What is Soret effect?

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 April 25, 2000, 10:19 Re: What is Soret effect? #1 Chuck Leakeas Guest   Posts: n/a The soret effect is where small light molecules and large heavy molecules separate under a temperatue gradient. Usually this effect is important where more than one chemical species is present under a very large temperature gradient such as CVD problems and chemical reactors. This effect is found when solving the species mass fraction equations. The Dufour effect describes the energy (heat) flux created when a chemical system is under a concentration gradient. This could also be important in CVD problems. This effect is found in the energy equation. The soret coefficient is the ratio of the thermal diffusion coefficient divided by the ordinary diffusion coefficient.

 May 25, 2000, 00:11 Re: What is Soret effect? #2 Jin Wook LEE Guest   Posts: n/a Dear Zeng Dufour Effect : Concentration gradients produce a heat flux. Soret Effect : Reverse of Dufour effect It is known that both Soret & Dufour effects are negligible, for most applications. Sincerely, Jinwook

 May 30, 2000, 06:00 Re: What is Soret effect? #3 s.venkat Guest   Posts: n/a Soret effect- This is a mass flux due to a temperature gradient and appears in the species continuity equation when you have a multicomponent mixture where each species has its own diffusional velocity. Dufor Effect-This is enthalpy flux due to a concentration gradient and appears in the energy equation for a multicomponent mixture.These effects depend on thermal diffusion which is generally very small but can be sometimes significant when the participating species are of widely differing molecular weights Venkat

 May 30, 2000, 06:00 What is Soret effect? #4 Zeng Guest   Posts: n/a Can you help me to understand: (1) Soret effect (2) Soret diffusion coefficent (3) Dufour effect Thanks in advance.

 June 14, 2012, 19:32 soret effect #5 New Member   Morteza Eslamian Join Date: Jun 2012 Posts: 6 Rep Power: 5 In isothermal mixtures of two or more species (gases, liquids and even solids), mass diffusion occurs if the species are initially distributed unevenly, i.e., when a concentration gradient exists. A temperature gradient can also work as a driving force for mass diffusion, in a phenomenon which is called thermodiffusion, thermal diffusion, or inliquid mixtures Soret (Ludwig-Soret) effect. Free open access paper on Soret effect http://www.thermalfluidscentral.org/...hp?a=206&g=242

 June 15, 2012, 04:04 #6 Senior Member   Join Date: Dec 2011 Location: Madrid, Spain Posts: 133 Rep Power: 6 Hi, as far as I know, Soret effect is not negligible when you compute the transport of light species (typically H radical in combustion applications). Cheers.

 June 15, 2012, 09:44 soret effect #7 New Member   Morteza Eslamian Join Date: Jun 2012 Posts: 6 Rep Power: 5 Whenever there is a temperature gradient in the mixture, Soret effect is present. The higher the temperature gradient, the larger the Soret effect. Pressure diffusion is usually negligible but not the Soret effect.

October 11, 2014, 16:38
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mohsen z
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Quote:
 Originally Posted by Chuck Leakeas ;8860 The soret effect is where small light molecules and large heavy molecules separate under a temperatue gradient. Usually this effect is important where more than one chemical species is present under a very large temperature gradient such as CVD problems and chemical reactors. This effect is found when solving the species mass fraction equations. The Dufour effect describes the energy (heat) flux created when a chemical system is under a concentration gradient. This could also be important in CVD problems. This effect is found in the energy equation. The soret coefficient is the ratio of the thermal diffusion coefficient divided by the ordinary diffusion coefficient.
I am confused.....on one side when we have temperature gradient the different species seperate to omit this gradient so temperature gradient decreases but the concentration gradient created as a result....so now due to dufour effect this concentration gradient should create heat flux that will lead to temperature gradient again....and now it is again soret effect turn and this cycle continues.....so when these two effects reach to a balance......?????????????????????????

October 11, 2014, 17:14
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mohsen z
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Quote:
 Originally Posted by eslamian Whenever there is a temperature gradient in the mixture, Soret effect is present. The higher the temperature gradient, the larger the Soret effect. Pressure diffusion is usually negligible but not the Soret effect.
I am confused.....on one side when we have temperature gradient the different species seperate to omit this gradient so temperature gradient decreases but the concentration gradient created as a result....so now due to dufour effect this concentration gradient should create heat flux that will lead to temperature gradient again....and now it is again soret effect turn and this cycle continues.....so when these two effects reach to a balance......?????????????????????????

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