h a l f b a k e r yStrap *this* to the back of your cat.
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SuperCool
Use engine steam to circulate coolant | |
Pursuit Dynamics (link below) has a pump with no moving parts. It works by injecting steam into the flow of liquid to be moved. This has a minor effect in entraining the pumped liquid, and a major effect in setting up a continuous shockwave effectively pulling the liquid through the pipe. It has been
proven to work in pump diameters from 6mm to 25mm, although these do not seem to be absolute limits.
An automobile engine has a mechanical water pump – I believe it's normally a centrifugal pump. It is heavy, expensive, not terribly reliable, and saps energy. A very small electrically-driven pump could be used to feed a trickle of water into a steam generator wrapped around the exhaust manifold. This would power a PDX pump to circulate the coolant. Waste heat is thus used to cool the engine.
Advantages would be:
1: Smaller, simpler, cheaper, more reliable, more fuel-efficient, easier to maintain.
2: The pump does not need a thermostat – it will not operate until the engine reaches operating temperature.
3: Once the engine is hot, the pump will continue to run for a while even when the engine is stationary eg in fuel-saving 'stop at lights' mode. Current hybrids need complex mechanical to electrical switchover mechanisms to achieve this.
Ideally an arrangement could be devised which would not need the electrical trickle pump, but I can't see how to do this yet.
http://www.pursuitdynamics.com/default.asp
halfawakery's link
http://www.pursuitd...ics.com/default.asp
(I don't charge for this service) [po, Oct 04 2004]
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It sounds good. Really good. Does anyone suppose injecting steam into the coolant is counter-productive? |
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This kind of pump technolgy is exciting! |
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But here are my concerns /questions: |
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Where would the water to make steam come from? A reservoir would need constant filling, and the addition of water to the coolant would lower its glycol content. (a big problem in cold climates) |
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What if the coolant was the steam source? Wouldn't their be problems because of the the need to condense the steam in the close cooling system? What about the effect of boiling on the glycol? |
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Also generating steam from the exhaust manifold has problems- it would reduce exhaust temp, bad for calatlytic converter. A steam generator would have vanes and part that would obstruct exhaust outflow, raising back pressure, and interfering with performance. |
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I think an interesting app for this kind of pump might be to use as an aeration pump for sewage treatment plants, use the waste gas to produce steam, use the steam to power aeration pums, which would add heat and accelerate the action of bacteria. (unless too hot, but the degree of heating is not known to me.) |
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I've been assuming from the beginning that the coolant is the steam source – it's the fact that it's a closed system that makes the process so attractive. Agreed that boiling the glycol is a problem – what is the effect of this? Does it break down? Can it reform? Will it in fact vapourise at all? |
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I'm also concerned about the ability to condense the steam back into the coolant. This is (as far as I understand it) a near-explosive phenomenon with the PDX pump, and I'm not sure if there would be enough temperature differential between the steam and the coolant on the exit from the radiator, particularly given that the whole system is pressurised? What is the temperature drop across the radiator? It might need a bigger / more efficient radiator to make it work? |
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I assumed that steam could be generated from a small bore pipe wrapped around the manifold – they do get pretty hot and the amount needed is not great. Taking heat from the exhaust is not a problem I don't think – turbos do that, and they don't seem to affect the cat unduly. They also slow the flow, (as does a silencer!) and again it can be easily handled. |
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I can also now see a way to dispense with the trickle pump too. If coolant was heated between a one-way valve and the pump, the steam trapped in this length of pipe would increase in pressure and cut off the inlet flow until it had escaped through the pump. The lowering of pressure would then allow the valve to open and more fluid to flow in. And so ad infinitum. |
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[ The sewage pump application you describe is very similar to one described on the PDX site – they've just finished a successful test with Sonico in the Goldbar wastewater treatment plant in Edmonton. In answer to your specific question, PDX say that the outlet liquid is only raised in temperature by 3 or 4 degrees C, although I think this is to some extent tunable. It can also macerate, which is very useful in the treatment of solid sewage. ] |
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I think the added complexity of this system will nullify any potential benefits, especially since the coolant mixture in cars is designed specifically NOT to boil, and the cooling system is generally under a few pounds of pressure, raising the boiling point further. Simpler alternatives exist for automotive applications, otherwise the technology seems to have potential. |
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Is there some way you could take the
water by condensing some of the
exhaust? Roughly speaking, burning
1gram of petrol produces roughly
1gram of water (and around a couple of
grams of CO2), which normally is
expelled as vapour (and is seen only
from a cold engine on a cold day, where
it condenses as a fog and/or drips from
the exhaust). So, having taken some of
the exhaust heat to power the pump,
take out some more of the heat and
collect the condensate to provide the
trickle of water. Win win. |
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