Question

A 3 m^3 rigid tank contains 10 kg of H2O at 70 C.

a. Determine the specific volume of the system

b. Determine the pressure

c. The phase description and quality (x) if it is in the two phase region (saturated mixture)

d. The mass of each phase of water

e. The specific internal energy (u) of the system

Answer 1

a) Specific volume of the system is given by

b) Pressure we calculate from ideal gas formula

n is number of mole = m/M

M is molar of H2O= 18g/mol=0.018kg/mol

Temprature T= 70+273=343K

and

or

so we calculate

c) For any temprature in a rigid bix both Vapour and liiquiid both states are present which we calculate using x

where vf is specific volume of liquid =-0.001003 m^3/Kg

and vg is specific volume of vapour = 43.36 m^3/kg

so we calculate

4) and mass of vapour we calculate from

5) Specific internal energy of system can be calculated as

where uf and ug is saturated specific internal energy of liquid and vapour at 70 C

which values we can see from table