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The heat transfer and thermochemical reaction are numerically investigated for the solar driven methane dry reforming process, coupling with the solar radiation transport from concentrator to the interior of volumetric reactor. Using a Monte Carlo ray tracing method, the solar radiation concentration with a multi-dish system and absorption by the foam structure in the reforming reactor are simulated. The solar power density distribution in reforming reactor and the optical efficiency of system are determined and compared at different foam structural parameters. Then, an integrated model of transport phenomena is developed to analyze the thermal and chemical performances under different operating conditions. The results indicate that solar radiation absorption and distribution in the reactor are greatly affected by the foam structural parameters, while the optical efficiency has no significant variation. Assumption of the concentrated solar radiation as collimated leads to a temperature deviation of approximately 10%. Besides, the methane conversion increases with increasing porosity and cell size, and decreases markedly with increasing inlet velocity and CH 4 /CO 2 ratio. [ABSTRACT FROM AUTHOR]

The calorific value of syngas can be greatly upgraded during the methane steam reforming process by using concentrated solar energy as heat source. In this study, the Monte Carlo Ray Tracing (MCRT) and Finite Volume Method (FVM) coupling method is developed to investigate the hydrogen production performance via methane steam reforming in porous media solar thermochemical reactor which includes the mass, momentum, energy and irradiative transfer equations as well as chemical reaction kinetics. The local thermal non-equilibrium (LTNE) model is used to provide more temperature information. The modified P1 approximation is adopted for solving the irradiative heat transfer equation. The MCRT method is used to calculate the sunlight concentration and transmission problems. The fluid phase energy equation and transport equations are solved by Fluent software. The solid phase energy equation, irradiative transfer equation and chemical reaction kinetics are programmed by user defined functions (UDFs). The numerical results indicate that concentrated solar irradiation on the fluid entrance surface of solar chemical reactor is highly uneven, and temperature distribution has significant influence on hydrogen production. [ABSTRACT FROM AUTHOR]

Abstract: The distribution of concentrated solar irradiation has a significantly impact on the temperature distribution of porous media receiver. The thermal performance of porous media receiver is investigated by combining the Monte Carlo Ray Tracing (MCRT) method and FLUENT software with user defined functions (UDFs). The MCRT method is used to obtain the heat flux distribution on the fluid inlet surface of porous media receiver. The calculated heat flux distribution is treated as the wall heat flux boundary condition of thermal performance analysis. The local non-equilibrium thermal equation (LNTE) model with Rosseland approximation is used to investigate the temperature distributions. Typical influences of the heat flux boundary condition, radiation heat loss, porosity, emissivity, flow mass and average particle diameter on the temperature distributions are investigated. [Copyright &y& Elsevier]

Abstract: In this paper, Monte Carlo Ray Tracing (MCRT) and Finite Volume Method (FVM) coupling method is adopted to solve the radiation, conduction and convection coupled heat transfer problems of porous media receiver with multi-dish collector. The MCRT method is used to obtain the concentrated heat flux distribution on the fluid inlet surface of porous media receiver. The local thermal non-equilibrium (LTNE) model with concentrated solar irradiation on the fluid inlet surface is used for energy equations. FVM software FLUENT with User Defined Functions (UDFs) is used to solve the fluid phase and solid phase heat transfer problems. The effects of solar irradiance, air inlet velocity, average particle diameter, receiver radius and air properties on the temperature distribution are investigated. [Copyright &y& Elsevier]

Abstract: Material selection of tube receiver is a critical issue to ensure the reliability during its whole service life. In this study, the thermal stress analyses of tube receiver under concentrated solar irradiation condition using various materials are carried out. The concentrated solar irradiation heat flux distribution is obtained by Monte-Carlo ray tracing method and used as boundary conditions of the Computational Fluid Dynamics (CFD) analysis. The CFD analysis will solve the temperature fields and the resulted temperature fields defined at the nodes of CFD analysis meshes are interpolated as input data to the nodes of the thermal stress analysis meshes. The temperature fields, thermal stress fields of various material conditions are obtained in the numerical analysis. The numerical results show that the temperature gradients and effective stresses of the stainless steel and silicon carbide (SiC) conditions are significantly higher than that of the aluminum and copper conditions. The stress failure ratio is introduced to assess the thermal stress level of each material condition. The stainless steel condition has the highest stress failure ratio and the copper condition has the lowest stress failure ratio. From the standpoint of thermal stress, copper is recommended to be the material of tube receiver. [Copyright &y& Elsevier]

