ASHRAE-D-AJ10AprIC-20100331.pdf

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7 4 A S H R AE J o u r n a l A p r i l 2 0 1 0

Propane Replacing R-22By Karin Jahn, Ph.D.

ccording to the International Institute of Refrigeration, 1 20% of the global warming potential of refrigerating

and air-conditioning systems comes from leaks (directemissions), while 80% results from their energy consumption(indirect emissions). Today’s refrigeration systems consumearound 15% of the world’s available electrical energy. Reducingtheir energy demand would make an important contribution toreducing the threat of global warming.

In this context, special importance is attributed to naturalrefrigerants such as ammonia, carbon dioxide and hydrocarbons,which offer high energy efciency as well as being climate-neutral. Expert opinion recognizes ammonia as the most ef-cient refrigerant. But hydrocarbons such as propane, propeneand isobutane also have outstanding thermodynamic properties;refrigerating and air-conditioning systems that run on theserefrigerants are particularly energy-efcient. Companies suchas Ben & Jerry’s, Pepsi and Unilever use hydrocarbons forrefrigeration in their chilling units and freezers. Various testsin the eld have conrmed energy savings between 10% and30% compared to HFC systems.

In addition, certain hydrocarbons also can be used as a “drop-in solution” for synthetic refrigerants. For example, propane(R-290) and propene (R-1270) have similar thermodynamicbehavior to R-22. They use the same technology, which meansthat many of the existing installed components are compatible.For higher ambient temperatures or higher humidity levels,propane and propene are more efcient than R-22.

Making AC Systems Environment-Friendly The Chinese air-conditioning system manufacturer Gree

Electric Appliances is using propane to replace R-22 and R-410A in new systems. The company is one of the world’s largestmanufacturers of room air conditioners with a production outputof more than 70 million units a year. The Chinese use R-22 asa standard refrigerant, with China’s air-conditioning systemsgenerating annual HCFC emissions amounting to 260 milliontons of carbon dioxide equivalent, constituting one of China’slargest source of emissions.

In 2009, Gree, assisted by the implementing agency GTZProklima, started pilot production of room air-conditioning sys-tems based on propane. The quantity of refrigerant ranges from200 to 350 grams (0.44 to 0.77 lbs) for rated cooling capacitiesof 2 kW to 4 kW, depending upon the model. Signicantly, theair-conditioners have a higher efciency than R-22 and R-410Amodels, while requiring a smaller mass of system materials.

In addition to the reduced charge size, GTZ Proklima withUK-based consultant Daniel Colbourne, assisted with the safedesign of the air conditioners. A production line will turn out180,000 systems per year. The changeover in refrigerant willsave 560,000 tons of carbon dioxide equivalents in direct emis-sions over the entire service life of the air-conditioning systems.

To this should be added a further 320,000 tons of carbon dioxideequivalents in indirect emissions saved by the improved energyefciency of the systems. For the nal consumer, this benetsin terms of lower electricity bills.

The best project practice, which is intended to have a role-model effect for China’s entire air-conditioning industry andbeyond, is being funded by the German Federal Ministry for theEnvironment, Nature Conservation and Nuclear Safety withinthe framework of the International Climate Initiative based ona decision of the German Federal Parliament.

A

Delaying the Ripening of FruitCompanies in other industries are also

opting for hydrocarbons, such as the Brit-

ish fruit grower Manselds. The companystores apples and cherries in a controlledatmosphere so that they will be availablein top quality year-round regardless ofwhen they were picked. State-of-the-artmeasuring, control and refrigeratingsystems monitor temperature, humidity,oxygen and carbon dioxide levels, keep-ing them at the required level to delaythe ripening of fruit and vegetables.Manselds wanted an efcient, HFC-freerefrigeration system for the warehouse in

Chartham near Canterbury.

This article was published in ASHRAE Journal, April 2010. Copyright 2010 American Society of Heating, Refrigerating and Air-ConditioningEngineers, Inc. Posted at www.ashrae.org. This article may not be copied and/or distributed electronically or in paper form without permission

of ASHRAE. For more information about ASHRAE Journal, visit www.ashrae.org.

