Purdue University
`Purdue e-Pubs
`International Refrigeration and Air Conditioning
`Conference
`
`School of Mechanical Engineering
`
`2008
`
`HFO-1234yf Low GWP Refrigerant Update
`
`Barbara Minor
`DuPont Fluoroproducts
`
`Mark Spatz
`Honeywell International
`
`Follow this and additional works at: http://docs.lib.purdue.edu/iracc
`
`M nor Barbara and Spatz Mark "HFO 1234yf Low GWP Refr gerant Update" (2008). International Refrigeration and Air Conditioning
`Conference. Paper 937.
`http://docs.l b.purdue.edu/ racc/937
`
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`Arkema Exhibit 1010
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`
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`Barbara MINOR1*, Mark SPATZ2
`
`1DuPont Fluoroproducts,
`Wilmington, DE, USA
`Phone: 302-999-2802, E-mail: barbara.h.minor@USA.DuPont.com
`
`2Honeywell International,
`Buffalo, NY, USA
`Phone: 716-827-6238, E-mail: mark.spatz@Honeywell.com
`
`ABSTRACT
`
`HFC-134a has been scheduled for phase-out in automobiles in the European Union beginning January 1, 2011.
`HFO-1234yf has been identified as a new low global warming refrigerant which has the potential to be a global
`sustainable solution for automotive air conditioning. HFO-1234yf is a pure compound which is highly energy
`efficient, exhibits low toxicity in testing to date, and can potentially be used in systems currently designed for R134a
`with minimal modifications. Life Cycle Climate Performance (LCCP) calculations also indicate a significant
`environmental benefit versus R134a, R152a and CO2 (R-744) in all major regions of the world. Though HFO-
`1234yf is mildly flammable per ASTM E-681-04 (ASTM, 2004), it is significantly less so than HFC-152a and HFC-
`32 and has the potential to be used in direct expansion systems without a secondary loop. In this paper, an update
`will be provided on recent status of HFO-1234yf evaluations.
`
`1. INTRODUCTION
`
`Due to increased pressure to address the issue of global warming, the European Commission has effectively banned
`the use of R-134a refrigerant in air conditioning in new car platforms in EU countries starting January 1, 2011. R-
`134a has a 100 year global warming potential value (GWP) of 1430 according to the Intergovernmental Panel on
`Climate Change 4th Assessment Report (AR4). Replacement refrigerants must have a GWP less than 150. Until
`recently, the leading candidate to replace R-134a has been carbon dioxide with a GWP of 1. However, CO2 has
`several drawbacks including significantly higher pressure and lower thermodynamic cycle efficiency. These
`properties necessitate significant design changes to be able to use CO2 with associated higher cost equipment,
`reliability questions, and other transition costs such as system maintenance, tools, and training.
`
`HFO-1234yf was recently identified as a potential alternative that has vapor pressure and other properties similar to
`R-134a, but a 100 year GWP of 4 which meets the EU regulation requirements. It also has zero ozone depletion
`potential and excellent Life Cycle Climate Performance (LCCP) compared to R-134a and CO2 which indicates it has
`the least overall impact on global warming in automotive air conditioning applications. Following is a review of
`properties and performance of HFO-1234yf.
`
`2. THERMODYNAMIC PROPERTIES
`
`HFO-1234yf thermodynamic properties are very similar to R-134a as shown in Table 1 and Figure 1. Boiling point,
`critical point, and liquid and vapor density are comparable to R-134a. Vapor pressure is slightly higher at
`temperatures below 25°C and slightly lower at temperatures above 60°C which can yield a lower compression ratio
`and better compressor efficiency.
`
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`Table 1: HFO-1234yf Thermodynamic Properties
`Properties
`HFO-1234yf HFC-134a
`Boiling Point, Tb
`-29°C
`-26°C
`Critical Point, Tc
`95°C
`102°C
`Pvap, MPa (25°C)
`0.677
`0.665
`Pvap, MPa (80°C)
`2.44
`2.63
`Liquid Density, kg/m3 (25°C)
`1094
`1207
`Vapor Density, kg/m3 (25°C)
`37.6
`32.4
`
`R-134a
`HFO-1234yf
`
`3.5
`
`3
`
`2.5
`
`2
`
`1.5
`
`1
`
`0.5
`
`Pressure (MPa)
`
`0
`
`-40
`
`-20
`
`0
`
`40
`20
`Temperature (C)
`
`60
`
`80
`
`100
`
`Figure 1. HFO-1234yf and R-134a Vapor Pressure
`
`3. TOXICITY
`
`Significant toxicity testing for HFO-1234yf has been completed following Organization for Economic Cooperation
`and Development (OECD) guidelines. The toxicity profile to date is shown in Table 2 below. All acute toxicity
`testing has been completed, as well as a 13 week inhalation study and rat developmental testing with very promising
`results. Although an Ames test showed slight activity, subsequent in vitro testing, including mouse and rat
`micronucleus and unscheduled DNA synthesis showed no activity indicating HFO-1234yf is not mutagenic.
`Environmental tests on daphnia, fish and algae results are also similar to R-134a.
`
`Test
`LC50
`Cardiac Sensitization
`
`Table 2: HFO-1234yf Toxicity and Environmental Summary
`HFO-1234yf
`No deaths 400,000 ppm
`NOEL > 120,000 ppm
`
`R-134a
`No deaths 359,700 ppm
`NOEL 50,000 ppm
`LOEL 75,000 ppm
`Not active
`Not active
`Not active
`Not tested
`NOEL 50,000 ppm
`NOAEL 50,000 ppm
`NOEL > 100 mg/L
`
`Ames
`Chrom AB
`Micronucleus (mouse and rat)
`Unscheduled DNA Synthesis
`13 Week Inhalation
`Developmental (Rat)
`Environmental Tox (acute daphnia,
`fish, algae)
`
`Slight activity
`Not active
`Not active
`Not active
`NOEL 50,000 ppm
`NOAEL 50,000 ppm
`NOEL > 100 mg/L
`
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`4. ENVIRONMENTAL
`
`2349 Page 3
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`HFO-1234yf atmospheric chemistry has been evaluated experimentally (Nielsen et al. 2007). HFO-1234yf has no
`ozone depletion potential. Atmospheric lifetime was determined to be 11 days versus R-134a at 14 years. Global
`warming potential based on a 100 year time horizon was determined to be 4 versus R-134a at 1430. Atmospheric
`breakdown products are also very similar to R-134a with no high GWP breakdown products formed.
`
`5. FLAMMABILITY
`
`HFO-1234yf was determined to be flammable by exhibiting lower and upper flammability limits when tested using
`ASTM-E681-04. However, results indicate mild flammability when comparing the lower flammability limit versus
`other refrigerant candidates as shown in Table 3. Also, flammability limits are only one factor in determining
`whether HFO-1234yf can be safely used in a given application. Another important consideration is the amount of
`energy that is required to ignite the refrigerant, represented by the minimum ignition energy, and the damage
`potential if an ignition were to occur, represented by the burning velocity.
`
`5.1 Laboratory Flammability Measurements
`Of the relevant comparisons shown in Table 3 below, HFO-1234yf has the smallest gap between lower and upper
`flammability limits, indicating a smaller flammable envelope which reduces the likelihood an ignition will occur.
`Minimum ignition energy (MIE) was determined using ASTM E-582 (ASTM, 2007) which employs a 1 liter vessel
`and metal electrodes to generate a spark up to 1000 mJ. Propane and R-152a have very low MIEs, meaning a larger
`number of ignition sources could potentially ignite these refrigerants. Since R-32, ammonia, and HFO-1234yf are
`slower burning materials, a 1 liter vessel was determined to be too small to test these refrigerants because
`interference of the vessel wall can quench the flame. Therefore these refrigerants were retested in a 12 liter vessel.
`At 5,000 mJ there was no ignition of HFO-1234yf, and at 10,000 mJ an ignition occurred. This is significantly
`higher than R-32 which ignites between 30 and 100 mJ and ammonia between 100 and 300 mJ, although these are
`considered mildly flammable refrigerants. These results indicate there will be fewer potential ignition sources for
`HFO-1234yf.
`
`Finally, burning velocity gives an indication of the potential damage which could be caused if an ignition were to
`occur. HFO-1234yf was recently tested in a spherical vessel (Takizawa 2007) and the burning velocity at room
`temperature was determined to be 1.5 cm/s. This is a very low value compared to propane and R-152a and less than
`R-32 and ammonia indicating that HFO-1234yf has low potential for damage should an ignition occur. These
`flammability results are being used as input to risk assessments to confirm HFO-1234yf is safe to use in direct
`expansion systems without a secondary loop. Also, a spark ignition test also was conducted using a 12-volt car
`battery hooked up to electrodes in a 12 liter vessel containing HFO-1234yf /air mixtures between 8-9% (most
`ignition sensitive range). Sparks were generated from a the 12-V battery short at 20, 60, or 80°C. There was no
`ignition of HFO-1234yf. However, for comparison, a 20 vol % ammonia/air mixture was tested and ignited at both
`20 and 60°C.
`
`Table 3: HFO-1234yf Flammability Summary
`Propane R-152a
`R-32
`
`
`Property
`Flame Limits (ASTM E681-04) at 21°C
` LFL (vol% in air)
` UFL (vol% in air)
` Delta UFL-LFL
`Minimum Ignition Energy (mJ)
`Burning Velocity (cm/s)
`
`
`
`
`
`NH3
`
`HFO-1234yf
`
`
`
`
`
`2.2
`10.0
`7.8
`0.25
`46
`
`3.9
`16.9
`13.0
`0.38
`23
`
`14.4
`29.3
`14.9
`30-100
`6.7
`
`15.0
`28.0
`13.0
`100-300
`7.2
`
`6.2
`12.3
`5.8
`5,000-10,000
`1.5
`
`5.2 Automotive Mockup Flammability Testing
`A mockup has been constructed to measure the time varying local refrigerant concentration for the 0.5 mm corrosion
`hole (worst case corrosion type) and ruptured line scenarios. The mockup was constructed to simulate these
`scenarios for the case of a 2.5 m3 passenger compartment representative of a typical European size automobile.
`
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`Figure 2(a) shows the interior dimensions of the mockup, while Figure 2(b) indicated the position of the diflerent
`ignition locations used in the study: vent, floor and breath.
`
`2349 Page 4
`
`
`
`WidhiiIIl§Iih'hEiI|
`
`I,54m
`
`(b)
`(a)
`Figure 2. Dimensions and locations of ignition sources
`
`The flammability testing used two ignition types: a butane torch representing a high power cigar lighter and a MIG
`arc welder with approx. electrical discharge of 1.5 kW used without shielding gas. The settings for the flammability
`tests are:
`
`Blower setting — low, blower inlet damper adjusted for 60 CFM output
`Air velocity exiting vents: 1.7 m/sec
`HVAC Mode: 100% recirculation of air inside mock-up.
`Temperature — approximately 22 °C
`Rupture Line leak rate — 12 g/s (deviations: 1 1 to 14 g/sec)
`0.5 mm corrosion leak — 1.4 g/s (deviations: 1.4 to 1.7 g/sec)
`
`A series of tests were conducted that depicted an ever decreasing likelihood that this event will occur. As shown in
`Table 1. the most likely type of evaporator leak is one from a small diameter hole. Even with a large corrosion leak
`emanating from a 0.5mm diameter hole that would represent only 1% of evaporator leaks, both CFD modeling and
`experimental results show that concentrations inside the passenger compartment never reach the LFL. It was decided
`to run tests with this leak as well as the much less likely tube rupture leak with various ignition sources. sequences,
`and locations. The results of the series of flammability tests that were conducted in the mock-up are shown in Table
`4.
`
`Table 4. Results of Mockup Flammability Tests.
`
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`1) Large Corrosion Leak (0.5 mm diameter) — flammability tests 1 and 3 were conducted at the vent outlet and
`breath locations with the butane lighter. No flame extension or any other propagating flame was seen in any
`of the tests for this scenario. One observation made was that the flame color changed from orange to a blue.
`Figure 3. This phenomenon is the same as the older halide torch leak detectors used by the industry. Test 2 was
`conducted to simulate a leak into the passenger compartment with the blower shut—off allowing the refrigerant
`to pool. To simulate a short of a battery that was installed under the front seat. an arc welder positioned on the
`floor was activated. Again no ignition took place.
`
`2349 Page 5
`
`
`
`Figure 3. Butane lighter in 0.5 mm Corrosion Leak Test
`
`2) Ruptured Line Leak — flammability tests 4 thru 9 were conducted to simulate the ruptured tube event.
`Tests 4 and 7 were conducted at both the breath level to simulate a cigarette lighting location and for a
`worst case location (area of highest concentration) at the vent outlet with the butane lighter. Results — as the
`HFO-l234yf concentration increased the butane lighter became inoperable: operation of the butane lighter
`was not again possible until the local refrigerant diflilsed to lower concentrations. It is currently postulated
`that the inclusion of HFOl234yf raised the butane/HLFOl234yf minimum ignition energy above the energy
`release for the lighter‘s sparker. When the local concentration dropped. lighter operation was again
`possible. The flame behaved as in the corrosion leak test.
`Elevated Temperature (45 °C) — tests with the butane lighter were also conducted at an elevated
`cabin temperature of 45 °C. The operation of the lighter and the flame are the same as the room
`temperature tests.
`
`Tests 5 and 6 utilize an arc welder Without shielding gas which was placed on the floor of the moclrup (test
`5) to simulate a shorting battery connection. or shorts in the electrical seat motor or heater. The welder was
`also placed at the vent outlet location (test 6) to simulate an HVAC module short (the concentration at the
`vent outlet is assumed to be the same as the interior of the HVAC module interior). The videos from the
`arc welder are very dramatic with sparks flying about the cabin. however. No detectable flame was
`evident. Figure 4 show stills from the video capture.
`
`
`
`Figure 4. Electrical Arc Welder located at the vent outlet and floor location
`
`Extraordinary measures had to be taken to achieve ignition of I-IFO-l234yf even with the worst possible leak
`scenario of the ruptured tube. Tests 8 and 9 were conducted to overcome the issue of the failure of the lighter to light
`
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`2349 Page 6
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`in areas of higher HFO-1234yf concentrations. The extraordinary steps taken to carry out these tests show that the
`likelihood of ignition of HFO-1234yf is quite remote.
`
`6. MATERIALS COMPATIBILITY
`
`6.1 Thermal Stability
`HFO-1234yf has been evaluated for thermal stability per ASHRAE Standard 1997-99 (ASHRAE, 1999). Tests were
`conducted with refrigerant and either polyalkylene glycol (PAG) or polyolester (POE) lubricant and water
`concentrations varying from less than 100 ppm to 10,000 ppm. Refrigerant and lubricant were placed in sealed glass
`tubes containing aluminum, copper and carbon steel coupons and held at 175°C or 200°C for two weeks. Results
`indicate HFO-1234yf is thermally stable with no significant corrosion to the metals observed.
`6.2 Plastics and Elastomers Compatibility
`HFO-1234yf and R-134a have been evaluated for compatibility with typical plastics and elastomers used in
`automotive air conditioning systems. Some commonly used plastics and elastomers were immersed in sealed tubes
`containing HFO-1234yf and PAG lubricant and held at 100°C for two weeks. Plastics were then inspected for
`weight change after 24 hours and physical appearance. Elastomers were evaluated for linear swell, weight gain and
`hardness using a durometer. The results of specific plastics and elastomers that were tested are shown in Tables 5
`and 6. HFO-1234yf has very similar behavior with plastics and elastomers compared to R134a, indicating that many
`materials in use in current air conditioning systems may be compatible with HFO-1234yf.
`
`Refrigerant
`HFO-1234yf
`"
`"
`"
`"
`
`Refrigerant
`R-134a
`"
`"
`"
`"
`
`Table 5: HFO-1234yf Plastics Compatibility
`Plastics
`Rating 24 h Post Weight Chg. % Physical Change
`Polyester
`1
`4.4
`0
`Nylon
`1
`-1.5
`1
`Epoxy
`1
`0.3
`1
`Polyethylene Terephthalate
`1
`2.0
`0
`Polyimide
`0
`0.2
`0
`
`
`
`
`Plastics
`Rating 24 h Post Weight Chg. % Physical Change
`Polyester
`1
`5.6
`0
`Nylon
`1
`-1.4
`1
`Epoxy
`1
`0.3
`1
`Polyethylene Terephthalate
`1
`2.8
`0
`Polyimide
`0
`0.7
`0
`
`The following ratings were used to assess changes to plastics: Rating = 0 if weight gain is less than 1% and there is
`no physical change. Rating = 1 if weight gain is between 1 and 10% and physical change = 2.
`
`Refrigerant
`
`HFO-1234yf
`"
`"
`"
`"
`"
`
`
`Table 6: HFO-1234yf Elastomers Compatibility
`24 h Post Linear
`24 h Post Weight
`Elastomers Rating
`Swell %
`Gain %
`Neoprene
`0.0
`-0.3
`WRT
`HNBR
`1.6
`5.5
`NBR
`-1.2
`-0.7
`EPDM
`-0.5
`-0.6
`Silicone
`-0.5
`2.5
`Butyl rubber
`-1.6
`-1.9
`
`
`
`
`0
`0
`0
`0
`1
`0
`
`
`24 h Post Delta
`Hardness
`1.0
`-7.0
`4.0
`4.0
`-14.5
`0.5
`
`
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`Refrigerant
`
`R134a
`"
`"
`"
`"
`"
`
`Table 6 (cont): HFO-1234yf Elastomers Compatibility
`24 h Post Linear
`24 h Post Weight
`Elastomers Rating
`Swell %
`Gain %
`Neoprene
`-0.6
`-1.3
`WRT
`HNBR
`2.1
`8.6
`NBR
`0.0
`3.0
`EPDM
`-1.1
`-0.4
`Silicone
`-1.4
`1.4
`Butyl rubber
`-1.1
`-1.6
`
`0
`0
`0
`0
`0
`0
`
`2349 Page 7
`
`24 h Post Delta
`Hardness
`2
`-5.5
`-3.5
`-2
`-2.5
`-3.5
`
`For elastomers, Rating = 0 if for < 10% weight gain, < 10% linear swell and < 10% hardness change. Rating = 1 for
`> 10% weight gain or > 10% linear swell or >10% hardness change.
`
`7. SYSTEM PERFORMANCE
`
`System performance was measured in a bench scale apparatus using mobile air conditioning components from a
`small car. The fully instrumented bench system was constructed in an environmental chamber to allow control of
`temperature and humidity. Baseline tests for R-134a were conducted and the refrigerant was replaced with HFO-
`1234yf. No other system changes were made, including no adjustment to the thermostatic expansion valve (TXV).
`The test matrix covered the range of automotive vehicle operation and are defined in currently proposed SAE
`standard (SAE J2765).
`
`Results for cooling capacity and energy efficiency relative to R-134a are shown in Figure 5. Results show that with
`no system changes, the cooling capacity and energy efficiency is within 4-8% of R-134a. Significant improvements
`can be expected with minor system optimization, such as TXV adjustment and larger diameter suction line tubing.
`
`Capacity COP
`
`120%
`110%
`100%
`90%
`80%
`70%
`60%
`50%
`40%
`30%
`20%
`10%
`0%
`
`charge
`H15-10C
`H15-3C
`M15-10C
`M15-3C
`L15-10C
`L15-3C
`I15-10C
`I15-3C
`I30-10C
`I30-3C
`H25a-10C
`H25a-3C
`M25a-10C
`M25a-3C
`L25a-10C
`L25a-3C
`I25a-10C
`I25a-3C
`I40a-10C
`I40a-3C
`I40c-10C
`I40c-3C
`H35a
`M35a
`L35a
`I35a
`I50a
`H45
`M45
`L45
`I45
`
`Figure 5. Bench Cooling Capacity and COP for HFO-1234yf Relative to R-134a
`
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`2349 Page 8
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`8. LIFE CYCLE CLIMATE PERFORMANCE
`
`Life cycle climate performance, (LCCP) has been used quite extensively in the mobile air conditioning industry and
`has become a useful tool to understand total product environmental impact beyond the direct global warming
`potential (GWP) of the refrigerant. This is a cradle-to-grave analysis of the environmental impact at all points in the
`life cycle chain, including manufacture of components, system operation and end-of-life disposal. The GREEN-
`MAC- LCCP® 2007 model was used as the basic foundation for this analysis. Although there are several other
`models available for automotive LCCP calculations, this model was chosen for its robustness and volume of data
`available. Data from the bench scale tests described in Section 7 were used as inputs to the model to calculate
`LCCP values for HFO-1234yf versus R-134a in several locations including cooler and warmer climates. Results in
`Figure 3 show an LCCP reduction of 15% on average for the transition from R-134a to HFO-1234yf, and up to 27%
`reduction in part of Europe. There was an LCCP reduction in every geographic location evaluated.
`
`100
`
`95
`
`90
`
`85
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`50
`
`CO2 Eq. Emmission Relative to R-134a
`
`Houston
`Phoenix
`
`Boston
`
`Frankfurt
`Miami
`
`Athens
`
`Sydney
`Tokyo
`Bombay
`Sapporo
`Kagoshima
`Bangalore
`New Dehli
`
`Shanghai
`Beijing
`
`Figure 3: LCCP For HFO-1234yf Relative to R-134a
`
`9. CONCLUSIONS
`
`HFO-1234yf has excellent potential as a new low global warming refrigerant for automotive air conditioning and
`potentially for stationary applications. It has excellent environmental properties which can have a long term
`favorable impact on climate change and meet current and future climate regulations. Significant toxicity tests have
`been completed with encouraging results. It is compatible with existing R-134a technology which can allow for a
`smooth and cost effective transition. The mild flammability properties of HFO-1234y have shown its high potential
`for use in direct expansion applications, pending completion of risk assessments.
`
`10. REFERENCES
`
`ASHRAE Standard 97-99, 1999, “Sealed Tube Thermal Stability Test”. American Society of Heating, Refrigerating,
`and Air-Conditioning Engineers, Inc., Atlanta, GA.
`ASTM E582-07, 2007 "Standard Test Method for Minimum Ignition Energy and Quenching Distance in Gaseous
`Mixtures” American Society for Testing and Materials (ASTM), West Conshohocken, PA.
`ASTM E681-04, 2004 "Standard Test Method for Concentration Limits of Flammability of Chemicals (Vapors and
`Gases)," American Society for Testing and Materials (ASTM), West Conshohocken, PA.
`GREEN-MAC-LCCP© model 2007. www.epa.gov/cppd/mac/.
`Nielsen, O.J. et al., 2007 “Atmospheric Chemistry of CF3CF=CH2”, Chemical Physics Letters, vol. 439, p. 18-22.
`
`International Refrigeration and Air Conditioning Conference at Purdue, July 14-17, 2008
`
`DISCLAIM ER
`Although all statem ents and inform ation contained herein are believed to be accurate and reliable, they are presented w ithout
`guarantee or warranty of any kind, expressed or im plied. Inform ation provided herein does not relieve the user from the responsibility
`of carrying out its own tests and experim ents, and the user assum es all risks and liability for use of the inform ation and results
`obtained. Statem ents or suggestions concerning the use of m aterials and processes are m ade w ithout representation or warranty that
`any such use is free of patent infringem ent and are not recom m endations to infringe on any patents. The user should not assum e that
`all toxicity data and safety m easures are indicated herein or that other m easures m ay not be required.
`
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