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Abstract

An experimental investigation was conducted to evaluate the hydrothermal and energy performance of a novel heat exchanger incorporating a wavy–twisted square conduit (WTSC) as the inner passage. Water was used as the working fluid and the shell-side flow rate was maintained at 1.7 L/min for all test cases. The effects of the conduit-side Reynolds number (Re = 5200, 7500, 10200, 12600, and 15400) and twist ratio (TR = 17.5 and 35) on the logarithmic mean temperature difference (LMTD), overall heat transfer rate, thermal effectiveness, pumping power, and energy efficiency index (η₁) were investigated. The thermal and hydraulic performances of the WTSC heat exchanger were also compared with those of heat exchangers incorporating twisted, wavy, and plain internal passages. Owing to the asymmetric swirling flow induced within the WTSC, enhanced fluid mixing occurs, which plays a significant role in improving the overall heat transfer rate. The results reveal that the WTSC heat exchanger increases the overall heat transfer rate by up to 39.9% compared with the plain configuration, while the twisted and wavy heat exchangers achieve improvements of 19.1% and 12.9%, respectively. Nevertheless, the asymmetric swirling flow leads to a pumping power penalty of up to 59.2% relative to the plain heat exchanger, whereas the corresponding penalties for twisted and wavy configurations are 20.8% and 44.9%, respectively. Furthermore, the experimental results indicate that the maximum energy efficiency index reaches 32.5% for the WTSC heat exchanger with a twist ratio of TR = 17.5 at Re=10200. Overall, the findings demonstrate that the proposed WTSC heat exchanger can provide a substantial enhancement in energy efficiency without requiring additional inserts or turbulators, highlighting its strong potential for energy recovery applications across a wide range of industrial systems.