Fanless or near fanless PC 2014 ? (sub 5 watts)

Thermal siphon = Heat pipe

On Monday, September 8, 2014 8:44:43 PM UTC, rickman wrote

Not really. A heat pipe is a tube which has some liquid in it. At the heat source the liquid changes to gas. The gas goes to the cool end of the tube where it condenses. The condensed liquid is transported by capillary action to the hot end of the tube.

A thermal siphon is all liquid. The liquid at the warm end expands and rises to the cool end where it gets denser. It then goes down a separate tube to the hot end.

Heat pipe one tube. Thermal siphon two tubes.

Dan

Yes, you are correct. :)

The main difference I believe is that the heat tube works pretty well. How well does the thermal siphon work? I thought about trying this once but I couldn't make myself believe it would move much water. I also had trouble figuring out how it would get started. I figured the heat source or the radiator needed to be in one of the riser tubes, best if one is in each. If the source and sink are both equally positioned over the two risers there would be equal pressure and not much flow if any. Will random fluctuations get it started? Will longer risers make it work better?

Den tirsdag den 9. september 2014 03.33.18 UTC+2 skrev snipped-for-privacy@krl.org:

the capillary action is really only needed when the pipe isn't vertical

-Lasse

Thermal siphons also work well or at least well enough for many things. No one ever said that a thermal siphon needs or should be symmetrical.

Dan

I'm asking about the symmetry. I gave thought to building one and realized it may need to have the heating and cooling sinks arranged to give a push to the initial flow. I believe it is the difference in pressure in the two columns that create the flow so that taller columns should work better. If I ever get back to cooling a desktop I may give this a try.

I gave thought to building one and

It needs to have the heating and cooling arranged so that it gives a push at all times. Longer tubes do help as well as bigger diameter tubes.

Dan

On Wed, 10 Sep 2014 00:48:54 -0400, rickman Gave us:

Just add a peltier plate to it.

I'm talking about getting it started. Just like an induction motor has a small number of coils which give the initial push to a stationary rotor, the heat source and cold source need to be a little offset so one chimney fills with the warm fluid and the other fills with the cold fluid. Otherwise it may not start up. But once in motion the hot and cold fluid will obviously follow the flow and continue the siphon.

As long as the hot pipe goes up at the start, and more than it does down, it will start.

Until the flow has started, which pipe is the hot pipe?

On 12 Sep 2014 22:25:37 GMT, Jasen Betts Gave us:

Reminds me of Rutger Hauer making "pattern".

Well... the machine they used anyway.

On Fri, 12 Sep 2014 18:37:07 -0400, rickman Gave us:

Usually, the esophagus.

the one that initially goes up the steepest.

to

push at all times. Longer tubes do help as well as bigger diameter tubes.

has

one

and

down, it will start.

The one headed up from the heat source. Density change starts the flow.

?-)

And if they both go straight up? That was my point. The fluid circuit needs to be designed with an asymmetry to assure that the thing will start up ok.

Ok, I see. One pipe is "up" from the heat source and the other pipe is "down" from the cold sink. So how does the unit tell which I intended to be up and which is down?

Sounds like you're trying to design-out metastability.

arranged to

a push at all times. Longer tubes do help as well as bigger diameter tubes.

has

so one

and

down, it will start.

flow.

The up pipe is top on both heat exchangers.

?-)