Given a suction header pressure of 38 PSIG and a suction header temperature of 37°F, how much superheat is found at the outlet of the evaporator?

To determine the amount of superheat at the outlet of the evaporator, it's essential to first understand the relationship between pressure, temperature, and refrigeration cycle efficiency. The superheat is calculated by comparing the temperature of the refrigerant entering the compressor to the saturation temperature corresponding to the suction header pressure.

At a suction header pressure of 38 PSIG, we need to convert this into absolute pressure. The conversion involves adding atmospheric pressure (approximately 14.7 PSIA) to the gauge pressure:

38 PSIG + 14.7 = 52.7 PSIA

Next, we can reference a saturation temperature table for the specific refrigerant being used (common refrigerants include R-134a, R-410A, etc.). For example, assuming R-134a, a pressure of 52.7 PSIA corresponds to a saturation temperature approximately around 25°F.

Now, the actual suction header temperature is given as 37°F. To find the superheat, we subtract the saturation temperature from the actual temperature of the refrigerant at the evaporator outlet:

Superheat = Actual Temperature - Saturation Temperature

Superheat = 37°F - 25°F = 12°F

However, since the options suggest rounding, this