Thread: Another Cooling idea from a dreamer...

Originally Posted by evandude

The amount of heat the radiator dissipates is proportional to the difference in temperatures of the water and the ambient air, which is why a water cooling system will reach a stable temperature... it's the equilibrium point, where the amount of heat dissipated by the radiator equals the amount generated by the CPU, and it depends on the amount of heat being produced by the CPU, and the temperature of the outside air. (assuming the fan speed stays the same)

However, the job of a thermostat in a car is to allow the engine to heat up.
http://auto.howstuffworks.com/question248.htm

a car's thermostat stays OPEN above a certain temperature, so it allows constant flow when the temperature is above that level, and allows no flow when the temp is below. if it was intended to cool water to a certain temp before releasing it, then it would have to work the opposite way (open when cooler than that temp, closed when hotter) This differs from a computer water cooling system in that an engine is supposed to be at a certain operating temp, and a computer must just be as cool as possible... but the point is, the coolant should be circulating whenever the engine is too hot, not sitting in the radiator. The hotter the radiator water is, the faster heat is removed, so allowing radiator water to be cooler than engine water would not make things cool faster.

Look at your description; you're contradicting yourself. what happens if the water in the engine AND the water in the radiator are above the thermostat temp? it stays wide open until the temperature falls below its set temp. having the water in continuous flow removes the most heat... the thermostat is making sure the temperature doesn't go BELOW its set temp, not above... when the temp is above, it's the radiator's job to get it back down.

if what you say is true, that allowing continous flow doesn't remove enough heat, then the engine would overheat if the radiator water and engine water were hotter than the thermostat set temp (it would never close, so you'd have continuous flow)

also:
"Yes, But it takes more energy to go faster so it produces more heat."
I think that's completely irrelevant. The amount of energy it takes to pump coolant through a cooling system is just a drop in a bucket compared to the amount of energy being consumed by the device generating the heat. not to mention, water pumps generally do not produce significant heat. The water pump I had when water cooling my computer was warm to the touch, never hot. even going to a higher-flow pump would still produce an insignificant heat increase compared to the heat of the processor.

Ok, We are comparing two things that don't relate to each other completly..... To illistrate my point, go out and pull the thermastat out of your car, drive it on a hot day non stop and see if it doesn't overheat. It will most difinatly. Trust me.

A car with a stuck open thermastat will take longer to warm up but will eventually over heat. A car with a stuck closed thermastat will heat up and never cool down, Just boil itself. so it will over heat much quicker.


Most automotive thermastats operate between 165 and 200 degrees. Get a temp probe and point it at the top rad hose, You can watch it cycle, It will go up to what ever the temp of the thermastat is, then it will drop about 5 to 10 degrees, then it will climb again, then drop, and so on.

No, A water pump doesn't create the heat,it will create some, but the engine is what creates it...or in our case the cpu and other components of our computers. The water pump just keeps it circulating.

Anyway, This is getting kind of off topic so I am done.

Originally Posted by BADDERICK

Yes, But it takes more energy to go faster so it produces more heat. I am a certified mechanic. The thermastat in a car holds the water in the engine until it reaches a specified temprature. That also allows the water in the radiator time to cool. if it passes through the radiator to quickly not enough heat is disapated so the water doesn't cool enough, then it goes back to the engine being heated more because it wasn't cool enough to cool it down, the longer this cycle continues the hotter the water gets. It needs to spend long enough inb the radiator for the heat exchange to take place.



