Aftercooler on Quincy QT-54

[Mesozoic]

Getting a bit closer to setting up my new QT-54 compressor and found a 21,000 BTU, 36 plate count stacked plate cooler with 1/2" FNPT connections sitting on my shelf. Must've been from back in the day when I had an automatic transmission to cool. It is a Long Mfg TruCool M7B cooler. Planning to mount this thing onto my QT-54 as an aftercooler. The tubing connecting the pump to the tank is currently 3/8 ID copper - is there any reason I couldn't just run 3/8" ID aluminum tubing instead of copper?

 

[matt_i]

That's an app I would be concerned about. For 3 reasons. The compressor is producing a spiky pressure wave that should center around 175psi. I wouldn't be surprised if there were 300psi pulses on every piston stroke right there at the exhaust port. I realize the line pressure on a transmission is triple digits but the cooler circuit doesn't run at that pressure...its pretty low-flow.

Also, for a heat exchanger to work efficiently it relies on internal turbulence...the enemy of flow. Perfectly acceptable for a trans cooler because flow is slow to start with.

Last the aluminum loses a lot more ductility when bent than copper in my experience. Not the material I'd be looking to use in a ~200psi system.

 

[Mesozoic]

The cooler itself appears to be similar to what a lot of members on this forum are using. I'm not too worried about it so much as I am about the tubing. I have plumbers coming to finish/trim the air system connections next week, so I could ask them to bend me up the right pieces in Cu to interface with the cooler.

However, I was looking at McMaster-Carr and there's certainly aluminum tubing available for the same purpose and it seems to have a significantly higher pressure handling capacity too. For air rated tubing, 1/2" OD, 0.37" ID, 0.065" wall thickness Al tubing with T6 tempering, we're talking 2400 psi rating @ 72F. For the air rated copper tubing with exactly the same dimensions, the rating goes down to 1400 psi. The Cu is also $80 for 10' coil, whereas the Al is $25. The only drawback I'm seeing using Al is, as you mentioned, ductility loss after bending (Cu can be rebent with annealing), and availability as you will find Cu at any Home Depot. The Al would have to be ordered.

Found this interesting read on Al vs Cu for compressed air applications: https://www.plantengineering.com/ar...iping-makes-sense-for-compressed-air-systems/

 

[Mesozoic]

Well, I'm quite pleased with my setup thus far. I moved the compressor into position in its closet and wired it up, checked all the connections, and fired it up! While it is loud as hell inside the closet, it is literally inaudible inside our house which was the main goal - required some attention to the STC rating of materials between walls.

The aftercooler is doing a pretty good job, making the output air lines to the tank cool enough to touch, while the input to the cooler is scorching hot. I used 1/2" OD aluminum tubing with JIC fittings - no leaks, have a few hours on it and seems to be working well.