Viscous dissipation effects on convective instability and heat transfer in plane poiseuille flow heated from below

Abstract

The effects of viscous dissipation on the onset of instability for longitudinal vortices in the thermal entrance region of a horizontal parallel-plate channel are studied by a numerical method for the case when the lower plate is heated isothermally and the upper one is cooled isothermally. Numerical results are obtained for Pr=0.1, 0.7, 10 and 100. It is found that viscous heating has a destabilizing influence. The effect is significant for large Prandtl number fluid (Pr≳10) but is insignificant for small Prandtl number fluid (Pr≲0.7). The viscous dissipation effects on thermal entrance region heat transfer for basic flow (without secondary flow) are also studied.