Yes, this is kind of confusing.

i am also a certified mechanic and you are so wrong is unreal
the thermastat in a car is simply to help the engine get up to temp as fast as poss.
they do not control the flow of water after that temp has been reached they are permanently open.
the water system of the car has been designed to keep the car at that temp (rad size ,water flow from pump and vol ).
if the temp of the car does rise for some reason (very hot day or so on )thats why they have fans

badderick is a mechanic from way back I'm guessing...because he is right, as far as older cars go anyway..... you take an american v8 in a typical install.. which was comprised of a copper radiator & a clutch driven fan in a shroud......not very efficient....

the design was such that when the engine reached 185-190 (example only) the thermostat would open & the hot 200 degree water would flow into the radiator...for the most part the block would empty of 200 deg water & fill with say 140 deg water from the rad....... when the thermostat level was reached with this cooler water it would close..... the engine would proceed to heat the incoming water to 185-190..... this would take 1-2 min give or take..... at that time the radiator has accepted the 200 deg water & is now holding it & cooling it for those same 1-2 minutes... allowing it to cool enough so that it would be well under the original temp....

this design worked well unless there was a problem somewhere..... but he is right... if you took the thermostat out of a typical install as above... the radiator wouldn't hold the water long enough to cool it under hot conditions & not moving at high speeds.... the car will overheat.... because of no thermostat... which EVEN WHEN OPENED IS STILL A RESTRICTOR......no thermostat translates to higher flow.... which only compounded the problem...... racers used to play around with fixed restrictor plates instead of a thermostat to try to have more control........

modern cooling systems are different in many ways.... & this flow/hold sinario is less necissary or primary in design...... but can still be a factor..... although on modern cars the thermostats primary purpouse is to allow the engine to heat to operating temps as fast as possible for emmisions & closed loop operation......

hey maybe your both right & both wrong......

Did you just call me old :P

actually it is relivant because cooling a pc in a car with liquid(watter wetter works great) cannot be approached like cooling a pc in a house......the small lines & small pumps used in conventional pc water cooled systems will not work great in a car...... simply because to install a water cooling system in a car will take very long runs of tubing/hose..... it will need to be much bigger in diamiter & the pump will need to be much bigger too...forget those tiny pumps & tiny tubes... unless your radiator is just inches away... which isn't the best way to begin with......

to liquid cool a pc in a car you should use a radiator mounted in airflow....most practical is in the grille like a tranny cooler....which would make a great radiator for this type of install by the way..... using copper tubing to & from in stratigic spots will help dissipate heat even more...... you will have to use a pump much larger than what is normally used for a pc.... you basically need to build an aux cooling system... not an off the shelf pc liquid cooling solution.....

I think this thread has been officially hijacked

Okay, let me say this: I am not trying to be a dick, this is a scientific argument to me; I am not convinced I am right, I am just basing my opinion on what i know, and if someone can prove to me that I'm wrong, honestly, I'd welcome that as well... I just want to understand the physics of it. I'm under no misconceptions of being infallible!

The main point is that when water is being cycled continuously, there aren't such severe hot spots and cool spots... all the coolant is closer to the same temperature (not quite the same, but significantly less than if it sat in the rad or engine for a couple of minutes at a time). There is a fixed amount of coolant, so it has a certain amount of heat capacity. so it doesn't particularly matter how fast the coolant goes through the radiator. the radiator still removes a certain amount of heat from the coolant, depending on the coolant temp. Since the coolant cycles through the system quickly enough to maintain similar temperatures, removing heat from ANY of the coolant is basically the same as removing heat from all of it.

If you put 180 degree water inside a radiator and have a fan blowing on it, the air coming off the radiator is going to be a certain temperature (and thus is removing heat at a certain rate) and the amount of heat it's removing will obviously fall as the liquid is cooled. however, if you're constantly pumping 180 degree water through it, the radiator is still going to be removing heat energy at the exact same rate as it would at the point where you had stationary 180 degree water in it.

now it's a fact that heat energy will be removed at a faster rate from coolant by a radiator when the coolant temperature is higher... That's why a cooling system will always reach equilibrium at some temperature, where the radiator removes heat at the same rate it is produced (computer water cooling radiators are rated in Watts per degree celsius typically... so as the temperature goes up, so does the rate at which it can remove heat) this is, of course, as long as the coolant doesn't boil, and the cooling system can withstand the heat/pressure... and obviously car cooling systems are designed to have enough cooling capacity to reach equilibrium before the coolant temp gets too high.

