power supply overheating?

[Timothy Daniels]

Now lets put example numbers to your speculations from
chemistry. If the CPU temperature increases, then the CPU
might only last 100 years instead of 200 years. That 5
degrees is totally irrelevant except when other unresolved
hardware problems make it relevant. Again, I cite the Dorothy
post as example. Use numbers such as from datasheets before
making conclusions. Otherwise we get this junk science
conclusion about chemical reactions inside semiconductors.

Again, a straw man argument. Who said anything about
semiconductor "wear"? I said "hard drive", which includes
platter bearings and armature bearings. Mechanical wear
is very much influenced by temperature, and I would
consider a 5 degree F. drop in temperature worthwhile.
If you prefer your hard drives hotter than that, go for it!

*TimDaniels*

 

[Timothy Daniels]

Tim - 50% obstruction was provided as an example and not as
what is happening in every case. Clearly all you want to do
is argue. Cut the bullshit with 'waffling' and 'strawmen'.
When you are ready to discuss technical, then it will be
obvious that you first read a manufacturers datasheet. You
are posting numbers using junk science concepts - such as
irrelevant chemical reactions inside a semiconductor.

Straw man. I made no such reference to chemical reactions
inside a semiconductor. You're arguing with your own b.s.

Currently your posts, devoid of numbers, are classic of
junk science reasoning combined with selective reading.
Please feel free to cite manufacturers data sheets and numbers
before replying. Use technical facts rather then a lawyer's
subjective terms such as 'waffling' and 'strawmen'.
Demonstrate a technical grasp before replying. Don't
continue posting using 'junk science' reasoning.

You have claimed in this very thread that putting two fans
in series will not increase air flow. Cite your vaunted
"manufacturer's data sheets and numbers" to prove that.
Let's see where the junk science really is.

*TimDaniels*

 

[w_tom]

Chemical reactions inside disk drives have doubled because
the temperature has risen how many degrees? Yes, higher
temperature can increase mechanical wear. And that disk drive
is rated for something on the order of 50,000 hours even when
run at 100 degrees F. Again numbers. 50,000 hours at eight
hours everyday is something like 17 years. Clearly a disk
drive that fails after 17 years is a disaster? Tim- are you
still worried about all those chemical reactions inside a disk
drive now that we apply numbers to your speculations?

The only strawman I see here is the one who wishes he had a
brain. At least be a tin man. Have enough heart to admit you
don't have sufficient technical knowledge. Admit that massive
chemical reactions have not doubled inside a warmer disk
drive. Posted earlier was criticisms about those who post
without even providing numbers. Your posts provide no numbers.
Only demonstrates proof using junk science - sweeping
conclusions without a single numerical fact. Numbers, Tim.
They have a very important purpose in technical discussions.
Numbers are what characterize Dorothy's post separate from
'computer literates' who know and therefore don't need no
stinkin' numbers.

In the meantime, please provide the empirical equations for
those massive chemical reactions inside a disk drive due to 5
degrees more heat. If chemical reactions are damaging disk
drives, then we all must be informed of that chemistry.

 

[kony]

Again, a straw man argument. Who said anything about
semiconductor "wear"? I said "hard drive", which includes
platter bearings and armature bearings. Mechanical wear
is very much influenced by temperature, and I would
consider a 5 degree F. drop in temperature worthwhile.
If you prefer your hard drives hotter than that, go for it!

*TimDaniels*

While it's certainly true that a hard drive's (maximal) lifespan is
related to temp, unfortunately it seems none of the manufacturers provide
temp vs lifespan projections. Further we're getting into a grey area,
where one persons's idea of acceptible lifespan may not be the same as
another person's, and futher the willingness to go to extra measures to
extend lifespan may also vary.

On the other hand, fan and capacitor manufacturers are sometimes more
forthright about this relationship, that a typical lifespan reduction of
50% can be expected with 10C rise in temp. This will not affect some
people, but often plays a role in failure of video card fans, power supply
sleeve bearing exhaust fans, and video or motherboard power regulation
circuit capacitors (varying per design, space and budget), in addition to
system power supply capacitors.

