Modeling of Thermomagnetic Phenomena in Active Magnetocaloric Regenerators

2014 ◽  
Vol 6 (3) ◽  
Author(s):  
Paulo V. Trevizoli ◽  
Jader R. Barbosa ◽  
Armando Tura ◽  
Daniel Arnold ◽  
Andrew Rowe
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Experimental Data ◽  
Solid Phase ◽  
Entropy Change ◽  
Porous Matrix ◽  
Cooling Capacity ◽  
Heat Transfer Fluid ◽  
Fluid Displacement ◽  
Matrix Heat Exchanger

The active magnetic regenerator (AMR) consists of a porous matrix heat exchanger whose solid phase is a magnetocaloric material (solid refrigerant) that undergoes a reversible magnetic entropy change when subjected to a changing magnetic field. The cooling capacity of the cycle is proportional to the mass of solid refrigerant, operating frequency, volumetric displacement of the heat transfer fluid and regenerator effectiveness. AMRs can be modeled via a porous media approach and a model has been developed in this work to simulate the time-dependent fluid flow and heat transfer processes in the regenerator matrix. Gadolinium (Gd) is usually adopted as a reference material for magnetic cooling at near room temperature and its magnetic temperature change and physical properties were accounted for through a combination of experimental data and the Weiss-Debye-Sommerfeld (WDS) theory. In this paper, the interaction of the applied magnetic field waveform with the heat transfer fluid displacement profile and the influence of demagnetizing effects on the AMR performance are investigated numerically. The numerical model is evaluated against experimental data for a regenerator containing spherical Gd particles.

Modeling of Thermo-Magnetic Phenomena in Active Magnetic Regenerators

2013 ◽  
Author(s):  
Paulo V. Trevizoli ◽  
Jader R. Barbosa ◽  
Armando Tura ◽  
Daniel Arnold ◽  
Andrew Rowe
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Solid Phase ◽  
Porous Matrix ◽  
Cooling Capacity ◽  
Working Fluid ◽  
Active Magnetic Regenerator ◽  
Flow And Heat Transfer ◽  
Magnetic Cooling ◽  
Matrix Heat Exchanger

The active magnetic regenerator (AMR) is at the heart of the thermo-magnetic Brayton cooling cycle. It consists of a porous matrix heat exchanger whose solid phase is a magnetocaloric material (solid refrigerant) that undergoes a reversible magnetic phase transition when subjected to a changing magnetic field. The cooling capacity of the cycle is proportional to the mass of solid refrigerant, operating frequency, volumetric displacement of the working fluid (generally an aqueous solution) and regenerator effectiveness. AMRs can be modeled via a porous media approach and a model has been developed to simulate the time-dependent fluid flow and heat transfer processes. Gadolinium (Gd) is usually adopted as a reference material for magnetic cooling at near room temperature and, in this study, its magnetic temperature change and physical properties were accounted for using a combination of experimental data and the Weiss-Debye-Sommerfeld theory. In this paper, the influence of the applied magnetic field waveform and of demagnetizing effects on the AMR performance is investigated numerically. An evaluation of the model is also carried out in the light of a comparison against experimental data for a regenerator containing spherical Gd particles.

Free convection in a square porous cavity filled with a nanofluid using thermal non equilibrium and Buongiorno models

2016 ◽  
Vol 26 (3/4) ◽  
pp. 671-693 ◽  
Author(s):  
Ioan Pop ◽  
Mohammad Ghalambaz ◽  
Mikhail Sheremet
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Brownian Motion ◽  
Base Fluid ◽  
Average Nusselt Number ◽  
Solid Phase ◽  
Porous Matrix ◽  
Governing Equations ◽  
Content Type ◽  
Brownian Motion And Thermophoresis

Purpose – The purpose of this paper is to theoretically analysis the steady-state natural convection flow and heat transfer of nanofluids in a square enclosure filled with a porous medium saturated with a nanofluid considering local thermal non-equilibrium (LTNE) effects. Different local temperatures for the solid phase of the nanoparticles, the solid phase of porous matrix and the liquid phase of the base fluid are taken into account. Design/methodology/approach – The Buongiorno’s model, incorporating the Brownian motion and thermophoresis effects, is utilized to take into account the migration of nanoparticles. Using appropriate non-dimensional variables, the governing equations are transformed into the non-dimensional form, and the finite element method is utilized to solve the governing equations. Findings – The results show that the increase of buoyancy ratio parameter (Nr) decreases the magnitude of average Nusselt number. The increase of the nanoparticles-fluid interface heat transfer parameter (Nhp) increases the average Nusselt number for nanoparticles and decreases the average Nusselt number for the base fluid. The nanofluid and porous matrix with large values of modified thermal capacity ratios (γ p and γ s ) are of interest for heat transfer applications. Originality/value – The three phases of nanoparticles, base fluid and the porous matrix are in the LTNE. The effect of mass transfer of nanoparticles due to the Brownian motion and thermophoresis effects are also taken into account.

