Abstract
<jats:p>Purpose: This paper investigates shell-side convective heat transfer in a vertically oriented helically coiled tube heat exchanger (HCTHEX) and develops a global correlation for predicting the shell-side Nusselt number. Design/methodology/approach: A steady-state conjugate CFD database was generated using liquid water on both sides of the exchanger. The database contains 2,400 averaged operating points spanning shell-side flow rate, coil-side thermal response, and dimensionless coil pitch. Coil-side Nusselt number and pressure drop were benchmarked against established correlations, and shell-side behavior was then modeled using conventional regressions and a GAM/ensemble surrogate. Findings: The shell-side Nusselt number increased with the hydraulic-diameter-based Reynolds number, but the scatter showed that Re alone cannot represent the shell-side response. The GAM/ensemble model captured the coupled effects of Re, coil-side Nusselt number, and pitch, achieving R2 approximately 0.83 and RMSE approximately 19.6. Originality/value: The study provides a dense conjugate CFD dataset and a data-driven global shell-side Nusselt-number correlation for a HCTHEX geometry family where shell-side convection is strongly affected by morpho-hydrodynamic coupling rather than by a single Re-based trend. Practical implications: The proposed surrogate supports prediction, comparison, and design-space screening within the investigated Reynolds-number, pitch, and geometric ranges.</jats:p>