At 80°C, water has vf = 0.0010291 m3/kg and vg = 3.407 m3/kg. The water occupies a volume of 0.05 m3. For each mass value below, determine whether the water is a compressed liquid, saturated liquid, saturated mixture, saturated vapor, or superheated vapor and the quality of the water:

Question

(a) 60 kg
(b) 5 kg
(c) 0.025 kg
(d) 0.0147 kg
(e) 0.0095 kg

Given: vf = 0.0010291 m3/kg; vg = 3.407 m3/kg; V = 0.05 m3

What will be an ideal response?

Answer 1

(a) m = 60 kg: v = V/m = 0.000833 m3/kg
As v < vf, this is a compressed liquid (quality is undefined).

(b) m = 5 kg: v = V/m = 0.01 m3/kg
As v < vf, this is a compressed liquid (albeit very slightly. Answering a saturated liquid with a quality of 0 is also acceptable).

(c) m = 0.025 kg: v = V/m = 2 m3/kg
As vf < v < vg, this is a saturated mixture. x = (v – vf) / (vg – vf) = 0.587

(d) m = 0.0147 kg: v = V/m = 3.401
As vf < v < vg, this is a saturated mixture, although v is very close to vg, and an answer of saturated vapor with x = 1.0 is acceptable. Technically, x = (v – vf) / (vg – vf) = 0.998

(e) m = 0.0095 kg: v = V/m = 5.26 m3/kg
As v > vg, this is a superheated vapor (quality is undefined).