1 kg of saturated liquid water is contained within a piston cylinder device. The

Question

1 kg of saturated liquid water is contained within a piston cylinder device. The water is expanded in a constant pressure process from 100kPa until it reaches a final volume of 1m3. Determine the following:

a) Temperature of the water at the beginning of process

b) The volume of the water at the beginning of the process

c) The temperature of the water at the end of the process

d) The quality of the water at the end of the process

e) Draw the process on a T-v diagram (label the T and v of state 1 and 2 as well as the line of constant pressure the process passes through)

f) Draw the process on a P-v diagram (label the P and v of state 1 and state 2 as well as the line of constant temperature(s) the process passes through)

Hint: When listing what you know (Given), list all the properties you are given for state 1 and state 2 (Ex. State 1: m1=______, P1=_______, phase of the water is___________, State 2:………). This will help you find the two independent, intensive properties you need to fix each state and answer the questions)

Explanation / Answer

a) Temperature of the water at the beginning of process = saturation temperature at 100 kPa = 99.63 oC

b) The volume of the water at the beginning of the process = 0.001043 m3/Kg = 0.001043 m3

d) The quality of the water at the end of the process

vf = 0.001043 m3/Kg

vg = 1.6938 m3/Kg

v = vf + x*vg = 0.001043 + x*1.6938 = 1

So, x = 0.5898

c) The temperature of the water at the end of the process =  99.63 oC (it will remain same as the final constituents is water vapor mixture at the same pressure)

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