Oil/water mixture

[FFEA]

Hello all,

I am trying to calculate the inside heat transfer coefficient for a 4 in diameter pipe transporting an crude oil/water mixture.
The crude oil is API 20° and two mixtures are to be analyzed, one for a 50% water cut and the other for a 70% water cut.
I don't know how to determine the viscosity and thermal properties of the mixture.

Please help. Thanks!

 

[georgeverghese]

In the real world, you may find that transient inventory in the HX is sometimes mostly oil and sometimes mostly water, so calculating the inside htc based on 100% oil would be conservative.

Beware of the properties of this oil at the lowest film temp the calcs predict - viscosity may be high and also check if wax could precipitate out, forming an insulating layer on the tube id.

 

[FFEA]

georgeverghese,

Do you think it would be conservative to calculate the inside htc based on 100% oil?
I read in some places that the viscosity of the oil/water mixture has a greater value than that of its separate components. Have you heard about this?

Thanks for your response.

 

[LittleInch]

I don't think you have the necessary info based on the above.

"mixture" is very vague - Is this a homogenous emulsion? separate? stratified? slug like? Is it fully formed before going into the pipe or mixed in the pipe.

Oil / water mixes are quite complex and very specific to the oil concerned. Above some percentages it all separates in some oils.

Flow rate / velocity becomes important. Is this truly a single phase liquid or have you got gas breakout from the crude?

What temperature is it running at?

Why is this important? a 4" pipe is small - without good insulation it will rapidly get to ambient conditions.

Without physical testing of samples you're just guessing IMHO

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

Yes, I've read about this too, but I must confess that I had chosen to ignore this information when I had to do design work many years ago similar to what you are working on now.

For press drop through the tube bank, the all water case may be controlling, unless you have high oil viscosity.

As Little Inch cautions, also check for gas break out in this mix if this is a crude heating application.