Question

Water is the working fluid in a Rankine cycle with reheat. The turbine and the pump have isentropic efficencies of 80%. Superheated vapor enters the turbine at 10 MPa, 480 °C, and the condenser pressure is 6 kPa. Steam expands through the first-stage turbine to 0.7 MPa and then is reheated to 480°C. Determine for the cycle
(a) the rate of heat addition, in kJ per kg of steam entering the first-stage turbine.
(b) the thermal efficiency.
(c) the rate of heat transfer from the working fluid passing through the condenser to the cooling water, in kJ per kg of steam entering the first-stage turbine.

Answer 1

Answer:

A)  3783.952 kJ/kg

B)  34.5%

C)  2476.67 kJ/kg

Explanation:

A) Determine the rate of heat addition entering the first-stage turbine

Qin ( 1st stage ) =  ( h1 - h6 ) + ( h3 - h2 )

                         = ( 3321.4 - 164.07 ) + ( 3438.566 - 2811.944 )

                         = 3783.952 kJ/kg

h values are gotten from super heated table

B) Determine the thermal efficiency

n = 34.5%

attached below

C) Rate of heat transfer from working fluid passing through the condenser to the cooling water

Qout = h4 - h5

         = 2628.2 - 151.53

         = 2476.67 kJ/kg