An adiabatic turbine operating under steady-state conditions receives superheated steam at a pressure of p1 = 20 bar and a temperature of T1 = 400C. At the exit of the turbine, the pressure of the wet steam is 1 bar. Two cases are considered: Isentropic expansion - question f) 1.

Actual expansion with an isentropic efficiency of 56% - question f2

Find the quality, specific enthalpy and specific entropy of the steam leaving the turbine in each case. Then, calculate the specific work output of the actual turbine and the entropy change of the steam going through the turbine. Assume that changes in kinetic energy of the stream passing through the turbine are negligible. Maximum marks will be awarded as follows:

a) A succinct problem statement (1 mark)

b) A plant diagram (2 marks)

c) A T-S diagram showing the actual and isentropic processes with respect to the saturated liquid and vapour lines (4 marks)

d) A list of assumptions made to solve the question (2 marks)

e) A list of physical laws used to solve the question (2 marks)

f) Calculations (24 marks)

1. Find the quality, specific enthalpy and specific entropy of the steam leaving the turbine if we assume isentropic expansion through the turbine. (9 marks)

2. If the isentropic efficiency of the turbine is 86%, find the actual quality, specific enthalpy and specific entropy of the steam leaving the turbine. (9 marks)

3. Calculate the specific work output of the actual turbine (in kJ/kg). (3 marks)

4. Calculate the entropy generated in the turbine (in kJ/kg.K). (3 marks)