Thermal performance analysis and parameter optimization of spiral-wound heat exchangers by using local thermal-resistance ratio

Spiral-wound heat exchangers (SWHEs) are widely utilized in natural gas liquefaction, air separation, and other industrial applications due to their compact structure and high heat transfer efficiency. However, their intricate design poses significant challenges for structural design and optimization. This paper introduces the axial local thermal resistance ratio to characterize the shell-side thermal resistance distribution. It then investigates the effects of the spiral-wound tube outer diameter, radial interlayer spacing of the tube bundle, winding angle, and axial spacing between tubes in the same layer on this distribution. Based on these findings, a thermal resistance control optimization method for SWHEs is proposed. The results indicate that the proposed axial thermal resistance ratio exhibits high sensitivity to thermal resistance variations, rendering it suitable for analyzing and evaluating shell-side heat transfer. Specifically, the ratio decreases with an increasing outer diameter, increases with greater radial interlayer spacing, and also increases with larger axial spacing between tubes within the same layer. Furthermore, the ratio initially decreases and then increases with the winding angle. The proposed thermal resistance control optimization method demonstrates superior performance for SWHE optimization. Compared with a conventionally optimized externally grooved SWHE, the SWHE optimized using the proposed method achieves an average reduction of 10.7% in the axial local thermal resistance ratio and 13.0% in pressure drop.