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<p>The present study examines the thermal performance and exergy characteristics of ZnO/oil nanofluid flow through four different inner twisted tube designs, labeled RT1 to RT4, within a dual-tube heat exchanger (DTHE). Numerical simulations are performed over a Reynolds number (Re) range of 400 to 2000 for the hot-side oil-based nanofluid and at Re = 1800 for the cold-side water flow. The results reveal that increasing both the inlet flow rate and the twist angle of the inner tube enhances the convective heat transfer coefficient (HTC) and pressure drop (Δp). Among the studied configurations, the RT4 design, with a 90-degree twist, yields the highest HTC and Δp at Re = 2000. The application of oil-based nanofluid further enhances thermal performance, with improvements observed in both HTC and Δp values across all designs. However, the performance evaluation criterion (PEC) shows that the benefits of using nanofluids in twisted tubes only surpass the associated drawbacks under certain conditions. For instance, a 2% nanofluid concentration in RT1 and RT2 is the only case where PEC exceeds 1. Exergy analysis reveals that exergy destruction increases with higher values of Re, larger twist angles, and greater nanofluid volume fractions, primarily due to enhanced irreversibilities within the system.</p>

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Thermal performance and exergy analysis of a dual-tube heat exchanger with an inner twisted square tube

  • 期刊论文

  • 发表日期：

    2025年11月7日

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  • Shuang Liu,
  • Chaobin Fu,
  • Jie Ma,
  • Zijie Liu,
  • Guosheng An,
  • Yunhong Chen,
  • Yabo Zeng,
  • Guoyin Yang

摘要

The present study examines the thermal performance and exergy characteristics of ZnO/oil nanofluid flow through four different inner twisted tube designs, labeled RT1 to RT4, within a dual-tube heat exchanger (DTHE). Numerical simulations are performed over a Reynolds number (Re) range of 400 to 2000 for the hot-side oil-based nanofluid and at Re = 1800 for the cold-side water flow. The results reveal that increasing both the inlet flow rate and the twist angle of the inner tube enhances the convective heat transfer coefficient (HTC) and pressure drop (Δp). Among the studied configurations, the RT4 design, with a 90-degree twist, yields the highest HTC and Δp at Re = 2000. The application of oil-based nanofluid further enhances thermal performance, with improvements observed in both HTC and Δp values across all designs. However, the performance evaluation criterion (PEC) shows that the benefits of using nanofluids in twisted tubes only surpass the associated drawbacks under certain conditions. For instance, a 2% nanofluid concentration in RT1 and RT2 is the only case where PEC exceeds 1. Exergy analysis reveals that exergy destruction increases with higher values of Re, larger twist angles, and greater nanofluid volume fractions, primarily due to enhanced irreversibilities within the system.