Water as a saturated vapor at 400 bar passes through an extr

Water, as a saturated vapor, at 40.0 bar passes through an extremely well insulated valve to a pressure of 10 bar at the rate of 13.4 kg/min. Please find the rate at which entropy is being generated in the water in W/oK.

Solution

>> At P = 40 bar, Water is in Saturated Vapour Form.

At this Stage, entropy, S1 = 6.0697 KJ/Kg-K

and, Enthalpy, H1 = 2800.8973 KJ/Kg

>> Now, at P = 10 bar, Let Quality Factor = x

Now, as it is well insulated, So, H2 = H1 = 2800.8973 KJ/Kg

As, H2 > Hg = 2777.1195 KJ/Kg

So, Here it is superheated Steam

So,

=> S2 = 6.6370 KJ/Kg-K

>> As, Mass Flow rate = 13.4 Kg/min

>> So, Required Entropy Generation Rate = (S2 - S1)*m\" = (6.6370 - 6.0697)*13.4 = 7.6018