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Author: Subject: Any Mechanical Engineers out there?
luke_stephenson

posted on 15/2/10 at 06:05 PM Reply With Quote
Any Mechanical Engineers out there?

good evening all,

Maybe someone could help with the following question; the dynamic viscosity of water changes with temperature (known) however does it change with pressure? i need to know the dynamic viscosity of water @110 celsius 7Bar pressure

cheers

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Bob C

posted on 15/2/10 at 06:21 PM Reply With Quote
I can't see why it should vary with pressure - 7 bar is not that exotic. I assume you mean kinematic viscosity (visc/density). OK density will increase ever so slightly with presure.
And if you need it for doing some kind of hydrodynamic simulation other errrors & assumptions will dwarf any physical constant errors!

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Nash

posted on 15/2/10 at 07:10 PM Reply With Quote
quote:
Originally posted by luke_stephenson
good evening all,

Maybe someone could help with the following question; the dynamic viscosity of water changes with temperature (known) however does it change with pressure? i need to know the dynamic viscosity of water @110 celsius 7Bar pressure

cheers


It's steam at 110 deg C and 7 bar?!?!?!?

...........Neil





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liam.mccaffrey

posted on 15/2/10 at 07:10 PM Reply With Quote
I was reading an article about this the other day in New Scientist. I think it does change but I can't say for sure.





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jos

posted on 15/2/10 at 07:16 PM Reply With Quote
does this help

http://www.engineeringtoolbox.com/water-dynamic-kinematic-viscosit y-d_596.html





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Breaker

posted on 15/2/10 at 07:19 PM Reply With Quote
quote:
Originally posted by Nash
quote:
Originally posted by luke_stephenson
good evening all,

Maybe someone could help with the following question; the dynamic viscosity of water changes with temperature (known) however does it change with pressure? i need to know the dynamic viscosity of water @110 celsius 7Bar pressure

cheers


It's steam at 110 deg C and 7 bar?!?!?!?

...........Neil


If the water is pressurized, it will not vaporize at 110 C. Otherwise lots of cars will have steam cooling instead of water cooling.

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flak monkey

posted on 15/2/10 at 07:20 PM Reply With Quote
quote:
Originally posted by Nash

It's steam at 110 deg C and 7 bar?!?!?!?

...........Neil


Nope still a liquid I think at that pressure and temperature.





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will121

posted on 15/2/10 at 07:35 PM Reply With Quote
quote:
Originally posted by flak monkey
quote:
Originally posted by Nash

It's steam at 110 deg C and 7 bar?!?!?!?

...........Neil


Nope still a liquid I think at that pressure and temperature.


definately still be a liquid, cant get my steam tables out of the loft be covered in 20years of dust, but we run high temp Hot water heating systems upto 150degC @10bar,

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luke_stephenson

posted on 15/2/10 at 08:26 PM Reply With Quote
with ref to engineers toolbox, thankyou, id already checked there tho. v.good site!
afraid its definately still in the liquid state, saturation temp @ 7 bar is 165celsius.

ok so this is my theory, as shown in the engineers toolbox and other sites the dynamic viscosity which is different to kinematic viscosity varies with temperature @ atmospheric pressure. however the chart only goes to 100c obviously as the water will boil. and it is shown that as the water nears boiling point the dynamic viscosity lowers.

all well and good, but the 7bar pressure would effectively have the water in a totally different state as it would not be near boiling point. its got me well stumped.

unfortunately i need it to get a reliable reynolds number to allow accurate heat transfer calcs and more importantly accurate scaling of the proposed heat exchanger.

im well and truely stuck!

thanks for all the input so far

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Nash

posted on 15/2/10 at 08:49 PM Reply With Quote
quote:
Originally posted by will121
quote:
Originally posted by flak monkey
quote:
Originally posted by Nash

It's steam at 110 deg C and 7 bar?!?!?!?

...........Neil


Nope still a liquid I think at that pressure and temperature.


definately still be a liquid, cant get my steam tables out of the loft be covered in 20years of dust, but we run high temp Hot water heating systems upto 150degC @10bar,


I thought 110 was a turning point?! So I found this and I was wide of the mark

Steam tables
Steam tables


It is about 150 by the look of things

.......Neil





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Ivan

posted on 15/2/10 at 08:51 PM Reply With Quote
This is where I normally pick up the phone and phone the Varsity and ask to speak to the relevant Prof - normally they are very happy to help if you approach them civilly and explain your problem.
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