Joe-the_tattoo_artist

Compared to ceramics... yes, metals are poor conductors of heat.

And by the way, ceramics are capable of absorbing more heat than metals. This is how ceramic coated exhaust manifolds can be more efficient than non-coated ones at reducing engine bay temperatures.

Joe-the_tattoo_artist

It also illustrates the point of the article; that ceramic and ceramic lined engines are more thermaly efficient than a traditional all metal engine.

Arca_ex

iTrader: (10)

Alright I just think he's trolling at this point... but whatever. I'll try explaining this one last time.

First lets look at the meaning of the word conduct when used as a verb in this context.

Conduct (v): To serve as a channel or medium for (heat, electricity, sound, etc.)

Source: http://dictionary.reference.com/browse/conduct


So thermal conductivity is the efficiency at which a material can transmit heat from one material to another.

Now look at the attached picture. Lets assume that chambers A and C are filled with air at normal atmospheric pressure at about room temperature. Lets assume that these chambers are perfectly sealed to object B and can have no interaction with anything but object B.

For the first example, we'll have object B represent a solid piece of metal. If I were to instantly make chamber A 300 degrees, but chamber C was still room temperature, the metal would begin to CONDUCT heat energy from chamber A to chamber C until they reached equilibrium. If I were to coat this same piece of metal in ceramic, the time it takes for it to conduct that same amount of heat energy over to the other chamber would be LONGER than without the ceramic coating. Meaning that the bare metal is BETTER at conducting heat from one chamber to the other.


This is why we use ceramic coatings for headers, so that it conducts LESS heat from inside the headers to the outside of the headers, effectively lowering engine bay temperatures. Because it is LESS efficient at conducting heat.



I've also attached a chart of the thermal conductivity of common materials. Notice how Aluminum is about 250 times BETTER at conducting heat than wood? Also notice how Aluminum is about 4 times BETTER at conducting heat than stainless steel? What material a radiator is made out of still has a huge impact on its performance.

Also note that air and water are very poor thermal conductors.



Seriously if you're still that thickheaded after this explanation, go read this: http://en.wikipedia.org/wiki/Thermal_conductivity

kma5783

iTrader: (7)

NO Ceramics are worse conductors of heat compared to metals.


When a header is ceramic coated it acts as an insulator because the ceramic does not conduct heat as well as the metal below it, which is why heat remains in the header and the surface temp of a ceramic coated header is less than one without the coating.

Now if you talking about which will retain heat for a longer period of time I would say Ceramics, this does not make it a better conductor.

kma5783

iTrader: (7)

Thank you Arca_ex, but I don't think we are getting anywhere lol

Joe-the_tattoo_artist

Let me clarify that the thermal insulative properties of ceramics is how this works.

kma5783

iTrader: (7)

This post makes absolutely NO sense!!!! A material cannot be a good conductor and insulator at the same time.

Some of your posts are totally conflicting with eachother.

Arca_ex

iTrader: (10)

Insulation is referring to the R rating where R is resistance to heat transfer.

Materials with a high R rating, like ceramic, are poor heat conductors. Materials with low R ratings, like metals, are good heat conductors.

You CANNOT have a material that has a high R rating and is also a good conductor of heat. That doesn't make ANY sense.


But I'm pretty much done here if you're going to continue being this ignorant when multiple people have explained to you why your logic is backwards.

Joe-the_tattoo_artist

Perhaps I should mention that I am extremely tired and yet cannot sleep.

I meant to say the same things as you guys. I do understand it. My tired brain is making it difficult to make coherent sentences and lines of thought.

I seem to have mis-used the definitions of conductivity and insulation. When I wake up tomorrow and re-read what I posted, I am sure that I will be giving myself the biggest face-palm of them all in bewilderment of myself.

Joe-the_tattoo_artist

...due to back pain from a past construction injury.
At the moment my cognitive abilities are compromised. I am sure that some of you have done the same a time or two while intoxicated or what not.
I do humbly apologize for any misunderstanding. Don't hold it against me.

Ozimandious

Sorry about that... I posted the first thread and then came back and was unable to find it for some reason so I did a repost.