Showing papers on "Nusselt number published in 2017"
TL;DR: In this paper, a system of partial differential equations for micropolar and nanofluid has been analyzed by a combination of the similarity transformation and accurate finite-difference method.
427 citations
TL;DR: In this article, the synthesis of hybrid nanoparticles, preparation of hybrid nanofluids, thermal properties, heat transfer, friction factor and the available Nusselt number and friction factor correlations are discussed.
Abstract: In the past decade, research on nanofluids has been increased rapidly and reports reveal that nanofluids are beneficial heat transfer fluids for engineering applications. The heat transfer enhancement of nanofluids is primarily dependent on thermal conductivity of nanoparticles, particle volume concentrations and mass flow rates. Under constant particle volume concentrations and flow rates, the heat transfer enhancement only depends on the thermal conductivity of the nanoparticles. The thermal conductivity of nanoparticles may be altered or changed by preparing hybrid (composite) nanoparticles. Hybrid nanoparticles are defined as nanoparticles composed by two or more different materials of nanometer size. The fluids prepared with hybrid nanoparticles are known as hybrid nanofluids. The motivation for the preparation of hybrid nanofluids is to obtain further heat transfer enhancement with augmented thermal conductivity of these nanofluids. This review covers the synthesis of hybrid nanoparticles, preparation of hybrid nanofluids, thermal properties, heat transfer, friction factor and the available Nusselt number and friction factor correlations. The review also demonstrates that hybrid nanofluids are more effective heat transfer fluids than single nanoparticles based nanofluids or conventional fluids. Notwithstanding, full understanding of the mechanisms associated with heat transfer enhancement of hybrid nanofluids is still lacking and, consequently it is required a considerable research effort in this area.
365 citations
TL;DR: In this article, a thermal system numerical solutions of the flow velocity field, temperature field, mass transfer and heat conduction had been produced out as functions of the viscoelastic number (E), Prandtl number (Pr) and buoyancy parameters (Gc, Gt), etc.
324 citations
TL;DR: In this article, the effects of change in parameters of stretching ratio parameter (A ∗ ), nanoparticles volumetric fractions (∅ 2 ), magnetic parameter (β) and reciprocal magnetic Prandtl number (λ) on the functions including velocity, induced magnetic field and temperature for both Cu-water nanofluid and TiO2-Cu/water hybrid nanofluid.
300 citations
TL;DR: In this article, the authors considered various shapes of nanoparticles and found that platelet shape has the highest rate of heat transfer and Nusselt number enhances with increase of nanofluid volume fraction, Darcy, and Reynolds number while it reduces with an increase of Lorentz forces.
296 citations
TL;DR: In this article, the impact of Coulomb force on nanofluid forced convective heat transfer is examined using Fe3O4-Ethylene glycol nan ofluid.
268 citations
TL;DR: In this article, the influence of Lorentz forces on Fe 3 O 4 -water nanofluid is presented, where the radiation source term is taken in to account in energy equation and newly suggested model is imposed for viscosity of ferrofluid.
251 citations
TL;DR: In this paper, the effect of Lorentz forces on thermal conductivity of porous media and nanofluid has been investigated in the presence of a porous enclosure in a porous medium.
228 citations
TL;DR: In this article, a mesoscopic method is utilized to examine nanofluid forced convection in a three dimensional porous geometry in existence of uniform Lorentz forces, and the Lattice Boltzmann method is selected for this goal.
227 citations
TL;DR: In this paper, the influence of thermal radiation on nanofluid heat transfer in existence of Lorentz forces is investigated, and a correlation for average Nusselt number is extracted.
223 citations
TL;DR: In this paper, the Lattice Boltzmannian method is selected as mesoscopic approach for convective flow in cubic porous enclosure and the Brownian motion impact is taken into account via KKL model.
Abstract: Magnetohydrodynamic nanofluid convective flow in cubic porous enclosure is reported. Lattice Boltzmann Method is selected as mesoscopic approach. Brownian motion impact is taken into account via KKL model. Roles of Darcy number ( D a ) , Hartmann number ( H a ) , Rayleigh number ( R a ) , and Al 2 O 3 volume fraction ( ϕ ) are presented. Outputs are illustrated in forms of velocity contours, isokinetic energy, streamlines, isotherms and Nusselt number. Results indicate that temperature gradient over the hot surface augments with rise of Darcy numbers and ϕ while it reduces with augment of Lorentz forces. Nusselt number enhances with increase of buoyancy forces and permeability of porous media. Nanofluid motion enhances with augment of ϕ , D a , R a while it decreases with augment of H a .
TL;DR: In this paper, the influence of Coulomb forces on Fe3O4-H2O nanofluid thermal improvement in a cavity with moving wall is examined and the final formulas are solved via Control Volume based Finite Element Method.
TL;DR: In this paper, the impact of Lorentz forces on CuO-water nanofluid flow in a permeable enclosure is presented by means of CVFEM, where Darcy's law is applied for porous media.
TL;DR: In this article, the shape effect of nanoparticles and Brownian motion impact on nanofluid properties are taken into consideration and the solutions of final equations are obtained by CVFEM.
TL;DR: In this article, the authors address the simultaneous characteristics of thermal radiation and melting heat transfer effects in stagnation point flow of carbon nanotubes due to a stretching cylinder and compute numerical solutions numerically by fifth order Range-Kutta Fehlberg scheme.
TL;DR: In this article, the influence of external magnetic source on Fe3O4-water heat transfer in a cavity with circular hot cylinder is studied and a new numerical method is chosen namely CVFEM.
TL;DR: In this article, the natural convection of a CuO-water nanofluid in a permeable cavity is simulated using the Darcy law and the Brownian motion impact on the properties of the nanophase is taken into account using the KKL model.
