Autocascade design

[Chris_F]

I want to know if it is posable to build a single refrigerant Autocascade using R290(propane).

Here is a diagram of how I think it would work.

EDIT: Sorry about the pic. See my second post for the picture.

Any thoughts?

[water_cooler 20]

your pic didn't work and to make a autocascade u would need propane and a low temp gas not just propane

[berkut]

attach it via XS

[Chris_F]

OK, sorry. Here you go.

[berkut]

you need 2 refrigerants to do such a thing

[captaincascade]

Originally posted by berkut
you need 2 refrigerants to do such a thing

yup.

im not good enough yet to build an autocascade:( :( :( :( :( :( :( :(


only tried once, im just not ready.:( :( :( :( :( :( :(


makes me feel worthless, incompetent, and overpaid:(

[berkut]

hehe and im probably leaving the project of a full cascade to 2 small autocascades, they are much easyer for me to build

[Redwolf]

From what I know it can be done with 134A and 23 (50/50 mix)
Use a partical condensor.. Well its designed to only condense the 134A.
Another trick is to have same suction pressures.

Not a project I care to try anytime soon.

[captaincascade]

Originally posted by berkut
hehe and im probably leaving the project of a full cascade to 2 small autocascades, they are much easyer for me to build



rrriiigghhhttt.....good luck with that


my autocascade made -72c with 450psi head pressure.....needless to say... it died....

[water_cooler 20]

450 psi that would scare the **** out of me:D

[Chris_F]

Originally posted by Redwolf
From what I know it can be done with 134A and 23 (50/50 mix)
Use a partical condensor.. Well its designed to only condense the 134A.
Another trick is to have same suction pressures.

Not a project I care to try anytime soon.

From what I hear it can also be done with r134a and CO2.

I don't really care to try it either. ;)

[Chris_F]

What kind of temps could you get with a R290/R290 classic cascade?

[]JR[]

-55c loaded and you can pat yourself on the back. You probably want a R600a lowside compressor or alike becasue of the pathetically small low stage pressures...

]JR[

[]JR[]

Originally posted by Redwolf
Another trick is to have same suction pressures.


But surely you overcome this by sticking a bit of cap tube on the exit of the evaporator into the suction line to meter the evaporating pressure (or if your more clever some kind of dynamic metering device)

]JR[

[Redwolf]

No you dont.
Want to make a gas travel through a cap tube now?
What your talking about is a EPR (Evap Pressure Regulator) and its nothing like a cap tube.

[DaBit]

Sure, you can do it with R290 only, but then you don't have an autocascade, but an extra subcooler. Take a bit of condensed liquid, and use it to subcool the liquid going to the expansion device. IMHO this works especially well for direct-die application due to less flash gas and thus more efficient use of the always too small direct-die evap.

BTW: I know that picture ;)

[berkut]

rrriiigghhhttt.....good luck with that

I have to take in to account that one of my a/c compressors will die during the oil change, leaving me with only 1 compressor. Having 2 systems wich are independent decreases the possibility that when 1 of my compressors die the whole system will be useless. Simply ill be left with only 1 working autocascade instead of 1 useless cascade...

[Chris_F]

BTW: I know that picture

Do you now? :D :D

[Chris_F]

Sure, you can do it with R290 only, but then you don't have an autocascade, but an extra subcooler. Take a bit of condensed liquid, and use it to subcool the liquid going to the expansion device. IMHO this works especially well for direct-die application due to less flash gas and thus more efficient use of the always too small direct-die evap.

How would that work?

[Redwolf]

Dabit
Are you refering to keeping the same suction pressures on the different stages?
If not NM

[Chris_F]

Somthing like this DaBit? :confused:

[Chris_F]

Or somthing like this?

[chilly1]

Originally posted by Redwolf
No you dont.
Want to make a gas travel through a cap tube now?
What your talking about is a EPR (Evap Pressure Regulator) and its nothing like a cap tube.

