Morphing Air Conditioner into Autocascade System

The laws on using R290 in refrigeration systems make me question our governing bodies. I imagine if my AC system outside was charged with R290 instead of R22 it would run cooler while consuming much less power. We can argue all day long on the safety issues of using a hydrocarbon but at the end of the day it won't matter much. I don't see builders dropping R1150 as a refrigerant as R14 is expensive and so destructive. There are R22 substitutes that are primarily R290, and I wouldn't be surprised if we see R600 replace R134a in some applications.

Nol: Walt isn't "jabbing" at you, he's just stating a few facts about the use of R290, especially those who sell units charged with it. (And plenty do !)

While you state that it's not illegal to modify your own tools, I'm pretty sure that Walt is correct about it being illegal to modify a torch.

Regardless, this is overshadowing mytekcontrols's awesome work. (I should really find a new word instead of saying awesome all the time.)

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Originally Posted by yngndrw

Regardless, this is overshadowing mytekcontrols's awesome work. (I should really find a new word instead of saying awesome all the time.)

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Your right,I didn't even relize what thead I posted in sorry mytek.
But even mytek agees safety is alwyas the #1 concern.

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R14 is expensive and so destructive.

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Expensive yes, destructive no. It's a green gas as far as i've read and been told.
As for modify a torch, actually the thing I Have now is not a torch. I'd say modifying the torch end of a... torch. Would be dangerous, you could easily create a bomb, however, cutting off the fitting is not exactly dangerous to those around you.
I agree that its not a jab persay, however I don't like the way it was stated.

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Originally Posted by n00b 0f l337

Expensive yes, destructive no. It's a green gas as far as i've read and been told.

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My last post on this subject before we derail this thread.

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Originally Posted by Wikipedia;

. Its atmospheric lifetime is 50,000 years and global warming factor is 6500 (carbon dioxide has a factor of 1). Although structurally similar to chlorofluorocarbons, tetrafluoromethane does not deplete the ozone layer.

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That being said, it's a fantastic compound.

I leave for a minute (well... actually hours), and you guys take over :D

Just kidding :ROTF:

Actually some interesting points were made about using HC's.

• Yes it is dangerous in the wrong hands.
• Many of them are considered to be very Green.
• As we saw in another post earlier this week, even R22 can be explosive when using poor practices.
• As for legality; at least in Europe, R-600a has been approved for use in home refrigerators.

I truly think that HC's will be the next big change in refrigeration. Same as what we saw happen when CFC's were banned. It no longer is just about Zero ODP, but now also has to be low global warming potential as well. HC's are currently the only viable way to achieve both in a phase change system (at least that I know of). HFC's only address the ozone concerns. HFE's show promise, but for the most part have numerous problems to work out, such as oil solubility.

Thank you all for your input :clap:

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Originally Posted by mytekcontrols

I prefer the later, since it will allow me to keep my package size small.

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Really? I thought you'd be looking at increasing your package size. :rofl:

Very very nice autocascade mytek, best I have ever seen. And you reckon you could get it going better? You're the man. :hump:

impressive work, especially due to the size..

one thought.. how would r23 be as a substitute to r170?

R170 is the substitute for r23 :)

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Originally Posted by n00b 0f l337

R170 is the substitute for r23 :)

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In auto cascades?

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Originally Posted by God

Really? I thought you'd be looking at increasing your package size.

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My wife would disagree :smileysex:

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Originally Posted by tim

impressive work, especially due to the size..

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Tim have you been talking to my wife? :yepp:

Well in all seriousness let's get back to the subject at hand...

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Originally Posted by tim

one thought.. how would r23 be as a substitute to r170?

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As Adam pointed out, R-23 and R-170 are interchangeable with virtually the same boiling points, and very similar COP . Although R-170 seems to work just a little better, perhaps due to it's superior oil solubility.


Static BP Results:

My static BP turned out to be 202 psig (as checked against a Mirror Gauge), with the unit's internal temperature warmed up to 15.8C (I thought it would be as high as 215 psig). It would probably go up a few more psi in a normal room temperature ambient. Part of what I forgot to factor into my calculations when adding up all the refrigerant additions made during the tuning process, is that often times there will be a "soak-in" of the refrigerants with the oil which can lower the overall pressure by 6-12 psi.

Edit: Updated Test chart BP data as seen in this post. Also reviewed heat loss calculations for line and load insulation vs. temperature differential, and added this as well (estimated losses to be 20-25 watts). Total for maximum load = 150 watts + 25 watts heat losses (175 watts)

I did a compressor start-up and immediately came up to 295 psi on the discharge, with a peak current of 4.8 amps. Within 4 minutes of running, the current had backed down to 4.1 amps, and the discharge pressure was at 385 and rising. At this point I did a quick bypass of the discharge to the expansion tank using the manifold valves. This of course immediately dropped the discharge pressure down to about 300 psi. However it once again started rising as the pressure was sucked back out of the tank via the expansion tank captube (no surprise). It didn't take long before the discharge pressure was getting back into dangerous territory. So I manually bypassed it again to the expansion tank. Had to do this several more times within the first 15 minutes of run time, until the discharge pressure stayed in a more comfortable range.

My analysis of all this; seems to indicate that a more restrictive captube going from the expansion tank to the compressor suction would have allowed me to get away with bypassing the discharge only once (greater delay imposed on returning refrigerant back to the system). However with the present setup, and doing multiple bypasses whenever the discharge pressure approached 325-350 psi, I saw an incredibly fast pull-down in my evaporator temperatures. Within 15 minutes the mid-point of my evaporator coil was colder than -100C. This got me thinking.

I could go to a very long and small id captube to increase the delay time on sucking the refrigerant out of the expansion tank. Although I am already using 12 feet of 0.031id. Could go to 0.026id, but I'm not sure if even this would be enough without using an extremely long piece (I thought 12 feet was a lot). Another thought was; why not use a feed-thru PRV between the discharge line and the expansion tank? One that has a blow-off point of 350 psig. This would be simple, and not require any timers. I think this will be my next approach... now just got to locate a PRV.

