Referring to the illustrated psychrometric chart, suppose air at a dry-bulb temperature of 60F and a relative humidity of 52% passes over a heating coil, resulting in sensible heat gain, and the off-coil temperature is now 80F. What is off-coil relative humidity? GS-RA-22

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

Question

Referring to the illustrated psychrometric chart, suppose air at a dry-bulb temperature of 60F and a relative humidity of 52% passes over a heating coil, resulting in sensible heat gain, and the off-coil temperature is now 80F. What is off-coil relative humidity? GS-RA-22

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

Accepted Answer

Option B: 27%. Sensible heating increases dry-bulb temperature while keeping the moisture content constant. Moving horizontally to the right on the psychrometric chart from 60F/52% RH to 80F dry-bulb results in a lower relative humidity. The new intersection point on the chart indicates the off-coil relative humidity is approximately 27%.