37
3.
Nucleate boiling for
-
precision cooling.
-
engine heat removal with lower coolant flow rate.
4.
Increase maximum allowable temperature out of the engine and increased
T across
it.
5.
Consider the air-side heat transfer situation that is controlling.
6.
Increase radiator air-side surface.
7.
Use variable-speed coolant pump to bring the engine to temperature and to maintain
that temperature. Laminar flow can be avoided when the air side does not dominate.
(Bosch found 5% fuel economy improvement with such a system.)
that temperature. Laminar flow can be avoided when the air side does not dominate.
(Bosch found 5% fuel economy improvement with such a system.)
8.
Improve control of coolant using variable-speed pump, variable-drive fan, and control
as a system.
as a system.
9.
Consider alternate materials for radiator air-side heat transfer (like porous materials).
10.
Use large-diameter fans, but control the increased noise.
11.
Raise the allowable coolant temperature to about 260°F.
12.
Use improved fluid sensors to control coolant flow.
13.
Size coolant system near maximum service, and turn off EGR at the very peak loads.
The prioritization that resulted was
Short Term
1.
Use higher coolant temperature in the range of 240oF to 250oF with more uniform
cooling and increased reliability of temperature sensors.
cooling and increased reliability of temperature sensors.
2.
Use variable-speed fan drives and coolant pump.
3.
Increase air-side heat rejection 30% and underhood air flow reduction of 10-15%.
4.
ECU communication is important, e.g., transmission integration.
5.
Develop a non-EGR strategy.
Long Term
1.
Demonstrate improved vehicle cooling systems at full scale with an ECU standard.
2.
Evaluate non-EGR emissions-reduction options.
3.
Explore advanced air-side heat-rejection concepts.
4.
Change emission standard to g/mile basis; may require a real-time Nox sensor.
5.
Develop a fuel specification for reduced emissions.