Steam enters a turbine operating at a steady state at 8 MPa and 700 degree C. Th

Question

Steam enters a turbine operating at a steady state at 8 MPa and 700 degree C. The mass flow rate of the steam is 135 kg/mm. The steam exits the turbine as a saturated vapor at 18 kPa. The turbine produces 2.2 MW of power. Ignoring potential and kinetic energy effects determine the: Rate of heat transfer from the turbine to the environment in kW Rate of entropy production in kW/K for an enlarged control volume that includes the turbine and enough of its surroundings that the heat transfer occurs at the ambient temperature of 25 degree C. Hint! Assume that the environment acts as a reservoir. Whot does this imply relative to the temperature? Ans. 3.747 kW/K

Explanation / Answer

P1=8Mpa T1=700c m.=135kg/min=2.25kg/sec

superheated region:

h1= 3882.2kj/kg s1=7.2822kj/kg.k

satureted vapor:

p2=18Kpa =>h,g2=2604.66kj/kg s,g2=7.94722kj/kg.k

turbine produces 2.2 Mw of power

one inlet and one outlet so m1.=m2.=m.

a)rate of heat transfer from the turbine to the environment:

m.h1=m.(h,g2)+W.+2.2MW=>W.=8734.95kW-5860.485kW-2200kw=674.465kW

b) @25C surrounding temp. S,g=8.9kj/kg.k

rate of entropy production:

m.(S,g-s1)=2.25(8.9-7.2822)KW/k=3.64KW/K

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