Question 10 in the morning session of the 2017 Chemistry exam
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10. A turbine is driven by superheated steam at 735 K and 1520 kPa (H1=326.7 kJ/kg, S1=7.5182 kJ/(kg·K)). While driving the turbine to perform work, each kg of steam loses 7.1 kJ of heat to the surroundings; the ambient temperature is 293 K, and the pressure of the steam after work is done is 71 kPa (H2=2770.5 kJ/kg, S2=7.7735 kJ/(kg·K)). What is the thermal efficiency η (%) for this process? A、92.3 B、88.8 C、79.6 D、76.6 Please experts provide the solution process!
What I did was divide the lost work by the ideal work, resulting in an efficiency loss of 0.1112; then I used 1-0.1112=0.8888, which equals 88.88%. I’m not sure if I did it right; please, experts, help me correct it!
Could you write down the specific calculation process? Thank you!