A chiller plant is the heart of a large‑scale cooling system, most often found in commercial buildings, industrial facilities, or campuses. It generates chilled water (typically 4–7 °C) which is then circulated through air‑handling units, fan‑coil units, process equipment, or heat exchangers to absorb heat and provide air‑conditioning or process cooling. Below is an overview of its key aspects:

1. Main Components

1. Chillers

   • Compressor (reciprocating, centrifugal, screw): Raises refrigerant pressure and temperature.

   • Condenser: Rejects heat from the refrigerant to either cooling‑tower water (water‑cooled) or ambient air (air‑cooled).

   • Expansion Device: Drops refrigerant pressure so it can evaporate at a low temperature.

   • Evaporator: Refrigerant absorbs heat from the building’s chilled‑water loop, cooling the water.

2. Cooling Tower (for water‑cooled systems)
   Rejects heat extracted by the condenser to the atmosphere by evaporative cooling.

3. Pumps

   • Condenser‑water pumps (water‑cooled systems): Circulate cooling‑tower water through the condenser.

   • Chilled‑water pumps: Circulate chilled water through the building’s distribution loop.

4. Piping and Valves
   Insulated chilled‑water piping, balancing valves, strainers, and isolation valves.

5. Controls & Instrumentation
   Temperature sensors, pressure gauges, flow meters, and a building‑management system (BMS) or chiller‑plant controller that sequences chillers, cooling towers, and pumps for optimum efficiency.

2. Types of Chiller Plants

TypeProsCons

Water‑CooledHighest efficiency (COP > 6:1); long lifeRequires cooling towers; higher footprint

Air‑CooledNo cooling tower; simpler installationLower efficiency (COP ≈ 3–4:1); noisier

AbsorptionUses waste heat or steam (no electric drive)Lower COP (≈ 1.0–1.2); high capital cost

3. How It Works (Simplified Cycle)

1. Evaporation: Low‑pressure liquid refrigerant enters the evaporator, vaporizes by absorbing heat from the chilled‑water loop.

2. Compression: The vapor is compressed, raising its pressure and temperature.

3. Condensation: High‑pressure vapor enters the condenser, rejects heat to condenser water or air, and condenses to liquid.

4. Expansion: Liquid refrigerant passes through an expansion valve, dropping in pressure and temperature, then re‑enters the evaporator.

4. Plant Configuration & Control

• Staging and Sequencing
  Multiple chillers and towers are staged on/off or modulated (via variable‑speed drives) based on cooling demand to maximize part‑load efficiency.

• Primary‑Secondary Pumping
  Decouples chiller’s chilled‑water loop from the building loop, stabilizing flow and temperature control.

• Variable‑Primary Pumping
  Eliminates the secondary loop by slowing pumps to match the chiller’s required flow, reducing pumping energy.

• Free Cooling / Hybrid Systems
  Use outdoor air or tower water when ambient conditions permit to bypass compressors and save energy.

5. Design & Efficiency Considerations

• Coefficient of Performance (COP)
  Ratio of cooling provided (kW) to electrical input (kW). Higher COP = more efficient.

• Part‑Load Performance
  Most systems operate below full load—ensure good efficiency at 30–70 % load.

• Heat Recovery
  Capture condenser heat for domestic hot water or process heating.

• Redundancy & Reliability
  N+1 configuration (one extra chiller) often used to maintain operation during maintenance.

6. Common Applications

• Commercial offices, hospitals, universities, data centers, manufacturing processes (plastics, food, chemicals), district cooling networks.

7. Operation & Maintenance Tips

• Regular Water Treatment: Prevent scaling, corrosion, biological growth in cooling‑tower water.

• Filter Inspections: Keep strainers and coils clean to maintain heat‑transfer efficiency.

• Control Calibration: Verify sensors and control sequences seasonally.

• Vibration Analysis: Monitor compressors and pumps to detect imbalances early.

Summary
A well‑designed and -operated chiller plant is critical to energy‑efficient cooling in large‑scale facilities. By selecting the right chiller type, staging strategy, and incorporating advanced controls (and potentially heat‑recovery or free‑cooling modes), operators can achieve both reliability and low operating costs.