The issue is not so much whether the temp is dropped by 5C, but what the
maximal temp is that will provide adequate service life... a difficult
thing to determine except in retrospect, comparing aged parts to next-gen
parts, particulary with parts having unlabled or generic components,
unobtainable specs. Of course if the temp is above this acceptible
service life margin, 5C drop is much more significant than if temp is
below that.

As for hard drives, we need specs for manufacturer to make individual
determination of realistic (not MTBF ratings) lifespan projections per
temp before this information can be used to plan a system's service life,
or at least that of the drive itself to implement a rotation schedule,
replacing drives as an informed choice.

 

[Timothy Daniels]

Chemical reactions inside disk drives have doubled because
the temperature has risen how many degrees?...
Admit that massive chemical reactions have not doubled
inside a warmer disk drive.

You are so very dependent on jousting with straw men,
aren't you. No one spoke of "chemical reactions" inside
disk drives. No one spoke of "massive chemical reactions",
either. But that the increased kinetic energy of the atoms
and molecules of a medium increase both chemical reactions
and wear rates *is* true, and the mechanisms are much
the same when you consider that much of mechanical
wear occurs at a molecular level.

As for the significance of a 5 degree F. decrease in temperature,
if it makes a difference to your body, why wouldn't make a
difference to a disk drive? When considered on a Kelvin scale,
the operating temperatures of both are similar. Just how much
of a temperature decrease do you need to feel that it is
"significant"?

*TimDaniels*

 

[David Maynard]

"w_tom" blurted out loud:




Numerous people have posted that airflow increased
when they removed or cut away the grill or the perforated
blade guard that covered their fans. Doing so obviously
reduced the resistance to airflow and thus the back pressur,
allowing more air to flow. Adding a fan in series *also*
reduces the back pressure and results in an increase of
air flow. The effect is very analogous to reducing a
resistance in an electrical circuit while keeping the voltage
across the resistance the same - the current increases as a
result, just as airflow increases with the fan. And electrically,
one can do what two fans in series do by applying twice the
voltage across the resistance - which doubles the current.
If fans were ideal fixed pressure differential devices, putting
two in series would do the same thing - it would double the
air flow.

Nice analogy, except that fans don't work like that and an easy way to
visualize it is to imagine a very high CFM fan going into a low CFM fan.
The second fan itself becomes a resistance, and not a 'boost', to the high
CFM fan because, for one, it's blades simply can't spin that fast. And even
if they 'free wheel' they'd obviously not be adding anything to the effort.
Indeed, they'd be bleeding off CFM by absorbing the energy needed to blow
the blades faster.

You may protest that that isn't two equal fans but the point is they do not
'add' like your electrical analogy.

Obviously not. And no one claimed that two fan in series
*would* double the airflow over that of one fan. And
that is because a fan is a combination of a fixed CFM device
and a fixed pressure differential device. In other words,
it's a real world device, not an ideal device, and two fans
in series aid each other whether they are in series or in
parallel, but not to the extent of doubling airflow. What
they *do* do in increasing air velocity is to reduce the angle
of incidence of the air as it meets the leading edge of the
fan blades, reduce the turbulence produced by the blades
as they pass through the air, thus reducing the noise. Would
the amount of noise be cut in half? Of course not. But I
would expect a reduction of maybe a couple dB.

*TimDaniels*

Fans are rated CFM into free air and CFM per back pressure.

Under ideal conditions, identical fans, and ignoring side effects:

Put two fans in series and you raise the slope of the back pressure curve
(I.E. 0 CFM occurs at a higher pressure) but you do not increase the
'rated' CFM into free air.

Put two fans in parallel and the 0 intercept of the back pressure curve
remains the same (I.E. 0 CFM will be at the same pressure as for 1 fan) but
you double the 'rated' CFM into free air.


When people say that putting fans in series doesn't 'increase' the airflow
they are speaking of the 'rating': What you 'could' get under ideal
conditions (it's where you start with any spec). It can result in increased
airflow if you're working into a high resistance because the ability to
push/pull into/against the resistance has increased (assuming it isn't
screwed up by turbulence, blade beat, and other problems), but that
characteristic is the same as for 1 fan: I.E. you get less than the
'rating' depending on the resistance to the airflow. You simply have a 1x
CFM fan that can handle more pressure.

