A gas turbine generates 25MW in an open cycle configuration

A gas turbine generates 25MW in an open cycle configuration.
Determine:
(1) the amount of power that can be generated for heating
(2) the resulting efficiency of the plant

State all assumptions

Solution

ASSUMPTION: The turbine runs at a high enough specific speed s.t. the efficiency has levelled out. From Charts like Smiths, the efficiency is a function of specific speed and levels out at about 90% for normal running clearances.

The WASTE HEAT is what can be used for heating from the exhaust gases, assuming the shaft power is used for driving machinery and other work. The waste heat is what is deficit in the efficiency from various factors like mechanical, electirical, volumetric and others. Main efficiency inputs are mechanical and volumetric.

The question should have been asked the other way around: How much eficiency is estimated?

How much power is available ( from waste output).

Deducting 1-2 % for mechanical efficiency, the waste contricutes abot 8-9% from the total of 100%, so about 25*0.1 MW available for heating means a max of 2.5 MW

(Please note, these are approximate figures, as no correct answer is possible for such a problem which is real world)