Heat Transfer Characteristics Research On A Volumetric Solar Receiver With Single-Layer Or Double-Layer Porous Media

Porous media solar receiver is a key component of the solar power technology.According to local thermal non-equilibrium model,analytical solutions are obtained for the air temperature,skeleton temperature,air pressure and receiver efficiency along the receiver.The effects of the geometry(including porosity and pore diameter)on the performance of the receiver are researched.For a volumetric solar receiver with single-layer porous media(single-layer receiver),this study investigates the performance of a single-layer receiver with four radiative transport models: model which ignore inner radiation of skeleton(Model A),Rosseland approximation(Model B),a uniform heat source model(Model C)and radiatiave transport in receiver meets Beer's law(Model D).Analytical solutions of four models are obtained for the air temperature,skeleton temperature,air pressure and receiver efficiency by using a local thermal nonequilibrium model.The effects of the porosity,the pore diameter and the thermal conductivity of the porous skeleton on the performance of the receiver are researched.The results show that the maximum temperature of the receiver is located in the inlet of the receiver for Model A and Model B,and located in the outlet of the receiver for Model C,and located in the inner of receiver or in the outlet of the receiver for Model D.Subsequently,the receiver efficiency depends on the porosity,the pore diameter and the thermal conductivity of the porous skeleton,and receiver efficiency of Model C is highest in the four model discussed.For a volumetric solar receiver with double-layer porous media(double-layer receiver),the Rosseland approximation is applied to account for the radiative heat transfer through the double-layer receiver.Analytical solutions are obtained for the air temperature,skeleton temperature,receiver efficiency and air pressure along the receiver by using a local thermal non-equilibrium model.The effects of the increasing-porosity or decreasing-porosity design and increasing or decreasing design of pore diameter on the performance of the double-layer receiver are researched.The results show that the first porous layer has a significant effect on the solid inlet temperature,air outlet temperature and air pressure drop.Subsequently,compared with the increasing-porosity design,the decreasing-porosity design tend to achieve higher rceiver efficiency and higher solid inlet temperature.What's more,the increasing design of pore diameter can achieve lower solid inlet temperature and higher rceiver efficiency compared to the decreasing design of pore diameter.Lastly,the pressure drop can be reduced by increasing the thickness of high porosity region or increasing the thickness of high pore diameter region.