How Can 45-Degree F Air Freeze Water?

Very easily….! If the outside air enters a scrubber at this temperature, the scrubber acts as an evaporative cooler while it cleans the air and lowers the temperature adiabatically. The air becomes saturated with water vapor and freezes causing clogging of the scrubber and reduction of the air flow. How can this happen? Look at the psychrometric chart. The laws of physics are very clear.

The solution to this challenge is equally as clear. Control the outside air so that it always enters the scrubber at a safe temperature. Control the scrubber leaving temperature so that it satisfies the room comfort conditions, especially humidity.

We were recently given the opportunity to help with the design of this special supply air system for an industrial customer who expressed concern about the quality of his outside air. He insisted that a wet scrubber be used to clean the supply air. Other than the addition of the scrubber, the challenge was a normal one: condition 100% outside air (95 F/78 F- summer and 5 F - winter) to 70 degree F and 50-60% RH in the occupied space.

Proper application of the scrubber required a thorough design knowledge of each system component in order to achieve proper results:

a) A Marlo-Stratomizer heated the outside air above the critical inlet temperature

b) An API Ketema (Acme Chiller) controlled the air at a constant temperature leaving the scrubber through a chilled water coil; therefore, achieving dew point control.

c) A Marlo steam reheat coil maintained the room temperature and the humidity within an acceptable range.

We are asked to solve unusual problems on a regular basis. Do you have an environment application in mind that requires a special system?

By:

Paul Coward

7-99