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This theoretical study investigated the effect of thermophysical properties on Nusselt number when the magnetic field and thermal radiation are exposed to the ferrofluid flow at the lower stagnation point of a hot sphere surface. The thermophysical properties are important mechanisms considered in the heat transfer process. Besides, the ferroparticles volume fraction is one of the variables that can enhance the thermophysical properties that are exclusively studied on thermal conductivity and thermal diffusivity of ferrofluid. Therefore, the correlation between the ferroparticles volume fraction and thermophysical properties is measured by the Pearson product-moment correlation coefficient method. The strength of association and the direction of the relationship between these pertinent variables are exhibited in ferrofluid flow composed of magnetite (Fe3O4) and water (H2O). Regression analysis is implemented to predict the effect of the ferroparticles volume fraction on the Nusselt number. The results show a positive correlation between ferroparticles volume fraction and thermal conductivity as well as between ferroparticles volume fraction and thermal diffusivity. Furthermore, a simple linear regression model proposed to predict the Nusselt number when increasing the ferroparticles volume fraction resulted in statistically significant and given minuscule residuals value. [ABSTRACT FROM AUTHOR]

The influence of free convection flow on unsteady Casson fluid over a vertical channel is studied in this paper. The governing equation consists of partial differential momentum and energy equations have been transformed into non-dimensional equations by using the appropriate nondimensional variables. The expression of exact solutions for nondimensional velocity and temperature profiles are obtained by using the Laplace transform method. The obtained exact solutions are found satisfied all the initial and boundary conditions. The behaviour of velocity and temperature profiles influenced by Casson fluid parameter, Grashof number, Prandtl number and time are plotted graphically and presented in tables. It can be observed that, the velocity profile and boundary layer thickness decrease when the values of Casson fluid parameter and Prandtl number increase. This is due to the increase of viscous force and retard the movement of the velocity. The present result is validated when the obtained exact solution of velocity is compared with published result and found in a good agreement.

The boundary layer heat and mass transfer flow of Casson nanofluid over a stretching sheet with constant wall temperature (CWT) under the magnetic field and thermal radiation effects is investigated numerically. Using similarity transformations, the governing equations are reduced to a set of nonlinear ordinary differential equations (ODEs). These equations are solved numerically by Shooting method. The effects of Casson parameter, magnetic parameter, porosity parameter, radiation parameter, Prandtl number, Brownian parameter and thermophoresis parameter on velocity, temperature and concentration fields are shown graphically and discussed. The results show that increase in Casson parameter causes the wall temperature increase well in the nanofluid.

In this article the idea of time fractional derivatives in Caputo sense is used to study memory effects on the behavior of nanofluids because some physical processes complex visco-elasticity, behavior of mechatronic and rheology are impossible to described by classical models. In present attempt heat and mass transfer of nanofluids (sodium alginate (SA) carrier fluid with graphene nanoparticles) are tackled using fractional derivative approach. Exact solutions are determined for temperature, concentration and velocity field, and Nusselt number via Laplace transform technique. The obtained solutions are then expressed in terms of wright function or its fractional derivatives. Numerical solutions for velocity, temperature, concentration and Nusselt number are obtained using finite difference scheme. It is found that these solutions are significantly controlled by the variations of parameters including thermal Grashof number, fractional parameter and nanoparticles volume fraction. It is observed that rate of heat transfer increases with increasing nanoparticles volume fraction and Caputo time fractional parameters. [ABSTRACT FROM AUTHOR]

Soret effects on unsteady mixed-convection heat-and-mass-transfer flow over an oscillating vertical plate embedded in a porous medium with Newtonian heating in the presence of magnetic field are studied. The governing equations, along with imposed initial and boundary conditions, are first converted into the dimensionless form and then solved using the Laplace transform technique. The numerical results for fluid velocity, temperature and concentration are graphically shown, whereas the skin friction, Nusselt number and Sherwood number are presented in tabular forms. It is observed that the fluid velocity and concentration increase with increasing values of Soret number. The conjugate parameter of Newtonian heating increases the temperature as well as the concentration and velocity distributions. It is also found that the rates of the heat-andmass transfer increase as the conjugate parameter increases. [ABSTRACT FROM AUTHOR]