Pressure work and viscous dissipation in the equations of thermal convection in a vertical channel

Equations for fully developed flow in a vertical channel have been solved, taking into account viscous dissipation, and using formulations with and without pressure work. Perturbation solutions are used to distinguish the effects of viscous dissipation from pressure work. Viscous dissipation has very little effect on free convection flows driven by temperature differences or heat fluxes at the channel walls, but it may play a major role in forced convection.