Thursday 8 October 2020

thermodynamics - What meaning does the slope of the efficiency path on a Mollier diagram have in terms of temperature?



Let's say I have a steam turbine that I have modified to increase its isentropic efficiency. As a specific case, consider the modification outlined in the Mollier diagram below. The arrows represent the before and after modification paths of the turbine on the Mollier diagram.


The slope of the arrows represent how efficient the turbine is. A horizontal slope is a throttling process whereas a vertical slope is 100% isentropic efficiency. Slopes in between obviously are something less than 100%.


The slope is $\Delta{H} \over \Delta{S}$ which has units of temperature (degR).


Does the fact that the units of the slope are temperature hold any special meaning? Why would the value of a temperature inherently represent a performance level of isentropic efficiency? Does the fact that the values are always negative mean anything? Is the reason 100% efficiency is impossible related to the fact that the value of the temperature is $-\infty$?


turbine mod




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