Compressed dry air

(not verified)
Posted in: , on 15. Jul. 2003 - 06:16

I am trying to find ways to conserve energy in a plant. Compressed air is dryed with desiccant dryers to about -40 degrees F for use in pneumatic actuators and air pulse for dust collectors. Although the -40 F is the requirement based on manufacturer's literature, can I reduce the dryness level considering that the lowest temperature that the dry air will be exposed to is about 72F?


Bobby Cruz

Dennis Hauch - Freeport, TX, USA
(not verified)

Compressed Air Dp

Posted on 17. Jul. 2003 - 10:39

Bobby Cruz,

When compressed air at 100 PSIG is let down to atmospheric pressure through a nozzle, even a pulse clean nozzle found in your typical dust collector, the pressure ratio is such that sonic velocity will occur in the nozzle throat. A simple expression based on the ratio of specific heats for air says that temperature in the throat area of the nozzle will fall to approximately minus 16 degrees F when it is flowing.

From the above we can say that compressed air having a DP of minus 20 degrees F and stored at 72 degrees F should not pose a condensation problem inside the nozzle itself. There could still be a problem, however, and it’s on the outside surface of the nozzle body. If the ambient air surrounding the nozzle has a DP above minus 16 degrees F, and it most assuredly will, moisture will condense on the nozzle surface. It may be necessary then to insulate the nozzle to prevent exterior condensation.


Dennis Hauch

(not verified)

Re: Compressed Dry Air

Posted on 31. Jul. 2003 - 05:33


Thanks for the reply.