Steam at 500 bar and 500°C undergoes a throttling expansion to 1 bar. What will be the temperature of the steam after the expansion? What would be the downstream temperature if the steam were replaced by an ideal gas, CP/R = 7/2?

T1=T2=500°C

Explanation:

Given-

Pressure, P1 = 500 bar

Temperature, T1 = 500°C

P2 = 1 bar

T2 after expansion, = ?

We know,

P1/T1 = P2/T2

500 / 500 = 1/T2

T2 = 1°C

If the steam were replaced by an ideal gas, since enthalpy of ideal gas is a function of temperature only, we easily obtain T2 = T1 = 500°C