Problem # p019

Open System. Entropy

An ideal gas (R=0.29 kJ/(kg K) with constant specific heat, cp=1.0 kJ/(kg K)), is streaming through a pipe. The pressure in the entrance and exit plane are equal ( = 2 MPa ) while the temperature changes from 40oC to 600oC due to heat transfer into the pipe.
The mass flowrate is 1.5 kg/sec.
Neglecting changes in kinetic and potential energies, determine :
  1. The amount of heat per second transferred into the pipe.

  2. If the process of heat transfer is performed in a reversible manner what would the entropy change of the gas be if we assume that the heat is transferred to the gas at a mean temperature of 320oC ? ( Hint : integral dQ/T )

  3. Determine the actual change in entropy of the gas.

  4. What should the relationship between the results from 2. and 3. be ? Circle one of the following :
    Equal   ||   2 greater 3   ||   3 greater 2