USCG Exam PracticeBoiler and steam propulsion fundamentals
Superheated steam is preferred over saturated steam for use in turbines primarily because superheated steam does which of the following?
- A. It carries suspended moisture droplets that lubricate the turbine blade surfaces
- B. It condenses more rapidly in the turbine, releasing additional latent heat to drive the blades
- ✓ It contains no liquid and will not condense and erode the turbine blades during expansionCorrect
- D. It has a lower enthalpy than saturated steam, reducing thermal stress on the turbine casing
Why C is correct
Superheated steam has been heated above its saturation temperature and contains no liquid. This is desirable for turbines because wet steam — steam containing suspended moisture — will condense during expansion and the resulting water droplets erode the turbine blades. Superheated steam also carries higher enthalpy, not lower, than saturated steam at the same pressure. (DOE-HDBK-1012 §1-2; NAVEDTRA 14104 §3-1)