INNOVATIVE HORIZONS IN SQUARE DUCTS HEAT TRANSFER ENHANCEMENT: PASSIVE,

Abstract

Heat transfer enhancement in square ducts forms the core of modern thermal engineering with a significant impact on the efficiency of heat exchangers, heating, ventilation, and air conditioning, and renewable energy equipment. The review encompasses both active and passive techniques of augmentation, their mechanism, applications, and comparative effectiveness. Active techniques—such as acoustic, electric, and magnetic actuation—improve heat transfer by developing flow instabilities and vortices but at the cost of employing intricate systems and extra energy. Conversely, passive configurations like ribs, baffles, twisted tapes, and winglets are simpler, energy-efficient, and increase turbulence responsible for degrading boundary layers, increasing the Nusselt number. The study is concerned with the effect of the geometrical parameters on the thermal and hydraulic performance, with respect to the trade-off between enhanced heat transfer and pressure loss. Optimal rib height ratios (e/H = 0.2–0.3) and pitch ratios (0.75–1.0) were determined to yield optimal performance, generating high heat transfer at reasonable pressure losses. The review also explores hybrid solutions that combine passive techniques with nanofluids to achieve synergistic improvements. Finally, the importance of vortex generation and combining advanced materials with smart optimization strategies are put forward as viable routes to efficient thermal management systems.