Rotameters volumetric flow-rates

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. 

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... 

To size a rotameter requires calculating the volumetric flow rate of a standard fluid at standard conditions. Most manufacturers calibrate rotameters using a stainless-steel float and water at a standard tenperature for liquids and air at a standard tenperature and pressure for gases. For other fluids, float materials, and operating conditions, the flow rate must be converted to an equivalent flow rate of water or air. To derive a formula for making this conversion, Bernoulli s equation is applied across the float shown in Figure 8.15 to give Equation 8.9. 

To select a rotameter from Table 8.3 first calculate an equivalent flow rate of water from Equation 8.26. In Table 8.3 stainless steel floats are used. The density of stainless steel is 8.02 g/cc (501 Ib/ft ) and the density of carbon tetrachloride is 1.60 g/cc (99.9 Ib/ft ). After substituting numerical values into Equation 8.26, the volumetric flow rate of water. 

Sulfur dioxide is contained in the feed and effluent streams of a chemical reactor, but it is neither a reactant nor a product. The volumetric flow rates of both streams (L/min) are measured with rotameters, and the concentrations of SO2 in both streams (mol/L) are determined with a gas chromatograph. The molar flow rate of SO2 in the reactor effluent (determined as the product of volumetric flow rate and concentration) is 20% lower than the molar flow rate of SO2 in the feed. Think of as many possible explanations for the discrepancy as you can. 

A condenser is then installed and run at the design temperature and pressure. The volumetric flow rates of the feed stream and the vapor and liquid product streams are measured with rotameters (see p. 46), and the MEK mole fractions in the feed and vapor effluent streams are measured with a gas chromatograph. The feed stream flow rate is set to 500 liters/s and enough time is allowed to pass for the product stream rotameter readings to reach steady levels. The feed and product gas flow rates are then converted to molar flow rates using the ideal gas equation of state, and the product liquid flow rate is converted to a molar flow rate using a tabulated MEK density and the molecular weight of MEK. Here are the results. 

The three previously discussed devices use a fixed geometry and read a pressure difference which is proportional to the square root of the volumetric flow rate, A rotameter uses a fixed pressure difference and a variable geometry, which is a simple function of the flow rate. Figure 5.13 shows a schematic view of a simple rotameter. It consists of a tapered transparent (glass or plastic) tube, in which the fluid whose flow is to be measured flows upward, and an interior float, which is shown in Fig. 5.13 as a spherical ball. 

Example 5.10. Our rotameter has been calibrated for nitrogen at room temperature and atmospheric pressure the calibration shows that for a reading (float position) of 50 percent of the height of the rotameter tube, the volumetric flow rate is 100 cm /min. We now need to measure the flow of... 

A rotameter is used to measure the flow rate of air at 25 °C and 1 bara. A 2 mm sapphire bead rises to a point in which the tube diameter is equal to 6 mm. Calculate the mass flow rate and the volumetric flow rate if the drag coefficient equals 0.1. M. Lessard... 

A rotameter measures the flow of nitrogen at a temperature of 800.5 °F and a pressure of 58.01 psig. The volumetric flow rate equals 5 m min" when the carbon steel ball is at full scale ... 

To size the rotameter, v nsx can be eliminated between these two equations and the expression simplifled so that the volumetric flow rate q is obtained as Eq. (24), where Q = l/ /C is a discharge coefficient with values between about 0.6 and 0.8 [9]. 

Both gas flow rates and liquid flow rates can be measured by a wide variety of devices such as bellow meters, Venturi nozzles, nutating disk meters, orifice meters, rotameters, weirs (for liquids), Pitot tubes, and magnetic meters among others. Some devices measure volumetric flow directly as with meters in which the space between rotating paddles incorporates small volumetric displacements of fluid. Other device measure the flows indirectly by measuring the pressure drop caused by an orifice between two different sites in the pipe, or the change in voltage of a heated wire. 

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