Here I work through two examples of the effect of isentropic efficiency on devices. I use the nozzle and the compressor as examples. I show that you need to produce a system and a T-S diagram. THen work out what form of the SFEE you need to use. Then work out the ideal temperature change, modify this by multiplying or dividing by the isentropic efficiency to get the real temperature change. Finally, use the SFEE to work out the power or velocity.