Morphing Air Conditioner into Autocascade System

[AliG]

SGHX? What does that stand for? I figure its some kind of heat xchanger (but what kind)

[godmod]

Suction Gas Heate Exchanger probably?

[AliG]

hmm could be that, come to think of it that would make sense since this is an autocascade, not just an ordinary ss

[jinu117]

SLHX = SGHX (more proper term anyways).
You get better temp at cost of capacity in auto-c based on what mytek said in earlier thread

[mytekcontrols]

Having a little hard time following the heaps of copper but would it be safe to say you have decided to use SGHX for last stage?

Suction Gas Heat Exchanger probably?

All the Heat Exchangers are all in essence "Suction Gas Heat Exchangers", and yes this is an AutoCascade without exception. Check out Post #107 for the complete piping diagram, which should help un-jumble the heap of copper tubing. You'll notice that I really haven't veered from my original course in this regard.

Awesome! Now I am really excited to see how it performs

Me too

[DagoDuck]

OMG, that's really awesome!

[n00b 0f l337]

Wow looks amazing!

[HoriWanderFuLL]

sorry for the noobness but will it work

[kayl]

sorry for the noobness but will it work

horri if anyone can do it, mytekcontrols is the man

[Xeon th MG Pony]

Here in Europe Butane is quite common for camping stoves, but its a wild mix of n-butane, iso-butane, propane and some unidentified hydrocarbons, so I would not recommend using it. Also lighter gas (for lighters, you know what I mean) is mostly butane, but I wouldnt recommend it either.

I supose you could easily make your own fractional distalation system to isolate the N-Butane (R-600)

Cool the cylinder down to -10 then boil off all the gasses then very slowely raise the temp to a coulple degrees below the boiling point of the target gas. If you want to recover the other gases do so via tempriture gradient and the internal berometric pressure will drive flow.

Closer and tighter you control the temp raise to the boiling point of the target gas the more pur it will be.

[Xeon th MG Pony]

Would a water cooled Condencer be too cold for a primary ? I'd be geting 20C leaving liquid refrigerant and even colder after the SGHX (An HX-50).

I have a 6,000BTU Coaxial condencer with a V46AA-1C head pressure modulated flow control valve to lock the condencing Temp (Pressure), I have it set to hold condencing to 110psi on a 3,000 btu compressor (SC12B, R-12, H/M temp w/ Oil cooler). Sensible cooling and subcooling will be insanely good even under max load conditions, thing is with such a topology it may effect phase seperation in an auto cascade type configuration or am I over stressing it?

The above plant is still a blank and I'm thinking of making it to an Auto cascade but thedegree of over cooling I've designed into it is a ocncern to me for the 1st seperation stage.

[mytekcontrols]

Would a water cooled Condencer be too cold for a primary ? I'd be geting 20C leaving liquid refrigerant and even colder after the SGHX (An HX-50).

Actually water cooling is even better. This is the method commonly used for most of the mid-to-large sized systems that Polycold has made (it was also used on some smaller 1HP systems, but not as common). However if you are using chilled water (or just happen to live in a very cold place), and/or anticipate condenser refrigerant outlet temperatures will be much below 18C, then it is wise to run a crankcase heater on the compressor. This will prevent refrigerant saturation in the oil, and save the compressor from having it's cylinder walls stripped of oil on start-ups.

Having a lower liquid line temperature (condenser outlet) will help produce colder temps in all the following stages, and improve phase separation as a result.

sorry for the noobness but will it work

I sure hope so, otherwise I really will have nothing but a useless heap of copper
On the more optimistic side, I'm pretty darn sure it will work, and it will achieve -110 to -120C temps (or colder with a tad bit of Argon added). The only question in my mind is how much load can it take. I might also need to boost the compressor displacement from what I'll be initially using. Basically this stuff is difficult to calculate, when it comes to full blown autocascades such as the one I am building.

[Xeon th MG Pony]

Oh Ok well I live in a cold climate, Canada when it hits absalute 0 we consider wearing a coat here But I've designed the system so the compressor is all ways the warmest part of the system (Puting the control electonics snug against it all the waste heat keeps it warm ) and I'll be using a snap disk thermal cut in to keep it between 50C and 39c.

Ok so thanks I may seriously retask that plant when I have the money to make some HX's

[Xeon th MG Pony]

quintus,
-80C can be obtained with only 2 refrigerants R600 (n-Butane) and R170 (Ethane), which are hydrocarbons, so might be easier to come by (and cheaper). Will probably work with only 2 heat exchangers (auxiliary condenser and cascade condenser), and a single phase separator. Just be sure to make the phase separator fairly large, and stuff the upper end with either steel or copper wool. Having fewer stages does require that you do a better job of phase separation, otherwise too much of the high boiling component gets through to contaminate the final stage. !!!Important Note!!! When fabricating your phase separator, be sure it is constructed to handle the working pressure on the discharge side of your system (350+ psi). Also implement a high side pressure switch to limit over pressure. Either 1 5/8" or 2 1/8" OD ACR hard drawn copper tubing with copper end caps works well.

