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Originally Posted by serialk11r
Er, the examples you gave were of reclaiming blowdown pressure though :O
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Um... What do you think happens to the temperature? Do you have any idea of how a turbine works?
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Originally Posted by serialk11r
I was talking more about a secondary heat engine running off the thermal energy itself :O
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What do you call a turbine? That's not a good enough heat engine for you? You do realize that a turbine in a properly sized turbocharger will recover at least 20% and as much as 60% of the heat energy in the exhaust, don't you? Seems a bit better than the 15% claimed by the BMW turbosteamie.
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Originally Posted by serialk11r
BMW turbosteamer is probably the closest one to production, and I don't see that happening for some time.
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That turbosteamie thingy seems like a dead end. For the same gain in fuel economy, one could downsize the engine and attach a turbocharger to it. Oh, wait! They're already doing that extensively in Europe! Amazing what they can do over there... Mid- and full-sized sedans getting 40+ MPG right off the showroom floor.
So... instead of using something that's directly powered off the exhaust gas, you'd rather heat something else up, have that heat be lost through radiation as it travels via heat pipes to its heat engine, and then convert that diminished heat energy into mechanical energy - keeping in mind that there'll still be waste heat to get rid of. And all to get a recovery of 15% of the exhaust heat.
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Originally Posted by serialk11r
Thermoelectrics seem to be at the very least several years off from even viable prototypes.
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That was true decades ago, and it'll continue to be true for the foreseeable future. Until technology is perfected to the point where thermoelectric junctions can be efficiently manufactured on a microscopic scale, then it'll always be years away from becoming viable.
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Originally Posted by serialk11r
There's also SMA engines, whose progress I haven't really bothered to follow, though I understand they have a somewhat low theoretical peak efficiency by design.
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Motors made out of metals that are designed to deform and reform countless times... I dunno... sounds like a recipe for metal fatigue to me.