An EPR is connected to the outlet of the evaporator to keep the pressure up. You still need a metering device. A PEV (Pressure Expansion Valve)is connected to the inlet to regulate the actual pressure in the evap and won't work well in a vacume, A TXV (Thermostatic eXpansion Valve) either internally or externally equilized has trouble at low temps/pressures and will throttle or hunt causing fluxuations in temps and pressures and will maintain the superheat by measuringing the temp of the evap discharge, a hand expansion valve will need constant attention, an EXV (Electronic eXpansion Valve) with a small plc (Programable logic controller) or computer control would be ideal but expensive.. The problem with all these is the amount of refrigerant needed to maintain a liquid column at the expansion device, and the internal volume needed to insure a safe static pressure. As in Chris_F posts the subcooling device can be either parallel or in series with the refrigerant circuits. As is common with all refrigerant systems it is still a trade off lower temps for less capacity. Ideally we want to have the most capacity at the lowest temp.

[Redwolf]

Yes an EPR keeps the suction pressure in that evap up. But it also keeps the suction pressure at the compressor or maybe another evap (freezer/cooler set up) down.

Why do you keep calling it a PEV. What manufacturer calls a CPXV (Constant pressure expansion valve) or AXV (auto expansion valve) a PEV? I know your making your own. But their still the same thing from what you've said. ie they maintan a constant evaporating pressure.

[chilly1]

Originally posted by Redwolf
Yes an EPR keeps the suction pressure in that evap up. But it also keeps the suction pressure at the compressor or maybe another evap (freezer/cooler set up) down.

Why do you keep calling it a PEV. What manufacturer calls a CPXV (Constant pressure expansion valve) or AXV (auto expansion valve) a PEV? I know your making your own. But their still the same thing from what you've said. ie they maintan a constant evaporating pressure.


CPR (Crankcase Pressure Regulator), For keeping pressure in the crankcase from rising to dangerous(to the compressor) levels. EPR(Evaporator Pressure Regulator) to maintain a low limit to evaporator pressure. DPR (Discharge Pressure Regulator) To prevent the compressor from pulling a vacume. CPEV,CPXV,PXV or PEV (Constant Pressure Expansion Valve) are one and the same.
Sorry for the confusion, I have been in the trades for a number of years I have always called it a PEV, I use these for systems that have widely fluctuating loads that have commonly had captubes such as high volume pizza tables to help maintain better more constant temperatures where veggies are kept.
It's the metering portion of the device I customize.

Technically the evaporator Fugger and I built does to some degree refrigerate the refrigerant and we have a blend with two differant boiling points..............Not an autocascade but a subcooling evaporator

[DaBit]

Chris_F: the first picture is what I mean. The liquefied refrigerant is now cooled down to evaporation temperatures, increasing the evaporator efficiency (and decreasing mass flow and refrigerant speed, mind you..)

[chilly1]

Originally posted by DaBit
Chris_F: the first picture is what I mean. The liquefied refrigerant is now cooled down to evaporation temperatures, increasing the evaporator efficiency (and decreasing mass flow and refrigerant speed, mind you..)

How about using a phase seperator and CPXV's
Chris_F I modified your pic....

http://www.blairwing.com/images/autocacade.jpg

[Redwolf]

DPR, now thats something I've never heard of nor seen.
For make tables we use 2 evaps both with a TXV and solenoid valve. Plate for the chill top and low humity evap(s) for the box.
I've always been under the impression a PEVs are more for a constant load issue. They accually hold up in high box usuage? I'd have to see that to believe it.

Subcooling the evap? explain. How can you subcool latent heat?

[chilly1]

All we do is give the refrigerant a chamber that is cooled below the refrigerant's boiling point at the set pressure so the refrigerant will flood making better contact with the warmer heat transferred more effeciently. As for as subcooling the liquid in the block will actually be colder than the liquid in the lliquid line... When I went to this design I gained 15 degF in it's first run all else being equal... Currently With a 1/2hp sc12mlx low stage with r508b I am seeing -86C under load.... P4EE@4.44Ghz... A PEV will respond to changes in load almost as fast as a txv and the now come in wide range multi gas versions....
A DPR sporlan ADRI-1-1/4-0/55 ST sporlan Item # 904927

[Chris_F]

Chilly1, your mod looks nice but how does it work?

