翅片管式空气–熔盐换热器的数值模拟优化

Numerical Optimization of Finned Tube Heat Exchanger for Air-Molten Salt Heat Transfer

摘要: 本文采用FLUENT软件对高温空气–熔盐在翅片管式换热器中的换热进行数值模拟，研究高温空气–熔盐之间的换热与流动特性。在翅片管式换热器的管内走熔盐，管外翅片间走高温空气。模拟主要考察对于不同雷诺数及不同翅片间距下，翅片管式换热器中空气侧的换热和阻力特性。计算结果表明：随着空气侧流速的增加，空气侧表面换热系数有显著增加，而平均阻力系数逐渐减少并趋于平缓。增加空气侧流速可以强化空气侧换热，但是增加流速使得风机的能耗大大增加。在低雷诺数下，翅片表面的换热分布不均匀，换热主要集中在迎风侧，从而使管壁四周换热不均匀，导致管内熔盐形成涡流，从而产生X方向的速度。随着翅片间距的增加，空气侧表面换热系数呈现先增加后减小的变化趋势。

Abstract: This paper numerically simulated the heat transfer process of the high temperature air-molten salt in the finned tube heat exchanger by use of a software called FLUENT. The heat transfer and flow characteristics between the high temperature and molten salt were studied. In the finned tube heat exchanger, the molten salt is flowing inside the tube while the outside is surrounded by the high temperature air, which is flowing between the fins. In the simulating process, the heat transfer and resistance characteristics for the air side in the exchanger are investigated under the condition of different Reynolds numbers and fin spaces. The results show that the surface heat transfer coefficient of the air side has a significant increase with the increase of flow velocity in the air side, while the average drag coefficient gradually reduces and tends to be gentle. Increasing the flow velocity of air side can strengthen the heat transfer, while the increase of velocity leads to the significant energy lost for the fan. When the Reynolds number is small, the heat transfer distribution of fin surface is obviously nonuniform, the heat transfer is mainly focused on the windward side and the heat transfer around the pipe wall is uneven, which leads to the formation of vortex for the molten salt inside the tube. Meanwhile, the velocity of the X direction is also generated. With the increase of fin space, the surface heat transfer coefficient of the air side shows a changing trend that first increases and then decreases.