REFRIGERANTS
Secondary refrigeration: a viable alternative
Durapipe’s industrial brand manager, Fraser Higgins, discusses the benefi ts that secondary refrigeration systems can off er.
I
t is clear low global warming potential (GWP) refrigerants are the future for refrigeration systems as the phase-down of HFC gases gathers pace. Preparing to comply with the reduced levels of refrigerant gas carbon emissions to be enforced by 2030, increasingly more businesses are investing in switching to the lower GWP HFOs or natural refrigerants.
With tens of thousands of supermarkets, shops and restaurants using commercial refrigeration affected by the F-Gas regulations, several major retailers have already announced commitments to move away from HFC gases. Aldi has confirmed it will be utilising natural refrigerants in all of its stores, with a transition to CO2
refrigeration
units, while the Co-op has committed to adopting the HFO R448A as its preferred option for refrigerant needs across its stores.
While natural refrigerants meet the requirement of reducing carbon gas emissions, they are not harmless or non-toxic. This leads to the question of why secondary refrigeration systems are not being widely adopted to comply with the new regulations and reduce environmental impacts.
Traditional direct expansion (DX) systems are still the most widely operated across a variety of industries,
but Durapipe UK is advising that adopting a secondary refrigeration system could not only reduce environmental impact, but deliver significant cost savings. A centralised DX set up is typical for refrigeration systems installed throughout Europe and usually utilises between three to eight compressors, located in a plant room, which are connected to an external air-cooled condenser. High pressure refrigerant is fed directly from the plant room to the chiller units, via a liquid receiver, and the refrigerant vapour is then returned to the compressors via a suction line.
The main issue experienced with DX solutions is the leakage rate of refrigerant, due to the large refrigerant charge required; a typical supermarket DX system will use between 1,360-2,270kg of refrigerant. The average annual refrigerant leakage rate experienced in these systems is up to 15%, which can rise to up to 30% in older systems.
In contrast, secondary refrigeration systems use two separate circuits, with heat from the chiller units transferred to a heat exchanger by circulating a cooling medium, where the heat is absorbed by a primary refrigerant. Typically, the cooling medium used is a water and either glycol or hycool mixture, with propylene
36 August 2018
www.acr-news.com
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