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[ROG] Positive vs Negative Pressure - Page 4

post #31 of 44
Quote:
Originally Posted by mdatmo View Post

While it is true that adiabatic contraction (expansion) causes air to heat (cool), low pressure doesn't mean low temperature. Temperature is a measure of the mean molecular kinetic energy and can be extremely high in low pressure situations, such as in the thermosphere (where temperatures reach 2000 C but the pressure is extremely low).
The pressure difference inside a case with 'positive pressure' isn't large enough to change the thermodynamics inside the case.

Actually your dead wrong. Pressure is directly related to temperature.

PV=nRT

If you change pressure, you directly change T as otherwise would be impossible. What you mean is, pressure of this scale can't ever change T enough for it to make a difference in a computer case.

[edit] the thermosphere has other variables that allow temperature to reach such high numbers. If you go by the science, pressure is always related to T. This also requires you to have constants of the gas, so it's X amount of gas. A free flowing case doesn't work, as that brings in variables outside of this scenario. So does the thermosphere. You also have to have ATM( standard atmosphere unit ) equal through out, the second you raise or lower ATM you have changed variables in the formula and thus changing the outcome.

[edit] For simplicities sake, since I actually remembered why I have this memorized. How does a pressure cooker work? Does it not increase pressure so that the inner temperature rises. The only difference between it and a pot is the pressure, same heat source and everything. Oh that's right, because pressure IS directly related to heat.
Edited by mushroomboy - 3/19/12 at 11:17pm
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post #32 of 44

Um this is a computer with fans running around which won't be enough to pressure air to create heat and energy anyways... every chassis has so many ventilation holes or grill on the PCI bracket or side to allow fresh air -- positive pressure to push those heat out.

 

I'm not sure why some of you went into theory and rocket science about this... this is not a space NASA computer or something.

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post #33 of 44
Very very nice thumb.gif
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post #34 of 44
Quote:
Originally Posted by mdatmo View Post

While it is true that adiabatic contraction (expansion) causes air to heat (cool), low pressure doesn't mean low temperature. Temperature is a measure of the mean molecular kinetic energy and can be extremely high in low pressure situations, such as in the thermosphere (where temperatures reach 2000 C but the pressure is extremely low).
The pressure difference inside a case with 'positive pressure' isn't large enough to change the thermodynamics inside the case.

No of course, I agree. Fans blowing into a computer case that is anything but airtight will not create that type of energy; I know what you mean, a CO2 tank or NO2 tank on the other hand, would. It's just that the original article made it sound like "pressure" was actually a determining factor in the temperature of the components. I just think it could have been worded better. Perhaps fan "intake" and "outtake" would have been an ideal word choice regarding the article's context.

Like I said in my first comment; I believe a fan arrangement that allows air to flow through the case to be the best. It should consist of intake and outtake fans for ideal cooling. I wasn't quite on-board with the idea that a "positive pressure" arrangement would blow out the dust in the case, that just seems completely inverted from what you think intake fans would do.
post #35 of 44
Quote:
Originally Posted by mushroomboy View Post

Actually your dead wrong. Pressure is directly related to temperature.
PV=nRT
If you change pressure, you directly change T as otherwise would be impossible. What you mean is, pressure of this scale can't ever change T enough for it to make a difference in a computer case.
[edit] the thermosphere has other variables that allow temperature to reach such high numbers. If you go by the science, pressure is always related to T. This also requires you to have constants of the gas, so it's X amount of gas. A free flowing case doesn't work, as that brings in variables outside of this scenario. So does the thermosphere. You also have to have ATM( standard atmosphere unit ) equal through out, the second you raise or lower ATM you have changed variables in the formula and thus changing the outcome.
[edit] For simplicities sake, since I actually remembered why I have this memorized. How does a pressure cooker work? Does it not increase pressure so that the inner temperature rises. The only difference between it and a pot is the pressure, same heat source and everything. Oh that's right, because pressure IS directly related to heat.

To answer your question about pressure cookers: Since the pressure cooker is airtight, the pressure created by the steam can only do so much until it is re-condensed and, yet again, turned back into steam. So what would be 200 normally, would be 250 (or something, wild estimates here) in a pressure cooker. I think that's how my physics teacher in high school explained it...
post #36 of 44
Quote:
Positive pressure is overwhelmingly a benefit, not only for the reasons listed above but also because it pushes dust out of the case
lachen.gif
u know when you put RAM fan Cooler , it won't make your RAM Clean, it would just make it more dusty
it's same with the case, it won't make the case cleaner, adding more intake fan without dust filter just make more dust into the case

if you want to stay away from dust, stay away from using too much fan
more fan = more air = more dust from air
or using dust filter for the intake, no need for the exhaust

at least the article give some good info
1. negative pressure works for blower exhaust type GPU cooler
2. positive pressure good for water cooling
    
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post #37 of 44
You can clearly see from his setup that his "positive" tests are merely testing that intake air blown directly into the intake of the cpu cooler from the top is better than indirect from the front/side. Conversely, the side intake is the best for the GPU temps.

