Scroll compressors and screw compressors are two common types of positive displacement compressors, which are significantly different in structure, working principle, performance characteristics and application fields. The following is a detailed comparison of the two:
1. Working principle and structure
- scroll Compressor
- principle: It is composed of a movable scroll and a fixed scroll. The movable scroll revolves eccentrically around the fixed scroll to form multiple closed crescent-shaped compression chambers. The gas is compressed during the gradual shrinking of the cavity and finally exits from the center vent hole of the stationary disk.
- Structure: No reciprocating parts, relying on geometric meshing to achieve compression, simple and compact structure.
- Screw compressor
- principle: Single screw or twin screw (yin and yang rotor) mesh with each other, when the rotor rotates, the element volume decreases, and the gas is compressed and discharged.
- Structure: Divided into oil-injected and oil-free types. Oil-injected screws are lubricated, cooled and sealed by oil; oil-free screws are sealed by special coatings, water or gaps.
2. Comparison of performance characteristics
| Contrast Item | scroll Compressor | screw compressor |
|---|
| vibration and noise | very low vibration (no reciprocating inertial force), noise is usually less than 65dB | the vibration is small, but the oil injection machine type may produce some noise (about 75dB or less) due to the oil flow. |
| Efficiency | high efficiency under medium and small flow, but affected by leakage, the compression ratio should not be too large (usually ≤ 10) | wide working conditions are adaptable, single-stage pressure ratio can reach 8~13 (fuel injection) or higher (multi-stage), but the micro-efficiency is lower than the vortex. |
| Reliability | few moving parts, no wear (only meshing), long life (design life of more than 10 years) | high reliability, but the bearings and seals need to be maintained, and the life is affected by the lubrication method (oil-free models cost more) |
| maintenance complexity | simple maintenance without frequent replacement of parts | the lubricating oil and filter element (injector type) need to be replaced regularly, and the oil-free model needs water cooling or special materials. |
| Cost | high machining precision, large initial investment | rotor processing is complex and equipment costs are high (especially five-axis processing), but long-term operating costs are low (fuel injection machine type) |
3. Application areas
- scroll Compressor
- areas of Advantage: Air conditioning, small cold storage (3-30HP), low noise scenes (hospitals, laboratories), micro compressed air systems.
- Restrictions: Low compression ratio, not suitable for high-pressure gas (such as industrial-grade high-pressure air).
- Screw compressor
- areas of Advantage oil and gas (pressurization, transportation), large industrial refrigeration (cold storage, central air conditioning), chemical process (liquid resistance, multi-phase mixed transmission).
- Segment Applications: Oil-free screws are suitable for pharmaceutical/food grade gases, and oil-injected screws are widely used in occasions that require cost-effectiveness.
4. Technical bottleneck and development trend
- scroll Compressor
- challenge surface processing is difficult, and leakage control depends on precision assembly.
- Development: Improve tightness by material optimization (e. g. ceramic scroll).
- Screw compressor
- challenge: The high-pressure ratio needs multi-stage series connection, and the miniaturization efficiency is low.
- Innovation permanent magnet frequency conversion technology (energy saving 15-20%), asymmetric rotor profile (increase volumetric efficiency).
Summary
scroll compressors are dominant in silent and miniaturized scenarios, while screw compressors are known for their high reliability and wide adaptability to operating conditions. The choice should be based on specific requirements, such as pressure range, noise limit and long-term maintenance costs.
