EXAMPLE QUESTION FIRST LAW OF THERMODYNAMICS PART 2

3. A nozzle is supplied with steam having a specific enthalphy of 2780KJ/KG at the rate of
    9.1KG/MIN. At outlet from the nozzle the velocity of the steam is 1070M/S. assuming that the
    inlet velocity of the steam is negligible and that the process is adiabatic , determine :
 
  a) the specific enthalphy of the steam at the nozzle exit.
  b) the outlet area required if the final specific volume of the steam is 18.75 m3/KG.

         h1 = 2780 KJ/KG.            A2, v2 = 18.75 m3/KG
          m = 9.1 KG/MIN
         c2 = 1070 M/S
         c1 = 0
          Q = 0

SOLUTION :

a)  Q-w = [(h2-h1) + (c2^2-c1^2/2)+ g (z2-z1)]m

           0 = [h2-h1+ c2^2/2] m
           0 = h2 - 2780 (10^3) + 1070^2/2
           0 = h2 - 2207550
          h2 = - 2207550 - 0
               = - 2207.55 KJ/KG.

b)  m = c2A2/v2
   
          A2 = mv2/c2
          A2 = (0.152) (18.75) / 1070
                = 2.66 (10^-3) m2.