Question

During methane liquefaction, about 1000 kg of methane are stored at a pressure of 10 Mpa and 180 K. The plant manager is worried about the possibility of an explosion. Determine the energy released by a sudden rupture of this storage tank and the temperature and physical state of the methane immedeately after the rupture. -couldn't find the final temperature from the mollier diagram in my book

Answer 1

To explain how to find out the enthalpy of phase change from mollier diagram,the blue contour lines shows enthalpy at different temperatures ,at a given pressures,while the red contour lines shows entropy changes at different T,P.

The regions=

A=liquid –vapour equilibrium

B=liquid region

C=vapour phase

D=supercritical fluid

Greem line=supersaturated liquid

Orange=supersaturated vapour

Red point=critical point (all three phases in equilibrium)

At 10 Mpa ,180K=-93 deg C(K=273+C) ,∆H=-600kj/Kg K

At 10 Mpa,post-explosion,vapour is formed t T=55 deg C=333 K , ∆H=-420KJ/K g K

Difference of enthalpy is released=-420-(-600)=180KJ/Kg K

For 1000 kg

Heat released=180KJ/Kg K *1000Kg*(333-180K)=27540000 KJ