Abstract: In the parabolic trough concentrator with tube receiver system, the heat transfer fluid flowing through the tube receiver can induce high thermal stress and deflection. In this study, the eccentric tube receiver is introduced with the aim to reduce the thermal stresses of tube receiver. The ray–thermal–structural sequential coupled numerical analyses are adopted to obtain the concentrated heat flux distributions, temperature distributions and thermal stress fields of both the eccentric and concentric tube receivers. During the sequential coupled numerical analyses, the concentrated heat flux distribution on the bottom half periphery of tube receiver is obtained by Monte-Carlo ray tracing method, and the fitting function method is introduced for the calculated heat flux distribution transformation from the Monte-Carlo ray tracing model to the CFD analysis model. The temperature distributions and thermal stress fields are obtained by the CFD and FEA analyses, respectively. The effects of eccentricity and oriented angle variation on the thermal stresses of eccentric tube receiver are also investigated. It is recommended to adopt the eccentric tube receiver with optimum eccentricity and 90° oriented angle as tube receiver for the parabolic trough concentrator system to reduce the thermal stresses. [ABSTRACT FROM AUTHOR]

Solar-to-fuel is an approach of converting concentrated solar high-temperature heat radiation to high-value chemical fuel, providing sustainable means for large-scale solar energy storage. However, the inefficient space radiation regulation and unclear photo-thermal-chemical multiphysics synergy limit solar to fuel conversion. To effectively improve photo-thermal-chemical conversion, here, we propose a novel idea of using an egg-tray-inspired concave structure in foam solar receiver-reactors for pore-scale space radiation regulation. The multiphysics field coupling model is accurately constructed to truly describe the complex radiation energy conversion process. Experimental and numerical results illustrate that, the proposed egg-tray-inspired concave structure can achieve the better radiation absorption and transmission, multi-field synergy and thermochemical conversion. The solar radiation absorption capacity can be increased by 7.05 %. The improvements reach a maximum efficiency of 3.17 % for photo-thermal conversion and 9.77 % for photo-chemical conversion. The excellent synergistic conversion of solar-to-fuel opens a new pathway towards accelerating energy transition and upgrading. • Egg-tray-inspired concave structure in foam solar receiver-reactor is proposed. • Photo-thermal-chemical multiphysics coupling model is accurately constructed. • Well-designed structures can achieve better pore-scale space radiation regulation. • The excellent synergistic conversion of solar-to-fuel can be enhanced by 9.77 %. [ABSTRACT FROM AUTHOR]

Glazed roof has a convenient place to receive solar radiation, however its bad thermal mass affects the indoor thermal environment and energy consumption. In the present work, the effect of glazed roof filled with phase change material on its thermal mass was experimentally investigated and compared with conventional glazed roof. Experiments with different PCM melting temperatures, PCM layer thicknesses and glazed roof slopes were performed to analyze their effect on the energy consumption and dissatisfaction rate of indoor thermal environment. Also, a general economic analysis was performed to assess the viability of glazing units containing PCM. The results show that the energy consumption of glazed roof filled with PCM is significantly less than that of air, and up to 47.5% of energy saving can be achieved. Payback period can be reduced to 3.3 years by proper selection of PCM melting temperature. Increasing the melting temperature of PCM can effectively decrease the temperature of internal surface of glazed roof, but has a slight influence on the dissatisfaction rate of indoor thermal environment. Increasing the thickness of PCM layer decreases the peak temperature of internal surface of glazed roof and indoor chamber, the energy consumption and the dissatisfaction rate. The highest energy consumption and dissatisfaction rate are obtained at 20° of the inclination angle. [ABSTRACT FROM AUTHOR]