[captaincascade]

Originally posted by chilly1
All we do is give the refrigerant a chamber that is cooled below the refrigerant's boiling point at the set pressure so the refrigerant will flood making better contact with the warmer heat transferred more effeciently. As for as subcooling the liquid in the block will actually be colder than the liquid in the lliquid line... When I went to this design I gained 15 degF in it's first run all else being equal... Currently With a 1/2hp sc12mlx low stage with r508b I am seeing -86C under load.... P4EE@4.44Ghz... A PEV will respond to changes in load almost as fast as a txv and the now come in wide range multi gas versions....
A DPR sporlan ADRI-1-1/4-0/55 ST sporlan Item # 904927

this may sound stupid but, until I just looked it up, i had no idea wat a dpr was. once again im telling you, the more mechanicals you add, the more prone to failure you are. I have worked on the most technologicly advanced systems in the world of refrigeration for 10 years..... yes im saying it again.....why wont you believe me? .... do you guys come from an air conditioning background or a refrigeration background? Because refrigeration,especially ultra low refrigeration, is very very different.

bottom line: the more bells and whistles you add, the more that
will go wrong and fail. thats why when we build a system, we ask the user what temp they want,,, set it up,,,, map it, validate it, give them a display and a chart recorder,,,, only thing they can fuss with is a toggle switch,,,, on/off.

[FUGGER]

CC, I think you missed the point. (http://dictionary.reference.com/search?q=capacity) Without it, the temps nose dive. Maintaing it and preventing hunting are key.

Have you worked on anything without a cap tube? This is much different than freezer racing.

[Redwolf]

I'm going to stay out of the who does what crap.

So using Peter to pay Paul. No diff than a liquid line stablizer or a rack's subcool/desuperheater.... OK. The way you worded it the first time threw me off. :)

[captaincascade]

Originally posted by FUGGER
CC, I think you missed the point. (http://dictionary.reference.com/search?q=capacity) Without it, the temps nose dive. Maintaing it and preventing hunting are key.

Have you worked on anything without a cap tube? This is much different than freezer racing.



lol, fugger i know, capacity capacity capacity.. my system wont get any warmer than -90c under load if not colder, useing cap tube.....dont knock it till you jock it!.... you boys really wanna screw around with capacity controls try to keep it simple.....

Dont think im closed minded on the subject,, i have screwed around with a couple ideas.. its hard enough to find a txv for a -80 add the fact that its just as hard to find one that can move quik enough for this aplication. And then try to find all the stuff chillys talkin about for a -80c. i think you guys are going the wrong way hint, think simple hint, even simpler hint


i come off as an arogant :banana::banana::banana::banana::banana: dont i? im sorry, if i where saying it to you it wouldnt sound that way
:(

[FUGGER]

Chilly was being very conservative with -80c, not a txv a pev. It can respond very fast when done right, I lose 1 degree at most going from idle to full load. A txv would be pointless on a second stage like mine. I do have one on the first stage.

I can adjust to any situation on the fly.

Right now I am running on a low charge after we ran out of gas. estimated 8~10oz of gas in my system (weighed the bottle before and after) I adjusted my valve and had no problem finding otpimum capacity and for the load. Thats something you cannot do with a cap tube. You cannot fine tune the existing charge as easy and you have to criticly charge the system so whever you get is what you got period.

These valves will apply to autocascades when done right. Might I suggest picking one up and playing with it CC, you might not go back to cap tube again.

[chilly1]

Originally posted by Chris_F
Chilly1, your mod looks nice but how does it work?

Just an idea. The Pink/Green is a phase seperator. the green is the low pressure gas, the pink is the high pressure gas. The differance is I use PEV's instead of cap tubes... I'm going to build this soon. after my next cascade (2-1 hp bristols)
I will use R134A for low pressure and R23 for High pressure gas.
The pink blue thing is the R23 condenser I'll probably use a tube with aluminum fins inside a suitable tube. The entire system will operate at one suction pressure, I havent done all the calcs on it yet nor have I figured out how to monitor the charge to the two internal refrigerant paths. But I will figure it out.

EDIT : the beauty of this is it will be the same size as a prometeia and may hit -100, may be wishful thinking but??? we will see I'll keep you all informed....

[DaBit]

Chilly1: What PEV did you use, and how do you maintain your superheat on the evap outlet?

[chilly1]

Originally posted by DaBit
Chilly1: What PEV did you use, and how do you maintain your superheat on the evap outlet? http://www.blairwing.com/images/PEV_Block.jpg
Evap and PEV Combo Reveled.. This is not cleaned up yet.....

[Gary Lloyd]

Here's a thought: How about using an AXV with a few feet of cap tube at its outlet? For example, lets say we are modding a prommie from R134a to R404A, R507, or whatever. We cut off the excess cap tube and place an AXV at the cap tube inlet. We then adjust the AXV to get the proper flow through the cap tube. This would solve the AXV's 'doesn't work well in a vacuum' problem, and keep the AXV's weight off of the evaporator.

