and trailers. The big problem with R134a when it leaks to atmosphere is what is described as its âglobal warming poten
News
Refrigerant gas rumpus rolls on A
simmering and increasingly bitter row over the pros and cons of various refrigerant gases look set to boil over soon from car air-conditioning systems into commercial vehicles. At the heart of the dispute is the familiar refrigerant R134a (chemical formula CF3CH2F), long used in car and commercial vehicle aircon systems as well as in many commercial refrigeration systems such as those used on controlled-temperature trucks and trailers. The big problem with R134a when it leaks to atmosphere is what is described as its “global warming potential” (GWP). This is put as high as 1,440 because it takes 13 years for R134a to break down into its constituent gases. A newer refrigerant, R1234yf (chemical formula C3F4H2), produced by the giant Dupont and Honeywell corporations of the US, has been singled out as the preferable replacement for R134a because it has a much lower GWP, 4. Carbon dioxide, itself used as a refrigerant gas called R-744, with a GWP of 1, has been ruled out so far for use in air-con systems. It takes only a week for R1234yf to break down into its constituent gases. This is why it is favoured by European authorities and others globally and why a European Union law has been introduced banning R134a in newly type-approved car air-con systems from 1 January this year. The plan had
been to phase in R1234yf in other applications, including trucks and trailers over several years. Everybody seemed content with this plan until Daimler engineers last year discovered what they consider a serious fire risk with R1234yf. Daimler feels so strongly about the risk that it is refusing to use the Dupont/Honeywell gas. The French government responded a couple of months ago by banning sales of some new Mercedes cars in France. Last month the French authorities relented a little on this, apparently based on a legal technicality. But the central dispute remains unresolved. Now Toyota has joined Daimler and decided to boycott R1234yf, at least temporarily, in its car air-conditioning systems in Europe. “Toyota regards it as the duty of individual companies within the automotive industry to ensure that vehicles meet
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current safety standards,” says a Toyota statement from Germany. “Unfortunately, there is no consensus on this issue on the European market. As soon as the situation has been clarified and a consensus found, we will comply with the outcome. For this reason, we have decided, as a temporary measure, to use R134a so as to dispel any possible concerns our customers might have.” Hard factual information about flammability tests on R1234yf are hard to find, though Dupont and Honeywell defend their product robustly. But sources at Daimler tell us that the company’s engineers were alarmed to find that in a frontal offset impact which punctured a car’s air-con system, R1234yf caught fire when it was released close to hot engine parts such as the turbocharger and exhaust manifold. Combustion of butane in R1234yf then apparently leads to emissions
of highly toxic gases when it burns. Other vehicle manufacturers are reported to have tried and failed to replicate the Daimler tests. But Daimler nevertheless is sticking to its guns, arguing that the risk is simply unacceptable. And some other car-makers, including Volkswagen and BMW, seem to be having second thoughts about the wisdom of a wholesale switch from R134a to R1234yf. VW appears still to favour R744 (carbon dioxide) in principle, though long-running efforts to adopt it as an industry standard replacement for R134a ended about three years ago, seemingly on the basis of cost, durability, and failure to satisfy US Environmental Protection Agency restrictions. The main worry is that carbon dioxide, exhaled by human respiratory systems, may make drivers drowsy in concentrations above three per cent. This is why the EPA insists that R-744-based aircon systems would have to ensure that short-term exposure (15 minutes or more) never gets as high as four per cent, including the CO2 being exhaled by a vehicle’s occupants. Meanwhile R-744 continues to gain traction as the possible refrigerant gas of the future for use in truck and trailer systems, where the risk of unacceptable CO2 concentrations in confined spaces is much less. Ringing alarm bells: fires like this are what Daimler sees as the unacceptable risk of the new refrigerant gas.
News Ingersoll Rand group subsidiary Thermo King, with European operations based in Galway, Ireland, is one of the best-known names in the temperature-controlled sector and was one of the first to see the potential for R-744. The Thermo King product which came second in the “environment” category of the pan-European Trailer Innovation 2011 awards is the CT-15 Spectrum, described as a “zero-emissions cryogenic multi-temperature trailer unit that utilises the highlyinnovative and patented CryoTech cooling system.” Mention of “cryogenic” refrigeration (meaning simply in essence a substance for producing low temperature) may remind some seasoned truck operators of the ill-fated Polarstream, liquid-nitrogenbased “cryogenic” system used on BOC trucks of old in the UK. Environmental factors associated mainly with fuel consumption and the noise of the diesel engines that power most trailer refrigeration units nowadays certainly have led to increased interest in alternatives working on the same general, nitrogeninjection principle as the old Polarstream system. But Thermo King is at pains to explain how its CT-15 Spectrum system is different. The use of carbon dioxide (CO2) classified as R-744 refrigerant, is key. Thermo King marketing manager Samvit Dutta points out that CO2 is a common waste by-product of various industrial manufacturing processes such
as fertiliser production and oil refining. Liquid nitrogen takes three times more energy to produce, it is argued. “The secret behind our CryoTech units is the use of recycled liquid R-744 as a coolant in an open-circuit system,” says Dutta. “While this is not the only cryogenic solution currently available, it is highly innovative as it provides airflow in the loadspace, which is essential for fresh produce. Also it exhausts the cryogen outside the loadspace, ensuring that no R-744 enters the cargo area.” With the old Polarstream system, and even with more modern ones of similar general type, coolant is injected into the cargo area, displacing oxygen. As Thermo King points out, “such systems require complex safety mechanisms and gasextraction equipment to protect operators.” This is claimed to “inevitably delay loading and unloading while the gas is removed and the area becomes safe to enter.” The absence of any diesel engine, compressor and other heavy components in the “host unit” of a CryoTech system makes it compact and light by comparison with conventional, diesel-powered trailer refrigeration systems. A CT-15 “host unit” weighs only 145kg, compared with about 845kg for a typical diesel-engined, nosemounted reefer. Now Thermo King arch-rival Carrier Transicold, part of the huge United Technologies Corporation, has introduced its own trailer refrigeration system using R-744 as the refrigerant gas. The system is called
Trying something different: Sainsbury’s has started a two-year trial of a Carrier trailer refrigeration unit using caron dioxide as the refrigerant gas.
NaturaLine and was developed originally for deep-sea containers. A trial of the container system ended last year. This month comes the official announcement in London of the start of a twoyear trial in the Sainsbury’s supermarket fleet of a tandemaxle, 10.8-metre Gray & Adams reefer semi-trailer fitted with the Carrier NaturaLine system. “This is the very first time that our NaturaLine system has been mounted to a box trailer anywhere in the world,” says Carrier Transicold president David Appel. “It’s a fantastic opportunity to advance Carrier’s natural leadership in environmental technologies, by working closely with Sainsbury’s, one of our largest customers in Europe, to test how the concept performs on the road. It’s also much better
news for the environment because natural refrigerant CO2 is non-ozone depleting and has a global warming potential of one.” Sainsbury’s thinks the Carrier system could help with its overall aim to cut CO2 emissions from its depot-to-store logistics operation by 35 per cent by 2020, against a 2005 baseline. “The new carbon dioxide technology has much less of an impact on climate change and we hope it will play a big part in helping us reduce our carbon emissions,” says Nick Davies, head of the supermarket chain’s transport operations. “We will be monitoring its performance closely and if successful, in line with our replacement plan, it could help us save over 70,000 tonnes of CO2 compared to the current refrigerated trailer fleet.” K
September 2013 Commercial Vehicle Engineer
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