AU594095B2 - Snowmaking gun - Google Patents

Description

A P/00/011 594095 Form PATENTS ACT 1952-1973 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Class: In. CI: 6 f V56186 Application Number: Lodged: ::,Complete Specification-Lodged: *0 Accepted: .99 9 9.

o Priority: 9 9 Related Art: ?ublished: Thisn C'nai h aine~lnrelts deiv.

Section 49 and is cret1 V *t Name of Applicant: Address of Applicant: Actual Inventor: TO BE COMPLETED BY APPLICAN AN2 OTCE1 WOOtNERA SNOW GUNS PTY LTD 4olcor of Pub1c 20 WELLS GARDENS, GRIFFITH, CANBERRA, ACT, 2603 GEORGE. HARCORT JENNINGS W L THOMSON ASSOCIATES, P 0 BOX 291, WODEN, ACT, 2606 Address 4ervice: Complete S-pecification for the invention entitbad: SNOWMAKING GUN he following statemeni, is a full description of this invention, Including the best method of perform-ing It known 'Note: The descriptioi~ is to be typed In double spacing, pica type face, in an area not exceeding 250 mm In depth and 160 mri~in width, on tough white paper of good quality end it is to be Inserted Inside this form.

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INTRODUCTION

This invention relates to snowmaking guns for use in producing skiable slopes in circumstances where nature has been somewhat less than accommodating. The invention also relates to method of making snow.

BACKGROUND

Thirty years ago the first compressed air snowmaking equipment was used to create a skiable slope. Since then snowmaking equipment has been steadily improved and there are now three basic types of snowmaking equipment: compressed air/water which makes snow over the widest range of weather conditions and is most efficient (when compared with the other types) in the higher ranges of snowmaking temperatures and humidities, and again when the temperatures become very low, fan guns (cannons) which use a reduced compressed airflow for the creation of ice nucleii (5-10% airflow of a comparable waterflow of a compressed 15 air/water gun) and the airless snowmakers of the S.M.I. pattern (the most energy efficient of all snowmaking equipment when the conditions are suitable).

In the U.S.A. up to the late 70's it was believed that snowmaking was only possible in below freezing temperatures i.e. snow was formed by sensible heat cooling. The original patents (over 35 years ago) referred to a gun with separate nozzles for compressed air and water.

These were of low efficiency, i.e. high compressed air useage for a low water flow. Since then there has been a number of inventions to try to improve the efficiency. The majority of these snowmakers have a comparatively large round, tubular final discharge orifice (10-40mm in diameter); sometimes a number of guns or nozzles were placed near each other to improve the capacity ad throw of the snowstream. Others have used a linear slot orifice. May have also used internal orifice(s) to improve mixing and performance. These internal orifice(s) usually cause an internal compressed air expansion, leaving less potential for the cooling expansion at the final orifice.

During theoretical considerations in the late 60's, I discovered that the process to make snow economically was the use of latent heat of evaporation to remove the heat released changing watt' to ice in a small water droplet. This indicated that snowcould theoreticalYy be mad( at +120C if the humidity was low enough. Since that time i have madek snow at this temperatre with a relative humidity -2 6* .94 1 6 6 a it 6 t i r :I I: i 1 i ts ~u~;rtla~ir~lnr~ #'Aignature of Dgarant) (IMPORTANT-Cross out inapplicable words in the above Form.) SI t 14692/78- L C. J. THomaom, Commonwealth Govemment Paiter teJV 1 i l -4 J W% iMag 0 lo a at .09.

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of however the amount of snow produced was too small to be economic. My earliest nozzles made useful amounts of snow at when the relative humidity was below 12%. Development has now increased the temperature to +6 0 C at this humidity. Further theoretical considerations led to the calculation of the time needed to remove the "heat of fusion" and in turn the maximum diameter of water droplet same time to fall). This could be estimated for each temperature/relative humidity. The use of comparatively large discharge orifices produces a wide range of droplet diameters i.e.

some extremely fine nist that freeze very quickly to nucleate the production droplets and some in between that absorb nucleii but being slow to settle may be blown away. This is the pattern most types of compressed air snowmakers operate on today. With a wide droplet size range this "blow away" can become over 30% when operating above -3 0 C temperatures and/or when the relative humidity is about Australian weather dictates snowmaking equipment must be developed to operate in these "high" temperature and humidity conditions.

I found that to control the range of droplet diameters a narrow slot (0.2mm to 3mm oide) was best. When this was made into an annular slot it had the advantage of promoting the throw from the gun and improving the mixing of the surrounding air to promote the evaporative cooling. Another result noticed, was the evenness of the size/density of the deposited "snow" particles along the deposition path; this is a characteristic not matched by other compressed air 25 snowmaking guns which have a wide range of droplet sizes thus causing a large difference in crystal sizes and deposited snow densities. It appears that the mechanism of the formation of ice nucleii is different; observations indicate the nozzles of this invention form nucl(ii in the droplet rather than separately. For this the conditioniig zone inside the nozzle seems to be very important, as is thsattention to minimising the friction in the air and air/water streams by providing adequately sized smooth sided passages, This ensures the maximum coolin~g expansion occurs near Sthe discharge slot in a droplet ready to form its nucleii internally.

More recently I have found the following interesting facts Operating Ranges Comprssed ati pressures successfully tested so far 200Kpa (30psi) -3i I C tLc, k B t I (r r2: i

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f d I ii to 1,000 Kpa (150 psi). The higher the pressure, the higher the waterflow for the same produced snow quality and the higher the efficiency.

