Numerical Investigation of Flow and Heat Transfer Characteristics on Tubes with Triangular Internal Fins

To overcome the low heat-transfer efficiency on the seawater side of the intermediate fluid vaporizer (IFV), a triangular inner-finned heat-transfer enhancement tube suitable for low to medium-flow-velocity conditions was designed. The influence of triangular internal fins’ axial spacing, height, radial arrangement number, and inclination angle on the flow and heat transfer characteristics inside the tube was numerically investigated. The tube performance was evaluated and optimized by performance evaluation criteria (PEC). The results indicated that triangular internal fins induced vortex structures, which disrupted the boundary layer, thereby enhancing momentum and energy exchange between the hot fluid within the boundary layer and the cold fluid outside it. Heat transfer was improved with reduced fin distance, increased height, and increased the number of radial arrangements. The optimal comprehensive performance was achieved at an inclination angle of 75°. The Nusselt number (Nu) increased by 66.02%, the friction factor (f) increased by 162.23%, and PEC reached up to 1.203 when Re was 9545. The results provided a theoretical reference for the structural optimization of efficient heat-exchange tubes.