He needs much better controls.

This is still worth knowing, but certainly not good test of positive or negative case pressure.
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post #38 of 44
Quote:
Originally Posted by Blindrage606 View Post

Bill Cosby is not getting the static pressure to move stagnant air pockets within the H50 res, thus making a hotter CPU. That is unless you're blowing the exhaust from ambient case temps to cool a res? Just as bad.
Setup in a push/pull with fresh air moving into case, and through res.
I have an H50 and I have great temps for 5Ghz thumb.gif

No, I'm not. I'm also blowing fresh air through the res, only difference is I have two top 120mm fans directly above mine and they're blowing fresh air directly to it, which is being exhausted by the H50. I've tried many setups, including the rear intake setup you're using, even mounting it to my side panel as an intake (which is a PIA, btw), and this setup provides the best temps for me - especially at load.
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post #39 of 44
Quote:
Originally Posted by Kappy03 View Post

To answer your question about pressure cookers: Since the pressure cooker is airtight, the pressure created by the steam can only do so much until it is re-condensed and, yet again, turned back into steam. So what would be 200 normally, would be 250 (or something, wild estimates here) in a pressure cooker. I think that's how my physics teacher in high school explained it...

No, the steam escapes out the top. The top weight is what determines the pressure. Standard pressure at 14.5psi (not converting, lazy) gives you about 200, 15psi gives you a little over 200, like 220-240. The steam doesn't re-condense, that's just silly talk. If it did that we would have no reason for the weight on top or the holes.

http://wiki.answers.com/Q/How_does_a_pressure_cooker_work

That's the laziest answer I can find. Either way, ask a chem major. Pressure and temp are directly related no matter what you do. PV=nRT

P = (nRT)/V

There, it's made to find pressure. Now you can see that T will effect P every time. In the reverse:

T = (PV)/(nR)

Now you see how Pressure directly changes T. There is no way Pressure and Temperature are not related, it's what basic chemistry would teach you. Physics teaches you the same thing, since it's the exact same formula.

[edit] Pressure always increases the heat potential of any liquid. So boiling temps go up, as well as the temps of the evaporated liquid. ALWAYS

[temp clarification] I'm talking about steam temps, the wiki talks about boiling temps. You get roughly those temps as I'm not exactly sure what the steam temps are. I just know (for certain) they are enough above 200 to kill 99% of bacteria. It's why pressure cooking works so well, it kills off bacteria.
Edited by mushroomboy - 3/20/12 at 11:31am
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post #40 of 44
Quote:
Originally Posted by mushroomboy View Post

No, the steam escapes out the top. The top weight is what determines the pressure. Standard pressure at 14.5psi (not converting, lazy) gives you about 200, 15psi gives you a little over 200, like 220-240. The steam doesn't re-condense, that's just silly talk. If it did that we would have no reason for the weight on top or the holes.
http://wiki.answers.com/Q/How_does_a_pressure_cooker_work
That's the laziest answer I can find. Either way, ask a chem major. Pressure and temp are directly related no matter what you do. PV=nRT
P = (nRT)/V
There, it's made to find pressure. Now you can see that T will effect P every time. In the reverse:
T = (PV)/(nR)
Now you see how Pressure directly changes T. There is no way Pressure and Temperature are not related, it's what basic chemistry would teach you. Physics teaches you the same thing, since it's the exact same formula.
[edit] Pressure always increases the heat potential of any liquid. So boiling temps go up, as well as the temps of the evaporated liquid. ALWAYS
[temp clarification] I'm talking about steam temps, the wiki talks about boiling temps. You get roughly those temps as I'm not exactly sure what the steam temps are. I just know (for certain) they are enough above 200 to kill 99% of bacteria. It's why pressure cooking works so well, it kills off bacteria.

Ah, right. I'm thinking back to how I was camping at high elevation and had to boil the water longer than normal for it to be safe to drink. I know the famous "pervnert' equation but I didn't really pay attention, or care, in chem 101 since it indirectly applies to my major, and I will re-learn it anyway. Microwaves ftw! thumb.gif
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