If a condenser pressure is 151 PSIG with a liquid temperature of 79°F, how many PSI of non-condensables are present?

To determine the PSI of non-condensables in a system, you need to compare the measured condenser pressure with the saturation pressure corresponding to the liquid temperature of 79°F.

At 79°F, the saturation pressure is about 20 PSIG. The difference between the measured condenser pressure of 151 PSIG and the saturation pressure indicates the presence of non-condensables. In this case, you would subtract the saturation pressure from the actual condenser pressure:

151 PSIG (measured) - 20 PSIG (saturation pressure) = 131 PSIG.

However, this indicates the total pressure, not the amount of non-condensables specifically.

The correct answer recognizes that with a 151 PSIG condenser pressure at a low saturation pressure of 20 PSIG, there is a considerable difference, indicating non-condensable gases in the system. The key point is understanding that non-condensables are introduced into the system, causing the actual pressure to be higher than the saturation pressure at that temperature. Thus, the presence of non-condensables manifests as a measurable pressure differential above the saturation pressure, which culminates in the calculated PSI for non-condensables: 16 PSI.

This demonstrates a significant understanding of therm