To enhance the heat transfer inside the helically coiled tubes, a kind of internally finned helically coiled tubes is proposed. Compared to the smooth helically coiled tubes, the heat transfer and flow resistance characteristics of internally finned helically coiled tubes are investigated numerically. Influence of fin number, pitch and coil diameter on the performance is analyzed. Empirical correlations to calculate the Nusselt number and friction factor of internally finned helically coiled tubes are summarized. The helically coiled tubes heat exchangers are divided equally into several cells and the theoretical analysis of energy flow in each cell is carried out. According to the established equations of heat transfer, the calculation method for single-stream helically coiled tubes heat exchangers and multi-stream helically coiled tubes heat exchangers is proposed. The geometric model and thermohydraulic model are built up, and the design software for internally finned helically coiled tubes heat exchangers is developed based on Python. Take two cases of helically coiled tubes heat exchangers as examples, smooth helically coiled tubes and internally finned helically coiled tubes (fin number is six) are applied to validate the accuracy of calculations results obtained by design software. The results show that the deviation of outlet temperature and pressure drop is less than 7 % and 11 %, respectively. When applying internally finned helically coiled tubes, the heat transfer coefficient of the tube side is increased by approximately 30 %. The corresponding pressure drop and heat load is higher. The outlet temperature proves that the heat transfer is more insufficient in the case of internally finned helically coiled tubes (fin number is six).

中文翻译：

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单流、多流内翅片螺旋管换热器数值研究及软件设计


为了增强螺旋管内部的传热，提出了一种内翅片螺旋管。与光滑螺旋管相比，内翅片螺旋管的传热和流阻特性进行了数值研究。分析了翅片数量、节距和线圈直径对性能的影响。总结了计算内翅片螺旋管的努塞尔数和摩擦系数的经验关系。将螺旋管换热器均分为若干单元，并对各个单元内的能量流进行理论分析。根据建立的传热方程，提出了单流螺旋管换热器和多流螺旋管换热器的计算方法。建立了几何模型和热工水力模型，并基于Python开发了内翅片螺旋管换热器设计软件。以两种螺旋管换热器为例，采用光滑螺旋管和内翅片螺旋管（翅片数为6）来验证设计软件计算结果的准确性。结果表明，出口温度和压降的偏差分别小于7%和11%。当采用内翅片螺旋盘管时，管侧传热系数可提高约30%。相应的压降和热负荷较高。出口温度证明，在内翅片螺旋管（翅片数为6）的情况下，传热更加不足。