Recent Blogs Posts

I have calculated the speed of sound for different fractions of water and steam at 10 Bar.a
with IAPWS 1995 model which is supposed to be very accurate,
software Prode Properties + Excel
the calc's are done in Excel,
in a cell I put the macro

=StrMSS(1)

which returns the speed of sound for vapor, liquid and vapor + liquid mixtures

for water at 453 K 10 Bar.a Prode Properties calculates 1392 m/s

for water (0.999 fraction) + steam (0.001 fraction) at 453.028 K 10 Bar.a Prode Properties calculates 9.73 m/s

for water (0.001 fraction) + steam (0.999 fraction) at 453.028 K 10 Bar.a Prode Properties calculates 470.55 m/s

for steam at 453.5 K 10 Bar.a Prode Properties calculates 501.58 m/s

I am surprised to see those very low values (9.73 m/s) for low values of vapor mass fraction,
I have some tabulated data which confirm the trend but still I am unable to understand the origin of phenomena, could you give some explanations?[/QUOTE]

Tags: liquid, prode, sound, speed, vapor

Categories

Uncategorized

I have found several papers discussing this topic, one is "Improved control valve sizing for multiphase flow" from Hydrocarbon Processing March 200, the authors say "HNE-DS method basically assumes that the flow pattern in the control valve is homogeneous but gas and liquid are not in equilibrium – a non-equilibrium factor N represents the boiling delay"
your comment agrees with this statement.
By the way I found also an interesting thread comparing API PSV formulation for gas flow here

'http://www.cheresources.com/invision/topic/16104-psv-discharging-temperature'

the author has provided a Excel page to compare different procedures

Discharging temperature (PSV outlet)
1) calculated with isentropic + adiabatic flash (the default in nozzle.xls)
2) calculated with adiabatic flash
3) calculated with isentropic flash

Calculated Area
1) rigorous numerical solution of isentropic nozzle
2) API formulation for gas and vapors, ideal cp/cv
3) API formulation for gas and vapors, real cp/cv
4) API formulation for gas and vapors, real cp/cv, Zv = 1

all the required properties are calculated by Prode library , for personal/academic use you can download a free -with limited number of components- copy from 'www.prode.com'

I recommend to read this thread to everyone interested in PSV sizing.
psvcompare1.xls

Tags: flow, gas, hem, liquid, psv

Categories

Uncategorized