Drop evaporated

The discussion of laminar diffusion flame theory addresses both the gaseous diffusion flames and the single-drop evaporation and combustion, as there are some similarities between gaseous and Hquid diffusion flame theories (2). A frequentiy used model of diffusion flames has been developed (34), and despite some of the restrictive assumptions of the model, it gives a good description of diffusion flame behavior. 

The presence of gaseous ions will make it difficult to dry a gas thoroughly. This is perhaps best seen from energy considerations. If Q is the charge on a drop of liquid of radius R, the electrical energy is Q2/R. As the drop evaporates R diminishes but... 

Included in Table IV are drop evaporation constants determined for some commercially important fuels. To conserve space the data of Kobayasi 27) are tabulated here in the form of averaged values at various temperature levels. 

W.D. Garrett, Reply to comment on retardation of water drop evaporation with monomolecular surface films, J. Atmos. Sci. 29 (1972) 786-787. 

This is an unstable equilibrium The smaller drops evaporate and dis appear, while larger drops grow due to the vapor condensation. Similar phenomena are characteristic of the synthesis of disperse solids as well Larger crystals grow and overcome smaller crystals that are more soluble. 

Capability to Measure Small Changes in Droplet Size. Several experiments were performed to assess the capability of the interferometer/ visibihty technique to measure drop size changes resulting from changes in the atomization procedure or from subsequent drop evaporation. Using... 

Garrett, W. D., Retardation of Water Drop Evaporation with Mono-... 

Figure 6 Four stages in the production of sea salt aerosol by the bubble-burst mechanism, (a) A bubble rises to the ocean surface thereby forming a thin film at the interface which begins to thin, (b) Flow of water down the sides of the cavity further thins the film which eventually ruptures into many small sea spray particles, (c) An unstable jet, produced from water flowing down the sides of the cavity, releases a few large sea spray drops, (d) Tiny salt particles remain airborne as drops evaporate a new bubble is formed. Note the scale change between (a) to (c) and (d) (after...

We are interested in the dispersion of a small amount of liquid solution in an SCF at P < Fn, that is, the system is far from thermodynamic equilibrium, with resulting heat and mass exchange between the drops and their supercritical environment. The simplest model that can be used in this case is the classical model of drop evaporation (58) that predicts a linear decrease of the squared droplet diameter in time and is often referred to as the law ... 

In recent years a great many studies have reported on the dynamic systems where a drop of liquid is placed on a smooth solid surface. ° The system liquid drop-solid is a very important system in everyday life, for example, rain drops on tree leaves or other surfaces. It is also significant in all kinds of systems where a spray of fluid is involved, such as in sprays or combustion engines. The dynamics of liquid drop evaporation rate is of much interest in many phenomena. The liquid-solid interface can be considered as follows. Real solid surfaces are, of course, made up of molecules not essentially different in their nature from the molecules of the fluid. The interaction between a molecule of the fluid and a molecule of the boundary wall can be regarded as follows. The molecules in the solid state are not as mobile as those of the fluid. It is therefore permissible for most purposes to regard the molecules in the solid state as stationary. However, complexity arises in those liquid-solid systems where a layer of fluid might be adsorbed on the solid surface, such as in the case of water-glass. 

Systematic studies have been reported in the literature on the various modes of liquid drop evaporation when placed on smooth solid surfaces. ... 

Measurement of contact angles appears to be quite easy when first encountered, but this can be misleading and the accurate measurement of thermodynamically significant contact angles requires painstaking effort. If the substrate is not prepared properly, if very pure liquids are not used while forming drops and if some important practical issues during measurement, such as drop evaporation, the location of the needle in the drop, and... 

Receding contact angle determination from drop evaporation... 

Drop evaporation theory for spherical and ellipsoidal drops... 

Next, a method was developed to determine the initial peripheral contact angle, 9, of sessile drops on solid surfaces from the diffusion controlled rate of drop evaporation, for the constant drop contact radius mode. Application of this method requires use of the product of the vapor diffusion coefficient of the evaporating liquid, with its vapor pressure at the drop surface temperature (l)APv), which can be found directly from independent experiments following the evaporation of fully spherical liquid drops in the same chamber. It is then possible to calculate 9,p, from... 

Erbil, H.Y. (1998). Determination of Peripheral Contact Angle of Sessile Drops on Solids from the Rate of Drop Evaporation./. Phys. Chem. B, 102, 9234-9238. 

Erbil, H.Y. and Dogan, M. (2000). Determination of Diffusion Coefficient - Vapor Pressure Product of some Liquids from Hanging Drop Evaporation. Langmuir, 16, 9267-9272. 

Erbil, H.Y., McHale, G. and Newton, M.I. (2002). Drop Evaporation on Solid Surfaces Constant Contact Angle Mode. Langmuir, 18, 2636-2641. 

Because of the low individual coefficient on the gas side, the overall coefficient in the desuperheater section is small, and the area of the heating surface in that section is large in comparison with the amount of heat removed. This situation should be avoided in practice. Superheat can be eliminated more economically by injection of a spray of liquid directly into the superheated vapor, since small drops evaporate very rapidly, cooling the vapor to the saturation temperature. The desuperheating section is thereby eliminated, and condensation occurs with high coefficients. 

As a drop evaporates, the Niisselt number gets smaller and approaches 2,0, To simplify the analysis, assume Nu = 2,0, The drops injected into warm air soon reach the wet-bulb temperature. Heat transferred to a drop ... 

This is the initial or maximum value of Nu. As the drop evaporates, Ut and Re decrease, and Nu approaches 2.0. Use Nu = 2.0 to simplify the analysis, since h then varies with Dp . Heat balance on drop ... 

---