Auto-Cascade plan

[LardArse]

I'm planning to start with an autocascade so would like some views from the vets regarding my plan. Here's a rough sketch:



Basically I plan to use a 1 HP Med temp Rotary R22 compressor that are commonly used in window A/Cs. I will use R22 and R1150. Mineral oil will be used and should travel with the R22 nicely and the R1150 should be pretty oil free.
The phase-seperator will be the condenser which will have 2 "T"s piped upwards for the vapour R1150. I saw a small nice condenser that will do this job at the shop just the other day.
Something like this will work?



The HX will be a compact liquid/gas HX which should have enough surface area I hope.
I added in a hand-valve at the liquid line of the R1150 which will be opened during start up to reduce the pressure especially when the HX is not down to temp. This will be closed when HX is down to temp. I do not know if this works at all?
Both stages will be cap tubed, I was thinking of using something close to what my 2 compressor R22/R1150 cascade used. 1.5m of 0.031 for R22 first stage worked good on my cascade but I don't know if such an unrestrictive cap tube would have a much higher % of R22 in gaseous form which will then be traveling with the R1150 to the HX?

[runmc]

Cool!!! Another project.

I'm new to Auto Cascade, so I'll watch closely. Maybe I'll learn something ..

I'm sure you'll do a "Bang Up" job. LardArse Good Luck

[berkut]

Arghhhhh, damn high school exams... if it wasnt for them.... !

What is the hand valve for ?

[LardArse]

Thx Runmc, I'm also very new to this, so I'm lookin for views from the vets such as Gary and Chilly1.
Berkut, what I intend for the hand valve to do is to reduce the head pressure during startup before the HX goes cold. This will be opened until the HX gets cold and then closed. I do not know if this will work?
Since they share the same suction, if the evap ends up at -80+C, low side at about 10 PSI or so, condensing temp will be ~ -30C with R22. That will make high side pressure ~ 300 PSI, pretty scary for me. Too bad I do not have R507 or R404A.

[chilly1]

What about this?

[chilly1]

or this

[LardArse]

Thx Chilly, that last pic seems close to what I plan. What is the rectangle just out from the discharge? Is there a need for the desuperheater?

[chilly1]

Compressor/oilseperstor/filterdrier/phase seperating condensor/suction desuperheater/interstage condenser/evap/pressure expansion valve/ And capillary tubes, the CPEV is to adjust and maintain the delta P between the condensers. If needed the CPEV can be put in the other suction line.. And I would use R507...

The oil cooler/ oilseperator/ filterdrier are nessassary in that order the filter is there and will be fine as the oil cooler drops the temperature enough to cool it below where it will burn the oil/ filter medium.

[placebo]

Hi LardArse ....
First of all deepest respect to you and your work. I have followed your previos cascade very closely ... Also, good thing you didn't kill yourself with that ethylene bottle...

Congratulations also to your decision to now try an auto-cascade!!!

I am currently in the planing and testing phase of my first cascade system. Once that is up and running I will also modify it and try to auto-cascade it

Your drawing and the one's from chilly look very good ...

What do you think about using SWEP plate heat exchangers???

Keep us up to date ...

[Sidewinder]

Chilly:
Wich Program are you using for thosse images (if made by yourself)?

[captaincascade]

to my knowledge anigma and myself are the only to build a fuctioning autocascade. in my opinion, its not worth the headache if you are just going for cold. they can only do as well as a 2 stage classic cascade anyway without adding phase seps and heatexchangers. and seriouse mental breakdown of course

[kayl]

love the drawing LardArse
the laws of physics i just love it

[chilly1]

Originally posted by LardArse
Thx Chilly, that last pic seems close to what I plan. What is the rectangle just out from the discharge? Is there a need for the desuperheater?

The desuperheater will help prevent slugging but isn't nessassary use a suction accumulator...

[LardArse]

Originally posted by captaincascade
to my knowledge anigma and myself are the only to build a fuctioning autocascade. in my opinion, its not worth the headache if you are just going for cold. they can only do as well as a 2 stage classic cascade anyway without adding phase seps and heatexchangers. and seriouse mental breakdown of course

Yes, I know its easier to do it dual compressors, but I want to try it for the fun of it, plus I want to try to make a compactised rig that will be displayed outside a shopfront/office. I'm still deciding whether it will be cooler to have an autocascade display or a dual evap display rig. Its even harder with R22, but the price of it just sways me too much I want to add R290 to lower condensing pressure of R1150 but with the autocascade it will probably "distilate".

Thx placebo, the plate exchangers I havent even seen one before and they are not available to me without some import. But the gurus have good things to say about these.

Chilly, I making it with intention of compactising it so i'm trying to cut down on the unnecessary baggage. I'll see how it goes if I really start on it.

[LardArse]

Well I've kick started the project, but now am leaning towards the dual evap as most people I've asked said that it would draw more attention than an autocas at a shopfront to the main public.
But of course an autocas would be mouch more fun for me.



1HP R22 hi-temp Compressor
I'll try to work out dual evap cap tube length and see if it is acceptable to the gurus such as Chilly and Gary I'll be using a R22/R290/R410 blend which gave nice results but I expect condensing pressure to be ~ R507 or a bit above with my ambient. ~ 220 PSI at load I would believe.

[berkut]

You'll probably need a new filter as you uncapped thet one and humidity spoiled it

[Gary Lloyd]

That doesn't look like a filter/drier. It looks like a strainer.

[chilly1]

Looks Like a strainer/distributor...

