Radiators and Fans

[bigben2k]

Originally posted by pHaestus
Flowmeter is going to equate to substantial pressure loss. The advantage of using pressure differential as suggested is that provided one has data for the rad one can backcalculate flow rate reasonably well in their cooling loop without adding more resistance. Sure we could throw thousands of dollars at the problem of measuring flow rate directly in our system's loop, but Sean's suggestion would get reasonably close without much money being expended.

Eh, that's what I wrote, non?

Low restriction meters are easy to find, but they're still pricey. One *can* get lucky, as I did. (now all I need are pressure measurements)

[Since87]

Originally posted by bigben2k
Not bad. How 'bout p/n MPX2050GP-ND, MPXM2053D-ND and MPXM2053GS-ND? $15.85, $7.90 and $8.07 respectively.

Haven't looked at those others but in any case, the one I listed may not work for water - appears to be meant for air only.

A sensor that will do the job may be substantially more expensive.

Originally posted by bigben2k

Circuit diagram?

$1000?

[pHaestus]

Take the pressure measurements across that flowmeter: you won't put in in your loop afterwards. We are WAY off on a tangent though sorry.

[bigben2k]

I don't know about that... I just got my flowmeter today, and the 1/2" NPT fittings have an ID of >12 mm.

[pHaestus]

You are ignoring the bell shaped restriction on the inside that allows one to read flow rate? I have similar:

http://www.procooling.com/~phaestus/flowmeter.jpg

HUGE restriction regardless of the fittings used. Also mine is rated +/- 6% accuracy; is just using the pressure across the radiator any worse? Certainly a lot less counterproductive than lowering flowrates considerably to measure them....

[bigben2k]

5% here, but the minimum ID I would guess is 10mm. Otherwise it's wide open: there's an opening even at near 0 flow.

[Blackeagle]

Spooky !

I've been thinking about a 460 which is depicted right under the one you now have Ben. (edit: But it was only a long term thought for when/if I had extra funds for it. And after getting the rest of a new system up and running.)

Considering BillA's & pH's reactions I have to wonder just how restrictive they are.

But if you return to the Blue-White site Ben and go through the ordering steps you'll come to a data page for your flow meter. Shows 2psi as Max. pressure drop. But they don't say at what flow rate this is to happen at.

Hope that is of some interest.

edit: Ben if you get solid data on a restrictions curve chart I hope you could share what it may tell you differant than what little they have to be found at the site.

Thanks

[Since87]

Not looking good.

I crunched the flow data for the three heatercores and I can get good simulations for Blackeagle's and Deeppow's HC using two simple factors.

Mine, however, is way out. (The two blue lines)



Mine 'should' be more restrictive.

I'm inclined to believe that mine has less restrictive flat tubes than the others. I could be missing something in the calculations, but if so, it's something big.

Anyway, I pulled two numbers out of...

I derived two numbers by trial and error.

'Tube resistance/inch' = 0.002
'Overhead' = 0.0008

Blah, blah, blah. It's getting late. If anyone is interested in the math, I'll detail it later and/or pending Bill's permission I'll make my Excel spreadsheet available.

Edit: Just noticed I got the axis labels reversed.

[Roscal]

BillA > One question more : Have you already test a rad in the 2 possible way (assymetry of inlet/outlet) ?? Because pressure drop are less important when water come from the tube and enters a small tank than a big tank and pressure drop are different too for the flow exit..
If you can do that for one rad (since87's rad for example or another with a great assymetry), it could be interesting to see how much difference is and if it's really important (put the 2 possibilities on a same graph)

[BillA]

I do not understand ?

the pressure drop is a consequence of the flow rate
you are suggesting reversing the flow ?
I do not believe such will have ANY effect on the pressure drop (the total is the sum of the increments)

are you trying to breakout the effects of the deltaP ?

Since87 - did you adjust for such with the rad data ?

Roscal - in several days I may have a chance to flow Sean's rad 'backwards

[Roscal]

Ok Thanks BillA for trying , I'm curious to see results.

[Since87]

Originally posted by unregistered

Since87 - did you adjust for such with the rad data ?

I didn't make any attempt to account for variations in tank geometry or inlet/outlet tubing size.

I just lumped all that into the 'overhead' factor mentioned above. For the simulated results, I added the same 'overhead' flow resistance as a single 'component' in series with the tubing flow resistance, for all three heatercores.

I'm interested in seeing the results for the reversed flow test. I'm not really expecting to see much difference, but if there is a clear difference it will be an indication that tank geometry, etc. is a significant factor. That would put a serious kink in our ability to generate models based on a few easily obtainable measurements.

More later.

Edit: Corrected "four heatercores" to three heatercores".

[Les]

Originally posted by Since87
I didn't make any attempt to account for variations in tank geometry or inlet/outlet tubing size.
.............

Done some manipulation for inlet/outlet tube size.
Original P/Q by inpection of gif
Connector correction used "SF Pressure Drop5.0"



Too much like hard work.
Don't think I like this game.

[Since87]

Originally posted by Les

Too much like hard work.
Don't think I like this game.

LOL

Thanks for the info Les. It gives me hope that there is an equation that works for all three heatercores.

I'll work on it some more. I downloaded "SF Pressure Drop 5.0". It looks very handy.

This is going to take a while. Obviously the inlet and outlet sizes need to become inputs to the model. They are much bigger factors than I had guessed.

I'm probably going to need to write some code to search for the right combination of 4 or more 'weighting factors' to minimize the model error for all three heatercores. (The only way I know to do this is very much brute force.)

