Research on correlation between SWHE performance and geometric parameters driven by working fluid physical properties

doi:10.3969/j.issn.2097-0706.2026.06.003

Abstract

Abstract:

Spiral-wound tube heat exchangers （SWHE） hold significant application potential in the steam-molten salt heat exchange process within deep peak shaving systems for coal-fired power units. Existing research has primarily focused on optimizing SWHE geometric structures， leaving a research gap regarding the regulatory effects of working fluid thermophysical properties on SWHE performance. A multi-objective optimization framework was established by integrating a SWHE design calculation model with a non-dominated sorting genetic algorithm. The framework targeted comprehensive performance evaluation criteria for both hot and cold sides， average heat transfer coefficient， shell outer diameter， and total entropy generation number. Optimization design research was conducted for five mixed molten salts： solar salt， Hitec， Hitec XL， quaternary nitrate， and ternary nitrate. The results indicated that working fluid thermophysical properties significantly influenced the correlation between SWHE geometric parameters and performance. For instance， when high-viscosity molten salts （such as Hitec XL） served as working fluids， the winding angle of the SWHE exhibited a strong positive correlation with the overall heat transfer coefficient. Furthermore， increasing the tube diameter could enhance the heat transfer coefficient. This behavior differs significantly from SWHEs employing other molten salts as working fluids. Meanwhile， the correlation between the spiral angle of SWHEs using high-thermal-conductivity molten salts （such as quaternary nitrate） as working fluids and the entropy generation number showed characteristics opposite to those observed with other molten salts as working fluids. Finally， through comprehensive decision-making based on heat transfer intensity per unit volume and entropy generation number， four recommended solutions were selected from the Pareto solution set obtained by multi-objective optimization. Solution 1 exhibited optimal compactness （heat transfer area： 984.96 m²， construction cost： 5.838 million yuan）， but had higher operating costs （1.1531 million yuan/year）. Despite its larger heat transfer area （3 904.88 m²） and higher construction cost （12.161 million yuan）， Solution 4 achieves a 51.5% cut in annual operating cost （559 300 yuan/year） compared with Solution 1 due to its low entropy generation number. The results indicate that the thermophysical properties of mixed molten salts correlate with the performance and geometric parameters of SWHE， which lays a theoretical foundation and offers practical solutions for molten salt formulation screening and SWHE engineering design.

Key words: peak shaving of coal-fired power unit, thermophysical properties of molten salt, spiral-wound tube heat exchanger, heat exchanger design, multi-objective optimization, correlation analysis

CLC Number:

TK172

WANG Zixuan, LU Yuanwei, YANG Han, WU Yuting. Research on correlation between SWHE performance and geometric parameters driven by working fluid physical properties[J]. Integrated Intelligent Energy, 2026, 48(6): 34-45.

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混合熔盐	熔点	分解温度
太阳盐	223.2	575.9
Hitec	142.0	500.0
Hitec XL	120.0	500.0
四元盐	86.5	629.9
三元盐	135.5	648.5

混合熔盐	密度拟合公式
太阳盐	$2\mathrm{ }136-0.710\mathrm{ }8\mathit{t}$
Hitec	$2\mathrm{ }083.5-0.748\mathit{t}$
Hitec XL	$2\mathrm{ }240-0.827\mathit{t}$
四元盐	$2\mathrm{ }081.51-0.618\mathrm{ }5\mathit{t}$
三元盐	$2\mathrm{ }068+0.210\mathrm{ }2\mathit{t}-1.331\times {10}^{-3}{\mathit{t}}^{2}$

混合熔盐	比热容拟合公式
太阳盐	$1\mathrm{ }838.96+2.8\mathit{t}-0.016\mathrm{ }68{\mathit{t}}^{2}+1.686\times {10}^{-5}{\mathit{t}}^{3}$
Hitec	$1\mathrm{ }507-0.1\mathit{t}$
Hitec XL	$1\mathrm{ }634-0.33\mathit{t}$
四元盐	$2\mathrm{ }513.4-5.15\mathit{t}+0.001\mathrm{ }03{\mathit{t}}^{2}-9.823\times {10}^{-6}{\mathit{t}}^{3}$
三元盐	$1\mathrm{ }342+1.15\mathit{t}-1.137\times {10}^{-3}{\mathit{t}}^{2}$

混合熔盐	热导率拟合公式
太阳盐	$2.915\mathrm{ }31-1.659\times {10}^{-2}\mathit{t}+3.818\times {10}^{-5}{\mathit{t}}^{2}-2.939\times {10}^{-8}{\mathit{t}}^{3}$
Hitec	$0.586-0.000\mathrm{ }64\mathit{t}$
Hitec XL	$0.519$
四元盐	$4.800\mathrm{ }35-3.515\times {10}^{-2}\mathit{t}+9.586\times {10}^{-5}{\mathit{t}}^{2}-8.429\times {10}^{-8}{\mathit{t}}^{3}$
三元盐	$0.261+8.941\times {10}^{-4}\mathit{t}+1.709\times {10}^{-8}{\mathit{t}}^{2}$

混合熔盐	黏度拟合公式
太阳盐	${10}^{-3}\times 0.281\mathrm{ }49{\mathrm{e}}^{\frac{2.135\mathrm{ }79}{\mathit{t}}}$
Hitec	$0.001\mathrm{ }7-0.124\mathrm{ }9{\mathrm{e}}^{\frac{-\mathit{t}}{57.05}}$
Hitec XL	${10}^{6.137\mathrm{ }4}{\mathit{t}}^{-3.364\mathrm{ }06}$
四元盐	${10}^{-3}\times 0.488\mathrm{ }845{\mathrm{e}}^{\frac{621.738}{\mathit{t}}}$
三元盐	${10}^{-3}\times 0.810\mathrm{ }5{\mathrm{e}}^{\frac{3\mathrm{ }311}{8.314\mathit{t}}}$