Radiated Heat

[dhuxted]

Can someone please explain to me why heat transfer from a floor to a body is termed radiated heat and not conduction heat?

[dhuxted]

could it not be said that electric floor heat is radiant, conductive and convective?

[David A. Andersen]

If you lay on the floor it's "conductive".

If the air becomes heated it will "convect".

If the heat energy passes through the air it "radiates".

It is called radiant heat because the majority of the heat transfer occurs during radiation not the other two. There is always a percentage that includes all three (except in outer space where convection and conduction do not occur).

[Marcel R. Cyr]

I like that answer Dave.
I got to remember that one myself.

[David A. Andersen]

Hope it wasn't too blunt!

I was on the phone...

Actually this is the most misconceived theory out there. Good question...

[dhuxted]

Not blunt great answer!
just finding it confusing between the three.

[David A. Andersen]

okay, long version...

conduction: heat transferred from molecule to molecule.

convection:heat transferred through a fluid, air or liquid.

Radiation: heat transferred through a gas (air), no contact or heat medium required.

Wasn't that long now was it?

[David A. Andersen]

just remember that all three types of heat transfer must equal 1.

conduction: .35
convection: .28
radiation: .37 = 1.0

[Bob Elliott]

Originally Posted by dhuxted

Not blunt great answer!
just finding it confusing between the three.

Should not be.
Think of closing your eyes on a sunny day with your face aimed at the sun.
The heat is radiating to your face.

(Sun-Space-Radiation)

When watching the Weatherman he talks about convection currents all the time.

(currents-convection-air streams)

Hmmm... someone think of a good one for conduction.

[David A. Andersen]

Walk bare foot across the street in the summer...

[Michael Larson]

Or Cat on a Hot Tin Roof

[Bob Elliott]

True but trying to think of a good metaphor with conduct.

[dhuxted]

Ya that's the def in the courses and that's were I get confused, where radiated heat is stated, I see it as conduction through contact (molecules) or even convection, as radiated heat should by nature only happen in space.
A fireplace is radiated heat or is it? could it not be convection or even conduction through the molecules of air? When a molecule hits another molecule it creates vibration which in turn creates heat. Is that conduction, convection or radiant?

[dhuxted]

so is in floor heating radiant or conductive?

[dhuxted]

and after going back to Davids answer #3 i think, I am answering my own questions.
However I don't get the =1 thing.