Experimental Investigation of Thermal Storage Processes in a Thermocline Storage Tank

2011 ◽  
Author(s):  
Wafaa Karaki ◽  
Peiwen Li ◽  
Jon Van Lew ◽  
M. M. Valmiki ◽  
Cholik Chan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Storage Tank ◽  
Power Plants ◽  
Thermal Power ◽  
Energy Charge ◽  
Thermal Storage ◽  
Packed Bed ◽  
Heat Transfer Fluid ◽  
Energy Storage Efficiency

This paper presents an experimental study and analysis of the heat transfer of energy charge and discharge in a packed-bed thermocline thermal storage tank for application in concentrated solar thermal power plants. Because the energy storage efficiency is a function of many parameters including fluid and solid properties, tank dimensions, packing dimensions, and time lengths of charge and discharge, this paper aims to provide experimental data and a proper approach of data reduction and presentation. To accomplish this goal, dimensionless governing equations of energy conservation in the heat transfer fluid and solid packed-bed material are derived. The obtained experimental data will provide a basis for validation of mathematical models in the future.

scholarly journals Thermal Conductivity of Metastable Ionic Liquid [C2mim][CH3SO3]

Molecules ◽  
2020 ◽  
Vol 25 (18) ◽  
pp. 4290 ◽  
Author(s):  
Daniel Lozano-Martín ◽  
Salomé Inês Cardoso Vieira ◽  
Xavier Paredes ◽  
Maria José Vitoriano Lourenço ◽  
Carlos A. Nieto de Castro ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Ionic Liquid ◽  
Melting Point ◽  
Solid Phase ◽  
Freezing Point ◽  
Phase Region ◽  
Heat Transfer Fluid ◽  
Diphenyl Oxide ◽  
Conductivity Models

Ionic liquids have been suggested as new engineering fluids, namely in the area of heat transfer, as alternatives to current biphenyl and diphenyl oxide, alkylated aromatics and dimethyl polysiloxane oils, which degrade above 200 °C and pose some environmental problems. Recently, we have proposed 1-ethyl-3-methylimidazolium methanesulfonate, [C2mim][CH3SO3], as a new heat transfer fluid, because of its thermophysical and toxicological properties. However, there are some interesting points raised in this work, namely the possibility of the existence of liquid metastability below the melting point (303 K) or second order-disorder transitions (λ-type) before reaching the calorimetric freezing point. This paper analyses in more detail this zone of the phase diagram of the pure fluid, by reporting accurate thermal-conductivity measurements between 278 and 355 K with an estimated uncertainty of 2% at a 95% confidence level. A new value of the melting temperature is also reported, Tmelt = 307.8 ± 1 K. Results obtained support liquid metastability behaviour in the solid-phase region and permit the use of this ionic liquid at a heat transfer fluid at temperatures below its melting point. Thermal conductivity models based on Bridgman theory and estimation formulas were also used in this work, failing to predict the experimental data within its uncertainty.

Effects of magnetic field and viscous dissipation on entropy generation of mixed convection in porous lid-driven cavity with corner heater

2016 ◽  
Vol 26 (5) ◽  
pp. 1548-1566 ◽  
Author(s):  
Sameh E Ahmed ◽  
Hakan F. Öztop ◽  
Khaled Al-Salem
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Mixed Convection ◽  
Viscous Dissipation ◽  
Entropy Generation ◽  
Hartmann Number ◽  
Heat Transfer Fluid ◽  
Content Type ◽  
Driven Cavity ◽  
Corner Heater

Purpose – The purpose of this paper is to investigate the effects of magnetic field and viscous dissipation on mixed convection heat transfer, fluid flow and entropy generation in a porous media filled square enclosure heated with corner isothermal heater. Design/methodology/approach – Finite volume method has been used to solve governing equations. A code is developed by FORTRAN and entropy generation is calculated from the obtained results of velocities and temperature. Results are presented via streamlines, isotherms, local and mean Nusselt number for different values of Richardson number (0.001=Ri=100), Hartmann number (0.001=Ha=100), Darcy number (0.001=Da=0.1), length of heaters (0.25=hx=hy=0.75) and viscous dissipation factors (10−4=ε=10−6). Findings – It is observed that entropy is generated mostly due to lid-driven wall and right side of the heater. Entropy generation decreases with increasing of Hartmann number and heat transfer increases with decreasing of viscous parameter. Originality/value – The originality of this work is to application of magnetic field and viscous dissipation on entropy generation in a lid-driven cavity with corner heater. Here, both corner heater and the external forces are original parameters.