so if the coolant is intermittently cooled and heated, in distinct stages where it sits in the radiator and then sits in the engine... during the first bit of cooling, where the really hot coolant is in the radiator, it will cool at a faster rate. but it will continue cooling until it is much cooler than it would be in a continuous loop system. I won't get into the math crap too much, but here's the basic idea: if you remove heat from a fixed amount of coolant at a fixed rate (number of watts) the temperature will fall linearly. however, with a radiator, the number of watts falls as the temperature difference from ambient falls, so the absolute value of the slope (derivative) of the temperature curve falls over time as well. thus, you end up with an exponential curve.

The first analogy that comes to mind is a tractor pull. In the first 5 seconds you might make it 100 feet, then the next 5 seconds you might make it 50 feet, then the next 5 seconds 20 feet, then none. the longer it sits in the radiator, the worse job the radiator does of removing heat.

in any case, the average wattage doesn't work out to be quite as high. as a thought exercise, by decreasing the time period it sits stationary in the radiator, you decrease the max temp of the water in the engine, and also decrease the time it spends inefficiently cooling at a lower temp, which increases the efficiency. keep decreasing it and eventually you end up with continuous flow, which should be the highest efficiency.

However, turbocad has a point in that we're probably both a little wrong. From what I've read in the mean time, the thermostat doesn't usually fully open or fully close, it usually hangs somewhere in the middle, in another kind of equilibrium... as turbocad said, it's more of a restrictor than an on/off switch, it just varies the restriction based on temperature. However, it does open more to cool the engine more, and close more to heat it more, which points to higher flow rate meaning more cooling. Of course, there's an equilibrium there too, because at some point if the flow rate is too high you're just wasting energy pumping it... but that's something engineered into the car itself, because it should be designed so that if the thermostat is pretty wide open, (engine really hot) it should be at peak cooling efficiency, not wasting power pumping coolant. so yes, removing the thermostat entirely might cause a problem... so perhaps the question should be whether the car would overheat if the thermostat for some reason got stuck fully open.

Okay, as for the actual computer cooling side of things.

Anyone with a water cooled computer can easily test it. Pinch one of the hoses with something (not completely shut, just restricting) and watch the CPU temps. as the flow rate gets slower, the CPU block will become a hot spot, and the radiator will become a cool spot, instead of having everything about the same temp. again, it's an exponential relationship, in that if it's doing a decent job cooling, doubling the flow rate isn't going to double the cooling ability. increasing the flow isn't going to increase CPU temps at any point, but it will approach a "plateau" of sorts, in which increasing the flow any more will not produce a significant enough gain to be worth the effort or money, but if it were pumping extremely slowly, a jump in the flow rate could have very dramatic effects on temps.

and as for the suggestion of pumping AC into the computer directly instead of water cooling:

well, in that case there's two concerns:
1) the radiator and water combination are probably more efficient than the CPU heatsink and fan... since the water cooling is reasonably efficient, and the radiator can be significantly larger than a CPU heatsink.
2) condensation. if you've ever had your AC on full blast on a hot day and had one of the vents aimed toward a window, you probably know about this. hot CPU heatsink + cold air is a recipe for condensation. Therefore, you can isolate it by cooling the radiator instead. (which could be away from the PC, where condensation wouldn't matter)

I don't think you'd need too crazy a pump to handle it. The hard part for a water pump is the amount of head (essentially its ability to pump water against gravity)... since the tubes going to the front would be pretty much horizontal, that wouldn't be quite as much of a problem. You'd be better off using a beefier pump than you would for the same system in a normal desktop setup, but I bet it would work.

I'd be more worried about running the tubes through the engine bay though. even if they aren't too close to the engine, it gets pretty hot in there, and if 6 or so feet (firewall to bumper vent to firewall) of the tubing was exposed to that heat, you'd be losing a lot of efficiency... perhaps if you ran them way off to one side, and put some form of insulation on them...