Flow displacement

Note that the supply air should be at least 1-2 colder than the air in the lower part of the room in order to make the supply air layer at floor level. Thus, the ventilation air cannot be used for heating the room. 

The dimensioning of displacement ventilation is shown in the example in Section 7.5.4. That given above is an example of displacement ventilation with weak thermal stratification. Even though the stratification is weak, the contamination in the lower, cleaner zone is normally on the order ol onc-rhird of the contamination in the upper zone. 

An example of displacement ventilation with cold contaminants is shoun in Fig. 8.31. The contaminants, i.c., the fumes from the sewer, are colder than the room air, and thus tend to stay low due to the negative buoyancy. 

A good arrangement in this case is to locate the air supply below the ceiling. The supply air should not be colder than the room air, in order to layer below the ceiling. The fresh air will fill the room from above. 

In this case, hearing is possible by means of the supply air. 

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Fast Rinse Cycle - The fast rinse step is essentially the service cycle except that the effluent is diverted to waste until quality is proven. This final rinse is always in the same direction as the service flow. Therefore, in countercurrent systems the displacement flow and rinse flows will be in opposite directions. 

FIGURE 7.1B General exhaust placed to give a displacement flow through a passage. 

When special contaminating processes are located in a seini-enclosed parr of a room as in Fig. 7.18, the exhausts should be located so that a displacement flow is created through the passage into the semi-enclosure. With this arrangement there may be no need for a door, which may be very practical. 

Location of General Exhaust to Create Displacement Flow... 

Displacement flow, actual Actual flow pattern in an enclosure, resulting in uniform air distribution with virtually no mixing. 

Displacement flow, ideal Ideal flow pattern in an enclosure, in which uniform air diffusion is provided without mixing. 

Low-velocity ATD An air terminal device which is designed for thermally controlled ventilation, e.g., displacement flow applications. See also Air terminal device. 

Fig. 7. A pattern for displacing flow curves of filled polymers with the growth in temperature. The arrow indicates the direction of temperature growth...

U. Narang, P.R. Gauger, and F.S. Ligler, Capillary-based displacement flow immunosensor. Anal. Chem. 69, 1961-1964 (1997). 

Figure 7.12 Qualitatively predicted particle trajectories in the laboratory frame (screw rotation) a) flow in the z direction (towards the inlet) due to the motion of the core, b) positive displacement flow in the x-y plane. The spacing between the particles is at equal time intervals. The relative positions indicate the speed of the particles. That is, the particles are moving faster near the root of the screw...

A Displacement Flow Immunosensor for Explosive Detection Using Microcapillaries, Anal. Chem. 1997, 69, 2779. 

In a displacement flow meter, all of the fluid passes through the meter in almost completely isolated quantities. The number of these quantities is counted and indicated in terms of volume or weight units by a register. 

The most common type of displacement flow meter is the nutating disk, or wobble plate meter. A typical nutating disk is shown in Figure 7. 

Steady Mechanical Displacement Flow Aided by Drag, 159... 

We now analyze mechanical-displacement flow in a straight channel of constant cross-sectional area, as shown in Fig. 4.11 (with the upper plate at rest). A column of compacted solids of length L is compressed between two rams. The one on the left exerts a force Fo on the solids and it is opposed by a smaller force FL on the right. Thus, friction on the channel walls also opposes the applied resultant force. 

STEADY MECHANICAL DISPLACEMENT FLOW AIDED BY DRAG 159... 

First we want to gain some insight into the nature and mechanism of positive displacement flow. In the next two examples we examine the plunger-cylinder... 

Fig. 6.37 Schematic representation of four geometrical configurations utilizing external mechanical pressurization giving rise to positive displacement flow, (a) Axially moving plunger in a cylinder, (b) Squeezing disks, (c) Intermeshing gear pump, (d) Counterrotating intermeshing twin screws.

To inject the polymer melt into the mold, the melt must be pressurized. This is achieved by the forward thrust of the screw (a) or the piston (b), both of which act as rams. Hence we have static mechanical pressurization, as discussed in Section 6.7, which results in positive displacement flow. 

Displacement chromatogram of a chloroaniline mixture containing 44.7 umol of the meta isomer, 29.8 umol of the ortho isomer and 16.4 umol of the para isgmer. Conditions 50 cm x 4.6 mm ID beta-cyclodextrin-silica column, carrier solvent 10 % v/v methanol water displacer 13 mM p-nitrophenol dissolved in the carrier solvent displacer flow-rate 0.2 mL/min column temperature 30 C. 

The displacement flows can be miscible (brine after polymer solution, C02 after oil, steam after water) or immiscible (water after oil). In the former case, it is the mixing process itself which has to be understood and modeled steam recovery requires the thermal transport problem to be accurately modeled. In the latter case, the two fluid phases coexist within the porous medium their relative proportions are determined not only by flow and mixing processes, but equally by interfacial and surface tensions between the three phases (matrix material included). Local (capillary) variations in pressure between the two fluid phases become important. The overall flow field is determined by large-scale pressure gradients. 

The most used methods for the characterization of flow and species transport inside a porous body include the identification of the characteristics of the pores of the porous structure and the particularisation of classic transport equations to this case. These equations are generally associated with equations describing the solid-fluid interaction, adsorption, capillary condensation and flow due to the capillary forces etc. Concerning the species displacement (flow) problem inside a porous structure, we can consider the following classification ... 

Positive displacement flow meters, or PD meters, are used more than all other flow measurement devices [10] a typical PD flow meter is shown in Figure 4.22. Millions of PD... 

A = horizontal tube displacement flow reactor = rotary vertical batch type reactor... 

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