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Instrumentation and Measurement
Published in Dale R. Patrick, Stephen W. Fardo, Ray E. Richardson, Brian W. Fardo, Energy Conservation Guidebook, 2020
Dale R. Patrick, Stephen W. Fardo, Ray E. Richardson, Brian W. Fardo
When a positive pressure is directed into one leg of the U-tube it forces the liquid down in that leg and up in the other leg. The resulting difference in the height of the two liquid columns indicates the pressure. An indication of pressure would be in inches of water or inches of mercury. This could be read directly on a scale positioned in the center of the U-tube. Manometer scales are based upon the pressure required to move the rill liquid. One inch of mercury (Hg) is equal to 0.492 pounds per square inch (psi). Water, being much lighter in weight than mercury, produces a greater change in column height. One inch of water is equivalent to 0.036 psi of pressure or 1 psi = 2.31 ft of water. A convenient flexible-tube manometer and a portable rollup type of manometer are shown in Figure 10-23.
Measurement fundamentals and instrumentation
Published in Raymond F. Gardner, Introduction to Plant Automation and Controls, 2020
Fluid pressure—usually air—is applied against a liquid in a U-tube as shown in Figure 1.4. The pressure forces the liquid to rise in the U-tube until the liquid weight balances the pressure force. The measurement is the height of the liquid in the manometer. For small pressure measurements, such as fan-discharge pressures, water is often used, and the pressure is given in inches of water column. For larger pressures or vacuum, mercury is used, and the units are given in inches of mercury. Standard atmospheric pressure is slightly less than 30 inches of mercury. To increase the sensitivity, manometers are often inclined at an angle. To convert height of liquid to psip=γ⋅h(whereγisweightdensity)Find: How high in feet of water column is one psi?1lbfin2=62.41bft3⋅ft2144in2⋅hSolving:h=2.31ft
Analysis of Fluid Flow and Heat Transfer in Corrugated Porous Fin Heat Sinks
Published in Heat Transfer Engineering, 2021
Shripad A. Upalkar, Sanjeet Kumar, Shankar Krishnan
The cross-section of the duct is 50 mm × 45 mm. The size of the melamine foam sample was 50 mm × 50 mm × 6 mm. The conduit has a width of 19.5 mm, whereas the length and height both are 50 mm. This foam sample was fitted in the test chamber of the airflow duct. The melamine foam was kept at the center of the flow duct, and the thin acrylic sheets were attached to it on both ends to form a Z-type arrangement for fluid flow. During the experimentation, the flow rate was varied using a Yaskawa V1000 variable frequency drive in conjunction with a counter-blower. The flow rate was varied from 0.0011 m3/s to 0.0041 m3/s. As the least count of the U-tube manometer is 1 mm, the uncertainty in measuring pressure drop is ±5 N/m2. The pressure drop across the array of nozzles in the flow chamber, which is used to calculate flow rate (and in turn, the flow velocity), is measured using an inclined manometer whose least count was 0.01 inch and corresponding uncertainty in pressure drop measurement is ±1.25 N/m2 (0.01 inch of water ≈ 2.5 N/m2).