BTW; for future reference, I'll be calling this a buffer PRV.

In combination with the feed-thru PRV, I'll also be adding a high pressure switch set to 375 psig, as a safety cut-off for my compressor (was always planning on doing this anyway... just haven't implemented it as of yet).


Photo of warmed-up static balance pressure, verified against mirror gauge:

I had a similar issue on my last "autocascade" if you can call it that. Since it's the HXs that aren't cooling down fast enough, would it be wiser to place the buffer PRV past the 1st oil separator on the gaseous so that most of the butane and what little high-stage refrigerants that have entered into the oil/butane solution can begin chilling the 1st HX?

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Originally Posted by n00b 0f l337

Expensive yes, destructive no. It's a green gas as far as i've read and been told.

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lol? R14 has a GWP of 6500! :down:

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Originally Posted by [XC] gomeler

Since it's the HXs that aren't cooling down fast enough, would it be wiser to place the buffer PRV past the 1st oil separator on the gaseous so that most of the butane and what little high-stage refrigerants that have entered into the oil/butane solution can begin chilling the 1st HX?

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That's a good point!

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Originally Posted by gomeler

...would it be wiser to place the buffer PRV past the 1st oil separator on the gaseous so that most of the butane and what little high-stage refrigerants that have entered into the oil/butane solution can begin chilling the 1st HX?

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Yes it would! I'm glad that you picked up on that. It'll be tricky to do on my foam insulated system, but I'll be wanting to tap into the top of my 1st phase separator for the discharge gas source leading into the Buffer PRV.

Edit: Of course I will need to monitor the valve's temperature to be sure it doesn't get too cold for proper operation and re-seating. I suspect it won't, since the valve's operation will be very intermittent and the mass should preclude any problems with freeze-up.

A small wrap heater can solve that issue as well Mytek ;)

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Originally Posted by Nol

A small wrap heater can solve that issue as well Mytek

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Good idea, but I've been researching the idea of using a PRV repeatably as in the proposed Buffer PRV application I have been discussing. Apparently using a PRV this way is not recommended due to inconsistencies in operation after repeated opening and closing. Here is a good discussion on the topic: click here (might need to scroll up to the top of the page)

I think I'll have to go with a pressure switch and solenoid valve instead. This will also allow tweaking the setting and differential as well, to better match the use.

What about a Selenoid Valve in combination with a High Pressure Cut Off with a auto reset? HPCO triggers the Selenoid Valve and resets (closes the Valve) again.

Yep thats easy enough. Or just a handvalve if your willing to deal with un-automated. But a solenoid "open" linked to a high pressure cutoff. You can wire it in a rather odd way that will allow you to cut off to open a shorted circuit if you'd like. Or just have a powered coil all the time holding it open, and should pressures get high cutoff, opens the coil and tada.

Why should he use a hand valve when he tried to fit everything into this nice case...

Hahaha sorry just came to mind ;)

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Originally Posted by godmod

What about a Selenoid Valve in combination with a High Pressure Cut Off with a auto reset? HPCO triggers the Selenoid Valve and resets (closes the Valve) again.

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That is exactly what I intend to do :) I guess I didn't explain myself well enough, but it's good to see someone else thinking the same thoughts.

Does anyone have a good source (as in inexpensive) for an Auto Reset HPCO that can be set to cut-in (turn on solenoid) at 350 psig, and cut-out (turn solenoid valve off) at 300 psig? Most pressure switches that i've seen have an SPDT switch, so the logic should not be a problem.

For my other safety aspect, I just ordered a fixed high pressure switch today from under-the-ice.com (400 psig cut-out, 300 psig cut-in). This will be used to shut-down the compressor if the discharge pressure gets out of hand. Unfortunately the other PS that they stock (350 psig cut-out, 250 psig cut-in) has too much of a differential. Otherwise I would have liked to use it for the Buffer aspect.

And as for the hand valve suggestion adam... well although it would work, I really am trying to have this thing work all on its own (automatic).

www.under-the-ice.com is run by Runmc here ;)
You'll get your order quick, in the mean time *psst ron send me his home address and phone! ;) ;) jk*
Lemme find you a pressure valve.

http://cgi.ebay.com/RANCO-CONDENSER-...QQcmdZViewItem
$50 :(

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http://cgi.ebay.com/RANCO-CONDENSER-...QQcmdZViewItem
$50

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Thanks for the link Adam. I bought it :)

It'll work perfect, just needs a relay to reverse the logic (which I have already).

Why the sad face? I think it was very reasonably priced.

Heh I could get ones with opposite open and close for $25 ish.

Why reverse the logic? Wouldn't it work to take a SV that is curentless Opened?
That would also be a plus of security. If the HPCO fails (which is quite unlikeley) the SV would be opened all the time and HP would not rise.

Michael, do you know, did you try, or can you estimate at which HP the unit will settle if the SV is opened (thus the High side is directly connected with the Exp.tank)?
Maybe a solution with a second captube (not too restrictive) from SV to the Exp.tank would be nice to ensure that the presure drop is not too abrupt...
On the other hand the SV closes anyway at 300psig...

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Heh I could get ones with opposite open and close for $25 ish

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Opps!! Well I guess I should have waited a bit. Anyway what's done is done.

Adam can you post the source for these here for others to see? :)

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Why reverse the logic? Wouldn't it work to take a SV that is curentless Opened?
That would also be a plus of security. If the HPCO fails (which is quite unlikeley) the SV would be opened all the time and HP would not rise.

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Yes it could be done with a normally open solenoid valve, but the cost of this kind of valve is apparently much higher than a normally closed one (besides which, I have some N.C. valves that I got for free).

As for safety in the event of the valve failing to open; this is where the separate HPCO on the compressor power would protect the system. It would take a 2 point failure to have both safeties fail, which is extremely unlikely, and why European Directives and Semi-S8 only require 2 point redundancy in safety circuits for refrigeration systems.

