aiiii
I think the words on this page are cavitating
sorry but I've not time to catch up

"Lowered flowrate results in a COOLER coldplate", are we getting closer ?

Les, help me here
give me a (frothy ?) verbal description of that second graph
(the first I would hazard represents 'reaL world' efficiency, as my uninsulated system was setup)

Please explain "the way you see it". I look forward to changing the "way I see things" if I am reasonably proven wrong in my thinking.

1)They are wb only C/W s .
The predicted C/Ws are a composite of the calculations posted here:
http://forums.procooling.com/vbb/sho...?threadid=6347 .
The joined "calculated data points" are at the same flow rate.
In that the Temp dependance of the Flomeric and Kryotherm "h" appear to be similar no differentiation is made betweeen wb type..

Your C/Ws simply calculated from "coolant temp", "die temp" and Watts..
Dunno whether your flow rate is constant but would conveniently explain the large discrepancy if was decreasing with coolant Temp.

2) Something like that.

ah so
#2 then is VERY enlightening
pHaestus ?

BTW, a 25% soln of antifreeze was used

Althornin, I know you understand the following, but I just wanted to expand upon the point you raised, I am not contradicting you.

Yes, this is true, but this is a bad thing given everything else being fixed except for flowrate.

The non-intuitive flip here is that just because the cold-plate/water-block is cooler, this does not necessarily mean that the water will be colder. If the amount of heat being moved is the same, then what happens is just a large temperature differential between the cold-plate and the water.

If we keep the cold-plate warmer, the TEC's efficiency picks up, and more heat gets moved from the cold to the hot side. Also, and VERY importantly, for a high flow rate the differential between the water and the cold side is MUCH less than with a low flow rate. Yes, the cold plate is warmer than with a low flow rate, but the water is also THAT much closer to the cold-plate temperature.

Rather than mince words like the above description, this is why I tried to keep referring to the wattage moved. Don't think of things as temperatures, think of things as watts moved and then it makes sense when you keep in mind that you can't create/destroy energy.

It is true that improving the hot-side efficiency tends to have a greater effect though, but the cold-side efficiency is still important.

If you don't believe me, go to Kryotherm and type in some values for the cold-side C/W. The lower the C/W (more efficienct representing a higher flow rate), then the lower the equilibrium cold-chamber temperature, but the higher the cold-plate temperature.

I'm trying to follow the example you state here,
This is the DeltaT of coldplate and chiller water? Higher DeltaT is what you are saying in this case for the lower C/W. This is coinciding with higher in chiller flow rate?

Bear with me, not trying to contradict this just making sure I understand your example.

Interesting (to me) observation:

Extrapolating Bill's data - the MCW5002 has a lower C/W than White Water with flowrates a bit lower than 1 lpm.

I predict a thermal resistance of ~.255 C/W at 0.1 lpm for an MCW5002 and ~.285 C/W for a White Water at 0.1 lpm. (Inasmuch as these numbers have any relevance, it is WRT Bill's die simulator.)

I don't really want to go into a detailed explanation of how I came up with these numbers. In brief, I used my 'hydropower' spreadsheet to make fairly straight lines on a log graph out of the C/W vs 'hydropower' curves, and then extrapolated those lines to the 0.1 lpm point.

Warning: Mathematical nightmare approaching.

Some points for consideration:

A 226 Watt TEC is actually a two dimensional array of many smaller 'tecs'. Each of these small 'tecs' can be operating at a different point of the dT vs Q tradeoff. Thinking of a 226 Watt TEC as a single monolithic block works reasonably well when 'high' flowrates are used, because of the small dT between inlet and outlet coolant. As the flowrate is lowered, it becomes increasingly important to consider the operating dT and Q of the smaller 'tecs' within the TEC.

Edit: I'm just beginning to think about a grossly simplified model that attempts to consider the points above, and my head already hurts. There's a lot to be said for finding things out experimentally.

I believe there are 127 in the array.
http://www.arrakis.es/~cidete/iti.htm

lol, the livin' proof here

your extrapolations seem correct, the slope of the MCW5002's C/W curve is less at its low end,
though at 0.3gpm the WW is 0.002°C/W lower, rather difficult for anyone to measure

which is the specific advantage - for all TEC apps - of a wb with opposite corner connections

Something like this:-
http://www.jr001b4751.pwp.blueyonder.co.uk/Chiller3.jpg

Cannot vouch for accuracy of data points(inpection of gifs).

EDIT: Revised/updated graph to include experimental data points. Thanks Bill

Yep, except a bit more convoluted on my part due to using an existing spreadsheet as a shortcut.

Same here.

Ah pimpage. LOL

Actually if there is a benefit to the dT/Q gradient that develops at low flowrates, the benefit likely becomes substantially greater if the the chilled water flows past the two TEC's in series. Taken to it's logical conclusion 'diagonality' becomes irrelevant.

(I'm still not certain that there is an explanation for your experimental results in the dT/Q gradient alone. I have no other hypotheses though.)

Somewhat coincidentally, several at O/C forums seem to get 'good' results from chillers containing ten '50 Watt' TEC's. I haven't paid enough attention to know anything about the construction of those chillers though.

I suspect there should also be some benefit to running the hotside water counterflow to the chilled water. Have you tested this Bill?

shakin' ma booty, pimpage rules

"two TEC's in series", na - one chamber with a TEC on either side
no, diagonally is relevant - consider the areas of stagnation

I have a liquid/liquid xchr which is counter flow, only way to get good results
but here there is a TEC plus 2 rather hefty bps between the 2 flows, no significance I suspect

we have some 360W TECs, perhaps all 6 sides ?
lets see, 6x24A = 144A @ 24V = 3456 Watts
would that get it done ?

will send you and Les the datapoints

You've seen examples of my flow visualization abilities. Why would you think that if I "consider the areas of stagnation" I will get better results? Got pictures? drawings?

I presume there is some small amount of stagnation in the 'non-barbed' corners. On the other hand, an open chamber type with barbs centered in two opposite sides, will have worse stagnation in all four corners. Reasonably accurate?

exactamundo
and center inlet, corner exit is worse yet