Abstract
A local non-thermal equilibrium heat transfer analysis was conducted for an investigation of the heat transfer performance of silicon carbide ceramic foam as a possible volumetric solar receiver. Turbulent heat transfer takes place from the receiver solid phase to the air as it passes through the porous receiver. Radiative heat transfer was coupled with conduction and turbulent convection using the P1 model which describes radiative heat transfer in optically thick media reasonably well. The two energy equations written in one-dimensional form for the air and foam were combined with the irradiation transport equation based on the P1 model. Analytic solutions are obtained for the developments of air and ceramic temperatures as well as the pressure along the flow direction derived under the low Mach approximation. The solutions serve as a useful tool for designing a novel volumetric solar receiver of silicon carbide ceramic foam.
Highlights
A solar volumetric receiver is required to have the resistance to temperature as high as 1000 degree Celsius, high porosity for sufficiently large extinction volume such that the concentrated solar radiation penetrates through the receiver, high cell density to achieve large specific surface area and sufficiently high effective thermal conductivity to avoid possible thermal spots
In order to overcome the problems associated with thermal spots and flow instabilities, we would like to study fluid flow and heat transfer characteristics in silicon carbide ceramic foams based on the analytical expressions of pressure and temperature fields within a solar volumetric receiver
The complete set of analytical solutions, which fully considers the combined effects of turbulence, tortuosity, thermal dispersion, compressibility on the convective, conductive and radiative heat transfer within a ceramic foam receiver, is presented based on the two-energy equation model of porous media. Both the Rosseland approximation and the P1 model are applied to account for the radiative heat transfer through the solar receiver, while the low Mach approximation is exploited to investigate the compressible flow through the receiver
Summary
A solar volumetric receiver is required to have the resistance to temperature as high as 1000 degree Celsius, high porosity for sufficiently large extinction volume such that the concentrated solar radiation penetrates through the receiver, high cell density to achieve large specific surface area and sufficiently high effective thermal conductivity to avoid possible thermal spots. The complete set of analytical solutions based on the two-energy equation model of porous media was presented, so as to fully account for the combined effects of tortuosity; thermal dispersion and compressibility on the convective, conductive and radiative heat transfer within a ceramic foam receiver In their analysis, the Rosseland approximation was applied to account for the radiative heat transfer through the solar receiver. This study appears to be the first to provide the complete set of analytical solutions based on the twoenergy equation model of porous media [9], fully accounting for the combined effects of turbulence, tortuosity, thermal dispersion, compressibility and radiative heat transfer within a ceramic foam receiver
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