Evaporation, thermal surface

The quasi-one-dimensional model of flow in a heated micro-channel makes it possible to describe the fundamental features of two-phase capillary flow due to the heating and evaporation of the liquid. The approach developed allows one to estimate the effects of capillary, inertia, frictional and gravity forces on the shape of the interface surface, as well as the on velocity and temperature distributions. The results of the numerical solution of the system of one-dimensional mass, momentum, and energy conservation equations, and a detailed analysis of the hydrodynamic and thermal characteristic of the flow in heated capillary with evaporative interface surface have been carried out. 

Different mass spectrometric techniques can be classified according to the evaporation and ionization methods applied. Evaporation of solid samples can be performed, for example, by thermal (e.g., on a hot tantalum filament or in a heated graphite furnace) or laser-induced evaporation, and by electron or ion bombardment. Electron ionizaton (El), ionization during the sputtering process with a primary ion beam, resonant or non-resonant laser ionization or thermal surface ionization... 

For the study of crystalline surfaces, ultrahigh vacuum (UHV) is required. The preparation of clean crystalline surfaces is usually carried out within the UHV system by cleavage, sputtering, evaporation, thermal treatment, or molecular beam epitaxy. 

If the air space of the wind-wave flume is flushed with dry air (relative humidity approximately 75%), a latent heat flux is established through evaporation. The surface temperature drops a few tenth of a degree ( cool skin ) and skin-bulk temperature difference is forced across the thermal sublayer. 

The rotors may be one of several zero-clearance designs, a rigid fixed clearance type, or in the case of tapered rotors, an adjustable clearance construction type (Fig. 16). One vertical design includes an optional residence time control ring at the end of the thermal surface to hold back product and thus build up the film thickness. The majority of thin-film evaporators in operation are the vertical design with a cylindrical fixed-clearance rotor shown in Fig. 14. 

The absence of fragment ions characterized the thermal surface ionization mass spectra of the sodium salts of alkylbenzenesulfonic acids24. The observed [nM + Na]+ ions, m = 1—2, were suggested to derive from a stepwise process involving evaporation of neutral clustered molecules followed by ionization and dissociation on the surface of the hot wire. 

The energy performance of a dryer and a drying process is characterized by various indices such as volumetric evaporation rate, surface heat losses, steam consumption, unit heat consumption, and energy (thermal) efficiency. Of all these indices, the energy efficiency / is most frequently quoted in technical specifications. It commonly relates the energy used for moisture evaporation at the solids feed temperature ( , ) to the total energy supplied to the dryer ( ,) ... 

Thin-film evaporators are mechanically-aided, turbulent film devices. These evaporators rely on mechanical blades that spread the process fluid across the thermal surface of a single large tube. All thin-film evaporators have three major components a vapor body assembly, a rotor, and a drive system (Figure 11-23). 

Materials that Tend to Foul. Because of high turbulence imparted by the rotor and excellent localized mixing, fouling of the thermal surface is not generally a problem with thin-film evaporators. Approximately ten rotor blades pass each point on the heat transfer surface every second and the surface is "washed each time. 

Weter Leekage When water from external sources enters the process side of the evaporator, thermal efficiency decreases since such leaks dilute the product and increase the amount of water to be evaporated. Possible sources of water leakage into the process are corroded heat-exchange surfaces, pump seal flushes, barometric condenser water flooding, condenser flushes, and leaking of the water valves used to clean out the evaporator for startup and shutdown. 

In non-laser desorption/laser ionisation techniques selective laser ionisation of gas phase neutrals (atoms and molecules), generated by evaporation, thermal heating, particle or photon bombardment, can be applied. Regarding ionisation, it is possible to differentiate between thermal impact with other particles (LEIS laser-enhanced ionisation), ionisation due to an electric field (FILS field ionisation laser spectrometry) and that due to photoionisation (RIS resonance ionisation spectrometry). This type of ionisation can be combined with a mass spectrometer to detect isotopes selectively (RIMS resonance ionisation mass spectrometry). If a polymer additive is volatile enough its presence can be ascertained via ionisation-only spectra. That is, the additive evaporates from the near-surface region for a certain amount of time, and the ionisation laser alone will yield a reasonable amount of signal to obtain an analysis of the additive present. 

There are hints that the structure of amorphous boron deposited by evaporation on surfaces at lower temperatures are essentially different from those in thermal equilibrium (see Ref. 38 and compare with Ref. 34). 

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