Answer:
a) the mass flow rate of the steam is 
b) the exit velocity of the steam is 
c) the exit area of the nozzle is
= 0.0015435 m²
Explanation:
Given that:
A steam with 5 MPa and 400° C enters a nozzle steadily
So;
Inlet:
5 MPa
= 400° C
Velocity V = 80 m/s
Exit:
2 MPa
= 300° C
From the properties of steam tables at
5 MPa and
= 400° C we obtain the following properties for enthalpy h and the speed v

From the properties of steam tables at
2 MPa and
= 300° C we obtain the following properties for enthalpy h and the speed v

Inlet Area of the nozzle = 50 cm²
Heat lost Q = 120 kJ/s
We are to determine the following:
a) the mass flow rate of the steam.
From the system in a steady flow state;

Thus




b) the exit velocity of the steam.
Using Energy Balance equation:

In a steady flow process;










c) the exit area of the nozzle.
The exit of the nozzle can be determined by using the expression:

making
the subject of the formula ; we have:


= 0.0015435 m²