Calculation of "thermal mass"

[WGEngr]

I have heard people talk about "thermal mass" of this or that material. The term thermal mass seems to have to do with thermal diffusivity. Can someone tell me what it is and how to calculate it?
Thanks

 

[butelja]

Mass*Specific Heat = Thermal mass

 

[JOM]

Dear WG,

I don't recall "thermal mass" being a formally defined term. As Butelja tells us, it is a term that describes the quantity of heat in a body. I don't think it needs precise defining, but rather competent useage of the term.

Sometimes you might use it to refer to the amount of heat stored in a body, in which case you have to include the body's temperature with reference to some datum, such as ambient. Then, your term would be calculated by mass*heat capacity*temp difference.

It's not "thermal diffusivity". By that I think you might mean conductivity, or perhaps, heat transfer rate.

Does that help?

Cheers,
John.

 

[WGEngr]

Dear John,

Thanks for your response. I better understand now, and am glad to hear that it hasn't been formally defined.

I have seen people use mass*heat capacity and density*heat capacity. I prefer density* heat capacity becuase it relates to thermal duffusivity.

By thermal diffusivity, I mean, alpha = conductivity/(density*heat capacity). This is the coefficient used in transient conductivity cases, cf A Heat Transfer Textbook, 3rd Edition pages 17-19.

http://web.mit.edu/lienhard/

http://www/ahtt.html

Thanks again and best wishes,
James