Numerical Study On Coupled Heat Transfer Of Thermal Radiation And High-Speed Flow

In many engineering fields related to high temperature heat transfer and flow, thermal radiation and convection usually take place simultaneously and to form coupled heat transfer of radiation and convection. This coupled thermal behavior will cause an important impact on the process characteristics. In a coupled radiation and high-speed flow heat transfer process, not only the interaction of thermal radiation and convection heat transfer but also the combination of heat transfer, fluid flow and mass transfer are involved. So far, our knowledge on mechanism, characteristics and influencing factors of coupled radiation and high-speed flow heat transfer is far from the requirement of developing new technologies in aviation and aerospace engineering fields. The research on coupled thermal radiation and high-speed flow heat transfer is becoming important.On the basis of investigating numerical methods of thermal radiation transfer in participating medium with complex geometry, the analytical model for coupled heat transfer of high-speed flow field with complex structures is established. Three kinds of coupled heat transfer problems of high-speed flow with thermal radiation have been investigated by numerical simulation, which are that on complex structure surface, that in high-speed two-phase channel flow and that in supercritical channel flowThe main work of in this dissertation includes the following four aspects.(1) Investigation on the Monte Carlo method for solving thermal radiation transfer problems. The Monte Carlo method is flexible to complex problems, but it costs large amount of memory space and computational time. Aiming at those characteristics, investigations on elevating the computational efficiency and on diminishing memory request are conducted. As a results, the Bidirectional Monte Carlo method (BDMC) for solving radiative heat transfer in absorbent and scattering medium is improved and a Monte Carlo method with mobile domain (MCMD) is put forward to solve the thermal radiation in medium with large optical thickness, and the computational programs for those two kinds of Monte Carlo methods are developed.For the Bidirectional Monte Carlo method, the characteristics of thermal radiation transfer is combined with the simple random sampling (SPS) and the probability sampling proportionate to size (PPS) respectively to derive the radiative transfer coefficients, which are used for the homogeneous medium and inhomogeneous medium, respectively. The computational performance of the method is evaluated by error analysis and comparison of performance parameters.For the Monte Carlo method with mobile domain, the numerical model and implementation scheme is established and the influences of computational domain and artificial boundary on calculation accuracy are analyzed numerically. All of that provided a powerful method of solving thermal radiation transfer, which is needed for analyzing coupled heat transfer in large optical thickness media.(2) Investigation on the coupled heat transfer of surface radiation with high–speed flow across complex shape of bodies. For the heat transfer process with transient coupled thermal boundary conditions, the concept of wall heat flux function is introduced to decouple the calculation of heat transfer in solid structure from that of the flow field. By employing the domain decomposition calculation and resorting to the heat flux functions database of bounding surface, the analysis model for the coupled heat transfer of surface radiation with high–speed flow across complex shape of bodies is developed. A commercial CFD software is combined with the Monte Carlo method and thermal network method to simulate the transient coupled heat transfer of a high-speed aircraft numerically, and the effects of various parameters are analyzed.(3) Investigation on the coupled heat transfer of thermal radiation with high-speed flow of non-uniform participating medium in channels. By combining FLUENT software with programs for calculating thermal properties, droplet evaporation and radiation heat transfer, numerical simulation of the coupled heat transfer of thermal radiation with high-speed flow of non-uniform participating medium in channels was carried out. By analyzing the temperature field, the liquid phase concentration and the wall heat flux, the influences of thermal radiation properties were investigated. For the thermal design of supersonic combustion chamber, the influence of wall boundary condition was analyzed to give the thermal boundary model with non-uniform temperature distribution. The flexibility of this model for supersonic combustion chamber and the main factors affecting the thermal environment in supersonic combustion chamber were discussed.(4) Investigation on coupled heat transfer in high-temperature cooling channel. For the thermal protection of high-temperature combustion chamber, the Monte Carlo method and the experimental correlations for convection heat transfer were used to numerically simulate the coupled radiation and convection heat transfer of supercritical fuel liquid in a high-temperature cooling channel. The effects of thermal radiation were analyzed and the thermal design method for cooling panel was presented based on the allowed temperature of materials and the non-uniform distribution of heating flux. The reliability of the design method is examined numerically. By the investigations in this thesis, the numerical methods have been developed to analyze the coupled heat transfer of thermal radiation with high-speed flow. The detailed knowledge on the three kinds of coupled heat transfer was obtained, which can give some valuable conclusions and design references.