Cooling Systems, Water and Environmental Constraints
Comprehensive university textbook unit covering fundamental principles, governing relationships, and engineering applications of Cooling Systems, Water and Environmental Constraints.
§5.1 Condenser heat-rejection accounting
**Core topic:** water-side calorimetry. **Representative relation:** `Q_reject = m_dot_cw*cp*DeltaT`. **Case context:** condenser cooling-water loop.
§5.2 Cooling towers and ambient boundaries
**Core topic:** approach, range and wet-bulb influence. **Representative relation:** `Range = T_hot-T_cold`. **Case context:** forced-draft evaporative cooling tower.
§5.3 Water consumption and blowdown
**Core topic:** cycles of concentration and water budgets. **Representative relation:** `COC = C_circulating/C_makeup`. **Case context:** cooling tower makeup, drift and blowdown records.
§5.4 Dry and hybrid cooling
**Core topic:** heat-exchanger effectiveness and climate effects. **Representative relation:** `Q = UA*LMTD`. **Case context:** air-cooled condenser under hot weather.
§5.5 Environmental evaluation and monitoring
**Core topic:** resource intensity across a reporting boundary. **Representative relation:** `I_water = V_consumed/E_net`. **Case context:** monthly plant water balance.
Step-by-Step Power Plant Engineering Solutions
Three original questions connect calculations, definitions and interpretation. Open each solution to follow the reasoning.
Problem Statement: A cooling-water loop carries 2600 kg/s with assumed cp = 4.18 kJ/(kg K) and temperature rise 7 K. Heat duty is 2600 × 4.18 × 7 = **76,076 kW**, or 76.076 MW(th). A 0.2 K sensor offset would change the inferred duty by about 2.17 MW, so calibration matters.
Worked Engineering Derivation:
**Verification and limitations.** This single-phase sensible estimate does not include independent condenser steam-side validation. The result is illustrative and does not replace equipment-specific property data, measurements or professional review.
Problem Statement: A cooling tower returns water at 29 °C after receiving hot water at 36 °C. Cooling range is **7 K**. If ambient wet-bulb temperature is 25 °C, the cold-water approach is **4 K**. Neither number alone specifies evaporation, electrical fan demand or biological treatment requirements.
Worked Engineering Derivation:
**Verification and limitations.** Cooling-tower performance changes with humidity, air flow and water chemistry. The result is illustrative and does not replace equipment-specific property data, measurements or professional review.
Problem Statement: A concentration proxy is 1800 mg/L circulating-water dissolved solids divided by 300 mg/L makeup-water solids, giving **6 cycles of concentration**. This simplified ratio assumes consistent species behavior and mixing; chemical reaction and selective precipitation break the scalar approximation.
Worked Engineering Derivation:
**Verification and limitations.** A plant water budget also requires evaporation, blowdown, drift and leak measurements. The result is illustrative and does not replace equipment-specific property data, measurements or professional review.
Problem Statement: A simplified air-cooled exchanger has UA = 250 kW/K and a log-mean temperature difference of 16 K. Its idealized rate is **4.0 MW(th)**. Real UA varies with fouling, air velocity, fin condition and operating temperature, so a hot-day prediction requires actual equipment data.
Worked Engineering Derivation:
**Verification and limitations.** An assumed fixed temperature approach can conceal a high-temperature derating risk. The result is illustrative and does not replace equipment-specific property data, measurements or professional review.
Problem Statement: A plant consumes 500,000 m³ of water while exporting 700,000 MWh(e) over the same annual period. Consumptive intensity is 500,000/700,000 = **0.714 m³/MWh**. Withdrawal volume could be much larger; report the two separately and document where water is returned.
Worked Engineering Derivation:
**Verification and limitations.** This accounting value is not a license to withdraw water or discharge heated effluent. The result is illustrative and does not replace equipment-specific property data, measurements or professional review.