Volume fixed

Power output is controlled, not by adjusting the quantity of fuel/air mixture as in the case of induced spark ignition engines, but in changing the flow of diesel fuel introduced in a fixed volume of air. The work required to aspirate the air is therefore considerably reduced which contributes still more to improve the efficiency at low loads. 

Wang and Taha described an interesting application of potentiometry called batch injection. As shown in the following figure, an ion-selective electrode is placed in an inverted position in a large-volume tank, and a fixed volume of a sample or standard solution is injected toward the electrode s surface using a micropipet. 

Quantitative Calculations Quantitative analyses are often easier to conduct with HPLC than GC because injections are made with a fixed-volume injection loop instead of a syringe. As a result, variations in the amount of injected sample are minimized, and quantitative measurements can be made using external standards and a normal calibration curve. 

The amount of caffeine in an analgesic tablet was determined by HPLC using a normal calibration curve. Standard solutions of caffeine were prepared and analyzed using a lO-pL fixed-volume injection loop. Results for the standards are summarized in the following table. 

Orifice. Orifice viscometers, also called efflux or cup viscometers, are commonly used to measure and control flow properties in the manufacture, processing, and appHcation of inks, paints, adhesives, and lubricating oils. Their design answered the need for simple, easy-to-operate viscometers in areas where precision and accuracy are not particularly important. In these situations knowledge of a tme viscosity is uimecessary, and the efflux time of a fixed volume of Hquid is a sufficient indication of the fluidity of the material. Examples of orifice viscometers include the Ford, Zahn, and Shell cups used for paints and inks and the Saybolt Universal and Furol instmments used for oils (Table 5). 

Comparisons are available on the relative performance and costs for dewatering municipal sludges (2). The relative performance of different filters and conditioners on waste sludges is shown in Table 3. The same sludge was treated on two belt-filter presses, two different centrifuges, and rotary vacuum filter (75). In another study, a variable chamber filter press, fixed-volume filter press, continuous belt-filter press, and rotary vacuum filter were compared for performance, capacity, and capital and operating costs (69). 

The procedure can be readily extended to multicomponent systems by applying the test to each component in turn. In real systems, it is generally convenient to take samples of fixed volume or mass rather than fixed number of particles. In such cases, the expected variance can be computed using (see Refs. 19 and 20)... 

The regenerator (Figure 4-80) is represented by a simplified model that ineludes the total volume and mass balanee ealeulation. The regenerator exit temperature is assumed eonstant for the duration of the transient. The third-stage separator is handled as a fixed volume and assoeiated pressure drop. Blow-down (bypass) flow is subtraeted from the input flow. 

The reciprocating compressor is a positive displacement, intermittent flow machine and operates at a fixed volume in its basic configuration. 

Figure 4-20. Efficiency comparison between a variable-volume ratio and a fixed-volume ratio compressor. These compressors have an asymmetric rotor profile [4].

Enhancement of gas storage capacity through adsorption occins when the overall storage density is increased above that of the normal gas density at a given pressure. The adsorbed phase has a greater density than the gas phase in equilibrium with it. However, enhancement in a storage system of fixed volume can only happen if a greater amount of gas is adsorbed compared to the volume of gas displaced by the adsorbent volume. 

Figure 11-19. Fixed volume clearance pocket. [Courtesy of Dresser-Rand Company.]...

Variable clearance that can be changed very readily can be built into the cylinder. Figure 11-19 is an example of a fixed volume clearance pocket mounted on the cylinder. This type is separated from the cylinder by a valve that can be opened and closed from the outside. 

It can be seen from Equation 11-7 that as R is increased, and as clearance is incre ised, volumetric efficiency is reduced. The relationship of volumetric efficiency and clearance is important, because it allows variable clearances (both fixed volume and adjustable volume pockets) to be used to control capacity and obtain the maximum use of available driver horsepower. 

It is not common practice, but quite viable, to inject the flow marker at a predetermined volume offset from the polymer injection. This can be accomplished either with a second injection at a predetermined time into the run or by having two coordinated injection valves separated by a fixed volume of tubing. This approach can avoid many of the pitfalls described earlier. However, the mathematics of this correction is slightly different from that for a coinjected marker. The proper correction for the delayed volume injection is shown in Eq. (3) ... 

