Autocascade Drawings

[chilly1]

Just a couple ideas.. Post your autocascade drawings here...

[bh2k]

Yea, I think this item is in my future if I can just figure out how I'm making a phase separator. Chilly1 what is the thing that connects the capilary tube and the condenser? is that a HX of some kind? If so, could it just be an air cooled coil of pipes or would I have to use a normal condeser for ir? And the exit line from the oil separator to the condenser does it really connect in the middle of the condser? I'm having a bit of trouble determining the overall flow the refridgerent, think you could help me out?

[chilly1]

ON the bottom drawing...the 2 phase refrigerant comes out of the compressor and into an air coil where it is desuperheated, then it goes to the oilseperator where the oil is taken out and returned to the compressor, then the refrigerant goes through the filter. Then to the mid point of the parallel condenser/separator where the lower pressure gas condenses and the high pressure gas rises, the low pressure liquid exits the bottom of the condenser and travels through the capillary tube to the interstage heat exchanger(light blue) and evaporates and returns to the suctionline,back to the condenser and the high pressure gas exits the condenser and goes to the HX on the suction line where it rejects some heat into the suction line then to the HX(purple), the high pressure gas condenses to a liquid in the hx and exits (darkblue) through the capillary tube to the block, were it evaporates cooling the load and is pressure limited by the use of the EPR (Evaporator Pressure Regulator) valve then enters the suction line where it mixes with the lower pressure gas, the gas blend in the suction line is superheated by the suctionline heatexchanger and then enters the compressor

[bh2k]

I see. And how does the charge work for that? Do I just charge both gases like 1/2 and 1/2 or is there a special way to charge the system?

[chilly1]

My first approxamation to develpo a method of charging would be to charge the lower pressure gas for twice the superheat you want at the compressor like 14 to 18 then add a little of the second stage gas and monitor the effects, then I would add or subract either the low or high pressure gass depending upon the effects and I would make guesses about its operation until I developed an understanding of how each gas affects the operation of the system as a whole. We have a few common points here that you will have to monitor this will work as two independant systems but they will be linked by pressure and temperature..

[bh2k]

Okay, I got it, now how do I go out separating the gasses like if I want to remove some of the second and keep the first charge? Also how do I do my accesses since there are 2 stages there should be 4 access ports if I'm not mistaken.

[chilly1]

Actually for tuninfg you need four acceass ports one on the scuction line one on the compressor discharge one on the second stage liquid line and one on the first stage liquid line..

[gkiing]

I wouldnt want to remove gas on the second stage liquid line wouldnt that be where it is under the most pressure (eg co2 @ 300psi?). Wouldnt it be easier to remove the second stage gas from after the condenser/phase-separator?

If you wanted to remove gas from the liquid line wouldnt you want one of those liquid charge adapters (you use it when charging-- charge with the cylinder upside down but the liquid turns to gas before it enters the charging line)

[gkiing]

Forgot to add, are there any safety devices in that diagram? What is the function of the EPR? To maintain a pressure difference between the evaporator and the suction line for the first stage gas?

[bh2k]

Think someone could point out on the drawing where exactly I'm going to want to put all of my access ports? I'm going to the ac shop today to get the parts for my phase separator, oil sep and hx so I need a bit of advice before I start building.

[chilly1]

Another simpler one..

[chilly1]

[gkiing]

Whoa, the second one is like an autocascading evaporator! Is the idea to evaporate the first stage gas in the suction line just after the evap, and have the second stage capillary tube wrapped around that area, so that it will condense and then flow into the evaporator? In the first drawing is the oil returned by having it mix back with the first stage refrigerant and return to the compressor?

great designs, love the xtremesystems on it too

[chilly1]

These are just ideas not tested designs. The ides in teh third rawing is to use the phase seperator as an oil seperator as well and the oil returns with th efirst stage refrigerant.
The last drawing also has the oil return with the first stage gas. There are a few problems to work out i the top of the block, like oil drain back and Suction desupreheating causing a rise in suction discharge pressure. The suction line would be the HX but there is an issue of running the second stage return gas through the first stage evaporator. There may need to be a three layer piping system.

