Mass crosses the boundary—what analysis framework do you begin with?
Control volume (open system) using continuity and energy balance.
Device says ‘steady state’—what balance term is eliminated?
Time-accumulation (storage) terms drop out.
Before applying SFEE, what is the most important setup step?
Define the control volume and label inlets/outlets with directions and sign convention.
Throttling valve with no heat/work—what key property stays constant?
Enthalpy (h_in ≈ h_out).
Adiabatic nozzle, big velocity increase—what dominates the energy balance?
Enthalpy drop converting to kinetic energy increase.
Adiabatic diffuser, velocity decreases—what increases?
Static pressure/enthalpy (pressure recovery).
Turbine with isentropic efficiency given—what do you compute first?
Isentropic outlet state (s_out,s = s_in), then actual via efficiency.
Given P and T for water—what is the first region check?
Compare T to Tsat(P) to determine compressed/saturated/superheated.
Given P and h for steam—what is the first diagnostic?
Compare h to hf/hg at that P to decide mixture vs superheated/compressed.
Quality x: what is it and when is it valid?
Vapor mass fraction; only valid in saturated mixture region.
Compressed liquid slightly subcooled—what PE approximation is often acceptable?
Use saturated liquid properties at the same temperature.
Ideal gas relations: what is the key condition to justify them?
Gas is far from saturation/critical region and behaves nearly ideally.
Closed system first law: what form is your default starting equation?
ΔU = Q − W (plus KE/PE if relevant).
Adiabatic + reversible: what does that imply about entropy?
Isentropic (Δs = 0).
Adiabatic device shows entropy increase—what does that mean?
Irreversibility; entropy generation > 0.
Cycle thermal efficiency: what is the top-level relationship?
η = W_net / Q_in.
Rankine cycle: what is the best first move?
Label state points and processes on a T–s diagram (pump, boiler, turbine, condenser).
Why is Rankine pump work usually small compared to turbine work?
Liquid specific volume is small, so vΔP work is small.
Brayton cycle: what parameter strongly affects ideal efficiency?
Pressure ratio (and component efficiencies if included).
Regeneration in Brayton: what does it reduce?
Required external heat input (fuel) for a given turbine inlet temperature.
Combined cycle: what is the core benefit mechanism?
Uses gas-turbine exhaust heat to generate additional steam-cycle work.
Otto vs Diesel: what is the key modeling distinction for heat addition?
Otto: constant-volume; Diesel: constant-pressure heat addition.
COP given: what is the first clarification you must make?
Whether COP refers to refrigerator (Q_L/W) or heat pump (Q_H/W).
COP exceeds Carnot COP—what do you check first?
State properties/sign convention and absolute temperatures.
