Free Convection in an Open Triangular Cavity Filled With a Nanofluid Under the Effects of Brownian Diffusion, Thermophoresis and Local Heater

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Nadezhda S. Bondareva ◽  
Mikhail A. Sheremet ◽  
Hakan F. Oztop ◽  
Nidal Abu-Hamdeh
Keyword(s):  
Heat Transfer ◽  
Buoyancy Force ◽  
Local Heat ◽  
Brownian Diffusion ◽  
Governing Equations ◽  
Transfer Enhancement ◽  
Two Phase ◽  
Force Magnitude ◽  
Flow And Heat Transfer ◽  
Buoyancy Ratio

Natural convection of a water-based nanofluid in a partially open triangular cavity with a local heat source of constant temperature under the effect of Brownian diffusion and thermophoresis has been analyzed numerically. Governing equations formulated in dimensionless stream function and vorticity variables on the basis of two-phase nanofluid model with corresponding initial and boundary conditions have been solved by finite difference method. Detailed study of the effect of Rayleigh number, buoyancy-ratio parameter, and local heater location on fluid flow and heat transfer has been carried out. It has been revealed that an increase in the buoyancy force magnitude leads to homogenization of nanoparticles distribution inside the cavity. A growth of a distance between the heater and the cavity corner illustrates the heat transfer enhancement.

Natural Convection of Nanofluids in Enclosures Heated Laterally and Underneath

2015 ◽  
Vol 737 ◽  
pp. 301-312 ◽  
Author(s):  
Marta Cianfrini ◽  
Roberto de Lieto Vollaro ◽  
Stefano Grignaffini ◽  
Massimo Corcione
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Brownian Diffusion ◽  
Particle Loading ◽  
Governing Equations ◽  
Transfer Enhancement ◽  
Temperature Dependent ◽  
Two Phase ◽  
Liquid Phases ◽  
Base Liquid

A two-phase mixture model is used to study natural convection in a square cavity filled with CuO+H2O nanofluids, in the hypothesis of temperature-dependent physical properties, assuming that Brownian diffusion and thermophoresis are the primary slip mechanisms between solid and liquid phases. The cavity is heated at one side and cooled at the opposite side, whereas the horizontal walls are assumed either both adiabatic, or the bottom heated and the top cooled. A computational code based on the SIMPLE-C algorithm is used to solve the system of the mass, momentum and energy transfer governing equations. It is found that, owing to the effects of the slip motion occurring between solid and liquid phases, the rate of heat transferred across the cavity by the nanofluid in the heating-from-below configuration is remarkably higher than that transferred by the pure base liquid. Moreover, in this particular configuration the addition of nanoparticles to the base liquid generates periodicity in heat transfer. Additionally, the heat transfer enhancement is discovered to increase as the imposed temperature difference is increased, showing a smooth maximum at an optimal particle loading.

scholarly journals Two-Phase Flow and Heat Transfer Enhancement

2013 ◽  
Vol 5 ◽  
pp. 256839
Author(s):  
Somchai Wongwises ◽  
Afshin J. Ghajar ◽  
Kwok-wing Chau ◽  
Octavio García Valladares ◽  
Balaram Kundu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Transfer Enhancement ◽  
Two Phase ◽  
Flow And Heat Transfer

scholarly journals Convective Heat Transfer of Ethanol/Polyalphaolefin Nanoemulsion in Mini- and Microchannel Heat Exchangers for High Heat Flux Electronics Cooling

2021 ◽  
Author(s):  
Jaime Rios ◽  
Mehdi Kabirnajafi ◽  
Takele Gameda ◽  
Raid Mohammed ◽  
Jiajun Xu
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Convective Heat ◽  
Phase Flow ◽  
Transfer Performance ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Two Phase ◽  
Flow And Heat Transfer

The present study experimentally and numerically investigates the flow and heat transfer characteristics of a novel nanostructured heat transfer fluid, namely, ethanol/polyalphaolefin nanoemulsion, inside a conventionally manufactured minichannel of circular cross section and a microchannel heat exchanger of rectangular cross section manufactured additively using the Direct Metal Laser Sintering (DMLS) process. The experiments were conducted for single-phase flow of pure polyalphaolefin (PAO) and ethanol/PAO nanoemulsion fluids with two ethanol concentrations of 4 wt% and 8 wt% as well as for two-phase flow boiling of nanoemulsion fluids to study the effect of ethanol nanodroplets on the convective flow and heat transfer characteristics. Furthermore, the effects of flow regime of the working fluids on the heat transfer performance for both the minichannel and microchannel heat exchangers were examined within the laminar and transitional flow regimes. It was found that the ethanol/PAO nanoemulsion fluids can improve convective heat transfer compared to that of the pure PAO base fluid under both single- and two-phase flow regimes. While the concentration of nanoemulsion fluids did not reflect a remarkable distinction in single-phase heat transfer performance within the laminar regime, a significant heat transfer enhancement was observed using the nanoemulsion fluids upon entering the transitional flow regime. The heat transfer enhancement at higher concentrations of nanoemulsion within the transitional regime is mainly attributed to the enhanced interaction and interfacial thermal transport between ethanol nanodroplets and PAO base fluid. For two-phase flow boiling, heat transfer coefficients of ethanol/PAO nanoemulsion fluids were further enhanced when the ethanol nanodroplets underwent phase change. A comparative study on the flow and heat transfer characteristics was also implemented between the traditionally fabricated minichannel and additively manufactured microchannel of similar dimensions using the same working fluid of pure PAO and the same operating conditions. The results revealed that although the DMLS fabricated microchannel posed a higher pressure loss, a substantial heat transfer enhancement was achieved as compared to the minichannel heat exchanger tested under the same conditions. The non-post processed surface of the DMLS manufactured microchannel is likely to be the main contributor to the augmented heat transfer performance. Further studies are required to fully appreciate the possible mechanisms behind this phenomenon as well as the convective heat transfer properties of nanoemulsion fluids.