[chilly1]

Originally posted by LardArse
Yes, I know its easier to do it dual compressors, but I want to try it for the fun of it, plus I want to try to make a compactised rig that will be displayed outside a shopfront/office. I'm still deciding whether it will be cooler to have an autocascade display or a dual evap display rig. Its even harder with R22, but the price of it just sways me too much I want to add R290 to lower condensing pressure of R1150 but with the autocascade it will probably "distilate".

Thx placebo, the plate exchangers I havent even seen one before and they are not available to me without some import. But the gurus have good things to say about these.

Chilly, I making it with intention of compactising it so i'm trying to cut down on the unnecessary baggage. I'll see how it goes if I really start on it.

If you add R290 to lower the condensing pressure install another phase seperator and heat exchanger to take advantage of it to cool your r1150 so you cool it in three steps instead of 2 this will reduce you head and increase your COP.
I can get stainless plate HX's for you they cost around 200US

[LardArse]

Thx for the info chilly. I guess autocas will be for next time as I have decided on dual evap first.

Just did a bit of piping and brazing:



I'll be trying out another type of simple evap design such that I don't really need to drill much. Much easier to make, I dont mind losing 2-3C.

1.5M of 0.031 fof GPU and 1M of 0.031 for CPU is this ok?

[placebo]

Thx for the info chilly. I guess autocas will be for next time as I have decided on dual evap first.

That is very, very sad ...

I was hoping so much for the autocascade. I know that it is extremely difficult to do but on the other hand it is very, very cool.

And as far as I am concerned I would imagine that people would be more impressed when looking at a refrigeration system using one compressor with 2 different refrigerants. (But I guess that is just my personal opinion).

Nonetheless, I am sure that you will get an awesome system up and running and I am already looking forward to watch it closely.

to my knowledge anigma and myself are the only to build a fuctioning autocascade. in my opinion, its not worth the headache if you are just going for cold. they can only do as well as a 2 stage classic cascade anyway without adding phase seps and heatexchangers. and seriouse mental breakdown of course

What refrigerants did aenigma and captaincascade use in their auto-cascades? I would also be very interested to know the ratio!

Have a good weekend ..

[chilly1]

Actually the ratio of refrigerants is easy to calculate you want balance so base calculations on the enthalpy of the refrigerants this will give you the approxmatley the ratio you will need to tune it based on the effeciency of your HX's and the phase seperator you use. Also the metering devices will need to be proportional.. If you use CPEV's and an epr you could dial it in and use a common pressurs and temperature to calculate. For a more accurate also take into the change in density versus temperature and compare the refrigerants at different points in the system...

[placebo]

Actually the ratio of refrigerants is easy to calculate you want balance so base calculations on the enthalpy of the refrigerants this will give you the approxmatley the ratio you will need to tune it based on the effeciency of your HX's and the phase seperator you use. Also the metering devices will need to be proportional.. If you use CPEV's and an epr you could dial it in and use a common pressurs and temperature to calculate. For a more accurate also take into the change in density versus temperature and compare the refrigerants at different points in the system...

Thanks for that answer chilly, that makes perfect sense....

I am currently planing on using Propylene for the High Stage and Ethylene as the low stage refrigerant. I will try to use the same refrigerants in the traditional cascade first to gain experience. However, since there are only a handful of people and companies out there that have succesfully finished such a system, I'd really like to know what you guys have used and/or would use.

I already have some Dupont Suva 95 (R508b) ... however, I am not sure if it would be a good idea and/or what to mix it with in an autocascade.
Discharge temperature, pressures etc. are a major concern (which kinda is the problem using R1150, I know that R508b would have a lot lower discharge temperature, but what does that mix with? ...

Goal for the final system is it to "chill" a heat transfer fluid down to -80°C (which will probably require an evap. temperature on the low stage of around -100°C).
For testing purposes I have already obtained some Dynalene MV fluid, you can find informations at www.dynalene.com ...
I have two USG of this stuff, it is very smelly and will be replaced with a Hydro-Fluoro-Ether solution later on.

I am happy for every piece of qualified information that I can get at the moment. This should limit the mistakes I will make and the $$$ I will have to waste before I can get it right ...

[placebo]

Chilly and LardArse ....

I am pretty sure you know these already (But I thought I'd post them anyway since it kinda fits in ... ---> http://www.revco-sci.com/ &
http://www.revco-sci.com/literature/...20Freezers.pdf

I spoke with Revco and they told me that they are utilizing a 5 stage Autocascade to reach -150°C . The technician I spoke with also said something about using a slightly modified 1HP Copeland compressor to handle the task.

[zabomb4163]

Originally posted by chilly1
Actually the ratio of refrigerants is easy to calculate you want balance so base calculations on the enthalpy of the refrigerants this will give you the approxmatley the ratio you will need to tune it based on the effeciency of your HX's and the phase seperator you use. Also the metering devices will need to be proportional.. If you use CPEV's and an epr you could dial it in and use a common pressurs and temperature to calculate. For a more accurate also take into the change in density versus temperature and compare the refrigerants at different points in the system...

I dont know if this sounds dumb. But do many people in your trade measure refrigerant using weight? My dad was a heat transfer engineer for 20 years and according to him in the industry the system is set on a system of precise scales and the refrigerant is filled according to weight.

at the factory he worked at it took them 60 seconds to pull a vacume and fill the system with refrigerant. why do amatures use pressure?

please try to go easy on me if i sound like a moron for asking.