass exchangers, etc. are usually, of necessity, other than circular or parallel plate. One very common exchanger made up of many flow passages looks like the end view of several layers of corrugated cardboard. The boundary of the cross-section normal to the flow of one of these passages may be represented by a sine curve from — π to π forming the upper portion of the duct and a flat plate stretched between — π and π to form the bottom portion of the boundary. This paper presents the computed friction factors and Nusselt numbers (or Sherwood numbers) of this geometry for several aspect ratios and Biot numbers (or wall reaction rates). These results agree well with the very limited experimental data reported in the literature. Since the data in the literature are limited, this analysis provides additional design information on a very important heat and mass transfer geometry. The results obtained could not be adequately estimated from the results of a circular geometry or a flat duct because the corners in the sinusoidal duct provide an inherently different geometry. The results also differ considerably from a triangular duct. An unusual result for the sinusoidal geometry is the behaviour of the Nusselt number. It decreases with decreasing Biot Number.