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Below Ambient

D

darkone414

n00b
Joined
Mar 12, 2005
Messages
16
Just curious if anyone has succesfully made a setup that operates below ambient temps?
Before you tell me this is not possible please know that it is very possible it would just require a lot of fans and airflow. I know this would work simply based on my own automotive experience. My car sees 80* intake temps in 95+ weather all the time due to the very large intercooler that I use. Now keep in mind that air is being forced through the cooler at 100+ mph but it can be done. It would be very impractical I imagine but I was just curious if anyone has strapped a large enough fan to their radiator to do this....
 
I don't know call me nuts but, how can the ambient air be cooled below it's own temp without assistance from AC?
 
the reason you are getting 80* intake temps is because the fuel is vaporizing in there. As it vaporizes it takes energy from the air and therefore, reducing the temps to below ambient.

It would be lower if you were running alcohol in it, our Racecar's intake feels COLD to the touch in 100* weather (were talkin ice cold) because more alcohol evaporates so much better so much faster.

So, no, with the way our watercooled comp are, tehre is no way to drop it below ambient
 
yep, as was said, you cant get below ambient just by moving a lot of air. No matter how quickly you move the air, the air is never colder than ambient. In fact, you reach a point where the beefier the fan, the more heat the fan puts out, which would actually increase the air temperature.
 
I'm on the side of the original poster here.

My RX7's Intercooler is hot on the inlet side and cold on the outlet side unless i've been sitting for awhile, and this is way before fuel is injected.
 
its possible, i think...im working on my pilots license and one of the things we discussed in ground school was carb icing due to the venturi effect...alot of air moving really fast through a small opening will lose alot of its heat...but im not sure if its possible for his application (the air isnt moving fast enough and the opening is too big...but what do i know) :D
 
I should be more clear on what I was saying as well. My car intercooler is one thing, which probably doesn't reflect how a radiator could perform in my case.
 
Thank you for the support ouija. I am by no means a physics expert but just like ouija said when you feel the hot side its very very warm (not to hot to touch but almost there) as the compressed air coming from the turbo reaches somewhere around 300* but then when you put your hand on the cold side its cool to the touch, well below ambient. And just like he said this is all taking place before the throttle body with no fuel/additives having touched the air yet.

Also any form of water/alcohol/meathanol injection takes place right before the throttle body, once again well after the intercooler.

Thanks for all the responses guys, keep em coming.
 
The only way you could do this is with compressed air. For example, at the end of the work day, when I open the drain cock on my air compressor, the released air feels quite cool, sometimes even freezing the moisture draining from the tank also.

But to do this in a w/c setup seems highly unlikely. You would need an Extremely powerful fan, aka a compressor, connected to a venturi tube connected to the rad.

The setup would also be very loud. Like when you take the valve out of a car tire.

In this type of setup, you would actually be lowering the ambient temp around the rad. Using just air, it really isn't feasible. :rolleyes:
 
Keep in mind that the intercooler is basicly the same thing you are using to cool your CPU in a WC computer, it's just using the rad to extract the heat fron the air the same way your extracting the heat from your CPU, so you're not doing it with just air flow !
 
The post about the air compressor gave me a good reason as to why your intake is cool after the intercooler.... I might not be right though

Think of it this way, before the intercooler, the air your turbo (supercharger, blower whatever, they al basicly do the same thing) is encoutering resistance from the cooler itself which creates a "back pressure" if you will on the forced induction. While it is in the cooler, it still has this pressure, but is cooled down in the process as well. Then, when it is finally through the cooler, it encounters less resistance (since the moter is activly pulling the air) and the pressure drops (maybee only slightly but still). Gas laws say that pressure drop = temp drop, thus explaining why intake is cool before the fuel is introduced.

This would also explain why intake gets warm on ouija's car when he sits for a while, moter is not pulling as much air, less of a pressure drop, less of a temp drop.

#2, by intake I mean the intake manifold. Guess that is where we get crossed. On most cars the intake is considered to be this as well. That would put it right after or at the same point as where the fuel is introduced (be it the carb or injectors).

img0004w8pe.jpg
 
go punx!

yeah, PV = nRT universal gas equation. n is the same on both sides, R is a universal constant, V is close to constant(since it is an open system), T is a variable, P is a variable.

all that boils down to is that if there is a pressure drop, there will be SOME temperature drop, like he said.

another thing to consider that is superchargers and turbos usually use an impeller-type or lobe-type blower, that can actually generate a decent pressure gradient, wheras computer users typically use ducted-propeller-type fans, that can't generate a decent pressure differance for love or money.

it doesn't matter how much air the fan tries to move, it can't set up enough of a pressure gradient to make a differance, past the point where the exaust air approaches the temperature of the intake air.
 
