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Technology Focus

Jeff Newel, Hillphoenix

But in its lab, Hillphoenix tested a “non-optimised” system with a higher low-temperature load among other changes “because, believe it or not, systems out in the working world aren’t always optimised,” Newel said. The result was a 5.4% annual energy saving with parallel compression and a 6.5% saving with parallel compression and an ejector. “This is still good savings,” he added.

Liquid ejector advantage Giacomo Pisano, technical sales manager at Dorin, described at ATMOsphere America how the company is enabling retailers like Carrefour to operate transcritical refrigeration efficiently in the warm climates of Italy. One way is with liquid ejectors. In Europe, not only are manufacturers incorporating gas ejectors in transcritical systems, but liquid ejectors as well. Liquid ejectors allow for a flooded evaporator design. Some liquid may come back from the evaporator, but would be collected into a low-pressure receiver and then pumped by a liquid ejector into an intermediate-pressure receiver. “By working in this way, you manage to raise the evaporating temperature by [as much as] six degrees Kelvin, which means a very high COP increase,” said Pisano. Pisano said a gas ejector works most efficiently in combination with a liquid ejector. “If you manage to raise your suction pressure with a liquid ejector, you will have a smaller differential pressure across the gas ejector – which will then be able to transfer more mass flow.”

Giacomo Pisano, Dorin

In Europe, there are about 100 transcritical systems running with gas and liquid ejectors, he said, especially in very warm areas like Italy or Greece. “This kind of system, using parallel compressors, liquid and gas ejectors, is managing to completely delete the so-called equator for CO 2 applications.” Pisano cited a Carrefour supermarket in Turin, Italy, as an example of where this enhanced transcritical system, with a rack from Italian OEM Enex and Dorin compressors, is running. The store has a mediumtemperature capacity of 340 kilowatts and a lowtemperature capacity of 66 kilowatts, performs heat recovery for ambient heating and sanitary hot water usage, serves 160 evaporators, and is designed to work in ambient temperatures up to 45°C. According to Pisano, by using a system with parallel compression combined with gas and liquid ejectors, Carrefour gains 28% in efficiency over a basic transcritical system. “You can easily understand how, with this technology, you manage to boost the efficiency of a CO 2 system in very warm climates,” he said. At ATMOsphere Europe, meanwhile, Pisano acknowledged that CO 2 is becoming increasingly competitive with ammonia in the industrial refrigeration market. He cited Dorin’s six-cylinder transcritical compressors that can run up to 60 m3/h as a key technological development allowing CO 2 to operate at higher capacities. MG & AW

Accelerate Europe

Winter 2017

Accelerate Europe #9 Winter 2017  

HONOURING THE TRAILBLAZERS The past twelve months have been full of innovation in the HVAC&R sector. The winter 2017 edition of Accelerate...

Accelerate Europe #9 Winter 2017  

HONOURING THE TRAILBLAZERS The past twelve months have been full of innovation in the HVAC&R sector. The winter 2017 edition of Accelerate...