As for cost; I think Chris proposed using a N.O. valve on his new project, and was shocked out of doing so by the price.

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Originally Posted by godmod

Michael, do you know, did you try, or can you estimate at which HP the unit will settle if the SV is opened (thus the High side is directly connected with the Exp.tank)?
Maybe a solution with a second captube (not too restrictive) from SV to the Exp.tank would be nice to ensure that the presure drop is not too abrupt...
On the other hand the SV closes anyway at 300psig...

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I have to confirm this, and it varies as the system begins to cool, but I think if the Buffer Valve were to stay open, the pressure in the expansion tank would settle out at around 275 psig. Of course my tests are presently with the high pressure coming directly from the compressor, and not from the top of the 1st Phase Separator as proposed.

Interesting thought on the captube restriction. I don't really know if this would help much, if any. Kinda think that it is best to buffer abruptly and quickly for the best results (at least with my setup; based on the expansion tank size, and expansion tank captube -to- suction side flow rate).

Yes, those were hypothetical thoughts. I am curious how this solution will work and how it is going to affect the cool down phase. I hope you find time to work on the AC-2 soon! I love this project (gives me a lot of helpful information for my autocascade project).

Thanks as always for sharing all your ideas. And yes I too want to find the time to finish this project. I also look forward to seeing other peoples autocascade creations, whether or not they were inspired by what I am doing, and sharing here.

What size compressor, and how many stages will you be using on yours?

I am not sure yet whether i will take a rotary or a reciprocating compressor. I think rotary is the type of choice, and i will probalby take a 12ccm one with ~7200BTU. My biggest problem is how to make the pipe-in-pipe coaxial HXs. As for refrigerants i will probably take R600, R290, R23 (would prefer R170, but it is very expensive), r1150 and/or R14 (+R50?). But I also have some doubts, because i do not have any experiance with autocascading systems.
(i don't want to spam your nice thread with off topic posts, if you want we can discuss this via pm)

another questioning i were asking myself for days now: what do you think, will there be performance differences between your evaporator coil and a "normal" (direct die) evaporator? I think so. I thnik the performance would be worse, due to the reduced contact surface to the load and reduced surface where the refrigerant can evaporate. On the other hand, it should definately work with a "normal" evaporator, because your load values are in normal regions (100W-300W).

We need different conditions, and really better and bigger evaporators. I've been wanting to get a much larger, almost LN2, pot evap for a while. 2.5" OD, 3-4" tall, stepper all the way up with very large center pole.

godmod --- Some things to take into consideration are how cold do you really need to go? If you can live with -85C to -90C, then leaving out a stage in what I have built, increasing the flows of the remaining 2 captubes (not counting captube #1), and going with a R-600, R-290, R-170, R-1150 (small amount) should get you in the range of 225-250 watts. Doing this and also increasing the compressor to 12cc would probably take you all the way up to 300 watts.

Just boosting the the compressor up to 12cc with what I've done, should easily yield -100C @ 200 watts.

As for how the test load I am using compares to something like a stepper evap, I'm not sure, but here are the specs for mine:

11 feet x 1/4" od Tubing
Internal volume = 3.53 cubic inches
external volume = 6.48 cubic inches
weight = 1.4 lbs of copper

I'd drop the r1150 even in that mix, no need, r290 and r1150 will work out I think.

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I'd drop the r1150 even in that mix, no need, r290 and r1150 will work out I think.

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So leave out the R290 all together? Hmm... Yes, but based on what I've been seeing, you'll have to dumb-down the phase separation to make it work (in other words "very inefficient phase separation --- low volume").

In my early talks about using a combo like R-123 and R-23 (80C difference in boiling points), this was being linked for use with an autocascade with extremely poor phase separation (Polycold P-20). Apparently (and it should be no surprise), as the phase separation improves, so does the need for picking out refrigerants that don't take too much of leap in boiling points from one-to-the-other.

Of course this is all theory that I am spouting off the top of my head, but it does have an intuitive basis in what I have experienced.

Edit: This stuff just keeps on evolving.

Not the r290, but the r170 ;)

Can you say to what extent reciprocating compressors would also be suitable?
I have a bunch of big compressors, e.g. an Maneurop MT-28 (48cc/rev) and many others. although i would rather make a autocascading system with a small (12cc) rotary because of size and energy consumption.

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Not the r290, but the r170

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Got you ;)

There would be a 61C gap between the R-290 and the R-1150... might be wise to implement a Partial Phase Separator on the last stage prior to the final cascade condenser (see below). This way some liquid will be passed on to the next stage along with what ever gas is present, there by insuring that a disconnection between stages doesn't occur (as what happened to me on my R-600/R-170 charge test).

Some experimentation will be needed to find the optimum height for the exit tube.

Edit: Notice that this is a modification of my existing upper stage phase separator design.

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Can you say to what extent reciprocating compressors would also be suitable?

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No problem using reciprocals. just so long as motor size vs. displacement is reasonable (medium to high back pressure).

Yeah I think that would work well, what filters do you use? I think I asked before but I cant seem to find something similar to what you use.

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Originally Posted by mytekcontrols

No problem using reciprocals. just so long as motor size vs. displacement is reasonable (medium to high back pressure).

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Thanks for the Info.
edit: ok, i already thought this. and of course R404a comps would be better, because of stronger motor (high HP)

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Originally Posted by mytekcontrols

This way some liquid will be passed on to the next stage along with what ever gas is present, there by insuring that a disconnection between stages doesn't occur (as what happened to me on my R-600/R-170 charge test).

Some experimentation will be needed to find the optimum height for the exit tube.

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The right "length-setting" might be really hard to find. Aren't the liquid levels loaded different than in idle? The problem i see here is that "the gas out pipe sucks" either liquid or gas. There will be an alternating oscillating gas-liquid compositon. I visualize that that way: a constand volume flow out of the strainer through the gas-discharge. the composition will be, depending on the refrigerant level in one moment liquid, until level drops, then gas until liquid is high enough. maybe sometime it will equilibrate, but I think varying load could cause a oscillating system (keyword: feedback). Just thoughts, might also be delusions :D

No I think thats valid, however by charging till you always have spill over, you can fix said problem ;)

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Originally Posted by godmod

The problem i see here is that "the gas out pipe sucks" either liquid or gas. There will be an alternating oscillating gas-liquid compositon.

