At a pressure of 18.1 inches Hg vacuum, what is the saturation temperature of R-123?

• A. 20.6 °C
• B. 32.0 °C
• C. 10.2 °C
• D. 45.8 °C

Answer: (A)

Verified step by step guidance

1. Understand that the problem gives a pressure in inches of mercury vacuum (in Hg vacuum), which means the pressure is measured below atmospheric pressure. To find the absolute pressure of R-123, you need to convert this vacuum pressure to an absolute pressure scale.
2. Convert the vacuum pressure to absolute pressure using the relation: \(P_{absolute} = P_{atmospheric} - P_{vacuum}\). Here, atmospheric pressure is approximately 29.92 in Hg (standard atmospheric pressure). So, calculate \(P_{absolute} = 29.92 - 18.1\) inches Hg.
3. Convert the absolute pressure from inches of mercury (in Hg) to a more standard unit for refrigerant tables, such as psia (pounds per square inch absolute) or kPa, depending on the units used in the R-123 saturation temperature tables. Use the conversion factor: \$1 \text{ in Hg} = 0.4912 \text{ psi}\( or \)1 \text{ in Hg} = 3.386 \text{ kPa}$.
4. Use the saturation pressure-temperature tables or charts for R-123. Locate the absolute pressure you calculated in the table and find the corresponding saturation temperature. This temperature is the saturation temperature of R-123 at the given vacuum pressure.
5. Compare the temperature you find in the table with the options provided to select the correct saturation temperature.