Italian compressor manufacturer Dorin is celebrating 30 years as a manufacturer of environmentally friendly CO2 compressors, having launched the first 4HP model in 1991.

Back then, Dorin was contacted about a possible collaboration by Norwegian CO2 refrigeration pioneer Gustav Lorentzen and his team.

Lorentzen and team were “investigating the possibility of applying CO2 transcritical technology in replacement of synthetic refrigerants, by validating floating head pressure COP optimization with varying heat sink temperatures,” explained Giacomo Pisano, Sales Manager of Dorin, about the beginning of the collaboration.

Dorin was happy to join the innovative work. “Innovation has always been our motto; we’ve understood the potential of natural refrigerants for a long time, both for refrigeration, chillers and heat pump applications,” Pisano said.

While the very first CO2 compressor from Dorin had a modest displacement of 3 m3 (106ft3)/h, the technology has taken enormous strides in the past 30 years. In 2002, the capacities had already increased to 12 m3 (424ft3)/h, and have been climbing steadily since. In 2020, Dorin introduced its largest compressor so far, the CD600, with a 60 m3 (2,219ft3)/h displacement, and the company is not stopping there. “We are in the final qualification test for a 102 m3 (3,602ft3)/h transcritical compressor which we target to launch by the end of this year,” Pisano revealed.

Dorin’s development work has also been recognized by independent organizations.  Its large CD600 CO2 compressor was awarded the 2021 AHR Expo Award in the refrigeration category.

The 102 m3/h will not necessarily be the end of the line for Dorin. When queried about whether there is a maximum capacity limit for CO2 compressors, Pisano said “Not really; I believe the main limiter is on other components such as vessels, separators, valves and the like.”

He added, “Increasing system sizes leads unavoidably to a significant increase in those components volume and this might be a limiter, but I strongly encourage those components manufacturers to start focusing on such topics, as CO2 transcritical technology potential is huge in industrial applications.”

Bigger and smaller

The size of CO2 compressors has not only been increasing. Dorin also manufactures “tiny cute babies” as Pisano called them, with 1 m3 (35.3ft3)/h displacement and a 1.5HP motor – a “perfect match for mini boosters needed for small format stores such as convenience shops and petrol stations.”

Dorin is also the sole manufacturer of a complete range of transcritical two-stage CO2 compressors, capable of withstanding low-temperature loads without a booster execution, Pisano noted.

Longevity and 15% greater efficiency

Over the years, Dorin has worked steadily to improve both quality and efficiency of its products.

“Many improvements have been implemented, making our compressors the most robust and reliable in the market,” Pisano stated. “We have several sites with original CO2 transcritical compressors running since 2003.”

The efficiency of Dorin’s compressors has also evolved since the first model was introduced in 1991. “A lot of effort has been put towards a continuous improvement of the isentropic efficiency levels,” Pisano said, adding that it has gone up by about 15% (peak to peak) over the last 30 years.

“Clearly we are still investigating further enhancements, which will soon make it possible to provide additional efficiency gains,” he concluded.