Effect of the magnetic field on the heat transfer coefficient of a Fe3O4-water ferrofluid using artificial intelligence and CFD simulation

2019 ◽  
Vol 134 (3) ◽  
Author(s):  
Ali Khosravi ◽  
Mohammad Malekan
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Artificial Intelligence ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cfd Simulation ◽  
The Heat Transfer Coefficient ◽  
The Magnetic Field

Conjugate Heat Transfer Analysis of Circular Microtube Under Time Varying Heat Source

2005 ◽  
Author(s):  
Abdullatif A. Gari ◽  
Muhammad M. Rahman
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Magnetic Material ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Transient Heat Conduction ◽  
Heat Transfer Analysis ◽  
Working Fluid ◽  
Heating And Cooling ◽  
The Magnetic Field

When a magnetic field is applied to a magnetic material it releases energy. It has been proven experimentally that this temperature rise could be as high as 20 K when a magnetic field of 10 T is applied. Heat is generated when the magnetic field is applied and cooling is produced when the magnetic field is released. The purpose of this study is to explore transient heat transfer coefficient when a fluid is circulated in the substrate through microchannels. Equations for the conservation of mass, momentum, and energy were solved in the fluid region. In the solid region, the transient heat conduction equation was solved. Gadolinium and water were picked as the magnetic material and working fluid respectively. The results are represented by plotting the variations of heat transfer coefficient and Nusselt number with time at various sections of the tube. The effects of the magnetic field strength, diameter of the microtube in the substrate, and Reynolds number were studied. It was found that the heat transfer coefficient changes with time in a periodic fashion when heating and cooling are generated in the system by repeated introduction and relaxation of the magnetic field. The results of this study will be useful for the development of microtube heat exchangers for a compact magnetic refrigerator.

scholarly journals Simulasi CFD Pengaruh Konsentrasi Nanofluida Al2O3/Air Terhadap Performa Perpindahan Panas Pipa Radiator

2020 ◽  
Vol 13 (2) ◽  
pp. 54
Author(s):  
Yoga Arob Wicaksono ◽  
Sudarno . ◽  
Nanang Suffiadi Akhmad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Single Phase ◽  
Heat Transfer Performance ◽  
Cfd Simulation ◽  
Simulation Method ◽  
Performance Of Heat Transfer ◽  
Pass Through ◽  
The Heat Transfer Coefficient

The performance of heat transfer on a car radiator can be improved by using nanofluids as working fluids. In this study analyzes the of heat transfer performance of Al2O3/water nanofluids that pass through cylindrical pipes in 3D using the CFD simulation method for single phase approach. This research studied the effect of nanofluid concentration  0.1, 0.5, 1 and 1.5% on the heat transfer coefficient. The Reynolds number is varied between 9000 to 23000 and the ambient temperature is constant. The results showed that 1.5% Al2O3/water nanofluid increasing heat transfer coefficient up to 5.7% compared to base fluid.

Analysis of Transient Heat Transfer in a Microchannel Heat Exchanger During Magnetic Heating of the Substrate Material

2003 ◽  
Author(s):  
Muhammad M. Rahman ◽  
Shantanu S. Shevade ◽  
Venkat Bethanabotla
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Generation ◽  
Solid Material ◽  
Transient Heat Transfer ◽  
Working Fluid ◽  
Systematic Analysis ◽  
The Magnetic Field

The paper presents a systematic analysis of heat transfer processes during the heat up and cool down phases of a magnetic material when subjected to a magnetic field. As a first step towards the development of a MEMS magnetocaloric refrigerator for hydrogen liquefaction, a computer simulation of fluid flow and transient heat transfer in microchannels was carried out. The study considered microchannels with rectangular and square cross sections with heat generation in the substrate due to imposed magnetic field. The results computed were for gadolinium substrate and water as the working fluid. In order to achieve the liquefaction of a cryogen such as hydrogen, heat need to be removed from the working fluid by taking the advantage of the demagnetization of the material when the magnetic field is removed. The purpose of this study is to explore the transient heat transfer coefficient when the fluid is circulated through the substrate via microchannels. The application of the magnetic field was simulated by using the concept of volumetric heat source distributed uniformly over the entire solid material. Because of the relatively small size of the MEMS device, the magnetic field strength is expected to be uniform throughout the material. The strength of the source was calculated from energy balance during magnetization of the material. From the simulation results, plots of Nusselt number and heat transfer coefficient over the length of the channel as well as locally at different sections were obtained. A thorough investigation for velocity and temperature distributions were performed by varying channel aspect ratio, Reynolds number, and heat generation rate in the channel.

Mist/Steam Cooling by a Row of Impinging Jets

2001 ◽  
Author(s):  
X. Li ◽  
J. L. Gaddis ◽  
T. Wang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cfd Simulation ◽  
Heated Surface ◽  
Impinging Jets ◽  
Stagnation Line ◽  
Round Jets ◽  
Steam Cooling ◽  
The Heat Transfer Coefficient

Closed loop steam has been chosen for cooling airfoils in heavy frame Advanced Turbine Systems (ATS) to improve efficiency. Enhanced cooling by the use of mist is considered to have potential to augment cooling by internal steam alone. Water droplets generally less than 10μm are added to 1.3 bar steam and injected through a row of four discrete round jets onto a heated surface. The Reynolds number is varied from 7500 to 22500 and the heat flux varied from 3.3 to 13.4 kW/m2. The mist increases the heat transfer coefficient along the stagnation line and downstream wanes in about 5 jet diameters. The heat transfer coefficient improves by 50 to 700 percent at the stagnation line for mist concentrations 0.75 to 3.5 percent by weight, depending on conditions. Off-axis maximum cooling occurs in most of the mist/steam flow but not in the steam-only flow. CFD simulation indicates that this off-axis cooling peak is caused by droplets’ interaction with the target walls.

