Nozzle is a steady flow device. So, applying Steady Flow Energy Equation (S.F.E.E.) ,
h1 + v12/2 + Z1g + dQ/dm = h2 + v22/2 + Z2g + dW/dm
Here h1 , h2 → sp. enthalpy at inlet and outlet resp.
v1 , v2 → vel. at inlet and outlet resp.
Z1 , Z2 → elevation of inlet and oulet sections above...