Steam-Cycle Power Generation
Comprehensive university textbook unit covering fundamental principles, governing relationships, and engineering applications of Steam-Cycle Power Generation.
§2.1 Rankine states and thermal conversion
**Core topic:** net cycle work and heat input. **Representative relation:** `eta_R = (w_t - w_p) / q_in`. **Case context:** four-state saturated cycle.
§2.2 Steam turbine expansion and extraction
**Core topic:** enthalpy work and internal efficiency. **Representative relation:** `W_t = m_dot*(h_in-h_out)`. **Case context:** high-pressure turbine with a bleed stream.
§2.3 Condenser duty and backpressure
**Core topic:** heat rejection from wet exhaust. **Representative relation:** `Q_cond = m_dot*(h_in-h_out)`. **Case context:** surface condenser in a humid climate.
§2.4 Feedwater pumps and boiler input
**Core topic:** liquid-pump work and steam-generator duty. **Representative relation:** `w_p ≈ v*(p_out-p_in)`. **Case context:** multistage feedwater train.
§2.5 Reheat and regenerative feedwater heating
**Core topic:** cycle efficiency and moisture management. **Representative relation:** `Q_added = sum(m_dot*delta_h) across heated streams`. **Case context:** one reheat stage with closed feedwater heater.
Step-by-Step Power Plant Engineering Solutions
Three original questions connect calculations, definitions and interpretation. Open each solution to follow the reasoning.
Problem Statement: Take idealized cycle enthalpies of 192 kJ/kg at pump inlet, 202 after pumping, 3450 after the boiler, and 2300 at turbine exit. Turbine work is 1150 kJ/kg, pump work is 10 kJ/kg, and heat supplied is 3248 kJ/kg; ideal thermal efficiency is (1150 − 10)/3248 = **35.10%**. These are a synthetic set of enthalpies, not a verified steam-table operating point.
Worked Engineering Derivation:
**Verification and limitations.** Detailed state selection must satisfy actual pressure and entropy constraints; arbitrary enthalpies cannot validate a real cycle. The result is illustrative and does not replace equipment-specific property data, measurements or professional review.
Problem Statement: With steam flow of 30 kg/s and inlet/outlet enthalpies 3410 and 2550 kJ/kg, an ideal steady turbine power estimate is 30(3410 − 2550) = **25,800 kW**, or 25.8 MW. A real extraction turbine must apply this balance separately to every branch rather than using the full inlet flow across all stages.
Worked Engineering Derivation:
**Verification and limitations.** The estimate excludes mechanical losses, leakage and the small kinetic-energy terms until their significance is checked. The result is illustrative and does not replace equipment-specific property data, measurements or professional review.
Problem Statement: A condenser receives 42 kg/s of wet exhaust at specific enthalpy 2400 kJ/kg and discharges condensate at 220 kJ/kg. Condenser thermal duty is 42(2400 − 220) = **91,560 kW**. This heat must reach a cooling medium, subject to nonzero temperature approach and finite transfer area.
Worked Engineering Derivation:
**Verification and limitations.** A lower condensing temperature may improve ideal cycle output but can increase cooling demand or air-leakage sensitivity. The result is illustrative and does not replace equipment-specific property data, measurements or professional review.
Problem Statement: Using near-incompressible liquid specific volume 0.0011 m³/kg and pressure increase 11 MPa, ideal pump work per kilogram is approximately 0.0011 × 11,000,000 = **12,100 J/kg**, or 12.1 kJ/kg. A 75%-efficient pump requires approximately 16.1 kJ/kg shaft input, excluding other losses.
Worked Engineering Derivation:
**Verification and limitations.** Convert pressure to pascals before multiplying by m³/kg; this dimensional check prevents a thousand-fold error. The result is illustrative and does not replace equipment-specific property data, measurements or professional review.
Problem Statement: A reheat section raises specific enthalpy of 45 kg/s of steam by 580 kJ/kg. Assuming negligible external heat loss, reheat duty is 45 × 580 = **26.1 MW(th)**. Whether reheat improves overall cycle efficiency depends on the resulting turbine expansion and heat-supply conditions, not duty alone.
Worked Engineering Derivation:
**Verification and limitations.** For regenerative systems, a steam bleed lowers the downstream mass flow; use branch-by-branch energy balances. The result is illustrative and does not replace equipment-specific property data, measurements or professional review.