Walid Chakroun - ASHRAE - REFRIGERANTI E LORO USO RESPONSABILE
Refrigerants and their Responsible UseASHRAE Position DocumentTHE LATEST TECHNOLOGY IN AIR CONDITIONING AND REFRIGERATION INDUSTRYENERGY ISSUES AND CLIMATE CHANGENEW REFRIGERANTS, NEW EUROPEAN REGULATIONS AND CERTIFICATIONS,MOBILE AIR CONDITIONING AND REFRIGERATED TRUCKSPolitecnico of Milan 7th- 8th June 2013Walid ChakrounASHRAE
ContentsWhat is ASHRAE Position DocumentRefrigerants OverviewAlternative TechnologiesIssues for Considerations
ASHRAE Position DocumentASHRAE position documents areapproved by the Board of Directors andexpress the views of the Society.
Definition“Refrigerants are the working fluids inrefrigeration, air-conditioning, and heat-pumpingsystems. They absorb heat from one area, such asan air-conditioned space, and reject it intoanother, such as outdoors, usually throughevaporation and condensation, respectively.”
Where Are We NowHFCs are greenhouse gases and the value of GWP quantifies thiseffect on global warming-- In some applications, the “indirect” effectof producing energy is much greater than the GWP effect of therefrigerant itself.Total equivalent warming impact (TEWI)--include both direct andindirect impacts of refrigeration systems--Life cycle climatePerformance LCCPUnder the Kyoto Protocol, no specific mandates for reductions orphase out of the HFCs -European Union enacting regulations on HFCs--F-Gas Legislation-Some countries went even beyond by proposingan amendment to the Montreal Protocol to start phasing down HFC.These developments led to renewed and increased interest in naturalrefrigerants and the development of new low-GWP options.
Present FactsThe process of switching to Low GWP is moving at different speedsaround the world—Challenges for High Ambient Temperature countriesRefrigerants selection and their operating systems still not based on aholistic analysis of multiple criteria- energy efficiency, systemperformance, potential impact on community safety, risk to personalsafety, cost, and minimization of direct and indirect environmentalimpacts.Some HFOs are available in limited quantities, Not yet fully tested in allapplications. Some HFOs and lower-GWP HFCs have mild flammabilityand cost is high.No ideal refrigerant yet. Natural refrigerants, the HFCs, the unsaturatedHFCs (also known as HFOs), and possibly blends will continued to beused.
Challenges- High Ambient Temperature(TEAP, 2012) High ambient temperatures lead to high condensing temperatures andpressures.—Consequences COPs drops 20%- 25%. Constrains in high discharge temperature and pressure lead to the choice of“medium pressure” refrigerant such as HFC-134a or HFC-1234yf for singlestage systems. Lack of low-GWP refrigerants with a large refrigeration capacity in order toreplace R-404A or HCFC-22 in single stage refrigeration systems.
Alternative Technologies Which refrigerant to use :-The answer is very size and application dependent.-Selection of the correct refrigerant requires: capitalcost, operating cost (including energy andmaintenance), equipment size and location, operatingtemperatures/pressures, facility staff capability andlocal, national, and international regulations.
CO2 TechnologyPressures in CO2 systems are approximately ten timeshigher than those in ammonia—special equipmentdesigns-different manufacturing process-high costHigh pressure results in high gas density, allows fargreater refrigerating effect to be achieved from a givencompressor.-cost effective for smaller products that requires highpressure rating.At low temperatures (-30 to -50 oC), CO2 produces verysmall reductions in saturation temperature for a givenpressure drop allowing higher mass flux in evaporatorsand suction pipes without efficiency penalties.--
Hydrocarbon TechnologyHydrocarbon refrigerants have excellent environmental,thermodynamic, and thermo-physical properties, howeverthey are highly flammable.Hydrocarbon refrigerants provide a range of boiling pointswith applicability from cryogenics to air conditioning.Mostly used in European and Asian countries, used withcommercial refrigeration systems including beverage andice-cream machines, Transport refrigeration systems fortrucks, Chillers in the range 0.3 – 40 tons of refrigeration
Ammonia TechnologyReadily available inexpensive, operates at pressurescomparable with other refrigerants, absorb large amountsof heat when it evaporates, zero ODP, Zero GWP, lowTEWI.Ammonia has a low boiling point (-28°F @ 0 psig), highlatent heat of vaporization (nine times greater than R-12).Ammonia is toxic effect at higher concentrations (i.e. =above 300 ppm)-self -alarming odor, easy to repair leaks,lighter than air.Ammonia’s use in the HVAC&R industry should beexpanded as regulatory and code officials becomeinformed of its relative safety.
Ammonia TechnologyBarriers to expanding its use must be addressed:-Some real and perceived, generally relate to humanhealth and environmental safety, and system installation-Continue research on topics such as handling,application, operation, control of emissions and newtechnology.-Maintain and develop standards and guidelines forpractical and safe application of ammonia in refrigerationsystems.
Questions Remain open Issues with natural refrigerants include flammability, toxicity, high pressures, or, in some cases,lower operating efficiencies Concern about the high GWP of some HFCs ---calling to reduce it. Research to extend lower-GWPHFCs into new applications. The reduction has been proposed as a phase-down of HFC’s, however no country has formallyadopted a proposal nor is it currently included in either the Kyoto or the Montreal Protocols. At the present time, some hydrofluoroolefins (HFOs) are available in limited quantities, but they arenot yet fully tested in all applications. In addition, some HFOs and lower-GWP HFCs have mildflammability. Research is also investigating blends across these refrigerant classes to identify combinations thatmay optimize performance and minimize negative aspects. End-of-life disposal of refrigeration and air-conditioning systems is another important issue. At thattime, refrigerant should be recovered and recycled or disposed of safely to prevent loss of the chargeto the atmosphere.
Research Recommendations balancing the safety, energy efficiency, cost, and environmental impact forrefrigerants using a consistent and comprehensive methodology across allrefrigerants and system types using benchmarks like LCCP, life cycleassessment (LCA) or TEWI advancing the design and development of refrigeration and air conditioningequipment that facilitate reduced refrigerant emissions developing methodologies and practices to minimize or prevent refrigerantloss during installation, operation, maintenance, and decommissioning ofrefrigeration systems developing new refrigerants that minimize environmental impacts and safetyconcerns