Investigation On Multiphvsics Coupling Processes And System Integration Of The Concentrated Solar Thermal Energy

Solar energy is considered by many to be a promising energy in the 21th century due to its infinite reserves and cleanness nature. It may be one of most effective routes to solve the energy problems caused by exploitation and utilization of the fossil fuels. Large scale solar thermal power generation can overcome the drawbacks of solar energy such as the low energy density, the intermission and the unequal distribution, solar thermal power generation mainly includes concentrating solar thermal power and solar thermalchemical power genration. The parabolic trough linear receiver and solar receiver/reactor are key components of solar thermal power generation system. Due to the characteristic of the concentrator, the solar energy flux distribution is non-uniform, leading to non-uniform circumferential temperature distribution, which affects the performance of the receiver/reactor. Supported by the National Natural Science Foundation of China and the National Basic Research Program (973 Program) the researches mainly including the performance analysis of the parabolic trough solar receiver and a multiphysics coupling simulation of the mid-and-low temperature solar receiver/reactor, have been carried out in this dissertation.1. Experiment and simulation study of the density of the solar flux. The solar energy flux distributions on the outer surface of the absorber under off-design conditions have been texted. A three-dimensional optic-thermal-stress coupling model was implemented. The heat transfer process in a parabolic trough solar collector system (PTC) and the impacts of the key operation parameters on the performances of the PTC were numerically investigated. The performances of a parabolic trough solar collector system using molten salt as heat transfer fluid were also investigated.2. A multiphysics coupling mathematical model that incorporates the mass, fluid flow, energy conservation governing equations and the kinetic model of the methanol steam reforming is developed to investigate the performances of the mid-and-low temperature solar receiver/reactor. The factors influencing the hydrogen production and the temperature distributions of the catalyst bed, including the diameter of the receiver/reactor tube, the non-uniform distribution of the solar energy and the porosity of the catalyst bed, are numerically investigated. The non-uniform distribution of the solar flux has an obvious influence on the cross-sectional temperature difference of the receiver/reactor tube and the catalyst bed, and the temperature rise of the catalyst bed, while has a slight impact on the methanol conversion and the collector efficiency.3. A new design solar receiver/reactor was proposed by changing the collector area, the diameter of the receiver/reactor and the length of the receiver/reactor along the flow direction to make the solar energy match the chemical reaction in the catalytic bed. The new design solar receiver/reactor reduces the heat loss and improves the performance of solar receiver/reactor. Compared to the traditional receiver/reactor, the methanol conversion of the new design receiver/reactor increases by 9 percent points under typical conditions.