Gopinath Mandal

Flow and heat transfer of nanofluids at a stagnation point flow over a stretching/shrinking surface in a porous medium with thermal radiation

Abstract In this paper, the effects of thermal radiation and viscous dissipation on a stagnation point flow and heat transfer over a flat stretching/shrinking surface in nanofluids are analyzed. The effects of suction/injection are also considered. Using a similarity transformation, the governing equations are transformed into a system of nonlinear ordinary differential equations. The resulting system is then solved numerically by Runge–Kutta–Fehlberg method with shooting technique. It is observed that the local Nusselt number increases with increment in the suction/injection parameter for stretching sheet whereas reverse effect is observed for shrinking sheet. It is found that skin-friction coefficient increases for both stretching/shrinking sheet with increase in volume fraction of the nanoparticles.

Soret and Dufour effects on MHD convective-radiative heat and mass transfer of nanofluids over a vertical non-linear stretching/shrinking sheet

A numerical investigation is applied to study the influence of the Soret and Dufour effect on mixed convection heat and mass transfer of nanofluids in the boundary layer region over a non-linear stretching and shrinking sheets in the presence of thermal radiation. The governing differential equations are solved numerically using a fifth-order Runge-Kutta-Fehlberg integration scheme with a shooting technique. The influence of mixed convection parameter, Soret and Dufour number, magnetic field and thermal radiation parameters on velocity, temperature and concentration fields as well as on the skin-friction coefficient, local Nusselt number and local Sherwood number are illustrated graphically for three types of metallic or nonmetallic nanoparticles, namely copper (Cu), alumina (Al2O3) and titanium dioxide (TiO2) in the base fluid water in order to show some interesting phenomena. The obtained results show appreciable effects of Soret and Dufour numbers i.e. the effects of increase in Soret number (or decrease in Dufour number) decrease the skin-friction coefficient and Nusselt number for shrinking sheet, whereas the reverse effects are found for stretching sheet.

Effectiveness of convection-radiation interaction on stagnation-point flow of nanofluids past a stretching/shrinking sheet with viscous dissipation

In this paper, a numerical model is developed to study mixed convection heat transfer on a stagnation-point flow over a stretching/shrinking sheet in nanofluids in the presence of thermal radiation and viscous dissipation. Three types of nanofluids, namely copper-water, alumina-water, and titanium dioxide-water are considered. It is observed that the local buoyancy parameter, effective Prandtl number, and internal heat generation/absorption give some interesting and significant results on the skin-friction coefficient and local Nusselt number for all three types of nanofluids. It is found that the variation in the suction/injection parameter plays an important role in having dual solutions.