Thermal Performance Evaluation of a Helical-Finned Pipe-in-Pipe Heat Exchanger

Efficient heat exchangers are crucial for diverse industrial applications, including chemical processing, petroleum refining, and paper production. Driven by the need for enhanced energy efficiency and environmental sustainability, improving heat transfer performance is a critical objective. This study examines the heat transfer characteristics of a concentric tube heat exchanger, focusing on the synergistic effect of external helical fins and internal tube rotation. A one-meter counter-flow exchanger was constructed, featuring a 21mm fin spacing. Water was utilised as the coolant within the inner tube, while glycerol served as the heating medium in the outer shell. Maintaining a constant cold fluid flow, the hot fluid flow rate was varied. Convective heat transfer coefficients were measured for both static and rotating inner tubes across a range of rotational speeds. The findings revealed a significant enhancement in heat transfer due to the combined application of helical fins and tube rotation. The fins augmented the heat exchange surface area, while rotation promoted fluid mixing, thereby boosting convective heat transfer. Notably, the Nusselt number, a measure of convective heat transfer, exhibited an increase of up to 72% at 110 rpm compared to the stationary finned tube. The experimental results were compared with the established Dittus- Boelter correlation, confirming the efficacy of this approach for improving heat exchanger performance. Major Findings: The combination of helical fins and inner tube rotation significantly enhanced heat transfer, increasing the Nusselt number by up to 72% at 110 rpm. Experimental results consistently outperformed predictions from the Dittus-Boelter equation, confirming improved convective performance. This approach enables compact, highly efficient heat exchanger designs for industrial applications.