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Originally Posted by Nol

No I think thats valid, however by charging till you always have spill over, you can fix said problem

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You are both correct :)

Yes the idea is to lower the threshold for flood-over within the phase separator, but mainly during low-to-moderate heat loads. I believe it is during this time that the system can get in trouble when refrigerants with wide differentials in boiling points are used. It goes into what my original mentor would have called "self refrigeration". I call it inter stage disconnection. There is another technique that has been used, which combines a distributor with a phase separator, although in a system with a single tube-in-a-tube HXC it isn't required.

Basically you want to keep the first stage separator from getting too cold and stealing all the lower boiling refrigerants through absorption into the warmer boiling refrigerants (what I call the liquids, due to the fact that they are charged into the system with either a charging glass or a scale in their liquid state).

The simplest partial separator is to use an inclined tee, with the gas exiting the side connection. Although I'm not sure how well this would work in a very tiny unit (the strainer that follows would still hold a lot of liquid).

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Originally Posted by Nol

Yeah I think that would work well, what filters do you use? I think I asked before but I cant seem to find something similar to what you use.

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I get them from Baker Distributing which is a local refrigeration parts wholesaler. I think they are part of a national franchise.

Ah I was wondering about no load, freeze back through all the stages I guess...

very nice as already said :)

i'm actually thinking, since i don't get anything less then 14-17k btu rotarys and up.

i'm thinking of using one of those which is 3-3½times larger then your compressor (27-34ccm). how would you suggest to dimension the captubes? make them 3-3½times less restrictive or is it something else to remember?

condenser and hxes need to be larger as well due to the larger compressor and flows.

regards
Tim

best regards
Tim

Figure out how many times your displacement is, take his mass flow figures and multiply by that and then find new captubes to fit your new massflows.

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Originally Posted by tim

i'm thinking of using one of those which is 3-3½times larger then your compressor (27-34ccm). how would you suggest to dimension the captubes?

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This will link you back to the discussion on captube sizing:

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Originally Posted by mytekcontrols

...I also included a captube sizing chart in case you wish to use a different ID.

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More on Partial Phase Separators

Here is another idea out of the past, that was used to create a partial phase separator that would meter out liquid as the liquid level rose within the separator. The higher the level, the more liquid would be passed on to the next stage along with the gas.

Metered Partial Phase Separator:

Very cool idea indeed. I like it. Sending you an email Mytek.

EDIT: Actually just had an idea since I can't seem to find those strainers...

Although I have presented several schemes along this theme, my answer would be NO!

The reason being; you'll be sacrificing thermodynamic efficiency in the process. It is always better to design with the best possible phase separation, heat transfer, and minimal pressure drop. If you have to resort to partial phase separators to get your system to work properly, then you're probably sacrificing efficiency in doing so.

Of course sometimes due to the refrigerants that are available (or not available), you are left with no choice. So because of this, I think it is still important to cover the topic of partial phase separators, but it is also just as important to try to design without relying them.

So in your opinion, propane to ethylene. Thats -42C to -104C. Or a 62C boiling point delta. Do you think a partial phase separator would be necesary? R600 to R170 is a 89C boiling point delta.

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So in your opinion, propane to ethylene. Thats -42C to -104C. Or a 62C boiling point delta. Do you think a partial phase separator would be necesary? R600 to R170 is a 89C boiling point delta.

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I wish I could give you a definitive answer, but as you can imagine, it depends on a lot of different factors (eg; phase separator efficiency for one). Since I don't have ethylene or anything else with this same boiling point, I can't run a test. But you can ;)

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Originally Posted by n00b 0f l337

So in your opinion, propane to ethylene. Thats -42C to -104C. Or a 62C boiling point delta. Do you think a partial phase separator would be necesary? R600 to R170 is a 89C boiling point delta.

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On a similar note, could you get away with strictly R290/R1150 or should you keep the R600 loop for compressor cooling and as a way to help purify the R1150 by having 2 loops to pull the R600/R290 components out of the mix?

Basically R290 -> R1150 or R600/R290 -> R290/R1150 -> R1150.

ninja-edit: Thinking about it, I'm betting the 2nd option would be better as that 1st mixture will boil somewhere close to propane, say -30C. Hopefully the 2nd mixture would boil around ethane's BP, and the final stage would be nearly pure R1150. I'm in the planning stages of my autocascade which is why I ask and I don't want to screw it up :)

Hahaha Michael ya should get ethylene, might be able to help you guys replace r14 ;)

What about blending 2 HC? Don't you think they will blend to form an azeotropic gas in the end? Some of you use blend on cascade (methan+propan), so why would it be different here?

You're expecting to condense ethan or ethylen with respectively R600a or R290? Good luck :rolleyes:

Considering they won't blend (I'm not sure they won't...) :
R170 is the hardest mid range second stage refrigerant (~-85°C @ 1bar like R23 and R13) to condense because of very high latent heat of vaporisation. A R600a compressor must have 65% greater displacement than needed with R12 to get the same capacity, so don't expect to remove the heat of R170 to condense it at decent pressures.

That's worse with ethylen and propan :D

They will be blending, and theres also going to be saturation. And not even isobutane, we're talking about normal butane.

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Originally Posted by Clemmaster

You're expecting to condense ethan or ethylen with respectively R600a or R290? Good luck
Considering they won't blend (I'm not sure they won't...) :
R170 is the hardest mid range second stage refrigerant (~-85°C @ 1bar like R23 and R13) to condense because of very high latent heat of vaporisation. A R600a compressor must have 65% greater displacement than needed with R12 to get the same capacity, so don't expect to remove the heat of R170 to condense it at decent pressures.

