3-D Numerical Simulation Analysis of Heat Transfer Efficiency of the Heat Pipe as related to Its Porous Medium

• Main Authors: Bo-Chao Huang, 黃柏超
• Other Authors: Tsung-Leo Jiang
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/70632824240130915497

碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 93 === 　The heat pipe is a simple and power-free device characterized by a high heat transfer capacity and a short thermal response time. It has been one of the most important heat-dissipation elements for the thermal management of various electronic and satellite systems. This thesis aims to present a study in which the porous-medium parameters on the heat transfer efficiency of the heart pipe are investigated. By adapting the KIVA-3 software and adopting the Darcy-Brinkman-Forchheimer model, a numerical simulation model for the three-dimensional, transient, and multi-phase flow is developed in order to conduct the investigation. Numerical results thus obtained show that the porous-medium increases the vapor flow velocity and meanwhile reduces the pressure and temperature of the heat pipe. It also patently shortens the time for the heat pipe to reach a steady state. A higher effective thermal conductivity of the material may reduce the temperature, pressure and the thermal resistance of the heat pipe. However, it will raise the velocity of the vapor flow. More heat input results in a higher temperature, pressure and density in the vapor flow. The resulted liquid temperature is also higher. A smaller diameter of the porous medium will reduce the permeability and increase the pressure difference of liquid from condenser section to evaporator section, but will not affect the temperature. When a capillary structure is organized by porous-medium of different diameters but with single arrangement, the effective thermal conductivity will not undergo change due to the size of porous-medium, but the permeability will be affected. Accordingly, the particle size of porous-medium will influence the distribution of both the liquid pressure and the velocity of the liquid flow, but it will not influence the temperature, the vapor pressure, and the vapor velocity. On the contrary, when the capillary structure with porous-medium of identical diameter but with different arrangements, both the effective thermal conductivity and the permeability will undergo change. Consequently, the pressure, the velocity and the temperature will be affected. However, the heat transfer efficiency of the heat pipe is still influenced primarily by the porosity. Furthermore, this thesis compares the numerical results predicted by two different porous-medium models of Darcy and Darcy-Brinkman-Forchheime to be insignificant. Although D-B-F model takes a non-linear type of second steps of inertia into account, the influences on the speed, pressure, and temperature are found respectively.