A six-port valve was first used to interface the SEC microcolumn to the CZE capillary in a valve-loop design. UV-VIS detection was employed in this experiment. The overall run time was 2 h, with the CZE runs requiring 9 min. As in the reverse phase HPLC-CZE technique, runs were overlapped in the second dimension to reduce the apparent run time. The main disadvantage of this yu-SEC-CZE method was the valve that was used for interfacing. The six-port valve contributed a substantial extracolumn volume, and required a fixed volume of 900 nL of effluent from the chromatographic column for each CZE run. The large fixed volume imposed restrictions on the operating conditions of both of the separation methods. Specifically, to fill the 900 nL volume, the SEC flow rate had to be far above the optimum level and therefore the SEC efficiency was decreased (22). 

The second interface design that was developed for use with yu-SEC-CZE used the internal rotor of a valve for the collection of effluent from the SEC microcolumn. The volume collected was reduced to 500 nL, which increased the resolution when compared to the valve-loop interface (20). However, a fixed volume again presented the same restrictions on the SEC and CZE operating parameters. An entirely different approach to the interface design was necessary to optimize the conditions in both of the microcolumns. 

The total fixed volume of a mixture of gases and vapors at a giv en condition is the same as the olume of any one component (gas laws), and its pressure is composed of the sum of the individual partial pressures of each component. 

Figure 12-2E. 250 psig working pressure cylinder used in refrigeration service. Auxiliary stuffing box for added sealing on shutdown. Manual fixed volume clearance pockets for capacity control. (Used by permission Bui. L-679-BIA, 1957. Dresser-Rand Company.)... 

CLEARANCE POCKET shown in the head is the manual fixed-volume type. 

The clearance pockets may be of many different shapes and arrangements (see Figures 12-6B, 12-30A, and 12-30B). Fixed volume pockets allow for fixed or set volume changes while the variable volume designs allow for changes to suit a particular operating condition or balance and are of value when the cylinder must be used in several different alternating applications. 

If a fixed volume of the solution is chosen as the basis, the concentration of a component (or dissolved species) can be expressed in one of the following ways ... 

Thermochemistry is concerned with the study of thermal effects associated with phase changes, formation of chemical compouncls or solutions, and chemical reactions in general. The amount of heat (Q) liberated (or absorbed) is usually measured either in a batch-type bomb calorimeter at fixed volume or in a steady-flow calorimeter at constant pressure. Under these operating conditions, Q= Q, = AU (net change in the internal energy of the system) for the bomb calorimeter, while Q Qp = AH (net change in the enthalpy of the system) for the flow calorimeter. For a pure substance. 

In a compressor, pressure is generated by pumping quantities of gas into a tank or other pressure vessel. Progressively increasing the amount of gas in the confined or fixed-volume space increases the pressure. The effects of... 

Viscosity is normally determined by measuring the time required for a fixed volume of a fluid, at a given temperature, to flow through a calibrated orifice or capillary tube. The instmments used to measure the viscosity of a liquid are known as viscosimeters. 

Both procedures measure the time for a fixed volume of the sample to flow though a calibrated tube at a controlled temperature. 

Matter is anything that has mass and occupies space. It exists in three phases solid, liquid, and gas. A solid has a fixed shape and volume. A liquid has a fixed volume but is not rigid in shape it takes on the shape of the container. A gas has neither a fixed volume nor a rigid shape it takes on both the volume and the shape of the container. 

The device most commonly used to measure volume in general chemistry is the graduated cylinder. A pipet or buret (Figure 1.8) is used when greater accuracy is required. A pipet is calibrated to deliver a fixed volume of liquid—for example, 25.00 mL—when filled to the mark and allowed to drain. Variable volumes can be delivered accurately by a buret, perhaps to 0.01 mL. 

Measuring volume. A buret (left) delivers an accurately measured variable volume of liquid. A pipet (right) delivers a fixed volume (e.g.. 25.00 mL) of liquid. 

The ideal gas law offers a simple approach to the experimental determination of the molar mass of a gas. Indeed, this approach can be applied to volatile liquids like acetone (Example 5.4). All you need to know is the mass of a sample confined to a container of fixed volume at a particular temperature and pressure. 

A container of fixed volume contains two moles of gas at room temperature. The pressure in the container is four atmospheres. Three more moles of gas are added to the container at the same temperature. Use the result just stated to show that the pressure is now 10 atmospheres. 

The Dafert pipette (Fig. 3.2 Section 3.11) is a convenient apparatus for dispensing fixed volumes of a standard solution, as are also the various liquid dispensers which are available. 

The introduction of the sample into the adsorbent layer is a critical process in HPTLC. For most quantitative work a platinum-iridium capillary of fixed volume (100 or 200 nL), sealed into a glass support capillary of larger bore, provides a convenient spotting device. The capillary tip is polished to provide a smooth, planar surface of small area (ca 0.05 mm2), which when used with a mechanical applicator minimises damage to the surface of the plate spotting by manual procedures invariably damages the surface. 

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