Effect of Thickness on Thermo-Hydraulic Performance of a DPHE with Twisted Perforated Tapes: A Numerical Study

While twisted tape inserts are widely used for heat transfer enhancement, the specific impact of tape thickness remains under-explored. This study provides a systematic numerical investigation into the thermo-hydraulic performance of a double-pipe heat exchanger equipped with twisted perforated tape (TPT) inserts of varying thicknesses (1, 1.5, and 2 mm). Using a validated 3D SST k−ω model across Re = 1000–12,000, the research establishes a mechanistic distinction between flow regimes. The results indicate that the 2 mm TPT yields the highest enhancement, achieving a 78.6% increase in the average Nusselt number (Nuavg) and a 67.8% improvement in the overall heat transfer coefficient at Re = 12,000. Quantitative analysis of secondary flow intensity and turbulence kinetic energy confirms a transition from geometry-induced swirl at low Re to turbulence-driven shear at high Re. Despite a pressure drop penalty of up to 3.26 times the plain tube, the thermal performance factor remained above unity for all cases, peaking at 1.17 at Re ≈ 4000. These findings establish tape thickness as a first-order design variable for optimizing high-performance thermal systems.