Secondary*Loop*Motor*Vehicle*Air*

Condi5oning*Systems*(SL:MACs)*

Using*Low:Global*Warming*Poten5al*(GWP)*Refrigerants*in*Leak:Tight*Systems*

In*Climates*with*High*Fuel*Prices*and*Long,*Hot*and*Humid*Cooling*Seasons*

Building*on*the*Previous*Success*of*Delphi,*Fiat,*General*Motors,*Volvo,*Red*

Dot,*SAE*Coopera5ve*Research*Projects,*and*Other*Engineering*Groups*

Orlando*MACS*Briefing*

6*February*2015*

Stephen*O.*Andersen*&*Nancy*J.*Sherman,*IGSD*

Timothy*Craig,*Delphi*

James*Baker,*JAB*Consul5ng
Protocol*&*Market*Drivers*

of*HFC:134a*Phase:Down*in*MACS*

• Protocol*Drivers*

– The*Kyoto*Protocol*already*controls*

hydrofluorocarbon*(HFC)*emissions'

– The*Montreal*Protocol*will*likely*soon*control*HFC*

produc-on'and'consump-on'''

• Market*Drivers*

– EC*MAC*Direc5ve*requires*GWP*<150*aaer*2017*for*

new*automobiles*sold*in*the*European*Union*

– US*EPA*offers*credit*toward*fuel*mileage*standards*

and*may*prohibit*HFC:134a*in*new*cars*aaer*~2022*
SL:MAC*Demonstra5on*Project

• Design,*build,*test*and*demonstrate*an*energy:

efficient*SL:MAC*for*high*ambient*temperature*

climates*using*R:1234yf*(GWP*<1)*or*R:152a*

(GWP*=*138);*both*SNAP*and*REACH*approved**

• Financed*by*the*Climate*and*Clean*Air*Coali5on*

to*Reduce*Short:Lived*Climate*Pollutants*(CCAC)*

• Principal*Inves5gators:*Stephen*O.*Andersen,*

IGSD;*James*Baker,*JAB*Consul5ng;*Timothy*Craig*

&*Mark*Zima,*Delphi;*and*Sangeet*H.*Kapoor*&*

Nagarhalli*Prasanna,*TATA*
Why*Secondary*Loop?** ****************

•**Safe*use*of*mildly*flammable*refrigerants*

•**Lower*charge*reduces*refrigerant*emissions/costs*

•**Reduced*A/C*system*noise*

•**Lower*cost*for*mul5:point*cooling*point*systems*

•**Cold*storage*comfort,*economy*&*environment*

•**“Regenera5ve*cooling”*during*decelera5on;*

reduced*compressor*load*during*accelera5on*

•*A/C*comfort*during*longer*stop/start*(idle:stop)*

•*Uniform*air*temperature*across*cooling*coil*

•*Fewer*compressor*oil*starva5on*issues
Why*a*First*Demonstra5on*in*India?*

• Longer,*hooer,*and*oaen*humid*cooling*season*

with*rela5vely*high*fuel*prices*in*India*shortens*

the*payback*for*energy*efficiency*improvements*

• Low*risk*of*freezing*allows*choice*of*secondary*

loop*coolant*that*op5mizes*energy*efficiency*

• India*and*other*developing*countries*will*qualify*

for*Montreal*Protocol*financing*once*the*HFC*

phase:down*Amendment*is*agreed*
Technical*&*Cost*Performance**

• Cooling*Performance*

– Cooling*capacity*(Bench*and*wind*tunnel*tests)*

– Cooling*comfort*(ride*tests)*

– Op5mized*engine*loading*by*interac5on*of*secondary*

loop*coolant*buffer*with*engine*management*system*

• Cost*Performance*

– Reduced*refrigerant*charge*and*refrigerant*cost,*but*

added*cost*of*chiller,*pump,*and*reservoir*

– Less*frequent*and*lower*cost*recharge*from*leaks,*

accidents*or*component*failure*

– Lower*cost*for*addi5onal*cooling*points***
Environmental*Performance*

• Direct*Refrigerant*Greenhouse*Gas*(GHG)*

Climate*Performance*

– Reduced*refrigerant*charge*and*life:cycle*leak*rate*

with*shorter*hoses,*fewer*fiqngs*and*integrated*

components*(calculated*using*SAE*J:2727)*

• Indirect*Energy*GHG*Climate*Performance*

– Higher*energy*efficiency*with*engine*management*

system*(EMS)*integra5on*and*cooling*on*decelera5on*

(regenera5ve*cooling)**

– Higher*fuel*savings*from*stop/start*by*reducing*the*

5me*stop/start*is*deac5vated*because*it*is*too*hot
Safety*&*Economy:*HFO:1234yf*

• Cost*of*addi5onal*secondary*loop*components*

offset*by*savings*from*reduced*system*charge*

• Reduced*charge*encourages*proper*service*using*

HFC:1234yf*rather*than*lower*cost*HFC:134a*

• Lower*life:cycle*emissions*reduce*trifluoroace5c*

acid*(TFA)*forma5on*from*HFO:1234yf*refrigerant*

degrada5on*
Safety*&*Economy:*HFC:152a*

• Cost*of*addi5onal*secondary*loop*components*

offset*by*refrigerant*cost*savings*compared*to*

HFO:1234yf*

• Proper*service*using*HFC:152a*because*HFC:134a*

costs*more*

• HFC:152a*has*no*TFA*degrada5on*byproducts*

• Use*of*HFC:152a*refrigerant*in*leak:5ght*

secondary*loop*systems*is*safe*and*approved*

under*the*US*EPA*Significant*New*Alterna5ves*

Policy*(SNAP)*Program*and*the*EC*F:Gas*Direc5ve**
Poten5al*Challenges:*Risk*Mi5ga5on*

• Small*Charge*

• Charged*components*in*wind*stream**

• Refrigerant*isolated*from*igni5on*sources*

• Loca5on*and*control*of*refrigerant*pressure*

relief*valve*

• Ac5ve*safety*systems?*

A company considering HFO-1234yf unsafe for their cars 

in direct expansion systems 

 could declare secondary-loop as the design solution 
Poten5al*Challenges:*Design*

• Managing*weight*and*spa5al*impact*of*addi5onal*

components*in*the*engine*compartment*and*

vehicle*cabin*

• Sizing*to*sa5sfy*cooling*performance*and*ride*

comfort,*par5cularly*for*ini5al*cool:down*from*

hot:soak*

• Developing*compressor*on/off*strategies*that*

balance*fast*thermal*pull*down*in*high*ambient*

temperatures*with*fuel*efficiency***
Poten5al*Challenges:*Service*

• Safety*in*servicing*pressurized*systems*with*

flammable*refrigerants*

• Best*prac5ces*in*refrigerant*iden5fica5on,*

recovery,*recycle,*etc.*

• Maintaining*coolant*quality*and*freeze*

protec5on*and*avoiding*and*resolving*air*in*

the*coolant*circuit*
The*Importance*of*Advisors*

• Help*make*the*design*and*demonstra5on*as*

good*as*it*can*be*

• An5cipate*and*help*answer*important*ques5ons*

about*technical,*environmental,*and*cost*

performance*

• Communicate*the*findings*to*the*mobile*air*

condi5oning*community*and*to*policy*makers*

• Head*start*on*how*to*contribute*to*the*

commercializa5on*of*SL:MACs**