On Tue, 12 Jul 2005 20:53:10 -0800, floyd@apaflo.com (Floyd
L. Davidson) wrote:

>kony <spam@spam.com> wrote:
>>On Tue, 12 Jul 2005 18:04:49 -0800, floyd@apaflo.com (Floyd
>>L. Davidson) wrote:
>>
>>>You can literally calculate the amount of heat that can be
>>>stored in any given sized reservoir of water, and from that you
>>>can calculate just exactly how long it will take to raise the
>>>temperature of your reservoir to any given point at which you
>>>estimate that the cpu will not get sufficient cooling. (And,
>>>once you get it installed you can measure that very easily.)
>>
>>Not true because even if one tried to prevent it, heat would
>>be shed so long as ambient is less than water temp.
>
>The question is, however, how fast? The answer: not very.


Yes but you kept focusing on the reservoir which is
pointless. The reservoir on any sane PC cooling system is
not big enough to matter relative to the radiator.


>
>>>If there is no air movement across the radiator, the reservoir
>>>is not going to shed any of the heat ...
>>
>>One has nothing to do with the other.
>
>I am considering "the reservoir" to be the entire coolant
>container, including the radiator, pump, and the hoses too.

Err, ok. Seems a bit confusing why you'd do that though,
and futher, since the hoses aren't usually metal, they're
still far less of a heat exchanger than the radiator. Point
being, practically everything but the radiator can be
ignored.


>
>Essentially the only way that heat will be dissipated is by
>moving air across the "radiator"... which might be a separate
>heat exchanger or might be incorporated into the physical
>construction of the reservoir. (The URL the OP posted is in
>fact a combination reservoir/radiator, all in one unit, though
>there may indeed be another heat exchanger too.)

It's not a radiator. It's merely a fancy looking gimmic of
a reservior.



>
>The point is that the water temperature of the reservoir,
>lacking some system to remove heat, is *not* going to dissipate
>the heat it gets from the CPU. It is going to store it.

It's pointless to think about it one way or the other, it
can be completely ignored.



>>No, the reservior has little impact on it unless it's HUGE,
>
>That simply isn't true. As I noted, you can calculate exactly
>how much heat any given sized reservoir can absorb for a
>selected temperature rise.


Yes you can calculate it, and once you've done so-
congratulations, you've completely wasted your time.


>
>The *only* way that a water cooling system will work is if the
>heat removed from the reservoir is equal to the heat removed
>from the CPU.

No. First of all, the reservoir is the reservior, NOT
anything but the storage tank. Second, you're just plain
wrong. The heat is removed primarily in the radiator and
the radiator needs be designed (Selected) towards that goal.
It's just a waste of time to do all this silly theory when
you dont' gain anything by it.



>The CPU of course has to have heat exchanged at a
>fairly fast rate, while the reservoir size determines how fast
>heat has to be removed.

No.
This is all nonsense.
The CPU doesn't need any particularly "fast" nor "slow",
merely at nearly the same rate as it produces the heat,
minus a little as it's impossible to have perfect heat
conduction from the center of the core to the outside though
only a singular path without heading surrounding areas.

The reservour size does not determine how fast heat has to
be removed. Heat has to be removed at a similar rate
regardless of how large it is as a matter of being
reasonable, because it is not large reservoir, not metal
pipe, and even in the actual reservoir (not the nonsense
idea you made up about what a reservoir is) the goal is
storage, it is optimized clearly with that in mind, NOT
maximizing heat transfer. Even so, if it does help a little
so much the better but that is NOT the primary cooling
method and not a primary determining factor.


>
>>and even then, only to the extent that a huge reserviour has
>>high water-surface contact. It's not practical to plan for
>>a huge reservoir, if someone has THAT much free space they'd
>>be better off just adding a 2nd radiator.
>
>Depends on what the point of water cooling is. If it is lower
>temperatures, you are correct (and the reservoir need not have
>any capacity larger than a very small surge tank). But if the
>design target is lower noise, then reservoir capacity is
>significant.