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Actually I think I can condense it at reasonable pressures with only R-600 (43 suction/240 discharge):

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Originally Posted by mytekcontrols

First Test Results (-102.6C @ 125 Watts)

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And with R-123+R-22 (49 suction/275 discharge):

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Originally Posted by mytekcontrols

-101C @ 150 Watts Applied Load

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Originally Posted by gomeler

On a similar note, could you get away with strictly R290/R1150 or should you keep the R600 loop for compressor cooling and as a way to help purify the R1150 by having 2 loops to pull the R600/R290 components out of the mix?

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I think it best to use both the R600 and the R290 for the reasons that you stated in the end.

Edit: I'll be running my next test with R600 and R290.

Oh cool made a r290 adaptor? ;)

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Oh cool made a r290 adaptor?

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Yes I did. Thanks for the idea :)

Still waiting on my extra parts to arrive first, so I can implement the buffer valve feature. But soon.

No problem and not my idea, been used here for years :)

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Originally Posted by mytekcontrols

Actually I think I can condense it at reasonable pressures with only R-600 (43 suction/240 discharge):

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You're talking about condensing R170 with R600 right?

Yes he is, butane will boil much lower then its normal BP as it absorbs and saturates with ethane.

How do you know where it will actually saturate?

Ethane involve a very high condensing rejection so you must have a good displacement to carry such load on first stage...

It will saturate everywhere... Dunno what you mean by that? The auxillary condenser before the first phase separator will lower refrigerant temps and boost saturation as well.

Clemmaster, When I made the statement:

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Actually I think I can condense it at reasonable pressures with only R-600 (43 suction/240 discharge)

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I really meant to say "I know" instead of "I think". The reason I say this is, that I know beyond a shadow of a doubt, that the only way I could have obtained -100C or colder with a charge based on R-600, R-170, R-14 -and- with a 240 psig condensing pressure -while- evaporating into a 43 psig suction, would be by condensing at least the R-14, which would have minimally required condensing and evaporating the R-170.

My questions to you are: Have you studied, or have been working with autocascades? Do you understand that an autocascade is not the same as a standard multi-compressor cascade, and that in an autocascade a mixture of refrigerants are fractionated out and used to cool successive stages? If not, then this may be the source of your dilemma about why I was able to condense R-170 (and R-14 which has a much lower boiling point), while using only one other refrigerant (R-600).

One last question for you: Have you read through this entire thread? If not, then I would highly recommend that you do so, since much has been covered on the topic of autocascades and how we think they work.

I'll be the first one to admit that there has been much theorizing on the subject, and I'm sure you'll find that some of the later posts will be in conflict with what had been thought to be fact in earlier ones. But overall I believe it has been a very productive effort, and hopefully is allowing others to have the knowledge to build their own autocascades, and have their own successes at condensing R-170, and/or R-1150, and/or R-14.

Mytek if you need a rotary cascade as you were thinking from the r22 problem thread, send me an email I have a large inventory at the moment.

I just read over my response to Clemmaster's questions, and although I didn't mean to come off as and over bearing know-it-to-all, I think it could possibly be perceived that way. My apologies go out if it felt this way to you as well Clemmaster :wiggle:

Anyway the point I was really trying to make is, that there is a tremendous amount of information on autocascades already covered by this thread. So to keep from being redundant (by going over what has already been discussed), it is best to start at the beginning, and read it through to the end. That way we can try to keep this from getting into a 1000+ postings, which to say the least, gets a bit unwieldy.

However, I am always happy to try and answer the questions, and try to do so as accurately as I can.

Also... :welcome: to this thread.

Quote:

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Originally Posted by mytekcontrols

Clemmaster, When I made the statement:

I really meant to say "I know" instead of "I think". The reason I say this is, that I know beyond a shadow of a doubt, that the only way I could have obtained -100C or colder with a charge based on R-600, R-170, R-14 -and- with a 240 psig condensing pressure -while- evaporating into a 43 psig suction, would be by condensing at least the R-14, which would have minimally required condensing and evaporating the R-170.

My questions to you are: Have you studied, or have been working with autocascades? Do you understand that an autocascade is not the same as a standard multi-compressor cascade, and that in an autocascade a mixture of refrigerants are fractionated out and used to cool successive stages? If not, then this may be the source of your dilemma about why I was able to condense R-170 (and R-14 which has a much lower boiling point), while using only one other refrigerant (R-600).

One last question for you: Have you read through this entire thread? If not, then I would highly recommend that you do so, since much has been covered on the topic of autocascades and how we think they work.

I'll be the first one to admit that there has been much theorizing on the subject, and I'm sure you'll find that some of the later posts will be in conflict with what had been thought to be fact in earlier ones. But overall I believe it has been a very productive effort, and hopefully is allowing others to have the knowledge to build their own autocascades, and have their own successes at condensing R-170, and/or R-1150, and/or R-14.

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Don't worry for me :rolleyes:

I didn't look at the pdf, and I now know the purpose of this cooling, nothing to be afraid of indeed :up:

Quote:

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Originally Posted by mytekcontrols

I just read over my response to Clemmaster's questions, and although I didn't mean to come off as and over bearing know-it-to-all, I think it could possibly be perceived that way. My apologies go out if it felt this way to you as well Clemmaster :wiggle:

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No problem, that's the way I talk too I understand that it isn't personnal :up:

I apologize not having read the entire topic, I will, I'm sure I will find lots of information. I didn't know where the blend would saturate but as you said, It will saturate somewhere between butan and ethan point and that's the way it's supposed to be, that now make sense :up: . I've always been thinking of "quasi-non blending" refrigerant (R290+R744 or R290+R23) not on HC mixtures and that's a part I'll we be working on!

Thank you :up:

Quote:

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Originally Posted by Clemmaster

I've always been thinking of "quasi-non blending" refrigerant (R290+R744 or R290+R23) not on HC mixtures and that's a part I'll we be working on!

