Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Coupling of chemical reaction and heat transfer

Please login with a confirmed email address before reporting spam

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 12 giu 2017, 03:38 GMT-4

Please login with a confirmed email address before reporting spam

Posted: 7 years ago 11 giu 2017, 13:28 GMT-4
Updated: 7 years ago 11 giu 2017, 14:47 GMT-4
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,

Please login with a confirmed email address before reporting spam

Posted: 7 years ago 12 giu 2017, 03:38 GMT-4
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.

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.