Question

A First Stage in a turbine receives steam at 10 MPa, 800 C with an exit pressure of 800 KPa. Assume the stage is adiabatic and reversible. Find the exit temperature and the specific work.

Answer 1

Answer

given,

P₁  = 10 MPa                 T₁ = 800

P₂ = 800 KPa               T₂ = ?

Using formula

$\dfrac{T_2}{T_1} = (\dfrac{P_2}{P_1})^{\dfrac{n-1}{n}}$

For steam   n = 1.33                    

$\dfrac{T_2}{800+273} = (\dfrac{800\times 10^{3}}{10\times 10^{6}})^{\dfrac{1.33-1}{1.33}}$

T₂ = 573.368 K                    

T₂ = 573.368 - 273 = 300.368 °C

$W = \dfrac{P_1V_1-P_2V_2}{n-1}$

          =$\dfrac{mR(T_1-T_2)}{n-1}$

          =$\dfrac{1\times 0.287\times (800 - 300.368)}{1.33-1}$

      W = 434.53 kJ/kg