Without trying to promote or defend the Volt...
Multiple heat exchangers can be the source of energy efficiency as it may be using these as heat/energy recovery devices.
Most of the inefficiency in a traditional style internal combustion engine and automobile can be associated with energy lost as heat.
In refineries, petrochemical plants, etc, we often use multiple heat exchangers as a way to boost overall system efficiencies by recovering energy otherwise lost as heat.
Not in this case, though. From the article:
The Volt uses additional [cooling systems] to cool the battery and electronics, so no fewer than five heat exchangers, or radiators, and associated plumbing had to be replaced. The Volt is also highly computerized, and the car goes into a safe mode after a collision that requires the engine control module to be reprogrammed. "Other hybrids don't do that," Tamblyn said.
With all this heat exchanging and energy recovering going on, it is easy to see how the Chevy Volt can travel up to 40 miles on a single charge!
/sarc
I hope you’re right but it doesn’t seem that these should be in something that is supposedly as efficient as an electric automobile. Other than dissipating waste heat due to the large inverter and poly-phase wheel motors, I can’t see what they would be for.