Evaporation of lignin-lean black liquor

TAPPI Journal ◽  
2015 ◽  
Vol 14 (7) ◽  
pp. 441-450
Author(s):  
HENRIK WALLMO, ◽  
ULF ANDERSSON ◽  
MATHIAS GOURDON ◽  
MARTIN WIMBY
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Black Liquor ◽  
Salt Content ◽  
Solubility Limit ◽  
Lignin Removal ◽  
Kraft Black Liquor ◽  
Black Liquors ◽  
The Heat Transfer Coefficient

Many of the pulp mill biorefinery concepts recently presented include removal of lignin from black liquor. In this work, the aim was to study how the change in liquor chemistry affected the evaporation of kraft black liquor when lignin was removed using the LignoBoost process. Lignin was removed from a softwood kraft black liquor and four different black liquors were studied: one reference black liquor (with no lignin extracted); two ligninlean black liquors with a lignin removal rate of 5.5% and 21%, respectively; and one liquor with maximum lignin removal of 60%. Evaporation tests were carried out at the research evaporator in Chalmers University of Technology. Studied parameters were liquor viscosity, boiling point rise, heat transfer coefficient, scaling propensity, changes in liquor chemical composition, and tube incrustation. It was found that the solubility limit for incrustation changed towards lower dry solids for the lignin-lean black liquors due to an increased salt content. The scaling obtained on the tubes was easily cleaned with thin liquor at 105°C. It was also shown that the liquor viscosity decreased exponentially with increased lignin outtake and hence, the heat transfer coefficient increased with increased lignin outtake. Long term tests, operated about 6 percentage dry solids units above the solubility limit for incrustation for all liquors, showed that the heat transfer coefficient increased from 650 W/m2K for the reference liquor to 1500 W/m2K for the liquor with highest lignin separation degree, 60%.

scholarly journals Effect of Magnetic Field on the Forced Convective Heat Transfer of Water–Ethylene Glycol-Based Fe3O4 and Fe3O4–MWCNT Nanofluids

2021 ◽  
Vol 11 (10) ◽  
pp. 4683
Author(s):  
Areum Lee ◽  
Chinnasamy Veerakumar ◽  
Honghyun Cho
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Field Strength ◽  
Ethylene Glycol ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Hybrid Nanofluid ◽  
Forced Convective Heat Transfer ◽  
The Magnetic Field

This paper discusses the forced convective heat transfer characteristics of water–ethylene glycol (EG)-based Fe3O4 nanofluid and Fe3O4–MWCNT hybrid nanofluid under the effect of a magnetic field. The results indicated that the convective heat transfer coefficient of magnetic nanofluids increased with an increase in the strength of the magnetic field. When the magnetic field strength was varied from 0 to 750 G, the maximum convective heat transfer coefficients were observed for the 0.2 wt% Fe3O4 and 0.1 wt% Fe3O4–MWNCT nanofluids, and the improvements were approximately 2.78% and 3.23%, respectively. The average pressure drops for 0.2 wt% Fe3O4 and 0.2 wt% Fe3O4–MWNCT nanofluids increased by about 4.73% and 5.23%, respectively. Owing to the extensive aggregation of nanoparticles by the external magnetic field, the heat transfer coefficient of the 0.1 wt% Fe3O4–MWNCT hybrid nanofluid was 5% higher than that of the 0.2 wt% Fe3O4 nanofluid. Therefore, the convective heat transfer can be enhanced by the dispersion stability of the nanoparticles and optimization of the magnetic field strength.

scholarly journals Systematic heat transfer measurements in highly viscous binary fluids

2021 ◽  
Author(s):  
Ann-Christin Fleer ◽  
Markus Richter ◽  
Roland Span
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Volatile Component ◽  
Test Tube ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Low Viscosity ◽  
The Heat Transfer Coefficient

AbstractInvestigations of flow boiling in highly viscous fluids show that heat transfer mechanisms in such fluids are different from those in fluids of low viscosity like refrigerants or water. To gain a better understanding, a modified standard apparatus was developed; it was specifically designed for fluids of high viscosity up to 1000 Pa∙s and enables heat transfer measurements with a single horizontal test tube over a wide range of heat fluxes. Here, we present measurements of the heat transfer coefficient at pool boiling conditions in highly viscous binary mixtures of three different polydimethylsiloxanes (PDMS) and n-pentane, which is the volatile component in the mixture. Systematic measurements were carried out to investigate pool boiling in mixtures with a focus on the temperature, the viscosity of the non-volatile component and the fraction of the volatile component on the heat transfer coefficient. Furthermore, copper test tubes with polished and sanded surfaces were used to evaluate the influence of the surface structure on the heat transfer coefficient. The results show that viscosity and composition of the mixture have the strongest effect on the heat transfer coefficient in highly viscous mixtures, whereby the viscosity of the mixture depends on the base viscosity of the used PDMS, on the concentration of n-pentane in the mixture, and on the temperature. For nucleate boiling, the influence of the surface structure of the test tube is less pronounced than observed in boiling experiments with pure fluids of low viscosity, but the relative enhancement of the heat transfer coefficient is still significant. In particular for mixtures with high concentrations of the volatile component and at high pool temperature, heat transfer coefficients increase with heat flux until they reach a maximum. At further increased heat fluxes the heat transfer coefficients decrease again. Observed temperature differences between heating surface and pool are much larger than for boiling fluids with low viscosity. Temperature differences up to 137 K (for a mixture containing 5% n-pentane by mass at a heat flux of 13.6 kW/m2) were measured.

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