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The Math Control Equations of Gas Flow Drying Coupled Field and Runge-Kutta Method Study

Author: ShiJinYan
Tutor: ChenJunRuo
School: Kunming University of Science and Technology
Course: Mechanical Design and Theory
Keywords: Pneumatic drying Mathematical model Heat and Mass Transfer Multiphase flows Runge-Kutta method
CLC: TQ028.67
Type: Master's thesis
Year: 2009
Downloads: 34
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Abstract

Gas flow drying is an approach of convective desiccation. Firstly the heated gas enters into the equipment; the material which needs for being dried is transported by the hot gas. Then the convection is taken place during the whole procedure. Therefore, the moisture will be evaporated away due to the heat transfer. Finally the drying purpose is achieved.According to the macro-Movement, Gas flow drying is the transmission of solid material from one location to another location. the materials was dried in the transmission process, so in fact it is Pneumatic transport process. If the particles were defined as solid phase, the gas flow were defined as the gas phase, the transmission of solid materials,In essence, it is a Multiphase flows problems.According to the heat and mass transfer phenomenon in the pneumatic drying, it is a complicated multiphysics problem. The exchange of heat and mass between the gas flow and the material is carried out during the conveying process. The material which contains the moisture obtains the heat from the hot gas and the temperature will rise. When it achieves the evaporation point, the water will change the phase form liquid to gas and is combined with mixture hot gas. Thus, the particle mass and humidity will decrease. At the same time, the humidity of hot gas will increase and its temperature will go down. All of this will certainly change the pressure, velocity, density, diffusion coefficient and concentration of the fluid field. And this kind of change will definitely influence the water evaporation phenomenon again.Based on the knowledge about pneumatic drying, a mathematic model for impulse dryer has been established. The model includes seven parameters and their corresponding ordinary diferential equations, viz. velocity、moisture contents and temperature of particles, velocity、moisture contents and temperature of of air flow. According to the characteristics of the model equations, the four-order Runge-Kutta integration method was used to solve them.We got the impact of different parameters on the air drying process Expressed the impact of particle diameter, particle temperature, particle velocity, particle moisture content, gas temperature, gas velocity, solid-air drying process than the impact on the curve.The research work of the paper relates to some subjects like computational fluid dynamics, pneumatic conveying, multiphase flow and computational engineering. It would be guidance for the numerically solving multiphase flow problem and reference to the industrial drying applications

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