Zarcon Dee Grissom's Idea Page
Updated 09APR2008
Home > Ideas > The Heatpipe Dilemma.
The Heat pipe dilemma. Which end up?
Ever ask, why it worked for there tests, and not in your computer?
just how good are heat pipes, and are the current products for everyone?
can it work that way?
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The Heat pipe dilemma. which end up?

Heat pipes are an amazing form of refrigeration. heat vaporises a coolant in a tube, the hot gas rises in the tube to the cooler end where it is condensed, and the cool liquid falls back down to the hot end of the heat pipe.
heatpipe upright
This whole process, assumes that the hot gas can rise to the cool end, and the cool liquid can fall down to the hot end. Yes, orientation is that critical with a heat pipe.

Horizontal vs Vertical.
heatpipe verticle vs horizontal.
Even horizontal, heat pipes can be affective in transferring heat, even consuming minute amounts of heat energy in the vapor/liquid conversion process and moving the coolant around the pipe. However, only about half the heat-pipe's hot end is in contact with the cool coolant, the other half in contact with the hot vapor.

Upside down?
heatpipe upside down, wrong
What happens when a heat pipe is flipped upside down. Now the side that is supposed to be condensing the gas, is super-heating the gas. As the heat works it's way down the mettle tube, it vaporises even more of the coolant. This coolant moves to the top of the pipe where it is only heated more. With little, if any gas returning to liquid form, the pressure in the heat pipe begins to rise. Until the tube that contains the dangerous gas, can no longer contain the pressure. The only fatal question is, will the under-cooled processor or the tinsel strength of the heat-pipe's skin fail first.

 How fatal, is fatal?
In a tower setup, only the top of the cooler is affective in cooling, in most heat-pipe setups.
heatpipes, cooling cut in helf
Even with half the heat pipes up-right in a vertically mounted cooler, the other half are upside down.

What about the “U” shaped pipes?

With the heat at one leg of the “U”
heatpipe "C"heatpipe "C"
with these sideway like coolers, there really is only one way to use most of them. They tend to place each pipe at an angle away from the processor socket. so on it's side at least one pipe is upside down, so it will not function, if not all of them.

On a test bench, the “U” shaped products work as designed. The hot end is on the bottom, and the cool end is at the top of the cooler. Even with the pipe horizontal, so long as the liquid can flow under it's own power to the hot end, and the vapor can flow to the cool end, the product will function.
heat pipes uprightheat pipes on side
Mount the cooler so the pipe's ends are up, and the hot side becomes a small upside-down time bomb.
heat pipe gas trapheat pipe gas trap
Mount the cooler with the pipe ends down.and the liquid vaporises out of the hot end, and condenses in the cool end, with no way for gravity to get the liquid back to the hot end. In either case the cooler becomes no more affective then the outer skin of the heat pipe. Even if the pipe is made of copper, it is not enough to cool a power hungry CPU.
heat pipe emptyheat pipe empty

With the heat at the center of the “U”.
these products accentually double the effectiveness of the heat pipe, by placing the heat source at the center of the tube.
ninja on upright, heat pipes upright
However mount the cooler in a tower case, and the effectiveness can be cut in half, if not resulting with some pipes upside down. A dangerous proposition, for some computers.
ninja heat pipes on side

Is All lost for the tower PC?
There is hope, some of the products out there use pipes that do not bend when they leave the base, and come straight out to the end of the cooler. However, these coolers are heavy, and large. The tower coolers can put an enormous strain on the processor socket and/or motherboard.
chipset cooler on side half pipehorazontial chipset cooler double half pipe
Even some of the tower-coolers out there fall victim to some of there heat pipes being upside-down, on the wrong motherboard. like the ninja above.

BTW, Is room temp important?
I don't know what would happen, if room temp exceeded 100F. at what ambient temperature will the coolant in the cool end of the pipe stop condensing, rendering the cooler ineffective. No one has documented this on there site.

Mitigating circumstances and claims.
Some heat pipes have a wick like material inside that is supposed to help bring the liquid coolant back to the hot end of the pipe. If this were effective enough to compensate for gravity pooling the liquid the wrong direction, then there would not be a bunch of dead motherboards out there that use heat pipes between the V-regs and the north brig to cool the chip set. Bottom line, the most effective heat pipe solution will use gravity to pool the condensed liquid back down to the hot end of the pipe.

Wind, and air flow
even tho the pipes can help get heat away from the hot component, that heat still needs to be transfered to the air passing threw the heat sink fins. Some heat sinks are so big, they actually get in the way of the exhaust fans or intake fans on the back and side of some computer cases. Moving air dose not like to change direction quickly, nor dos large amounts of air go threw small openings efficiently.
Smutherd exhaust fan Limited room, and sharp angle air path
Here half of the exhaust fan is completely blocked by the heat sink, the other half sucking the same air the cooler is trying to pool in. reducing the effectiveness of both fans to move air. There is no where for the air to go after it passes threw the heat sink, except to go up the back side of the graphics card, and right back threw the cooler again... a so called circle of death. Here the exhaust fans can only get air squeezed from below the heat sink, after it has to completely change direction. top that with the coolers intake being flush up against the side cover of the case.

If your neck breaking computer is in a pizza-box or cake-box, there is a smorges board of coolers out there for you. However I don't know anyone with a pizza-box gaming machine, there all towers. It is essential to know, which way the socket, will place the cooler in your tower. Some coolers will not protect your processor with some motherboards.

heat pipe, This is BAD! Left; 2.1GHz Brisbane ALL Stock Speeds&V about 21C (70F) room temp, idling at over 71C (160F)... Idling on the BIOS screen! System refused to boot to any desktop, till the over temp protection was disabled. then would only function at the desktop for a few minutes before locking up solid to the point the reset and power switch on the front of the computer failed to function. Turn the heat sink around 90degrees by placing the case on it's front bezel, and system runs under full prime95 (two instances AKA dual core mode) load indefinitely at under 60C (140F). Place the case on it's side as if it was a cake-box, and the temps drop another three to five degrees Celsius.
Right; the same cooler is keeping a 2GHz single-core soc754 CPU at 35C (95F) or less under ANY load.
heat pipe, that Works.

In the end, I guess the best cooler would be assisted by the heat pipes. However would not rely on them to bring the heat to the cooling fins. Allowing a heat sink with heat pipes to be mounted in either 90 or 0 degrees relative to the socket clips couldn't be that difficult either.

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