With an increase in the saturation pressure...

🔍 Key Concepts

• Identify what thermodynamic property line 5 represents on a temperature vs. BTU per pound (heating curve) diagram for water/steam. • Recall how latent heat of vaporization changes with increasing saturation pressure. • Recall how the specific heat of superheated vapor (steam) changes with increasing pressure compared to how much the latent heat changes.

💭 Think About

• First, decide which region of the diagram line 5 falls in: ice heating, water heating, evaporation (latent heat), or vapor (steam) heating. What does the slope of the line in that region represent? • When you go to higher saturation pressures (for example, going from atmospheric pressure to several hundred psia in a boiler), which property changes dramatically: the latent heat between saturated liquid and saturated vapor, or the specific heat of the superheated steam? • Look at the bracket marked III where line 5 appears. Is this energy going into a phase change or just raising the temperature of steam already in the vapor phase?

✅ Before You Answer

• Be sure that line 5 is correctly identified as being in the superheated vapor region (after all liquid has been converted to vapor). • Confirm whether the latent heat of vaporization is shown horizontally (at constant temperature) or as a sloped line; this will help eliminate any option that talks about latent heat for line 5. • Remember that the latent heat changes a lot with pressure, while the specific heat of superheated steam changes relatively little; use this comparison to rule out at least two wrong choices.

With an increase in the saturation pressure of a fluid, the value represented by line "5" on the graph will __________. Illustration SG-0001

represent an increase in the specific heat of the vapor

represent virtually no change in the latent heat of vaporization

represent a decrease in the specific heat of the vapor

represent virtually no change in the specific heat of the vapor

🔍 Key Concepts

💭 Think About

✅ Before You Answer