Heat Transfer and Pressure Drop Characteristics of an Assembly of Partially Segmented Plates

Abstract

The heat transfer and pressure drop characteristics of an assembly of plates in a rectangular duct, with part of each plate segmented transversely and the segments inclined at 25 deg to the flow, have been investigated experimentally in the range of Reynolds numbers between 900 and 4000. The segmented-to-total width ratios β were 0.81 and 0.61. Mass transfer measurements of naphthalene were made to obtain the heat transfer coefficient. A new spray technique is described for preparing the mass transfer models, which are so complex that previously reported techniques cannot be applied. The mass transfer models simulate louvered fin surfaces used currently in industries. The heat transfer coefficient is found to be a strong function of the segmented-to-total plate width ratio β, and it decreases as β decreases. The heat transfer coefficient of an existing louver fin heat exchanger whose geometries are in close proximity to one of the model configurations was compared with that of the model, and good agreement was obtained between the two. The pressure drop (through the plate assembly) measurements showed that the pressure drop is mainly due to inertia loss in the experimental range of the present work, and that the streamwise, per-row pressure drop coefficient Kp is a function of only β and independent of the Reynolds number NRe,Dh. It was found, for a fixed blower power, that there exists an optimum Reynolds number (NRe,Dh)opt for maximum Nusselt number at a given segmented-to-total width radio β. A similar trend is also found for a fixed pressure drop.