Fluid venting flow rates

Morris et al.[6] have proposed a graphical method for estimating vent flow rate for high viscosity flashing fluids The method is semi-empirical and is fitted to experimental data for fluids with viscosities up to 750 cP. 

Constant Flow into Protected Equipment For the steady-state design scenario with a constant, steady flow of fluid from a pressure source that is above the maximum aUowed pressure in the protected equipment, volume is being generated within the equipment at a rate RV = F/ f. Substituting into Eq. (26-21) and noting that the specific volume of the vent stream is l/p, gives the required mass flow rate ... 

Gas pressurized Monitor tank level and provide interlock for feed feed shut-off overpressurizes, alternate fluid delivery system (e.g., pump) centrifuge system when feed vessel delivery gas pressure to maximum safe empties working pressure of downstream system (e.g., pressure regulation) Restrict feed flow rate to be consistent with vent capacity Ensure adequate vent capacity for maximum possible gas flow ... 

Bell, S D Morris R Oster, "Vent Line Void Fractions And Mass Flow Rates During Top Venting Of High Viscosity Fluids , J Loss Prev Process Ind, Vol 6, No1,31-35,1993... 

Dynamic factors are among the key variables to be optimized in an SFE process. In addition to extracting the analytes, the primary function of the supercritical fluid is to transport the solutes to the collecting vessel or to an on-line coupled chromatograph or detector. Ensuring efficient transportation of the analytes following separation from the matrix entails optimizing three mutually related variables, namely the flow-rate of the supercritical fluid, the characteristics of the extraction cell and the extraction time. These factors must be carefully combined in order to allow the flow-cell to be vented as many times as required. 

At high temperatures, RTFs break down into low-boiling compounds. Vapor of these compounds needs to be vented from time to time to prevent pump cavitation, reduced fluid flow rate, lower fluid flash point, and reduction in safety because of continuously increasing pressure. 

Tests are conducted to determine capacity, heat transfer rates, steam economy, product losses, and cleaning cycles. Practically all the criteria of evaporator performance are obtained from differences between test measurements. Errors can result when measuring flow rates, temperatures and pressures, concentrations, and steam quality. Factors which can have a great effect on performance include dilution, vent losses, heat losses, and physical properties of fluids. 

A sudden release of pressure in a container of liquified gas or a liquid that is at a temperature above the atmospheric-pressure boiling point can result in a rapid conversion of some of the liquid to vapor, with a consequent swelling of the now two-phase fluid. Since this fluid is not totally gas or liquid, the equations that are used to calculate flow rates for these phases do not apply. Similarly, venting of a liquified gas or a liquid at a temperature above the atmospheric-pressure boiling point... 

A schematic view of an analog or jet interaction amplifier is shown in Fig. 2a. The device consists of a supply nozzle, two inlet (control) ports, two outlet ports, and two vents. This device is geometrically symmetric about its vertical axis. A uniform jet is supplied to the amplifier via the supply nozzle. Depending on the flow rates at the control channels, there can be three types of scenario at the output channels. First, if there is no flow through the control inlet(s), the fluid jet... 

The SFE instrument consists of a solvent supply, a pump to maintain the pressure and the flow rate, an extraction cell mounted in a heated oven in order to maintain the temperature at the specified value, a restrictor connected to the outlet of the cell, and a collection device. There are different ways of collecting analytes as discussed in the section Collection Devices . In a representative experiment, the cell has a volume of 10ml and is loaded with 1-5 g of sample matrix. Carbon dioxide is pumped at a rate of 0.5-4 ml min measured as liquid at the pump. The pressure is 150-450 bar and the temperature 40-150°C, with a dynamic extraction time of 10-60 min. The extracting fluid is transported through a restrictor. At the restrictor, the pressure of the extracting fluid drops as the extraction fluid expands, releasing the extracted compounds. The gaseous extraction fluid is vented and the analytes are collected in a small volume of solvent (5-20 ml) or onto a solid-phase trap (commonly octadecyl-silica), which is rinsed with solvent in a subsequent step. The extract is often ready for direct analysis. An internal standard is added to the vial to correct for differences in final extract volumes. 

Rotameters have a glass tube with a flow element trapped between the measurement grid. This type of device provides direct contact between the measurement element and the fluid. Flow typically enters at the bottom of the rotameter and lifts the flow element. Oval gear meters and turbine flow meters displace a specific amount of liquid on each rotation. This is used to calculate total flow rate through the system. Pitot tubes are positioned perpendicular to flow. As the liquid enters the tube, precision-machined sensing vents determine flow rate. 

Figure C.2. Photograph of the supercritical fluid system used for nanoparticle synthesis. Shown is the 300-mL high-pressure reactor (A), with pressure/temperature controllers (B). The system is rated for safe operation at temperatures and pressures below 200°C and 10,000psi, respectively. The vessel may be slowly vented, or exposed to a dynamic CO2 flow, using a multiturn restrictor valve (C), which provides a sensitive control over system depressurization, allowing for the collection of C02-solvated species in the stainless steel collector (D). For deposition using the rapid expansion of tlie supercritical solution (RESS), nanoparticles were blown onto a TEM grid that was placed under the stopcock below D. Also shown is the cosolvent addition pump (E) used for the synthesis of aluminum oxide nanoparticles, capable of delivering liquids into the chamber against a back-pressure of <5,000 psi.

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