Cooling visual observations

In saturated annular flow boiling, on the other hand, a liquid film annulus normally covers the heating surface and acts as a cooling medium. Thinning of the liquid film annulus, therefore, indicates approaching dryout. The behavior of bubble layers and liquid annuli are of interest to visual observers. 

The nature of the radiation processes is not fully understood. Ball (10,11), with the aid of a stroboscopic shutter, visually observed cool flames as actual flame fronts moving across the combustion chamber of a motored engine. This was later confirmed by Getz (53). The source of cool flame emission in tube experiments has been attributed to excited formaldehyde by Emeleus (51) and Gaydon (52). Cool flame spectra in engines obtained by Levedahl and Broida (70) and Downs, Street, and Wheeler (35) were reported to be due to excited formaldehyde. The nature of the blue flame spectra has not been fully explored, although some evidence points to carbon monoxide emission (35). 

Deposit sample analysis and report interpretation. A minimum of 1 to 2 ounces (25 to 50 grams approximately) is usually required for analysis. Precise details are required concerning the point of sampling from the cooling system, also the date, time, and any relevant operating information and observations. Deposit samples are almost always dried before any further analytical work is undertaken and the results are typically scaled to 100% dried material. (A comparison of visual observations, from the time and place of sampling, with subsequent analytical reports, can provide valuable experience for evaluating similar problems in the future.)... 

FIGURE 3.20 Successive cooling curves for hydrate formation with successive runs listed as Sj < S2 < S3. Gas and liquid water were isochorically cooled into the metastable region until hydrates formed in the portion of the curve labeled Sj. The container was then heated and hydrates dissociated along the vapor-liquid water-hydrate (V-Lyy-H) line until point H was reached, where dissociation of the last hydrate crystal was visually observed. (Reproduced from Schroeter, J.R, Kobayashi, R., Hildebrand, M.A., Ind. Eng. Chem. Fundam. 22, 361 (1983). With permission from the American Chemical Society.)... 

Method. The TLC plates (silica gel) are activated for 30 min at 10S °C, cooled to room temperature and then spotted with a few microlitres of the sample. The chromatograms are developed by ascending chromatography, dried at 80 °C for IS min, cooled to room temperature and exposed to bromine vapour for a period of time ranging from 15 sec to several min. Excess of bromine is removed by means of a stream of cool air passed over the surface of the adsorbent. The plates are then sprayed with DDQ (a fresh 0.1% solution in benzene) and dried for 2 min with a stream of warm air. Visual observations are made with a UV lamp at long wavelength. Spots may be quantitated with a chromatogram scanner in the fluorescence mode. 

VI Flocculation Studies, Critical flocculation temperatures were measured using suspensions of 0.6% v/v latex containing the appropriate amount of sodium chloride. Differing degrees of neutralisation were produced by the addition of NaOH to stock solutions and checked by conductometric titration with base in the absence and presence of added HC1. Flocculation temperatures (CFT) were determined by visual observation at a cooling/heating rate of M).5 C s. The flocculation was generally reversible provided that the latices had not been left in the flocculated state for more than a few minutes or so. 

As mentioned earlier, the melting mechanism in screw extruders was first formulated by Tadmor (29) on the basis of the previously described visual observations pioneered by Bruce Maddock. The channel cross section and that of the solid bed are assumed to be rectangular, as in Fig. 9.26. The prediction of the solid bed width profile (SBP), that is the width of the solid bed X as a function of down-channel distance z, is the primary objective of the model, which can be experimentally verified by direct observation via the cooling experiment of the kind shown in Figs. 9.20-9.25. As shown by Zhu and Chen (40), the solid bed can also be measured dynamically during operation by equipping the extruder with a glass barrel. 

Reversed micelles have very highly dynamic structures and are in rapid equilibrium with surfactant monomers. Therefore, it is usually difficult to observe their real features by microscopy. A freeze-fracture transmission electron microscope (TEM) would probably show the real picture of a reversed micellar solution because a freeze-fracture film of the reversed micelles is made by rapid cooling to — 150°C to stop instantly the dynamic nature of the structure. Figure 2(a) shows an electron micrograph of the AOT reversed micellar solution (5% w/v AOT-iso-octane solution, IV = 1) [44]. The visual observation by a... 

An apparatus in which the controlled heating and cooling sequences demanded in the above technique is depicted in Figure 5.9 and described in section 5.3. Determination of the instant at which all the crystals have finally dissolved in a solution is most commonly made by visual observation. In principle, however, the monitoring of any concentration-sensitive physical or physicochemical property (refractive index, conductivity, density, vapour pressure, particle size distribution, etc.) can offer alternative procedures. 

Neuhauser, W. Hohenstatt M. Toschek, P.E. Dehmelt H.G. Visual observation and optical cooling of electrodynamically contained ions. Appl. Phys. 1978,17,123-129. 

The film produced from a blend of 5 and 6 was cut with a scalpel the separated edges were then placed in close proximity and heated to approximately 90 °C. Visual observation of the material over this temperature ramp showed that the surface remained homogeneous. After cooling back to room temperature, the broken edges had re-engaged, and the material could again be peeled like a continuous polymer film (Fig. 10). 

DSC measurements were carried out on Perkin-Elmer DSC-2 apparatus under an argon atmosphere with a heating or cooling rate of 10 /min. Peak areas were determined by planimetry. The results of DSC measurements were connected with the visual observations of the texture of the samples by means of hot-stage microscope equipped with a pair of crossed polarizers. 

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