Question

A steam turbine has inlet steam pressure p₁ = 1.4 MPa absolute. Inlet steam temperature is T₁ = 400 ^oC. This corresponds to inlet enthalpy per unit mass of h1 = 3121 kJ/kg. Exit pressure of the steam is p₂ = 101 kPa absolute. Exit steam temperature is T₂ = 100 ^oC. This corresponds to exit enthalpy per unit mass of h₂ = 2676 kJ/kg. Inlet speed of the steam is V₁ = 15 m/s and exit speed is V₂ = 60 m/s. Axis of the steam turbine is horizontal. Time-rate of heat loss through the walls of the turbine is Q = 7600 kJ/h. The mass flow rate of steam through the turbine is 0.5 kg/s.

a) If the power extracted by the turbine is P_actual = 200 kW, what is the amount of power loss (expressed in kW) due to viscous effects?

b) If there would be no viscous losses, what would be the ideal power, P_ideal, extracted by the turbine (in kW)?

c) What is the coefficient of efficiency, ?, of the turbine?

Answer 1