Appearance Of Vapor Research Articles

High-pressure double stage homogenization processes: Influences of plant setup on oil droplet size

High pressure homogenization is widely used to produce small droplets in liquid products. The use of two homogenization units (e.g. orifices) in series thereby is generally accepted as increasing homogenization efficiency, even when the mechanism is still not fully understood yet. It is shown that for a single stage orifice operated at a given overhead pressure, the drop size decreases with increasing backpressure first until a minimum is reached and then increases due to the lower total pressure drop due to the lower flow velocity and driving force. Simultaneously observation showed that backpressure suppresses cavitation. This paper focuses on the question whether the droplets break up at the first or second orifice. A process plant is designed enabling us to investigate droplet breakup in o/w-emulsions at each orifice separately. In subsequent experiments the second orifice was substituted by a pressure vessel to eliminate the influence of the second orifice entirely. Our research reveals that droplets are broken up only in the first orifice. The second orifice delivers back-pressure being responsible for a change in the cavitation pattern found after the first orifice. The smallest oil droplet sizes are reached at a back-pressure of ~30% of the inlet pressure, a value being in consensus to former experimental studies. A discussion of the droplet breakup with regard to the mean specific energy input Ev at the first orifice is given. It depicts that a change in flow pattern, especially the appearance of vapor after the first orifice has a huge impact on energy transfer efficiency. A prediction of resulting droplet sizes as result of pressure drop in the first stage is only possible for constant Th numbers.

Explosive loading of lead hemispherical liners

This paper documents results of a combined analytical/experimental program to study the behavior of lead hemispheres of various thicknesses subjected to explosive shock loading. Previous studies of collapse and jetting of lead structures indicated that, due to the low melting temperature of lead, significant amounts of vapor were present in the jet. However, its high density, ready availability and low cost make lead an attractive material for industrial and military applications. Hemispherical lead liners of three different thicknesses were fabricated into aluminum confined cavity charges using OCTOL high explosive to drive the liners. Analysis of flash radiographs of the formation and jetting process indicated a gradual transition from an apparent liquid-vapor jet for the smallest wall thickness to a liquid-solid jet for the largest thickness. This apparent phase transition of the lead liners through a region of decreasing vapor lead to an analysis of the phenomena with the two-dimensional HULL code, a finite-difference Eulerian code for computations of hydrodynamic and elastic-plastic phenomena. Good correlation (8%) was obtained between experimentally determined and computed jet characteristics, thus permitting inferences to be drawn regarding the effects of material properties and strain rates on the response of lead to shock loading. Additional computations were made with HULL for copper hemispherical liners (for which more extensive experimental data was available) and these were compared with results from HELP, another Eulerian code. The EPIC code was also used to predict the geometric characteristics and velocities of the jets from the lead liners. On the whole, good agreement with experiments was obtained from all codes indicating that existing two- and three-dimensional codes may be valuable tools for the study of explosive forming problems. In addition, the temperature profiles of the jets from the lead liners are in general agreement with the quality of the flash radiographs (i.e. appearance of vapor) and with experimental measurements of the jet surface temperature.

The seasonal and global behavior of water vapor in the Mars atmosphere: Complete global results of the Viking Atmospheric Water Detector Experiment

The water vapor content of the Mars atmosphere was measured from the Viking Orbiter Mars Atmospheric Water Detectors (MAWD) for a period of more than 1 Martian year, from June 1976 through April 1979. Results are presented in the form of global maps of column abundance for 24 periods throughout each Mars year. The data reduction incorporates spatial and seasonal variations in surface pressure and supplements earlier published versions of less complete data. Column abundances vary between 0 and about 100 precipitable microns (pr μm), depending on location and season, while the entire global abundance varies seasonally between an equivalent of about 1 and 2 km3 of ice. The first appearance of vapor at nonpolar latitudes as northern summer approaches and the drop in abundance at mid‐latitudes as summer ends both strongly imply the existence of a seasonal reservoir for water within the regolith. There appear to be no net annual sources away from the poles that contribute significant amounts of water. However, the strong annual gradient of vapor from north to south implies a net annual flow of vapor toward the south. This southward flow may be balanced by a northward flow during the global dust storms, by transport in the form of clouds or adsorbed onto dust grains, or during other years. The perenially cold nature of the south polar residual cap, along with the relatively large summertime vapor abundances over the cap, implies a net annual condensation of vapor onto the cap. Comparison with earlier (Earth‐based) observations of vapor in the south during the local summer indicates that all of the seasonal CO2 cap may sublime away in some years to reveal the water ice cap which must lie underneath, with corresponding large southern summer vapor abundances. The global distribution of the annual average abundance of vapor correlates well with Martian topography, as might be expected for a uniform constant atmospheric mixing ratio. If this topographic effect is divided out, the resulting residual map correlates well with maps of surface albedo and thermal inertia; this correlation may be related to the control exerted by the surface and subsurface temperatures on the adsorption/desorption process and on the atmospheric temperature profile and, hence, the vapor holding capacity of the atmosphere.

Drilling porthole glass with a diamond tool

Plant have carried out some tests to determine the parameters of the process of drilling glass with an annular diamond tool of >60 mm diameter. The studies were carried out on a 2A125 drilling lathe equipped with a measuring device, a liquid-cooling system in the cavity of the drill, and a device for applying the drill at a constant force. Glasses 17 and 28 mm thick which had an ultimate compressive strength (in the dry state) of 80.5-114.9 MPa were drilled using a serially produced annular diamond drill and experimental specimens of drills made by the Kiev Institute of Ultrahard Materials. The characteristics of the drills are given in Table I and the experimental results in Figs. 1-3. The normal working of the drill was taken as the acceptable cutting regime. In regimes going beyond the acceptable, there was an increase in vibration, the appearance of vapor from the cooling liquid (water), which no longer reached the cutting zone, and destruction of the glass which was being treated. An increase in power requirements with an increase in the axial load in the case of all sizes of drills was characteristic when the drill was operated in all the permitted cutting regimes (Fig. I). The productivity of the drilling process with a higher axial load also increases to some limit after which it remains at the same level or decreases although the power requirements continue to increase. In the case of the 60-mm drill with a diamond granularity of 200/160 and the 100-mmdrill with a granularity of 400/315, the maximum productivity is reached within the acceptable cutting regimes (based on the strength of the glass); for the remaining tests the drill was outside this interval. The fact that the drilling productivity stops increasing with a further increase in the axial load is explained by the fact that the destroyed material cannot be displace d from the intergrain space (between the protruding diamond grains on the cutting edge of the drill).