2.4.1 — Rotary Compressors
Rotary compressors use rotating motion to compress refrigerant. The most common design in refrigeration is the rolling piston (rotary vane) type, where an eccentric roller on the motor shaft rotates within a cylindrical housing. A spring-loaded vane maintains contact with the roller, dividing the cylinder into suction and compression sides.
Operating Principle
Rolling Piston Cycle
- Suction side: the expanding crescent between the roller and cylinder wall creates low pressure, drawing refrigerant in through the suction port
- Compression side: simultaneously, refrigerant trapped in the decreasing crescent on the opposite side of the vane is compressed and discharged when it reaches the discharge port
- Each full revolution of the rotor completes one compression cycle; suction and discharge occur continuously in different regions of the cylinder
Characteristics
| Capacity Range | 0.5 to 5 tons (1.76 to 17.6 kW) typically |
| Efficiency | Good; high volumetric efficiency |
| Size | Very compact |
| Applications | Room air conditioners, residential systems, refrigerators, dehumidifiers |
Advantages
- Very compact size
- Few parts, simple construction
- High volumetric efficiency
- Low vibration
- Cost-effective for small capacities
Disadvantages
- Limited capacity range
- Vane wear limits service life
- Sensitive to liquid flooding
- Not field-serviceable