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Old 11-15-2011, 12:20 PM   #1 (permalink)
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Heat storage system (Prius-like insulated coolant reservoir)

Hello, this is my first post here on EcoModder, even though I've been a member for quite a while now. I'm from Finland and the winters here are quite cold. Temperatures of -20 C (-4 F) and colder are common in the wintertime.

I started working on a heat storage device for my Fiat Uno and would like to share my ideas and maybe get some good feedback. The Uno is a Italian supermini-class car and its 1100 cc engine doesn't warm up as fast as I would hope.

The heat storage system consists of a 10 liter (2.6 gal) coolant reservoir packed in a styrofoam insulation box with a couple of pumps. Coolant transfer is done in insulated hoses that run from the engine bay into the trunk. The engine + heater holds about 4 liters(1+ gal) of water while the whole original cooling system capacity is 6 liters (1.6 gal). The system uses waters high specific heat to store energy for warming an engine faster during cold starts. Works best when used with a core heater but results should be seen even without.

But how does it work?

As the thermostat opens, the IN pump in the reservoir starts to suck hot coolant into the reservoir while the OUT pump is pumps coolant from the bottom of the reservoir out into the water pump. For a while this works like a radiator, taking heat from the engine, but unlike a radiator the valuable heat is not blown away into the atmosphere but stored for future use. When the reservoir reaches a given temperature (75+ C/ 170+ F) it starts to pump slowly just to keep the temperature hot.

As the car is parked after a drive the engine starts to cool rapidly, but the coolant in the insulated box does not. If the engine is fully warmed up and the trip is long enough, temperatures at the time of parking in the reservoir are about 80-85 C (~180 F).

The next time the car is started the temperature of the engine and the coolant have dropped significantly. The temperature of the coolant in the reservoir depends on the time of parking but as my tests have shown, after a 8 hour work shift the temperature is about 55-60 C. This depends on the insulation. The cold engine starts to receive hot coolant from the reservoir which is mixed into the cold coolant (to make temperature rise consistant over entire engine and prevent cracking). The pumping stops when the engine and reservoir temperatures are the same. The cycle starts over when the thermostat opens.

The system is still in a beta stage with temperature probes being calibrated and the best locations for input and output hoses to the engine under consideration.

So what do you think?

I couldn't post images, maybe you can see the attachments.

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