If I have a tank 22" high with a tube at the bottom (size 1/4" pipe). How do I calculate how much pressure I have at the tube and how the pressure will change as I change the specific gravity of the liquid in the tank changes. Thanks, Stan
Height times the density of the substance.
Thanks, If I had water in the tank would that be 22" of water (or 0.795 PSI) pressure deferential? Stam
The pressure at the bottom of a column of water, if it's open to the atmosphere at the top, is the "static head." It's equal to approximately one psi for each 2.31 feet (27.8") of water column. The pressure at your 1/4" pipe, therefore, is a little less than 2 psi.
If you change the specific gravity of the fluid, just multiply the pressure you would have with water (specific gravity = 1) by the specific gravity of the new fluid (mercury, for example, has a specific gravity of 13.546).
These figures are rounded a little bit but it sounds like they're within the range of accuracy you're looking for. If you need real accuracy, let us know.
-- Ed Huntress
Correction, I meant a little less than 1 psi.
-- Ed Huntress
Just be sure to keep your units consistent. :-) ...lew...
If memory serves me, I believe one cubic inch of water weighs .0361 lbs. The height of the column, times this number, should give you PSI unless I'm mistaken.
Thanks for the help. Stan
There aren't enough of us former physics teachers on this group.
The pressure in the vessel is rho*g*h where rho is the density of the fluid, g is the local gravitational constant, and h is the height of the unpressurized surface above the measure point.
If, and only if, you use 'pounds per cubic foot' types of measurements, your liquid is NOT characterized by density or by specific gravity, but you have included also the 'g' gravity constant in that quantity. Folk using metric measures (grams, centimeters, and such) do NOT have any equivalent way to sweep the gravity constant under the rug.
g= 9.8 meters/sec**2 = 32 ft/sec**2 is often close enough, near sea level on Terra.
The pressure for water would be .433psi per foot of height. Adjust for other liquids by multiplying .433 times the specific gravity.
And thank God that we all do not all have to think in terms of Greek alphabets and boundary theory .
Hmmm, but only on Terra? Physics obviously isn't all its cracked up to be ;). GCC
Heh. When you get past the theory, most things really ARE pretty simple.
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