Carrier extends NaturaLine trials

- Carrier Traniscold is currently undertaking extended field trials of its ‘NaturaLINE’ environmentally sustainable reefer containers, which use CO2 as the refrigerant. This follows what the company calls the ‘world’s first’ successful global trials of such units during 2010 in partnership with Hapag Lloyd.


With the focus nowadays more on the global-warming potential (GWP) of refrigerants (an estimate of how much a given mass of gas will contribute to global warming) the company’s new breed of refrigerated containers harness the natural elements of CO2 as an alternative to the more commonly used hydrofluorocarbon (HFC) R-134a and R-404A.


“With its GWP of one, CO2 (also known as R-744) is essentially the baseline against which all other refrigerants are measured,” Kartik Kumar, Carrier’s director of marketing and strategic planning for global container refrigeration, told CM.


“CO2 compares favourably against HFC R-134a and R-404A refrigerants that have GWPs of 1320 and 3260 respectively. Although other synthetic refrigerants under development have lower GWPs than current HFCs, none approach CO2,” he added.


According to the company the use of natural refrigerants allays many of the concerns held by shipping lines, by removing flammability or high toxicity that are evident in other refrigerants, including those based on butane and ammonia.


Kumar says that using CO2 ‘adds no new environmental risk’, stating that in the event of a leak the gas essentially simply returns to the atmosphere.


Describing CO2 as ‘future proof’, Jim Taeckens, senior product manager for Carrier’s container product group, said that as a natural gas it is not subject to environmental taxes or is likely to be phased-out.


“CO2 has unique thermodynamic characteristics, with a heat-transfer coefficient, which determines the rate at which it absorbs and sheds heat, higher than conventional synthetic refrigerants,” he explained.


“Another aspect of the thermodynamic characteristics is that the system operates at higher pressures that allow for new and unique component designs that improve system performance,” says Taeckens.


In a mechanical refrigeration system, conventional refrigerants go through various phases – evaporation, compression, condensation and expansion. By contrast, CO2 changes into a liquid where conditions have a low ambient temperature and goes through a ‘gas cooling’ stage at moderate to high ambient temperatures.


This has brought about the need for a new gas cooler/condenser coil that wraps around the fan and has increased surfaces to maximise heat transfer, along with the need for a new multi-stage compressor.


With the technology for natural refrigerants differing greatly from its other container refrigeration systems, Carrier has introduced new power electronics and an advance software control system to optimise fan speeds and compressor capacity to match cooling loads and temperature control. It has also introduced ‘MicroLink’, a control unit that the company says will be as familiar to operate as any of its other units.
(Source:http://www.container-mag.com)