Standard volumetric flow rate

On a molar basis the compression work does not change very much for the various mixtures ranging from a low of 1927.7 J/mol to 1945.2 J/mol - the difference being less than 1%. Expressing the work on a molar basis is significant because the molar flow rate is proportional to the standard volumetric flow rate. Thus to compress 1 Sm3 of each of these mixtures requires approximately the same amount of work. This is true even though the exit temperatures is different for the various mixtures. 

Note that to calculate the molar flow rate from a standard volumetric flow rate, you don t need to know the actual gas temperature and pressure. 

All of the calibration gas generators for laboratory use work dynamically, ie, according to the dosing principle. The desired gases are dosed with definite flow rates and then mixed inside the apparatus. With the technical equipment available in laboratories, standard volumetric flow rates (V,) or molar flow rates (F) can be proportioned much more precisely than concentrations or absolute quantities (gas suppliers, however, often manufacture gas mixtures by a weighing-in process). Calibration gas generators are offered on the basis of three different methods of gas dosage (to be described in detail later). 

F, + Fj). The molar flow rate F and the standard volumetric flow rate V, are equivalent quantities that can be converted by using the standard molar volume Vg as conversion factor. 

The smallest possible standard volumetric flow rate is in the range of 0.1 to 1 standard cubic centimeter per minute (SCCM). In the following example, a total standard volumetric flow rate (that in close approximation is equivalent to the carrier gas standard volumetric flow rate K.carrier) about 1000 SCCM results in a minimal possible concentration of 10 or a dilution ratio of 1 10000. 

The concentration pulses can be smoothened out in remixing devices. To do this, a vessel with a residence characteristic of a perfectly mixed flow vessel and a medium residence time of five to ten times the dosing interval is necessary. In the case of a total standard volumetric flow rate of 2 SLM and a pulsing interval of one minute, one needs a device that can hold approximately 10-20 L, which conforms to a delay in the system response of 5-10 min. 

A disadvantage of the nozzle method is that the nozzles are not variable in their cross-sectional area, that is, the concentrations and total flow rate are fixed and cannot be varied continuously. The built-in nozzles are chosen and fixed at the time of conception of the system. To enable the flow rate to vary, precise, reproducibly steerable pressure regulators for the inlet pressure would be necessary, which is not economically feasible. Orifices can be manufactured with various cross-sectional areas, but there is a technical lower limit, so that the minimum standard volumetric flow rate achievable lies at approximately 1 SCCM. 

The lowest possible concentration range is a critical point in dosing pump/vaporizer solutions. The presently available pumps, in the lowest range, transport approximately 10 10 — 100 10 CCM, which, after vaporization, correlates to a gas standard volumetric flow rate of 10-100 SCCM. The lowest mole fraction range is ll o at a total standard volumetric flow rate of 1 SLM (a typical value for gas analysis equipment). 

In the case of a carrier gas standard volumetric flow rate of about S SLM, a maximal dilution ratio of 1 5000 can be achieved. The surplus precursory calibration gas is emitted as exhaust. 

For calculation of the volumetric flow rate only the cross section area of the pipe is to be known. In order to give flow under standard conditions the temperature and pressure must be measured, and for conversion to mass flow the composition or density of the gas must be determined. These process parameters are often monitored by calibrated instrumentation. 

As with dust cyclones, no reliable pressure-drop equations exist (see Sec. 17), although many have been published. A part of the problem is that there is no standard cyclone geometry. Calvert (R-12) experimentally obtained AP = 0.000513 J Q /hiWi) 2.8hiWi/dl), where AP is in cm of water Pg is the gas density, g/cm is the gas volumetric flow rate, cmVs hj and Wj are cyclone inlet height and width respectively, cm and is the gas outlet diameter, cm. This equation is in the same form as that proposed by Shepherd and Lapple [Ind. Eng. Chem, 31, 1246 (1940)] but gives only 37 percent as much pressure drop. 

CFR Part 60 (Appendix A) New source performance standards Methods 1-4 Test location, volumetric flow rate, gas composition, moisture content... 

Compressors are rated as to their maximum volumetric flowrate they can operate at, and the maximum pressure they can maintain. These ratings are usually specified as standard cubic feet per minute (scfm) and psig. The scfm of volumetric flow rate refers to the compressor intake. The pressure rating refers to the output pressure capability. 

Q Volumetric flow rate in standard conditions (m3/min) r Radial distance from SVE well (m)... 

Since the density of a gas is strongly dependent on the temperature and pressure, knowing only the volumetric flow rate is not adequate. For this reason the flow is given above as so many standard cubic feet per minute (scfm). This is the volume of fluid that would be transferred at a temperature of 60°F (15.6°C) and a pressure of 14.7 psia(1.033 kg/cm2). For design purposes, this rate is usually increased by 5%.27... 

