Consider the two-stage steam turbine depicted in Fig. Q2. The mass flow rate through both the
turbines is 3 kg/s. Superheated steam enters the first turbine at a pressure of 90 bar, a temperature
of 370 oC, and at the enthalpy h1. Then, outside of the first turbine there is dry saturated steam at 39
bar, which enters the second turbine at the enthalpy h2. Finally, the steam exits the second turbine
at a pressure of 7 bar, the enthalpy h3, and with a dryness fraction of 0.65. Assume no heat losses for
turbine 1, and an overall power loss (due to heat losses) of 78 kW in turbine 2. Making use of the
steady flow energy equation and the steam tables, determine:
a) Write down the steady flow energy equation for turbine 1 and turbine 2, applying the
appropriate simplifications. ]
b)ng steam tables, extract and indicate the values of h1 and h2.s]
c) Using the steam tables, extract and indicate appropriate enthalpy values that is required to
determine the enthalpy h3 at the outlet of the second turbine.
d) Determine the power, P1, developed in turbine 1 ]
e) Determine the power, P2, developed in turbine 1
f) Considering the heat loss and the work done per second in turbine 2, determine the thermal
efficiency, and propose how to optimize it.Consider the two-stage steam turbine depicted in Fig. Q2. The mass flow rate through both the
turbines is 3k(g)/(s). Superheated steam enters the first turbine at a pressure of (90)/(b)ar , a temperature
of 370deg C, and at the enthalpy h_(1). Then, outside of the first turbine there is dry saturated steam at 39
bar, which enters the second turbine at the enthalpy h_(2). Finally, the steam exits the second turbine
at a pressure of 7 bar, the enthalpy h_(3), and with a dryness fraction of 0.65 . Assume no heat losses for
turbine 1, and an overall power loss (due to heat losses) of 78kW in turbine 2 . Making use of the
steady flow energy equation and the steam tables, determine:
a) Write down the steady flow energy equation for turbine 1 and turbine 2, applying the
appropriate simplifications.
[3 marks]
b) Using the steam tables, extract and indicate the values of h_(1) and h_(2).
c) Using the steam tables, extract and indicate appropriate enthalpy values that is required to
determine the enthalpy h_(3) at the outlet of the second turbine.
d) Determine the power, P_(1), developed in turbine 1
e) Determine the power, P_(2), developed in turbine 1
f) Considering the heat loss and the work done per second in turbine 2, determine the thermal
efficiency, and propose how to optimize it.
[5 marks]
Consider the two-stage steam turbine depicted in Fig.Q2.The mass flow rate through both the turbines is 3 kg/s.Superheated steam enters the first turbine at a pressure of 90 bar,a temperature of 370c,and at the enthalpy h.Then,outside of the first turbine there is dry saturated steam at 39 bar,which enters the second turbine at the enthalpy h.Finally,the steam exits the second turbine at a pressure of 7 bar,the enthalpy ha,and with a dryness fraction of 0.65.Assume no heat losses for turbine 1,and an overall power loss(due to heat losses)of 78 kW in turbine 2.Making use of the steady flow energy equation and the steam tables,determine:
a Write down the steady flow energy equation for turbine 1 and turbine 2,applying the appropriate simplifications. [3marks] b) Using the steam tables,extract and indicate the values of h and h [2 marks] c) Using the steam tables,extract and indicate appropriate enthalpy values that is reguired to determine the enthalpy h at the outlet of the second turbine [5marks] p Determine the power,P,developed in turbine 1 [5marks] e) Determine the power,P2developed in turbine 1 [5marks] f) Considering the heat loss and the work done per second in turbine 2,determine the thermal efficiency,and propose how to optimize it. [5marks]
1
2
P=78kW
Fig.Q2:Two-stage steam turbine
