Flow-measuring equipment, types

In the process industries, flow measurement devices are the largest market in the process instrumentation field. Two web sites for process equipment and instrumentation, www.globalspec.com, and www.thomasnet.com, both list more than 800 companies that offer flow measurement products. There are more than one hundred types of flowmeters commercially available. The aforementioned web sites not only facilitate selection and specification of commercial flowmeters, but also provide electronic access to manufacturers technical literature. 

Anxiety concerning the measurement of flow of liquefied gases possibly stems from the knowledge that such liquids can be near their saturation temperatures and that two-phase flow may occur. The apprehension is that local pressure depressions may cause vaporization and thus yield an erroneous flow measurement. Another problem arises because no instrumentation has yet been developed which will give the necessary density information. These difficulties, which are common to all fluids near saturated conditions using volumetric flow meters, can be eliminated by the use of mass flow meters some instrumentation of this type is available, but is very expensive. There is no justification, however, for using very complicated equipment... 

Extensional Viscosity. AH three types of extensional viscosity can be measured (101,103) uniaxial, biaxial, and pure shear. Only a few commercial instmments are available, however, and most measurements are made with improvised equipment. Extensional viscosity of polymer melts can be estimated from converging flow (entrance pressure) or from a melt strength drawdown test (208). 

Figure 23.18. Dependence of the extent of flow on temperature for a general purpose phenolic resin. Curves of this type may be obtained from measurements made on widely different pieces of equipment, e.g. the Rossi-Peakes flow tester and the flow disc. Thus no scale has been given for the...

Except for the case of an ideal plug flow reactor, different fluid elements will take different lengths of time to flow through a chemical reactor. In order to be able to predict the behavior of a given piece of equipment as a chemical reactor, one must be able to determine how long different fluid elements remain in the reactor. One does this by measuring the response of the effluent stream to changes in the concentration of inert species in the feed stream—the so-called stimulus-response technique. In this section we will discuss the analytical form in which the distribution of residence times is cast, derive relationships of this type for various reactor models, and illustrate how experimental data are treated in order to determine the distribution function. 

Tubular flow units, like the CSTR, usually are operated at steady state. It is not always easy to measure the temperature profile accurately. In some high temperature operations, the coil is immersed in a fluidized sand bed or lead bath so there is fairly good temperature control. Sometimes it is felt desirable to do the laboratory work in a tubular unit if the commercial unit is to be of that type, but rate data from any kind of equipment are adaptable to the design of PFR. 

The TO 6 type got two separate gas jet pumps, one for each measuring range and an el. magn valve. A range selector does the same as the flow selector of the modified TO 4 type. The second stream is lead to an additional sniffing port which can be used by the panel leader. A port selector brings the main stream to one of four sniffing ports (masks), installed in four separate boxes. This equipment has been set up in a caravan. To set it vertical it is mounted to a ball and socket. Four panelists can take place in front of their masks A sample bag can directly be connected to the olfactometer. The delay between... 

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