Study On Flow And Heat Transfer Characteristics In Evaporator Of Separate Type Heat Pipe

On a global energy crisis basis and a global need of protecting environment from disrupting, exploiture on utilization of solar energy is a great stratagem for human being's better development. Separate type heat pipe has high thermal conductivity, simple structure, convenient arrangement, reliable work, even temperature and so on the merit, which all cause it to have a extremely widespread application prospect in utilization of solar energy.Firstly, this article makes a summary to the research about separate type heat pipe, with emphasis, introduce the domestic and foreign researchers'research result on liquid-filled ratio, heat transfer performance and flow characteristics of evaporation segment in separate type heat pipe, according to research insufficiency of separate type heat pipe in use of solar energy, one kind of separate type heat pipe using low boiling point matter as working liquid is proposed for actual utilization of solar energy.Secondly, after pre-digestion for physical model and one dimension hypothesis, on the bases of three basic equations such as mass equation, momentum equation and energy equation and fundamental theory of flow boiling heat transfer, a model of flow boiling heat transfer for separate type heat pipe was established using Shah model,J.C.Chen model and Gungor-Winterton model respectively,it was discovered that J.C.Chen model was more suitable for separate type heat pipe than others after comparative analysis among J.C.Chen model, Gungor-Winterton model and Shah model.Then,a separate heat pipe using R22 as working liquid was studied by means of experiment, its heat transfer performance was well studied by a series of experiments with heat flux from 1 kW/m2 to 5kW/m2,working temperature from 30℃to 60℃and gradient of evaporation segment from 10°to 90°. The effect on heat transfer performance caused by heat flux,gradient and liquid-filled ratio of evaporation segment was deeply studied. The result showed that this heat pipe could start-up in a short time at low heat flux, the wall temperature along with the axis way of evaporation segment distributed equally,these showed that this kind of heat pipe has good capability of start-up,the appropriate liquid-filled ratio was more than 80%,within the scope of testing parameters,heat flux,gradient and liquid-filled ratio of evaporation segment had little impact on its heat transfer performance.Finally, according to the founded model, use program wrote by Matlab to research on evaporation segment of separate type heat pipe using R22 as working liquid through numerical computation method. The mostly purpose is to investigate how independent variables as heat pipe diameter, heat flux, working temperature, gradient of evaporation segment effect on dependent variables as working liquid temperature and pressure, mass and section gas rate, gas and liquid phase velocity, grades of friction pressure drop, flow boiling heat transfer coefficient, outer wall temperature of evaporation segment. By contrast analysis, experimental outer wall temperature of evaporation segment was approximately consistent with the numerical computational result,by which the founded model was testified to be right to a deep extent. It was concluded that the founded model could be applied with design and analysis of separate type heat pipe, the numerical computational result made instructional sense for practice.