Targeted heat load enhancement in shell‐and‐tube heat exchangers using twisted tape design

Abstract This study presents a design‐oriented approach for selecting the twist ratio of twisted tape inserts to achieve targeted heat transfer enhancement in shell‐and‐tube heat exchangers. Generalized correlations are developed from numerical data obtained through CFD analysis to characterize the thermohydraulic behaviour of twisted tapes. The expressions operate for a Reynolds number range of 500 to 45,000 and TR values from 2 to 7. Two key design parameters are identified as critical to heat load enhancement: (1) the thermal effectiveness of the exchanger, and (2) whether the tube side governs the limiting heat transfer coefficient. Two case studies are presented; first, for an exchanger with low thermal effectiveness of ε = 0.3750, the maximum heat load increase of 36.72% is achieved using the shortest twist ratio (TR = 2), accompanied by a 69.90% rise in pressure drop and a final thermal effectiveness of ε = 0.5127. The second case study has a higher thermal effectiveness of ε = 0.7857, the same twist ratio yields a more modest heat load gain of 4.27% and a final ε = 0.843 is obtained. The proposed method enables the selection of TR values that meet specific thermal performance targets. For example, in case study 1, achieving a 35.54% increase in heat load requires a twist ratio of 3.1, resulting in a 65.15% increase in pressure drop.