The Stovebolt Site Forums The Shop Area The Tool Chest Cooling Compressed air...

Greetings...

OK, so I am going to design a 3/4" copper compressed air manifold for my shop in preparation for both a blasting cabinet for smaller parts and a pressurized system for outdoor blasting.

Regarding expansive cooling for moisture seperation, I am thinking of making a 8' long zig-zag type setup in which a 3/4" line starts close to the ceiling with a slight pitch, then 180 degrees to reverse direction with an immediate increase to 1" copper for 8', another 180 degrees to reverse direction and one more increase to 1-1/2" for another 8'...and then a "T" with a trap and drain and return to 3/4" for the rest of the piping system.

The whole concept is essentially 2 increases in volume for 2 seperate expansive cooling sequences. Is my thinking on the right track? Is it overkill? Will 1 increase in pipe diameter be sufficient for adequate expansive cooling?

Any inputs would be appreciated?!!

Thanks...

Burgie

Yes you are thinking correct. Reduce the velocity of air.

Approx 50% of input power to compressor is wasted as heat.

BUT why not take advantage of that heat you removed from air AND that dang water and use it to heat something else? Would take a little more plumbing ie heat exchanger tees and larger pipe say 1" and run water between outside of 3/4 and the inside of 1". Use to heat hot water for shop and or house (sink shower etc in summer) and for shop heat (mmm in floor heat) in winter.

Grainger has heat exchangers designed for this but are probably oversize and over BUDGET for you.

Dan Bentler

You can't get expansive cooling without dropping the pressure. When you have a tank or compressor supplying the air and go from a smaller pipe to a larger pipe the air doesn't expand, the air supply simply pushes in more air to maintain the pressure. The efficiency of cooling the air with this type of setup is in part determined by the ratio of surface area of the pipe to the volume of air in the pipe. The smaller pipe will have a larger surface area per unit of air volume and therefore will cool more efficiently. So you'll cool the air better by not increasing the pipe diameter. Then add one vertical section of a larger diameter at the end to slow the linear velocity and drop out any water droplets.

Agree he is not doing expansive cooling.

I beg to differ regarding pipe size
I agree the volume to circumferance is not favorable with larger pipe ie vol goes up by the square of radius change
BUT
the velocity is inversely proportional to the area so what you lose on one hand you gain on the other. With larger pipe size you get slower velocity thus longer contact time
AND more surface area.

He would be much better off by using multi tube heat exchanger water cooled than with single tube but there just may be a cost factor involved which I tried to keep in mind.

dan Bentler

Cost is certainly a factor...but I am trying to understand the physics of the process to best design a system for maximum moisture removal from the compressed air...

Sorry, I didn't state what I meant very well. I should have said a longer run of smaller pipe will cool better than a shorter run of larger pipe and both will cost about the same.

I was going to try the outside coil from a heat pump I replaced but had to leave it when I moved and didn't have enough room on the truck.

Any refrigeration equipment heat exchangers work well with compressed air.

Matching refer pump HP to compressor HP should be real close.

Could go to wrecking yard get 2 or 3 condensors connect in parallel.

OR go to outfit scrapping HVAC stuff and get freon to water coil and preheat house hot water and or shop with yumm in floor heat.

Dan Bentler