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I want to know how this four pressures and enthalpies are selcected

I want to know how this four pressures and enthalpies are selcected

Elements Of Electromagnetics
Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
Problem 1.1MA
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I want to know how this four pressures and enthalpies are selcected

8.6. A steam power plant employs two adiabatic turbines in series. Steam enters the first turbine at 650°C and 7000 kPa and discharges from the second turbine at 20 kPa. The system is designed for equal power outputs from the two turbines, based on a turbine efficiency of 78% for each turbine. Determine the temperature and pressure of the steam in its intermediate state between the two turbines. What is the overall efficiency of the two turbines together with respect to isentropic expansion of the steam from the initial to the final state? A steam power plant employs two adiabatic turbines in series. Steam enters the first turbine at 650 and 7,000 kPa and discharges from the second turbine at 20 kPa. The system is designed for equal power outputs from the two turbines, based on a turbine efficiency of 78% for each turbine. Given the initial temperature and pressure to be T₁ = 923.15K, P₁ = 7000kPa H₁ = 3766.38kJ/kg Hence from steam tables, S₁ = 7.22kJ/kgK At 20 kPa, the values for saturated liquid and vapour are as follows: Hlig = 251.45kJ/kg, Hvap = 2609.9kJ/kg Sliq=0.832kJ/kgK, Svap = 7.909kJ/kgK The four values of pressure and the corresponding enthalpies are as follows: 725 750 775 800 P₂ kPa, H₂ 3023.9 3032.5 3040.9 3049.0 Actual work is given by n(h₂' -h₁) H₂act = The actual enthalpy and entropy are hence -579.15 +3766.4 -572.442 +3766.4 -556.89 +3766.4 559 579 3766 4. 0.78(3023.93766.4) 0.78(3032.5 3766.4) 0.78 (3040.93766.4) 0.78(30493766.4) 3187.3 3194.0 3200.5 3206 8. why this 4 Pressures are selected? kJ/kg = -579.15 -572.442 -565.89 -559.512
Transcribed Image Text:8.6. A steam power plant employs two adiabatic turbines in series. Steam enters the first turbine at 650°C and 7000 kPa and discharges from the second turbine at 20 kPa. The system is designed for equal power outputs from the two turbines, based on a turbine efficiency of 78% for each turbine. Determine the temperature and pressure of the steam in its intermediate state between the two turbines. What is the overall efficiency of the two turbines together with respect to isentropic expansion of the steam from the initial to the final state? A steam power plant employs two adiabatic turbines in series. Steam enters the first turbine at 650 and 7,000 kPa and discharges from the second turbine at 20 kPa. The system is designed for equal power outputs from the two turbines, based on a turbine efficiency of 78% for each turbine. Given the initial temperature and pressure to be T₁ = 923.15K, P₁ = 7000kPa H₁ = 3766.38kJ/kg Hence from steam tables, S₁ = 7.22kJ/kgK At 20 kPa, the values for saturated liquid and vapour are as follows: Hlig = 251.45kJ/kg, Hvap = 2609.9kJ/kg Sliq=0.832kJ/kgK, Svap = 7.909kJ/kgK The four values of pressure and the corresponding enthalpies are as follows: 725 750 775 800 P₂ kPa, H₂ 3023.9 3032.5 3040.9 3049.0 Actual work is given by n(h₂' -h₁) H₂act = The actual enthalpy and entropy are hence -579.15 +3766.4 -572.442 +3766.4 -556.89 +3766.4 559 579 3766 4. 0.78(3023.93766.4) 0.78(3032.5 3766.4) 0.78 (3040.93766.4) 0.78(30493766.4) 3187.3 3194.0 3200.5 3206 8. why this 4 Pressures are selected? kJ/kg = -579.15 -572.442 -565.89 -559.512
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