cascade 1

I often get pms about my first unit so i thought i would put it into a thread here

cascade 2 http://www.xtremesystems.org/forums/...d.php?t=105549

cascade 3 http://www.xtremesystems.org/forums/...d.php?t=117279

cascade 4 http://www.xtremesystems.org/forums/...d.php?t=126920

cascade 5 http://www.xtremesystems.org/forums/...d.php?t=152749

cascade 6 http://www.xtremesystems.org/FORUMS/...d.php?t=184106

This will bring my cascades builds upto date here

now before you jump on me remember this was my first

so there are some mistakes

the most important would be that i did not use any safety devices

this i changed with all my cascades since

and would suggest that all cascades have the correct safety controls in place

here is a pic of the missing parts

it would be useful for the first time builder if you could spot where to place these items

http://www.net7.info/1/cascade3/build/DSC00169.jpg

I won’t be going after uber temps with this one but you never no

I have pulled together some old parts I had lol what’s left of my first vapo
And some new stuff that I will be able to use again for the next project

Here are the parts so far:

High stage:

Danfoss NL11f(SC18 if the NL dont cut it) 402a, hx 12 feet of 1/2 copper with a 1/4 pipe in it (that’s the large coil), 1/4 copper pipe for most of runs on this stage, filter dryer with read point, cap tube (still to work out), sight glass, vapo condenser with pre cooling coil

Low side:

Danfoss NL11f co2/402a
Danfoss oil separator or I might have ago at a home made one
Hand valve oil return
High pressure cut off valve
Control unit something along the lines of this unit EWPC-901 I may have something else coming, cap tube length undecided as yet

My choices of gases is based on the fact that I already have the 402a and I can get the co2 cheap. r23 will be In the next one

Mocked up the high side today just need to fill the compressor with oil attach the cap tube and braze it up

Some picks

http://benchtec.co.uk/1/casscade/1stage/1.jpg

http://benchtec.co.uk/1/casscade/1stage/IMG_0003.jpg

http://benchtec.co.uk/1/casscade/1stage/IMG_0011.jpg

http://benchtec.co.uk/1/casscade/1stage/IMG_0014.jpg

http://benchtec.co.uk/1/casscade/1stage/IMG_0018.jpg

http://benchtec.co.uk/1/casscade/1stage/hx1.jpg

http://benchtec.co.uk/1/casscade/2stage/IMG_0002.jpg

http://benchtec.co.uk/1/casscade/2stage/IMG_0001.jpg

The oil separator was one I had left from some bits and bobs sent over by sandman so it was not made by me but should do the job

As oil builds up in the separator I have to open the red valve and let the oil return to the suction line and then back into the compressor

There is still to be a pressure cut off to go in this section just before
The gas goes into the hx


http://benchtec.co.uk/1/casscade/2stage/IMG_0004.jpg

http://benchtec.co.uk/1/casscade/working/IMG_0002.jpg

http://benchtec.co.uk/1/casscade/working/IMG_0008.jpg

http://benchtec.co.uk/1/casscade/working/IMG_0016.jpg

http://benchtec.co.uk/1/casscade/working/IMG_0023.jpg

Ah I remember this. Was very neatly and nicely piped. A very well done job with good results, albeit a small condenser. I liked your HX stand, and though a spiral is even to curve around our refrigerant bottles, I've always found trombones are more space efficienct.

for me this one was that eureka moment when it worked for the first time

i remember how good that felt

What was the original problem?

Looks amazing, nice and clean :slobber:
Hope I can do something like this.

Nice first cascade baz.

I see you use the accumulator on the suction line on your cascades, how beneficial is it mate?

I Like the bracket for the suction line and HX also.

Plenty of changes since then, but what's never changed is my having to wipe drool off my keyboard every time I see your handiwork. :toast:

Quote:

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Originally Posted by n00b 0f l337

What was the original problem?

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at the time i could not get it to hold a load

wish i still had it i am sure i could have made it work now

Quote:

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Originally Posted by 4Qman

Nice first cascade baz.

I see you use the accumulator on the suction line on your cascades, how beneficial is it mate?

I Like the bracket for the suction line and HX also.

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tbh i dont know if accumulator help or not

with my current cascade i removed it and its just fine

Did you ever insulate the HX? Simply having it in the open applies a 100++ watt load to the unit. More then enough to crash your HX temps.
I think with 2nd stage you dont have to worry about leak floodback as much. An accumulator can help though, and I wouldn't go without one in most situations, especially when its all insulated and if you run it at idle.

Nice to see your first cascade baz, with the exception of the condensor this is a perfect little system :)

With an accumulator on a cascade second stage - it could have helped on this as you were using a lower pressure refrigerant with the CO2, the lower pressure refrigerant would have probably remained liquid much along the suction due to the lower temperature of the evaporator from the CO2.

If you're just using a high pressure refringerant in the second stage then it won't do anything as the refrigerant will build up a lot of superheat just from suction line insulation as it's at a much lower temperature. Also it's hard to get the physical amount of second stage refrigerant in the system for floodback due to static pressure and startup shock being the main limitations.

Tom

Oh yes, that and your condenser was probably undersized for even the load of the iced hx. Wrappy the capillary line probably could have helped as well.

Baz thank you for posting this. The only NF11 Cascade i know of.

Can't wait to get mine on the go.

Ta

Heh, I'm thinking of doing a NF11fx cascade, Ive got the parts sitting, so its nice to look at Bazx work as well. 60hz tho gives me a bit more power ;)

Nice one baz looks like the NF11fx is very good for a small cascade, these temps will be a bit better with some insulation on so the -100 mark is not that far away and using such small compressors which run nice and quite, would be interested to know how well this unit deals with loads.

I think with r23 or r508a/b you can't expect -100C. Not without ethylene or the like. (R14 in commercial uses)

Would be so COOL to have a quite, 24/7 cascade that only consumes 400 -500 Watt :D

I wonder how much power our second++ stages consume, power consumption is relative to that of the evaporation temperature, so with the low boiling point refrigerants it might be quite low unless your running a high compression ratio.

if i were able to spend an afternoon with this unit again

i would of changed the

(first stage)

condencer/cap tube, size and length/first stage gas to R507/gauge (high)

(second stage)

safty valve, cut off switch, gas to R23, oil sep, cap tube and length for the evap

and insulated the lot

I actually think the condenser might have been enough, maybe, at least with those desuperheaters. The fact that your HX iced with just a desuperheater coil on 2nd, and the load of the air, you could probably have gotten to take a GPU or the like after insulating.
I still think its a great example of excellent pipework.

Quote:

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Originally Posted by n00b 0f l337

I wonder how much power our second++ stages consume, power consumption is relative to that of the evaporation temperature, so with the low boiling point refrigerants it might be quite low unless your running a high compression ratio.

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I think you'd work out the compression power needed in a perfect cycle (isen = 1) and then divide this power by the calculated isentropic efficiency of the compressor at similar suction discharge pressures from the compressors datasheet - should get you very ball park although it will be a bit off from the different refrigerant.

With CO2 below tripple point i have no idea how you'd do it...

Compression ratio isn't the decider on power consumption, you could have the same compression ratio with two different suction/discharge pressures pairs, the power consumption could be vastly different with the same compression ratio. You could have 1PSIa suction and 200PSIa discharge, 200:1, but it won't use much power because it's not doing much.

Unless the compressors are large it doesn't matter anyway as long as you don't pay the bills and can power the thing - the shell cooling takes out most of the compressor input power anyway.

Sorry for off topic Baz :)

Tom