scholarly journals Transient free convection in an inclined square porous cavity filled with a nanofluid using LTNE and Buongiorno’s models

2018 ◽  
Vol 240 ◽  
pp. 03014
Author(s):  
Mikhail Sheremet ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Inclination Angle ◽  
Equilibrium Temperature ◽  
Brownian Diffusion ◽  
Governing Equations ◽  
Nanofluid Flow ◽  
Porous Cavity ◽  
Flow And Heat Transfer ◽  
The Finite Difference Method ◽  
Porous Enclosure

The combined effect of Brownian diffusion, thermophoresis and cavity inclination angle on natural convective heat transfer in an inclined porous enclosure has been studied numerically. Fluid containing nanoparticles of low concentration circulates inside the cavity under the effect of the buoyancy force. Governing equations with corresponding boundary conditions formulated using the non-dimensional stream function and vorticity variables have been solved by the finite difference method. An influence of the cavity inclination angle, Darcy and Nield numbers on nanofluid flow and heat transfer has been investigated. It has been found that high Nield numbers illustrate more equilibrium temperature distribution inside the porous cavity.

NUMERICAL SIMULATION OF MIXED CONVECTION WITHIN NANOFLUID-FILLED CAVITIES WITH TWO ADJACENT MOVING WALLS

2013 ◽  
Vol 37 (4) ◽  
pp. 1073-1089 ◽  
Author(s):  
Mohammad Hemmat Esfe ◽  
Ariyan Zare Ghadi ◽  
Mohammad Javad Noroozi
Keyword(s):  
Heat Transfer ◽  
Richardson Number ◽  
Buoyancy Force ◽  
Simple Algorithm ◽  
Governing Equations ◽  
Nanofluid Flow ◽  
Flow And Heat Transfer ◽  
Case Rate ◽  
Finite Volume Approach ◽  
Opposing Effect

In this study, nanofluid flow and heat transfer in a cavity with two moving lids are investigated. Governing equations are solved by finite volume approach using SIMPLE algorithm over a staggered gird system. The results show that when the moving lids have opposing effect, the streamlines contain two main vortices. By increasing the Richardson number, intensity of the vortex complying with buoyancy force increases, while intensity of the other vortex decreases. When the moving lids have aiding effect, the streamlines contain one the primary dominant vortex in which its strength increases with increase of the buoyancy force. In this case, rate of heat transfer is more than other cases.

Effect of moving stretching sheets on natural convection in partially heated square cavity filled with nanofluid

2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Anil Kumar ◽  
Pentyala Srinivasa Rao
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Buoyancy Force ◽  
Volume Fraction ◽  
Governing Equations ◽  
Transfer Enhancement ◽  
Square Cavity ◽  
Flow Strength ◽  
Square Enclosure ◽  
Dimensionless Velocity

Abstract This article deals with the heat transfer enhancement due to buoyancy force in a partially heated square enclosure filled with nanofluids. The model is developed to analyse the behaviour of nanofluids taking into account of volume fraction and stretching parameter, when square horizontal walls are moving in opposite directions to each other. Implicit alternate direct finite difference method has been used to solve the governing equations of vorticity, energy, and kinematics. Graphically investigated the effect of physical pertinent controlling parameters on the dimensionless velocity, streamlines, isothermal, and Nusselt number. The obtained numerical solution achieves the best configuration for Rayleigh number 103 ≤ Ra ≤ 105, stretching parameter 0 ≤ τ ≤ 2.5, and volume fraction 0 ≤ ϕ ≤ 0.2. It is found that the stretching parameter and direction of moving walls affect the fluid flow, flow strength, and heat transfer in the cavity.

