On an R-22 cooling unit, if the suction pressure is 32.8 psig and the leaving evaporator temperature is 30 degrees, what is the system superheat?

To determine the system superheat, it is important to understand the relationship between the suction pressure, evaporator temperature, and superheat itself. Superheat is the difference between the actual temperature of the refrigerant gas as it leaves the evaporator and its corresponding saturation temperature at the suction pressure.

In this case, the suction pressure of 32.8 psig corresponds to a specific saturation temperature for R-22. By consulting R-22 refrigerant property tables or using a pressure-temperature conversion chart, we can find that at 32.8 psig, the saturation temperature is approximately 30 degrees Fahrenheit.

Next, we look at the evaporator leaving temperature given in the question, which is also 30 degrees Fahrenheit. To find the superheat, we subtract the saturation temperature from the actual leaving evaporator temperature. Given that both the saturation temperature and leaving temperature match at 30 degrees, the superheat calculation results in:

Superheat = Leaving evaporator temperature - Saturation temperature Superheat = 30 degrees - 30 degrees = 0 degrees.

However, this does not correspond to the answer options provided. The correct way to find the superheat is to determine the gas temperature after the evaporator based on the operational condition, which