Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 7 2021 09 23 Numerical investigation of the effect of thermophysical properties of nanofluid on fluid flow and heat transfer in a tube in presence of magnetic field Numerical investigation of the effect of thermophysical properties of nanofluid on fluid flow and heat transfer in a tube in presence of magnetic field 4329 4344 4261 10.22060/mej.2021.18936.6924 FA Yahya Malmir Chegini Faculty of Mechanical Engineering, University of Guilan, Iran Nima Amani Fard Journal Article 2020 09 02 In this paper, flow characteristics and heat transfer in a smooth horizontal pipe subjected to forced heat convection with constant wall heat flux in the presence of magnetohydrodynamic have been computationally analyzed. The effects of temperature-dependent density, specific heat capacity, thermal conductivity, and viscosity on heat transfer and frictional flow characteristics of transformer oil and local and average heat transfer coefficient have been numerically investigated. Firstly, to validate, the present numerical result has been compared with the analytical and experimental results through a smooth pipe, which shows a good agreement. A significant deviation between constant and variable properties has been achieved. Changes in fluid velocity profiles have led to changes in fluid characteristics including coefficient of friction and heat transfer coefficient. By considering the changes in the parameters, it was observed that the viscosity of the base fluid and the nanofluid have the maximum effect with approximately 30 and 25% increase in heat transfer coefficient and apparent friction coefficient relative to the fixed properties, respectively. Despite the dependence of the thermal properties of the nanofluid on temperature-dependent viscosity, the change in thermal conductivity leads to 35% increase in the heat transfer coefficient in the presence of a magnetic field. In this paper, flow characteristics and heat transfer in a smooth horizontal pipe subjected to forced heat convection with constant wall heat flux in the presence of magnetohydrodynamic have been computationally analyzed. The effects of temperature-dependent density, specific heat capacity, thermal conductivity, and viscosity on heat transfer and frictional flow characteristics of transformer oil and local and average heat transfer coefficient have been numerically investigated. Firstly, to validate, the present numerical result has been compared with the analytical and experimental results through a smooth pipe, which shows a good agreement. A significant deviation between constant and variable properties has been achieved. Changes in fluid velocity profiles have led to changes in fluid characteristics including coefficient of friction and heat transfer coefficient. By considering the changes in the parameters, it was observed that the viscosity of the base fluid and the nanofluid have the maximum effect with approximately 30 and 25% increase in heat transfer coefficient and apparent friction coefficient relative to the fixed properties, respectively. Despite the dependence of the thermal properties of the nanofluid on temperature-dependent viscosity, the change in thermal conductivity leads to 35% increase in the heat transfer coefficient in the presence of a magnetic field. https://mej.aut.ac.ir/article_4261_13384ffc9d8bdb21c53c6f72d46f7866.pdf