Surface condensers illustration

The basic assumption is that the Langmuir equation applies to each layer, with the added postulate that for the first layer the heat of adsorption Q may have some special value, whereas for all succeeding layers, it is equal to Qu, the heat of condensation of the liquid adsorbate. A furfter assumption is that evaporation and condensation can occur only from or on exposed surfaces. As illustrated in Fig. XVII-9, the picture is one of portions of uncovered surface 5o, of surface covered by a single layer 5, by a double-layer 52. and so on.f The condition for equilibrium is taken to be that the amount of each type of surface reaches a steady-state value with respect to the next-deeper one. Thus for 5o... 

A 2-litre round-bottomed flask provided with the adapter illustrated in Fig. II, 1, 8, d may also be used. For preparations on one half or one quarter of this scale, a 1000 or 500 ml. flask equipped with an efficient double surface condenser will give reasonably good results. 

Condensers may be of one or two general types depending on the specific application. Contact condensers operate with the coolant, vapors, and condensate intimately mixed. In surface condensers, the coolant does not come in contact with either the vapors or the condensate. The usual shell-and-tube condenser is of the surface type. Figure 29-14 illustrates a contact condenser which might be used to clean or preclean a hot corrosive gas. 

An assembly for heating a reaction mixture under reflux is illustrated in Fig. 2.54. The precise design of condenser depends upon the volatility of the reaction liquid, low boiling liquids (<60°C) require the use of a double surface condenser. Additionally a calcium chloride tube may be inserted at the end of the condenser if the reaction mixture contains moisture-sensitive components. It is... 

Figure 20.16 schematically illustrates the process of titania film growth by ALD. The substrate is hydroxylated first, prior to the introduction of titanium precursor, titanium tetrachloride. Titanium tetrachloride reacts with the surface hydroxyl groups through a surface condensation reaction ... 

Water vapor diffusion coefficients as functions of time are shown in Fig, 8. Values obtained from (2), (3), and (4) are all shown for comparison. Due to the scatter obtained, coefficients resulting from (2) are shown as a band of values rather than a single curve. Such a coefficient should be a function of the partial pressure gradient across the diffusional boundary layer. However, under the ambient conditions existing during this study, this quantity was essentially constant, and no partial pressure relationship was determined. However, the effect of boundary layer condensation without subsequent adherence to the container surface is illustrated by the data shown in Fig. 8. Equations (2), (3) and (4) pro-... 

Figure 4.17 Schematic illustration of an effluent free vapour jet vacuum pump with surface condensation.

Exhibit 4-27 illustrates how primary process considerations govern the elevation of the surface condenser and some of its auxiliary equipment. Because a pump is needed to remove the condensate from the hot well, the pump net positive suction head (NPSH) must be satisfied to operate satisfactorily. Vertical pumps are generally used in this application because the NPSH requirement is calculated from the bottom of the lower impeller for vertical pumps, compared with the centerline of the inlet nozzle for horizontal pumps. Setting the elevation of the inter-after condenser, usually located to the side of the suifice condenser, can be done with fewer restriaions. Ilie bottom of the inter-after condenser shell must not be more than 3 ft (900 mm) below the condensate return nozzle on the side of the hot well. The plant layout designer is then free to set the elevation as high as necessary. 

It was pointed out that a bimolecular reaction can be accelerated by a catalyst just from a concentration effect. As an illustrative calculation, assume that A and B react in the gas phase with 1 1 stoichiometry and according to a bimolecular rate law, with the second-order rate constant k equal to 10 1 mol" see" at 0°C. Now, assuming that an equimolar mixture of the gases is condensed to a liquid film on a catalyst surface and the rate constant in the condensed liquid solution is taken to be the same as for the gas phase reaction, calculate the ratio of half times for reaction in the gas phase and on the catalyst surface at 0°C. Assume further that the density of the liquid phase is 1000 times that of the gas phase. 

In moist enviromnents, water is present either at the metal interface in the fonn of a thin film (perhaps due to condensation) or as a bulk phase. Figure A3.10.1 schematically illustrates another example of anodic dissolution where a droplet of slightly acidic water (for instance, due to H2SO4) is in contact with an Fe surface in air [4]. Because Fe is a conductor, electrons are available to reduce O2 at the edges of the droplets. 

Figure C2.11.6. The classic two-particle sintering model illustrating material transport and neck growtli at tire particle contacts resulting in coarsening (left) and densification (right) during sintering. Surface diffusion (a), evaporation-condensation (b), and volume diffusion (c) contribute to coarsening, while volume diffusion (d), grain boundary diffusion (e), solution-precipitation (f), and dislocation motion (g) contribute to densification.