To put it another way, the airflow resistance is an external influence and
not a characteristic of the fan configuration, be it single or dual. You
spec what the configuration can do (e.g. I get twice the pressure
capability with series fans) and then calculate into the environment.

If you insist on an 'airflow' description, the way to characterize it is
that you "lose less airflow" with series fans, not that you get 'more',
because the free air rating of 1 fan is all you 'can get'.

A better way is to say you double the pressure capability with series fans
and double the airflow with parallel fans because that is the actual
characteristic of the configuration. You can then see what effect the
environment they're placed into has on them.

 

[David Maynard]

You're waffling. And you're setting up a straw man, again.

First, the grills and perforated screens covering fans do not
cover 50% of the cross-sectional area and they are not
"installed wrong" as every manufacturer does that. So arguing
against a 50% obstruction - which no one has mentioned - is
a straw man.

Second, you've said that CFM remains constant regardless of
decrease or increase of resistance to air flow. Now you're
backing off and waffling. Just what IS your position?






And just where did I equivacate a fan to a voltage source
or to its analogue, a constant pressure differential device?
You're arguing against a straw man, again, as I made no
such claim. In fact, I pointed out that a fan is a combination
of a constant flow device and a constant pressure device,
IOW not an ideal example of either but rather, a real world
device.






Waffling, again. Define "excessively".

In truth, two fans in series will increase air flow, but
not double it,

two fans in parallel will increase air flow,
but not double it.

Of course two in parallel will double it. Why would you think not?

 

[kony]

Of course two in parallel will double it. Why would you think not?

In _free_air_ two parallel fans will have double flow rate, but not if
there is a pressure gradient.

 

[Timothy Daniels]

Nice analogy, except that fans don't work like that and an easy way to
visualize it is to imagine a very high CFM fan going into a low CFM fan.
The second fan itself becomes a resistance, and not a 'boost', to the high
CFM fan because, for one, it's blades simply can't spin that fast.

That's where fans are non-ideal. Over a span of loads, the fans
speed up when the load (back pressure) is decreased. Beyond
those loads, the fans act differently. You are merely observing that
fans are not ideal pressure differential devices. And, of course,
that is what I have been saying - that fans are a real world combin-
ation of constant pressure differential devices and positive displace-
ment (constant flow) devices.

You may protest that that isn't two equal fans but the point is they
do not 'add' like your electrical analogy.

And why not? If the larger fan is turning at the low end of its speed
range so that its flow rate doesn't put the smaller fan outside its normal
speed range, their efforts will indeed be additive - not perfectly
additive - but additive. What you are proposing is a situation in which
only one of the real world devices can approximate a constant pressure
differential device and not both. And what does *that* prove? It only
proves that there are no ideal devices in the real world. Even electrical
devices don't act as ideal devices.

Fans are rated CFM into free air and CFM per back pressure.

Under ideal conditions, identical fans, and ignoring side effects:

Exactly. Fans are given a rating for a given set of conditions.
Their ratings are not isolated parameters of the fans without
reference to their environments, i.e. they are real world devices.
And it also means that they can also interact - one can, in fact,
act as a flow inhibitor for the other for certain ranges of
fan rpms, just as in your example.

And getting back to the original question about whether two
case fans in series can move more than one case fan (with
the implicit condition that the fans are of comparable size),
the answer is still "Yes".

*TimDaniels*

 

[David Maynard]

In _free_air_ two parallel fans will have double flow rate, but not if
there is a pressure gradient.

Two fans in parallel will put out twice what a single fan would into the
same gradient.

 

[kony]

Two fans in parallel will put out twice what a single fan would into the
same gradient.

.... but with two fans, it wouldn't be the same gradient, unless there are
other changes beyond simply the addition of second fan.

 

[David Maynard]

That's where fans are non-ideal.

Fans are not ideal under ANY conditions, not just 'there'.

Over a span of loads, the fans
speed up when the load (back pressure) is decreased. Beyond
those loads, the fans act differently. You are merely observing that
fans are not ideal pressure differential devices. And, of course,
that is what I have been saying - that fans are a real world combin-
ation of constant pressure differential devices and positive displace-
ment (constant flow) devices.

