Answer to Question #253004 in Mechanical Engineering for lroenz

Question

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 0.007 MPa. The work is 1559 kJ/kg and the thermal efficiency is 41.05%. Find the temperature of the steam leaving the reheater. 

Answer 1

Given work = 1559 KJ/kg

η_h = 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.

S_g2 = 6.625 KJ/kg.K

S₁ = S₂ = S_g2

Entry to reheater in Saturated vapour:

T₂ = 170.5°C

h₂ = h_21g = 27689 kJ/kg.

(h₁ - h₆) + (h₂ - h₃) = 3747.807

(3349.6-170.626) + (h₃ - 2768.9) = 3797.807

h₃ = 3387.773 kJ/kg.

let c_p1v = 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