| Summary: | 碩士 === 國立交通大學 === 機械工程學系 === 85 ===
In order to realize the important variables during a drying process that influences the producing rate and quality, a numerical analysis is performed in this study to examine characteristics in infrared-radiation drying of cylindrical tubes of porous media. When the tubes are dried by hot air and infrared radiation, the major internal moisture transfer mechanisms considered include 1. capillary flow of water in the fine capillaries and voids; and 2. water vapor flowing through the voids of a porous material by convection and diffusion.
In this study, we consider the drying of cylindrical tubes with finite length. The infrared radiation is uniformly incident upon the outside surface of the tubes, while at both the inside and outside surfaces there exists the convective boundary conditions. The mass diffusion is a function of temperature and moisture content. The convective heat and mass transfer coefficients, specific heat capacity and thermal conductivity are all dependent upon the water content. In numerical analysis, we solve the species equation, energy equation and the radiation transfer equation for the distributions of moisture content and temperature at various drying conditions. We then solve for the drying rate. In terms of the numerical analysis schemes, we utilize the A.D.I method to solve the non-linear transient heat and mass transfer problems and use an interative procedure similar to the method of successive overrelaxation to accelarate the convergence.
It is found in the numerical results that we increase radiant heat flux, Bi, Bim, and the heating area and decrease conduction to radiation parameter to raise the drying rate and decrease the drying time.
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