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7 6 A S H R AE J o u r n a l A p r i l 2 0 1 0

The refrigeration experts InternationalControlled Atmosphere Storage and SRSFrigadon designed a brine system usingpropene as the primary refrigerant. The

system was completed in 2008 withan output of 1,150 kW (327 ton). Fiveair-cooled factory-assembled packagescharged with a total of 90 kg (198 lb)of propene provide cooling capacity forthe secondary circuit at a temperature of–9°C (16°F). The special safe design ofthese chillers and a detailed safety analy-sis was provided by Re-phridge.

A brine mixture of water and salt isused as the secondary refrigerant. Thecircuit is lled with 30,000 L (7,925 gal-lons) and works at an operating pressureof only 1.5 bar to cool the heat transferuid down to –3°C (27°F). The brine ispumped to the 36 controlled atmospherecold storage rooms, which are kept at aconstant air temperature of –0.5°C and1.5°C (31°F to 35°F). The secondaryrefrigerant also cools the preparationand loading areas. The evaporators in

the warehouses are defrosted by off-cycle defrost. This entails interruptingthe refrigeration process so that thebrine absorbs heat from the ambient air,

which is used for defrosting. This methodprevents the products being cooled fromabsorbing unnecessary heat and savesenergy. The system design minimizes thequantity of refrigerant and guarantees aEuropean Seasonal Energy EfciencyRatio of more than 4.2, although based onlocal conditions the real seasonal coolingcoefcient of performance is around 6.

Supporting Biotechnological ResearchOne important process in the research

and production of biotechnological prod-ucts is freezing and defrosting substancesfor transport and storage. At the phar-maceuticals company Roche, this takesplace in tanks with a volume of 300 L(79 gallon), which are cooled down to–40°C (–40°F) in a cleanroom atmo-sphere. Here the company wanted anefficient refrigeration system to copewith fast changes in temperature between–50°C and 130°C (–58°F and 266°F)with an accuracy of ±1 K, with automaticdrainage and relling of the tank’s cooling

jacket. Furthermore, compliance with theRoche Environment Protection Guidelinesrestricted the choice of refrigerants tosubstances that do not damage the ozonelayer and the climate.

To meet these requirements, PeterHuber Kältemaschinenbau developed achiller that works with a small chargeof 1.8 kg propene. The core element ofthe system is a two-stage semi-hermeticreciprocating Bitzer compressor, whichis designed for use with propene. After

being brought down to a temperaturebetween –30°C and –60°C (–22°F and–76°F), the propene then cools the sili-cone oil circulating in the cooling jacket.

The output is 12 kW at a secondary refrig-erant outlet temperature of 0°C (32°F),and 6.5 kW at –40°C (–40°F).

The safety concept of the system sepa-rates the refrigeration circuits into severalsections so that in the event of a burstpipe, any refrigerant leak is limited tothe affected section rather than the com-

plete charge. Additional components in

the refrigeration system, commissionedin 2006, include a plate heat exchangeracting as evaporator, a water-cooledcoaxial condenser and a Modbus-based

control unit. As Safe as Refuelling Stations

“The case studies show that non-halogenated hydrocarbons are suitablefor reliable refrigeration in many differentbranches,” says Monika Witt, chair ofeurammon, the European initiative fornatural refrigerants.

However, certain requirements haveto be met when using these substances.Potential sources of ignition have to beidentied and eliminated early duringthe planning phase. The systems haveto be designed so as to avoid leaks:this includes reducing the number of

joints and applying permanent corro-sion protection. As far as possible, therefrigeration system should be installedon the roof or equipped with a gas detec-tion and ventilation system so that thegas can be exhausted in the event of aleak. Components containing refriger-ant must be clearly marked as such sothat service technicians are informedaccordingly and can take correspondingprecautions. Good initial and advancedstaff training plays a crucial role, as faultymaintenance is one of the greatest riskswhen operating refrigeration systemswith hydrocarbons.”

But even if the ammability of hydro-carbons pose the greatest challenge, thesesubstances can still be handled safely, asdemonstrated every day in thousands ofrefuelling stations all over the world.”

References1. Dupont, J.L. 2007. “Improving energyefciency in refrigeration.” Presentation atthe Regional Ozone Network for Europe andCentral Asia, Ashgabat, Turkmenistan.

Kar in Jahn, Ph.D., i s managing di - rector for eurammon, a joi nt Europeaniniti ative of companies, institutions andindividuals who advocate an increaseduse of natural refri gerants.

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