[modeleng] Re: Aluminium boilers

My feeling is that there isn't an alumium alloy that can maintain its 
strength at firebox temperatures. You have to take into account the 
Nagayoka (I'm not sure of the spelling!) curves, which shows that under 
some circumstances, you can get a decrease in heat transfer as the 
temperature increases because of a semi insulating sheath of steam bubbles 
forming around the metal. This would enable the firebox crown temperature 
to be considerably higher than you would expect for something immersed in 
water, and becsue of the negative slope of the heat transfer curve, , you 
can get a runaway condition.
Bottom line is, I don't think it would work, let alone practical 
difficulties of boiler certificates etc!

Peter Chadwick
Swindon (but currently on business in Antibes)

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