Carrier Refrigeration

ContainerLINE November 2014 Issue

Carrier Refrigeration

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CO2 Makes Sense | ContainerLINE November 2014 refrigerants. Its design adheres to BS EN378-2 standards, helping to ensure the system is safe and reliable. Following applicable safety standards, components are tested at pressures well beyond the maximum pressure the unit will see in service. Moreover, the NaturaLINE system has three layers of safety limits on the high-pressure side of the system, including built- in software controls that limit pressures to 1,900 psig; an electromechanical high-pressure switch with a pressure limit of 2,000 psig; and a mechanical pressure relief valve that has a limit of 2,250 psig. These safety limits help ensure that the system will not experience abnormal pressure changes. "Carrier has a unique perspective, having seen similar progression from low- to higher-pressure refrigerants in retail settings and in residential and commercial air conditioning systems," Goh said. "Concerns about higher pressures were soon overcome once people saw how reliably the new systems performed. "On the matter of efficiency, CO2 has different thermodynamic properties than today's HFC refrigerants. You certainly couldn't use CO 2 in an existing system and expect the same performance," Goh said. "However, with the NaturaLINE unit, Carrier Transicold's engineers elevated CO 2's efficiency to higher levels, introducing to container refrigeration innovations that have proven successful in other efficient refrigeration systems, including design elements found in the CO 2OLtec supermarket system. "Examples include a new gas cooler in place of a traditional condenser, a multi-stage compressor with variable speed drive, two-speed fans, a flash tank and advanced software controls. Together these combine to produce efficiencies that compare closely to Carrier's industry-leading PrimeLINE unit. "We didn't develop a CO 2 system because it was the easiest or fastest solution to engineer," Goh said. "We chose it because we believe it to be the best, most compelling refrigerant choice for this application." w reduction because less fuel is burned to generate electricity, and carbon emissions are, in turn, reduced. In one sense, CO 2 as a refrigerant is a "back to the future" concept. It has a proven track record, having been successfully used in industrial refrigeration applications more than 130 years ago. In recent years, CO 2 has gone mainstream in commercial refrigeration applications, including supermarkets and convenience stores. Carrier's CO 2OLtec ® system has seen rapid and widespread adoption with more than 1,000 installations across Europe, compared with 150 just four years ago. While a very logical and compelling case can be made for Carrier's selection of CO 2 as a refrigerant for transport applications, others within the industry are evaluating alternatives, including different natural or synthetic refrigerants that suffer from certain drawbacks such as combustibility, toxicity and global warming potentials significantly higher than CO 2. A 'No-Pressure' Refrigerant Decision "Not surprisingly, those within the industry who presently lack a non-HFC solution have decried CO2 as a refrigerant, taking aim at its operating pressures and cooling efficiency," Goh said. "On the matter of operating pressures, some have questioned the higher system pressures required of the NaturaLINE system," Goh said. "We welcome the chance to address that. "First and foremost, safety is integral to all that we do. Similar to the CO 2OLtec system used safely in supermarkets throughout Europe, Carrier's NaturaLINE system runs at higher pressures than today's HFC-based systems – up to 1,800 psi." While these pressures are higher than those used in HFC systems, they're a fraction of the pressures required of other types of systems found on ships and at depots. Examples include forklift trucks and straddle carriers that use hydraulic systems for lifting at pressures of 5,000 to 20,000 psi. On ships, winches and watertight doors use oil-operated hydraulic systems with pressure ranges similar to forklifts. The NaturaLINE system introduces a more rugged design and construction, which is necessary to accommodate higher pressures. For example, coil tubes and other system components use thicker-walled material than found on systems using HFC Efficient NaturaLINE unit uses the natural refrigerant carbon dioxide. 3

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