The Research On Heat Transfer Characteristics Of Carbon Fiber In Low-temperature

Problems involving multiphase flow, multicomponent transport and heat transfer in porous media arise in a number of scientific and engineering disciplines. Those important technological areas include aero-space, oil reservoir engineering, groundwater contamination and remediation, heat pipe technologies, drying processes, particulate materials processing, trickle bed reactors, geothermal reservoirs and so on.Based on the theories of fluid mechanics, mass and heat transfer in porous media, gas-liquid two-phase flow, computational fluid dynamics, the experiment research and the numerical simulation, this thesis researched the heat transfer characteristics of capillary porous media in hypothermia.Firstly, analysis was carried out of the transfer processes in capillary porous media. The emphasis was placed on the deduction of continuous equation, momentum conservation and energy conservation. And three models of the two-phase flow in porous media were presented: SFM separate flow model, two-phase mixture model and the new three-zone model.Secondly, a study on heat transfer characteristic of porous material under the low temperature was introduced. The experimental result testified that the low temperature maintaining time increases obviously after filling in the porous material which changes the heat transfer characteristic. It is found that there is a consanguineous relation between heat transfer characteristic and material density. With the decrease of porous material's density, the heat transfer characteristic is enhanced continuously. And also found that the liquid nitrogen consumption increased after filling in the porous material.Thirdly, Fluent is used to simulate the temperature fields of the transfer processes in capillary porous media.It can be drawn that the wall temperature is minimum at the same time when the porosity is 0.85.And though contrasting the experimental results with simulation calculation it can be concluded that the main influencing factors are the heat leakage of experimental apparatus, heat flux from environment and error of temperature instrument.