https://wiki.nivel-teorico.com/index.php?action=history&feed=atom&title=Convec%C3%A7%C3%A3o_termomagn%C3%A9ticaConvecção termomagnética - Histórico de revisões2026-09-02T16:48:39ZHistórico de edições para esta página nesta wikiMediaWiki 1.40.1https://wiki.nivel-teorico.com/index.php?title=Convec%C3%A7%C3%A3o_termomagn%C3%A9tica&diff=5172&oldid=prevCalimero0000: uma edição2013-05-03T00:04:03Z<p>uma edição</p>
<p><b>Página nova</b></p><div>[[Ferrofluido]]s pode ser usado para [[Propagação térmica|transferir calor]], desde que o transporte de calor e [[Transferência de massa|massa]] em tais fluidos magnéticos podem ser controlados usando-se um [[campo magnético]] externo. <br />
<br />
[[Bruce A. Finlayson|B. A. Finlayson]] foi quem primeiro explicou, em 1970 (em seu artigo "Convective instability of ferromagnetic fluids", ''[[Journal of Fluid Mechanics]]'' '''40''':753-767, ''Instabilidade convectiva de fluidos ferromagnéticos'') como um campo magnético externo atuando sobre um ferrofluido com [[susceptibilidade variante]], ''e.g.'', devido a um gradiente de temperatura gradient, resulta em uma força de corpo magnético não uniforme, a qual conduz a '''convecção termomagnética'''. Esta forma de transferência de calor pode ser útil para casos onde a [[convecção]] convencional falha em prover adequada transferência de calor, ''e.g.'', em dispositivos de micro-escala ou sob condições de [[gravidade]] reduzida. <br />
<br />
Um grupo de pesquisadores liderados por Hiroyuki Ozoe tem estudado a convecção termomagnética tanto experimentalmente quanto numericalmente. Eles apresentaram como melhorar, suprimir e inverter os modos de convecção. <ref>Tomasz Bednarza, Toshio Tagawab, Masayuki Kanedab, Hiroyuki Ozoeb, Janusz S. Szmyd; [http://dx.doi.org/10.1080/10407780490457464 MAGNETIC AND GRAVITATIONAL CONVECTION OF AIR WITH A COIL INCLINED AROUND THE X AXIS]; Numerical Heat Transfer, Part A: Applications, Volume 46, Issue 1 July 2004 , pages 99 - 113</ref><ref>BEDNARZ TOMASZ, BEDNARZ TOMASZ, FORNALIK ELZBIETA, TAGAWA TOSHIO, OZOE HIROYUKI, SZMYD JANUSZ S.; [http://www.htsj.or.jp/TSE/TSE_14_4/TSE_14_4_7.pdf Convection of Paramagnetic Fluid in a Cube Heated and Cooled from Side Walls and Placed below a Superconducting Magnet-Comparison between Experiment and Numerical Computations]; Thermal Science & Engineering, VOL.14;NO.4;PAGE.107-114(2006) - [http://sciencelinks.jp/j-east/article/200622/000020062206A0906617.php Abstract em sciencelinks.jp] {{en}}</ref><ref>Tomasz Bednarza, John C. Pattersonb, Chengwang Leib and Hiroyuki Ozoe; [http://dx.doi.org/doi:10.1016/j.icheatmasstransfer.2009.06.005 Enhancing natural convection in a cube using a strong magnetic field — Experimental heat transfer rate measurements and flow visualization]; International Communications in Heat and Mass Transfer; Volume 36, Issue 8, October 2009, Pages 781-786</ref>. Eles tem também conduzido análise em escala para fluidos paramagnéticos em condições de [[microgravidade]]<ref>Tomasz P. Bednarza, Wenxian Linb, John C. Pattersonb, Chengwang Leib, and Steven W. Armfield; [http://dx.doi.org/10.1016/j.ijheatfluidflow.2009.08.003 Scaling for unsteady thermo-magnetic convection boundary layer of paramagnetic fluids of Pr > 1 in micro-gravity conditions]; International Journal of Heat and Fluid Flow; Volume 30, Issue 6, December 2009, Pages 1157-1170</ref>.<br />
<br />
<!--<br />
A comprehensive review of thermomagnetic convection (in A. Mukhopadhyay, R. Ganguly, S. Sen, and [[Ishwar K. Puri | I. K. Puri]], "Scaling analysis to characterize thermomagnetic convection", ''[http://www.elsevier.com/wps/find/journaldescription.cws_home/210/description International Journal of Heat and Mass Transfer]'' '''48''':3485-3492, (2005)) also shows that this form of convection can be correlated with a dimensionless magnetic [[Rayleigh number]]. Subsequently, this group explained that fluid motion occurs due to the presence of a [[Kelvin body forc]]e that has two terms. The first term can be treated as a magnetostatic pressure, while the second is important only if there is a spatial gradient of the fluid susceptibility, e.g., in a nonisothermal system. Colder fluid that has a larger magnetic susceptibility is attracted towards regions with larger field strength during thermomagnetic convection, which displaces warmer fluid of lower susceptibility. They showed that thermomagnetic convection can be correlated with a dimensionless magnetic Rayleigh number. Heat transfer due to this form of convection can be much more effective than buoyancy-induced convection for systems with small dimensions.<ref>[http://pof.aip.org/phfle6/v16/i7/p2228_s1?isAuthorized=no Phys. Fluids 16, 2228 (2004); doi:10.1063/1.1736691 (9 pages)]</ref><br />
<br />
The ferrofluid [[magnetization]] depends on the local value of the applied magnetic field '''H''' as well as on the fluid magnetic susceptibility. In a ferrofluid flow encompassing varying [[temperature]]s, the susceptibility is a function of the temperature. This produces a force that can be expressed in the [[Navier–Stokes]] or momentum equation governing fluid flow as the "Kelvin body force (KBF)". <br />
<br />
The KBF creates a static pressure field that is symmetric about a magnet, e.g., a line dipole, that produces a [[Curl (mathematics)|curl]]-free force field, i.e., curl('''ℑ''') = 0 for constant temperature flow. Such a symmetric field does not alter the velocity. However, if the temperature distribution about the imposed magnetic field is asymmetric so is the KBF in which case curl('''ℑ''') ≠ 0. Such an asymmetric body force leads to ferrofluid motion across [[isotherm]]s.<br />
<br />
--><br />
<br />
{{em tradução|:en:Thermomagnetic convection}}<br />
<br />
==Referências==<br />
<references/><br />
<br />
[[Categoria:Dinâmica de fluidos]]<br />
[[Categoria:Magnetismo]]</div>Calimero0000