| Under the background of rapid economic development in China,energy shortage and environmental pollution are becoming more and more prominent.Nuclear energy,a clean energy with low resource consumption and strong power generation capacity,is an electric power project that must be vigorously developed at present.The traditional uranium-based nuclear power plant is facing an increasingly tight situation of uranium resources.Therefore,strategic priority research program of Chinese Academy of Sciences has carried out research on the molten salt reactor with thorium as the nuclear fuel.The design and development of 2MW thorium molten salt reactor system with liquid fuel(TMSR-LF1)is being carried out,in which the molten salt exchanger(hot side is FLi Be,cold side is FLiNaK)is the key equipment to realize energy conversion.In order to improve the compactness and thermohydraulic performance of molten salt heat exchangers,the thermal characteristics of plate and plate-fin heat exchangers are numerically simulated in this paper,which provides a reference for the design of plate and plate-fin heat exchangers.Firstly,according to the design requirements of TMSR-LF1 and relevant national industry standards,the types of plate and fin are designed and simulated to optimize their heat transfer or flow characteristics.Herringbone,parallel,vertical corrugated plate,rectangular,streamline and improved streamline fin,are designed and constructed.The numerical results of each type are analyzed and discussed,and these models are compared by three methods: pressure drop,unilateral convection heat transfer coefficient and heat exchange performance evaluation criterion.Finally,the analysis method of fluid-induced vibration of heat exchanger is explored from the point of engineering practicability.Based on the experimental platform of molten-salt-air tube and shell heat exchanger of Shanghai Advanced Research Institute,Chinese Academy of Sciences,the two-way fluid-structure interaction simulation is carried out on the experimental model.Therationality and feasibility of the numerical simulation method are verified by experiments,which provides a calculation method for the engineering application of fluid-induced vibration problem in plate or plate-fin heat exchangers in the future.When the inlet temperature of molten salt is 833-923 K and the inlet velocity is0.3-0.5m/s,the results show that the pressure drop of fin about 3 times larger than that of plate,while the heat transfer coefficient increases by about 35 per cent.Among the six types,the streamline fin has the highest convection heat transfer coefficient,the whole heat exchanger is most compact.The vertical corrugated plate has the smallest pressure loss and is suitable for high velocity operation.For comprehensive evaluation of heat transfer performance index,vertical corrugated plate is the highest,which is about 17% higher than the second one,and about 44% higher than the average index of plate fin type.Compared with the shell and tube heat exchangers under the same heat transfer coefficient,the pressure drop of plate-fin heat exchangers is about 1/4 and that of plate heat exchangers is less than 1/10.The relationship curve of acceleration of heat exchanger tube between calculated value and experimental data are consistent,the error is in the range of about-12% to15%,which shows that it is feasible to analyze the fluid-induced vibration of heat exchanger by using the method of two-way fluid-structure interaction. |
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