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Re: [Phys-l] transformer question



Bernard Cleyet wrote:
... searching for the validity limit of Poiseuille's law [length/ diameter > ?] ... anyone know if (length / diameter) > 10 is "good"? I suppose it'll vary according to the flow rate (changing the Reynolds' #), etc.
Apparently not....
According to this URL
<http://books.google.com/books?id=6pSXSvGwOqAC&pg=PA201&lpg=PA201&dq=hagen+poiseuille%27s+law&source=bl&ots=DhU6_h3Zl3&sig=PTtHV0yiG7MQBhXBfh_KojUVRww&hl=en&ei=4FuHSv7rEIesMLm6-eME&sa=X&oi=book_result&ct=result&resnum=10#v=onepage&q=&f=false>
or
http://tinyurl.com/rd3sj9
...which is a Google Books offering of the Instrument Engineer's Handbook,
starting at P201 for Poiseuille style flow meters.

On P203 are design rules for reasonable linearity of such capillary flow meters. Briefly, for Re less than 500 in the laminar regime, the L/D of the capillary should > 0.3 Re for reasonable linearity. This is in part associated with avoiding objectionable entrance effects.

Brian W