Drying surface evaporation

Emulsified asphalt used as a protective coating is specified by ASTM D1227 (10). These emulsions ate appHed above freezing by bmsh, mop, or spray, and bond to either damp or dry surfaces. Such appHcation is not recommended for inclines <4° to avoid the accumulation of water. However, curing by water evaporation can be slow, and these emulsions may remain water-susceptible. 

Surface evaporation can be a limiting factor in the manufacture of many types of products. In the drying of paper, chrome leather, certain types of synthetic rubbers and similar materials, the sheets possess a finely fibrous structure which distributes the moisture through them by capillary action, thus securing very rapid diffusion of moisture from one point of the sheet to another. This means that it is almost impossible to remove moisture from the surface of the sheet without having it immediately replaced by capillary diffusion from the interior. The drying of sheetlike materials is essentially a process of surface evaporation. Note that with porous materials, evaporation may occur within the solid. In a porous material that is characterized by pores of diverse sizes, the movement of water may be controlled by capillarity, and not by concentration gradients. 

To check the efficacy of grease removal, the alkali solution is rinsed away or neutralised by dipping in dilute acid. If, after removal from the acid, the draining metal surface remains wetted evenly all over for 30-60 s (or until it dries by evaporation), hydrophobic soils have been removed. Traces of grease cause the surface to de-wet, and surface tension draws the water into separate droplets. This is the water-break test. Traces of grease which remain when the work is plated do not prevent electrodeposition, but are detrimental to adhesion and corrosion resistance. 

The suction-to-liquid heat exchanger will supply the suction superheat necessary for safe operation of a dry expansion evaporator, and the coil superheat may be less, giving more efficient use of the evaporator surface. The phial should be located before the heat... 

MAISEL and SHERWOOD(46) also carried out experiments in a wind tunnel in which water was evaporated from a wet porous surface preceded by a dry surface of length Lq. Thus, a velocity boundary layer had become established in the air before it came into... 

Trichloroethylene has been detected in a number of rainwater samples collected in the United States and elsewhere (see Section 5.4.2). It is moderately soluble in water, and experimental data have shown that scavenging by rainwater occurs rapidly (Jung et al. 1992). Trichloroethylene can, however, be expected to revolatilize back to the atmosphere after being deposited by wet deposition. Evaporation from dry surfaces can also be predicted from the high vapor pressure. 

Mg of dry mass of a non-porous solid is dried under constant drying conditions in an air stream flowing at 0.75 m/s. The area of surface drying is 55 m2. If the initial rate of drying is 0.3 g/m2s, how long will it take to dry the material from 0.15 to 0.025 kg water/kg dry solid The critical moisture content of the material may be taken as 0.125 kg water/kg dry solid. If the air velocity were increased to 4.0 m/s, what would be the anticipated saving in time if the process were surface-evaporation controlled ... 

This shows that surface evaporation into a dry atmosphere has the form of an Arrhenius rule for a zeroth-order chemical reaction. 

The program is written with two logical control variable flags, one takes the value of 1.0 to control the surface evaporation and the other a value of 1.0 to start the diffusional drying process. Array notation for the number of solid segments is used to allow plotting the concentration versus distance at any desired time. 

Efflorescences or crusts are formed either by the partial or complete drying up of the lakes or ponds during summer, or else by the surface evaporation of subsoil moisture carried to the surface by capillary action. 

Dry equipment is required for most processes carried out in biochemistry laboratory. When you needed dry glassware in organic laboratory, you probably rinsed the piece of equipment with acetone, which rapidly evaporated, leaving a dry surface. Unfortunately, that surface is coated with an organic residue consisting of nonvolatile contaminants in the acetone. Since... 

If Soln. E is allowed to dry by evaporation at 0°C (Fig. 5.14c) or freezing to the eutectic (Fig. 5.14d), then the distribution of precipitated salts is similar to Soln. C except for the large increase in MgSC>4 salts (cf. Figs. 5.14a,b with 5.14c,d). Exactly the same suite of salts precipitate for Solns. C and E. Also, the eutectic temperature is the same (—35.4°C). For Soln. E, the salt quantities fall in the order (MgNa)SC>4 > NaCl > (MgCa)CC>3, in agreement with estimates of salt distribution on the Martian surface (Clark and Van Hart 1981). 

Leveque, J., Hydration in psoriasis and eczema the dry surface-high evaporative water loss paradox, in Eisner, P., Berardesca, E., and Maibach, H. (Eds.), Bioengineering of the Skin Water and the Stratum Comeum, CRC Press, Boca Raton, pp. 243-249, 1994. 

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