What Is The Difference Between Screw And Scroll Air-cooled Chillers?

There are significant differences between screw and scroll air-cooled chillers in core technology, performance and application scenarios. The following is a comparative analysis from multiple dimensions:
I. Technical principles and structural differences of compressors
1. Scroll air-cooled chillers
Compressor type: A scroll compressor is used, and the compression chamber is formed by the meshing of the movable scroll and the static scroll.
Working principle: The movable scroll moves eccentrically around the static scroll, and the compression of the refrigerant gas is achieved by gradually reducing the volume of the compression chamber. The process is continuous and smooth.
Structural features:
There are no reciprocating parts such as pistons and crankshafts, and the structure is compact and the volume is small.
There is no clearance volume in the compression process, high efficiency, and extremely low operating noise (usually ≤75dB) and vibration.
The cooling capacity of a single compressor is usually 20-150 tons (about 70-525kW), which is suitable for small and medium-sized refrigeration needs.
2. Screw air-cooled chiller
Compressor type: Screw compressor, composed of male rotor (convex teeth) and female rotor (concave teeth) meshing.
Working principle: When the rotor rotates, the volume between the teeth decreases as the meshing position changes, achieving gas compression, which belongs to volumetric compression.
Structural features:
The rotor needs to be supported by bearings and equipped with a complex oil system (lubrication, cooling), and the structure is relatively complex.
There is periodic gas pulsation during the compression process, and the noise (80-90dB) and vibration are higher than the scroll type.
The cooling capacity of a single compressor is usually 100-1000 tons (about 350-3500kW), which is suitable for medium and large refrigeration scenarios.
2. Installation and maintenance characteristics
Scroll air-cooled chiller
Installation advantages:
Modular design, light weight of a single module (usually ≤1.5 tons), easy transportation and installation, no need for large lifting equipment.
No dedicated machine room is required, it can be installed outdoors (protective measures are required), and it occupies a small area (about 2-5㎡/module).
Maintenance features:
Oil-free lubrication design (some models) or simple oil circuit system, less maintenance, long maintenance cycle (usually 1-2 times a year).
Intelligent fault diagnosis, modules can be replaced separately during maintenance, and downtime is short.
Screw air-cooled chiller
Installation advantages:
The single unit is large in size (occupying about 5-15㎡), requires a fixed foundation and machine room, and professional lifting equipment is required during installation.
Multiple screw compressors can be integrated and run in parallel to meet the requirements of ultra-large loads.
Maintenance features:
The oil circuit system is complex, and lubricating oil and oil filter need to be replaced regularly (maintenance cycle 3-6 months), and the maintenance cost is high.
Rotor wear may affect efficiency, and professional maintenance (such as rotor grinding) is required after long-term operation.
3. Differences in application scenarios
Applicable scenarios for vortex air-cooled chillers
Small and medium-sized commercial buildings: such as central air-conditioning systems in shopping malls, hotels, and office buildings (cooling load ≤ 1000kW).
Industrial cooling: cooling of small and medium-sized processes such as injection molding machines, electronic equipment, and food processing, which require frequent start-stop or load fluctuations.
Areas with water shortage or limited space: such as arid areas and rooftop open-air installation scenarios, where cooling towers and water sources are not required.
Scenarios with low noise requirements: such as areas around hospitals and schools that are sensitive to equipment operation noise.
Applicable scenarios for screw air-cooled chillers
Large industrial projects: centralized cooling systems in chemical, pharmaceutical, metallurgical and other industries (cooling load > 1000kW).
Continuous high-load operation scenarios: such as data centers and cold storage warehouses, which require 24-hour uninterrupted cooling and stable load.
Scenarios that require precise load adjustment: such as laboratory constant temperature and precision processing equipment, slide valve adjustment can achieve 1% load precision control.
Severely cold areas: Screw compressors are more adaptable to low temperatures (with oil heating systems), which can reduce cold start failures.
4. Comparison of costs and economic efficiency
Initial investment cost:
Scroll type: The cost per refrigeration ton is about 800-1200 yuan. The initial investment is low when modularized, which is suitable for phased construction.
Screw type: The cost per refrigeration ton is about 600-1000 yuan. The cost per refrigeration ton of large units is lower, but the overall equipment and installation costs are higher.
Operating cost:
Scroll type: Higher energy efficiency under partial load, suitable for scenes with large load fluctuations, and lower annual operating electricity costs.
Screw type: Slightly higher full load efficiency, suitable for long-term high-load operation, and the annual operating electricity cost depends on the actual load rate.
Life cycle:
Scroll type: The life under normal maintenance is about 15-20 years, and the compressor has no wear (pure rolling friction).
Screw type: The life is about 20-25 years, but the rotor and bearings need to be replaced regularly, and the full-cycle maintenance cost is higher than the scroll type.
Summary: How to choose the right model?
Choose a scroll air-cooled chiller:
If the demand is small or medium cooling capacity (<500kW), the installation space is limited, the load fluctuation is large, the noise requirement is high, or the budget is biased towards economy, the scroll type is preferred.
Choose a screw air-cooled chiller:
If the demand is large cooling capacity (>500kW), long-term high-load operation, precise load adjustment is required, or the equipment life cycle cost is not sensitive, the screw type has more advantages.
In practical applications, the two can also be used in combination (such as using the screw type to bear the base load in large projects and the scroll type to bear the fluctuating load) to optimize energy efficiency and cost.