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I like the term "quasi-non blending". In other words; a virtual refrigerant, one that exists only under certain conditions :idea:

This is probably as good of a description as any, for what happens to the combination of refrigerants used within an autocascade as they are subcooled, and then go into solution with other nearby boiling point neighbors. Thus creating a condensate with a unique boiling point.

I also think that the other affect that we see to lowering temperatures, is that brought on by evaporating a condensate into an environment which consists of gases that have a lower boiling point then the condensate itself (eg; R-14 evaporating into Argon rich environment). This could be compared to the effectiveness of an evaporative water cooler in a high humidity environment vs. a dry low humidity one. The low humidity environment, being of a large part composed of lower boiling point gases, allows for an increased flow of heat from the evaporation of the water. Where as the high humidity environment is less effective due to saturation.

This is all part of the fun and magic to getting an autocascade to work properly :up:

Quote:

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Originally Posted by mytekcontrols

I like the term "quasi-non blending". In other words; a virtual refrigerant, one that exists only under certain conditions :idea:

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Yes I don't know how to call these mixtures because two gases always start a reaction (even if it stops really quick, that's the way it is :( ).

Quote:

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Yes I don't know how to call these mixtures because two gases always start a reaction (even if it stops really quick, that's the way it is :( ).

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This has been a problem for the engineers at Polycold for years. There was only one guy from Russia that had come up with a program that could accurately simulate a refrigerant mix for an autocascade. He had developed the program himself, and never shared it with anyone else. Unfortunately for Polycold he left, and went back to Russia, taking the program with him.

I received the high pressure switch yesterday (see photo below). It looks like it'll do the job just fine, and as it turns out, has the correct switch logic (Close on Pressure Rise). The Ranco Part Number is: 010-2054, and it is called a Condenser Fan Cycling Control. Range: 100 to 400 psig, Differential: 40 to 150 psig.

I will most likely leave the differential setting at 40 psig (default), and set the cut-in to 350 psig.

Great, what about this ?
http://www.fullgauge.com/PDF/PCT-1600.pdf
http://www.fullgauge.com/PDF/PCT-420.pdf
http://www.fullgauge.com/PDF/PCT-100Ri.pdf
http://www.fullgauge.com.br/
regards,
Marvin

Marvin --- those are pretty sophisticated controllers, but I think a bit more then what is really required for pressure control on the AC-2 unit.

Below you will see an updated piping diagram showing the Buffer Valve and Pressure Control.

Yep thats the switch :)
HPCO will cut out, a fan cycler will cut in. And they can be cheaper then that, but thats a rather high quality one :)

I have almost completed all the plumbing changes required for the Buffer Valve addition, and have also fabricated, and installed an access port manifold.

My problem is that the pressure gauges I was using are basically cr_p!!! The readings were off by 10 psi from when I had initially calibrated them. What I need is at least one reliable gauge (suction side) that is fairly small, and can be easily panel mounted. Anybody got a good source? :shrug:

P.S. I'll be posting some pictures of the plumbing changes momentarily (need to switch computers).

Gonna betray a source for you Michael, hope you enjoy it ;)
(Jk its just ebay)
http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA:IT&ih=005
Hows that?

You are the MAN!!!!
Thanks Adam that's a great deal :)

As promised, here are some pics on the latest changes:

1. Access Port Manifold (unpainted)
2. Access Port Manifold (painted)
3. Access Port Manifold connected
4. Buffer Valve and associated Pressure Switch
5. High Pressure Cut-Out switch

Now just got to wire it all up

Looking very sexy there.

VERY nice idea about the access port manifold!

nice work Michael, thats an awsome idea for the access valves hey.
WIth the suction line access port where do you braze that into so it doesnt freeze over? the expansion tank?


WHat the purpose of the buffer valve?

Quote:

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WIth the suction line access port where do you braze that into so it doesnt freeze over?

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Good point! I forgot about that. :shocked:
Hmmm... my connection is almost 6" away from the suction line... could be a problem. I can insulate the line, but you are right, there will probably still be enough conduction to probably make it sweat (I doubt that it will freeze). I might need to also use some armaflex tape on the painted steel plate, and use small spacers between it and the front panel that it will eventually get mounted to. A little sweating on the exposed end of the access fitting and brass cap should be ok.

Quote:

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...the expansion tank?

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Actually one of the access ports does go to the expansion tank as well. Both are needed due to the pressure restriction of the expansion tank captube (couldn't expect to pump a very good vacuum through 12 feet of 0.031" ID captube).

:idea: I guess if I really had a freezing problem, a piece of stainless steel tubing could be soldered between the suction line and the manifold port connection. Or a small power resistor (used as a heater) clamped to the backside of the manifold mounting plate and connected to my power would also work. At 120 VAC, a 3K 5 watt resistor would probably do it.

I'll just have to see how it goes (a bit of trial and error). :shrug:

Quote:

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WHat the purpose of the buffer valve?

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If the discharge pressure gets too high during start-up/cool-down, it dumps some of the refrigerant gas into the expansion tank to lower the amount of refrigerant circulating in the system. This reduces the discharge pressure, and then slowly meters the refrigerant back into the system via the expansion tank captube. Since the gas source is taken after the 1st phase separator, we leave the bulk of the highest boiling refrigerants (as separated condensates), to continue the work of cooling the succeeding stages, so that eventually enough of a phase change has occurred in the other circulating refrigerants to keep the discharge at a more reasonable pressure.

Here is a drawing showing the construction details of the Access Port Manifold (Dimensions are in INCHES --- all holes are aligned to horizontal CenterLine):

Suction Gauge is on order (thanks again to Adam). When this comes in I'll be able to complete the pressure circuit, and put the unit on a vacuum pump.

Until then, I have a bunch of wiring to do. And of course I'll need to think this over a bit, so as to keep everything neat and to the point (no sense in rushing through this, especially since the rest of the unit is coming together so well). Still gotta find a good location for the RUN Capacitor. Also need to install a 10 amp 120 VAC relay between the compressor and the HPCO, since it is only rated for about 3 amps. The 400 Psig HPCO was a great find, due to its very small size, and inexpensive pricing. I got this from Under-The-Ice.com (thanks Ron).

