Engineering Application And Numerical Analysis Of Radiation Heat Transfer In Complex Geometry

This dissertation is concerned with thermal radiation heat transfer in plasma surface alloying process and Czochralski crystal growth. The numerical method of the diffusive-gray enclosure radiation heat transfer in complex geometry was studied, and its application was introduced into these two processes to improve the quality of handsaw and single crystal.The complex geometry always makes the thermal radiation calculation extremely expensive and difficult to satisfy the important physical constraints of reciprocity and closure in computation of the view factor. Uncertainty analysis method was applied to diffuse-gray enclosure radiation problems in this paper. Analyses of the effect of uncertainties in view factors on the radiation heat transfer show that strict enforcement of view factor closure constraint can greatly reduce the sensitivity of the results to the errors in view factors. Based on the review of several view factors rectification algorithms, a simple rectification scheme was adopted to rectify the uncertainties of view factors resulting from obstructions in an enclosure. It was found that this rectification scheme is superior to the others for the reduction of heat flux sensitive to uncertainties in view factors, and the energy conservation can be matched very well.Two and three dimensional mathematical models were developed to simulate the radiation heat transfer in the plasma surface alloying process. The effects of the supplementary cathode, shield, configuration of the frame, emissivities and auxiliary plates on the temperature distribution were numerically studied. It points out: a rational arrangement of supplementary cathode can greatly uniformize the handsaw temperature duo to its double actions of redistributing heat source and reducing thermal radiation;less shield layers at the top of the furnace leads to more uniform horizontal temperature distribution. The horizontal plate between two rows of handsaws can enhance the radiative heat transfer at the center place, and therefore can reduce the temperature difference along both horizontal and vertical directions. The temperature in the frame was measured by thermal couples. The results show that the three-dimensional simulation are reasonable.The global model of CZ crystal growth considering the diffusive-gray enclosure radiation heat transfer was developed in this paper. The effects of the combined convection of the melt and radiative heat transfer on the shape of melt-crystal interface were numerically analyzed. A new method of controlling the melt-crystal interface by changing the local radiative heat transfer is presented.