| The Breakroom > The Water Cooler |
| Viscosity - a question with pur'Poise' ? |
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| John Rudd:
This is more appropriate than magic numbers and school theorems...... My dad was a vehicle body refinisher....To get the paint to the right consistency ( viscosity...) He would thin it with the appropriate thinners and run a sample through a special funnel ( fixed volume)..and use a stop watch to time the liquid fall... Hope this helps.. |
| awemawson:
Funny that John - years ago I made a 'dipper' for the same purpose. It comprised a 3" length of 1" copper pipe with a copper disk soldered on the bottom through which a short length of 1/4" pipe protruded axially. I soldered a length of the same 1/4" pipe to the 1" tube as a handle allowing me to dip it into a paint mixing can to test dilution. I actually squashed the end of the 1/4" pipe a bit to slow the flow and extend the time. A quick glance at your watch as it flows out tells you if you have added enough thinners. Worked a treat and avoided juggling funnels and having multiple containers to pour out of and into. |
| dsquire:
--- Quote from: awemawson on July 09, 2013, 04:52:18 PM ---Funny that John - years ago I made a 'dipper' for the same purpose. It comprised a 3" length of 1" copper pipe with a copper disk soldered on the bottom through which a short length of 1/4" pipe protruded axially. I soldered a length of the same 1/4" pipe to the 1" tube as a handle allowing me to dip it into a paint mixing can to test dilution. I actually squashed the end of the 1/4" pipe a bit to slow the flow and extend the time. A quick glance at your watch as it flows out tells you if you have added enough thinners. Worked a treat and avoided juggling funnels and having multiple containers to pour out of and into. --- End quote --- I wish that I had heard about this 35 years ago when I was into painting cars. It would have been much better than watching the paint drip off the stir stick until you figured that you had the right consistency. :Doh: Cheers :beer: Don |
| awemawson:
It was probably 35 years ago I did it :lol: |
| David Jupp:
As well as the inverse of viscosity ratio, you may also have to allow for differences in fluid density. The density will alter the driving force available due to gravity. If fluid densities are close then don't worry too much. It gets much trickier if the viscosities are such that flow with one fluid is laminar, and turbulent with the other. Chemical Engineering is not the most precise of disciplines, so don't expect any perfect answers... |
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