A comprehensive numerical study on the fluid flow, thermal and exergetic performance of longitudinally ribbed spirally coiled tube with various shapes

The primary objective of this investigation is to examine the impact of rib configuration on flow behavior and heat transfer characteristics in a spiral tube with longitudinal ribs, through numerical simulations. Different cross-sectional shapes, including semicircular, V-shaped, trapezoidal, and rectangular ribs, are analyzed to assess the fluid flow, heat transfer, and exergetic efficiency of the tube. The findings indicate that incorporating longitudinal ribs of different crosssectional forms substantially improves the fluid flow and thermal efficiency of the spirally coiled tube. An increase in rib depth leads to an accompanying rise in the Nusselt number, with improvements ranging from 18.4% to 27.9% for V-shaped and trapezoidal ribs, respectively. The spiral tube with rectangular shaped ribs exhibits the highest Nusselt number. Additionally, when the rib depth increases from 0.02 to 0.12 for the spiral tube with rectangular-shaped ribs, the THPP (Thermohydraulic performance parameter) experiences a significant increase of 38.1%. Also, the number of ribs (Nr) in the longitudinally ribbed spirally coiled tube has a crucial impact on its performance. Increasing the number of ribs results in higher heat transfer coefficients and Nusselt numbers for all tested rib shapes. However, the inclusion of more ribs leads to increased exergy destruction across all scenarios.