Boiler and Steam Systems Flashcards
7 cards from real CEM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Boiler and Steam Systems flashcards as text
What does boiler 'turndown ratio' describe?
Answer: The ratio of maximum to minimum firing rate while maintaining stable operation
Turndown ratio is the range from maximum to minimum firing rate at which a burner can operate stably, affecting part-load efficiency.
Which condition best describes 'wet steam' in a steam distribution system?
Answer: Steam containing entrained liquid water droplets below 100% quality
Wet steam has a dryness fraction below 1.0, meaning it carries entrained liquid droplets that reduce heat transfer efficiency.
A steam trap that fails open causes which primary energy problem?
Answer: Live steam blow-through resulting in direct energy loss
A failed-open steam trap allows live steam to pass through continuously, wasting the latent heat contained in that steam.
What is the primary purpose of a deaerator in a boiler feedwater system?
Answer: To remove dissolved oxygen and carbon dioxide from feedwater
Deaerators use steam stripping and mechanical action to remove corrosive dissolved gases, particularly O₂ and CO₂, protecting boiler internals.
Which heat recovery device captures energy from boiler flue gas to preheat combustion air?
Answer: Air preheater (recuperator)
An air preheater (recuperator) transfers heat from hot flue gases to incoming combustion air, improving combustion efficiency.
Increasing excess air beyond the optimal level in a boiler burner primarily causes:
Answer: Increased stack losses due to sensible heat carried away by excess air
Excess air above the optimal level carries additional sensible heat out the stack, reducing thermal efficiency even though combustion is complete.
What is the significance of the 'critical pressure' of steam for energy managers?
Answer: The pressure above which liquid and vapor phases become indistinguishable (374°C, 22.1 MPa for water)
At the critical point (22.1 MPa, 374°C for water), the distinction between liquid and vapor disappears, which is relevant for supercritical power plant design.