Numerical simulation of 2D turbulent natural convection of humid air in a cavity filled with solid objects.

Natural convection flow in enclosures containing solid objects is important in the design of a wide range of industrial and engineering applications. Numerical calculations were performed for low turbulence double-diffusion convection for humid air inside a rectangular cavity with an aspect ratio of 2:1(height/width) and partially filled with disconnected solid cylindrical objects occupying 15% of the total cavity volume. The vertical walls are maintained at 1.2 and 21IZC and a Rayleigh number of the fluid mixture based on the height of the vertical wall is 1.45 × 109. In the computations, turbulent fluxes of momentum, heat and mass were modelled by a low-Re (Launder-Sharma) k-< eddy diffusivity model. Radiation equation was discretised using the discrete ordinate method. Detailed analysis was performed on the flow and heat transfer and on the turbulence quantities within the cavity. The effect of 2D simplification of inherently 3D radiation modelling was carefully scrutinised and calculations carried out with an equivalent emissivity. Variations of average Nusselt number and buoyancy flux are analysed. Profiles of turbulent kinetic energy and turbulent viscosity are studied in detail to observe the net effect on the intensity of turbulence caused by the interactions of radiation with double-diffusive natural convection heat and mass transfer. Particular emphasis was placed on quantifying the proximity of the solid objects to the active walls. It has been found that turbulence is suppressed as the objects get closer to the walls.

[1]  Denis Flick,et al.  Experimental and numerical study of heat and moisture transfers by natural convection in a cavity filled with solid obstacles , 2009 .

[2]  A. Lachemet,et al.  3d-Transient modeling of heat and mass transfer during heat treatment of wood , 2011 .

[3]  Draco Iyi,et al.  Interaction effects between surface radiation and double-diffusive turbulent natural convection in an enclosed cavity filled with solid obstacles , 2012 .

[4]  Nicolas Rouger,et al.  NATURAL CONVECTION IN AN AIR-FILLED CAVITY: EXPERIMENTAL RESULTS AT LARGE RAYLEIGH NUMBERS. , 2011 .

[5]  Natural convection with unsaturated humid air in vertical cavities , 1997 .

[6]  Masud Behnia,et al.  Combined radiation and natural convection in a rectangular cavity with a transparent wall and containing a non‐participating fluid , 1990 .

[7]  Brent Griffith,et al.  A Momentum-Zonal Model for Predicting Zone Airflow and Temperature Distributions to Enhance Building Load and Energy Simulations , 2003 .

[8]  B. Launder,et al.  Application of the energy-dissipation model of turbulence to the calculation of flow near a spinning disc , 1974 .

[9]  Dennis L. Loveday,et al.  CFD modelling of double-skin facades with venetian blinds , 2007 .

[10]  J. Orfi,et al.  Laminar mixed convection of humid air in a vertical channel with evaporation or condensation at the wall , 2004 .

[11]  Denis Flick,et al.  Experimental study of heat transfer by natural convection in a closed cavity: application in a domestic refrigerator , 2005 .

[12]  Wei Liu,et al.  Numerical and experimental analysis of convection heat transfer in passive solar heating room with greenhouse and heat storage , 2004 .

[13]  Manab Kumar Das,et al.  Conjugate natural convection heat transfer in an inclined square cavity containing a conducting block , 2006 .

[14]  Tassos G. Karayiannis,et al.  Low turbulence natural convection in an air filled square cavity: Part II: the turbulence quantities , 2000 .