View Full Version : small cascade hx
gkiing
03-28-2005, 11:30 PM
I need to make a small cascade hx for my upcoming gpu cascade (5000btu rotary/1/4hp hermetic), and I was thinking of trying either 1/8" inside 3/8" (so I can coil it really tight) about 15' or one of those corrugated copper pipes (1/2"diameter, 12"long) inside a 3/4" pipe. I remember chilly1 trying the latter on a 1/7hp cascade with some good results.
chilly1
03-29-2005, 01:21 AM
3/16 inside the 3/8
gkiing
03-29-2005, 08:23 AM
Allright, I'll give it a try. Is it possible to use the inside coil as the high stage evaporator, because then all the cooling would be in direct contact with the condensing 2nd stage gas intstead of taking in heat from the insulation.
hatemi
03-29-2005, 08:37 AM
Or 1/4 tube wrapped around 28mm tube and everything stuffed inside of 42mm tube. domensions of the hx would be 42mm x ~50cm. and you can easily get 5m of 1/4 tube to fit there.
gclg2000
03-29-2005, 08:47 AM
Ya do the 3/16 inside 3/8. You can easily connect/pinch off your cap tube or TEV (most likely) on your rotary 1st stage to the 3/8" entrance of the HX and run that 3/8 exit (from HX) back to suction on your first stage. Use some 3/8 to 1/4 and 1/4 to 3/16 bell reducer's, i've personally found these make a nice flat connect that you can silver solder easily. Makes it so you don't have to pinch it off and make it look ugly, and then you don'thave to use alot of silver solder either.
Hope this makes sense, its what has worked best for me.
gkiing
03-29-2005, 09:18 AM
Ya do the 3/16 inside 3/8. You can easily connect/pinch off your cap tube or TEV (most likely) on your rotary 1st stage to the 3/8" entrance of the HX and run that 3/8 exit (from HX) back to suction on your first stage. Use some 3/8 to 1/4 and 1/4 to 3/16 bell reducer's, i've personally found these make a nice flat connect that you can silver solder easily. Makes it so you don't have to pinch it off and make it look ugly, and then you don'thave to use alot of silver solder either.
Hope this makes sense, its what has worked best for me.
I'm using captube due to a lack of funds. I'm planning to use the inside coil of 3/16" as the evaporator; I looked at the 3/16 inside 3/8 and there seemed to be about the same amount of space on the inside, so I don't think it will be too restrictive. By using the inside coil as the evap I think it'l greatly reduce the losses through the insulation since the only immediate thing to cool will be the 2nd stage gas :)