Spray isothermal

Measurements have been made of the combustion characteristics of an air blast kerosene spray flame and of droplet sizes within the spray boundary of isothermal sprays. Specific techniques were used to measure velocity, temperature, concentration, and droplet size. Velocities measured by laser anemometer in spray flames in some areas are 400% higher than those in isothermal sprays. Temperature profiles are similar to those of gaseous diffusion flames. Gas analyses indicate the formation of intermediate reactants, e.g., CO and Hg, in the cracking process. Rosin-Rammler mean size and size distribution of droplets in isothermal sprays are related to atomizer efficiency and subsequent secondary atomizer/vaporization effects. 

Measiurements in the isothermal spray using the laser diffraction meter are shown in Figure 7. Mean droplet diameter, as a fimction of... 

Figure 7. Mean diameter of droplets and spread of size distribution N in isothermal spray. Measurements were made by laser diffraction meter across the spray at various axial locations.

On the basis of measurements of velocity, temperature, and gas concentration in spray flames and droplet size measurements in isothermal sprays, the following conclusions have been reached. 

Measured velocities in spray flames were higher than those in isothermal sprays. The acceleration of the flow is caused by increases in volumetric flow rate as a result of an increase in temperature and the change from liquid to vapor phase. 

Measurements of mean size and size distribution of droplets in isothermal sprays by the laser diffraction meter show break-up of large droplets into smaller droplets, followed by preferential vaporization of smaller droplets, resulting in increases in mean droplet diameter and... 

The ammonium perchlorate solution is spray-dried to the desired crystal size at air temperatures below 150°C and crystal temperatures of about 110°C. This procedure provides a pure product having a controlled grain size. Prior mechanical and thermal treatment affects the isothermal... 

It can be seen from Figure 13.5 that for the air-water system a straight line, of slope equal to the enthalpy of dry saturated steam (2675 kJ/kg), is almost parallel to the isothermals. so that the addition of live steam has only a small effect on the temperature of the gas. The addition of water spray, even if the water is considerably above the temperature of the gas, results in a lowering of the temperature after the water has evaporated. This arises because the. latent heat of vaporisation of the liquid constitutes the major part of the enthalpy of the vapour. Thus, when steam is added, it gives up a small amount of sensible heat to the gas, whereas when hot liquid is added a small amount of sensible heat is given up and a very much larger amount of latent heat is absorbed from the gas. 

The spray paint can was inverted and a small amount of product was dispensed into a 20 mL glass headspace vial. The vial was immediately sealed and was incubated at 80°C for approximately 30 min. After this isothermal hold, a 0.5-mL portion of the headspace was injected into the GC/MS system. The GC-MS total ion chromatogram of the paint solvent mixture headspace is shown in Figure 15. Numerous solvent peaks were detected and identified via mass spectral library searching. The retention times, approximate percentages, and tentative identifications are shown in Table 8 for the solvent peaks. These peak identifications are considered tentative, as they are based solely on the library search. The mass spectral library search is often unable to differentiate with a high degree of confidence between positional isomers of branched aliphatic hydrocarbons or cycloaliphatic hydrocarbons. Therefore, the peak identifications in Table 8 may not be correct in all cases as to the exact isomer present (e.g., 1,2,3-cyclohexane versus 1,2,4-cyclohexane). However, the class of compound (cyclic versus branched versus linear aliphatic) and the total number of carbon atoms in the molecule should be correct for the majority of peaks. 

Trapaga and Szekely 515 conducted a mathematical modeling study of the isothermal impingement of liquid droplets in spray processes using a commercial CFD code called FLOW-3D. Their model is similar to that of Harlow and Shannon 397 except that viscosity and surface tension were included and wetting was simulated with a contact angle of 10°. In a subsequent study, 371 heat transfer and solidification phenomena were also addressed. These studies provided detailed... 

Despite some conflicting evidence (Kinsella and Fox, 1986), it appears that denaturation has little influence on the amount of water bound by whey proteins. However, other factors which may accompany denaturation (e.g. Maillard browning, association or aggregation of proteins) may alter protein sorption behaviour. Drying technique affects the water sorption characteristics of WPC. Freeze-dried and spray-dried WPC preparations bind more water at the monolayer level than do roller-, air- or vacuum-dried samples, apparently due to larger surface areas in the former. As discussed above, temperature also influences water sorption by whey protein preparations. The sorption isotherm for /Mactoglobulin is typical of many globular proteins. 

Figure 6. Moisture sorption isotherms of three ENCAPSULATED ORANGE OILS SPRAY DRIED AT DIFFERENT VOLTAGES a 200v b 150v c 75v.

Figure 5. Isotherms in liquid spray flame with disk stabilizer...

Emas and Nyqist investigated the aging and stabilization of spray-congealed solid dispersions of carnauba wax. Isothermal microcalorimetry (IM) was... 

Gustafsson et al. used SSNMR and isothermal microcalorimetry to investigate the amorphous component of lactose. In general, the detection limits for crystalline forms are much better than for amorphous forms due to the much broader resonances characteristic of disordered systems. The two techniques were found to be in agreement with each other in the characterization of the degree of disorder in the system. Completely amorphous lactose (prepared by spray drying) was mixed with completely crystalline lactose monohydrate... 

Figure 8.6b shows sorption isotherms for dried skim milk, of which about 50% is lactose. The lactose can remain amorphous when the milk is spray-dried. It can also be made with crystalline lactose, and the normal crystalline form is a monohydrate. The water of crystallization is not available as a solvent, which means that aw is smaller than for amorphous sugar at the same water content, provided the latter is fairly small. At higher water content, the curves cross, and amorphous sugar may crystallize, taking up part of the water. 

FIGURE 32.7 Schematic representation of isothermal drying cnrve for the selection of encapsnlating materials for spray-dried microcapsnles (Matsuno and Adachi method). Type 1 curve corresponds to materials that form fine, dense, two-dimensional skins immediate upon drying. Types 2, 3, and 4 curves correspond to materials that do not form dense skins at an early stage of drying. (From Perez-Alonso, C. et al., Carbohydr. Polym., 53, 197, 2003. With permission.)... 

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