Vaporization, microlayer

While a bubble expands or contracts in a liquid, mechanical work is transferred between the bubble and the surrotmding liquid. The kinetic energy transferred from the expanding vapor microlayer on a thin-film heater surface could be used, in principle, to drive electromechanical microdevices such as microactuators and... 

Diisopropyl methylphosphonate is slightly soluble in water (0.1—0.3 g/L at 25°) and has been demonstrated in laboratory studies to quickly diffuse between the surface microlayer into the water column after deposition as aerosols on fresh water (Van Voris et al. 1987). The solubility of diisopropyl methylphosphonate was 80 g/L (8%) and remained in solution even when the temperature was lowered to freezing (Bucci et al. 1997). In addition, there was no significant loss of diisopropyl methylphosphonate from the water column to the atmosphere, in either the presence or absence of a light wind over the water surface. Human exposure resulting from the vaporization of diisopropyl methylphosphonate from surface water is considered insignificant (EPA 1989). 

Evaporation-of-microlayer theory. A later hypothesis for the mechanism of nucleate boiling considers the vaporization of a micro layer of water underneath the bubble. This was first suggested by Moore and Mesler (1961), who measured... 

Figure 2.13 A newly formed vapor bubble illustrating an evaporating liquid microlayer. 

Readers should note that in Section 2.2.5.5, the term microlayer is used for the liquid sublayer beneath a single bubble. The macrolayer here includes a liquid sublayer and vapor stems. It is the same layer as shown in Figure 5.21. 

An improved CHF model for low-quality flow The Weisman-Pei model was later improved by employing a mechanistic CHF model developed by Lee and Mu-dawwar (1988) based on the Helmholtz instability at the microlayer-vapor interface as a trigger condition for microlayer dryout (Fig. 5.21). The CHF can be expressed by the following equation due to the energy conservation of the microlayer (Lin et al. 1989) ... 

KofTman, L. D., and M. S. Plesset, 1983, Experimental Observation of the Microlayer in Vapor Bubble Growth on a Heated Surface, Trans. ASME, J. Heat Transfer 105 625-632. (2)... 

For very low pressures (where there is a very large change of specific volume between the liquid and vapor states), bubble growth may be controlled by microlayer evaporation this situation has been investigated in detail by Cooper and Lloyd [48] and van Stralen et al. [49], van Stralen et al. [49] proposed the following expression for bubble radius as a function of time ... 

Latent heat transport. Here, the vapor being transported from the surface into the bulk fluid transports heat from the surface in the form of latent heat. This process is particularly important when heat fluxes are high. It may also play a very important role when the situation is such as to promote microlayer evaporation (e.g., at very low pressures). 

As discussed above, SVOCs are removed from the atmosphere and transported to the waters by precipitation scavenging of atmospheric vapors and particles, which are incorporated into the rain within or below the clouds. After SVOCs are deposited into the bulk seawater, partitioning in water column can affect the distribution of pollutants between the dissolved aqueous and the solid phases and eventually impact the fate of these compounds in oceans (Luo et al. 2004). In addition, air-sea exchange can make SVOCs diffuse across the air-sea interface however, the sea surface microlayer (SML), a unique compartment at the air-sea boundary defined operationally as the upper millimeter (1-1,000 pm)... 

This coextrusion techniqne has been applied to the fabrication of breathable films, using polyethylene oxide and polyolefin fiUed with CaC03. As the layer thickness decreased, the water vapor transmission rate changed dramatically due to changes from a continuous to discontinuous layer structure. Microlayer extrusion of a number of polymers has been accomphshed, including combinations of high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE), ethylene-styrene copolymers and low-den-... 

Correlations for Boiling Heat Transfer Nucleate boiling is a complex phenomenon. Several mechanisms have been proposed to explain the boiling process, such as latent heat transport, microconvection, vapor-liquid exchange, wake flow, enhanced convection, and microlayer evaporation, details of which can be found in Ginoux (1978). 

---