No.
If the design target is lower noise, the same critera still
applies- that the reservoir is not worth considering,
ESPECIALLY in increasing it's size, compared to a larger
radiator.



>
>>>Because of the above, it would seem there is no point in trying
>>>to start off with no fans at all, unless you have some other
>>>arrangement to remove heat from the reservoir. It sounds as if
>>>you are talking about a relatively small reservoir and a system
>>>entirely enclosed in the computer case, which suggests that it
>>>will perhaps take many minutes to heat up, and many hours to
>>>cool off again. Which is probably not an acceptable recycle
>>>time.
>>
>>A system should NEVER be planned based on "recycle time".
>
>Well, that just depends on what the design target is! With
>noise reduction, it *can* be based on recycle time.

QUITE WRONG.
It is a defective system and the seller should face
class-action lawsuits. Water cooling for computer systems
is not a one-shot system, it has to maintain temp
indefinitely at full load or it's simply inadequate.


>
>>>The problem is that you need a way to *know* what is going on!
>>
>>Actually, that's 100% completely wrong.
>>A properly engineered system has no need to inform the user
>>of anything, no need for the user to adjust anything, etc.
>>The only thing the user should ever need to know is that if
>>the system shuts down, it did so before it overheated enough
>>to cause damage.
>
>The "user" as such doesn't need to know anything. But the
>system that controls it *does*. The OP is talking about a
>manual system, in which case *he* is the controller that needs
>to know.

Actually the system doesn't need to know anything either.
You imply some sort of logic- it is completely 100%
unnecessary beyond that already present. Addition of water
cooling does not change the same basic thermal shutdown
scenario present from air-cooling, and no further logic is
necessary.



>
>My whole point was to convince him that since he would need to
>know a lot more, he might as well automate it and hand it all to
>a controller.

.... and you're wrong.
A controller is completely unnecessary additional cost,
time, and additional failure points. Water cooling does not
add any such need, the same system monitoring works for it
as well as air-cooling so long as silly mistakes aren't made
such as trying to do without fans by ignoring parts that
aren't monitored at all. If you argue to monitor
*everything* then I ask what you anticipate the time and
construction plus testing costs to be- since that's a large
enough amount of time and $ that unless it's a mission
critical system, it was once again wasteful.

>
>>>That means temperature probes in cooling system.
>>
>>Ridiculous waste of time.
>
>Only *if* you don't mind the noise of fans operating at maximum
>(required) capacity. That is typical of systems designed for
>overclocking, because the entire idea is to get minimum CPU
>temperature. But, that is *not* what the OP wants. His purpose
>minimum noise.

You have it backwards. The change it CPU temp is larger
than the change in water temp. Monitoring water temp
necessarily causes less accurate feedback for control
purposes. Further, it doesn't matter what the water temp is
and it will vary per ambient temp- we don't care about water
temp, only what the water is cooling.


>
>To have anything other than gross (on/off) control of the fan
>requires temperature probes of the coolant.

Again, wrong. You really have no idea how to set up water
cooling properly in a PC.


>
>>>The probe in
>>>the cpu is fine, but it doesn't tell you what the status of the
>>>reservoir is, and hence won't give you a clue about what the fan
>>>needs to be doing.
>>
>>No, completely wrong. The fan control should be based on
>>the hottest part if it's based on anything.
>
>You are designing a minimum CPU temperature system with a fail
>safe. That nice and is interesting, but is *not* what the OP
>wants.

Nope, I'm detailing how to get it to work properly. Most
thermal sensors don't even have a fine enough granularity to
measure changes in water temp, unless you're considering
something relatively expensive, which once again is a waste
as that same granularity improvement would still be of
further benefit measuring the larger changes in the actual
parts being cooled, which once again- is the whole point of
the water-cooling subsystem.


