U.S. component manufacturer Colmac Coil has noticed a “shocking” increase in the interest in CO2 (R744) evaporators for industrial applications over the past three years, according to Jeremy Olberding, Colmac Coil’s VP of Sales.

Olberding shared this observation following his presentation at the IIAR conference in Savannah, Georgia, held March 6-9.

Colmac Coil has seen a move away from both ammonia/NH3 (R717) and synthetics towards CO2 in evaporators for industrial applications, with CO2‘s share of the company’s output increasing from 5% in 2019 to 30% in 2022, Olberding said.

The huge increase in demand for CO2 evaporators has created a long backlog for Colmac Coil as the company attempts to adjust its production. Around 80% of the CO2 evaporators the company manufactures use DX technology, in line with the company’s traditional focus on DX evaporator technology for ammonia. The remaining 20% are typically overfeed units, Olberding said.

One of the reasons for the move towards CO2 is that it allows the removal of ammonia from the occupied space. Quoting what customers have told him, OIberding said, “I love ammonia as a refrigerant; it’s efficient, but keep it away from my people, my processes and my products.” So a way of doing that is putting CO2 in the refrigerated space and keeping ammonia on the outside, as in cascade systems, he explained.

The increased use of CO2 also has the benefit of increasing the number of players entering the field, leading to “much more cost-effective solutions,” Olberding noted.

One thing systems designers need to consider when working with CO2 is what temperature it requires, Olberding said, adding that modular-type systems can be a “great” option to accommodate end users with a number of different temperatures. This is one of the trends Colmac Coil has experienced, with many industrial end users expanding existing systems with modular CO2 add-ons for increased capacity and flexibility. 

The modular approach can also help reduce the need for welding in systems, as with CO2 it’s possible to connect sections with copper-iron tubing instead, a solution working well at all pressures. 

One of the biggest decisions end users have to make, once they’ve decided on a system type, is how they’ll defrost it, according to Olberling. The options are air, hot gas, heated glycol, electric and water, with each method having pros and cons. Looking at first cost, Colmac Coil regards hot gas as the default solution, with electric defrost being available at a 10% premium, and heated glycol costing 30% more than standard hot gas.

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