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<p>This work presents a numerical heat transfer study for carbon nanotube–water nanofluid flowing through a horizontal tube subjected to constant heat flux by using non-Newtonian viscosity models in stress–strain relationship. In general, carbon nanotube–water nanofluid changes its behavior from Newtonian to non-Newtonian if nanoparticle volume fraction exceeds 0.055%, thus showing a Newtonian and non-Newtonian mixture behavior subjected to specific concentration of nanoparticles. So, this work presents a comparative numerical study for heat transfer coefficients obtained by using Newtonian and non-Newtonian viscosity models for carbon nanotube–water nanofluid with volume fraction over 0.055%. A modified Maron–Pierce model has been chosen as the Newtonian viscosity model, and power-law and Carreau–Yasuda models have been adopted when carbon nanotube–water nanofluid is considered as non-Newtonian shear thinning fluid. Different set of comparisons on the basis of axial variation of heat transfer coefficient at the tube wall have been performed between Newtonian and non-Newtonian behavior of carbon nanotube–water nanofluid in order to propose a suitable numerical approach for the analysis of heat transfer of carbon nanotube–water nanofluid when it shows mixed Newtonian/non-Newtonian characteristics. The results have been validated with earlier experimental and analytical works wherever possible. It has been found that the calculated heat transfer coefficient is higher when shear thinning behavior of nanofluid has been considered subjected to a high shear rate (near inlet). On the contrary, Newtonian heterogeneous model predicts larger heat transfer coefficient than that of others in the low shear rate region (in the fully developed region) due to nanoparticle depletion by Brownian diffusion and thermophoresis. The Carreau–Yasuda model predicts slightly lower enhancement in heat transfer coefficient as compared to the power-law model. A suitable numerical approach has been suggested for the analysis of heat transfer coefficient for carbon nanotube–water nanofluid.</p>

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A study on heat transfer characteristics of carbon nanotube–water nanofluid considering its combined Newtonian and non-Newtonian behavior: a suggestion on appropriate numerical approach

  • 期刊论文

  • 发表日期：

    2025年9月2日

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  • Saptarshi Mandal,
  • Amol Gulabrao Kamble,
  • Swagata Paul

摘要

This work presents a numerical heat transfer study for carbon nanotube–water nanofluid flowing through a horizontal tube subjected to constant heat flux by using non-Newtonian viscosity models in stress–strain relationship. In general, carbon nanotube–water nanofluid changes its behavior from Newtonian to non-Newtonian if nanoparticle volume fraction exceeds 0.055%, thus showing a Newtonian and non-Newtonian mixture behavior subjected to specific concentration of nanoparticles. So, this work presents a comparative numerical study for heat transfer coefficients obtained by using Newtonian and non-Newtonian viscosity models for carbon nanotube–water nanofluid with volume fraction over 0.055%. A modified Maron–Pierce model has been chosen as the Newtonian viscosity model, and power-law and Carreau–Yasuda models have been adopted when carbon nanotube–water nanofluid is considered as non-Newtonian shear thinning fluid. Different set of comparisons on the basis of axial variation of heat transfer coefficient at the tube wall have been performed between Newtonian and non-Newtonian behavior of carbon nanotube–water nanofluid in order to propose a suitable numerical approach for the analysis of heat transfer of carbon nanotube–water nanofluid when it shows mixed Newtonian/non-Newtonian characteristics. The results have been validated with earlier experimental and analytical works wherever possible. It has been found that the calculated heat transfer coefficient is higher when shear thinning behavior of nanofluid has been considered subjected to a high shear rate (near inlet). On the contrary, Newtonian heterogeneous model predicts larger heat transfer coefficient than that of others in the low shear rate region (in the fully developed region) due to nanoparticle depletion by Brownian diffusion and thermophoresis. The Carreau–Yasuda model predicts slightly lower enhancement in heat transfer coefficient as compared to the power-law model. A suitable numerical approach has been suggested for the analysis of heat transfer coefficient for carbon nanotube–water nanofluid.