Heat transfer performance of a corrugated channel using winglet insert and hybrid nanofluid

Recent academic research has placed significant emphasis on enhancing heat transfer through the exploration of passive technologies. A notable area of interest within this field involves the utilization of corrugated walls, which have demonstrated commendable capability in improving heat transfer in heat exchangers. However, it is important to acknowledge that the presence of these corrugated walls can also give rise to stationary vortices, which can have an adverse impact on overall efficiency. To address this issue, the study proposes the integration of winglet vortex generators within channels, which disrupt the vortices and enhance heat transfer while preserving the advantages of corrugated walls. Additionally, the study investigates the use of nanofluids as coolant additives, However, it did not achieve the desired objective of improving heat transfer. Therefore, the study sought to enhance heat transfer in corrugated channels by implementing winglet inserts and a hybrid nanofluid. The study begins with a numerical analysis of water flow in a rectangular corrugated channel, examining different surface geometries such as trapezoidal, wavy, and triangular. Winglet vortex generators are then introduced into the trapezoidal-corrugated channel to evaluate their impact on thermal and hydraulic performance, comparing the results to smooth and trapezoidal-corrugated channels. The study further explores various parameters of the winglet vortex generators, including wing inclination angle, length, and location within the channel, using both water and nanofluids. Heat transfer rates and flow characteristics of different nanofluids, including MgO/water, CuO/water, and CuO-MgO/water hybrids, are analyzed within the channel equipped with longitudinal vortex generators. Experimental tests are conducted to synthesize the nanofluids at different concentrations and temperatures, evaluating their thermal conductivity and stability. The numerical investigation reveals that the trapezoidal-corrugated surface demonstrates higher performance in augmenting Nusselt numbers, skin friction coefficient, and Performance Evaluation Criteria (PEC) in comparison to alternative corrugated surfaces. Additionally, the integration of winglet vortex generators into the trapezoidal-corrugated channel yields a substantial increase of 190.9% in the Nusselt number and 130.2% in skin friction when contrasted with a smooth channel. Numerical analysis reveals noteworthy improvements in the Nusselt number for different nanofluids, namely MgO/water, CuO-MgO/water hybrid, CuO/water, and water, within the trapezoidal channel equipped with a winglet vortex generator. Specifically, enhancements of 246.3%, 225.94%, 211.06%, and 190.9% are observed, respectively. Furthermore, the study indicates that nanofluids exhibit higher skin friction coefficients, with average increments of 20%, 16%, and 11.4% for the CuO/water nanofluid, CuO-MgO/water hybrid nanofluid, and MgO/water nanofluid, respectively, when compared to water within the trapezoidal channel with winglets. Experimental findings demonstrate that the addition of 20% MgO nanoparticles to CuO/water nanofluids enhances thermal conductivity by 16.1% while maintaining stability. An empirical equation with high accuracy (R2=0.9942) is developed to establish correlations between temperature, volume concentration, and thermal conductivity. Experimental analyses reveal that nanofluids exhibit higher heat transfer and skin friction characteristics in the trapezoidal-corrugated channel with winglet vortex generators, owing to their improved thermal conductivity. The combination of trapezoidal corrugations, optimized winglet vortex generators, and CuO-MgO/water hybrid nanofluids significantly enhances heat transfer both numerically and experimentally, albeit at the expense of increased skin friction.

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