Numerical and experimental study of heat transfer in gas-solid flow: Particle cooling

2012 ◽  
Vol 3 (1) ◽  
pp. 21-29
Author(s):  
S. M. El-Behery ◽  
W. A. El-Askary ◽  
M. H. Hamed ◽  
K. A. Ibrahim
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Experimental Study ◽  
High Speed ◽  
Solid Phase ◽  
Ideal Gas ◽  
Particle Rotation ◽  
Two Phase ◽  
Solid Flow ◽  
Speed Flow

Abstract Heat transfer in gas-solid two-phase flow is investigated numerically and experimentally. The numerical computations are carried out using four-way coupling Eulerian-Lagrangian approach. The effects of particle rotation and lift forces are included in the model. The gas-phase turbulence is modeled via low Reynolds number k-ε turbulence models. The SIMPLE algorithm is extended to take the effect of compressibility into account. The experimental study is performed using crushed limestone to simulate the solid phase. The effects of Reynolds numbers, particles size and temperature on the pressure drop and the temperature of the phases are investigated. The model predictions are found to be in a good agreement with available experimental data for high speed gas-solid flow and present experimental data for low speed flow. The present results indicate that heat transfer in gas solid flow can be modeled using ideal gas incompressible flow model at low conveying speed, while for high speed flow, a full compressible model should be used.

GRAVITATIONAL AND MAGNETIC CONVECTION IN MAGNETIC FLUID

2005 ◽  
Vol 19 (07n09) ◽  
pp. 1367-1373
Author(s):  
A. A. BOZHKO ◽  
G. F. PUTIN
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Solid Phase ◽  
Fluid Flows ◽  
Homogeneous Magnetic Field ◽  
Temperature Sensors ◽  
Cylindrical Layer ◽  
Temperature Sensitive ◽  
Concentration Gradients ◽  
The Stability

Experiments were performed to examine the influence of external homogeneous magnetic field on ferrofluid convection in thin cylindrical layer heated from one wide sidewall and cooled from another. Gravitational and magnetic mechanisms of convection as well as the influence of gravitational sedimentation of particles and their aggregates on stability and structure of fluid flows are studied. The integral and local temperature sensors were used for measurement of heat transport across the layer. Visualization of flow patterns was provided by a temperature-sensitive liquid crystal sheet. The results indicate that with the help of a magnetic field it is possible to control the stability and the form of convection motions. Besides, the concentration gradients of solid phase can have material role to convection instability and heat transfer.

scholarly journals Large magnetic entropy change and prediction of magnetoresistance using a magnetic field in La0.5Sm0.1Sr0.4Mn0.975In0.025O3

RSC Advances ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 5395-5406 ◽  
Author(s):  
M. Dhahri ◽  
J. Dhahri ◽  
E. K. Hlil
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Rietveld Refinement ◽  
Magnetic Entropy Change ◽  
Calculated Data ◽  
Entropy Change ◽  
Magnetic Entropy ◽  
Vertical Bars

Rietveld refinement for the sample LSSMIO. Experimental data (the point symbols), calculated data (the solid lines), difference between them is shown at the bottom of the diagram and Bragg positions are marked by vertical bars.

scholarly journals The Influence of Inclined Magnetic Field and Heat Transfer on the MHD Convective Flow in a Vertical Channel Filled Partly with Porous Medium

2019 ◽  
Vol 8 (3S2) ◽  
pp. 994-1002
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Convective Flow ◽  
Vertical Channel ◽  
Mhd Flow ◽  
Darcy Number ◽  
Porous Matrix ◽  
Inclined Magnetic Field ◽  
Parallel Plates ◽  
Velocity Flow

An analyticstudy has been madeof a laminar fully developed MHD flow bounded by infinite vertical parallel plates with effect of inclined magnetic fieldpartly filled with fluid and partly with porous matrix. The motions of the plates are in the opposite direction and are maintained at distinct temperatures. The perturbation method has been chosen to derive the expression for velocity flow and temperaturedistributionand the effect on flow velocity and temperature due to magnetic field and Darcy number has been illustrated for the fluid and porous region with the helpof graph.

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