Abstract: In order to meet the needs of green environmental protection for energy conservation and emission reduction, and make full use of the advantages of good heat resistance and stability of molten salt, an electric heating furnace with indirect heating of molten salt was developed. Based on the natural convection model and Boussinesq hypothesis, the flow and heat transfer characteristics of molten salt and heat transfer oil in the enclosed space of the indirect heating furnace were studied by numerical simulation method, and the effects of different surface thermal strengths on the flow and heat transfer characteristics of the indirect electric heating furnace were compared. The results show that the density difference and temperature difference caused by the expansion of molten salt in the furnace after heating form a natural convection heat transfer in a confined space, and the average flow velocity of molten salt is 0.00613m/s when the surface thermal strength is 100%. The average temperature is 409.3°C, and a symmetrical annular circulation flow is formed on the cross-section of the electric heating tube from the bottom of the high-temperature heating tube to the upper heat transfer oil pipe, which strengthens the natural convection and heat transfer effect in the furnace, and the overall flow field and temperature distribution in the furnace are stable and uniform, and the heat released by the electric heating tube increases the inlet and outlet temperature of the heat transfer oil by 13.1°C through the indirect heating of molten salt of the intermediate medium, which can meet the process requirements. When the thermal intensity exceeds 100%, the natural convection circulation of molten salt in the furnace is significantly enhanced, the turbulence degree increases, and there is an obvious velocity boundary between the molten salt above the electric heating tube and the surrounding area, which positively affects the flow and heat transfer characteristics in the furnace.

Key words: molten salt, Indirect heating, electric heating furnace, flow characteristics, heat transfer characteristic

摘要： 为满足绿色环保的节能减排需求，充分利用熔盐耐热稳定性好的优势，提出了一种熔盐间接加热的管壳式电加热炉。基于自然对流模型和Boussinesq假设，采用数值模拟方法对加热炉封闭空间内的熔盐及导热油的流动与传热特性进行了研究，并分析电加热管的不同表面热强度对电加热炉内流动及传热特性的影响。研究结果表明：炉内熔盐受热后膨胀产生的密度差和温度差，形成密闭空间内的自然对流换热，表面热强度为设计值时熔盐平均流速为0.00613m/s，平均温度为409.3℃，在电加热管横截面上形成从底部高温加热管区域至上部导热油管的对称环形循环流动，强化了炉内的自然对流和传热效果；炉内整体流场和温度分布呈现稳定和均匀性；电加热管释放的热量，经过中间介质熔盐的间接加热使导热油进出口温度增加13.1℃，可以满足工艺需求。电加热管热强度超过设计值时，炉内熔盐自然对流循环流动明显增强，湍动程度增加，电加热管上方熔盐与周围存在明显速度边界，正向影响炉内流动及传热特性。

关键词: 熔盐, 间接加热, 电加热炉, 流动特性, 传热特性