OC on Fan Stacking

[lolito_fr]

Thx for Excel.
Following up the frictional heating idea, now evidently not the major culprit!



Correct me if I'm wrong, "Adj dP" (column R) is connector dP ? raw or PSI?
Just curious...

[Les]

Originally Posted by Incoherent

Bill
I think there is a measurement error.
It is not necessarily an offset, or at least the offset could be proportional to T.
I note "*RTD calibration in hardware". What kind of RTDs are they? PT100, Ni100, Ni120, CU10 etc? they have different temperature coefficients, even within the same type (i.e. PT100s can have different coefficients depending on the standard adherred to). Could it be that you are using an alpha value for a different type? This would defy calibration of the RTDs against a "known calibration of one", or comparing at zero load, they would read the same at the same temperature, the error coming when they have a difference...
(Edit. Some misleadings statements here. The "known calibration" would work, if it is itself correct. The effect is a compression/dilation otherwise)

Using a PT100 RTD with a NI110 setting for example might give this error within the small delta T we are dealing with.

Sorry if this is way off the mark, clutching at straws really, I just do not like these curves.

Maybe something like this:



Using these RTDs and switching gives :

[Incoherent]

Originally Posted by Les

Maybe something like this:

If I am following you correctly Les, yes, thats essentially what I am driving at.
The curves for the RTD responses, ideal vs actual, meet somewhere but their roc is different. We are looking at small errors here in the context of overall accuracy...

Or something like this.

Bills calibration should take care of this but I am curious about the "RTD Calibration in Hardware" statement. I am not a fan of using the alpha temp coefficient for Resistive sensors, RTDs are nowhere near as bad as NTC thermistors, being actually incredibly linear, but there are residual errors if the hardware is using it is as the calibration method. Way prefer the 3rd order fit (Steinhart-Hart for thermistors) especially over a large range. This is not the error in this case though (If it is in fact an error)
At 35C the Cp should perhaps be 4154J/l ish, but this has a very small effect on the power calc.

[BillA]

"*correction in hardware" is my notation for a goofy calibration scheme
I have a ref Pt392 caled in 10° increments for which I have a curve, so I understand actual;
in a bath I then 'cal' the working sensor at its actual use temp (or midpoint) - a trim resistor for each RTD input; connected to the separately caled inst that will read it

I need to re-cal over a curve for each one
bleh, this is a lot of work

[aaronspink]

Originally Posted by unregistered

med is the 30dB(A) fan we ship, the Delta WFB1212M

Isn't the 1212M a 34db fan? Surely you ment the 1212L.

-> low should be a fan that Swiftech would wish to ship with a 'low noise kit'
I selected the Papst 4412 FGL
???
I am very open to suggestion
Note: the low noise fan should be so at 12V, and even less so at 7V

The 4412 or maybe the nexus 120 seem to be popular and available world wide, so either would see a good choice. The Nexus is a little quieter but may be harder for swiftech to source.

Aaron Spink
speaking for myself inc.

[Les]

God Bill, this is tricky. Glad I didn't open this can.
Yes, am truly befuddled
Anyone fancy checking some sums whilst I am in the pub tomorrow.

(1) Heat Balance Air
Heat In = Heat Out
Wai + Wa + dPaQa = Wao
TaiCaQa +Wa + dPaQa = TaoCaQa
TaoCaQa - TaiCaQa = Wa + dPaQa
Tao= Tai + Wa/CaQa + dPa/Ca

(2)
LMTD=(Twi - Two) - (Tao - Tai)
---- ln ((Twi - Tao)/(Two - Tai))

Then substituting from (1) :
LMTD=(Twi - Two) - (Wa/CaQa + dPa/Ca)
.... ln((Twi - (Tai + Wa/CaQa + dPa/Ca))/(Two - Tai)

(3) R= F (LMTD)/Wa ,
where F is correction factor (obtainable from Wolverine Fig 4.14 (for two pass) - I think).
Have values for all except the air-flow(Qa) and air's pressure drop(dPa).

[BillA]

as
yes, the WFB1212M is 34 dB(A) - our 'kit' fan

[Les]

Think Bill's published data as presented in ThermoChill assessment are/is more than adequate.
Can be used for system calculations taking pump heat at zero flow and adjusting for temperature drop across the radiator(((0.5 *1/'CwQw ((theoretical imprecise but error is negligible(checked with data))).
They/it characterise(s) the radiator.

Edit. Is data a collective noun ?

[BillA]

collective ? no, plural; singular datum

[Les]

Gaggle of geese.
data = gaggle of datums

Feel more comfortable using data as singular

[lolito_fr]

Les, sums look ok.
Would think dPaQa is somewhat negligeable?

LMTD thing is more complicated than I had thought. Am wondering if it is not more useful to HE design, rather than the presentation/exploitation of test data?

[BillA]

am presently thinking so as well
unhelpful complexity, also many other factors ignored (air mass flow conversion, etc.)

have to consider the effect, not difficult with the present data
- I'll take a look at simplification (no one else is doing this anyway, so I should be sloppy too ?)

[Les]

Originally Posted by lolito_fr

Les, sums look ok.
Would think dPaQa is somewhat negligeable?

Thanks for looking.
Very possibly but have not done the sums.

Originally Posted by unregistered

unhelpful complexity, also many other factors ignored (air mass flow conversion, etc.)-

Probably: as stated am happy that present format characterises a radiator.
However to satisfy the purists, Myth Busters, a true R (Wolverrine !/aoUo) should be considered
Maybe Greenman100 can give an authoritative view?.

Originally Posted by unregistered

(no one else is doing this anyway, so I should be sloppy too ?)

Dunno

[BillA]

a bit more candid to describe this testing a empirical data collection rather than scientific analysis

so long as the methods are clearly described, . . . . .

[greenman100]

Originally Posted by Les

Probably: as stated am happy that present format characterises a radiator.
However to satisfy the purists, Myth Busters, a true R (Wolverrine !/aoUo) should be considered
Maybe Greenman100 can give an authoritative view?.

Holy smokes.

This is over my head, I'll get back to you in 2 years after fluid dynamics/thermodynamics.

Perhaps dumb it down for me?

[Les]

Originally Posted by unregistered

a bit more candid to describe this testing a empirical data collection rather than scientific analysis

so long as the methods are clearly described, . . . . .

I am happy with that.
Would, perhaps, have prefer "C/W" to be with reference to coolant inlet.It is no biggy,

Still unsure whether should be a "gaggle of datums" rather than a "data collection"

Edit
ok gaggle of datums = collection of data
you are right Latin limited to Latin Today -1950s edition(Discipili picturam spectata)

[BillA]

well hey, lets redefine it
(there is a big advantage in using the inlet - for those not measuring the outlet temp)

who is using what ?
- I record inlet only when testing kits (could record the outlet if needed); inlet and outlet all else - same for wbs and rads

prefer cluster of datums, alternate is dispersion of datums (goddam buggers)
[the latin plural of -m is -a)

[Les]

Originally Posted by unregistered

well hey, lets redefine it
(there is a big advantage in using the inlet - for those not measuring the outlet temp)

who is using what ?

"Outlet + 2/3 metre of tubing" temperature - tubing is a complication and probably negligible but has be assessed before attempting system calculations

Edit maybe should be a "datum collection" or a "collection of data"

[lolito_fr]

Just reassuring myself:
dPaQa for "Original" Black Ice

105cfm 0.25"H20: 3.09w
70cfm 0.15"H20: 1.23W
40cfm 0.05"H20: 0.24w

Seems reasonable considering typical fan specs

une donnée, des données. simple