>
>>Multiple parts
>>with a relay control if it were to be more elaborate, but
>>NEVER based on water temp. Suppose pump breaks, or water
>>leaks, the water temp will not be as high because the
>>components being cooled are retaining more heat.
>
>That has *nothing* to do with fan control.

yes it does. If the pump breaks- the water temp isn't
rising much at all relative to the water-cooled component.
Fans may not kick on but component overheats. Granted that
doesn't cool the water, but what it does do in a good
fault-tolerant system, is help remove as much heat as
possible including some cooling of the water block. That's
only part of the picture though- in past water-cooling
threads I've recommended same thing I still do- that the
northbridge and power regulator area still needs a fan.


>
>And fan control has *nothing* to do with shutting the system
>down due to catastrophic failure. Note that I discussed some of
>the functionality require for that too, farther down in my
>article (and which has been snipped).

What's your point?
Neither should water temp.


>
>I didn't get far into that, but if the OP wants to discuss it
>farther, the various requirements for failure protection are
>interesting too. But the requirements depend on information the
>OP has not provided yet.

Actually, it's very easy but you've gone so far along the
wrong tangent that you'd create an extremely complex,
expensive, failure-prone system that isn't even very
accurate.

It's quite simple- plenty of young kids manage to do it fine
except for the fan control. Fan (as well as any control) is
always best when given high resolution feedback. You can't
get that from water temp measurements and it won't be
applicable to the primary need- the cooled PC component
temps.


>
>>>Basically these devices allow you to have a fully metered
>>>cooling system. It is possible to measure coolant temperature
>>>in the reservoir, after the cpu waterblock, and after the
>>>radiator, and air temperatures in the case and on each side of
>>>the radiator, plus outside and room temperature too if you want!
>>
>>Which is all trivia. In a water cooled system, the only
>>temps that should be weighed in determining fan control are
>>those of the water-cooled components. Doing anything
>>differently than this will only increase the margin of
>>error.
>
>Please realize that this is *not* a typical overclocker's system
>design. He wants to reduce *noise*. Rethink what is allowed to
>vary (the CPU temperature), and what is required to have a low
>"margin of error" (fan noise!).

Please realize that your proposed solution is inferior for
ALL implementations. Inferior for overclocked systems and
inferior for non-overclocked systems.

Fan noise is most reduced when one is monitoring the part
that needs cooled. It is just ridiculous to vary a fan
speed based on a temp of a component of the cooling system
(the water) that has no critical temp that matters. You are
suggesting a system with large margin of error that cannot
safely keep fans as quiet.



>
>>However, if the chassis exahust fan is cooling the radiator,
>
>He wanted to have a minimum number of fans, all running as slow
>as possible.

Actually, I dont' recall any mention of minimum number of
fans but even if true, that doesn't change my statement. In
fact, it just reinforces it as having a minimal number of
fans would mean doubling-up on functionality, having the
exhaust fan also producing the radiator airflow.


>
>>and that fan is also being controlled, then all passively
>>cooled components much also be weighed in the determination
>>of proper fan speed control, but still, NEVER the water
>>temp. Water is absolutely the very last thing anyone should
>>care about until it starts boiling- and if your water is
>>boiling you have far larger problems than which fans are
>>spinning.
>
>That is just not true, given the design targets. (Not to
>mention an absurd scenario, given the typical 70C shutdown
>temperature, and the 50-55C target mentioned by the OP.)

The only way to meet the design target is to have an
accurate reading on the parts that are being cooled. Not
only is it the only relevant temp, but the one with highest
resolution and necessarily the ones that must be used to
determine sufficient cooling, and therefore sufficient
fan/flow rate. Measuring water temp as a basis for control
cannot be optimal and margin of error higher.

Even so, the really crazy part is the elaborate, time
consuming and expensive method suggested to achieve this
inferior pseudo-solution. You've gotten so caught up in a
tangent that you need to step back and look a the details
again. Minimalizing noise without overheating simply
requires monitoring the actual parts, as they are in fact
the determination of whether there is sufficient cooling,
the whole POINT of sufficient cooling.