5 replies to this topic

[kangaris]

Hello,

 

I am trying to obtain data from HYSYS for the design of a heat exchanger. I am having a non-condensing vapour mixture (partially condensible) and I want to cool it down from a temperature where the vapour fraction is 1 to a temperature where vapour fraction is around 0.7. The problem is that HYSYS isn't giving data for viscosity and thermal conductivity at liquid-vapour mixture which is needed for heat transfer coefficient calculations (I can only get at full liquid and full vapour conditions). I don't know then what values and how I am going to get the viscosity and thermal conductivity at 0.7vapour.

 

I will appreciate if someone knows how to help me.

[Bobby Strain]

You should take time to learn how to use HYSYS for your work.

 

Bobby

[serra]

in general for two-phase flow the average values to adopt depend from selected correlations,
for example, popular Rosenhow correlation to estimate nucleate boiling heat transfer requires densities (vapor and liquid), Prandtl number for liquid etc.
I get all these numbers in Excel with Prode Properties (of course Hysys or tables of values should provide equivalent results),
in some cases you may adopt the homogeneous concept to correlate data, for viscosity see for example Dukler (1964),
the homogeneous concept allows to estimate density, enthalpy, entropy and derived properties such as speed of sound etc. see for example
'http://www.cheresour...rbons-mixture/'

[Mahdi1980]

You can use aspen properties to find the required data.

Also, are you sure that Hysys cannot predict viscosity and thermal conductivity of Two-phase fluid?!

As far as I know, by defining an stream and specifying composition and changing thermodynamic properties of this stream ( P,T,VF)

other properties will be determined regardless of vapor fraction.

 

Please check it and let me know the result

 

Mahdi

[kangaris]

Hello, 

First of all thanks for your replies! I have gone into a bit more research to understand some more things. Because my heat exchanger is a partial condenser while there is condensation of non-condesible gas I use Gilmore (1963) formula which correlates the coefficient separately for both liquid and vapour. As a result I have to get the phase properties for viscosity and heat capacity while overall viscosity does not exist (which is obvious). 

 

In addition to that I wanted to ask something else. Because I am adding an ASTM from oil manager, I was adviced to ignore light ends in the oil manager and add them separately as pure components using a mixer prior to the heat exchanger. Does anyone know the reason for that?

[serra]

a non-condensable vapor (at specified t, p) shouldn't condense, make sure to select a suitable thermodynamic model...

with PRODE PROPERTIES for hydrocarbons I prefer extended EOS which gives accurate values for VLE,

you may select a similar option and verify results, 

finally, for characterization of petroleum fractions normally one includes light fractions (if present),

if you have doubts about VLE (and calculated compositions)  as alternative to

include a mixer you may simply define the composition at exchanger inlet and then solve a series of H-P flash operations...