FIRST EXPERIMENTAL RESULTS ON FORCED-CONVECTION HEAT TRANSFER INSIDE A WAVY CHANNEL

In this paper we present the results of an experimental investigation on average heat transfer characteristics and pressure drops of a forced air-flow through a rectangular channel with the lower and upper walls wavy configured. The test section is 880-mm long, 120-mm wide and 12-mm height, whereas waviness have in streamwise direction a triangular profile of 68-mm pitch and 161° apex angle; this geometry reproduces in a larger-scale a typical passage between two wavy-fins in a compact heat exchanger. The channel is operated with the wavy walls at uniform temperature whereas the side ones are adiabatic. Results here presented are for a wavy-wall temperature of 40 °C, air inlet-temperature of near 20 °C, and Reynolds numbers ranging from about 700 to 7500. Comparisons with the results specifically obtained in a flat rectangular channel, with the same dimensions and operating conditions, show that for the investigated wavy channel the laminar-to-turbulent transition starts at lower values of the Reynolds number, i.e., 1350, and heat transfer is enhanced from 40% to 80% but with a pressure penalization larger than 60%.