please answer both questions A real turbine with a mass flow rate of 5.0 kg/s of

Question

please answer both questions

A real turbine with a mass flow rate of 5.0 kg/s of steam has inlet conditions of 6.0 MPa and 700 degree C, and exit conditions of saturated vapor at 50 kPa. If the power output of the turbine is 5.0 MW, determine the rate of heat loss from the turbine to 3 significant figures in kW. Assume the inlet/outlet kinetic and potential energy changes are negligible. For problem (1) above, determine the increase in specific entropy of the steam as it flows through the turbine (units of kJ/kg K).

Explanation / Answer

At 6 MPa and T = 700 deg,From steam tables

h1 = 3894.28 KJ/kg

s1= 7.4324 KJ/kg.K

At 50 Kpa,From steam tables at saturated vapor conditions)

T2 = 81.33 deg

h2 = 2645.87

s2 = 7.5939 KJ/kg.K

Ideal Power by turbine = Wideal = m*(h1-h2) = 5*(3894.28-2645.87) = 6.242 MW

Given

Real turbine output = Wreal = 5 MW

Wideal = Wreal + Heat loss(Qloss)

Qloss = 1.242 MW = 1242 KW = 1240 KW (significant fig)

S = m*(s2-s1) = 5*( 7.5939 - 7.4324) = 0.8075 KW/K

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