Heat Transfer and Pressure Drop Characteristics of Alternating Clockwise-Counter Clockwise Curled Band Inserts in the Transitional Pipe Flow

Abstract

This study examines the research was analytically to look into the exchange of hotness along with pressure reduction feature within a flat round duct through alternate dextral along with anti-clockwise curled band (DACCB) inserts. The DACCB inserts were manufactured from copper ribbons (19 mm width, 1.5 mm thickness) with a curl ratio of 5 and joining gradients of 0°, 15° along with 45°, over a test length of 5.96 m. The DACCB insert was set within a plane round copper duct through an internal bore about 20 mm. Tests were conducted using water as a working medium over a heat flux of 1.35−4 kW/m² along with Reynolds number range of 305–11,410, covering the streamline, transitory and tumultuous run systems. The results demonstrate that alternating curl orientations promote earlier run of the transitory system and intensify mixing compared to the plain tube and convectional curled band designs. The DACCB with a 45º joining angle achieved a maximum Nusselt number improvement
of 46% at Re ≈ 1000 with a corresponding friction penalty of about 22%. The overall thermo-hydraulic performance factor (PEC) exceeded unity for all configurations, indicating net efficiency gain. Empirical correlations were developed to predict transition limits, Nusselt number, and friction factor, with deviations within ±10%. The findings suggest that DACCB inserts are a cost-effective passive method for improving compact heat exchanger performance while supporting energy conservation and carbon reduction goals. A rise in thermal flux importantly increased the transfer of heat in the streamline run system and retarded conversion. The transfer of heat and pressure loss connections grew to forecast the exploratory facts in the streamline, transitory and tumultuous systems like a role Reynolds number, altered Grashof number along with combination gradient.