Outlet Velocity of Steam through a Valve 3

[MattC1234]

I am having problems calcualting the outlet velocity of Steam across a valve and am looking for help.

The valve is 24" ANSI 600# (With a body bore of 22") my process conditions are causing some what of a problem to em and are giving very high outlet velocities, but these do not take into acount the temperature change of the steam during the pressure reduction stage.

The flow rates for the steam are 165000 and 235000 kg/hr and require pressure control from 64.7 Barg to 0.24 Barg with an inlet temperature of 282 Deg C. The ratio of specific heats is 1.86. Can anyone help me with the calculation for the temperature of the fluid at outlet and thus help me with the velocity calculation?

Any help would be appreciated. I am assuming using steam tables that the steam would be superheated as from an enthalpy entropy diagram it would be above the saturation line.

Cheers

 

[ione]

The link below is for a calculator of the isentropic exponent of water and steam.

http://twt.mpei.ac.ru/OCHKOV/WSPHB/WKDiag15.html

The isentropic exponent is described as:

k = - V/P *(dP/dV) at constant entropy

and it derives from:

P*V^k = constant

Passing to the logarithm

LogP + k*logV = constant

Differentiating

dP/P + k* dV/V = 0

k = - V/P *(dP/dV)