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 Seaspace March 22, 2002 21:46

How to calculate specific heat of mixture?

Hi, everyone,i am researching combustion of mixture between methane and air in porous media.But i do not know how to describe constant presssure specific heat,viscosity,enthalpy and heating value of the mixture.If anybody know ,please tell me.Thanks!!!

 Dean March 23, 2002 20:54

Re: How to calculate specific heat of mixture?

Check out any of the books on combustion theory, such as the class "Combustion Theory" by Forman Williams.

 seaspace March 24, 2002 00:15

Re: How to calculate specific heat of mixture?

Thanks for Dean's respones,but i checked some books on combustion,but no data provided about constant presssure specific heat,viscosity,enthalpy and heating value of the mixture.Can you give me more imformation? Thanks again!

 Jim Park March 24, 2002 18:30

Re: How to calculate specific heat of mixture?

I think everything you need can be calculated from the text book by Bird, Stewart, and Lightfoot, "Transport Phenomena." This is a classic for chemical engineers and has been around in various editions since at least the 60's.

It allows you to calculate at least estimates of the info you're seeking from first principles (molecular weight, etc).

Publisher is John Wiley.

 Neale March 24, 2002 22:50

Re: How to calculate specific heat of mixture?

For mixtures of pure substances, especially ideal gases, you can just assume an ideal mixture. Mixture properties are defined as the mas fraction weighted sum of the component properties. Any undergraduate thermodynamics text should cover ideal mixtures in more detail.

Neale.

 Dean March 25, 2002 02:55

Re: How to calculate specific heat of mixture?

Ok, I get it -- you want numbers, not the theory. Everything you need you should be able to dig out of GRI Mechanism 3.0 available at http://www.me.berkeley.edu/gri_mech The transport coefficients are given in the form of Lennard-Jones parameters, so you will have to dig out the formulas for viscosity, etc, including the mixture rules, from someplace such as Bird, Stewart, and Lightfoot. One point about combustion: to get the temperature right, you have to include the temperature dependence of the specific heats. Also, you need to get T right to get the chemistry right because the reaction rates depend exponentially on T.

Perhaps I can be more specific if you describe your problem in more detail. Premixed or diffusion flame? How much detail in the chemistry?

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