No, what I'm saying is that your analogy does not represent how fans work.

And why not?

Because they DON'T is why. Nor are they going to suddenly 'change' and work
that way simply because you find the analogy satisfying.

If the larger fan is turning at the low end of its speed
range so that its flow rate doesn't put the smaller fan outside its normal
speed range, their efforts will indeed be additive - not perfectly
additive - but additive.

The term "additive" means something; like 1+1=2. There is no term "not
perfectly additive" but if there were it would mean "not additive but some
other kind of relationship." And I explained to you what the other
relationship is: the pressure capability when placed in series.

What you are proposing is a situation in which
only one of the real world devices can approximate a constant pressure
differential device and not both.

I'm saying no such thing. I'm saying your analogy, and insistence on
calling them constant pressure differential devices, is inappropriate and
leads to incorrect 'guesses'.

And what does *that* prove? It only
proves that there are no ideal devices in the real world. Even electrical
devices don't act as ideal devices.

I gave you an extreme case, because it's easy to visualize, to illustrate
that the fans are not additive in the manner you claim.

Exactly. Fans are given a rating for a given set of conditions.

EVERY rating for ANY thing is for a given set of conditions.

Fans are rated at free air because that is the condition which represents
the fan's ability sans 'other things', which are unknown until the fan is
placed somewhere.

Their ratings are not isolated parameters of the fans without
reference to their environments, i.e. they are real world devices.

No kidding? It isn't a rating in an alternate universe? Whod'a thunk it?

And it also means that they can also interact - one can, in fact,
act as a flow inhibitor for the other for certain ranges of
fan rpms, just as in your example.

So? All this hand waving you're doing about generalities doesn't accomplish
anything.

And getting back to the original question about whether two
case fans in series can move more than one case fan (with
the implicit condition that the fans are of comparable size),
the answer is still "Yes".

I couldn't care less what, you say, "the original question" was, or who you
think you're having a proxy argument with. All I did was tell you how fans
work when placed in series and parallel configurations.

Here

http://www.comairrotron.com/engineering_notes_02.asp

 

[David Maynard]

... but with two fans, it wouldn't be the same gradient, unless there are
other changes beyond simply the addition of second fan.

And what would it be? Don't know. That's why these things are calculated
with the assumption of "all else being equal" and then when things aren't
equal you put in the numbers for that criteria. Put another way, when
building characteristic equations one likes to change only one variable for
'that' characteristic. If you link them then, invariably (pun), the next
application has one of them different.

However, you should have stuck to your original contention because it was
correct and it was I who misread it.

The doubling of flow for a parallel combination, and pressure handling for
series combination, is only accurate at the end points of max pressure and
max airflow because the fan's airflow/backpressure curve is not linear, and
neither is it when the two are combined.

http://www.comairrotron.com/engineering_notes_02.asp

 

[Timothy Daniels]

"David Maynard" blurted:

I couldn't care less what, you say, "the original question" was,
or who you think you're having a proxy argument with. All I
did was tell you how fans work when placed in series and
parallel configurations.

Here

http://www.comairrotron.com/engineering_notes_02.asp

Thanks. It proves my point that two fans in series flow
more air than a single fan. Here are three paragraphs from
the above web page, titled:

"Series and Parallel Operation"

"Combining fans in series of [sic] parallel can achieve
the desired airflow without greatly increasing the
system package size or fan diameter. Parallel operation
is defined as having two or more fans blowing together
side by side. The performance of two fans in parallel
will result in doubling the volume flow, but only at
free delivery. As figure 4 shows, when a system curve
is overlaid on the parallel performance curves, the
higher the system resistance, the less increase in flow
results with parallel fan operation. Thus, this type of
application should only be used when the fans can operate
in a low impedance near free delivery."

"Series operation can be defined as using multiple fans
in a push-pull arrangement. By staging two fans in series,
the static pressure capability at a give airflow can be
increased, but again, not to double at every flow point,
as Figure 5 displays. In series operation, the best results
are achieved in systems with high impedance."

