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Technical Issues: Session 3

Challenges and Opportunities in addressing high GWP HFC’sin Mobile Air Conditioning (MAC)

Options for Existing Systems / Equipment(Drop in / Retrofit)

SH Kapoor

Technical Chief (Climate Control)

TATA Motors Limited, India

Email: [email protected]

UNEP Workshop on HFC Management

Bangkok, Thailand20, 21 April 2015


Low GWP Refrigerants: Drop In / Retrofit Options?

R1234 yfR134a Cooling Performance cannot be matched with R1234yf as a ‘Drop In’Equivalent performance and durability requirements need to be met with significant re-engineering of MAC system components

R152aSuperior Cooling Performance can be attained with R152a; cannot be ‘Drop In’ due to flammability risk in case of leak (cab/engine) Potential Secondary Loop refrigerant with down sized MAC system components for matching R134a Cooling Performance

R744R134a Cooling Performance cannot be matched with R744 at higher ambient temperatures (Tc=31°C)All MAC system components require significant re-engineering due to very high system pressures and hence ‘Drop In’

is not a feasible option

Refrigerant Parameters for Operating Limits: 0°C Evaporating Temperature and 55°C Condensing Temperature

Parameter HFC134a(GWP=1430)

HFO1234yf(GWP=4)

HFC152(GWP=124)

R744(GWP=1)

Suction Pressure (bar-abs) 2.9 3.2 2.6 34.9

Discharge Pressure (bar-abs) 14.9 14.6 13.3 115

Pressure Ratio 5.1 4.6 5.1 3.3

Enthalpy of Vaporization (kJ/kg) 198.6 163.3 307.1 231.3

Vapour Specific Volume (m3/kg) 0.069 0.057 0.119 0.0103


Secondary Loop MAC: R152a, R1234yf

Parameter Opportunity Challenge

Design• With proper engineering design, freeze

protection and optimization, secondary loop

MAC’s are suitable for all climates

• Complexity of integration / packaging of

the additional components (small cars)

• Added components, increased weight

Performance

• Cabin cooling not compromised during extended

idle and long idle stops (stop / start traffic)

• Homogeneity of air temperatures across cooling

coil due to absence of phase change

• Minimizes fluctuations in vent outlet and cabin

temperature

• Reduce engine load during acceleration by

switching off compressor (fuel economy)

• Timing powered cooling – switch on compressor

when engine is at high energy efficiency

• Reduced MAC system noise transmitted from

thermostatic expansion valve (TXV) inside

passenger cabin

• Increased time to ‘pull down’

temperature to comfortable levels due

to thermal inertia of coolant

• Development and integration of Engine

Management System (EMS)

• Coolant pump power consumption

Refrigerant Circuit

• Absence of oil trapping issues in dual AC MAC

systems particularly when rear unit is turned off


Parameter Opportunity Challenge

Material Cost

• Reduced refrigerant charge offsets cost of

additional components even for dual AC MAC

systems (multiple cooling points)

• Reduced frequency of refrigerant recharges over

a vehicles service and maintenance life

(lower ownership costs)

Environment

• Use of environment friendly low GWP refrigerant

R152a / R1234yf

• Reduced refrigerant charge and life cycle GHG

emissions

Safety• Reduced refrigerant charge lowers fire risk

• Refrigerant separated from passenger

compartment

• Deploy refrigerant leak sensor and relief

valves for quick release of refrigerant to

atmosphere (thru wheel arch)

• Charged components placed in wind

stream and away from ignition sources

Secondary Loop MAC: R152a, R1234yf


Summary: Drop in / Retrofit Refrigerant Options for Existing Systems / Equipment

• HFO1234yf is gaining acceptance as an alternate MAC refrigerant option due to its low GWP of 4 but is mildly flammable

• HFO1234yf as a drop in refrigerant for a car already in service poses the challenge of deterioration in cooling performance and risk of cross contamination with existing PAG oil

• Not all compressors are available with PAG oil compatible with HFC134a and HFO1234yf

• This can lead to compressor durability issues and hence drop in is not recommended


Summary: Drop in / Retrofit Refrigerant Options for Existing Systems / Equipment

• HFC152a is a low GWP, slightly flammable refrigerant with superior properties and high potential of downsizing MAC system components like compressor and condenser

• The flammability risk associated with HFC152a and HFO1234yf can be mitigated by reducing the refrigerant charge, deployment of a Secondary Loop (SL) and use of leak sensors and relief valves

• The SL – MAC in combination with power train technologies has a high potential of improving overall energy efficiency and reducing carbon footprint

• To evaluate the opportunity of using SL – MAC with HFC152a and HFO1234yf, understand the challenges related to cooling performance, safety, power train technology and cost impact, a demonstrator car project needs to be initiated by relevant stakeholders


Thank You for your Attention!

Questions

End of Report


MAC Refrigerants: Past, Present and Future

Status Phased Out Current Future: Potential Alternatives

Parameter R12 (CFC) R22 (HCFC)Building Air Conditioning

R134a (HFC) R1234 yf (HFO) R152a (HFC) R744

Bonding

IUPAC NameDichloro Difluoro

MethaneChloro Difluoro

Methane1,1,1,2 – Tetra Fluoro

Ethane2,3,3,3 – Tetra Fluoro

Propene1,1 – Difluoro

EthaneCarbon Dioxide

ODP1

(2 Chlorine Atoms)0.05

(1 Chlorine Atom)0 0 0 0

GWP (100yr)(IPCC AR4)

10,900 18101430

(4 Fluorine Atoms)4 124

(2 Fluorine Atoms)1

Atmospheric Lifetime

100 years 12 years 14 years0.03 years

(due to weaker double bond)

1.4 years >100 years

Flammability(ASHRAE) A1 A1 A1

A2 L

(Mildly)

A2

(Slightly)

A1

Critical

Temperature111.9°C 96.14 101.06°C 92.42°C 113.26°C 31.04°C

Normal Boiling

Point-29.8°C -40.7°C -26.3°C -29.4°C -25°C -78°C

A1 : No flame propagation A2 : Slightly flammable- Lower flammability limit @ 60°C: > 100 g/m3 or Heat of Combustion < 19 Mega J/kgA2L : Mildly flammable-Lower flammability limit @ 60°C: > 100 g/m3 and Heat of Combustion < 19 Mega J/kg With Maximum Burning Velocity < 10 cm/s

OC

O

H

FC

C

H

H

F

HC

Cl

F F

ClC

Cl

F

F

H

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