I'm sure this has been discussed before (said the thief
) but how about exchanging heat between the flow to and from the radiator?
Maybe by using a heat exchanger but have both flows in the same direction, as to mix (instead of surpass) the temperature to the rad and to the engine?
Then the radiator would warm more evenly and the backflow will not be cold.
If it gets really hot the radiator will pretty much get fully heated anyway.
If the engine is cold some of the first heat flowing towards the radiator will flow back into the engine keeping it in the comfort zone.
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2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut.
lifetime FE over 0.2 Gigameter or 0.13 Megamile.
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For education go to people unlike yourself.