Answer to Question #128449 in Mechanical Engineering for Afra Syab

Question

Determine the final volume of a mixture of water and steam if 3 kg of water is heated at a constant pressure until the quality is 60 percent. The pressure is (a)25 kPa and (b)270 kPa.
Ans. (a) 11.6 mZ (h)1.24 m3

Answer 1

a) The pressure (p)=25kPa=0.025MPa

Mass(m)=3kg

quality (X)= 0.60

From steam table at P=0.025MPa

Specific volume of saturated water (vf)=0.001019m3/kg

Specific volume of saturated steam (vg)=6.4353 m3/kg

Therefore, the volume of steam having X=0.6 is given by

V=m[vf+X(vg-vf)]

=3[0.001019+0.6(6.4353-0.001019)]

= 11.58m3.

b)The pressure (p)=270kPa=0.270 MPa

Mass(m)=3kg

quality (X)= 0.60

From steam table at P=0.270 MPa

Specific volume of saturated water (vf)=0.001069m3/kg

Specific volume of saturated steam (vg)=0.66865 m3/kg

Therefore, the volume of steam having X=0.6 is given by

V=m[vf+X(vg-vf)]

=3[0.001069+0.6(0.66865-0.001069)]

=1.2048m3