Natural heat convection of water-based alumina (Al2O3/water) nanofluids (with volume fraction 1% and 4%) in a horizontal cylinder is numerically investigated. The whole three-dimensional computational fluid dynamics (CFD) procedure is performed in a completely open-source way. Blender, enGrid, OpenFOAM and ParaView are employed for geometry creation, mesh generation, case simulation and post pr...

In the present investigation heat transfer character due to viscous dissipation and magnetic field applied to unsteady boundary layer fluid flow past a stretching sheet is investigated. The equations governing the unsteady boundary layer fluid flow are constructed and non-dimensionalized. The non-dimensional equations are discretized using implicit finite difference method of Crank-Nicolson typ...

In this study, in order to increase the heat transfer rate in concentric double-pipe heat exchangers by an active method, a rotating ball valve was mounted downstream of the outer pipe end and used as a pulse generator. In the experimental set-up, hot water (40-70 °C) was passed through the inner pipe with fixed mass flow rate (Reynolds number ≈ 10,200) while cold water was passed through the a...

We report experimental results for the heat transport, as expressed by the Nusselt number Nu, by turbulent Rayleigh-Bénard convection in a cylindrical sample of aspect ratio Γ ≡ D/L = 0.50 (D = 1.12 m is the diameter and L = 2.24 m the height). The measurements are for the Rayleigh-number range 10 <∼ Ra <∼ 10 15 and for a Prandtl number Pr ' 0.86. At these large Ra the results were exceptionall...

A theoretical study is presented in this paper to investigate the conjugate heat transfer across a vertical ®nite wall separating two forced and free convection ̄ows at different temperatures. It is assumed that the heat conduction in the wall is only in the transversal direction. We also assume that countercurrent boundary layers are formed on the both sides of the wall. The governing equation...

The present study considers steady laminar two-dimensional incompressible flow over both in-line and staggered flat tube bundles used in heat exchanger applications. The effects of various independent parameters, such as Reynolds number (Re), Prandtl number (Pr), length ratio (L=Da), and height ratio (H=Da), on the pressure drop and heat transfer were studied. A finite-volume-based FORTRAN code...

We report Nusselt number measurements from high Prandtl number turbulent thermal convection experiments. The experiments are conducted in four fluids with the Prandtl number Pr varying from 4 to 1350 and the Rayleigh number Ra from 2x10(7) to 3x10(10), all in a single convection cell of unity aspect ratio. We find that the measured Nusselt number decreased about 20% over the range of Pr spanned...

Graetz and Nusselt studied heat transfer between a developed laminar fluid flow and a tube at constant wall temperature. Here, we extend the Graetz–Nusselt problem to dense fluid flows with partial wall slip. Its limits correspond to the classical problems for no-slip and no-shear flow. The amount of heat transfer is expressed by the local Nusselt number Nux, which is defined as the ratio of co...

in this paper, natural convection heat transfer over a vertical plate in a darcy porous medium saturated with a nanofluid subject to heat generation/absorption was theoretically studied. the governing partial differential equations were transformed to a set of ordinary differential equations using similarity transformations and solved using finite difference method. the influence of parametric ...

entry region of a rectangular microchannel is investigated. The wall heat flux is peripherally constant and varies exponentially with respect to the axis of the microchannel. The flow is assumed to be hydrodynamically fully developed. The three-dimensional energy conservation equation is solved numerically for different aspect ratios. Surface interaction parameters consist of momentum accommoda...