Spool compressor outperforms scroll in new analysis
31st May 2026
USA: New comparative analyses carried out with Torad’s R1234ze spool compressor is said to have demonstrated efficiency gains of up to 10% when compared to scrolls in cooling systems.
Three separate analyses conducted by the University of Illinois Urbana-Champaign’s Air Conditioning and Refrigeration Center, Department of Mechanical Science and Engineering are said to have demonstrated that the spool compressor achieved a superior COP, with efficiency improvements ranging from 2% to 10%. This boost was said to be driven by a 4% to 11% reduction in compressor power consumption. Additionally, the spool compressor maintained lower discharge temperatures, indicating enhanced thermal reliability and operating robustness.
US-based company Torad Engineering has been developing its rotary spool machine for over 10 years. Its patented technology is being designed to enable near-zero global warming air conditioning across a broad range of applications.
The spool compressor is a type of restrained vane device with several novel features which allow increased efficiencies and the ability to scale from small to larger capacities.
The latest simulation framework employed by the University of Illinois Urbana-Champaign validated steady-state compressor map models based on the AHRI 540 polynomial formulation. It used physically consistent condenser, evaporator, expansion device, and refrigerant property models. Parametric studies were conducted to examine the influence of outdoor air temperature, chilled-water inlet temperature, suction superheat, and evaporator pressure-drop effects on system performance.
Three comparative analyses were then performed. In the first analysis, the spool and scroll compressors were compared within the same chiller architecture using the same air-cooled condenser, the same water-to-refrigerant evaporator, and the same compressor size basis.
In the second analysis, refrigerant-side pressure-drop effects were introduced into the chiller model to assess whether comparative performance trends remained under more realistic non-ideal operating conditions.
In the third analysis, the spool compressor was evaluated in a chiller system and the scroll compressor in a DX system, while maintaining the same size basis and matching the two systems to equal cooling capacity at 95ºF outdoor air temperature.
The spool compressor is said to have achieved consistently higher COPs across all three analyses.
A copy of the report is available here.
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