Sorry boys and girls, but unless there is evaporation going on, there's no way to get below ambient. Those of us who took physics call this the Zeroth Law of Thermodynamics: Thermal Equilibirum.

Now that you've brought up your lovely fuel injectors, etc. They work, but they work on gases. Pressure drops on liquids do not cause the liquid to become cooler, they cause it to boil off. Also, conversely, liquids to not compress under common pressures.

If you want to go below ambient with watercooling, you make a chiller, or you make a bong.

All the fans and radiators in the world will only get you to ambient + some very small number.

That said, bongs work very very well in dry places. You have to keep refilling them, but they work very very well. Mine worked to about 4C below ambient where I live. Rockin steam in the winter, too, though I had to stop using it once I noticed the condensation on the lines.
 
mwarps: i took physics as well. mainly quantum and electrical, but i had some thermal in there as well.

why do you deny that a gas-phase pressure drop, with all other conditions being equal will elicit a temperature drop?

i would understand if you dealt with the temperature increase in the gas on the high-pressure side, and used your ambitent reference temperature to be the temp somewhere else in the room, to say that the system is not "really" below ambient. however, from the point of view of the radiator, the air passing through it would be cooler than the air coming into it, the the incoming volume of air was large and at pressure.

anyone want to test all of this experimentally? it probably won't work, but these will get you closer to making it happen than any case fan on earth should be able to: http://www.sidewindercomputers.com/de12tfexhisp.html

they are just disgusting!
 
DFI Daishi said:
mwarps: i took physics as well. mainly quantum and electrical, but i had some thermal in there as well.

why do you deny that a gas-phase pressure drop, with all other conditions being equal will elicit a temperature drop?

i would understand if you dealt with the temperature increase in the gas on the high-pressure side, and used your ambitent reference temperature to be the temp somewhere else in the room, to say that the system is not "really" below ambient. however, from the point of view of the radiator, the air passing through it would be cooler than the air coming into it, the the incoming volume of air was large and at pressure.

anyone want to test all of this experimentally? it probably won't work, but these will get you closer to making it happen than any case fan on earth should be able to: http://www.sidewindercomputers.com/de12tfexhisp.html

they are just disgusting!
Click to expand...

I don't deny it, not for a second. You cannot deny the laws of physics.

Do the rudimentary calculations, man. The pressure drop of that fan is measured mm of H2O. It's utterly irrelevant. If you had a serious pressure change, it would change the temperature noticeably. A few mm H2O isn't going to do much of anything. But remember, when the fan is at max pressure differential, it's not moving any air, so the fan wouldn't be doing anything but causing a pressure differential, there would be no flow, and the system would heat up.

The original poster is talking about real, tangible, sub-ambient temps, not tenths of a degree C. Well, I hope so anyway, otherwise... well... yeah. :p

What I'm trying to say...

Fans, of the classic PC type, even the funky blowers they're getting now for some of the heatsinks - the pressure drop is too low to do anything useful to the termperature of the air. However the formula is supposed to be calculated (and it's a hell of a lot more complex than PV= nRT), there is no doubt. If there is a pressure drop, then there is a temperature drop, but it's never going to translate into meaningful sub-ambient cooling.
 
what did i say about PC fans in the post immediately before you joined the discussion? was it not that a case fan can't set up enough of a pressure gradient to make a difference? given your most recent post, i don't think that we are disagreeing about theory at all, just you saying that it doesn't make enough of a difference to matter in the real world.

i agree with that, i just thought this was a hypothetical discussion from the start.

as for REAL sub-ambient temps............given my experiences with my pelt setup, i'm more and more feeling that to get into the territory that i want to be in, it will have to be using phase-change cooling.

and THAT will have to wait until after i graduate and start working a real job.
 
i dont think its fair to compare pc watercooling to engine cooling there are much greater pressures and such being applied to an engine radiator than a pc radiator
 
DFI Daishi said:
what did i say about PC fans in the post immediately before you joined the discussion? was it not that a case fan can't set up enough of a pressure gradient to make a difference? given your most recent post, i don't think that we are disagreeing about theory at all, just you saying that it doesn't make enough of a difference to matter in the real world.

i agree with that, i just thought this was a hypothetical discussion from the start.

as for REAL sub-ambient temps............given my experiences with my pelt setup, i'm more and more feeling that to get into the territory that i want to be in, it will have to be using phase-change cooling.

and THAT will have to wait until after i graduate and start working a real job.
Click to expand...


