| With the growing energy crisis in China,The application of solar medium-high temperature heat utilization technology in industry is an inevitable trend,which can provide high temperature heat energy.The heat transfer process of the through-type vacuum heat pipe is analyzed,and the one-dimensional steady-state heat transfer model of the heat pipe is established,in this paper.Simultaneously,the simulation results are compared with the experimental values,and the main reasons of the difference are analyzed.In order to improve the collector efficiency of the through-type vacuum heat collector,reduce the circumferential temperature gradient of the metal heat-absorbing tube,prolong the use of the vacuum collector,and reduce the thermal stress,in this paper,two kinds of enhanced heat transfer methods are proposed,and two corresponding new vacuum heaters are designed.The thermal performance of the traditional vacuum collector tube and two kinds of new vacuum heat collectors is studied experimentally under different experimental conditions,including the heat collecting efficiency and the circumferential temperature gradient of the metal heat pipe,and the heat transfer effect of two kinds of enhanced heat transfer methods is analyzed and compared on the basis of the experimental results.In order to meet the practical industrial application,a trough solar medium-high temperature steam generation system is designed.Based on the solar thermal power generation cost under Sunlab and Sargent&Lundy,the basic concept and calculation formula of Solar of Level Energy Cost are put forward,and the influence of annual radiation and system life on SLEC is analyzed.On the basis of verifying the mathematical model,the simulation results show that there are some differences between the simulated and experimental values.The main reasons for this difference are as follows:Firstly,the outer wall of the heat pipe in numerical simulation is uniform,which is different from the actual experiment,and the condition of the numerical simulation is ideal.At the same time,there is a certain system error,making the actual experiment Value less than the analog value in the production and construction of the system;Finally,the method of the vacuum collector tube production may also be one of the reasons for the large difference between the experimental and analog values.Under various experimental conditions,the heat collection efficiency of the vacuum tube collector with high flux coating and twined wire coil inserts are significantly higher than that of the traditional vacuum heat collector,slightly higher than that of the vacuum heat collector with only high flux coating.In the liquid phase area,compared with the traditional vacuum tube,the heat collection efficiency of the vacuum tube collector with high flux coating and twined wire coil inserts increases by about 26.2%,and the circumferential temperature gradient decreased by about 6.4 ℃;By contrast,the heat collection efficiency of the vacuum tube collector with only high flux coating increased by about 18%,and the circumferential temperature gradient decreased by about 3.6 ℃.In the gas-liquid two-phase zone,the heat collection efficiency of the high flux coating and twined wire coil inserts vacuum tube collector and the only high flux coating vacuum tube collector is about 34%and 22.7%higher than that of the traditional vacuum tube,respectively.But the circumferential temperature gradient is 9.8℃ and 4.8℃ lower than that of the traditional vacuum tube,respectively.In the gas phase area,compared with the traditional vacuum tube,the heat collection efficiency of the high flux coating and twined wire coil inserts vacuum tube collector and the only high flux coating vacuum tube collector increased by 22%and 21.65%,respectively;and the circumferential temperature gradient decreased by 22.5℃ and 8.3 ℃ respectively.When the heating scale is 1000 MW,the investment cost of the direct trough solar medium-high temperature steam generation system is expected to be reduced to 631.30$/kW,and the maximum amount of coal saving can reach up to 36.4 kg/s.With the increase of the annual radiation time and the system service life,SLEC is both obviously reduced. |
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