my autocascade

[gkiing]

Just finished the brazing and assembly tonight, its currently pressure testing @ 150PSI (of CO2) and I'm going to let it sit overnight to check for leaks. The condenser is passive for now but i'm going to add a fan eventually, I put a large desuperheater after the compressor and on the separated co2 gas line so I think that I might not need one. The compressor is a 1/4+ hp matsu:banana::banana::banana::banana:a hbp. My heat exchanger is diy, similar to berkuts but with a few minor changes. In the phase separator there is copper wool in the top half to help with oil separation from the CO2. The evap is just a drill press block, and the suction line is a 3/8" rubber hose, which I'm going to change out for a copper flex hose once I get it because I'm afraid of it cracking under the cold temps. No insulation yet, but I'm going to fix that tomorrow :D. Ordered some 1" wall armaflex (1/2" id) and I'm going to use a cardboard box + polyeurathane foam to insulate the hx.

overview (the thing to the left of the compressor is an expansion tank, these compressors sometimes have a hard time starting).
http://members.shaw.ca/gkiing/autocascade/1.jpg
http://members.shaw.ca/gkiing/autocascade/2.jpg

Nitrogen purging regulator with cga 580 (n2) to cga 320 (co2) adapter
http://members.shaw.ca/gkiing/autocascade/3.jpg
http://members.shaw.ca/gkiing/autocascade/19.jpg

CO2 tank, 20lb
http://members.shaw.ca/gkiing/autocascade/4.jpg

heat exchanger
http://members.shaw.ca/gkiing/autocascade/6.jpg

phase separator
http://members.shaw.ca/gkiing/autocascade/7.jpg

my vacuum pump, old but pulls a 29" vacuum. I always do a triple evac anyway.
http://members.shaw.ca/gkiing/autocascade/8.jpg

pressure testing 150PSIG co2
http://members.shaw.ca/gkiing/autocascade/10.jpg

my cat by the autocascade
http://members.shaw.ca/gkiing/autocascade/12.jpg

drier position
http://members.shaw.ca/gkiing/autocascade/14.jpg

evap and suction line
http://members.shaw.ca/gkiing/autocascade/15.jpg
http://members.shaw.ca/gkiing/autocascade/16.jpg

heat exchanger installed. I wish I hadnt wrapped it with captube first or I would have brazed the co2 liquid line to it as well.
http://members.shaw.ca/gkiing/autocascade/18.jpg

I still have to wire it, insulate it, add a condenser fan, and install the HP cutout. That's all for now, I'm going to charge it tomorrow and see how it fares :toast:

[JSU]

ooooooo looking good gking, why do you have 4 schraders btw? that passive condesnor prolly wont cut it, good luck!

[blinky]

nice whats teh first stage refigerant??

looks good man :toast:

[gkiing]

ooooooo looking good gking, why do you have 4 schraders btw? that passive condesnor prolly wont cut it, good luck!

yeah I know I went overboard with the shraders. One is for the high pressure cutout, one is to remove only r290, another is to remove only co2 another just came on the filter drier, and the one on the other side of the compressor is low side access. I know the passive condenser is ghetto and probably wont work well, I have a window air conditioner that I'm going to rip apart and steal the condenser from.

I havent charged it yet but it will be running r290/r744 (co2/propane).

[kayl]

thats some nice building there.
i hope it goes well for ya.

[total_assault]

awsome..i like the pipe work alot. :toast:

i cant wait to see if that condencer can handle the co2.it's going to get hot..pressure's are going to be high..the HX is small too..it should be interesting.
won't it explode instead of getting hot from pressure?

[Russell_hq]

Those passive condensers are made of steel and have small diameters. Bursting pressures are quite high!

[jan]

Nice looking system.

It won't burst until there is a weak brazing joint. But even then it won't realy "explode".

[gkiing]

Actually I'm changing out that steel condenser for an a/c (~5000btu) condenser I ripped out today. I don't think it could handle it either. This is really just a test system to try out that hx design, I'm building a larger one with a 1/2hp rotary once I figure this all out.

[berkut]

the hx should work, works for me :)

[gkiing]

I did some preliminary testing, the desuperheater was getting really hot but the condenser was not even warm. The lowest temp was around -51.5c but it was charged way out of proportion, and the evap was taking at least half of the supply of r290 which should have been going to the hx. High side was around 240psi and low was around 15psi. I'm starting a new autocascade with the rotary because I dont think this compressor is powerful eneough and I think the ac condenser will work better with the rotary, its probably too large for this small compressor.

hx was around -28c
evap was around -51c (the temp shown is recorded minimum by the way)

0.026 x 1m for hx (r290)
0.026 x 2.25m for evap (r290)
0.026 x 1m for evap (co2).
The evap got cold really really fast before I added co2 but the hx took a while. I think most of my r290 is being hogged by the evap, and also the hx captube is too short and the r290 isint condensing properly.

[berkut]

Insulate :slobber:

add more co2, lenghten the R290 evap supply

do you use the T splitter technique i did ?

[gkiing]

I re-measured the cap tube lengths the r290 to the hx is 0.9m and the co2 to the evap is 0.9m (of 0.026"). I think that the hx captube is too short as It does not reach condensing pressure very quickly, for a little while after startup I hear gas hissing inside it.

The evap has two captubes goign into it, and the one for the r290 is a bit shorter than the co2 inside the evap so it sprays onto the end of the co2 captube. I didn't use the "T" technique but I think its working ok.

How much captube do you think I should add for the r290 going to the evap? Do you think I will gain a lot by insulating? I dont really want to insulate until I get the captube lengths worked out, as the polyeurathane foam is really hard to remove and I wont be able to mod the hx afterwards without a lot of trouble.

