Question

Five kg of nitrogen gas (N2) in a rigid, insulated container fitted with a paddle wheel is initially at 300 K, 150 kPa. The N2 gas receives work from the paddle wheel until the gas is at 500 K and 250 kPa. Assuming the ideal gas model with a constant specific heat (i.e., use a constant specific heat of N2 at 300K), neglect kinetic energy and potential energy effects
Required:
a. Draw a system schematic and set up states.
b. Determine the amount of work received from the paddle wheel (kJ).
c. Determine the amount of entropy generated (kJ/K).

Answer 1

Answer:

A) attached below

B) 743 KJ

C) 1.8983 KJ/K

Explanation:

A) Diagram of system schematic and set up states

attached below

B) Calculate the amount of work received from the paddle wheel

assuming ideal gas situation

v1 = v2 ( for a constant volume process )

work generated by paddle wheel = system internal energy

dw = mCv dT .     where ; Cv = 0.743 KJ/kgk

     = 5 * 0.743 * ( 500 - 300 )

     = 3.715 * 200 = 743 KJ

C) calculate the amount of entropy generated  ( KJ/K )

S2 - S1 = 1.8983 KJ/K

attached below is the detailed solution