Rotameter, flow rate

Rotameter A rotameter consists of a vertical tube with a tapered bore in which a float changes position with the flow rate through the tube. For a given flow rate the float remains stationary since the vertical forces of differential pressure, gravity, viscosity, and buoyancy are balanced. The float position is the output of the meter and can be made essentially linear with flow rate by makiug the tube areavaiy hn-early with the vertical distance. 

According to Head [Tran.s. Am. Soc. Mech. Eng., 76, 851-862 (1954)], flow rate through a rotameter can be obtained from... 

The ratio of flow rates for two different fluids A aud B at the same rotameter reading is given by... 

Before removing the pump at the end of the sample period, check the flow rate to ensure that the rotameter bail is still at the calibrated mark (if there is a pump rotameter). If the ball is no longer at the mark, record the pump rotameter reading. 

Turn on the pump and adjust the pump rotameter, if available, to the appropriate flow rate setting. 

In practice, deliberate changes in flow are necessary to proportion quantities of flow into various systems, and to determine flow rate by various measuring devices by restrictions, e.g. Venturi meters and rotameters. 

The checkers used acetylene available from Matheson Gas Products. The gas was purified by passing it through concentrated sulfuric acid and then through a tower filled with potassium hydroxide pellets. The gas was then passed into a 1-1. safety flask which was connected to the gas inlet tube by means of rubber tubing. The checkers used a rotameter that was calibrated with air to determine the flow rate of acetylene. 

Rate Meter Measures the instantaneous volume flow rate through the sampling systems. An example would be a rotameter or venturi meter. Used to set precise flow rate for flow sensitive sampling devices. 

Rotameters, velocity flowmeters, and electromagnetic flowmeters have the advantage that they can be used with a linear scale in which the volumetric flow rate Q is directly proportional to the scale reading s. 

The Prosser was calibrated by measuring the air flows using a laminar flow meter (1% accuracy) for the odorous sample and a pitot tube with a micromanometer for the fan-blown air (3). The pitot pressures were converted to air velocities (4) and hence, from the cross sectional area of the tube, to volumetric flow rates. Since flow near the tube wall was slower than the centre, the tube was traversed by the pitot head and the average value calculated. A rotameter was also tried but it induced a back-pressure of 250 N/m2 and, as the manufacturer states that the maximum permissible back-pressure is 60 N/m for calibration to be accurate, its use was not pursued. 

The actual dilution factors were always less than the theoretical ones (Fig. 6) and the deviation with both rotameters was always larger at lower flow rates. The deviation of the... 

These investigations showed that the T04 olfactometer can deliver repeatable dilutions, but that an absolute calibration was needed before use. The main problems arise from the flow rates measured in the lower ranges of the rotameter scales, which are less accurate than the upper ranges. If the upper ranges only are used, then consistent results should be obtainable. The olfactometer should be used in the same orientation as when calibrated. 

Fig. 7 Effect of flow rate in small rotameter on the 10 x pre-dilution factor...

Feser et al. [214] used a radial flow apparatus to determine the viscous in-plane permeability of differenf DLs af various levels of compression (see Figure 4.26). A stack of round-shaped samples, wifh each layer of material separated with a brass shim, was placed inside two plates. Thicker shim stock was also used in order to control the total thickness of the stack of samples. Compressed air entered fhe apparafus fhrough the upper plate and was forced through the samples in the in-plane direction. After this, the air left the system and flowed through a pressure gage and a rotameter in order to measure the pressure drop and the air flow rate. The whole apparatus was compressed using a hydraulic press for each compression pressure, 10 different flow rates were used. 

In the field, a rotameter connected to the crucible holder is used to monitor flow rates each day. We recently Invested in a direct-reading rotameter with a range of 3-21 Lpm, and we anticipate better recognition of flow problems during sampling surveys. 

Variable-Area Meters Variable-area meters, which are also called rotameters, offer popular and inexpensive flow measurement devices. These meters employ a float inside a tube that has an internal cross-sectional area that increases with distance upward in the flow path through the tube. As the flow rate increases, the float rises in the tube to provide a larger area for the flowing fluid to pass. 

Specifications included two 56-gallon FIDPE tanks, a 120 V pump, on/off float switch, rotameter with flow-rate adjustment, two pre-filters, and four filters with refillable Octolig cartridges. Size is 52"x52" with a 68 gallon spill containment. From [28] and reproduced with permission. 

The supercritical carbon dioxide extract stream is passed from the extractor vessel outlet through pressure reduction valve 8, where the pressure is reduced to atmospheric pressure and the extracted organic substance is precipitated in collection device 9. The atmospheric pressure carbon dioxide then flows from the collection device through a rotameter 10 and dry gas meter 11, which measure CO2 flow rate and total volume, respectively, to the vent 12. 

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