Yuck.

[bigben2k]

Originally posted by unregistered
deeppow's '86 Chevette rad (# not known)


2-pass, 5/8 OD tubing connections (one cut back from 3/4" end)
effective dimensions: 6 1/8" long, 6 3/8" wide, 1 15/16" thick
14 corrugated tubes, with folded and louvered fins @ 10/in.

Sorry for taking so long...

The heatercore in question is Fedco# 2-261.


I just ordered 2-304: here's hoping it's a double pass! (Also a Chevy core)

[Blackeagle]

I'm curious Ben, Bill's data shows the single pass is lower restriction, which offers some advantages.

I'm wondering what advantage you are seeing in a double pass type?

What special set up do you have in mind for it?

[BillA]

swirling water will draw out more heat

diz-zy, I'm so diz-zy . . . .

[Since87]

Bill,

I was going to start beating my head against this data tonight, and realized I'm lacking some info.

Would you tell me the ID's for all the inlets and outlets?

Or, if they all use the same wall thickness, what is the wall thickness of the inlet/outlet tubing?

Also, is there any significant ID transition between where your pressure sense ports are and the ends of the inlet/outlet tubes?

Anything else I'm missing to be able to be able to calculate a reasonable approximation of the flow resistance attributable to the inlet/outlet tubes?

[BillA]

the Chevette:
0.540 and 0.565

yours:
0.565 - both

Craigs:
0.565 and 0.680

taps:
0.570 - both

I think you're chasing your tail, treat 'em as black boxes

[Since87]

Originally posted by unregistered

I think you're chasing your tail, treat 'em as black boxes

May well be, but I did come up with a better match. (For these three heatercores at least.)

First off, I played around with, "SF Pressure Drop5.0".

The results didn't make sense to me. The software would sometimes calculate negative pressure drops for some features. Quite likely a user problem, but I did come across the following in the FAQ:

"I have calculated a standard orifice acc. DIN 1952 or EN ISO 5167. The program calculates other pressure drops as I. Why?

The DIN 1952 or EN ISO 5167 calculate the pressure drop direct behind the orifice. These values are used to calculate the flow rate. The program SF Pressure Drop calculates the remain pressure drop which you will find 6 D behind the orifice."

Anyway, I modified my treatment of the flat tubes. My previous go at this, just had a factor based on the length of the tubes.

This time I split that up into a per tube factor and a per inch factor. The basis for this, was my dilletante belief, that there should be a pressure drop associated with entering and exiting the flat tube regardless of length, and that there should be a second pressure drop that was dependent on the length of the tubing.

Using these two factors and ignoring the main inlet and outlet altogether gave me the following:



And zoomed in more on the area of interest to most...



The only inputs required to generate these curves is the length of the flat tubes and the number of tubes in each pass.

Reasonably useful general equation for this 'family' of heatercores, or mental masturbation?

I don't know.

[BillA]

I'll not quibble with the rationale,
the fit is close enough for our purposes
(and likely more consistent than the data you're comparing it to !)

I'm putting: together a bunch of data for ThermoChill which should be more than sufficient to extract flow and dissipation parameters for oval tube/folded fin rads

right now I'm in Excel hell with a compressed axis title box (not autosizing)
any Excel gods out there please help

[bigben2k]

Nice work, Since87.

Care to take a guess at my core? 2-304 (not received yet).

[Les]

Originally posted by Since87
......, or mental masturbation?

I don't know.

Neither do I, but some more :-
Simulated using "SF Pressure Drop5.0".
No connectors or pleni(?).
Sean Simulated as 6.5(500x50x0.79mm) Channels
Ralph Simulated as 7(320x50x0.79mm) Channels
Craig Simulated as 13(250x50x0.79mm) Channels
Simulation for tubes only . The 0.79mm Dimension chosen( can't remember ,will edit when do)
All flow is clrssified as Laminar. Transition Laminar/Turbulent ~ 2.7LPM per Channel.


EDIT
Sean
Have only got negative Pressure Drop from "SF Pressure Drop5.0" for enlargement of pipe(so have not used until have thought about ita bit).

[BillA]

Les
the channels are quite corrugated (and your sims proportionally low)
- just add a 'fudge factor' to shift to match
??

and the heat dissipation ?
unfortunatly we have only one datum
just convert to "dissipated W/in²/CFM" (or metric) ?

[Since87]

Originally posted by bigben2k

Care to take a guess at my core? 2-304 (not received yet).

You might want to wait till you have the heatercore in hand. Blackeagle's did not meet the specs shown on the website.

Keep in mind that the numbers my spreadsheet generates may be total BS. I realized I'd made a fundamental mistake in how the 'per tube' fudge factor was applied. I've since redone it with that factor applied 'correctly' and have redone the spreadsheet.

Correcting the 'per tube' fudge factor, required me to add an 'overhead' fudge factor. The overhead fudge factor accounts for inlet/outlet tubing and tanks and is assumed to be the same for all heatercores. (Obviously an oversimpification which begs the question, 'Why does the inlet and outlet tubing size vary between heatercores?")

My updated spreadsheet generates nearly identical curves to the previous one with substantially different equations and fudge factors. Don't believe that because it gets a reasonable match with test data, that it must be 'right'.

That said, I do believe that what I have now is much more plausible. (It bothered me that there was no 'overhead factor' in my last pass at it.)

I'll create a cleaned up, user friendly version of the spreadsheet tonight, and make it available for download here. Anyone with Excel can play around with it, and possibly refine it.