My next test will be with R-600 and R-290 as my liquids. I will probably stick with the same ratio and amounts of the other refrigerant gases as used in the last charge. I'll post the results and the new charge specs.

Here's a pic of the 30" - 0 - 300 psig gauge I ordered from Frosty-Freeze A/C Products Company (looks to be a good quality ASHCROFT gauge, not bad for under $5.00):

I'd put the capacitor right below the fan motor, and again no problem, least I can do :)

Quote:

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Originally Posted by mytekcontrols

If the discharge pressure gets too high during start-up/cool-down, it dumps some of the refrigerant gas into the expansion tank to lower the amount of refrigerant circulating in the system. This reduces the discharge pressure, and then slowly meters the refrigerant back into the system via the expansion tank captube. Since the gas source is taken after the 1st phase separator, we leave the bulk of the highest boiling refrigerants (as separated condensates), to continue the work of cooling the succeeding stages, so that eventually enough of a phase change has occurred in the other circulating refrigerants to keep the discharge at a more reasonable pressure.

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I love explainations like these. :up: Well said.

I knew why you used the valve, but not how or where. Great idea.

Seems rather common in these systems, at least newer ones, I love the idea, its protection of sorts, like a burst relief valve, however less dangerous ;) And I think we saw CryoTek do this as well. Allows HX's to chillax out.

Quote:

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Originally Posted by Nol

I'd put the capacitor right below the fan motor...

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Good idea, but since it would be a bear to gain access to this area now, I think a good compromise would be to put it above the fan motor instead.

Quote:

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Originally Posted by Polizei

Quote:
Originally Posted by mytekcontrols
"If the discharge pressure gets too high during start-up/cool-down, it dumps some of the refrigerant gas into the expansion tank to lower the amount of refrigerant circulating in the system. This reduces the discharge pressure, and then slowly meters the refrigerant back into the system via the expansion tank captube. Since the gas source is taken after the 1st phase separator, we leave the bulk of the highest boiling refrigerants (as separated condensates), to continue the work of cooling the succeeding stages, so that eventually enough of a phase change has occurred in the other circulating refrigerants to keep the discharge at a more reasonable pressure."

I love explainations like these. Well said.

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Thanks :)
My goal is to get responses like yours. That way I know I am hopefully going down the right path in conveying my thoughts as clearly as possible.

Quote:

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Originally Posted by Polizei

I knew why you used the valve, but not how or where. Great idea.

---

Quote:

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Originally Posted by Nol

Seems rather common in these systems, at least newer ones, I love the idea, its protection of sorts, like a burst relief valve, however less dangerous And I think we saw CryoTek do this as well. Allows HX's to chillax out.

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Yep! Quite common in some of the Polycold units, especially the larger models where it helps keep the size of the expansion tank(s) more reasonable. I think the units that CryoTek builds use a different system, since they use no expansion tanks what-so-ever. However I do believe you are right about him discussing it on this forum. I wish he would get back on here, because I would love to see him join in on some of these conversations.

So ya still havent revealed it, but what are you using this little thing for? Do you need a CPU evaporator setup? If so I'd gladdy braze one up and send it your way.

Quote:

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Originally Posted by mytekcontrols

Good point! I forgot about that. :shocked:
Hmmm... my connection is almost 6" away from the suction line... could be a problem. I can insulate the line, but you are right, there will probably still be enough conduction to probably make it sweat (I doubt that it will freeze). I might need to also use some armaflex tape on the painted steel plate, and use small spacers between it and the front panel that it will eventually get mounted to. A little sweating on the exposed end of the access fitting and brass cap should be ok.


Actually one of the access ports does go to the expansion tank as well. Both are needed due to the pressure restriction of the expansion tank captube (couldn't expect to pump a very good vacuum through 12 feet of 0.031" ID captube).

:idea: I guess if I really had a freezing problem, a piece of stainless steel tubing could be soldered between the suction line and the manifold port connection. Or a small power resistor (used as a heater) clamped to the backside of the manifold mounting plate and connected to my power would also work. At 120 VAC, a 3K 5 watt resistor would probably do it.

I'll just have to see how it goes (a bit of trial and error). :shrug:


If the discharge pressure gets too high during start-up/cool-down, it dumps some of the refrigerant gas into the expansion tank to lower the amount of refrigerant circulating in the system. This reduces the discharge pressure, and then slowly meters the refrigerant back into the system via the expansion tank captube. Since the gas source is taken after the 1st phase separator, we leave the bulk of the highest boiling refrigerants (as separated condensates), to continue the work of cooling the succeeding stages, so that eventually enough of a phase change has occurred in the other circulating refrigerants to keep the discharge at a more reasonable pressure.

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That makes sense and would help alot.

Sweating schraider valve will be fine i think. When looking at your
drawings i was interested why there was a access valve on your expansion
tank and though you might have used that to charge and tune the system. I
know when using rotarys with cascades and tunning mine freeze over big
time and you cant remove the refrigerant gauge hose unit will you have
turned the system off and left it for ages. If i take it off even when its
almost defrosted my schraider valve leaks gas which stuffs my charge up.

So i was trying to decide for the cascade im building now to have 2 low
side access points line in your autoC and use the one on the suction line
for vacuuming and then use the one on the expansion tank for charging??
You think thats ok?? or any suggestions. I like you idea of bring all the
access valves together at the one point, will make tunning much easier
with the case all done up.

Quote:

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Originally Posted by kayl

So i was trying to decide for the cascade im building now to have 2 low
side access points line in your autoC and use the one on the suction line
for vacuuming and then use the one on the expansion tank for charging??
You think thats ok?? or any suggestions.

---

Yes that would work, but you would of course have to allow for the delay in balancing out the gases when charging through the expansion tank, and into the system via the expansion tank captube.

