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Coupling of chemical reaction and heat transfer

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Hi to everyone,

I have to prepare a model describing a chemical reaction (dehydration of an hydrated salt).

I have to couple heat transfer interface, laminar flow interface and chemistry interface.

My doubt is the following: in the heat transfer interface, I have to insert the thermal conductivity, density and specific heat. I am using a constant value for the thermal conductivity. However, the density and specific heat will vary at each instant according to the fact that the salt is progressively dehydrated. From what I have understood, I can couple the density from chemical reaction interface to heat transfer, but how can I define the specific heat according to the degree of conversion of my reaction?

2 Replies Last Post Jun 12, 2017, 3:38 a.m. EDT

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Posted: 7 years ago Jun 11, 2017, 1:28 p.m. EDT
Updated: 7 years ago Jun 11, 2017, 2:47 p.m. EDT
Valeria,

You may define it as a variable:

Cp_mix = Cp1*x1 + Cp2*x2 + Cp3*x3 + ...

where xi are the mass fractions (which vary with time) and Cpi are the heat capacities of pure substances.

Note that it is a linear approximation. For a more accurate approximation, you need to find the heat capacity of the mixture by using thermodynamic relations and mixing rules, which I wouldn't do.

Amin,
Valeria, You may define it as a variable: Cp_mix = Cp1*x1 + Cp2*x2 + Cp3*x3 + ... where xi are the mass fractions (which vary with time) and Cpi are the heat capacities of pure substances. Note that it is a linear approximation. For a more accurate approximation, you need to find the heat capacity of the mixture by using thermodynamic relations and mixing rules, which I wouldn't do. Amin,

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Posted: 7 years ago Jun 12, 2017, 3:38 a.m. EDT
Thank you,

I will do it like that. I know it's an approximation, but for the specific case should be accurate enough.

Thank you, I will do it like that. I know it's an approximation, but for the specific case should be accurate enough.

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