Effect of thermal radiation on magnetohydrodynamics nanofluid flow and heat transfer by means of two phase model

Ferrohydrodynamic and magnetohydrodynamic effects on ferrofluid flow and convective heat transfer

Heat transfer of Cu-water nanofluid flow between parallel plates

Simulation of MHD CuO–water nanofluid flow and convective heat transfer considering Lorentz forces

Economic reasons (material and energy saving) leads to make efforts for making more efficient heat exchange. The heat transfer enhancement techniques are widely used in many applications in the heating process to make possible reduction in weight and size or enhance the performance of heat exchangers. These techniques are classified as active and passive techniques. The active technique required external power while the passive technique does not need any external power. The passive techniques are valuable compared with the active techniques because the swirl inserts manufacturing process is simple and can be easily employed in an existing heat exchanger. Insertion of swirl flow devices enhance the convective heat transfer by making swirl into the bulk flow and disrupting the boundary layer at the tube surface due to repeated changes in the surface geometry. An effort has been made in this paper to carry out an extensive literature review of various turbulators (coiled tubes, extended surfaces (fin, louvered strip, winglet), rough surfaces (Corrugated tube, Rib) and swirl flow devices such as twisted tape, conical ring, snail entry turbulator, vortex rings, coiled wire) for enhancing heat transfer in heat exchangers. It can be concluded that wire coil gives better overall performance if the pressure drop penalty is considered. The use of coiled square wire turbulators leads to a considerable increase in heat transfer and friction loss over those of a smooth wall tube.

Review of heat transfer enhancement methods: Focus on passive methods using swirl flow devices

Effects of Heat Transfer in Flow of Nanofluids Over a Permeable Stretching Wall in a Porous Medium

This work presents a thermal and flow analysis of a fin shaped microchannel heat sink (MCHS) cooled by different nanofluids (Cu and Al2O3 in water) based on “saturated porous medium” and least square method then results are compared with numerical procedure. The Forchheimer–Brinkman-extended Darcy equation is used to describe the fluid flow and the two-equation model with thermal dispersion is utilized for heat transfer. The effect of nanoparticle size and volume fraction, volume flow rate, inertial force parameter and channel width investigated on total thermal resistance, friction factor and Nusselt number. The effective thermal conductivity and viscosity of nanofluid are calculated by KKL correlation. Central composite design (CCD) is applied to obtain the desirability of the optimum value of the nanofluid flow characteristics. Results show that Cu–water nanofluid is more lucrative thermally versus Al2O3–water nanofluid. It is found that total thermal resistance, friction factor and Nusselt number are not sensitive to inertial effect while they change significantly due to other parameters such as nanoparticle size and volume fraction, volume flow rate and channel width. We obtained that Nusselt number enhancement has direct relationship with inertial force parameter and volume flow rate.

Numerical optimization of microchannel heat sink (MCHS) performance cooled by KKL based nanofluids in saturated porous medium

The lattice Boltzmann method (LBM) is used to examine free convection of nanofluids. The space between the cold outer square and heated inner circular cylinders is filled with water including various kinds of nanoparticles: TiO2, Ag, Cu, and Al2O3. The Brinkman and Maxwell-Garnetts models are used to simulate the viscosity and the effective thermal conductivity of nanofluids, respectively. Results from the performed numerical analysis show good agreement with those obtained from other numerical methods. A variety of the Rayleigh number, the nanoparticle volume fraction, and the aspect ratio are examined. According to the results, choosing copper as the nanoparticle leads to obtaining the highest enhancement for this problem. The results also indicate that the maximum value of enhancement occurs at λ = 2.5 when Ra = 106 while at λ = 1.5 for other Rayleigh numbers.

Free convection of nanofluid filled enclosure using lattice Boltzmann method (LBM)

The aim of the present paper is to study the flow of nanofluid and heat transfer characteristics between two horizontal plates in a rotating system. The lower plate is a stretching sheet and the upper one is a solid porous plate. Copper (Cu) as nanoparticle and water as its base fluid have been considered. The governing partial differential equations with the corresponding boundary conditions are reduced to a set of ordinary differential equations with the appropriate boundary conditions using similarity transformation, which is then solved analytically using the homotopy analysis method (HAM). Comparison between HAM and numerical solutions results showed an excellent agreement. The results for the flow and heat transfer characteristics are obtained for various values of the nanoparticle volume fraction, suction/injection parameter, rotation parameter, and Reynolds number. It is shown that the inclusion of a nanoparticle into the base fluid of this problem is capable of causing change in the flow pattern. It is found that for both suction and injection, the heat transfer rate at the surface increases with increasing the nanoparticle volume fraction, Reynolds number, and injection/suction parameter and it decreases with power of rotation parameter.

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Flow and Heat Transfer of Cu-Water Nanofluid between a Stretching Sheet and a Porous Surface in a Rotating System

In this study, two phase simulation of nanofluid flow and heat transfer between parallel plates is investigated. The important effects of Brownian motion and thermophoresis have been included in the model of nanofluid. The governing equations are solved via homotopy perturbation method. According to comparison with previous works, this method has good accuracy to solve this problem. The semi analytical investigation is carried out for different governing parameters namely; the squeeze number, Hartmann number, Schmidt number and Eckert number. The results indicate that absolute skin friction coefficient decreases with increase of Hartmann number and squeeze number. Also it can be found that that Nusselt number is an increasing function of Hartmann number, Eckert number and Schmidt number but it is a decreasing function of squeeze number.

G. Domairry

Papers

Effects of Heat Transfer in Flow of Nanofluids Over a Permeable Stretching Wall in a Porous Medium

Numerical optimization of microchannel heat sink (MCHS) performance cooled by KKL based nanofluids in saturated porous medium

Free convection of nanofluid filled enclosure using lattice Boltzmann method (LBM)

Flow and Heat Transfer of Cu-Water Nanofluid between a Stretching Sheet and a Porous Surface in a Rotating System

Numerical simulation of two phase unsteady nanofluid flow and heat transfer between parallel plates in presence of time dependent magnetic field