I take it by your description, that the access port connected directly to your suction would not be a part of your manifold. And when the vacuum process was completed, it would be capped up and insulated, thereby leaving only 2 externally accessible ports (expansion tank & discharge). Was this what you had in mind?

I could see how the upper stages in a standard cascade would be problematic when it came to freezing suction side ports. In my AutoC I wont have nearly the problem, since my suction is not going to be much below 0 C (low load), and probably around 5 C under full load. So I think the resistor heater idea would most likely solve any sweating, or slight freezing problems that might be encountered in this situation. The resistor can be one of those metal encased types bolted to the backside of the manifold plate with a little heatsink compound, located close to the suction access port. This could then be connected to the compressor power source, only coming on when the compressor is running.

Although if you have the space, a foot or so of small o.d. stainless steel (3/16" or 1/4") tubing would provide enough isolation, due to the much poorer heat transfer as compared to copper tubing. This would allow you to bring all 3 connections out to your manifold as I have done, and not have any freezing problems. Of course the first 8 to 10 inches where it connects to the suction will need to be insulated.

Photo of suggested Power Resistor type for use as manifold anti-condensation heater (select appropriate wattage for application):

Hey Michael, any progress?

Progress??? What's that? :)

Yes there has been some, but not as much as I would have liked. Basically I am still buttoning up several loose ends:

• Insulated compressor suction line (boy was this a bitc_h to do with every thing else in the way)
• Patched foam insulation where I had changed some of the plumbing
• Finalized test load by foam insulating inside of a 4" ABS tube with end caps
• In the process of doing final electrical wiring

Hopefully will be recharging this week, and then test.

Quote:

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Originally Posted by n00b 0f l337

So ya still havent revealed it, but what are you using this little thing for? Do you need a CPU evaporator setup? If so I'd gladdy braze one up and send it your way.

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hey mate i am also curious... what evap are you using?

Teyber --- I'm using a coil with a radiant heat source as my dummy load.

Quote:

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Originally Posted by mytekcontrols

Here's a look at the test set-up...

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If you look at my avatar you'll also see a representation of a large test load made for up to 5000 watts. I am simply using a very small version of this same design. The copper tube coil is wrapped in aluminum foil to reflect any radiated heat that is trying to escape, back into the coil. The heater (large ceramic power resistor) sits directly centered within the coil.

Initially I was using fiberglass insulation, but as of this weekend, I have placed it within an air tight ABS enclosure, and foam insulated it to about 1.25" thickness all the way around. This should get me pretty close to a zero load condition when not applying any heat with the power resistor (no static losses).

Of course this is just a dummy load, and only meant to characterize the heat load capabilities of the AC-2 Chiller.

Sorry for not posting any pictures, but I left my camera at home, and the shop camera seems to have disappeared. First thing tomorrow I'll snap some pics of the test load as it stands right now.

Good news is that I got everything done on my to-do list, so in the next couple of days I should be testing again. This time with the following charge:

4 oz R-600
4 oz R-290
85 psi R-170
85 psi R-14
12 psi Argon

This is an ozone friendly mix.

Good :)
Hope you enjoy the r290 ;)
I wish I could pass you a cylinder of Ethylene (ethene) r1150 though. I think you'd love it.

Quote:

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I wish I could pass you a cylinder of Ethylene (ethene) r1150 though. I think you'd love it.

---

Can't you just email it to me? :D

It would be nice to try at some point, since R-14 is so darn expensive, and it is a green house gas. Although if it could be bought in the small quantities required for my unit it wouldn't be to unreasonable. Too bad the gas suppliers don't offer a system like the fill your own drinking water dispensers you see in front of the grocery stores.

Well r1150 is easy to get, and you can get small quantities. I have 11lb and its going to last a while me thinks.

mytek:
local airgas carries it, not sure on tank $ or regulator, but for ME at least they carried 10, 35 and 200 cubic foot tanks. 10 was 180$, 35 cuft was 225$, and 200cuft was 310$...

ethylene regulator runs around 750$, so i think people just use hydrogen regulators with a cga350 adapter (feel free to correct me here).

Regards

Sorry I haven't been updating for a while, but I got sick last week, and it took a bit longer to run some of the tests.

The good news is that I was able to run several different charge combinations. The bad news is that the hydrocarbon liquids (R600 & R290) don't seem to play very well together in my autocascade. I tried using just the R290 as my lower stage refrigerant, but it just wasn't getting the first stage cold enough to do much condensing of the next refrigerant in the chain (R170). After nearly an hour, the first phase separator was only running at +10.4C. So I added R600 a 1/2 an ounce at a time. This did get things running better, but not anywhere near as good as using HCFC's for the liquids. Also I started seeing pressure and temperature oscillations, plus it wouldn't hold a load worth a darn.

After trying 3 different HC tests, I decided to give up on this for a while, and instead switched back to using R123 as my first liquid, but substituted R410a as my 2nd liquid (R22 HFC replacement). This gave me much better performance and stability, and nearly matched my R123/R22 charge results. The only problem is that I got c_ocky and added 5 psi more Argon this time, which didn't buy me anything besides higher pressures and slightly warmer temperatures, although I was able to load it up to 200 watts without the evap return going to hell (except the pressures were getting very high just before I shut down 70/365, middle of evap = -89C).

I will have to do some more tests with different ratios of the R123 and R410a, so as to tweak it in for the best results. This combination is better then using R22, since the GWP and ODP are much lower (virtually non-existent). Actually I really don't understand why R123 is to be phased out in 2015. It really is a very good refrigerant, and has an extremely low atmospheric lifetime as well. Anyway getting rid of R22 will allow new systems to be built based upon this design up to 2015.

Now if only small amounts of R123 could be purchased :rolleyes:

Buffer Valve Results:

This worked very well indeed. I did tweak it up a bit higher to buffer at 370 psi on the discharge. Below you can actually see it buffering when I warm started the system. It did this quite a few times (just over 20 times), but after 15 minutes the pressures dropped significantly, and the buffer valve no longer needed to open.