Rotameter float

Area, m or ft Af, projected area of rotameter float Ap, cross-sectional area of channels at periphery of pump impeller Coefficient in Eq. (8.51)... 

Diameter, m or ft D, of pipe of venturi throat Dj-, of rotameter float Dg, of orifice D, of rotameter tube Drag force, N or lb ... 

Mass, kg or lb ttiy, of rotameter float Mass flow rate, kg/s or Ib/s... 

The quantity on the right side of this equation must be evaluated for the test fluid and the calibration fluid. This ratio (i.e., test fluid/calibration fluid) represents the calibration factor, which one must multiply by the mass flow rate of the calibration fluid at a given rotameter float height to obtain the mass flow rate of the test fluid when the float is in the same position. 

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. 

Rotameters The rotameter, an example of which is shown in Fig. 10-21, has become one of the most popular flowmeters in the chemical-process industries. It consists essentially of a plummet, or float, which is free to move up or down in a vertical, slightly tapered tube having its small end down. The fluid enters the lower end of the tube and causes the float to rise until the annular area between the float and the wall of the tube is such that the pressure drop across this constriction is just sufficient to support the float. Typically, the tapered tube is of glass and carries etched upon it a nearly linear scale on which the position of the float may be visually noted as an indication of the flow. 

A typical meter of this kind, which is commonly known as a rotameter (Figure 6.21). consists of a tapered tube with the smallest diameter at the bottom. The tube contains a freely moving float which rests on a stop at the base of the tube. When the fluid is flowing the float rises until its weight is balanced by the upthrust of the fluid, its position then indicating the rate of flow. The pressure difference across the float is equal to its weight divided by its maximum cross-sectional area in a horizontal plane. The area for flow is the annulus formed between the float and the wall of the tube. 

This meter may thus be considered as an orifice meter with a variable aperture, and the formulae already derived are therefore applicable with only minor changes. Both in the orifice-type meter and in the rotameter the pressure drop arises from the conversion of pressure energy to kinetic energy and from frictional losses which are accounted for in the coefficient of discharge. The pressure difference over the float —AP. is given by ... 

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. 

According to Baird and Cheema [Can. J. Chem. Eng., 47, 226—232 (1969)], the presence of square-wave pulsations can cause a rotameter to overread by as much as 100 percent. The higher the pulsation frequency, the less the float oscillation, although the error can still be appreciable even when the frequency is high enough so that the float is virtually stationary. Use of a damping chamber between the pulsation source and the rotameter will reduce the error. 

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. 

Rotameter A flowmeter, consisting of a precision bored, tapered, transparent tube with a solid float inside. 

A less desirable device for measuring flowrates is the rotameter. A float is placed in a tube which is slightly widened at the top to form a cone. The gas flow produces a dynamic pressure keeping the float, which is free to move in the gas stream, at a... 

Two supposedly identical Brook s-model R-2-65-5 rotameters with 316 stainless-steel spherical floats were calibrated for helium service at 20 psig input, 74 °F. Let Y mlHe/min. =flow rate and X mm=scale reading. The data are below ... 

The rotameter, illustrated in Figure 6, is an area flow meter so named because a rotating float is the indicating element. 

Pumps, such as piston pumps, can meter liquids into a reactor fairly precisely, but the chemical engineer uses a flow measurement device for greater precision. The most commonly used flowmeters are rotameters that are calibrated to translate the lifting of a float in a vertical slightly tapered tube (small diameter at the inlet of the flowmeter) into a measure of the amount of liquid delivered in a given timeframe. For greatest precision the rotameter is calibrated with the specific fluid being metered. Most modem rotameters are provided with a calibration plot that corresponds to performance. 

Foam films are usually used as a model in the study of various physicochemical processes, such as thinning, expansion and contraction of films, formation of black spots, film rupture, molecular interactions in films. Thus, it is possible to model not only the properties of a foam but also the processes undergoing in it. These studies allow to clarify the mechanism of these processes and to derive quantitative dependences for foams, O/W type emulsions and foamed emulsions, which in fact are closely related by properties to foams. Furthermore, a number of theoretical and practical problems of colloid chemistry, molecular physics, biophysics and biochemistry can also be solved. Several physico-technical parameters, such as pressure drop, volumetric flow rate (foam rotameter) and rate of gas diffusion through the film, are based on the measurement of some of the foam film parameters. For instance, Dewar [1] has used foam films in acoustic measurements. The study of the shape and tension of foam bubble films, in particular of bubbles floating at a liquid surface, provides information that is used in designing pneumatic constructions [2], Given bellow are the most important foam properties that determine their practical application. The processes of foam flotation of suspensions, ion flotation, foam accumulation and foam separation of soluble surfactants as well as the treatment of waste waters polluted by various substances (soluble and insoluble), are based on the difference in the compositions of the initial foaming solution and the liquid phase in the foam. Due ro this difference it is possible to accelerate some reactions (foam catalysis) and to shift the chemical equilibrium of some reactions in the foam. The low heat... 

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