DEVELOPMENT OF LAMINAR MIXED CONVECTION IN A HORIZONTAL SQUARE CHANNEL WITH HEATED SIDE WALLS

A finite element code is used for detailed analysis of mixed-convectio n flow in a horizontal channel heated from the side walls. The Reynold s number typically is Re = 500, and the Grashof number varies around G r = 10(5), Firstly, the numerical code is validated by a quantitative comparison with results of particle-tracking experiments for the veloc ity and liquid crystal measurements for the temperature. It is conclud ed that the agreement between the numerical and experimental data is s atisfactory and that the finite element approximation employed can be used in analyzing mixed-convection flow problems in complex geometries . Secondly, the velocity and temperature fields an further described b y means of isovelocity and isotemperature lines. The results are quant ified by the relative kinetic energy of secondary flow, the Fanning fr iction factor, and the Nusselt number as a function of the streamwise position. It seems that the resulting secondary flow induced by buoyan cy forces causes a substantial increase in heat transfer, knowledge of which is of importance for the design of compact heat exchangers. (C) 1998 Elsevier Science Inc. All rights reserved.