一种热管熔盐堆塔式温差发电系统设计及分析

Design and analysis of a heat-pipe molten salt reactor tower thermal power generation system

熔盐堆作为第四代先进反应堆的重要堆型之一,以高沸点熔盐为核燃料熔融载体,具有高温输出、常压操作等特点。而基于温差发电的热管熔盐堆,兼具了熔盐堆、热管和温差发电的优势,具有输出温度高、热电转换效率高、结构简单及安全可靠等优点,在能源系统领域具有极大的优势,是外太空及深海探测任务的理想能源。但因堆芯熔盐低热导率而形成的热管密集排布给热管冷凝段的温差发电传热设计带来了难题。针对该堆型设计需求,本文提出适于熔盐堆的热管-温差发电耦合系统结构并进行了传热分析。堆芯热管冷凝段采用塔式温差发电系统结构设计,整体热端座与堆芯热管冷凝端相配合,形成从下至上的第1层至第N层热段套;冷端座套置于热端座外,内设冷端热管通道;热端座的外侧壁与冷端座的内侧壁之间贴有温差发电片,发电片间隙采用保温棉减少漏热。采用Ansys Workbench开展了适于热管熔盐堆的4层塔式温差发电系统传热仿真模拟,分析表明:系统运行的高温热管最高温度为696℃时,整体塔座温度分布均匀,热量有效利用率大于96%,系统漏热量小于4%,发电片两侧温差大于490℃,利于提高热电转换效率,设计具有可行性,有利于推动温差发电在热管熔盐堆中的应用。

[Background]Molten salt reactors,one of the important types of fourth-generation advanced reactors,use high-boiling-point molten salt as a nuclear fuel carrier after melting,hence have the characteristics of high-temperature output and normal-pressure operation.A heat-pipe molten salt reactor based on thermoelectric power generation has the advantages of its components,that is,high output temperature,high thermoelectric conversion efficiency,simple structure,safety,and reliability.Therefore,the reactor of heat-pipe molten salt has significant advantages in the field of energy systems as it is an ideal energy source for outer space and deep-sea exploration missions.However,because of the low thermal conductivity of the molten salt in the core,the dense arrangement of heat pipes complicates the heat transfer design of the thermal power generator in the condensing section of the heat pipes.[Purpose]This study aims to design a heat-pipe–thermal power generation coupling system structure suitable for molten salt reactors,and analyze its heat transfer characteristics on the basis of design requirements of the reactor.[Methods]Firstly,the condensing section of the core heat pipe was designed using a tower thermoelectric power generation system.A thermoelectric generator was placed between the outer wall of the hot-side tower and the inner wall of the cold-side tower,and the gap between the generators was made of an insulating material to reduce heat leakage.Then,a heat transfer simulation of a four-layer tower thermoelectric power generation system suitable for a heat-pipe molten salt reactor was performed using the ANSYS Workbench.Finally,temperature distribution and variation under different power values at each layer of the thermoelectric generator and every thermoelectric generator,etc.,were analyzed.[Results]The analysis results reveal that,when the system is running with maximum heat-pipe temperature of 696℃,the temperature distribution in the overall tower is uniform,the effective heat utilization rate is>96%,the system leakage heat is<4%,and the temperature difference between the two sides of the generator is>490℃,which is conducive for improving the thermoelectric conversion efficiency.[Conclusions]The structural design of this study is feasible and conducive for promoting the application of thermoelectric power generation in a heat-pipe molten salt reactor.