Numerical Study And Optimization On The Optical And Thermal Performance Of Cavity Receiver In Dish Solar Thermal Power Generation System

With the development of human society, and continual improvement in people’s livingstandards, energy demand will grow substantially. However, the energy development andutilization are influenced and restrained by environment, resources, technology, economy, etc.The global energy crisis and the deterioration of the environment have become increasinglyprominent. Developing and using renewable, clean energy, actively looking for energy savingtechnologies are the response to the energy crisis and ecological crisis. As an endless andunlimited energy, solar thermal energy will become an important new energy in this century.Solar thermal power generation is an important way of solar thermal utilization. Atpresent, solar power tower, parabolic trough and dish system are three main types of solarthermal power generation system. Their characteristics are compared with each other in thisthesis, application and several key technologies are analyzed specially. The composition andprinciples of the dish solar thermal power generation system are present in this thesis, and thelatest progress in research and development trend are introduced.Cavity receiver is installed in the focus of dish concentrator. It is used to collect solarenergy and convert solar energy into thermal energy. Therefore, the optical and thermalperformance of cavity receiver has a significant impact on performance of the whole thermalpower generation system. The shape and opening size of the cavity receiver has a direct effecton its optical and thermal performance. In this thesis, the heat loss (such as loss of reflectedlight, radiation loss, convective heat loss, thermal conductive loss) from solar energy tothermal energy is analyzed in theory. The theoretical calculation method of the heat loss isalso provided. At the same time, the continuity equation, energy equation, momentumequations and turbulence equations of the fluid in the cavity receiver are established todescribe the internal flow field distribution.On this basis, the numerical simulation of cavityreceiver are carried out by an optical software TracePro and a computational fluid dynamicssoftware FLUENT. Main study includes the following areas:The3D geometrical model for four typical receivers, such as spherical, cylindrical,conical, flat-topped cone, is established. Under the same concentrator and solar radiationintensity, the optical efficiency of the four kinds of cavity receivers are calculated by usingoptical software TracePro, and their radiation intensity distribution are also calculated andanalyzed. The results indicate that spherical receiver has the best optical properties.For spherical receiver, six3D geometrical models of spherical receivers with differentopening ratio (D/d) are built. We use TracePro to calculate optical efficiency of the six receivers under the same concentrator and solar radiation intensity. At the same time, theirthermodynamic efficiency of the receivers are also calculated and compared by usingFLUENT. The results show that the spherical cavity receiver with1<D/d<1.5has higheroverall efficiency.Through the results of this research, it provides theoretical analysis method andnumerical analysis method for the selection，disign，and optimization of the cavity receiver.