Numerical analysis of Grashof number, Reynolds number and inclination effects on mixed convection heat transfer in rectangular channels

Mixed convection heat transfer in rectangular channels has been investigate d computationally under various operating conditions. The lower Surface of tile channel is Subjected to a uniform heat flux, sidewalls are insulated a nd adiabatic, and tile upper Surface is exposed to tile Surrounding fluid. Solutions were obtained for Pr = 0.7, inclination angles 0 degrees less tha n or equal to theta less than or equal to 90 degrees, Reynolds numbers 50 l ess than or equal to Re less than or equal to 1000, and modified Grashof nu mbers Gr = 7.0x10(5) to 4.0x10(6). The three-dimensional elliptic governing equations were solved using a finite volume based Computational fluid dyna mics (CFD) code. From a parametric study, local Nusselt number distribution s were obtained and effects of channel inclination, Surface heat flux and R eynolds number on the onset of instability were investigated. Results obtai ned from the simulations are compared with the literature and a parallel co nducted experimental study, from which a good agreement was observed, The o nset of instability was Found to move upstream for increasing Grashof numbe r. On the other]land, Onset of instability was delayed for increasing Reyno lds number and increasing inclination angle. (C) 2001 Elsevier Science Ltd.