I believe this is what you are looking for:
http://www.cubigel.com/java/X?cgi=cu...ccion=datos_ss
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I believe this is what you are looking for:
http://www.cubigel.com/java/X?cgi=cu...ccion=datos_ss
http://www.blairwing.com/images/Autocascade14.jpg
Changed pic... work in progress..condenser change is Gary's Idea
Maybe I'm missing something, but I just don't see the point in increasing the amount of R290 subcooled liquid, which is what the bottom of that condenser is doing.
I envy your drawing. How about drawing my parallel flow condenser/separator in there? Put a header at each end of that condenser, bring the discharge line into the center of the right header. The left header would have a line coming out the top straight over to the interstage, and the cap tube at bottom, much as it is now.
Give me a good description and I will draw it... pm me with it...
Lowering the head pressure. I have seen a drop of 10 to 15 degrees on the phase change systems I have subcooled in this manner..
I haven't built an auto cascade yet still figuring out what may work before I start...... just playin with ideas..
You would get more subcooling by exchanging that liquid line heat with the suction line, instead of air cooling it in the bottom of the condenser.
Chopped 12" off the R290 cap tube and set the heat load to 68 Watts. Left the system for 20mins to stabilise, these are the results.
R23
Evap Exit: -51.6ºC
SST: -66ºC (1.3barg)
SCT: -10ºC (18barg)
R290
Evap Exit: 13.7ºC
SST: -21ºC (1.3barg)
SCT: 55ºC (18barg)
Air in: 20.2ºC
Air out: 24.4ºC
CPU: -18ºC
Better about what I expected to happen. Do you happen to have an EPR (evaporator Pressure Regulator) I think that without something to differientiate the two suction circuits we won't get a good balance. With an EPR set at 1.8 on The r23 evap and a little shorter cap on the r 23 cap tube you will have it. With the valve in the circuit and a guage on the evap you can dial it in.. You are deffinatly headed in the right direction can't get -68 on propane.
Without changing the charge, take it up to full load and see what it does.
Kinda crude, but...
http://www.gatecom.com/~tmethod/cond-sep.jpg
That's R23/R290 from the discharge going into the right side, R23 exiting top left (to the interstage), and R290 exiting bottom left (to the cap tube for the interstage).
R23
Evap Exit: -42.5ºC
SST: -65ºC (1.5 barg)
SCT: -9ºC (18.5 barg)
R290
Evap Exit: 15.2ºC
SST: -19ºC (1.5 barg)
SCT: 56ºC (18.6 barg)
Air in: 21.7ºC
Air out: 25.6ºC
CPU: -2ºC
Oh yeah, thats after upping the load (1.65v@1866MHz to 1.9v@2700MHz). I could try and put the cpu on 100% load but im not sure if it will be stable enough.
You will probably need to add a little R23 to get best CPU temp at full load.
Thats just what I was wanting to do, but didnt want to change anything before you replied. I rekon around 20-21bar will get me the low temps, well thats what I have seen before. Do you need me to do anything else with this charge or can I go ahead and boost the R23?
Go ahead and charge the R23 for best CPU temp under full load, then if the sight glass is bubbling, add R290 to clear it.
Would having 2 cap tubes running parallel (effectively thats what we have with the R23 cap tube and R290 cap tube) between the high side and low side have any effect on the load they can handle vs. their length.
I ran the cpu at idle (previous results posted using this situation) and 100% load with the new charge, these are the numbers.
Idle
R23
Evap Exit: -47.3ºC
SST: -59ºC (2.2 barg)
SCT: -5ºC (21 barg)
R290
Evap Exit: 18.5ºC
SST: -12ºC (2.2 barg)
SCT: 62ºC (21 barg)
Air in: 22.2ºC
Air out: 27.6ºC
CPU: -7ºC
Full Load
R23
Evap Exit: -40.9ºC
SST: -59ºC (2.2 barg)
SCT: -4ºC (21.5 barg)
R290
Evap Exit: 18.9ºC
SST: -12ºC (2.2 barg)
SCT: 63ºC (21.5 barg)
Air in: 22.0ºC
Air out: 27.7ºC
CPU: 5ºC
The bottom of the compressor isn't cold, is it?
And the sightglass is clear, right?
Nope, its nice and toasty. The suction line just as it enters the compressor is cold, it still has some ice on it.
I know this is aggravating, but we need to keep cutting the cap tube. We have liquid at the entrance. If we cut the cap tube short enough, it will come flooding through, and the exit will get cold. That's the bottom line.
It was a new piece of cap tube, and I am 99% positive that I havent got any brazing material into the ends. Maybe a piece of copper filing or copper oxide has got stuck in it (aenigma mentioned this scenario to me). The end at the drier has been chopped off twice so im sure there is nothing blocking the entrance. Should I try fitting a new piece of tube? Looks like im going to need more propane, im getting kinda low :(
That shouldn't make any difference.Quote:
Would having 2 cap tubes running parallel (effectively thats what we have with the R23 cap tube and R290 cap tube) between the high side and low side have any effect on the load they can handle vs. their length.
However, while we know how many watts load is on the R23 evaporator, we do not know how many watts load is on the R290 evaporator. Apparently a lot more than the R23 evaporator.
I've lost track. How long is the cap tube now?
R290 is 65% of the mass of R23 Volume for volume so just a guess for balance if we are talking flow rates and all the pressures are equil then if you have 10 feet of cap tube for the R23 then wouldn't you have just 6.5 ft of the same ID cap for the propane?
Of course we are ignoring the enthalpy/entropy of these refrigerants.
We have 8 feet of cap tube for the R23, so that would mean we need 5.2 feet for the R290?
Just a guess but if the refrigerants mass is the sole consideration then yes but I don't have and enthalpy charts on R290 so sneak up on it.. Are you recovering your gas each time and reinstalling it?
There as a variety of considerations, but at least we know that we are not chopping in vain, that the difference in mass alone may justify it.
Russell_hq, keep on chopping. :D