What Are The Differences Between Screw-type And Rotary-type Air-cooled Chillers?

The main differences between screw and rolling screw-type and scroll-type air-cooled chillers lie in four areas: compressor technology, energy efficiency, application scenarios and cost. The analysis is as follows:
I. Compressor Technology: Mechanical Principle Determines Performance Limits
Screw
Principle: two intermeshing screw rotors are used to compress the refrigerant by volumetric displacement, which exhibits linear compression characteristics.
Strengths:
High cooling capacity: single unit can achieve hundreds of kilowatts of cooling capacity, suitable for centralized cooling applications.
Stable continuous operation: Durable screw rotors allows 24/7 continuous operation, suitable for chemical plants, cold storage and other facilities.
Stepless capacity control: 20% -100% Variable capacity control of load through sliding valves to accommodate fluctuating cooling requirements.
Scrolls
Principle: Using the phase difference between rotating and stationary scrolling discs, multiple tapering compression chambers are created to achieve tapering.
Strengths:
4. Low vibration, low noise: less moving parts, 40% less vibration, 5-10 dB(A) of low noise compared to screw-type chillers, suitable for noise sensitive environments.
3. Partialload efficiency: performance factors of 4.2-4.8 can be achieved at a load of 30% -80% load, which is 8% -12% higher than for screw-type chillers.
Precise temperature control: + -0.1°C temperature control accuracy to meet the needs of drug storage, optical instrument manufacturing, etc.
ii. Energy Efficiency: Load Profile Determines Energy Saving Strategy
Screw
Excellent high load efficiency: In industrial applications with a cooling capacity of more than 300 kW, the isentropic efficiency can exceed 70%, with low energy consumption per unit of cooling capacity.
Low load efficiency: Below 50% load, sliding valve operation results in energy losses and COP may fall below 3.5.
Scrolls
Important Partial Load Advantage: Running in parallel with multiple compressors or frequency conversion technology allows for high efficiency at low load times, suitable for applications requiring dynamic cooling such as shopping malls and data centers.
4. Lower total cost: less moving parts, 15 to 20 per cent lower maintenance costs and generally 20 to 20% -30% per cent lower initial investment compared to screw-type chillers. III. Application Scenarios: Matching Requirements Is Key to Selection
Screw Compressor Applications
Large-scale industrial refrigeration: chemical plant, such as refrigeration, cold storage, require to operate continuously at full capacity.
Centralized chilled water systems: such as large shopping malls, hospitals, and so on, with a high single-machine cooling capacity, reduce the number of equipment.
1. Extreme conditions: Equipped with an oil cooling system that can operate steadily at high temperatures (e.g., 50°C).
Scroll Compressor Applications
Commercial building air conditioning: such as office buildings, hotels, etc., require dynamic adjustment of refrigeration capacity, noise sensitivity.
Precise temperature control: such as medical laboratories, food processing lines, etc., requires ±0.5°C temperature control accuracy.
Space-restricted locations: Modular design allows for flexible integration into supermarket refrigeration, laboratory temperature control systems; some models support wall-mounted installations.
IV. INTRODUCTION Structure and costs: balancing initial investment and operating costs
Screw Compressor
Complex structure: requires an oil circulation system, high precision gears and a large number of moving parts, which reduces the maintenance cycles (overhauls every 3 to5 years).
Cost Structure: High initial investment, but an average annual operating time of over 6000 hours, with cumulative energy savings of 18 to 25 per cent over scroll compressors.
Scroll Compressor
Compact design: 60% smaller than reciprocating compressor of the same capacity, simple piping design, easy installation and maintenance.
Cost Advantage: Oil-free lubrication reduces maintenance frequency, the cost of replacing key components is low, and is suitable for projects with limited budgets or space constraints.