On Jul 24, 1:28*pm, Andy Dingley wrote:

It's also wrong to use these simplistic enthalpy calculations to
explain engine efficiency, especially the importance of condensers.
Improvements to the low end of the cycle that appear to be unimportant
from a simple linear calculation actually turn out to be very
important when you integrate over the cycle.

I'm not sure what any of that is supposed to mean. The enthalpy
figures I gave were certainly not in any sense linear, and by looking
at the difference from maximum to minimum enthalpy I was indeed
"integrating over the cycle".

This is why stationary
engines, and marine engines, and especially turbines, all make the
effort to run condensers.

The extra efficiency is certainly worth having, though of course it
gets less and less as the boiler pressure and superheat increase.
There are other factors too, though. In general marine engines have to
recycle their water and the same goes for stationary engines with
specially treated water. Doing that means a condenser and if you're
going to have a condenser you might as well use it to suck a bit more
power out of the system. While locomotives could also benefit from the
water recovery, the power gained in the cylinders would be dwarfed by
the loss of draught from losing the blast pipe.

Ian