USCG Exam PracticeThermodynamics and heat exchangers
Non-condensable gases accumulating in a main condenser will have which of the following effects on plant operation?
- A. They increase the latent heat of vaporization of the exhaust steam, improving heat transfer.
- ✓ They blanket the tubes, raise back-pressure, and reduce heat transfer, lowering plant efficiency.Correct
- C. They lower condenser pressure below design vacuum, allowing the turbine to produce more work.
- D. They contaminate the condensate with chlorides, causing boiler scale.
Why B is correct
DOE-HDBK-1018 Vol.1 §2-3 states that non-condensable gases must be continuously removed by an air ejector or vacuum pump, or they blanket the tubes, raise back-pressure, and reduce heat transfer. Chloride contamination results from seawater leaks, not non-condensable gases.
Cited:DOE-HDBK-1018 Vol.1 §2-3