Influence of the dynamic boundary conditions on natural convection in an asymmetrically heated channel

• Natural convection of air in a vertical or inclined asymmetrically heated channel.
• Influence of inlet-outlet boundary conditions on the flow structure.
• Parametric study of the existence of a reverse flow.
• Heat transfer at the heated wall.

The present paper is concerned with the results of the numerical investigation of unpermanent laminar, natural convection in an asymmetrically heated inclined open channel (i = 0,45,60 and 75∘) with walls at uniform heat flux (qw = 10,50,75 and 100  W m−2). Two methodological approaches have been adopted to investigate the air flow in these configurations: 2D and 3D description, and four sets of inlet-outlet velocity-pressure boundary conditions have been considered. Significant differences are observed in the flow dynamics between 2D and 3D results. The numerical results are compared with the experimental data and a good agreement is obtained when a local pressure boundary condition is applied at the inlet/outlet sections in the 3D case. A generalized correlation for the average Nusselt number is then obtained from numerical results. This correlation covers a wide range of the modified Rayleigh number and aspect ratio values (Ramcos(i) varying from 1.71 × 104 to 3.60 × 106 and 6.5 < H/b < 12.8).