An ideal reheat turbine with one stage of reheat receives steam at 8.0 MPa,
480°C. Reheat pressure is 0.83 MPa and exhaust pressure is 0.007MPa. The
work is 1559 KJ/kg and the thermal efficiency is 41.05%. Find the
temperature of steam leaving the reheater.
Given work = 1559 KJ/kg
ηh = 41.05%
When, steam is stable at P₁ = 8 MPa, T1 = 480°C
h1 = 3319.6 KJ/kg; S = 6.6613 KJ/kg.K at P2 = 0.83 Mpa.
Sg2 = 6.625 KJ/kg.K
S1 = S2 = Sg2
Entry to reheater in Saturated vapour:
T2 = 170.5°C
h₂ = h21g = 27689 kJ/kg.
(h1 - h6) + (h2 - h3) = 3747.807
(3349.6-170.626) + (h3 - 2768.9) = 3797.807
h3 = 3387.773 kJ/kg.
let cp1v = 2.1 kJ/kg.K
h3 = 3387.733 kJ/kg.K
From Superheated steam tables corresponding to h3 = 3387.733 kJ/kg.K, and
P3 = 0.83Mpa
T3 = 454°C