# Heat transfer of hot metal immersed in water

## Main Question or Discussion Point

if you plunge a hot metal (like wire) into water, the water temperature obviously increases. I wonder what kind of heat transfer occurs between the metal and the water.
it clearly doesn't seem like convection or radiation. But im not so sure if conduction is the right one cos it is usually explained in the context of two solids in contact.

can anyone explain in detail how the heat is transferred from the hot metal to water?
and also whether the rate of transfer depends on the temperature difference.

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It's conduction you're looking for.

I'd also point out that if the water temperature is above that of the metal then the water temperature will decrease.

Conduction at first, but if the metal is sufficiently hot, then I believe a layer of water vapor can form between both. And it would seem to me that this layer could well allow convection and maybe also radiation.

Shouldn't there always some heat transfer in the form of radiation? Although I assume it's negligible in the context. I mean, don't we have from Stefan-Boltzmann's law that radiated power is something like P= k * sigma * T^4, where 0<k<1 is a constant describing how close to a perfect black body the rod is?

And also (which I think was in part what the original question was about), how is the conduction happening in detail? Is it something like that the outer atoms in the metal rod "give away" thermal energy to the surrounding water molecules until they are in equilibrium (also, thermal energy is transported from the inner parts of the rod to the surface)? Can one think of the transfer of thermal energy from the rod to the water as collisions between surface atoms in the rod and water molecules? (Note that all this is assuming that the water is at a lower temperature than the rod.)

At the wall there is always pure conduction due to the no slip boundary condition. The process can be described as kloptok put it.

Free convection can happen outside of that layer due to buoyancy forces. Radiation is always in play as well.

Mapes