Constant flow rates

An empirical observation is if one forms drops at a constant flow rate such that... 

Titrations may be automated using a pump to deliver the titrant at a constant flow rate, and a solenoid valve to control the flow (Figure 9.5). The volume of titrant delivered is determined by multiplying the flow rate by the elapsed time. Automated titrations offer the additional advantage of using a microcomputer for data storage and analysis. 

A nonproportional sampler is suitable for near-constant flow conditions. The sample is simply drawn from the waste stream at a constant flow rate. Sampling lines should be as short as possible and free from sharp bends, which can lead to particle deposition. Proportional samplers are designed to collect either definite volumes at irregular time intervals or variable volumes at equal time intervals. Both types depend on flow rate. Examples of some of these are the vacuum and chain-driven wastewater samplers. Other types, which have cups mounted on motor driven wheels, vacuum suction samplers, and peristaltic pump samplers, are also available (26,27). 

When collecting meaningful field fractionating column data, the column must not only have constant flow rates, but the flows must give a good material balance (no accumulation). In addition, a steady state condition must exist for the given flow rates. 

Now, as shown in previous example, for a constant flow rate situation the pressure build-up in the machine is given by... 

Fuller claims that an auxiliary cupboard has better performance than an ordinary cupboard, if properly designed and used. The auxiliary flow rate should be 50% to 75% of the total exhaust flow from the cupboard. Below 50% there is no beneficial effect and above 75% the auxiliary air will aspirate contaminants out of the cupboard. The auxiliary air should enter the hood through the upper one-half to two-thirds of the opening. This should fill the volume between the cupboard operator and the opening and assist in the containment. The auxiliary air should be distributed uniformly across the length of the cupboard for a vertically sliding sash or above only the open sash of a cupboard with a horizontally sliding sash. It should also have a temperature within 1.5 °C of the room temperature and have a constant flow rate without pulsations. 

Mechanical constant flow rare Self-actLiacing and deriving ics energy from the airstream to maintain the constant flow rate function. 

Pneumatic or electric Deriving the energy for maintaining the constant flow rate function from an external source. It can be either of the constant or variable type. 

System-powered Deriving its energy from the dynamic pressure in the air-stream to maintain its constant flow rate function and can be either a constant or variable type. 

Mechanical constant flow rate controller See Flow rate controller. 

The number of cross baffles is large (more than 4). Constant flow rate and specific. 

Wv = Pounds water vapor per pound air w = Constant flow rate, lbs/min wa = Acceptable air leakage rate assigned to a system component, lbs/hr... 

The precipitate that forms during ozonolysis sometimes impedes stirring, and in some cases it may be necessary to dilute the slurry with another 100 ml. of methanol after the first hour. Solid can also clog the gas-dispersion tube. The submitters scraped the fritted-glass tip occasionally to maintain a constant flow rate, whereas the checkers prepared a more dilute solution of nitronate anion (Note 3). 

Constant flow rate of S03 High accuracy in flow controllers... 

Unfortunately, neither the computer nor the potentiometric recorder measures the primary variable, volume of mobile phase, but does measure the secondary variable, time. This places stringent demands on the LC pump as the necessary accurate and proportional relationship between time and volume flow depends on a constant flow rate. Thus, peak area measurements should never be made unless a good quality pump is used to control the mobile phase flow rate. Furthermore, the pump must be a constant flow pump and not a constant pressure pump. 

In HPLC, the mobile phase is a liquid delivered under high pressure (up to 400 bar (4 x 10 Pa)) to ensure a constant flow rate, and thus reproducible chromatography, while the stationary phase is packed into a column capable of withstanding the high pressures which are necessary. 

From a mass spectrometry perspective, the pump must be pulse free, i.e. it must deliver the mobile phase at a constant flow rate. Pulsing of the flow causes the total ion current (TIC) trace (see Chapter 3) - the primary piece of information used for spectral analysis - to show increases in signal intensity when analytes are not being eluted and this makes interpretation more difficult. 

The general case treats time-dependent volumes, flow rates, and inlet concentrations. The general case must be used to for most startup and shutdown transients, but some dynamic behavior can be effectively analyzed with the constant-volume, constant-flow rate version of Equation (14.2) ... 

The reactor operates at constant volume, constant density, constant flow rate, and isothermally. The only difference between the two products is the addition of component C to the feed when Product II is made. 

Fig.Sa-f. The sensorgram of the repeated injection of the aqueous viologen dimer 2 (a, c, e) and the antibody (b, d, f) solutions. [Viologen dimer 2]=2.0 pM and [antibody]=2.0 pM in phosphate borate buffer. Injection period 60 s for a-c and 120 s for d-f. A solution of viologen dimer 2 or the antibody passes over the surface of the sensor chip for 60 or 120 s at a constant flow rate of 20 pL min. The surface of the sensor chip was subsequently washed with buffer...

Flow rate Rate constant Flow rate... 

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