Yeah, I tend to read things a bit wrong and then go tangential.

Are you doing a pelt setup now? I've helped with two of them so far, but the people who I was working with are pussies and wouldn't let me solder the pelts, so the thin little wires killed the voltage, so the temps were pathetic.
 
i've been running a pelt setup for probably about 9 months now.

at stock clock, it drops my temps down to around -20 C load temp.

however, that's pretty meaningless.

at my normal OC of 13 x 200 @1.95 my load temps are around + 16 C.

and because people always ask why i have such a low FSB: my DFI NF2 board is hamstrung, and needs 1.9 chipset voltage to even hit 200 with full stability, with good NB an SB cooling.
 
DFI Daishi said:
i've been running a pelt setup for probably about 9 months now.

at stock clock, it drops my temps down to around -20 C load temp.

however, that's pretty meaningless.

at my normal OC of 13 x 200 @1.95 my load temps are around + 16 C.

and because people always ask why i have such a low FSB: my DFI NF2 board is hamstrung, and needs 1.9 chipset voltage to even hit 200 with full stability, with good NB an SB cooling.
Click to expand...

NF7-S, baby. 200MHz at 1.6V :p

You're right, though, for that much extra effort and cost, you might as well just watercool.
 
yes yes............plenty of people get truely wicked OCs out of their lanparty or infinity boards, which is why i got one.

i used to have an NF7-s rev 2, and it hit stock speed at stock voltage, but would not OC very well (~220 FSB).

i got a bad apple from DFI, and am permantely embittered by it.
 
I never considered preasure drop to be a factor but there is at least a 1.5psi drop once the air is inside the intercooler (not after like punx wrote) as it is going from 2.5 inch pipe to a 12x24x3 space and then back into the piping which would explain the temp drop. Also since we are talking about water in the comp and not air I would have to say that a good temp drop below ambient would be next to impossible with the computer. Thanks for all the responses guys.
 
DFI Daishi said:
yes yes............plenty of people get truely wicked OCs out of their lanparty or infinity boards, which is why i got one.

i used to have an NF7-s rev 2, and it hit stock speed at stock voltage, but would not OC very well (~220 FSB).

i got a bad apple from DFI, and am permantely embittered by it.
Click to expand...

Yeah, never trusted DFI, really.

Oh, regarding the poor Pelt Performace, the other thread we seem to be filling out nicely today - you should try a Black Ice Pro II, apparently. The BIX2, as Erasmus has informed us, is crappy. Bring that pelt on over here :D
 
Actually... the insides of intercoolers are not open by any means, they are in fact as crammed as your radiators, so your not going into a space of a size of 12x24x3. Second, its not the space that is causing the pressre drop I was talking about, its the fact that the intercooler causes restriction, and the engine causes a whole lot less (maybe zero becasue it is pulling the air).

Mwarps, I totally agree with you that to cool WATER below ambient there has to be evaporation, or air that is coder than what is considered ambient for the room is being passes through the rad. but good job on the theories, I'e only had very very basic physics and high-school chem to gude me along :D (i'll get ya after I got to college though)
 
when i ramp my two panaflo U1A fans up to full blast, the BIX2 is plenty good.

my coolant temps are hardly warm to the touch at that point, however i think that getting pelts to bring a high-heat system down below zero C load temp would be quite an engineering challenge, for more reasons than keeping coolant temps low.
 
Just curious: Wouldn't the wind chill factor come into play? Or is that only with direct contact with the air?

I know with bong cooling you can get lower than ambient, but that involves evaporation.

I think we've been down this road before, though. We've talked about different liquids other than water, chemical additives, water chillers, more fans, more radiators, blah, blah, blah...

What my Dad did was make a separate case for the radiator and fans. He put that outside during winter and routed the tubing through the wall during the winter. He had some awesome temps. During the summer, he brings it in, and since it's close to the A/C, he gets lower temps, too.

I was planning on trying out a phase change system next. A/C the CPU, but watercool the video card and northbridge. That will be a fun project this summer.
 
wind chill is a factor made for what the air temp feels like due to wind blowing over skin that puts out water and evaporates (sweat)
for something that isn't wet, wind chill (evaporative cooling, which is what a bong is) doesn't come into play.

one way to get sub zero temps:get a mini fridge, take it apart and the evaporator part be a radiator of sorts that cools off the air before it enters the heatsink. not practical because of condensation, but it's another idea to work with
 
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