[DaBit]

Sounds good. It also works fine with a TEV, so why not with an AXV?

There is onyl one 'but': the captube is fed with a two-phase mixture, so a rather large capillary is needed. Or a LOT of captube subcooling.

[Gary Lloyd]

I can only speculate on how it might work in practice. But if the idea worked as I think it may, this might be the 'one size fits all' ideal metering device for all of these systems, both chiller and direct die, and could be adjusted for ANY refrigerant. In fact, once it is adjusted for the heat load with the current refrigerant, if you switch refrigerants, it should adjust itself for the new refrigerant.

[DaBit]

I am still not happy with the evaporator pressure being regulated instead of superheat. I foresee flooding at low loads and excessive superheat at high loads.

Though FUGGER's system proves that it works.

[chilly1]

If your worried about superheat and floodback then a sporlan model # DRHE-6-1/2-0/55, 1/2 ton pressure regulating with an adjustable thermostatic charge.

[Redwolf]

Chilly we really need to work on your TLA usage..(Three Letter Acronym)
I was thinking you were talking about some valve I've never used.. DPR (Discharge Bypass Valve)
We were trying to even comprehend why one would want to control discharge pressure, actual discharge not condensing.

[chilly1]

This particular Discharge bypass Valve can have an adjustable thermostatic element installed or can be run on strictly pressure. It modulates the pressure in the suction line from either a hot gas line or into the evaporator from the liquid line (Not it's real application) Sporlan sent it to me to test it on my evaporator. Their engineer is the one who recommended it. I am working on a 3/4 hp rig for this valve. will post pice and temp as I have them.
Ill try to refrain from the shorthand.
Yes the ADRI-1-1/4-0/55 st is a discharge bypass valve that is used to keep suction pressure up. It is used in hot gas defrost systems, systems with scroll low temp systems where a vacume is harmful to the compressor ect. it is adjustable from 0psi to 55psi,


EDITED FOR TLA......:D

[iboomalot]

the beauty of this is it will be the same size as a prometeia and may hit -100

PERK

[chilly1]

True... Working on it as we speak.

[Redwolf]

Only problem I see with remote bulb version is the they use a Synthetic to metal seat. Those tend to get brittle at very low tempatures.

[chilly1]

I have all the parts for the above drawing except the phase seperator. I am working on that now... Let me run this by you............... I am going to use the return gas to help condense the R134a in the phase seperator. This liquid will feed the Constant Pressure Expansion Valve to cool the interstage heat exchanger where the high stage gas (R23) will condense feeding the low stage Constant Pressure Expansion Valve which will meter refrigerant into the evaporator. I am going to use a 1/2 ton tube in tube for the condenser, a desuperheating reciever with a few modifications for the phase seperator, a 1/2 hp low temp R404/507 danfoss sc12mlx compressor. My own version evaporator. A capped off reciever on the suction line for an expansion tank.
The only thing I am concerned about is the phase seperator.
What do you think?

[Redwolf]

I'm with Gary on the phase seporator. It should be a condensor/seporator to an actual seporator. Using a single pass condensor.
Its just a basic idea.. you'd have to modify it so the 134A is accually condensing before the pre-seporator (ie header).
But ya I too see the condensor and seporator as most of the trick.

CC didn't you try it with a normal condensor and ended up with 450psi head :( What do they use on those small chest auto-c units?

[chilly1]

http://www.blairwing.com/images/condensor1.jpg
How about a little help condensing the R134a.

[Redwolf]

I suggest keeping the Condensing temp around 80 to 85F and dont subcool the 134A till after the seporator. Remember R-23 has a critical temp of 78.6F.. which is an advantage in here.

Start up and getting the system flowing has got to be the hardest part. Once it starts working it should continue..

[chilly1]

Condenser sizing? Standard 1/2 hp condenser and modify it or a larger one, ya r23 will be an advantage. I am questioning wether this will work in temps over 90F?

[chilly1]

Check this out Fugger has the hydrogen compressor that mates to it. It is capable of 70W@40K and 1W@14K
http://www.blairwing.com/images/cryopump.jpg

[PyroTeknik]

ooooooh that sounds really cool i wish i knew what it meant...

