Slide 1© Copyright, Confidential, Tata Motors Ltd
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
Slide 2© Copyright, Confidential, Tata Motors Ltd
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
Slide 3© Copyright, Confidential, Tata Motors Ltd
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
Slide 4© Copyright, Confidential, Tata Motors Ltd
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
Slide 5© Copyright, Confidential, Tata Motors Ltd
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
Slide 6© Copyright, Confidential, Tata Motors Ltd
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
Slide 7© Copyright, Confidential, Tata Motors Ltd
Thank You for your Attention!
Questions
End of Report
Slide 8© Copyright, Confidential, Tata Motors Ltd
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