cascade 1

[bazx]

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

[n00b 0f l337]

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.

[SoddemFX]

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.

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