Transient natural convection in a partially open trapezoidal cavity filled with a water-based nanofluid under the effects of Brownian diffusion and thermophoresis

2018 ◽  
Vol 28 (3) ◽  
pp. 606-623 ◽  
Author(s):  
Nadezhda S. Bondareva ◽  
Mikhail A. Sheremet ◽  
Hakan F. Öztop ◽  
Nidal Abu-Hamdeh
Keyword(s):  
Natural Convection ◽  
Lewis Number ◽  
Brownian Diffusion ◽  
Governing Equations ◽  
Nanofluid Flow ◽  
Content Type ◽  
Average Temperature ◽  
Flow And Heat Transfer ◽  
Water Based ◽  
Buoyancy Ratio

Purpose The purpose of this paper is to study about the natural convection of water-based nanofluid in a partially open trapezoidal cavity under the influence of Brownian diffusion and thermophoresis. Design/methodology/approach Governing equations formulated in dimensionless stream function – vorticity variables – have been solved by finite difference method with a homemade code C++. Effects of Rayleigh number (Ra = 50-1,000), Lewis number (Le = 10-1,000), buoyancy-ratio parameter (Nr = 0.1-5.0), Brownian motion parameter (Nb = 0.1, 1.0) and thermophoresis parameter (Nt = 0.1, 1.0) on nanofluid flow and heat transfer have been studied. Findings It is found that high values of Rayleigh and Lewis numbers lead to the homogenization of nanoparticles distributions. For high values of Nt and Nb, heating is more essential and the cavity average temperature rises. Originality/value The originality of this work is to analyze natural convection in an open-sided trapezoidal cavity with Brownian diffusion and thermophoresis.

Combined Free and Forced Convection in Vertical Tubes with Radial Internal Fins

1981 ◽  
Vol 103 (3) ◽  
pp. 566-572 ◽  
Author(s):  
C. Prakash ◽  
S. V. Patankar
Keyword(s):  
Heat Transfer ◽  
Buoyancy Force ◽  
Finned Tube ◽  
Governing Equations ◽  
Finite Difference Technique ◽  
Flow And Heat Transfer ◽  
Buoyancy Forces ◽  
Free And Forced Convection ◽  
Internal Fins ◽  
Vertical Tubes

An analysis is made of the fully developed laminar flow and heat transfer in vertical tubes with radial internal fins to determine the influence of the buoyancy forces. The governing equations for velocity and temperature are solved by a finite difference technique which incorporates a special scheme for treating the two coupled variables. Results are presented for a range of the Rayleigh number and for various values of the fin height and the number of fins. The buoyancy force is found to increase significantly both friction and heat transfer in the finned tube; augmentation factors in the range of 5 to 10 are encountered. The effect of buoyancy is particularly strong when the number of fins is small and the fins are short.

Modeling of Nanofluid-Fluid Two-Phase Flow and Heat Transfer

2018 ◽  
Vol 15 (08) ◽  
pp. 1850072 ◽  
Author(s):  
Qiangshun Guan ◽  
Yit Fatt Yap ◽  
Hongying Li ◽  
Zhizhao Che
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Silicone Oil ◽  
Pure Water ◽  
Brownian Diffusion ◽  
Immiscible Fluid ◽  
Two Phase ◽  
Flow And Heat Transfer ◽  
Alumina Nanofluid ◽  
Buongiorno Model

This paper presents a model for two-phase nanofluid-fluid flow and heat transfer. The nonuniform nanoparticles are transported using Buongiorno model by convection, Brownian diffusion and thermophoresis. This is the first attempt to employ Buongiorno model for two-phase nanofluid-fluid flow. The moving interface between the nanofluid and the immiscible fluid is captured using the level-set method. The model is first verified and then demonstrated for coupled flow and heat transfer in (1) a water–alumina nanofluid-filled cavity with a rising silicone oil drop and (2) stratified flow of water–alumina nanofluid, pure water and silicone oil in a channel.

Effects of Particulate Diffusion on the Compressible Boundary-Layer Flow of a Two-Phase Suspension Over a Horizontal Surface

1998 ◽  
Vol 120 (1) ◽  
pp. 146-151 ◽  
Author(s):  
Ali J. Chamkha
Keyword(s):  
Heat Transfer ◽  
Mathematical Formulation ◽  
Fluid Phase ◽  
Brownian Diffusion ◽  
Particle Phase ◽  
Two Phase ◽  
Flow And Heat Transfer ◽  
Diffusion Temperature ◽  
General Power ◽  
Layer Flow

The problem of steady, laminar, compressible flow and heat transfer of a particulate suspension past a semi-infinite horizontal flat surface is formulated and solved numerically using an implicit finite-difference scheme. The mathematical formulation of the governing equations is based on the Eulerian description familiar from fluid mechanics where both phases are treated as two separate interacting continua. These equations account for Brownian diffusion which is important when the particle phase consists of very tiny particles and allow for a general power-law fluid-phase viscosity-temperature and particle-phase diffusion-temperature relations. Obtained flow and heat transfer results are illustrated graphically to show interesting features of this type of flow.

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