| Based on the flat micro heat pipes of different sizes,which are taken as the research objects,the optimization tests of the construction and application parameters are carried out respectively.According to the optimized parameters,the micro heat pipe flat plate solar collector was constructed and tested its thermal performance.On the basis of the comparison and analysis of the main factors that influence the performance of the plate micro-heat pipe,a series of evaluation parameters which can reflect its start-up,iso thermal and heat transfer performance are summarized.The test platform for the performance of plate micro heat pipe with different application conditions was designed and built.Completed isothermal,start up and heat transfer performance test with different flat micro heat pipes through experiments.And comparative analysis showed that the preferred flat micro heat pipes had the following geometric dimensions: length 930 mm,width 50 mm,and thickness 3 mm.The structural parameters of the preferred plate micro-heat pipe are: the upper and lower wall thickness is 0.45 mm,the thickness of the adjacent side wall of the micro-channel is 0.35 mm,the cross-sectional area of the micro-channel is 6.09 mm2,and the number of micro-channels is 15.The overall performance of the acetone microplate heat pipe is superior to that of the methanol.Combined with the application of the flat micro heat pipe in the solar collector,the influence of different application parameters on the performance of the flat micro heat pipe was studied through comparative experiments.Under different placement angles,the heat transfer performance of flat micro heat pipes is different.When the plate micro-heat pipe was placed in the range of 30 ° ~ 60 °between the horizontal and placing direction,its heat transfer capacity is relatively better.The dimensionless ratio of evaporative and condensation length,Lec,was defined and it was experimentally determined that when the Lec was between 1.16 and 1.66,the acetone heat medium plate heat transfer capacity was relatively better.The bent angle of the condensing section should be within 60°,and that time the flat micro heat pipe can start normally and have good phase change heat transfer capacity.The enhanced heat transfer in the condensing section make the vapor of the working fluid condense rapidly,accelerating the gas-liquid two-phase circulation flow in the micro heat pipe,which effectively increased the limit heat flux density and improved the heat transfer performance of the micro heat pipe.According to the construction principles of the micro heat pipe flat solar collector and the optimized parameters,a new micro heat pipe flat solar collector with a size of 2000×1000×90 mm was designed.The energy balance equation and the total heat loss qualitative analysis method were described.And designed the process flow for the production of the micro heat pipe flat solar collector.Finally,according the national code,finished the transient efficiency test and showed that the instantaneous efficiency intercept and slope of the micro heat pipe flat-plate solar collector sample 1 and 2,all are better than the national standards of 12.08% and 3.38%,17.5% and 4.18% respectively;the instantaneous efficiency of the sample 2 is cut.Micro heat pipe flat solar collector have significant performance improvement over ordinary flat-plate solar collector. |
