| Loop heat pipe(LHP)is a passive heat transfer device which transfers heat by the phase change of the working fluid.The cycle of the working fluid in LHP is driven by the capiliary force with no external drive.LHP has been widely used in the fields of spcacecraft thermal control and high heat flux electronics cooling owing to its many advantages such as high heat transfer capability,low heat transfer resistance,long heat transfer distance,smaller volume and mass,flexible pipeline design and higher reliability.With the development of integrated circuit technique,small space and high heat flux become the new challenge of electronics cooling.In order to satisfy this demand,ultra-thin design has become the key to the research.First of all,the working princeple and research status of LHP are introduced in the thesis.In order to reduce the thickness of the LHP,longitudinal replenishment structure is considered as a possible option.A series of flat LHP equiped with a 6mm thick rectangular evaporator with longitudinal replenishment were designed,fabricated and tested at different gravitational states to study its operation performance and characteristics.It can be obtained that the 6mm LHP can startup and operation to transfer the heat load from 20 W to 60 W in horizontal condition with a minimun resistance evaporator of 0.139?/W and the heat load from 10 W to 150 W under the assistance of gravity with a minimun resistance evaporator of 0.123?/W.It also can be found that there are two distinct disadvantanges of the longitudinal replenishment structure,poor supply competence of working fluid and more significant heat leaks on the heat side,compared with opposite replenishment structure.In order to increase the ability of LHP with longitudinal replenishment evaporator to provide the working fluid,a miniature loop heat pipe with an eccentric evaporator was fabricated and tested at different sink temperature from 0? to 35?.The thickness of the evaporator is 4.5mm.It can oberved that the LHP with an eccentric evaporator have a good response to low heat load.The LHP with an eccentric evaporator can successfully start up at a heat load of 2 W in the horizontal orientation with different sink temperatures ranging from 0 °C to 25 °C.The minimum heat load corresponded to 5 W at the sink temperature of 35 °C.The LHP transported the maximum heat load of 60 W at different sink temperatures from 0 °C to 35 °C with a larger heat load range for stable operation.In this thesis,Comsol and the thermal resistance network method was used to simulate and analyze the startup characteristics in different evaporator structure and the influence of different sink temperature.It can be found from the results that the change of sink temperatur affects the operation performance of LHP by changing the heat exchange enviroment of the compensation chamber.A production scheme of ultra-thin wick with mesh is presented based on sintered biporous wick.The thickness of the wick can be reduced to about 0.5mm.And the porosity and effective thermal conductivity of the ultra-thin wick was test in the research.According to the results,it can be considered that the ultra-thin wick made by new method have similar thermal performance to the sintered biporous wick wich conventional thickness applied in LHP.In this thesis,multiple flat LHP systems with longitudinal replenishment evaporator are presented and tested to study the startup and operation performance.The minimum thickness of the evaporator in these LHP systems is 4.5mm.The characteristics of the LHP with longitudinal replenishment evaporator are analyzed by different method.And a production scheme of ultra-thin wick is presented.The results of this thesis has a guiding significance to the ultra-thin design of the flat LHP. |
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