Flow and Pressure Distributions in Short Heat Exchanger Cores with Abrupt Entrance and Exit


Mechanical Engineering, University of Tabriz


The typical installation of a heat exchange device usually involves a flow contraction at the core entrance and a flow expansion at the core exit. Repeated flow Contraction and expansion are experienced in the flow passages of some compact heat exchangers. The latter refers to the flow passages in the plate-fin type with louvered fins or stripped fins and in the tubular type with dimpled-circular or flat tubes. Similar flow situations are encountered in flat-edged orifices. The majority of these constrictions are characterized by small length-to-hydraulic diameter ratio so that the flow after being disrupted has a little time in developing into an appropriate pattern before it is disrupted again. This work deals with a flow system consisting of a parallel channel with a flow constriction of small . The flows at both ends of the channel are laminar, fully developed. The full Navies-Stokes equations for the steady two-dimensional flow are solved numerically using the finite-difference technique. Some preliminary results are obtained for the distributions of velocity components, streamline and pressure. The result for a flow of small Reynolds number show qualitative agreement with the flow pattern of a similar flow system obtained by visualization method.