Abstract: The natural convection of a CuO-water nanofluid in a permeable cavity is simulated using the Darcy law. The Brownian motion impact on the properties of the nanofluid is taken into account using the KKL model. The effect of Lorentz forces on the nanofluid hydrothermal behavior are considered. The control volume based finite element method is applied to solve the final equations. Roles of CuO-water volume fraction (
$\phi$
), Rayleigh (Ra) and Hartmann (Ha) numbers for a porous medium are reported. Results show that the Nusselt number decreases with increasing Ha but it increases with increasing $\phi$
, Ra.
TL;DR: In this article, the effect of magnetic field and internal heat generation on the free convection flow in a rectangular cavity was investigated, where the cavity is filled with a porous medium saturated with Cupper Cu-water nanofluid.
TL;DR: In this article, the effect of triangular, rectangular and trapezoidal ribs on the laminar heat transfer of water-Ag nanofluid in a ribbed triangular channel under a constant heat flux was numerically studied using finite volume method.
Abstract: In the present study, the effect of triangular, rectangular and trapezoidal ribs on the laminar heat transfer of water-Ag nanofluid in a ribbed triangular channel under a constant heat flux was numerically studied using finite volume method. Height and width of ribs have been assumed to be fixed in order to study the effect of different rib forms. Modeling were performed for laminar flow (Re=1, 50 and 100) and nanofluid volume fractions of 0, 2% and 4%. The results indicated that an increase in volume fraction of solid nanoparticle leads to convectional heat transfer coefficient enhancement of the cooling fluid, whereas increasing the Nusselt number results in a loss of friction coefficient and pressure. Also, along with the fluid velocity increment, there will be an optimal proportion between heat and hydrodynamic transfer behavior which optimizes performance evaluation criteria (PEC) behavior. Among all of the investigated rib forms, the rectangular one made the most changes in the streamlines and the triangular form has the best thermal performance evaluation criteria values. For all studied Reynold numbers, heat transfer values are least for rectangular rib from. Therefore, trapezoidal ribs are recommended in high Reynold numbers.
TL;DR: In this article, the velocity distribution for local Weissenberg number in case of shear thinning liquid reduces whereas it increments for shear thickening liquid and the results demonstrated that the results of presented analysis are compared with the available works in particular situations and reasonable agreement is noted.
TL;DR: In this article, the influence of melting heat transfer on magnetohydrodynamic nanofluid free convection is analyzed by means of CVFEM, where the KKL model is taken into account to obtain viscosity and thermal conductivity of CuO-water nano-drone.
TL;DR: In this article, heat transfer and pressure drop characteristic associated with minichannel heat sink is investigated experimentally and the results indicate that TiO2 nanofluid thermal performance is strongly dependent on heating power and its usefulness heat transfer characteristic could be achieved more effectively at lower heating power.
TL;DR: In this article, three dimensional simulations are presented by means of Lattice Boltzmann Method for nanofluid forced convection heat transfer in the presence of magnetic field.
TL;DR: In this article, a computational analysis has been performed in a horizontal channel with an open cavity filled with hybrid nanofluid of Al 2 O 3 - Cu -water having an adiabatic square obstacle inside.
TL;DR: In this article, the free convective heat transfer of the Al 2 O 3 -Cu water hybrid nanofluid in a cavity filled with a porous medium is investigated. And the experimental data show dramatic enhancement in the thermal conductivity and dynamic viscosity of the synthesized hybrid nano-luids, and hence, these thermophysical properties could not be modeled using available models of nanometrics.
TL;DR: In this paper, a tube receiver with pin fin arrays inserting was introduced as the absorber tube of a parabolic trough receiver to increase the overall heat transfer performance of the tube receiver.
TL;DR: In this paper, the boundary-layer flow of Maxwell nanomaterial saturating a non-Darcy porous medium is characterized by considering the Darcy-Forchheimer based model.
TL;DR: In this paper, the influence of T-semi attached rib on the turbulent flow and heat transfer parameters of a silver-water nanofluid with different volume fractions in a three-dimensional trapezoidal microchannel was explored.
Abstract: This study aimed at exploring influence of T-semi attached rib on the turbulent flow and heat transfer parameters of a silver-water nanofluid with different volume fractions in a three-dimensional trapezoidal microchannel. For this purpose, convection heat transfer of the silver-water nanofluid in a ribbed microchannel was numerically studied under a constant heat flux on upper and lower walls as well as isolated side walls. Calculations were done for a range of Reynolds numbers between 10,000 and 16,000, and in four different sorts of serrations with proportion of rib width to hole of serration width (R/W). The results of this research are presented as the coefficient of friction, Nusselt number, heat transfer coefficient and thermal efficiency, four different R/W microchannels. The results of numerical modeling showed that the fluid's convection heat transfer coefficient is increased as the Reynolds number and volume fraction of solid nanoparticle are increased. For R/W=0.5, it was also maximum for all the volume fractions of nanoparticle and different Reynolds numbers in comparison to other similar R/W situations. That's while friction coefficient, pressure drop and pumping power is maximum for serration with R/W=0 compared to other serration ratios which lead to decreased fluid-heat transfer performance.
TL;DR: In this article, the sensitivity analysis of heat transfer and heat exchanger effectiveness in a double pipe heat exchange with Al 2 O 3 nanofluid was investigated using the Response Surface Methodology (RSM) and two phase mixture model.
TL;DR: In this paper, the influence of carbon nanotubes in the Marangoni convection boundary layer flow of viscous fluid has been investigated and convergent series solutions are established for the resulting differential systems.