Initially, an insulated rigid tank contains 3.86 kg of water at 265 o C and 1 MP

Question

Initially, an insulated rigid tank contains 3.86 kg of water at 265oC and 1 MPa. A heater in the wall of the tank maintains the wall temperature at 600oC. After a period of time, the pressure in the tank rises to 1.5 MPa. Determine the total entropy generation (kJ/K) during this process.

Hint: The following formulas will prove useful in solving this problem:

Since Tb is constant, then S2 - S1 = Q / Tb + Sgen

m*(s2 - s1) = Q / (600+273.15) + Sgen

Sgen = m*(s2 - s1) - Q / (600+273.15)

Correct Answer :

Correct Answer : 0.1623 ± 2%

Explanation / Answer

Taking whole system then we have Q=0 as insulated

so we have 3.86*(s2 - s1)

s1 = 6.956 and s2 = 7.112

so answer is 0.60488

For Turbine we have from the steamtables

at inlet of turbine we have 6.0833

at outlet we have 6.9656

so total entropy generation is 0.1623 kJ/kg-k

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