Open evaporation process

Figure 1.3. Open evaporation process (open distillation), x, y, composition of liquid and equrtibrium vapor phases L, amount of liquid dL, infinitesimal amount of evaporated hquid.

The residue curve represents the change in a mixture composition during the open evaporation process. Each point of this line corresponds to a certain moment of time and to a portion of evaporated liquid. 

Emission from an open liquid face (e.g., open tanks, liquid spills on the floor surface) can be evaluated using equations based on criteria relations and empirical data. Assuming that the heat and mass transfer processes can be described using similar differential equations, the criteria equation describing the evaporation process will be similar to one describing the heat transfer ... 

A. Batch Process (Refs 93, 102). The saturated solution from the storage tank is gravity fed to open evaporating pans ("high pans ) provided with stainless steel or aluminum heating coils and air agitation. The soln is evaporated to about 98% at a temp of... 

Continuous water recirculation system, whereby cooling water picks up heat by being pumped through a process heat source or heat exchanger and then over a cooling tower, open to the air, whereupon the sensible heat gained is lost by an evaporation process. 

The evaporation velocity at ambient pressure and, say, 60 °C, which corresponds to a mole fraction in the sweep gas of about 30 % water vapor, is about uuq = IO-5 m s-i. This results in Kj , = 0.904 which is rather close to 1, so that the effect of the liquid phase mass transfer resistance on the selectivity of an open distillation process with a free gas-liquid interface in most cases can be ignored. If, however, kuq becomes very small (as in the pervaporation process described in the next example), Kuq might become very small and thus reduce the selectivity of the open distillation process practically down to zero. 

All the normal considerations associated with DSC measurements are applicable to the study of hydrates, although particular care must be given to the choice of pan used. The use of hermetically sealed pans often leads to suppression of the water loss peak because of the buildup of headspace pressure within the vessel, which in turn alters the equilibrium of the dehydration or evaporation process. In this respect, several authors have recommended the use of open pans to study hydrates as the water loss peak is clearly seen under these circumstances. A further possibility is... 

All the theoretical results have been compared with measurements on 20-28 pm particles (dark circles) and 50-63 pm particles (open circles) Fig. 29 a. If velocity measurements are in good agreement with the calculations, the measured temperatures are from 100 to 600 K lower than the predicted ones. However, it is to be noticed that the measurements represent mean values and that the particles in their totality do not follow the jet axis. The same calculations have been performed for a particle trajectory like that represented with shaded line on Fig. 25 a. In this case a strong evaporation process occurs too, leading to a 50 % particle radius diminution. 

Our investigation shows that the vapor pressures of solid bismuth and antimony tellurides and of bismuth selenide are quite low. The working temperatures of thermoelements made of these substances do not exceed 700 C. Under such conditions, the evaporation of thermoelements should be of little significance, especially as the loss of matter from open surfaces occurs at a rate which is 6—65 times slower than the equilibrium rate of evaporation. The values of the evaporation coefficient (0.15-0.16) found in our study show that the evaporation process is fairly complex. This is supported by thermodynamic calculations, which demonstrate that the evaporation is of a dissociative nature. 

The heat transfer experiments conducted at Oak Ridge differed from the HTTR system in that the water used at, Oak Ridge was cycled in an open system whereby oxygen and nitrogen of the air were readily dissolved. It is expected that any gaSes in the MTR process water will be practically completely removed by the flash evaporation process, and therefore the corrosion rates may be even less than those determined by the experiments conducted at ORNL,... 

The static suspension method for preparing adsorption layer open tubular columns (ALOT) was suggested by Haiasz and Horvath [16, 17]. The columns prepared by this method have been successfully used for many separations. Haiasz and Horvath [16] filled stainless steel capillaries (50 m) with stable suspensions of many combinations of solid and liquid stationary phases, then closed the capillaries at one end and passed them through a furnace, where the solvent used to prepare the suspension evaporated through the open end. In this evaporation process the solid part of the suspension was retained on the capillary wall. This method was successfully used by Ettre and coworkers [18, 19] to produce efficient columns (a 45 m column has 57,000 theoretical plates). 

However, tie-lines can cross each other. That is why, for phase equilibrium characteristics in the concentration space, it is convenient to use another kind of line, the so-called residue curves. Let s consider a process of open evaporation simple distillation) illustrated in Fig. 1.3. 

The analogy with the process of open evaporation favored the fact that this mode was investigated earlier than the others. Systematic examination of distillation at the infinite reflux was initially carried out in works (Zharov Serafimov, 1975 Balashov Serafimov, 1984). The analysis of infinite reflux mode in the infinite columns was made (Petlyuk, 1979 Petlyuk, Kievskii, Serafimov, 1977 Petlyuk Serafimov, 1983) that allowed general regularities of separation to be defined for the mixtures with any number of components and azeotropes. A number of important investigations was realized (Doherty, 1985 Doherty Caldarola, 1985 Laroche et al., 1992 Bekiaris et al., 1993 Safrit Westerberg, 1997 Rooks et al., 1998) and others. 

Figure 9.14 Influence of solvent evaporation process on flnal particle size for PCL = 14,000) and PEGylated copolymer (initial concentration 6 mg/mL in acetone) both nanopheres of pure polymer and nanocapsules containing Miglyol are shown. Nanoparticles size measured after synthesis and quench in CIJM-dl (open symbols) and after solvent evaporator in a rotating evaporator (filled symbols) PCL...

Open steady-flow systems, which include almost all air conditioning processes, foUow this law. Examples include the energy flows in a cooling and dehurnidifying coil or an evaporative cooling system. 

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