# Vapor Fraction

1. Sep 10, 2014

### MuzMond

Hello,
Long time lurker, 1st time poster.

I need a sanity check that I am solving this problem correctly.

I have a pipe with a combination of gas and liquid flowing through it, the density of the gas (ρg) is 5.5kg/m^3, the density of the liquid (ρL) is 435 kg/m^3.

I have a vapor fraction (vf) of 0.92
I also have a flow rate of 5000kg/hr.

The combined density ρc = ρg*vf + ρL(1-vf) = 5.5*0.92 + 435*0.08 = 5.06+34.8=39.86 kg/m^3.

Is the combined density per the method shown above, or do I use the volume flow rate Q to determine the combined density.

flow of liquid = 5000*0.08 = 400kg/hr
flow of gas = 5000*0.92 =4600 kg/hr
dividing by densitys to get volume flow,
Q liquid = 0.091 m^3/hr
Q gas = 836.36 m^3/hr

Combined volumetric flow = 836.36+0.091 = 836.451 m^3/hr
As total mass flow is 5000 kg/hr.
Density is mass/vol
Combined density = 5000/836.451 = 5.98 kg/M^3.

Any advice would be welcomed.

MM

2. Sep 10, 2014

### bigfooted

in the first method, you assume that the vapor fraction is a volume fraction. In the second approach, you assume that it is a mass fraction.

Does 0.92 mean that 92% of the volume is gas or does it mean that 92% of the mass is gas?