The introduction of outside air to the air conditioning system is 90°F with a relative humidity of 60%. The air has been conditioned to 70°F with a relative humidity of 80%. Using the psychrometric chart, shown in the illustration, determine the quantity of moisture removed from one pound of the conditioned air. Illustration GS-RA-22

Illustration GS-RA-22: the U.S. Coast Guard has not released this illustration.

Question

The introduction of outside air to the air conditioning system is 90&deg;F with a relative humidity of 60%. The air has been conditioned to 70&deg;F with a relative humidity of 80%. Using the psychrometric chart, shown in the illustration, determine the quantity of moisture removed from one pound of the conditioned air. Illustration GS-RA-22

Illustration GS-RA-22: the U.S. Coast Guard has not released this illustration.

Accepted Answer

Option C: 40 grains. Psychrometric analysis of entering versus conditioned air utilizes absolute humidity values expressed in grains of moisture per pound of dry air. Subtracting the specific humidity of the conditioned air from the outside air yields a moisture removal rate of 40 grains.