Problem # p002

Polytropic Process, Heat + Work

A cylinder closed off by a movable piston contains propane gas at 100 kPa and 300 K occupying initially a volume of 100 ltr ( 1 m³ = 1000 ltr ). The gas is now slowly compressed according to the relation :

p V1.2 = constant

until the pressure reaches 400 kPa. Assume that propane behaves like an ideal gas of molecular weight M=44.1 kg/kmol. (Universal gas constant is 8.3144 kJ/(kmol K) ).

  1. How many kilogram of propane are inside the cylinder ?

  2. What is the volume the gas occupies after the compression ?

  3. What is the final temperature ?

  4. How much work is being done during the compression ?

  5. How much heat is added (removed) during the process ? Assume that the internal energy needed to bring propane from a state 1 to a second state 2 can be calculated according to :

    u2 - u1 = cv ( T2 - T1 )     with cv = 1.49 kJ/(kg K)