Would a Tempright 350 series oil seperator work as a phase sep for this aplication?

[n00b 0f l337]

Should be, though with higher flows might want a taller and larger volume phase sep.

[Xeon th MG Pony]

Thats why I'm asking, and don't forget need to factor in the lighter mass of the Hydrocarbon refrigerants. My system is being engineered for low temp not capacity thus flow rates won't be as high, it is all so on a 3,000btu system. It will only have rughley 700 btu/m latent load at 100 microns chamber vacuum. So evap load will be realitively tiny as all I'm doing is recondensing ice.

H2O at -30 has a partial vapour pressure of.0035 psia
Latent heat:
-fussion: 172.63 BTU/Lb
-Sublimination: 1221.2 BTU/Lb.

Density in F^3:
-Ice= 57.5
-Vapour 14^10-4

Product load: 4Lb apx @ apx 85% water (Ice cream sandwich bars)

It is for my vacuum freeze drying unit that I've been designing!

[mytekcontrols]

It's been a while since I posted anything, so here's an update.

Virtually all the refrigerant circuit has been assembled and brazed, including gauges, and expansion tank. The expansion tank was quite a deal, which I got for free when it came off of a customer's unit due to a bad access valve. I simply chopped off the valve and silver soldered in a 3/16" OD tube for connection to my expansion captube.

In one of the pictures you can see my evaporator. This is mainly to be used for doing calibrated heat load tests, and not actually meant to be a permanent fixture. The 50 OHM wire-wound ceramic resistor will be slid inside around the center tube connection. The entire thing will then be wrapped with aluminum foil to radiate any escaping heat back towards the center, and the outside will be insulated very well (I'll probably foam it). This design is called a radiation style heat load v.s. a direct contact heat load. Basically a miniature version of what we use for testing the big Polycold units. Check out my Avatar

My next order of business will be to connect up to 13 thermocouples for temperature profiling the entire HXC Stack, and then insulation + charging.

I'm starting to get excited

[n00b 0f l337]

Oh my god.
Wow.
Seriously Michael; wow. If anyone finds your contact info you might put us all out of business. If I had the cash I'd buy that off you in a heart beat. I wish my work was nearly that good. Maybe the next one will be. I really do like the condensers quite a bit. They really are quite perfect for this sorta application.
Wow.

Also: Still what, 3/4hp rotary? Wow. Love what looks like a hell of a gas selection in the backgroud.
And that a true expansion tank? I've always prefered a suction accumulator since there easier to find.

Also2 (P.P.S.) You have email

Also3:

Your work in red as well? Looks like some more nice HX stacks

And finally (but no promises) Also4:
Still using 6500 BTUH rotary? (Just looked back) Damn wish I had more r14 quite badly now (and r170 or r23). I need an investor hahaha

[mytekcontrols]

If I had the cash I'd buy that off you in a heart beat.

Appreciate it, but this one's not for sale.

Also: Still what, 3/4hp rotary?

I think it's more like 1/2hp --- 6500BTU. Probably should have went bigger, but I am curious what I can get out of something this size.

And that a true expansion tank?

Yep it sure is. Rated for a working pressure of 500 psig. Not bad for FREE
We were doing warranty work for another company, and they gave us a brand new tank to replace this one with, all because the valve stem leaked on the 3-way valve that I ended up cutting off. Just gotta be in the right place at the right time

Love what looks like a hell of a gas selection in the backgroud.

Yes it is, and I put it to good use.

I sent you back your marked up picture with some added notes (see below).

[Polizei]

What gasses are in the back of the picture with the evaporator?

[mytekcontrols]

What gasses are in the back of the picture with the evaporator?

Hi Polizei You must have posted at the same time as I. If you look back, you'll see that I marked them on the picture.

On another subject...
Final packaging:
I will be using this service to create my front and rear panels: Front Panel Express
The 2 gauges will be mounted flush in the panel, along with an IEC (computer type) power jack, and 3 access valve ports (suction, discharge, expansion tank) so I don't have to remove the panels for charging.

The original top (as can be seen behind the unit) is perfectly usable as is.

[Polizei]

No no no, I mean this picture.


The ones on the shelf.

[mytekcontrols]

Oh those tanks

Mainly recovered refrigerant charges that we use to top-up in house units.

[Polizei]

Ah. No worries.

Nice work on the unit.

I dont think Ive ever seen the quick disconnects on the suction or cap before. Would make different evap testing easier for other phase builders here to test to see which evap is best.

Would those valves be ok with the temps?

[mytekcontrols]

Would those valves be ok with the temps?

No not really. At least not the schrader pin aspect. However I've pulled out the pins, and am only using them as flared connectors (-valve). In this regard they will work just fine.

But of course the charge is lost when disconnected.