Heat Transfer Performance for a Falling-Film on Horizontal Flat Tubes

Abstract

Local and average heat transfer behavior for a falling film on horizontal flat tubes is explored through an experimental approach in this work. Experiments are conducted using water (18 °C) under different heat fluxes and tube spacings, with a range of flow rates that covers all flow modes. It is found that the local heat transfer coefficient decreases with distance from the top of the tube and is almost constant along the axial direction. Heat flux and tube spacing have almost no effect on average heat transfer performance within the experimental range. The average Nusselt number for the flat tube is close to that for round tube in a droplet flow mode, but it is almost twice as large as the round-tube result in the jet mode and sheet modes.