TY  - EJOU
AU  - Al-Zuhairi, Ali 
AU  - Kadhim, Zena K. 
AU  - Al-Kayiem, Hussain H. 
AU  - Merdan, Shatha 

TI  - A Comparative CFD Simulation and Hydrothermal Analysis of Double-Pipe Heat Exchangers Enhanced by Fins and Inserts as Passive Methods
T2  - Energy Engineering

PY  - 
VL  - 
IS  - 
SN  - 1546-0118

AB  - The performance of heat exchangers is vital for reducing industrial energy consumption and operational costs, driving significant interest in passive methods to enhance heat transfer. This study conducts a systematic numerical analysis and comparison of two prevalent passive techniques, low-integral circular fins and plain twisted-tape inserts, utilized in a counterflow double-pipe heat exchanger (DPHE). Three models were simulated in ANSYS FLUENT 2022 R1: a smooth DPHE (baseline), a finned DPHE with integrated circular fins on the outside of the inner pipe, and a DPHE with twisted-tape inserts in the inner pipe. Simulations were performed with hot-side Reynolds numbers (Re) varying from 5500 to 30,000 and inlet temperatures between 50°C and 70°C, while the cool side operated at Re from 2000 to 10,000. Critical performance metrics, including temperature changes, heat transfer rate, pressure drop, entropy generation, and the performance evaluation criterion (PEC), were analyzed to assess the balance between thermal improvements and hydraulic penalties. Finned pipes improve the cold-side temperature differential by 17%–19% at low cold-side Re and increase entropy generation by 20%–70%. Their PEC values range from 1.02 to 1.17, suggesting minor enhancements that diminish under fully turbulent conditions. Conversely, twisted tape inserts demonstrate higher performance at elevated Re and higher hot-side temperatures, increasing the cold-side temperature differential by 17%–26%, increasing entropy generation by 20%–82%, and increasing PEC values of 1.12–1.55, indicating a 12%–55% improvement over the baseline. However, this gain is accompanied by a significant pressure drop penalty, reaching up to four times that of the baseline case. Overall, low-integral fins are better suited to low- to moderate-flow regimes. Twisted tapes are more effective under turbulent conditions due to swirl-induced mixing. These findings support the practical selection of passive enhancement techniques in DPHE designs.
KW  - Double pipe heat exchanger; energy systems; entropy generation; performance evaluation; low integral finned pipe; twisted tape

DO  - 10.32604/ee.2026.086093