I see that you changed the pic to show my condenser/separator idea. Thanks, Chilly. You do nice work. :D
http://www.blairwing.com/images/Autocascade14.jpg
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I see that you changed the pic to show my condenser/separator idea. Thanks, Chilly. You do nice work. :D
http://www.blairwing.com/images/Autocascade14.jpg
We discussed this condenser idea before I still don't know how to size them I have a call in to my supplier for a quote when and if they get back to me I'll send you what I have.. I am looking for enthlpy charts and other data to better calculate the sizing on these systems, still a lot to learn so I'll keep looking...
Chilly1, if you download and install the coolpack refrigeration utillities you will be able to get a P-h chart for R290. I've linked to it below.
http://www.et.dtu.dk/Coolpack/Files/RefUtil.exe 2.69MB
The cap tubes are:
96" R23
82" R290
I will cut another 12" off the R290 tube and that will bring us closer to the 65% ratio.
I thought the physical properties of the refrigerants would also have an effect on the mass flow rate through the cap tube, so just sizing them by comparing the densities does not make sense to me.
I have nothing to recover the gas to, so its fresh charge from scratch every time I recharge.
If there were shutoff valves in both liquid lines, you could pump down the system to make adjustments (cut cap tubes, change driers, etc.) without losing any of the charge, although you would need to watch the static pressures very closely as they may rise to dangerous levels.
Yup, all this would be great if I had easy access to refrigeration components. Unfortunatly as I am not in the trade or any trade (being a student at the moment) it makes it rather more interesting when trying to obtain parts for my system. As it stands I have to buy all the tools and parts to do anything as my previous tool inventory consisted of a spanner, hammer and some screwdrivers. This makes things somewhat more costly in the short term. :( All this aside it still alot of fun :D
Cap tube has been cut, this time i took it off the other end at the evaporator. Im in the process of recharging the system. Im going to try a new thermal compound between the cpu and evap. Its rated to -150ºC compared to the previous -40ºC.
These are the numbers for the cpu on idle (1.89v@2700MHz approx. 120Watts) with the shorter R290 cap tube
Idle
R23
Evap Exit: -51.0ºC
SST: -59ºC (2.2 barg)
SCT: -5ºC (21 barg)
R290
Evap Exit: 16.5ºC
SST: -12ºC (2.2 barg)
SCT: 62ºC (21 barg)
Air in: 19.3ºC
Air out: 25.1C
CPU: -11ºC
Gary, how much more should I cut off. I've currently got the cap tubes at:
95" R23
70" R290
The R290 tube is getting close to the 5 foot mark. I chopped an inch off the R23 tube when I was redoing the R290, long story but it had to be done.
Aren't you going to post the current full load numbers, too?
Ok, I changed the charge a little to see what I could get, here are the numbers from running full load.
R23
Evap Exit: -42.2ºC
SST: -58ºC (2.4 barg)
SCT: -3ºC (22.1 barg)
R290
Evap Exit: 17.8ºC
SST: -10ºC (2.4 barg)
SCT: 65ºC (22.1 barg)
Air in: 20.4ºC
Air out: 27.1C
CPU: 3ºC
Russel thanks for the chart I am doing the calcs now it will be a few days as I have to pull my old textbooks out there are a few principles I need to brush up on..
Note that the condenser delta-T, under full load, has been progressively increasing as we shorten the cap tube. Assuming the condenser airflow has not changed, we are pumping progressively more heat. This is a good sign. We are getting there.
Keep on chopping. :D
Less than 5 feet is getting into the unstable range, but let's cross that bridge when we get to it. Cut it to 5 feet and see if that does it.
Air flow hasn't changed. How much will I take off this time, 6inches?
Sorry, I have a bad habit of editing. Seems I was editing while you were posting. Cut it to 5 feet and let's see what that does.
R290 and R23 when you Factor in the P/T and Enthalpy The closet we can get is 55% and we are there with the current cap tub length. The amount of heat the refrigerant is capable of carrying (enthalpy) needs to be at the ratio of 65% so we are out of balance by 10% when you started trimming the cap tube you were out 18% What we need to do is test using the exact same load and charge every time and change only one variable. Otherwise the system becomes harder to predict. As a guess I would say that we need to increase the pressure in the r23 evaporator and decrease the pressure in the R290 evap. We need to have an epr valve set at .8 bar between the evaporators This is still preliminary I need to factor in the HOC and the heat added by the motor.
An EPR cannot bring the pressure down to .8 bar. It can only bring the pressure up to .8 bar, IF the pressure drops below that point.
Aint autocascades fun :D
Im having some beers and watching films so work is off for the moment. Im 23 tomorrow, lets hope some birthday luck will kick in when I trim the cap down to 5 feet. I can see the temperatures are getting better with each cut of the tube, so lets hope the next one will do it. Talk later guys, let me know if you think of something ingenious that will help this system. I know you love the autocascade :D
Happy Birthday, Russell. :D
(Trying to remember 23... late 60's... after nam... before college... nope, can't remember a thing... must have been the drugs... LOL)
Sorry, Gary I meant a .8 bar delta across the valve making the suctionpressure on the R290 .8 bar less than the R23 evaporator. This would balance the system and give us an adjustment for tuning it.Quote:
Originally posted by Gary Lloyd
An EPR cannot bring the pressure down to .8 bar. It can only bring the pressure up to .8 bar, IF the pressure drops below that point.
I've done the last chop on the cap tube, from charging and watching temps, I feel this last chop has had a detrimental effect on the system. Could this be possible? Im just pulling down the system at the moment then im going to run full load at 2700MHz@1.89v and give you some numbers. Im thinking a chop on the R23 tube might help, though I could be wrong.
One more thing. Im trying to find out the rpm of my compressor, as I know the displacement I could then calculate the voulmetric flowrate if i know the rpm. I've looked at the manufacturers website and have been unable to find a number. Got any ideas?
Here are the numbers after running full load for 20 minutes:
R23
Evap Exit: -38.7ºC
SST: -58ºC (2.4 barg)
SCT: -3ºC (22.1 barg)
R290
Evap Exit: 20.1ºC
SST: -10ºC (2.4 barg)
SCT: 65ºC (22.1 barg)
Air in: 22.4ºC
Air out: 28.4C
CPU: 6ºC
It looks like you are using a tiny bit less R23 this time. Last time your evap exit was -42C.
I'm assuming the sight glass is clear, right?
I would keep chopping. Even though this takes us into the unstable range, when we see what size works, we can figure out what size to substitute.
The R23 cap tube is just right. I would leave it alone.
The tech sheet says it consumes 698 Watts and has a COP of 1.69 if thats any help.
The sight glass is about 85% full with a stream of bubbles comming up from the bottom.
I have studied the tech sheet, and am still puzzled. The inability to flood the R290 evaporator is the puzzle, but at some point it must push through. How could it not?