- #1

jaredogden

- 79

- 0

I searched for something relevant and came up short so forgive me if there is already a thread started on this.

I am taking a heat transfer class right now and am trying to figure out a few things.

My question arose when going over thermal resistances and how it relates to the general equations for conduction and convection.

I know the general equation for heat transfer due to conduction is q = kA(ΔT/L)

Also the heat transfer due to convection is q = hA(T

From my understanding these are the general relations, does this mean that we are neglecting the thermal resistances when we use these relations as if we were neglecting friction in a dynamics problem?

Are we then able to find the values for the resistances for a material based on its geometry and heat transfer coefficient and all that good stuff and then use a relationship like resistors in series?

Hopefully I'm making sense in all of this. Basically if I could sum it all up, are the general relations for heat transfer due to convection and conduction neglecting thermal resistance?

Small aside, can the thermal resistance of certain materials be understood sort of like the emissivity when finding heat transfer due to radiation in that the smaller the emissivity (the less the material acts like a blackbody) the less heat is transferred due to radiation?

EDIT: I just realized that my wording is off... the value of k for conduction is similar to resistance based on the material properties of the material you are dealing with, this allows less heat to transfer through plastic then say metal, this leads me to believe k can be thought of more like emissivity than thermal resistance since k is also a material property.

I am still however a little confused as to what thermal resistances are since k is also sort of like a thermal resistance.

I am taking a heat transfer class right now and am trying to figure out a few things.

My question arose when going over thermal resistances and how it relates to the general equations for conduction and convection.

I know the general equation for heat transfer due to conduction is q = kA(ΔT/L)

Also the heat transfer due to convection is q = hA(T

_{s}-T_{∞})From my understanding these are the general relations, does this mean that we are neglecting the thermal resistances when we use these relations as if we were neglecting friction in a dynamics problem?

Are we then able to find the values for the resistances for a material based on its geometry and heat transfer coefficient and all that good stuff and then use a relationship like resistors in series?

Hopefully I'm making sense in all of this. Basically if I could sum it all up, are the general relations for heat transfer due to convection and conduction neglecting thermal resistance?

Small aside, can the thermal resistance of certain materials be understood sort of like the emissivity when finding heat transfer due to radiation in that the smaller the emissivity (the less the material acts like a blackbody) the less heat is transferred due to radiation?

EDIT: I just realized that my wording is off... the value of k for conduction is similar to resistance based on the material properties of the material you are dealing with, this allows less heat to transfer through plastic then say metal, this leads me to believe k can be thought of more like emissivity than thermal resistance since k is also a material property.

I am still however a little confused as to what thermal resistances are since k is also sort of like a thermal resistance.

Last edited: