Next Generation
Refrigerant Solution forElectric Vehicle Heat Pumps
The adoption of heat pumps in battery electric vehicles increases toaddress deficiencies in thermal management. A new paper “NovelRefrigerant Solution for Electric Vehicle Heat Pumps” examines optimal
refrigerant blends for improved performance at a range of temperatures.

REFRIGERANT PERFORMANCE CRITERIA
Presently, no single refrigerant molecule is able to meet all the goals for the evolving EVindustry.
CRITERIA

Volumetriccapacity

COP

Average
Glide

Safety Classification
per ASHRAE 34

GWP

NBP

TARGETS>20% overR-1234yf> R-1234yf< 3KA2L< 150< R-1234yf to maintain positive
suction pressures at low ambient
heating conditions

Average outputs listed above based on thermodynamic system performance using SAE boundary conditions 1-13 for EV.
HP Average outputs listed above based on thermodynamic system performance using SAE boundary conditions 1-13 for EV HP.

THERMO-PHYSICAL PROPERTIES
Using extreme conditions for both AC and HP operations, performance evaluations against
R-1234yf were conducted with respect to the noted criteria from the stakeholders.
An optimal blend with mass concentrations of 7.5% R-32, 78.0% R-1234yf, and 14.5%
R-152a was selected and given the developmental name of R-457C (HFOG7).
Properties

R-134aR-1234yf

R-457C

Relative molar mass (g/mole)

102.0

114.0

95.5

Normal Boiling Point (°C)

-26.1

-29.5

-37.3

Dew-point temperature at 101 kPa (°C)

-26.1

-29.5

-32.1

Critical Temperature (°C)

101.1

94.7

94.1

Critical Pressure (kPa)

4059

3382

3956

Specific volume at the critical point (m3/kg)

0.00195

0.002100.00224

Latent heat of vaporization @ 60°C (kJ/kg)

139.1

110.4

127.9

Specific heat ratio of the vapor at 60°C

1.45

1.45

1.51

Occupational Exposure Limit (ppm)

1000500605Global Warming Potential (AR5)

1300

<172

Safety Class (ASHRAE)

A1

A2L

A2L

This table summarizes key thermo-physical properties of the incumbent fluids (R-134a and R-1234yf) compared to HFOG7.

THERMODYNAMIC CYCLE PERFORMANCE
These evaluations were conducted using Cycle D version 6.0 software from NIST.
R-457C (HFOG7) results at the AC condition exhibited a 22.6% increase in relative coolingcapacity and a 1.0% increase in relative COP.

COOLING

Whereas heating mode showed a 25.1% increase in relative heating capacity and a 3.7%
increase in relative COP when compared directly to R-1234yf.
Suction Pressure(kPa)

Discharge
Pressure (kPa)

Discharge
Temperature(C)

1234yf

316

1018

R-457C

372

1223

Refrigerant

Avg. Glide(K)Cooling Capacity(kJ/m3)

COP

54.90

1974

3.73

64.0

3.5

2419

3.77

Heating Capacity(kJ/m3)

COPHEATING

Evap = 0⁰C, Cond = 40⁰C, Evap superheat = 10⁰C, Subcool = 0⁰C and Isentropic Eff. = 70%

Suction Pressure (kPa)

Discharge
Pressure (kPa)

Discharge
Temperature(C)

1234yf

99

1302

73.3

0838

2.19

R-457C

115

1557

90.3

2.75

1049

2.27

Refrigerant

Avg. Glide(K)Evap = -30⁰C, Cond = 50⁰C, Evap superheat = 10⁰C, Subcool = 0⁰C and Isentropic Eff. = 70%

2Average outputs listed above based on thermodynamic system performance using SAE boundary conditions 1-13 for EV.
HP Average outputs listed above based on thermodynamic system performance using SAE boundary conditions 1-13 for EV HP.

MATERIAL COMPATIBILITY
R-457C (HFOG7) was evaluated for compatibility with an array of plastics commonly usedin refrigeration and air conditioning applications.
Sealed glass tubes were prepared containing HFOG7, POE lubricant (ND-11), and thematerials of interest. The tubes were held at 100°C for two weeks and the materials wereremoved. Measurements for weight, linear swell, and hardness were recorded before andafter exposures so differences could be assessed.
Two exposure measurements, immediately after exposure (0 hours) and after 24 hoursof exposure, were taken to determine if a time dependent recovery effect occurs withpolymers or plastics after separation from refrigerant.
Rating% Weight
Change% Linear
SwellHardness
Change, Delta-2Torlon polymer (polyamide-imide plastic)

000Ryton polymer (polyphenylene sulfide)

0000

PLASTICS AFTER PEEK (Ketaspire 820 NT)
0 HRSnylon 6.6 polymer plastic (Zytel 101)

0000teflon PTFE

0000021-2nylon resin - Zytel 330

00-101Torlon polymer (polyamide-imide plastic)

0-100

Ryton polymer (polyphenylene sulfide)

0000PLASTICS AFTER PEEK (Ketaspire 820 NT)
24 HRSnylon 6.6 polymer plastic (Zytel 101)

00000001teflon PTFE

021-2nylon resin - Zytel 330

00-101Rating: missing data

FLAMMABILITY
The subclass of 2L refrigerants per ASHRAE Standard 34 requires that all of the criteriaof Class 2 be met plus the additional requirement that the maximum burning velocity be avalue of less than or equal to 10 cm/s when measured at 23 °C and 101.3kPa in dry air.
The WCF for burning velocity was defined as 8.0% R-32, 77.0% R-1234yf, and15.0% R-152a while the WCFF for burning velocity was defined as 0.1% R-32, 80.4%
R-1234yf, and 19.5% R-152a. HFOG7 burning velocity results for the WCF and WCFF
are shown in the table (below).
10,0
9,0
8,0
7,0cm/s

6,0
5,0
4,0
3,0
2,0
1,0
0,0
5,5%

6,0%

6,5%

7,0%

7,5%

8,0%

8,5%

Refrigerant Volume Percent in Air
WCF-BV

3WCFF-BV

9,0%

9,5%

10,0%

10,5%

CONCLUSIONS
Addressing the thermal management deficiencies in BEVs is a key issue for theautomotive OEMs where they have identified that both improvements in heating capacity
and system efficiency are needed. As the adoption of heat pumps for BEVs becomesmainstream, improvements provided by novel refrigerant HFOG7 will aid in bridging thisgap. R-457C (HFOG7) has shown significant improvements in both volumetric heating
and cooling capacity, 25.1% and 22.6% respectively, as well as COP over R-1234yf, theincumbent refrigerant.

© 2022 The Chemours Company FC, LLC. Opteon™ and any associated logos are trademarks or copyrights of The Chemours Company FC, LLC.
Chemours™ and the Chemours Logo are trademarks of The Chemours Company.