Engine Refrigeration (Supplementary) USCG Question #609 (Set 9)

Referring the illustrated psychrometric chart, suppose during the cooling season that air passes over a cooling coil with a mean surface temperature above the dew point temperature, and this results in sensible heat loss with no change in moisture content. What statement represents the direction of the air conditioning process line? GS-RA-22 Illustration GS-RA-22: the U.S. Coast Guard has not released this illustration.

Official USCG Answer & Rule Citation

Correct Answer: Option B — The air conditioning process line is horizontal with the coil outlet to the left of the coil inlet.

Sensible cooling without dehumidification occurs when coil surface temperatures remain above the entering air dew point. On a psychrometric chart, this pure sensible heat loss moves the operational state horizontally to the left toward lower dry-bulb temperatures.

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