Question

Steam generated in a power plant at a pressure of 8,600 kPa and temperature of 600°C is fed to a turbine. Exhaust from the turbine is 10kPa. The pump operates at 75% efficiency. The turbine operates at 70% efficiency.

a. Determine the power required for the pump. Assume q=0 at pump.

Answer 1

The process is an adiabatic process

the PT relationship for this process is given by

Here we know

P1 = 8600 KPa , T1 =600 oC = 873.15 K

P2 =10 KPa

for steam gamma = 1.3

we will make use of above equation to evaluate T2

T2 =126.67 oC

now at P = 8600 KPa and T = 600 oC, H1 =3637.4752 KJ/Kg

at P =10 KPa and T =126.67 oC, H2 =2738.325 KJ/Kg

Now, Ideal power requirement = 3637.4752 - 2738.325 = 899.1502 KJ/Kg

The efficiency is 70 %

Hence actual power requirement = 0.7*899.1502 =359.66 KJ/Kg