Question 224General Subjects - 1st Asst/Chief70% 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
AI Explanation
The correct answer is B) 27%.
To arrive at this answer, we need to understand how the psychrometric chart works. When air passes over a heating coil, its dry-bulb temperature increases, but its moisture content (and therefore its relative humidity) decreases. By tracing the 60°F, 52% RH point on the psychrometric chart to the 80°F point, we can see that the relative humidity at the off-coil temperature is 27%.
The other options are incorrect because:
A) 19% is too low for the given conditions.
C) 55% is too high, as the relative humidity decreases when the air is heated.
D) 70% is also too high for the given conditions.
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