| The high temperature heat pipe fin (HTHPF) is quite a short heat pipe with liquid metalmedium. The reason why it is named fin is that it can be used to enhance heat transfer as a newtype fin, such as enhancing heat exchanger burner, obtaining heat from boiling bed,strengthening condenser of splitting decomposition and cooling high temperature mineral etc.As a new subject in the heat pipe field, the research of the HTHPF will develop the industryapplication of the heat pipe and enrich the basic content of enhanced heat transfer technology.The paper has a significantly value in theoretical project and industrial application.This work focus on the characteristics and enhanced heat transfer for the HTHPF. Themain contents are as follows.1. Study on the startup characteristics for the HTHPFBased on the molecular motion theory, the theoretical analysis of the vapor from the freemolecular to continuum flow during the startup was carried out. The five periods of the startupprocess was given. The startup limit criterion from frozen state of the HTHPF was proposed,that is FLS >1 . A minimum HTHPF (diameter 25mm, length 60mm) was tested. Theexperimental results show that the transition temperature of the vapor from the free molecularto continuum flow is 460℃ during the startup period. When the HTHPF is positioned at anyinclination with respected to the vertical, the temperatures of the condenser end are obviousdifferent. The larger heat input power yields faster startup. The comparison with the theoreticalanalysis shows that the relatively error of the theoretical and experimental transitiontemperature is about 6.5%, and that the theoretical startup process is coincident with theexperimental analysis. The startup temperature distributions of the HTHPF in the article aresimilar to those in the literature. When the condition of FLS <1 is met, the HTHPFencounters the frozen startup limit.2. Study on the temperature performance of the HTHPFThe thermal resistance model analyzed the complicated heat transfer process in theHTHPF. The calculating valves of the thermal resistance were obtained. The theoretical result IIIABSTRACTindicates that the thermal resistance of the short HTHPF is great under the condition of constantvapor diameter. To examine the temperature change, the transient temperature analysis was alsoperformed. The relation of transient temperature over time was presented by the means oftransient lumped model. It is found that the calculated results are in agreement with theexperimental results.3. Study on the heat transfer limit in the HTHPFThe heat transfer limits in the HTHPF was investigated on the basis of the theoreticalmodel in the literatures. The result shows that heat transfer capability of the HTHPF is mainlyrestricted by sonic and entrainment limit, especially sonic limit at the temperature of about 500℃. But its heat transfer capability is not limited by continuum, viscous, capillary and boilinglimit.4. Study on the flow of working mediumFirstly, a numerical model of vapor flow was developed. The vapor non-isothermality andpressure loss at the evaporator in the HTHPF was obtained. The temperature ratio of theevaporator outlet to inlet is 0.91 and its pressure ratio is 0.57 in the HTHPF with the size of thevapor diameter 18mm and length 300mm. Secondly the pressure drop of the flow liquid in theHTHPF wick was investigated. It is indicates that the pressure drop decreases with theshortening of the length of the HTHPF under the condition of constant vapor diameter.5. Study on the numerical simulation of enhanced heat transfer in the heat exchanger with theHTHPFThe theoretical model of enhanced heat transfer in the exchanger with the HTHPF wasestablished. The FLUENT software was used to simulate numerically the fluid flow and heattransfer in this exchanger. The numerical results show that the standard k ?ε model canreasonably predict the heat transfer characteristics in this exchanger. The contour...
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