Engine overheat and altitude

[Hortlund]

Now, this is *really* not my field, but I just have to ask one question.

I thought heat=movement.

Because if heat=movement then friction becomes a key factor..right?

And thats why density is such a big player when we are talking about thermal capacity of air.

Less density=less particles=less interference of movement of molecules=not good heat absorber.

Thats why a vacum (space) sucks (hehe) when it comes to being a heat absorber.

Am I right or wrong so far?

[pbirmingham]

Originally posted by Hortlund:
Now, this is *really* not my field, but I just have to ask one question.

I thought heat=movement.

Because if heat=movement then friction becomes a key factor..right?

And thats why density is such a big player when we are talking about thermal capacity of air.

Less density=less particles=less interference of movement of molecules=not good heat absorber.

Thats why a vacum (space) sucks (hehe) when it comes to being a heat absorber.

Am I right or wrong so far?

Well, actually, though heat is movement on a molecular level, friction is not really a factor at this level.  For the most part, molecules act like billiard balls smacking into each other (this isn't exactly true, but it's pretty close for air at terrestrial temperatures.)

What happens is this: more density = more particles that can take energy from the thing  we're cooling = more heat capacity.

[pbirmingham]

Here's an interesting link about density and average temperature at various altitudes in the atmosphere.

Standard Atmosphere

It's where I got the numbers I used in my calculation of the maximum heat capacity of a volume of air.

[Hortlund]

You are of cource completely correct. Friction has nothing to do with anything. BUT when molecule 1 hits molecule 2, the speed of molecule 2 increases and that of molecule 1 decreases. Thus 1 gets "colder" and 2 gets "hotter".

[pbirmingham]

Originally posted by Hortlund:
You are of cource completely correct. Friction has nothing to do with anything. BUT when molecule 1 hits molecule 2, the speed of molecule 2 increases and that of molecule 1 decreases. Thus 1 gets "colder" and 2 gets "hotter".

Well, yes if the molecules are equally massive, although I hesitate to use statistical concepts like temperature on individual molecules.

Re: your sig -- I'll have to ask my wife about that.