Question 479General Subjects - Assistant Engineer

70% to pass

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

A19%

B27%

C55%

D70%

AI Explanation

The correct answer is B) 27%. The reasoning is as follows: 1. The air starts at a dry bulb temperature of 60°F and a relative humidity of 52%. 2. As the air passes over the heating coil, it undergoes a sensible heat gain, resulting in the off-coil temperature of 80°F. 3. Using the psychrometric chart, the relative humidity at 80°F with the same moisture content (constant humidity ratio) as the initial condition of 60°F and 52% relative humidity is 27%. The other options are incorrect because: A) 19% is too low, C) 55% is too high, and D) 70% is also too high for the given conditions.