The Differences Between Screw Compressors and Scroll Compressors in Air-Conditioning Units

Core Structure and Operating Principle

Screw compressors operate by rotating two intermeshing male and female rotors within the compressor housing, achieving gas intake, compression, and discharge through changes in the volume between the rotor teeth. They have relatively few moving parts and rely primarily on the synchronized rotation of the rotors to complete the compression cycle.

A scroll compressor consists of a stationary scroll and an eccentrically rotating orbiting scroll. As the gas flows from the outer periphery toward the center within the meshing space between the two scrolls, it is progressively compressed, enabling a continuous and smooth compression process.

Applicable Capacity and Power Range

The differing design objectives of the two types of compressors directly determine their respective roles within air-conditioning systems:

• Screw-type:Typically suited for medium to large cooling capacities, with a single unit capable of delivering from several tens of kilowatts up to several hundred kilowatts, making it ideal for large commercial complexes, industrial facilities, or centralized district cooling systems.
• Vortex type:It is commonly used in medium- and small‑capacity cooling applications, with individual unit capacities typically ranging from a few kilowatts to around 30 kW. It finds widespread use in residential central air-conditioning systems, small commercial units, and distributed heating and cooling projects.

Operational Efficiency and Part-Load Performance

In terms of energy efficiency, each has its own advantages. Screw compressors feature shorter internal leakage paths, enabling them to maintain high volumetric efficiency even under high condensing pressures or large temperature differentials, and they are often paired with variable-frequency drives to achieve wide-range capacity modulation.

Screw compressors, owing to their compact design and low friction losses, exhibit high adiabatic efficiency under full-load operation. Their suction valve plates do not require frequent opening and closing, thereby reducing throttling losses and delivering excellent COP values under typical operating conditions.

Vibration, Noise, and Maintenance Characteristics

The rotor of a screw compressor undergoes high-speed rotational motion; insufficient balancing or bearing wear can readily give rise to mechanical noise at specific frequencies and axial vibrations. Regular monitoring of the oil‑lubrication system and seal components is essential to detect wear and degradation.

Scroll compressors feature no suction or discharge valves and exhibit smooth motion, inherently delivering low vibration levels and superior quiet operation. Routine maintenance primarily focuses on the lubrication system and the electrical control module, resulting in a relatively low overall failure rate.

Engineering Selection Reference

In practical projects, it is essential to match the system with the building’s load profile, available installation space, and long-term operation and maintenance requirements.

• For systems with a cooling capacity requirement exceeding 50 kW or those requiring multiple units to be paralleled for capacity expansion, the screw‑compressor solution should be given priority.
• For small terminals with stringent indoor noise‑reduction requirements, limited equipment‑room space, or frequent load fluctuations, a scroll‑type compressor is more suitable.
• In extreme high-temperature environments or for specialized processes requiring ultra-low‑temperature refrigeration, calculations must be performed in conjunction with the specific properties of the refrigerant and the compressor’s design parameters.