"In both series and parallel operation, particularly with
multiple fans (5, 6, 7, etc.) certain areas of the combined
performance curve will be unstable and should be avoided.
This instability is unpredictable and is a function of the
fan and motor construction and the operating point. For
multiple fan installations, Comair Rotron strongly recommends
laboratory testing of the system."


As the article points out, choice of the fan size and flow rate is
important to minimize power usage and noise production. It
points out that for high impedance (i.e. air resistance) cases,
the impedance rises at approximately the square of the flow rate
increase, in line with turbulent flow principles of aerodynamics.
This would lead one to seek ways to reduce the impedance before
resorting to a larger fan or fans in parallel. And, of course, one
way to reduce air impedance is to use "round" IDE cables instead
of flat cables in situations using many ATA/ATAPI drives, and to
remove perforated fan grills. Interestingly, in cases having high
impedance, the article says that fans in series are more effective
than fans in parallel.

*TimDaniels*

 

[David Maynard]

"David Maynard" blurted:




Thanks. It proves my point that two fans in series flow
more air than a single fan.

It is no 'point' to ME nor do I care what your apparent proxy argument with
someone else is.

Here are three paragraphs from
the above web page, titled:

"Series and Parallel Operation"

"Combining fans in series of [sic] parallel can achieve
the desired airflow without greatly increasing the
system package size or fan diameter. Parallel operation
is defined as having two or more fans blowing together
side by side. The performance of two fans in parallel
will result in doubling the volume flow, but only at
free delivery. As figure 4 shows, when a system curve
is overlaid on the parallel performance curves, the
higher the system resistance, the less increase in flow
results with parallel fan operation. Thus, this type of
application should only be used when the fans can operate
in a low impedance near free delivery."

"Series operation can be defined as using multiple fans
in a push-pull arrangement. By staging two fans in series,
the static pressure capability at a give airflow can be
increased, but again, not to double at every flow point,
as Figure 5 displays. In series operation, the best results
are achieved in systems with high impedance."

"In both series and parallel operation, particularly with
multiple fans (5, 6, 7, etc.) certain areas of the combined
performance curve will be unstable and should be avoided.
This instability is unpredictable and is a function of the
fan and motor construction and the operating point. For
multiple fan installations, Comair Rotron strongly recommends
laboratory testing of the system."

I already read it, and the equations. I'm the one who posted the link.

As the article points out, choice of the fan size and flow rate is
important to minimize power usage and noise production. It
points out that for high impedance (i.e. air resistance) cases,
the impedance rises at approximately the square of the flow rate
increase, in line with turbulent flow principles of aerodynamics.
This would lead one to seek ways to reduce the impedance before
resorting to a larger fan or fans in parallel. And, of course, one
way to reduce air impedance is to use "round" IDE cables instead
of flat cables

Better yet, simply run the flat cables flat along the walls like they're
intended.

in situations using many ATA/ATAPI drives, and to
remove perforated fan grills. Interestingly, in cases having high
impedance, the article says that fans in series are more effective
than fans in parallel.

Well, I tell you what. Why don't you post your fan specs and the air
impedance of your case and we'll crunch the numbers?

 

[Timothy Daniels]

"David Maynard" snarled:

It is no 'point' to ME nor do I care what your apparent proxy argument with
someone else is.

[..........]
I already read it, and the equations. I'm the one who posted the link.


Well, I tell you what. Why don't you post your fan specs and the air
impedance of your case and we'll crunch the numbers?

Dear David: I have no quarrel with you or your link, and I
don't care what you think or don't think. My purpose in
posting is to get at truth because many more people read
this newsgroup than you and I. And again, thank you for
the link.

*TimDaniels*

 

[David Maynard]

"David Maynard" snarled:

It is no 'point' to ME nor do I care what your apparent proxy argument with
someone else is.

[..........]
I already read it, and the equations. I'm the one who posted the link.


Well, I tell you what. Why don't you post your fan specs and the air
impedance of your case and we'll crunch the numbers?

Dear David: I have no quarrel with you or your link, and I
don't care what you think or don't think.

Good. And thank you for having finally stopped trying to argue with me
about what you think someone else's 'point' was.

My purpose in
posting is to get at truth because many more people read
this newsgroup than you and I. And again, thank you for
the link.

You're welcome.