Thermal driven flows inside a square enclosure saturated with nanofluids: Convection heat functions and transfer rate revisions from a homogenous model

Abstract

In former theoretical researches of nanofluid flows, numerical investigations could not agree with experimental observations, particularly regarding whether the mixing nanoparticles will enhance or deteriorate the heat transfer. In the present work, thermal driven buoyancy flows of nanofluids in a square enclosure were modeled by the use of homogeneous assumptions and the effective kinematic viscosity and thermal conductivity formulas. Thoroughly developed heat transfer coefficient is subsequently proposed, aiming to critically evaluate the performance of nanofluid heat transport. Numerical results are presented over a wide range of thermal Rayleigh number (10³ ≤ Ra ≤ 10⁶) and nanoparticles volume fraction (0.001 ≤ φ ≤ 0.04). Present modeling results accurately predict both the enhancement and deterioration of the natural convection heat transfer, fully validated by former experimental observations. Overall, mathematical models and Nusselt number definitions proposed in the present work effectively enhance the reliability of numerical modeling researches on the nanofluid heat transfer. Present clarification research on the Nusselt unifications could benefit future development of thermal carrier fluid enhanced by nano-particles.

Acknowledgements

Both Prof. Fu-Yun Zhao and Prof. Han-Qing Wang would also like to acknowledge the support from the Collaborative Innovation Center for Building Energy Conservation and Environment Control, Hunan Province, China.

Additional information

Funding

This research was financially supported by the Natural Science Foundation of China (NSFC Grant No. 51778504, Grant No. U1867221), Joint Zhuzhou – Hunan Provincial Natural Science Foundation (Grant No. 2018JJ4064), National Defense Research Funds for the Central Universities (Grant No. 2042018gf0031, Wuhan University), and National Key Research and Development Program of the Ministry of Science and Technology of China (Grant No. 2018YFC0705201, Grant No. 2018YFB0904200).