On Sat, 22 Apr 2017 12:13:31 +0100, charles wrote:

In article , Tim Streater
wrote:
In article , The Natural Philosopher
wrote:

I suspect that the boilers and engines you are familiar with are
more nineteenth century technology than twenty-first century. A
titanium tube flash boiler can supply steam at up to 4,000 psi and
650C. Ceramics allow engines to work at those temperatures and
pressures and achieve efficiencies not even dreamed of with
conventional materials.

Exatamondo. I cant remember what the law is called, but the hotter the
working fluid (steam in this case) is to start with, and the colder
the final exhaust, the more efficient is the engine.

Which is why a combined cycle gas turbine that starts with 1000C gases
in the jet engine, then heats a boler to get steam, and has a final
after condenser temp of around 50C, willnet you over 60% thermal
efficiency.

One of the laws of thermodynamics IIRC - efficiency is related to the
difference between input and output temps - in degrees K, not C.

my elementary physics suggests that if you are only refering to a
temperature difference the answer is the same in °K and in °C.°

The main benefit of using deg K instead of Deg C is the complete and
utter absence of negative numbers by which to confuse the mathematics. :-)

It's true enough that as far as steam engines are concerned, this is
unlikely to effect calculations involving deg C, but there are other heat
engines designs based on fluids with much lower freezing and boiling
points than zero deg C (the triple point of water to within an accuracy
of one decimal place).

--
Johnny B Good