Fluid sprinkling – spraying – and diffusing – Processes – Of weather control or modification
Reexamination Certificate
2002-08-10
2004-09-21
Evans, Robin O. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Processes
Of weather control or modification
C239S014200, C239S575000, C239SDIG002
Reexamination Certificate
active
06793148
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of snow-making. More particularly, it relates to improvements in methods and apparatus for producing man-made snow from water only, i.e., without the additional use of either compressed air or high-speed fans.
BACKGROUND OF THE INVENTION
Various methods and apparatus have been devised over the years for assisting Mother Nature in producing snow at ski resorts and the like. More recently, such snow-making methods and apparatus have even been used at water-treatment facilities for converting winter waste-water to snow which takes the place of a secondary treatment usually required for such water. To date, most man-made snow has resulted by suitably combining air and water under certain favorable conditions. Typically, man-made snow is produced by propelling a relatively fine spray of water particles into the air while cooling the water particles with a rush of turbulent air, as provided by either a source of compressed air or by a high-speed, motor-driven fan. Ideally, the air passing through the spray causes the temperature of the water particles to quickly fall below a critical temperature at which ice crystals (i.e. man-made snow) form from each particle. Whether or not such crystallization occurs, as well as the “quality” of such crystallization, depends on several factors. These factors include (i) water particle size, (ii) ambient atmospheric conditions (viz., temperature, relative humidity and wind speed), (iii) “hang-time” or flight-time of the particles before settling to earth, and (iv) the velocity of the turbulent cooling air passing through the water spray.
Water particle size is particularly relevant to the snow-making process since, from a physics standpoint, a relatively small particle (i.e., a particle having a relatively small mass and small surface area through which cooling can occur) can be more quickly cooled than a larger particle (with a correspondingly larger mass and surface area). Note, the surface area of the particle increases with the square of the particle's diameter. Particle size is determined by both the physical characteristics of the nozzle(s) used to produce the water spray, and the water pressure applied to such nozzles. Generally speaking, the smaller the diameter of the nozzle orifice through which water is projected, the smaller the median diameter of the water particles produced. On the other hand, the greater the water pressure applied to the orifice, the smaller the water particles produced. Ideally, the water particles created to produce man-made snow should be sufficiently small to facilitate a rapid conversion to ice crystals, but not be so small as to allow the particles to be either (a) wind-blown from the intended region of snow accumulation, or (b) evaporated in the ambient air, in which case the particles convert to water vapor rather than forming ice crystals.
Equally as important as particle size to snow-making are the ambient atmospheric conditions under which air and water particles are combined to produce snow. Of course, the colder and drier the ambient atmosphere, the easier it is for water particles to convert to ice crystals. Since water normally freezes (crystallizes) at a wet bulb temperature of 32° Fahrenheit (0° Centigrade), the closer the initial temperature of the propelled water particles to the freezing temperature, the faster the conversion from water particles to ice crystals. Further, the colder and drier the conditions, the better the quality of the snow deposit, assuming a dry, powdery snow is what is desired. Warm, wet conditions give rise to an undesirable, moisture-laden snow pack in which a large percentage of water particles have not been frozen.
Wind speed is relevant to the snow-making process due to its effect on a particle's “hang-time”, i.e., how long a particle stays airborne after being propelled into the air. Obviously, the longer a particle remains air-borne, the better its chance for attaining the temperature change required for crystallization. But a wind speed too high is detrimental to snow-making in that the snow deposit may not occur at the desired location. Particle hang-time also depends on (a) the water pressure applied to the water nozzle, the higher the pressure, the longer the hang-time, (b) the elevation of the water nozzle above ground level, and (c) the direction in which the water spray is directed relative to ground level. Usually, to enhance the hang-time of water particles, the snow-making apparatus is mounted atop a tower, typically measuring between 3 and 12 meters, and the water spray is directed upwardly from horizontal to provide for a relatively long particle flight time even on a still day.
Finally, the speed of the cooling air (provided by either a compressed air source or a rapidly rotating fan blade) passing through the water spray determines, in large part, the particle-to-crystal conversion efficiency. The turbulent cooling air operates to quickly transport thermal energy (via convection and evaporation) from the water particles, and the faster the air flow, the greater the number water particles converted to ice crystals, and the larger the size of water particle that can be converted.
It is well known that the production of ice crystals in a water spray can be dramatically enhanced by increasing, within the spray, the number of “nucleation site” (i.e., sub-micron and micron-sized particles) about which crystallization commonly occurs. It is well established that water particles containing a nucleation site (e.g. a dust particle or a small mineral particle in the water) will form an ice crystal more readily than water particles having no such site. Thus, it is common in the field of snow-making to introduce a relatively large number of nucleation sites into the water used to make snow. The introduction of nucleation sites can be effected by either (a) injecting the nucleation sites into the water supply prior to producing the water spray, or (b) injecting the nucleation sites into the water spray after the fact. With regard to the first approach, two commercially available products that operate, when added to a water supply, to supplement the nucleation sites in a water spray produced from such supply are Snomax® Snow Inducer (made and sold by York International), and Freezyme Snowmaker (made and sold by Samyang Genex). Both of these products comprise tiny microorganisms (dead) that are adapted to be mixed with water to form a concentrated suspension that can then be injected, in metered amounts, into the water supply as snow is being made.
As regards the second approach (noted above) of injecting nucleation sites into a water spray made from a water supply containing no artificial sites, reference is made to the commonly assigned U.S. Pat. No. 5,884,841 to Ratnik et al. This patent discloses a snow-making apparatus in which tiny, micron sized, particles of ice (nucleation sites) are injected into a bulk water spray by a plurality of external “nucleators”, i.e. nuclei-producing devices, that are positioned at equally-spaced locations outside the water spray, The bulk water spray itself is produced by one or more water nozzles, each having a single orifice or hole through which a flat or conical spray of water particles is produced. Each orifice is sized to produce a spray of water in which the median diameter of the water particles is preferably no greater than about 300 microns when a water pressure of about 500 pounds/inch
2
(PSI) or 170 Kg./cm
2
is applied. This translates to a nozzle hole diameter of about 0.11 inch (2.8 mm.). Note, recent developments of the bulk water nozzle used in this system have included the addition of up to twelve orifices per nozzle, such orifices being arranged in a circular pattern and oriented to direct their individual sprays of water particles in diverging directions to prevent their immediate interaction with each other (which would otherwise result in the formation of larger droplets). The individual orifices of this nozzle have been as small as 0
Evans Robin O.
Kurz, Esq. Warren W.
Ratnik Industries, Incorporated
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