Water pump - electric

[BDA]

I'd bet he would remember you! If you do call him, I'd be interested in his opinion on the subject.

[GavinT]

My question is: Since the heat in the engine is generated in the head, that seems like the part of the engine we should focus on cooling. So why wouldn't the cooling system be designed so that the coolest water goes there first? Such a design would work backwards from the way it actually works. The cooled water from the radiator would go to the head, down into the block, and out the water pump back to the radiator.

Good question.
Perhaps the thermosiphon effect is merely a design parameter left over from a bygone era?

How potent is the thermosiphon effect?
Is it like the coriolis effect which is relatively minor?

[EuropaTC]

How potent is the thermosiphon effect?
Is it like the coriolis effect which is relatively minor?

I've limited experience of the system, we used them on mechanical seals and from what I remember they had to be set up correctly, ideally with the reservoir/cooler directly above above the item you were cooling. Also a metre or so height was required, I think that was to get sufficient temperature gradient but I'm not sure.

It does work and folks sell commercial systems, the big advantage is that once set up there's not much to go wrong with them, and (almost) maintenance free was always a good idea on chemical plant !

Given the relative heights of engines/radiators in most cars you might get some movement but I doubt the effect would be good enough for anything with a decent power output.   On the Europa the radiator is well below the engine so it doesn't conform to the normal layout you'd expect for such systems.  And on the Europa, if the water pump belt goes then the car overheats minutes later so it does need a decent flow rate to work.

Brian

[Richard48Y]

Well, I'm going to throw in my two cents. 

Virtually all engines flowed coolant Up from the block to the head(s) until pretty recently.
Then someone decided that engine temps would be more evenly distributed if the hottest component (head) was cooled first.
I believe Chevy calls this "Reverse flow" and now uses it extensively.
As so many things automotive today this has a lot to do with quicker warm-up for emissions systems.
Also some consideration of complete engine thermal characteristics since so many modern engines use more aluminum and even plastic components than before.

As I recall a double cross-flow radiator is about 40% more efficient for a given size.

So Lotus may have been well ahead of the curve here. 

[Lotsof 3146 R]

Quick update:
With the increased flow rate the breather pipe to the top of the expansion tank (swirl pot) acts as a venture sucking in air and causing cavitation at the electric water pump.
A simple value, normally closed when running, open to bleed (see photo) is a quick and simple solution

[jbcollier]

The flow through the radiator is reversed from normal convention to make the the system less "air-lock-friendly".