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Two Fluid Manometer

IP.com Disclosure Number: IPCOM000092030D
Original Publication Date: 1968-Aug-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Dreyfus, RW: AUTHOR

Abstract

The manometer uses two fluids instead of one to attain pressure readings. The two fluids 2 and 4 differ in density by about 10% with the denser fluid 4 supporting the less dense fluid 2. One fluids contains a colored substance so that interfaces 6 and 6' can be readily distinguished. The free liquid surfaces h1 and h2 are displaced at a position of large tube diameter. The height change delta h is small per unit of fluid transferred from one side of the U-tube to the other. This small height change corresponds to an essentially negligible back pressure. By having the two fluids be of nearly equal densities, changes in the relative height delta l of the two liquid-liquid interfaces also produces negligible back pressure.

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Two Fluid Manometer

The manometer uses two fluids instead of one to attain pressure readings. The two fluids 2 and 4 differ in density by about 10% with the denser fluid 4 supporting the less dense fluid 2. One fluids contains a colored substance so that interfaces 6 and 6' can be readily distinguished. The free liquid surfaces h1 and h2 are displaced at a position of large tube diameter. The height change delta h is small per unit of fluid transferred from one side of the U-tube to the other. This small height change corresponds to an essentially negligible back pressure. By having the two fluids be of nearly equal densities, changes in the relative height delta l of the two liquid-liquid interfaces also produces negligible back pressure. Thus a small pressure differential results in a relatively large transfer of fluid from one tube to the other. Such large transfer causes the interfaces 6 and 6' to be significantly displaced.

The cross-section areas A and B are 100 times that of corresponding cross- sections a or b. The pressures p1 and p2 are considered in reference to the lowest point in the U-tube at which point p = Po. Changes in height delta h are 1/100 the changes in height delta l. Assume the density of the lower fluid is rho' and that of the upper fluid is rho.

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If rho' is 1.00 for water and rho = 0.95 for mixture of carbon tetrachloride and benzene, then delta rho = (1/0.06)(delta p/g), a sensitivity that is approximately 17 times that...