Aftercooling Question....

Does anyone know of a way to leave the fans running after the computer is shut-off?I live in near America's wang,and it is always hot and humid,even with A/C. I was thinking of hooking the fans up to an outside source, so I can run even more fans.....I've burned out several so far..... ----Small explosion,smoke slowly rising,mysterious acid(probably cap or battery fluid)------You should really try it....Incredibly fun.....Anyway,please help.

http://www.highspeedpc.com/Merchant...SPC&Product_Code=CoolAfter&Category_Code=Fans

may be a temporary substitution...maybe you can rig it to run the whole time

-peter

There's a product out there for doing this. Basically a capacitor that you hook up a fan or 2 to and it will run for 1-2 mins or so. Wow it's actually called Cooling After. I'd forgotten that. Here's a link to a review.


http://www.directron.com/rd7ca.html

Thanks for that link Ravsitar, that's a pretty sweet item. I have a buttload of large caps(mental image!) on hand, and I've thought about constructing something like that... but... that's a good looking product for the price.

Thx much ^_^

ok...its not like i provided a link and everything first........

good luck

-peter

rpckvv said:

ok...its not like i provided a link and everything first........

good luck

-peter

Click to expand...

Are you going to cry if I don't mention you in my Oscar speech?
Sorry, I didn't notice your link ^_^THANK YOU.

BOO HOO!!!

-peter

I've been thinking about this for a while myself. Good question Will Eatforfood.


.....really nice forum name too!

hidey

How do you think the Cooling After product works anyway?Does it utilize the power supply through like a hidden power connection, or just like store the power?I hooked up a 9v battery(energizer ) to the ylw and blk wires and all fans in the system were on!Running very slow of course, but on-even the PSU's.So if I can hook it up to a battery recharger, which I believe gives small volts, then I can power all fans at full speed.Just disconnect it with a home-made or store-bought "lift-drop-switch" when I power up so there are no power conflicts, or only power the fans I need so they can run at all times.

You could also hook up a second powersupply that runs the fans. That way, once your computer was shut down, your fans would keep running. You could just power down the second powersupply after a few minutes.

i have my cooling rigged to a couple of 12v dc power blocks i have the amp's out matched to what the fans need roughly so i have the cooling system in this rig almost undependent of the psu except for the gfx card and the cpu cooler but i like to know when they stop running while the computer is running. Its really handy on days when my room ambient is pushing 35c and outside its damn near 40c.

I don't see why aftercooling is needed. Your computer will not get hotter after it is turned off.

I'd like an easy way to have my fans run for a few seconds extra (30-60) to cool the water in my rad after I've shutdown.

Giblet Plus - That's not true. The processor temp spikes after you turn off your computer. It's true the processor stops producing heat but they heat already there needs to disipate. When you turn off the pc you turn off the fans so the heat sink must radiate the heat by itself without the effects of the fan. This is just like a car engine. When you shut off the car it stops making heat but it's still hot. Some cars even run the radiator and fan for a few minutes after the car is turned off to prevent the temp spike. Look at the link I posted. There's a graph of temps on it.

Everyone else - Aparently this version of the cooling after uses the WOL (wake on lan) conenction on the motherbaord to power the fans at a very low speed. The WOL connector always has power when the comptuer is plugged in. I know they had a version that rean off a capacitor though. It was larger though. Can't find it now.....

Ravsitar said:

Giblet Plus - That's not true. The processor temp spikes after you turn off your computer. It's true the processor stops producing heat but they heat already there needs to disipate. When you turn off the pc you turn off the fans so the heat sink must radiate the heat by itself without the effects of the fan. This is just like a car engine. When you shut off the car it stops making heat but it's still hot. Some cars even run the radiator and fan for a few minutes after the car is turned off to prevent the temp spike. Look at the link I posted. There's a graph of temps on it.

Click to expand...

This graph?



I don't think a graph ripped straight off the product box is going to be fully truthful.

Explain to me, using physics terms, how the processor gets hotter after it stops producing heat.

giblet, its simple, the processor is producing a ton of heat, which is only cooled by the fan, turn off the fan, temp rises. although its not producing heat anymore, it still has a ton of residual heat from when it was on a few seconds ago. that residual heat is enough to increase the temperature when the fan is turned off.

hope that helps.

although i myself dont think is necessary, the heatsink will do the job just fine.

That's not exactly scientific. Physically, I can't find a reason the temperature would increase, unless they were reading a probe on one of the heatsink's fins.

The CPU generates heat, not the heatsink. The thermal interface between the heatsink and the CPU is not perfect, so heat leaves the CPU into the HS at a finite rate. This means that the CPU is always hotter than the heatsink. And since heat can only pass from the CPU to the HS by the Second Law of Thermodynamics, there is no way for the temperature of the CPU to increase when no more heat is being produced.

Um.. it makes sense to me (that there would be a SLIGHT increase in heat for a SHORT period of time after its turned off, not enought to warrent a need for cooling though).
but as for the original question you could either:
Use a second PSU that is always on to power some of the fans.
Use a power adaper for somthing like a CD player (only more voltage), a 12v DC converter would run it at the same speed, a 4.5v (used in most 2 battery CD players) would run most decent fans and be almost silent.
Use one of these fancy pantsy gadgets.
Use some caps to run it for a pretty short ammount of time after the power is cut to the 12v rails.

I would use the adapter if I needed to do thise for some reason, however I don't seen why I would do this because it being hot wont make a differnce when the comptuer is off, eventually it WILL cool down to ambient wether there are fans in there or not, and how long it takes wont matter as long as, while its off (right after when it might heat up) it doesn't get hotter than like 70C, and it won't unless the fans go off. According to the graph which probably exagurates a bit the tempurature spikes for about 30 seconds before it starts dropping again and it only goes up by about 2C, probabl less than the differance btwn load and idle for most people.

Giblet is right; Mac, temperature is a measure of thermal energy - it is NOT the product of heat. The maximum temperature of the CPU after shutdown is the CPU temperature immediately before shutdown; a temperature spike or rise is physically impossible. Any test claiming otherwise is patently false and has experienced some sort of error that was unaccounted for.

This is true for a few reasons:

• The first law of thermodynamics states that the total energy of a system and it's surroundings are constant. For example, in order for the energy of the system to increase then the energy of the surroundings would have to decrease - the energy has to come from somewhere.
• The CPU is not drawing any current, there is no electrical energy being transformed into thermal energy. There is no source for energy.
• The object with the most energy in this system is the CPU. It's temperature is the warmest of all things surrounding it which means it will not experience any inflow of thermal energy, but there will be an outflow of thermal energy towards equilibrium.

The temperature of the CPU, or amount of heat in the CPU, cannot increase after shut down.

If you disagree, then the best way to prove you are right is to show that the CPU draws current after the fans shutdown. There could be a spike in energy if the fans lost power just before the CPU lost power... Otherwise it is impossible.

There is no constructive benefit of after cooling when it involves only air cooling. There may be a benefit if you don't want warm water sitting in your cooling loop, as in eobards example.

No it's not. Trust me. I'm a mechanical engineer. I've taken 3 thermodynamics classes and 2 heat transfer classes. And I work to design desiel engine generators. The temp rise will happen. Here's a site with actuall data not taken from the product box.

http://www.moddin.net/review.asp?ReviewID=93&PageNo=1

and another

http://www.technoyard.com/hardware/miscellaneous/rd7-ca/page_2.html

If it was impossible for the temp to spike then how did they get the data. It will happen.