[chilly1]

14K = -439F or -259C

[Redwolf]

How about this
(Tempature of each point)

1) H. Evap intlet -30C
2) H. Evap outlet -29C
3) Temp prob header -30C
4) Heat exchanger upper -56C
5) Heat exchanger mid -79C
6) Heat exchanger lower -121C
7) L. Evap inlet -157C
8) L. Evap outlet -155C
9) Champer temp -153C

[berkut]

Originally posted by chilly1
Check this out Fugger has the hydrogen compressor that mates to it. It is capable of 70W@40K and 1W@14K
http://www.blairwing.com/images/cryopump.jpg

is that a stirling cycle engine ?

[chilly1]

Not really, it is acryo pump, it does have two displacer pistons and two drive motors. One for high temp operation (40K) and one for low temp operation ( 14K ) It is simmilar in operation to a stirling engine in that it has a displacer to move the heat from the cold side to the hot side but it actually needs helium circulated through it to remove the heat from the hot side. For this it uses a a water cooled condensing unit running a five horsepower scroll compressor.

[]JR[]

Originally posted by chilly1
Not really, it is acryo pump, it does have two displacer pistons and two drive motors. One for high temp operation (40K) and one for low temp operation ( 14K ) It is simmilar in operation to a stirling engine in that it has a displacer to move the heat from the cold side to the hot side but it actually needs helium circulated through it to remove the heat from the hot side. For this it uses a a water cooled condensing unit running a five horsepower scroll compressor.

That sounds like a stirling engine to me! 10bar helium pressure by any chance?

]JR[

[Gary Lloyd]

I would suggest manifolds on both ends of Redwolf's condenser (parallel runs). The outlet manifold would be the separator.

[chilly1]

10 bar yes stirling simmilar but only using displacer not power pistons.

[chilly1]

Gary, do you have by chance any manuals or data on the engineering of dual phase condensers or do you just combine two enthalpy charts?

[]JR[]

chilly1 there is a stirling cryo cooler (reverse stirling engine) like that too, just a displacer which moves gas from one end to the other and a regenerator (stainless steel screens).

Let me find a picture.

]JR[

[]JR[]

http://www.cryoindustries.com/stirling.jpg

http://www.ricor.com/products/gm/cold-head.htm

http://www.globalcooling.com/stircoolunit.html

Could be wrong but im pretty sure thats a cold head from a stirling cryo cooler.

Personally im not convinced that a stirling engine is particularly difficult to make. Its just I dont fancy buying and machining all that stainless steel ;)

]JR[

[chilly1]

Jenkin/stirling... This is an ADP DE-202 and it is cooled with helium
Simmilar only they don't call it a stirling engine... Same principle.
Just add another one in front of that one and then have the heatrejection area cooled by a condensing unit (5hp)
I don't think the DE 202 has enough capacity to cool a processor, I Can't find any stats on this cryopump for -100 to -200C operation??? any Ideas... I am going to test it at this under a pelt load jus to see?? I will post results... The water cooled condenser that cools it is going to be hooked to my swimming pool which it currently at 39degF 36,000 gal so we'll see.

EDIT: I am worried about the vibration.

[Redwolf]

I would suggest manifolds on both ends of Redwolf's condenser (parallel runs). The outlet manifold would be the separator.
Ya, I thought about this too.. but to be honest with ya I was lazy and didn't want to draw it in. :)

What about the pump issue. It might be better to use a 410A compressor. To bad Copeland doesn't make small scrolls or screws.

Anyone have a copy of this book? Frank Fulkerson's book "Simplified Cascade System Servicing" I hear its good, but out of print.

[chilly1]

I'll look around. There is a company in town that has serviced cascade systems for years I'll ask them next week.
I met an odtimer that did cascade work 40 years age he mentioned books and stuff I'll catch up with him in a week or two who knows....
As far as using r410 compressor probably, the one that is currently in this system is an R22 compressor running helium... I erronously put hydrogen eailer ............

[PyroTeknik]

Originally posted by chilly1
14K = -439F or -259C


dang...... thats cold

[chilly1]

Dark side of the moon..............

[captaincascade]

SCREW IT! i have to build 1.

[chilly1]

Yep U got the disease!:.:rolleyes:

[Gary Lloyd]

Gary, do you have by chance any manuals or data on the engineering of dual phase condensers or do you just combine two enthalpy charts?

I don't do any engineering, Chilly. I've been a hands on service tech for over 35 years, and have yet to design or size a system. I can squeeze every last BTU out of 'em, though. :D