Mixing of fluids having different densities
Mixing of fluids having different densities
(OP)
Hi,
I am doing a pressure drop calculation for my project where there is a mixing of two fluids having densities of 980 Kg/m3 & 850 Kg/m3. Flow rates are 400 m3/hr & 120 m3/hr respectively. I am unsure of what the outlet flow rate will be. If we consider the volumetric flow rate, the outlet should be 520 m3/hr, but if we convert these into mass flow, then the flow rate will be 392000 + 102000 = 494000 Kg/hr which comes to 504 m3/hr. So how should I calculate the outlet flow rate & what will be the density of the mixed fluid that I should consider as this will also impact the pressure drop.
I am doing a pressure drop calculation for my project where there is a mixing of two fluids having densities of 980 Kg/m3 & 850 Kg/m3. Flow rates are 400 m3/hr & 120 m3/hr respectively. I am unsure of what the outlet flow rate will be. If we consider the volumetric flow rate, the outlet should be 520 m3/hr, but if we convert these into mass flow, then the flow rate will be 392000 + 102000 = 494000 Kg/hr which comes to 504 m3/hr. So how should I calculate the outlet flow rate & what will be the density of the mixed fluid that I should consider as this will also impact the pressure drop.





RE: Mixing of fluids having different densities
Good luck,
Latexman
Technically, the glass is always full - 1/2 air and 1/2 water.
RE: Mixing of fluids having different densities
I think the fluids will mix together without any reaction or heat effect, the fluids are Fuel oil & Diesel, can you advise on this?
RE: Mixing of fluids having different densities
The mixture density would be 494,000 Kg/hr / 520 m3/hr = 950 kg/m3.
Good luck,
Latexman
Technically, the glass is always full - 1/2 air and 1/2 water.
RE: Mixing of fluids having different densities
I was interested in where your 504 m3/hr came from. If I divide the mass flow rate by your 504 m3/hr I get 980 kg/m3. Did you really think that the mixed stream would have the density of the predominant component? That the minor component would somehow be promoted to that density? You have to use a weighted average density. If you use a density of:
(980*400+850*120)/(400+120) = 950 kg/m3
Then the mass flow rate of the incompressible fluid matches the volume flow rate as required.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: Mixing of fluids having different densities
Note, this only works when the two mixtures are being pumped BEFORE mixing. once you mix it, your pump will react differently as will your system curve which will change depending on the combined viscosity. The density of the mixture will affect the pressure exerted by the same head, but directly shouldn't affect the pressure drop per se.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Mixing of fluids having different densities
RE: Mixing of fluids having different densities
Also account for temp changes if these 2 streams are not at the same temp; for which Cp mix is a weight averaged sum of the 2 streams, assuming the mix remains at below bubble point temp.
Any temp changes may have some slight effect on mix density.
RE: Mixing of fluids having different densities
RE: Mixing of fluids having different densities
Your post got me interested in learning more about the mechanism of the shrinkage. I looked in Shrinkage Losses Resulting from Liquid Hydrocarbon Blending and found
Even though mixing two crude oils is far more complex than the sand filling the void space between the marbles, it still really helped me get my head around the concept. The equations from The Manual of Petroleum Measurement Standards Chapter 12 Section 3 were illuminating as well. It is so easy to forget that crude is not water.
The linked article also explains how to calculate mixture density (which is close, but not exactly the number you get from the weighted average approach that you would use for two liquids that were less complex).
Thanks for sharing.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: Mixing of fluids having different densities
It is far more important to consider that then compressibility for example.