Flow measurements static

With the help of ion-selective electrodes and the proper calibration, the ion activity at the indicating electrode position can be monitored directly and continuously. According to Friedman [249], who was the first to carry out continuous blood pNa and pK measurements, one can distinguish between static and dynamic flow measurements. Static measurements are those such as ion activity measurements in the stomach or on the surface of the skin. In vivo flow measurements are primarily ion activity measurements in bloodstreams, either in the flow circuit of a heart-lung machine, or also post-operatively by means of vein shunts. 

Chile [Prog. Aerosp. Sc7, 16, 147-223 (1975)] reviews the use of the pitot tube and allied pressure probes for impact pressure, static pressure, dynamic pressure, flow direction and local velocity, sldn friction, and flow measurements. 

The absolute, barometric pressure is not normally required in ventilation measurements. The air density determination is based on barometric pressure, but other applications are sufficiently rare. On the other hand, the measurement of pressure difference is a frequent requirement, as so many other quantities are based on pressure difference. In mass flow or volume flow measurement using orifice, nozzle, and venturi, the measured quantity is the pressure difference. Also, velocity measurement with the Pitot-static tube is basically a pressure difference measurement. Other applications for pressure difference measurement are the determination of the performance of fans and air and gas supply and e. -haust devices, the measurement of ductwork tightness or building envelope leakage rate, as well as different types of ventilation control applications. 

Example 4-1 Manometer. The pressure difference between two points in a fluid (flowing or static) can be measured by using a manometer. The manometer contains an incompressible liquid (density pm) that is immiscible with the fluid flowing in the pipe (density pf). The legs of the manometer are connected to taps on the pipe where the pressure difference is desired (see Fig. 4-2). By applying Eq. (4-7) to any two points within either one of the fluids within the manometer, we see that... 

Where conditions are such that it is impractical to measure static pressure at the wall, a combined pitot-static tube may be used. This is actually two tubes, one inside the other. The outer tube is plugged off at the end facing the flowing fluid, but small holes are drilled through it to receive the fluid pressure. These holes open into the annular space between the tubes. The static pressure is measured through two or more of these holes, and it is assumed that the flow follows along the outside of the tube in such a way that the true static pressure is obtained. 

The evaluation of the commercial potential of ceramic porous membranes requires improved characterization of the membrane microstructure and a better understanding of the relationship between the microstructural characteristics of the membranes and the mechanisms of separation. To this end, a combination of characterization techniques should be used to obtain the best possible assessment of the pore structure and provide an input for the development of reliable models predicting the optimum conditions for maximum permeability and selectivity. The most established methods of obtaining structural information are based on the interaction of the porous material with fluids, in the static mode (vapor sorption, mercury penetration) or the dynamic mode (fluid flow measurements through the porous membrane). 

Air flow measurement technique at different hood surfaces, volumetric flow rate, transport and capture velocity, hood static pressure, pitot tube, thermal anemometer, and magnehelic gauge. 

There are a number of approaches to the measurement of solubilities in pure and mixed supercritical fluids an excellent review can be found in Bruno and Ely (3). These fall into four major categories dynamic or flow methods, static or equilibrium methods, chromatographic methods, and spectroscopic methods. 

Liquid Flow Measurement. The requirement of accurate liquid flow measurement can also elevate process equipment (see Figure 7-8). If liquid is near the boiling point, a static head is required in the front of the control valve to overcome pipe friction losses and avoid flashing in the line. Minimum equipment elevation, orifice range and minimum line size can be used if the orifice is as close to the equipment as possible and the piping has only one elbow up to the control valve. 

The electronic flow measurement for custody transfer system consists of a microcomputer, s chromatgraph, H20 and H2S analyzer, a differential pressure, static and temperature transducers for each... 

Static pressure is the potential pressure exerted in all directions by a fluid at rest. In a duct, static pressure tends to expand or collapse a pipe, depending on whether static pressure is positive or negative. One measures static pressure in a duct normal to the direction of air flow. 

An unusual application is described by Fedoseeva, Nechaev, and Strel tsova, who measured the adsorption of thirty-five organic substances on snow surfaces. Toluene was used as solvent since it does not dissolve ice to any appreciable extent, and has a lower density than ice. Of the 34 substances studied only formic, monochloracetic, and trichloracetic acids, and methyl and ethyl alcohols were adsorbed. The type II isotherm for trichloracetic add seemed to exhibit a B-point , use of which led to a surface area of the snow sample of 2.8 0.3 m g, which is similar to the value obtained from the low-temperature N2 adsorption. Further work on the use of calorimetry for the determination of surface areas is described by Rahman, who compares flow and static measurements of the heats of adsorption of stearic add from n-heptane by Fc203 and FeS. It is reported that heats of adsorption determined by these two methods differ by a constant factor that depends to some extent on the operating conditions used in the flow calorimetry. Under standardized conditions and using an FcaOa sample as a reference material, it is considered that flow calorimetry using the adsorption of stearic acid from n-heptane is a reliable method of finding the surface area of oxides. 

Methodologies are currently available for measuring airway resistance and compliance in rodents and non-rodents either during spontaneous breathing (dynamic) or using a forced maneuver procedure (flow-volume or pressure-volume curves) that involves a controlled inflation and rapid deflation of the lung to evaluate forced expiratory flows and static or quasi-static compliance. The direct measurement of resistance and compliance t5q)ically requires an anesthetized model so that the airflows, pressures, and volumes can be monitored and controlled (Diamond and O DoimeU 1977 Costa et al. 1992 Mauderly 1989). 

Respirometric methods can be classified into a number of basic measurement principles depending on two criteria (i) The phase where oxygen is measured (gas or liquid) and (ii) the flow regime of bofh gas and liquid phase, which can be either flowing or static [4]. From these criteria the modalities are... 

The frictionless form of the Bernoulli equation is the basis for many fluid-flow measuring devices. These include the pitot tube, the pitot-static tube, the Venturi meter, and the orifice meter (see Figure 2-22). 

---