Study On The Viscosity Of Pure Components And Mixed Molten Salts

Solar energy is one of the hottest clean energy sources at present,and the technology of solar thermal power generation is developing rapidly.Molten salt has been widely used in the field of solar thermal power generation.Viscosity is one of the most important thermophysical parameters of molten salt,and it affects the flow status of heat storage medium directly.Exploring new high-performance mixed molten salt is one of the main research directions in the current CSP industry.Due to the variety of mixing methods and ratios of the mixed molten salt,the research on its viscosity is mainly conducted by a large number of experimental measurements.The measuring instruments are expensive,and there are many external factors that affect the accuracy of the experimental measurement.Most of the useless experimental results will not be adopted,which will consume a lot of manpower and material resources and time.Therefore,it is of great significance to conduct in-depth theoretical calculations on the viscosity of the molten salt.In this paper,based on a large number of viscosity experimental data in molten salt related literatures,reliable experimental data of all kinds of commonly used unary molten salt are compared and analyzed by different fitting calculations,and a more accurate fitting calculation formula is obtained.The fitting formula is used to provide viscosity data of pure component molten salt in low temperature functional area for the calculation model of mixed molten salt.For binary molten salt,this paper establishes a theoretical calculation model generally applicable to all kinds of commonly used binary salt.When calculating the viscosity of the binary salt,it only needs to provide the model with basic data such as viscosity and density of the two unary molten salts.The viscosity calculation values of Eyring equation and the calculation results of this model are compared with the reliable viscosity experimental data.The results show that the maximum deviation of the proposed calculation model is-9.306%,it includes the error caused by the experimental measurement and the deviation caused by the density data,while the Eyring equation always obtains larger deviations from the recommended model,and the maximum deviation reaches-14.901%.This paper analyzes a variety of theoretical calculation models suitable for multicomponent mixed molten salt viscosity calculation,and selects the Frankel mixing formula and Kendall-Munrae mixing formula with small calculation deviations for common ternary mixed molten salt.The comparison between the calculated results of the two formulae and the viscosity experimental data shows that the maximum deviation calculated by the KM formula is always less than the Frankel formula,and the average deviation of the KM formula is also smaller,the KM formula is more accurate and stable.In this paper,a large number of theoretical calculations have been done for various types of molten salts,and a series of stable and reliable calculation data and conclusions have been obtained.The results obtained provide reliable preliminary theoretical support for the selection of molten salt and the design of heat transfer and thermal storage systems.