Numerical simulation of laminar forced convection flow with entropy generation analysis in a duct with two expansions - Blocked-off method

In the present paper, numerical simulations of laminar forced convection flow and entropy generation analysis in a 2-D duct with two sudden expansions are investigated. These two expansions are created by four inclined backward facing steps and beget the separation flows and vortex regions. The vortex regions have the significant effects on the heat transfer rates and flow irreversibility. The inclination angle of steps is one of effective parameters on the control of the separation flows, heat transfer rates and flow irreversibility. In this paper, after calculation of velocity fields and temperature distributions, the effect of the step inclination angle on the separated flows, Nusselt number, friction coefficient, entropy generation number and Bejan number is studied. To obtain the temperature distributions and velocity fields, the set of governing equations including mass, momentum and energy equations are solved by the finite volume methods and computational fluid dynamic (CFD) techniques. For simulating the inclined surfaces of steps in Cartesian coordinates, the blocked-off method is used. Also, thermodynamic second law analysis is employed to calculate the entropy generation and flow irreversibility. Finally, the effect of the Brickman number on the entropy generation number and Bijan number is investigated graphically.