[berkut]

you wont finetune it untill you insulate

[berkut]

I do not agree.

The lack of insulation on something as big as a HX is worth about 100-200W static. Remember we have a airflow from the condensers fan.

Lack of insulation on the sucktion line and evaporator is also worth about 100W, and we are talking about a autocascade. 100W extra on the evaporator means 200W for the compressor to push.

If the cap tube is too short (not restrictive enough) adding insulation will make it worse (more flooding). In some designs a cap tube wich is not restrictive enough (most of my systems where i use a cap tu) a proper charge with heavy insulation will cause the system to auto stabilize. At least mine do.

If the cap tube is too restrictive adding insulation (if its not extreme) will probably make the system work properly or very close to what we want to get.

[MaZeR]

you guy's made me want to make a auto cascade too.i have been fine tuning it for the past 3 hr's..

Pic's or it didn't happen! ;)

[gkiing]

I'm adding 0.36m to the CO2 and the R290 hx cap tubes for a total of 1.26m 0.026 (~200W), and also 0.69m more for the r290 to the evap for a total of 2.94m (~75W). Then i'll insulate. I may try a TXV for the r290 going to the hx..

[thesaucier]

Hey sorry about the delay but I just sent the pelt today. ;)

[thesaucier]

I'm a little confused, but I'm going to change my cap tubes now. I'm adding 0.36m to the CO2 and the R290 hx cap tubes for a total of 1.26m 0.026 (~200W), and also 0.69m more for the r290 to the evap for a total of 2.94m (~75W). Then i'll insulate. I may try a TXV for the r290 going to the hx..

That was meant for you I forgot to quote. LOL

[gkiing]

thanks, I'm looking forward to getting it so I can test this thing!

[thesaucier]

Looks like things are coming along good so far!

[gkiing]

I've been having some problems with the phase separator, it need to be taller so the gas/liquid can have a larger distance to separate them. Right now some CO2 is getting caught in the r290 line to the heat exchanger..

[Aphex_Tom_9]

my auto cascade is blazing @ -80c right now with 20 psi lowside and 250 psi high side. no insulation..
wow, blazing indeed...

[gkiing]

Holy sh*t pc ice!! We're getting owned!!!

What's the specs on it.. compressor, condenser, captube lengths, txv?

edit: just read your using r1150.. thats awesome, and looks like your condensing pressures arent too bad either. I think that r290 would have an even harder time separating with r1150, from what i remember it blends well with ethane and ethylene which makes it more difficult to separate.

[JSU]

vapor phase r404a might be a good idea, if you have a bottle that almost done just vapor charge it. youle get some r134a in there.

[JSU]

the 0c shouldnt be necisary seing as its already way past its condensing temp at 250psi, maybe just a larger seperator.

[Russell_hq]

Well it would hurt in a way, where are you going to get the cooling for it :D

On the phase separator, the length is not as critical as the diameter. If you use a larger diameter phase separator then the gas will travel much slower allowing gravity to have a greater effect on the propane/R22 liquid. Increasing the height of an allready too thin separator will have little effect in my opinion.


Thats why the mapp bottle phase separators work so well :D

[Russell_hq]

But then you are just removing capacity from your system for something that does not really need to be. Also if you are evaping propane then the highpressure gas will start condensing too! As all suction lines should be at the same pressure so the bottom of your phase sep will be very cold, as will the rest of it as you will have to insulate the whole thing. I dont think this is a good idea. Just make a larger diameter phase separator. i designed these things in uni, but the idea there was a stripper, a gas came into the chamber and was rained on from above by the stripping liquid. If the diameter was too small then the stripping liquid droplets would be carried out with the gas instead of falling to the base and being drained away. If you want, go and look up info on designing strippers, you will learn some good stuff from that.

[kayl]

nice temps gkiing. a bigger compressor would do nice.
if you use a good size condenser and get that nice n cool things are much easier.

i think that you should use 0.031" capillary line so ya can get longer lengths or even bigger capillary line.
in the end i used 7' of 0.028" first stage longer than you would think and about 8' of 0.031 secondstage. im at 3psig and 250psig with -72.2c evap and -28c hx with r290/744, i wish i had some 1150 to test it with. working on that.

pcice thats some nice temps ya getting there.
whats ya 1st hx temp.

[berkut]

http://www.hoppek.pl/worthless.gif PC ICE :D

[gkiing]

gkiing would you mind if i posted a pic of my unit in here.

im starting to think the phase seperator should be @ or around 0c to insure the r290 or r22 is condenced and not the higher pressure gas..allowing the high pressure gas to flow to the top with little as possible low pressure gas mixed..

looking at all these UEI theraml reading gages make's me think they should just sponsor XS already.. :D

By all means go right ahead, I'm dying to see this thing!!

I'm just insulating my hx with PE foam now, I'm hoping for some -70C temps once I get all the kinks worked out.

[gkiing]

I thoguht my autocascade was kinda ghetto.. anyway im rebuilding it tomorrow. PC ice what were your captube lengths/size?

[kayl]

are you using a suctioline hx there on the dd evap pc ice?

[berkut]

Insulation should do wonders

Autocascades are much more tricky than cascades. And insulation really counts here :D Add Co2 to the mix and you're getting a real nightmare

[gkiing]

Insulation should do wonders

Autocascades are much more tricky than cascades. And insulation really counts here :D Add Co2 to the mix and you're getting a real nightmare

you can say that again.. my evap keeps getting clogged :( I think my suction line is too small.

[kayl]

By all means go right ahead, I'm dying to see this thing!!

I'm just insulating my hx with PE foam now, I'm hoping for some -70C temps once I get all the kinks worked out.

got any pics of it all foamed up