This principle is illustrated in Figure 10 (45). Water adsorption at low pressures is markedly reduced on a poly(vinyhdene chloride)-based activated carbon after removal of surface oxygenated groups by degassing at 1000°C. Following this treatment, water adsorption is dominated by capillary condensation in mesopores, and the si2e of the adsorption-desorption hysteresis loop increases, because the pore volume previously occupied by water at the lower pressures now remains empty until the water pressure reaches pressures 0.3 to 0.4 times the vapor pressure) at which capillary condensation can occur. 

Figure 11.7 illustrates the internal surface at the inlet end of the condenser. Approximately 2 in. (5 cm) of the surface is marked by mutually intersecting depressions and grooves. Areas of the internal surface downstream of this zone are smooth and covered with a thin layer of deposits. This typical case of inlet-end erosion can be eliminated by the techniques discussed earlier in this chapter under Elimination. ... 

Recent failures of the type illustrated in Fig. 12.21 affected a total of eight tubes in this condenser. Metal loss occurred exclusively on the top and bottom internal surfaces. Affected areas have a rough, jagged contour of deep, overlapping pits that were essentially free of corrosion products. Unaffected areas of the internal surface are smooth and are covered with a layer of black iron oxide. 

A WBL can also be formed within the silicone phase but near the surface and caused by insufficiently crosslinked adhesive. This may result from an interference of the cure chemistry by species on the surface of substrate. An example where incompatibility between the substrate and the cure system can exist is the moisture cure condensation system. Acetic acid is released during the cure, and for substrates like concrete, the acid may form water-soluble salts at the interface. These salts create a weak boundary layer that will induce failure on exposure to rain. The CDT of polyolefins illustrates the direct effect of surface pretreatment and subsequent formation of a WBL by degradation of the polymer surface [72,73]. 

Evaporators, Horizontal-Tube Type - The basic horizontal-tube evaporator is illustrated in Figure 12. The body of this evaporator is the liquor compartment and is in the form of a vertical cylinder. It is closed, top and bottom, with dished heads, although the bottom may be conical. The lower body ring is provided on opposite sides with steam compartments, closed on the outside by cover plates and on the inside by tube sheets. Between these tube sheets are fastened a number of horizontal tubes. The two steam chests with their connecting mbes form the steam compartment, and the tube wall heating surface. Steam is introduced into one steam chest and as it flows through the tubes it washes non-condensed gases and condensate ahead of it, so that these are withdrawn from the opposite steam chest. 

Figures 6-5 and 6-6 illustrate two-stage ejector installations with barometric and surface t) pe inter-after condensers respectively. The discharge of the steam non-condensables from the second stage jet of Figure 6-5 is exhausted to the atmosphere, while in Figure 6-6 the steam is condensed in the aftercondenser and, essentially, only non-condensables leave the ent of the aftercondenser. Figure 6-7A indicates a diagram of a three-stage barometric type installation.

For solid contacts in vapor atmosphere, liquid would condense from the vapor into cracks and pores formed between the contacting surfaces. As a result, a small liquid bridge appears around the contact spot and a meniscus with the curvature of (l/rj-i- l/r2) forms at the solid-liquid-vapor interface, as illustrated in Fig. 4 for a microscopic sphere in contact with a solid plane. 

Figure 1. Schematic illustration of the laser-vaporization supersonic cluster source. Just before the peak of an intense He pulse from the nozzle (at left), a weakly focused laser pulse strikes from the rotating metal rod. The hot metal vapor sputtered from the surface is swept down the condensation channel in dense He, where cluster formation occurs through nucleation. The gas pulse expands into vacuum, with a skinned portion to serve as a collimated cluster bean. The deflection magnet is used to measure magnetic properties, while the final chaiber at right is for measurement of the cluster distribution by laser photoionization time-of-flight mass spectroscopy.

Manning (1969) suggested that there is a critical charge density above which counterions condense on the surface of the polyion. This phenomenon is most clearly illustrated by the simple case of iiffinite dilution. As 0->O in equation (4.11), the graph of P against Q falls into two parts about the critical point 2=1 ... 

The large amount of S in the particles suggested that S02 gas molecules or small sulfur-containing particles condense on to the surface of soil dusts during their transportation from China. Figure 4.22 illustrates an elemental map for Si distribution in coarse particles within a total scanning area of 25 pm x 25 pm. The scale bar shows the peak count of characteristic X-rays by pixel of the scan area. 

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