In an experimaental set-up, air flows between two stations P and Q adiabatically. The direction of flow depdns on the pressure and temperature conditions maintained at P and Q. The conditions at P are 150kPa and 35K. The temperature at station Q is 300K. The following are the properties and relations pertaining to air:
Specific heat at constant pressure,
Specific heat at constnat volume,
Characteristic gas constnat,
Internal energy, u=cvT.
If the pressure at station Q is 50kPa, the change in entropy (sQ−sP) in kJ/kgK is