NATURAL-CONVECTION HEAT-TRANSFER IN VERTICAL CHANNELS WITH AND WITHOUT TRANSVERSE SQUARE RIBS

Experiments were performed to determine heat transfer data for the nat ural convective flow of air in vertical channels with one surface roug hened by transverse square ribs and the opposite surface smooth. Unifo rm wall temperature conditions were imposed on the ribbed side, while the smooth side remained unheated. Additional experiments were carried out in vertical channels without ribs, under the same channel geometr y and thermal conditions. A schlieren optical technique was used to re construct the thermal field and to obtain distributions of heat transf er coefficients. The presence of ribs was found to alter heat transfer considerably, causing thermally inactive regions just upstream and do wnstream of each protrusion. Consequently, the heal transfer performan ce of the ribbed channel turned out to be lower than that of the corre sponding smooth channel. (C) 1997 Elsevier Science Ltd. All rights res erved.