OT: CPU heatsink "heat pipes"

Is it hype, or is it technology? I'm wondering what is the
usefulness of "heat pipes" in CPU heatsinks?

Seems to me that a "heat pipe" is not a pipe in the ordinary sense
of the word, so it isn't going to transport anything the way a pipe
does. I guess it is a solid rod of copper that conducts heat about
the same as any other shaped copper conducts heat. Would its use
have to do with the shape of the heatsink, perhaps allowing the
heatsink to fit into a narrower space or allowing an easier/cheaper
connection between the CPU contact area and the heatsink fins or
whatever?

Thank you.

 

Heat pipes are not solid. They have a liquid in them that is constantly
changing from a liquid to a gas and back. As it does so it transfers the
heat from the end connected to the cpu to the end at the cooling fins. They
are most commonly used in laptops so the heatsink and fan can be thin and
located in a convenient location.

 

Actually, about 100 times better than copper.

It allows a huge heatsink area to be thermally coupled to a small CPU
chip. Water cooling can do that, too.

John

 

Technology.

I'm wondering what is the

Works on the same principle as a radiator on a car.

--
Conor

I'm so grateful to the USA for their contribution to the war on terror.
After all, if they hadn't funded the IRA for 30 years, we wouldn't know
what terror was.

 

It transports heat, and does so by fluid transport.

Hollow, like a pipe, hence the name.

It doesn't conduct heat the way a solid does, it transports it via fluid
flow, and is orders of magnitude better than copper.

 

Well, there are some similarities but fundamental differences. A heatpipe
uses the heat itself, combined with either gravity or capillary action, as
the transport mechanism and, so, doesn't require a mechanical pump. It also
operates on phase change whereas water boiling in a car cooling system is
bad news.

 

Only for the "heatsink" part of the system; the heat pipe element is
something completely different.

I'd stick to driving trucks if I were you.

 

....

It's been very informative, thanks to all of the replies. The most
important information seems to be that the heat pipe is
exceptionally conductive.

 

http://en.wikipedia.org/wiki/Heatpipe

Fundamentally an enclosed tube with a bit of fluid in it
..
Fluid boils at one end, condenses at the other, then travels back through
gravity or capillary action along the tube wall.

The vapour can carry heat much faster than solid copper can conduct it.

The tube often has a partial vacuum so the fluid boils at around the
temperature the cooled device is intended to run at.

 

Do you know what convection is? The first car engines didn't have
waterpumps...

--
Conor

I'm so grateful to the USA for their contribution to the war on terror.
After all, if they hadn't funded the IRA for 30 years, we wouldn't know
what terror was.

 

Really? Care to explain how? It's using a moving fluid to transmit heat
away then passing the liquid via pipes through fins to dissipate the
heat. I wonder how a car cooling system works...oh yeah, the same.

I'd stick to working in Mcdonalds if I were you.



--
Conor

I'm so grateful to the USA for their contribution to the war on terror.
After all, if they hadn't funded the IRA for 30 years, we wouldn't know
what terror was.

 

Only half right. The last couple of steps in manufacturing a heat-pipe
involve compeletely evacuating it, ten distlling in the desired amount
of theworking fluid - usually water - then sealing off the tube.

The only vapour in a good heat pipe has come from the evaporation of
the working fluid, so that the "boiling point" of the working fluid is
always pretty much the temperature of the coolest point along the heat
pipe. You might get some pressure drop along the heat pipe as the
vapour flows from the hot spot from which it is boiling off to the
coolest point where it condenses, but this doesn't usually amount to
much.

A bad heat pipe - which hasn't been properly evacuated - doesn't work
too well at temperatures below those required to make the vapour
presure of the working fluid a good bit higher than the partical
pressure of the residual (non-condensing) gases.

 

A heatpipe is filled with a wick to transport fluid to the hot end,
from the cold end,at the hot end the fluid evaporates, goes to the
cold end ,condenses ,is sucked up by the wick and fed back to the
hot side. Evaporation takes a huge amount of heat,at a very small
change of temperature,(as in boiling water),so you can get a lot
of heat out of a small place, and bring it to a place were there is
room to get rid of it.
In one type of laptop I had open,they used the whole area below
the keyboard to get rid of the heat.
So the pipe really ships gas in one direction , and fluid in
the other(with the help of the wick).

 

Please read David Maynard's response. It's all about phase change
(liquid/vapour) and NOTanything like an automotive cooling system unless that
latter is in distress.

Maybe a google on "heat pipe" would assist your grasp.

 

No it ISN'T.

Wrong again.

 

http://en.wikipedia.org/wiki/Heat_pipe

Cheers!
Rich

 

No. In a car engine/radiator, the working fluid is the liquid. The
heat transfer medium is the liquid. The mechanism is conduction;
the "radiator" actually cools the fluid mostly by conduction. (to
the air, of course.)

In a heat pipe, the working fluid is vapor. The working fluid boils
at the hot end and condenses at the cold end, then wicks back to
the hot end as liquid. The mechanism of heat transfer is phase
change.

Hope This Helps!
Rich

 

Wait-- water? Vacuum? These are *atrocious* refrigerants! Wouldn't it
have to be a common refrigerating gas, such as perhaps a medium freon, or
butane? Under sufficient pressure of course. Pressure then varies with
temperature, as with any compressed liquified gas.

Tim