Numerical investigation of flow characteristics and heat transfer efficiency in sawtooth corrugated pipes with Al2O3-CuO/Water hybrid nanofluid

Abstract

Improvements in heat transfer technologies are a key factor in making all industries that use condensers, solar collectors, and thermal machines more efficient and use less energy. With the development of corrugated pipes that improve convection in an affordable way, passive techniques to optimise heat conduction have entered the market. The objective of this study was to evaluate the performance of a hybrid nanofluid in improving heat transfer efficiency by using corrugated pipes. In particular, we investigated the behaviour of a hybrid nanofluid with a volume concentration of 0.5% Al2O3-CuO/water (80:20 by volume). To investigate the characteristics of the hybrid nanofluid, we used sawtooth-shaped corrugated pipes with different pitch height and pitch distance. The results show that increasing the Reynolds number improves the heat transfer due to higher flow velocities and disturbances from the corrugated surfaces. In terms of the Nusselt number, which is an indicator of convective heat transfer, corrugated pipes consistently perform better than smooth pipes. The average Nusselt number increases between 8% and 74% for the sawtooth-shape corrugated pipes which depends on the pitch height, pitch distance, and Re. However, the presence of corrugations leads to increased friction factors and pressure drops compared to smooth pipes, with larger corrugation amplitudes exacerbating these effects. Shorter pitch distances result in higher Nusselt numbers due to increased flow turbulence and mixing, while longer pitch distances lead to lower Nusselt numbers. These results contribute to the understanding of the effects of pitch height and pitch spacing on corrugated pipe performance. They also provide insights for the design optimisation of efficient heat transfer systems.

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