Heat storage system (Prius-like insulated coolant reservoir)

[Josh8loop]

Originally Posted by astra74

Sorry to dig up an old thread, but but i was thinking about this and i remembered this thread.

Any updates on this issue? Did you actually get to the implementing and testing of the system?

Sorry so long to reply. I haven't done anything more lately on this project. I ran into an issue when the Dewar I purchased was a bit too large for most location I wanted to put it. Also the large 6" opening on the top makes for some difficult container sealing options. I am thinking of going to two smaller dewars used for thermal coffee caraffes. Two of them may get a similar overall volume compared to my previous dewar. The caraffes have smaller top openings so I can turn a cap on a lathe that has a couple O ring seals. Then I could flow straight coolant through it instead of using the parafin. Still trying to figure it all out but it has been on my to do list.

[Demolite]

After a long time I'd like to share some things i noticed with my system. I recommend you don't use straight coolant to coolant transfer, the expansion system is very hard to do and the pressure of the cooling system doesn't stay in normal limits. Core plugs started to leak and the Uno's head gasget blew, propably as a result of coolant leakage. I suggest using insulated tubing to transfer heat and a pump in the system makes controlling and transferring heat quicker.

[Teemo]

Thanks Demolite for sharing this information with us. It may save my engine.
Sad to hear about your Uno.

[Demolite]

Wasn't too bad, the gasgets and parts are so cheap it cost only 30 euro for the whole job. Including resurfacing the head. I'm not saying a system like this cannot be done to an engine, I'm just saying look out for abnormal behaviour if you increase the cooling system capacity to 5 times the original and add extra pumps. Old corroded parts may not be able to handle the extra pressure/heat difference. Also keep in mind that if you return the hot coolant from heat exhanger to the water pump intake, the engine will be using that hot water as the cooling water. Especially when the thermostat is only part way open, I saw engine temps of over 100C. That combined with poor pressurisation (due to leakage and loss of coolant) of the system caused coolant to boil in the cylinder water-jackets.

[plasticuser]

Have you considered insulating the oil sump? The sump is insulated from the main engine block by a gasket, and oil doesn't evaporate, so the oil would stay warm for quite a long time.

Is it a pro or a con to start a cold engine with hot oil?

[elhigh]

Originally Posted by plasticuser

Is it a pro or a con to start a cold engine with hot oil?

I'd call that a pro.

[Demolite]

It's all about the energy, engine oil has less than half the specific heat of water and with an average oil capacity of 4-5 liters means it cant store enough energy for quick engine heat-up. There will be noticeable benefits from reduced friction which will lengthen the life of your engine and provide a smoother cold start. Word of warning, most cars (atleast here in the cold weather region) don't have oil coolers and rely on heat radiation from the oil pan and engine to keep oil at a reasonable temperature. Added insulation will interfere with this and oil temperature might exceed safe values.

[plasticuser]

Oil gives off less than 5% of its heat through the oil pan when the engine is running. About 95% of the surface contact area of the oil is with engine components and channels. Therefore, the oil is 95% cooled by transferring heat to metal, then coolant, and out the radiator. Also, while the engine is running, the level in the sump is less than half the level of when the engine stops and the oil drains downstairs.

[Demolite]

I didn't look into any numbers myself, just figured that as some cars come with finned oil pans and the oil pan is usually in the air stream below, maybe thats what the manufacturer wanted. In cold weather it won't likely make a noticeable difference in running oil temperature. Not sure for a hot summer day though. I think it's safe to say that it depends on the vehicle.

[plasticuser]

Some performance cars do, yes

If you're eco-driving, that should hardly be a problem. :P