Question

3. Sketch a T-v diagram and find the specified state for the following states

a. Propane at critical temp & press find T(°C), p(bar) and v(m3 /kg)

b. Water v=.05 m3 /kg, T=140°C find p(bar)

c. Water at p=30 MPa, T=100°C find v(m3 /kg)

Answer 1

Part (A) :

A T-v diagram for propane is as below : (Created from REFPROP software as sketching it as orginial is quite difficult)

As we know, critical temperature and Critical pressure are those temprature and pressure beyond which there will be direct phase change without saturated mixture, it is actually a top point of dome created by plotting T-v diagram which is infact Tcr = 97 deg C = 370 K and Pcr = 4.23 MPa. These values can be obtained by plotting intermediate plots.

Part (B) :

T-v diagram of Water: (Created from REFPROP software as sketching it as orginial is quite difficult)

If we plot the states mentioned, it can be seen that P = 0.362 MPa = 3.62 bar

Part (C) :

Plotting the states mentioned: P = 30 MPa and T = 100 °C

specific volume = v = 0.00103 (m³/kg)