If the gas behaves ideally the volumetric flow rate at the reactor inlet is given by the product of the molal flow rate [(500/146) lb moles/hr] and the molal volume at the pressure and temperature in question. The latter may be calculated by correcting the standard molal volume (359 ft3/lb mole) for variations in temperature and pressure between the reactor inlet and standard conditions. Hence... 

Other complications are that the reactor feed may be preheated and the feed pressure may vary, and thus the volumetric flow rate of gases will be functions of the reactor temperature and pressure at fixed mass flow rate. Therefore, the space velocity of gases is frequently defined at standard conditions T = 25°C and P = 1 atm. 

Volumetric flow rates of different gases are often compared to equivalent volumes of air at standard atmospheric temperature and pressure. The ideal gas law works well when used to size fans or compressors. Unfortunately, the gas law relationship, PV/T = constant, is frequently applied to choked gas streams flowing at sonic velocity. A typical misapplication could then be the conversion to standard cubic feet per minute in sizing SRVs. Whether the flow is sonic or subsonic depends mainly on the backpressure on the SRV outlet. In the API calculations, this is taken into account by the backpressure correction factor. 

The heat flow rate (Q) of a gaseous fuel is calculated as the product of its volumetric flow rate at standard conditions (V0) and its calorific value (CV). The Wobbe index (WI) measures the ratio between the net CV and the square root of specific gravity (SG). With orifice-type flow sensors, the advantage of detecting the WI is that it eliminates the need to separately measure the specific gravity this is because the product of the WI and orifice pressure drop results in a constant times the heat flow rate (KxQ), without requiring a separate measurement of SG. 

Determine the actual volumetric flow rate. Use Charles law to convert from qs, the flow rate at the standard-conditions temperature Ts, to qa, the flow rate at the actual temperature Ta ... 

It is proposed to install a pulse-jet fabric-filter system to remove particulates from an air stream. Select the most appropriate bag from the four proposed below. The volumetric flow rate of the air stream is 10,000 std ft3/min (4.72 m3/s) (standard conditions being 60°F and 1 atm), the operating temperature is 250°F (394 K), the concentration of pollutants is 4 grains/ft3 (141 grains/m3), the average air-to-cloth ratio is (2.5 ft3/min)/ft2, and the required collection efficiency is 99 percent. 

Determine the volumetric flow rate of the combustion products of the natural gas. This flow rate q equals the natural gas rate times the volume of combustion products produced per standard cubic foot of natural gas. Thus,... 

The reader is cautioned to note carefully that the volumetric flow rate at standard conditions is, in general, different from those at actual conditions. In the above equations the flow must be at actual conditions. 

The equations for sizing rotary-drum filters are summarized in Table 6.18. Equation 6.18.1 is the liquid mass balance. In this procedure, y is a mass fraction. Because the cake is wet, the liquid entering the filter will be less then the liquid leaving. Equation 6.18.2 is the solids mass balance, assuming that all the solids in the slurry are removed. Solve Equation 6.18.2 for the cake formation rate, me. Then, solve Equation 6.18.1 for the filtrate volumetric flow rate, V2. Next, calculate the filtration area from Equation 6.18.5 and the dmm area from Equation 7.18.6. Finally, select a standard rotary filter from Table 6.20. The calculation procedure for sizing a rotary filter is outlined in Table 6.19. Example 6.5 illustrates the sizing procedure. 

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. 

Explain the meaning of 37.5 SCFH (37.5 standard cubic feet per hour) and what it means to say that the flow rate of a gas stream at 120°F and 2.8 atm is 37.5 SCFH. (Why doesn t this statement specify the impossible condition that the gas is at two sets of temperatures and pressures simultaneously ) Calculate the true volumetric flow rate of that gas. 

The term standard cubic meters (or SCM) is often used to denote m (STP), and standard cubic feet (or SCF) denotes ft (STP). A volumetric flow rate of 18.2 SCMH means 18.2 m /h at 0°C and 1 atm. 

Butane (C4H10) at 360°C and 3.00 atm absolute flows into a reactor at a rate of 1100 kg/h. Calculate the volumetric flow rate of this stream using conversion from standard conditions. 

The answer is that it can t—the gas is nor at standard temperature and pressure. A flow rate specified in the given manner (23.8 SCMH) is not the true volumetric flow rate of the stream at its actual temperature and pressure (150 C and 2.5 atm) but the flow rate that would be obtained if the stream were brought from its actual conditions to standard temperature... 

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