Question

Thermodynamics

Calculate the internal energy and enthalpy variations of an ideal gas (in BTU / lb) when it changes state from 50 °C to 150 °C, with gas properties k = 1.4

Answer 1

Δu= 29.82 Btu/lb

Step-by-step explanation:

Given that gas temperature changes from 50 °C to 150 °C.

K=1.4

We know that

`C_P-C_v=R`

`C_P/C_v=K`

K=1.4 it means that it is air.

We know that for air

`C_v=0.71\ KJ/kg.K`

We know that internal energy for gas given as

`\Delta u=C_v\Delta T` KJ/kg

Δu= 0.71 x (150-50) KJ/kg

Δu=71 KJ/kg

We know that

1 KJ/kg=0.42 Btu/lb

So 71 KJ = 29.82 Btu/lb

Δu= 29.82 Btu/lb