On 22/04/17 12:13, 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.°

Well its not actually the temperature difference, its the *ratio* of the
temperatures.

The total input energy in heat is proportional to the absolute temperature.

The lost output energy as heat is proportional to the output temperature
in absolute degrees.

Theres a bit of a fudge in that you start with ambient to do your
heating of course.



--
If I had all the money I've spent on drink...
...I'd spend it on drink.

Sir Henry (at Rawlinson's End)