Thermohydraulic performance of a novel shell-and-spiral-tube heat exchanger with a perforated inner tube and hybrid nanofluids: A CFD analysis

This study numerically investigates a synergetic strategy to enhance the thermal efficiency of a shell and spiral tube heat exchanger using hybrid nanofluids and a novel perforated inner tube. First, a comparative analysis was conducted among pure water, CuO-MoS₂/water, and MgO-Al₂O₃/water hybrid nanofluids. The results identified a 0.5% volume concentration of MgO-Al₂O₃/water as the superior working fluid for heat transfer enhancement compared to the other tested fluids. Second, a hollow perforated tube was introduced on the shell side to induce jet cross-flow. The numerical results demonstrate that this geometric modification significantly promotes fluid mixing and disrupts the thermal boundary layer. Specifically, the thermal efficiency of the perforated configuration improved by 199% compared to the unmodified baseline, while the non-perforated hybrid nanofluid case showed a 118% increase. Despite a higher pressure drop penalty at increased Reynolds numbers, the trade-off analysis confirms that the perforated design remains highly effective for low-flow regimes. These findings suggest that the integration of MgO-Al₂O₃ hybrid nanofluids and perforated tube geometry offers a high-performance solution for compact thermal management systems.