Construction and Working Principle
- Compressor: Compresses refrigerant gas (e.g., R-134A or R-410A) into a high-pressure, high-temperature gas.
- Condenser: Cools the refrigerant into a liquid by dissipating heat via airflow or water (cooling towers).
- Expansion Valve: Reduces refrigerant pressure and temperature before entering the evaporator.
- Evaporator: Absorbs heat from the air, converting refrigerant back to gas.
- Air Handling Unit (AHU):
- Components: Filters, heating/cooling coils, fans, humidifiers/dehumidifiers, dampers.
- Function: Mixes outdoor and indoor air, filters contaminants, adjusts temperature/humidity, and distributes conditioned air via ductwork.
Working Principle
- Refrigerant cycles through compression, condensation, expansion, and evaporation to absorb/reject heat.
- Centralized Systems: Use chilled water pipes to transport coolant from chillers to AHUs for air cooling.
- Direct Expansion (DX): Refrigerant directly cools air at the evaporator (common in smaller systems).
| Type | Description |
|---|---|
| Chillers produce chilled water distributed via pipes to AHUs. | |
| Self-contained systems (installed outdoors) for medium-sized spaces. | |
| Installed on roofs, ideal for factories/warehouses. | |
| Indoor and outdoor units connected by refrigerant lines. | |
| Cool water or air for large-scale cooling (data centers, manufacturing). | |
| Variable Refrigerant Flow adjusts cooling/heating per zone for energy efficiency. | |
| Use water evaporation for cooling in dry climates. | |
| Heat-driven cooling (e.g., waste heat from industrial processes). |
- Humidification: Adds moisture via steam generators or spray systems.
- Dehumidification:
- Cooling Coils: Condense moisture from air (common in AHUs).
- Desiccant Systems: Use materials like silica gel to absorb moisture.
- HDH Process: Combines humidification and dehumidification for desalination or precise humidity control.
- Temperature & Pressure Controls
- Thermostats: Regulate temperature by cycling compressors.
- Pressure Switches:
- High/Low Pressure Cut-Outs: Shut down the system to prevent compressor damage.
- Oil Pressure Safety: Protects against low oil pressure in compressors.
- Mechanical Regulators: Adjust refrigerant flow via expansion valves.
- Safety Devices
- High-Pressure Trip: Prevents compressor overload.
- Low-Pressure Trip: Avoids air ingress and refrigerant loss.
- Low Oil Pressure Trip: Protects compressor bearings.
- Pressure Relief Valves: Release excess refrigerant during emergencies.
- Cooling Towers & Chilled Piping
- Cooling Towers: Remove heat from condenser water via evaporation. Warm water is sprayed over fill material while fans draw air upward, cooling the water for reuse.
- Chilled Piping: Insulated pipes distribute chilled water (5–7°C) from chillers to AHUs.
- Direct Expansion (DX) System
- Operation: Refrigerant directly cools air at the evaporator coil (no chilled water).
- Advantages: Simpler installation, lower upfront costs.
- Limitations: Less efficient for large spaces compared to chilled water systems.
| Task | Frequency | Details |
|---|---|---|
| Monthly/90 days | Depends on air quality (hazardous environments: monthly). | |
| Quarterly | Remove debris from condenser/evaporator coils. | |
| Biannually | Use UV dye or electronic sniffers. | |
| Annually | Verify levels and recharge if needed. | |
| Annually | Check tension and wear on compressor belts. | |
| Annually | Test thermostats, pressure switches, and safety devices. |
- VRF Systems
- Operation: Uses inverter-driven compressors to vary refrigerant flow to multiple indoor units.
- Benefits:
- Simultaneous heating/cooling in different zones.
- High energy efficiency (up to 30% savings vs. traditional systems).
- Flexible installation with long refrigerant piping.