Question

Calculate the hfg and sfg of steam at 120oC from the Clapeyron equation, and compare them to the tabulated values.

Answer 1

Answer:

The tabulated values at 120 C of hfg = 2202.1 kJ/Kg and sfg = 5.6

kJ/Kg.K

Explanation:

According to Clapeyron Equation :

$h_{fg}=TV_{fg}\left (\frac{\partial P}{\partial T} \right )_{sat}$

$=T(V_{g}-V_{f})_{120^{0}}\left ( \frac{\Delta P}{\125^{0}-115^{0}} \right )$

Taking P2 at temperature 125 and P1 at 115 degree Celsius .

T = 120 + 273.15 = 393.15 K

P2 = 232.23 kPa and P1 = 169.18kPa

(these are experimental values given in the Data)

$= 393.15(0.88133 -0.001060\ m^{3}/Kg)\frac{232.23-169.18 kPa}{10}$

$h_{fg} = 2206.8 kJ/Kg$

$S_{fg}=\frac{h_{fg}}{T}$

$\frac{2206.8}{393.15}$

= 5.6131 kJ/Kg.K

The tabulated values at 120 C of hfg = 2202.1 kJ/Kg and sfg = 5.6131

kJ/Kg.K