General Question

christinevincent1953's avatar

Which form of heat transfer travels the fastest,convection or conduction?

Asked by christinevincent1953 (1points) July 26th, 2012

transfer of heat via air currents (convection) or transfer of heat through a solid- eg metal door handle (conductor)

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7 Answers

XOIIO's avatar

Conductor. A solid object is much better at conducting than gas, that’s why wires are wired. Air has a higher resitance to change, but also changes more than a static object, with different currents and influencing variables like humidity, barometric pressure etc.

funkdaddy's avatar

I don’t think there is enough info here unfortunately. Is there something specific you’re looking for?

Convection moves the matter that is already heated, so a warm wind or the heat hitting you in the face from the oven could be convection.

Conduction instead moves the energy.

Either could move pretty quickly if you’re talking about “travels the fastest” in the sense of covering a distance.

CWOTUS's avatar

Welcome to Fluther.

What’s wrong with radiation?

If you’ve ever visited a hibachi restaurant you can often feel the radiated heat from when they light off the hibachi several tables away (or even a full room away) nearly instantaneously.

Other than that I would say “generally conduction”, although it matters greatly what the conductor is. If you light a fire in a fireproof safe, for example, you’ll feel the heat at the open door (convection) far sooner than you would through the conduction of the metal sides, since they’re insulated to protect against the heat. Materials matter. Also, if there are air / flue gas currents set up, the convective heat along that stream can travel as quickly as the convective media, too.

Setup matters. Materials matter.

tedd's avatar

If I remember correctly conduction works faster. If I recall correctly it has to do with the state the material is in. If it’s solid, then the heat/energy is quickly transferred to the next molecule in the material, and eventually out. That’s why metals heat up so quickly compared to water or air, and why they cool down faster. When you’re looking at a liquid or gas, the molecule has to come in contact with another molecule before it can transfer that energy, meaning it will take longer for it to be transferred away from the source.

RocketGuy's avatar

If you use a fast-moving liquid, you can get rid of heat really fast. That’s why there are liquid cooling systems in cars and nuclear reactors. There are even electronics cooling systems where the whole circuit board is immersed in a non-electrically conductive liquid, and the hot ICs boil the liquid that is flowing past.

tedd's avatar

If I’m not mistaken, we use liquid cooling because it takes more heat to vaporize it than it does to melt most of the metals we use, and we can quickly rotate in new liquid to accept the heat whereas the solid metal would be stationary.

jerv's avatar

@RocketGuy While convection takes place within all fluids regardless of density, the question only mentions gases, not liquids. I don’t feel like getting too deep into thermodynamics right now, but suffice it to say that it could be argued that all heat transfer is conduction and that liquid cooling works by conducting the heat from wherever into itself to be carried somewhere else (like a radiator) to be conducted away by a large volume (but small mass) of air.

The point is, air doesn’t transfer heat very well at all compared to, say, water or copper, so I say convection in gaseous mediums (like air) is the slowest.

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