Unsteady Natural Convection Flow of Multi-Phase Nanofluids Past a Vertical Plate with Constant Heat Flux

Heat transfer by natural convection is widely applied in science and engineering. Enhancing the fluid involved in such a process would be a remarkable achievement. Nanofluids have of late emerged as critical enhancers of such fluids. Such fluids are composed of nanoparticles of sizes 1-100 nanometers dispersed in a base fluid. As a result of such enhanced thermal conductivity properties, nanofluids can be considered as the next generation heat transfer agents. Many scholarly works have been undertaken on nanofluids boundary layer flows. However, in many practical applications, the boundary of the surface is subjected to a constant heat flux instead of being at a constant temperature. Unfortunately, little has been reported on the constant heat flux boundary condition despite the vast presence of constant heat flux in many industrial and engineering applications.

Researchers at University of Technology PETRONAS in Malaysia, Marneni Narahari, Rajashekhar Pendyala, and S. Suresh Kumar Raju proposed a study to analyze the transient two-dimensional natural convection boundary layer flow of multi-phase nanofluid past a vertical plate with constant heat flux. They aimed at analyzing the effects of Brownian motion and thermophoresis in the nanofluid model. They also hoped to consider the nature of the nanoparticle volume fraction on the boundary. Their research work is now published in the journal, Chemical Engineering Science.

The research team initiated their empirical procedure by employing an effective implicit finite difference technique of Crank-Nicolson method to solve the governing non-linear coupled partial differential equations. They then illustrated graphically and analyzed in detail the effects of time, Brownian motion parameter, thermophoresis parameter, buoyancy ratio parameter, Prandtl number and Lewis number on the dimensionless velocity, temperature and nanoparticle volume fraction. More so, they also presented graphical results for local as well as average skin-friction and Nusselt number. Eventually, they carried out a comparative study so as to validate their numerical results.

The authors observed that the velocity, temperature and nanoparticle volume fraction evolved with time and reached steady state as time progressed. The researchers also noted that the local Nusselt number slightly increased with increasing Brownian motion parameter and it decreased with increasing thermophoresis parameter, but the influence of buoyancy ratio parameter did not show any impact on the local Nusselt number.

Marneni Narahari and colleagues presented a comprehensive numerical study on the two-dimensional transient natural convective boundary layer flow of multi-phase nanofluid past a semi-infinite vertical plate with constant heat flux. In their work, an implicit finite difference technique of Crank-Nicolson has been employed to solve the governing non-linear coupled partial differential equations. Their work has presented graphical and detailed explanations on the effects of different physical parameters on velocity, temperature, nanoparticle volume fraction, local as well as average skin-friction and the Nusselt number. More so, the presented numerical solution has been validated by comparing the local Nusselt number results with the well-established correlations results for the limiting case and an excellent agreement was found between the results.