[sharp]

Ok this is fast and ugly,what is wrong with it??

[m0nk33y]

good luck tuning it to get the c02 to condense

[gkiing]

Originally Posted by m0nk33y

good luck tuning it to get the c02 to condense

The co2 would not condense in the condenser right after the compressor discharge. It would condense in the heat exchanger later on.

The diagram looks fine to me but you would also need a filter drier in the liquid co2 line or right after the compressor discharge where it can filter it all. It would also be good to put a high pressure cutoff between the high and low sides (where their gas) set to open if pressure reaches > 400psi. That will protect you from a rupture.

[kayl]

[quote=gkiing]
The diagram looks fine to me but you would also need a filter drier in the liquid co2 line or right after the compressor discharge where it can filter it all. QUOTE]

he does have one on the co2 line
can we use say a suction line drier for this on the discharge of the compressor like gkiing saud and then remove the other driers from the system?

[gkiing]

[quote=kayl]

Originally Posted by gkiing

The diagram looks fine to me but you would also need a filter drier in the liquid co2 line or right after the compressor discharge where it can filter it all. QUOTE]

he does have one on the co2 line
can we use say a suction line drier for this on the discharge of the compressor like gkiing saud and then remove the other driers from the system?

yeah I just realized that he did

In chilly1's original autocascade drawings he had a drier placed after the desuperheater and oil separator (comp discharge --> desuperheater --> oil sep --> drier).

[m0nk33y]

i was meaning in the phase separator. also if you plan on condensing c02, at lets say -20c, you need approximatelly 20 bars, r-290 evaporates at 58c at 20 bars. how would you condense c02 at -20 c when r-290 at 20 bars doesn't even evaporates at -20c? am i wrong?? please correct

[gkiing]

Originally Posted by m0nk33y

i was meaning in the phase separator. also if you plan on condensing c02, at lets say -20c, you need approximatelly 20 bars, r-290 evaporates at 58c at 20 bars. how would you condense c02 at -20 c when r-290 at 20 bars doesn't even evaporates at -20c? am i wrong?? please correct

The r290 doesnt evaporator at 20 bars, it evaporates at 0bar or close to it. A phase-change system has a high side (high pressure) and a low side (low pressure). The pressure difference is maintained by a metering device (capillary tube). This way the refrigerant can condense at a high pressure (for example 125psig for r290) and evaporate at a low pressure (Opsig). When the first stage refrigerant has condensed the second stage (co2) is still gas. The first stage refrigerant travels through the metering device to the heat exchanger, where it evaporates at a pressure around 0psig (-40). The co2 is still under high pressure and is able to condense at -40 at < 200psig.

Perhaps you aren't grasping the way an autocascade works, you should have a look at one of the many autocascade threads floating about.

[m0nk33y]

oops should have looked at the diagram, thx for clarifying. thus the term " am i wrong?please correct"

[RaVeN155]

I like third pic and I will propably make my unit that way And question, using cpev or other XV on HX is good idea? I think that it is a better way than using it on evap but maybe its not, so i just ask . And second question, is using 2 cpev possible? Those are "constant pressure..." so maybe it makes problems? dunno

[chilly1]

Originally Posted by RaVeN155

I like third pic and I will propably make my unit that way And question, using cpev or other XV on HX is good idea? I think that it is a better way than using it on evap but maybe its not, so i just ask . And second question, is using 2 cpev possible? Those are "constant pressure..." so maybe it makes problems? dunno

MAybe?? totally untried these have never been build these are discussion and proposed ideas only.

[gkiing]

Originally Posted by chilly1

MAybe?? totally untried these have never been build these are discussion and proposed ideas only.

Well experimentation is the best way to find out