TIFFE - Integrated HVAC system -- Help me understand

[RossABQ]

In a thread in the HVAC section, solar-assisted refrigeration/heat pumps was discussed (

http://www.eng-tips.com/viewthread.cfm?qid=348557),

and uniformly pooh-pooh'd.

Today I ran across "TIFFE", Thermal Systems Integration for Fuel Economy. I found this paper on it:

http://www.sae.org/events/aars/presentations/2010/W3.pdf

My reaction is, I don't get it. I can't find a lot of detail on refrigerants used, etc. but flammable fluids are mentioned. It appears the HVAC condenser becomes water-cooled, and operates at a higher temperature. Sounds a lot like the solar-boosted heat pumps...

Can someone tell me how this gives the claimed 15% increase in fuel economy/CO reductions? I'm not seeing it.

 

[IRstuff]

They have their own website:

http://www.tiffe.eu/index.php?option=com_jdownloads&Itemid=61&task=viewcategory&catid=4

with some downloads, but nothing newer than the end of last year, but, of course, their contract was supposed to end Dec 2012

TTFN
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[ivymike]

the two related items were
Reduced A/C fuel consumption thanks to the improved and homogeneous condensation (-10%)
Reduced heat exchanger [mass?]

So, if your A/C fuel consumption is 150% of your total fuel consumption, then a 10% reduction in A/C fuel consumption will translate to a 15% reduction in overall fuel consumption. Simple. You get the added benefit of smaller hx!

 

[RossABQ]

Mike, that's just what I don't get (other than the suspect numbers). If you use a water-cooled condenser, and the hot side of that condenser rejects via the engine radiator, it seems like you're doubling your approach losses compared to an air-cooled condenser, have added another HX, and a pump (weight). Is this just hi-tech snake oil?!

 

[IRstuff]

TIFFE was just one of a number of projects sponsored?? by EUCAR:

http://www.eucar.be/publications/EUCAR Project Book 2012

It doesn't look like they got very far or were completely funded to their original 3.6M euro bedget, but at least, someone made good use of 2M euros

TTFN
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[ivymike]

Looks like they have three water loops and a refrigerant loop connecting two of them (p13).

One water loop is the usual jacket water circuit servicing the engine needs. (high temp)
One water loop is a medium temperature circuit, picking up heat load from various components including the hot side of the refrig circuit.
The last water loop is a low temperature one, providing coolant to the HVAC system.

The refrigerant circuit would not have very long lines nor much volume internally, so probably uses less refrigerant than normal and in only a centralized location ... this may explain the following benefits they proposed:
•Safer use of flammable refrigerants
•Reduced A/C fuel consumption thanks to the improved and homogeneous condensation (-10%) (perhaps there is a problem getting an even temperature distribution in the hx of a normal car's evaporator, giving localized condensation which makes cold water for the road, and using higher-temperature/water in that loop would eliminate the problem?)
•Reduced refrigerant charge (-50%) (smaller system)
•Higher comfort in case of Stop & Start or mild hybrids (cold water circuit can continue pumping when compressor is off, allowing the heat capacity of water to soak up some extra heat?)

The refrig. circuit would have smaller hx's due to improved heat transfer to water vs. air ... on the flipside the water-air cores would be bigger to handle the extra heat load and the delta-T for the refrig. circuit vs. water is less than vs. air.

Perhaps one key item is "a new generation of coolant fluid (nanofluids)" ... not sure which circuit those nanofluids live in.