Consider a steam power plant operating on the Reheat-Rankine cycle. The steam en
ID: 1863429 • Letter: C
Question
Consider a steam power plant operating on the Reheat-Rankine cycle. The steam enters the High pressure turbine at 30 bar; 400degreeC and leaves dry saturated. The steam is then reheated at constant pressure to 400degreeC and expanded through Low-pressure turbine before passing through condenser, in which it condenses to saturated liquid at a pressure of 80 kPa. Determine (a) the thermal efficiency of the cycle, (b) the back work ratio, (c) the net power output for a mass flow rate of 15 kg/'s. [20: M]Explanation / Answer
a)here,P1 = 30 bar = 30 x 10^5 Pa,T1 = 400 oC and P2 = 80 kPa = 80 x 10^3 Pa
we know that
P1/T1 = P2/T2
or T2 = P2 x (T1/P1)
the thermal efficiency is
n = 1 - (T2/T1)
b)the power output is
P = (dm/dt) x s x dT
where (dm/dt) = 15 kg/s,s is specific heat of steam and dT = (T1 - T2)