Vapour Power Cycle In Engineering Thermodynamics by PK Nag (Chapter 12)

A: Governing principle: Mass transfer can control metal loss when protective films are unstable. High velocity strips magnetite faster than it reforms, even with low oxygen, matching the observed pattern. Option D catches people who see low pH and stop there, dropping the velocity term that actually sets the rate.

A: Governing principle: Regeneration trades hardware for cycle efficiency and chemistry control. Closed heaters boost efficiency without direct mixing, keeping oxygen and contaminants out of the feedwater. Option B tempts engineers from smaller plants where simplicity rules, but it breaks chemistry control at this scale.

A: Governing principle: Non-condensables raise partial pressure without changing cooling water duty. Normal CW conditions with pressure rise point to air leakage rather than heat transfer loss. Option B traps those who default to fouling, ignoring that fouling tracks CW temperature rise, which isn't present.

A: Governing principle: Safeguards act on specific pressure directions and magnitudes. A vacuum breaker protects against external pressure collapse, not internal overpressure events. Option A snares engineers who know why breakers exist, then forget to flip the pressure sign.

A: Governing principle: Safety functions are validated as a whole, not as isolated parts. Slower actuation can defeat overspeed trips even if steady control looks fine. Option D catches people who frame everything as heat rate, missing the protection layer entirely.

A: Governing principle: Condensate quality and recovery govern condenser selection at scale. Surface designs keep steam and cooling water separate, cutting make-up demand. Option C hooks engineers who remember non-condensables issues, then ignore water balance.

A: Governing principle: Chlorides plus stress drive specific cracking modes. LP exhausts run cool enough to rule out creep, leaving SCC as the consistent match. Option D tempts those who focus on wetness alone, ignoring the crack morphology driver.

A: Governing principle: Cavitation links suction conditions to vibration and pressure instability. Low NPSH fits all observed symptoms in a feedwater service. Option B traps people who see vibration and stop, dropping the suction pressure evidence.

A: Governing principle: Dynamic interactions matter during trips, not just steady load. Weaker vacuum alters transient torque balance, loading overspeed protection beyond its assumed envelope. Option B snares those who reason from steady-state curves and ignore trip dynamics.