Pressure Terminology

For design purposes it is necessary to use absolute pressures. In plant operation pressures are often used as vacuum. It is important to eliminate confusion before making a proper performance analysis. See Tables 6-4 and 6-5. 

If pressure is expressed as inches of mercury vacuum, the reading of the local barometer (or a reference barometer) is necessary to establish the absolute suction pressure, or pressure in the vacuum system. 

Applied Process Design for Chemical and Petrochemical Plants 

One kilogram/sq centimeter One kilogram/sq centimeter One kilogram/sq centimeter 

400 microns (micrometers) 0.03937 inch 1,000 microns 0.001 millimeter 0.00003937 inch 28.96 inches 14.22 psi abs 1 735.6 millimeter 

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Pressure/vacuum, 435, 466 Vacuum systems, 343 Absolute pressure conversions, 363 Air inleakage, 366 Calculations, 366-375 Dissolved gases release, 368 Estimated air inleakage, table, 366 Evacuation time, 371 Maximum air leakage, chart, 367 Specific air inleakage rates, 368 Temperature approach, 375 Classifications, 343 Diagrams, 380 Pressure drop, 353 Pressure levels, 343, 352 Pressure terminology, 348 Pump down example, 381 Pump down time, 380 Thermal efficiency, 384 Valve codes, 26... 

Figure 1.12 Pressure terminology. The standard atmosphere is shown by the heavy horizontal line. The dashed line illustrates the atmospheric (barometric) pressure, which changes from time to time. Point Q in the figure is a pressure of 19.3 psi referred to a complete vacuum or 5 psi referred to the barometric pressure (2) is the complete vacuum, O represents the standard atmosphere, and 0 illustrates a negative relative pressure or a pressure less than atmospheric. This type of measurement is described in the text as a vacuum type of measurement. Point (D also indicates a vacuum measurement, but one that is equivalent to an absolute pressure above the standard atmosphere.

Full advantage of the neutron production by plutonium requires a fast reactor, in which neutrons remain at high energy. Cooling is provided by a hquid metal such as molten sodium or NaK, an alloy of sodium and potassium. The need for pressurization is avoided, but special care is required to prevent leaks that might result in a fire. A commonly used terminology is Hquid-metal fast-breeder reactor (LMFBR). 

The pressure difference between the high and low pressure sides of the membrane is denoted as AP the osmotic pressure difference across the membrane is defined as Att the net driving force for water transport across the membrane is AP — (tAtt, where O is the Staverman reflection coefficient and a = 1 means 100% solute rejection. The standardized terminology recommended for use to describe pressure-driven membrane processes, including that for reverse osmosis, has been reviewed (24). 

In pump terminology, the approximate energy in an imploding cavitation bubble is 358,209 ft. To convert this energy into pressure ... 

There s a language barrier between the pump manufacturers and the pump users. They use different terminology. Pump users, the operators and mechanics, use pressure gauges that read in psi, pounds per square... 

When a mixture is saturated, the proper terminology is that the volume occupied by the mixture is saturated by one or more of the components, For air space, which is partially saturated by water vapor, the actual partial pressure of the water vapor may be determined by multiplying the saturation pressure at the space temperature by the relative humidity. 

Filtration. .. Section, Title. 1. Terminology. 2. Filtration Models.2.1. Cake Filtration Calculation of the Pressure Drop.. .. http.7/www.wiley-vch.de/contents/ullmann/ull 10295.html [More Results From www.wiley-vch.de]... 

This chapter describes the basic principles and procedures for the evaluation of overpressure potential in plant equipment, and for the selection, design and specification of appropriate pressure relieving facilities. The design of closed safety valves and flare headers is included in this chapter, but blowdown drums and flares are covered separately. To properly discuss this subject, the reader should become familiar with the following terminology. 

Referring to the terminology in Fig. 5.9 and using analysis similar to that for the coni-cylindrical die, it may be shown that the shear, extensional and die entry pressure losses are given by... 

Terminolog of Pressure Relief Devices, /American National Standards Institute (ANSI) No. B95, 1 (latest ed.). 

Terminology involves drier outlet dew point at the line pressure or the pneumatic circuit. This is the saturation temperature of the remaining moisture contained in the compressed air or gas. If the compressed gas temperature is never reduced below the outlet dew point beyond the drying equipment, there will be no further condensation. 

An interesting and practically valuable result was obtained in [21] for PE + N2 melts, and in [43] for PS + N2 melts. The authors classified upper critical volumetric flow rate and pressure with reference to channel dimensions x Pfrerim y Qf"im-Depending on volume gas content

channel entrance (pressure of 1 stm., experimental temperature), x and y fall, in accordance with Eq. (24), to tp 0.85. At cp 0.80, in a very narrow interval of gas concentrations, x and y fall by several orders. The area of bubble flow is removed entirely. It appears that at this concentration of free gas, a phase reversal takes place as the polymer melt ceases to be a continuous phase (fails to form a continuous cluster , in flow theory terminology). The theoretical value of the critical concentration at which the continuous cluster is formed equals 16 vol. % (cf., for instance, Table 9.1 in [79] and [80]). An important practical conclusion ensues it is impossible to obtain extrudate with over 80 % of cells without special techniques. In other words, technology should be based on a volume con-... 

In the previous sections, we have seen how computer simulations have contributed to our understanding of the microscopic structure of liquid crystals. By applying periodic boundary conditions preferably at constant pressure, a bulk fluid can be simulated free from any surface interactions. However, the surface properties of liquid crystals are significant in technological applications such as electro-optic displays. Liquid crystals also show a number of interesting features at surfaces which are not seen in the bulk phase and are of fundamental interest. In this final section, we describe recent simulations designed to study the interfacial properties of liquid crystals at various types of interface. First, however, it is appropriate to introduce some necessary terminology. 

The terminology of L-B films originates from the names of two scientists who invented the technique of film preparation, which transfers the monolayer or multilayers from the water-air interface onto a solid substrate. The key of the L-B technique is to use the amphiphih molecule insoluble in water, with one end hydrophilic and the other hydrophobic. When a drop of a dilute solution containing the amphiphilic molecules is spread on the water-air interface, the hydrophilic end of the amphiphile is preferentially immersed in the water and the hydrophobic end remains in the air. After the evaporation of solvent, the solution leaves a monolayer of amphiphilic molecules in the form of two-dimensional gas due to relatively large spacing between the molecules (see Fig. 15 (a)). At this stage, a barrier moves and compresses the molecules on the water-air interface, and as a result the intermolecular distance decreases and the surface pressure increases. As the compression from the barrier proceeds, two successive phase transitions of the monolayer can be observed. First a transition from the gas" to the liquid state. 

We need to exercise a little caution with our terminology we performed the calculation in Worked Example 5.1 with Equation (5.1) as written, but we should have written Ap rather than dp because 106 Pa is a very large change in pressure. 

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