Laminar and turbulent natural convection heat transfer in Trombe wall channels
Abstract
The natural convective heat transfer and air movement in a Trombe wall solar passive system has been studied analytically and numerically. Three Trombe wall channel geometries including the parallel channel with axial inlet and exit, parallel channel with side vents and Trombe wall channel coupled to the room have been considered. For the parallel channel with axial inlet and exit geometry, a momentumintegral method has been used to solve parabolic governing equations for two dimensional laminar flow. This formulation leads to a second order ordinary differential equation for pressure defect in the Trombe wall channel. The solution of this equation leads to prediction of velocity, temperature and pressure fields, and Nusselt number correlations that are in good agreement with previously reported finite difference solution of natural convection boundary layer equations. For the sidevented channel case, results are obtained for both two dimensional laminar and turbulent natural convective flow regimes. Due to presence of recirculating flow patterns in this geometry, full NavierStokes equations in twodimensions are employed. The turbulent flow characteristics are modeled by a twoequation (kepsilon) model. The governing equations for steady laminar as well as turbulent flows are solved by a finite volume technique that uses the quadratic upwind differencing scheme to discretize nonlinear governing equations to form algebraic equations which govern physical variables at the various numerical grid points. The coupled algebraic equations are solved by a semiimplicit algorithm known as SIMPLER. Flow patterns, isotherms and heat transfer characteristics are obtained for aspect ratios of 10 and 20, and Grashof number ranging from 1.4 x 10(exp 3) to 1.4 x 10(exp 8). The effect of the free pressure boundary location of flow characteristics is also analyzed. Results show that the mass flow rates induced and net energy delivered by the system is governed by the channel Grashof number and the channel vent size. The total vent loss coefficient for the sidevented cavity shows a minimum at Gr = 1.4 x 10(exp 4) for which the dimensionless mass flow rate also shows a maximum value.
 Publication:

Ph.D. Thesis
 Pub Date:
 January 1992
 Bibcode:
 1992PhDT........53C
 Keywords:

 Convective Flow;
 Convective Heat Transfer;
 Heat Transfer;
 Laminar Flow;
 Trombe Walls;
 Turbulent Flow;
 Turbulent Heat Transfer;
 Walls;
 Algorithms;
 Boundary Layer Equations;
 Flow Distribution;
 NavierStokes Equation;
 Nusselt Number;
 Parabolic Differential Equations;
 Two Dimensional Flow;
 Velocity Distribution;
 Fluid Mechanics and Heat Transfer