U.S. Research Firm CTS Develops Efficient, Low-Cost CO₂ Condensing Unit

Creative Thermal Solutions CTS), an Urbana, Illinois (U.S.)-based HVAC&R research company, has developed a small, low-cost CO₂ (R744)-based condensing unit designed for commercial applications.

The prototype, with a cooling capacity of about 1.6kW (0.45TR), was developed as an example of what could be achieved in a low-cost CO₂ condensing unit with the same efficiency and capacity as a comparable R448A unit, explained Stefan Elbel, CEO of CTS. Elbel is also Research Assistant Professor in the Department of Mechanical Science and Engineering, and Co-Director, Air Conditioning and Refrigeration Center, at the University of Illinois at Urbana-Champaign.

The prototype design was for medium-temperature applications, but a similar design could be used for low-temperatures as well, said Elbel.

CTS is open to collaborating with manufacturers in a commercial product, said Elbel. “It’s a relatively small system to start with, but it might spark some more interest in a low-cost-type system for larger capacities.” CTS is already working on a scaled-up version of the unit, he added.

The initial prototype would have immediate application to a walk-on cooler, for which CTS has also designed a CO₂-optimized evaporator. The capacity of the prototype would be low for typical commercial display cases, but a larger-capacity version would be suitable for display case systems or larger walk-ins, Elbel said.

Converted R448A unit

In developing its prototype, CTS converted a condensing unit using R448A to an “extremely low cost” CO₂ unit with small hermetic rotary compressors but no “fancy” components like ejectors, said Elbel.

“We were able to achieve, after only a little bit of optimization, the same efficiency and capacity as the R448A unit,” he added. The optimization related to charge, pressure and fans.

Elbel noted that the of the prototype CO₂ unit was designed for an indoor rating, with conditions at 90°F (32.2°C), and the functionality of the system was tested up to 110°F (43.3°C).

Founded by Pega Hrnjak, its President, in 2003, CTS is known for conducting pioneering research in the use of natural refrigerants.

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