Question

Oxygen enters an insulated 14.2-cm-diameter pipe with a velocity of 60 m/s. At the pipe entrance, the oxygen is at 240 kPa and 20°C; and, at the exit, it is at 200 kPa and 18°C Calculate the rate at which entropy is generated in the pipe.

Answer 1

Entropy generation==0.12 KW/K

Step-by-step explanation:

`s_2-s_1=C_p\ln (T_2)/(T_1)-R\ln (P_2)/(P_1)`

`s_2-s_1=0.891\ln (291)/(293)-0.2598\ln (200)/(240)`

`s_2-s_1=0.0412(KJ)/(kg-K)`

Mass flow rate=
`\rho*(\pi)/(4)d^2V`

`\rho_1=\frac {P_1}{RT_1}`

`\rho_1=\frac {240}{0.2598* 293}`

`\rho_1=3.51(kg)/(m^3)`

mass flow rate=
`\rho_1A_1V_1`

So by putting the values

Mass flow rate=2.97 kg/s

So entropy generation=(2.97)(0.0412)

=0.12 KW/K