Ambient Air Temperatures 4 snow has been made from +6 deg C (+12 deg C 6% RH snow was produced but in uneconomic quan.tities) down to i28 deg C (satisfactory operation should occur at temperatures lower than r28 deg C not had conditions lower than *28 deg C to test operations).

Humidity at temperatures below *2 deg C relative humidities up to 98% successful snowmaking has been proven.

deg C up to 90% R.H.

+I deg C up to 82% R.H.

0 deg C up to 72% R.H.

Lower humidities increase production rate.

Test of Tower Gun in comparison with a ground gun with identical nozzles; Tower delivered 38% more water with less compressed air, i.e. tower operating at 41% higher efficiency when compared with ground mount at '3 deg C 98% R.H.

According to this invention, there is provided a snowmaking gun comprising inlet means for water, inlet means for compressed air, passage means enabling said i air and water to mix, said passage means leading to i, outlet means comprising a nozzle, said nozzle having a tubular outer housing with an internal member axially 4 4 4 i 4) .Cy y i arranged in said housing, extending to said orifice, whereby to form an annular passage between said member and to occlude said orifice to restrict exit of air/water mixture to the forms of an annular stream, wherein the annular passage formed between said internal member and said housing has a substantially constant cross*sectional area being 2 to 17 times greater than the free cross-sectional area of said orifice.

The desirable elements of snowmaking guns of chis invention are:* 1. The comparatively narrow 1.2 4.0 mm wide) circular discharge slot to promote an even droplet size suitable for the prevailing conditions and the promoting of the mixing of ambient air close to the gun. The slot width is to a degree determined by the desired snow particle size e.g. 1.5 to 4 mm for bulk snow production and 0.2 to 1 mm for fan gun (cannon) nucleation. The produced snow size can also be determined by changes in water flow rate for a given nozzle variation in the produced snow quality/density to tailor the snow for the different uses.

2. For a given gun size (and weight), the annular X nozzle gives a maximum capacity. The double stream ;i from the nozzle improves the t 4a 1- I- iii: I .ii I 3UIIUI UICI~ IIII~ IICLI 0* 0 0 0*0 O 90 .9 0 0 0 00 tcr throw characteristics giving greater distance and improved ability to handle adverse winds.

3. The upstream cross-sectional area of any passageway carrying compressed air or compressed air/water mix is preferably at least twice the cross-sectional area of the annular discharge slot:i.e. 3 to 6 times is desired for bulk snow production; at 2 times, the produced snow particles showed a significant expansion before the discharge slot, reducing efficiency. An area up to 17.4 times the discharge slot has been used successfully on nucleating nozzles; however this area on bulk snowmaking nozzles would make the gun both heavy and very bulky.

4. The nozzle design ensures that a maximum expansion takes place in the region of the discharge slot, giving the sharpest temperature drop and a minimum time to absorb heat from other parts of the gun.

15 Thus the compressed air energy is used to maximum effect.

5. Immediately before the discharge slot is a water droplet conditioning zone of a length preferably 30-400 times the slot width (typically 40-200mm long). This prepared the droplet for nucleation, evening and smoothing the air/water flows for an even discharge.

6. The arrangement of the gun of this invention attempts to minimise internal heat transfer. At high production rates heat transfer to the stream would reduce nucleation rates and hence reduce efficiency.

Probably a considerable heat transfer is occuring during a wide range of flows in all the types of air/water guns I have seen. Their extended expansions (long tubular orifice and thick section walls) and/or partial internal expansions would allow such a transfer of heat to the stream, which can only reduce efficiency.

7. The gun of this invention is conceived for use on towers as well as on ground mounts. The extra height of fall from a tower means the droplet size can be increased to maintain the same time to fall to ground, thus increasing production 10-30% for the same compressed air useage. The compressed air pipe is placed inside the water pipe to keep the condensate in the air from freezing on its way to the nozzle. This placement of the compressed air pipe inside the water line is public knowledge: e.g. Mt. Brighton, Larchmont (now have used this principle on their range of 1 i Frl tower mounted air/water guns.

This invention uses various methods of water addition to the compressed air flow:- for examples see drawing sheets 5-7. Some early designs were prone to water pulsing and widening of the droplet size range. Also the air/water ratios were higher than in the later designs.

NOZZLE AND AIR/WATER MIXER CONSTRUCTION: Sheets 1 to 3 of the accompanying drawings show preferred annular nozzle constructions for the gun of this invention. In sheet one is shown one of the more preferred constructions the annular nozzle is made up from an outside tube and a central cast (solid) aluminium core (hardened) held in place by three spiders. DiPnsif3g ar r. h'n on the Sheet 2 shows a similar construction but the aluminium core is hollow with welded ends. Ag.i, imenion uz ~Sheet 3 shows a nozzle having a machined solid aluminium core held in position by welded tapered spiders, Nte t!he diJerrsei- a he .wPei- ithe pe Sheet 4 shows "nucleating" type nozzles with an aluminium solid machined centre held in the outer tube by an end bolt (for side entry of air/water) or by a 3 leg spider (for end entry of air/water).

woo. Again the dimensions for the nozzle types are as shown in the drawing pp and tables.

Sheet 5 shows air/water mixing arrangements prior to feeding to the annular nozzle.

Sheet 6 shows some air/water mixing arrangements of an earlier type than on sheet Sheet 7 shows an alternative arrangement for air/water mixing.

Sheet 8 shows general arrangements for tower and ground guns. It is to be noted that the aluminium construction is desirable since it is relatively corrosion free, light and easy to manufacture. s Thus copper or stainless steel could be used but would be more expensive. However, any suitable material of construction could be used instead, although metal is preferred.

It is emphasised that this invention is to be given a broad connotation and is not restricted to the specific embodiments hereinbefore described.

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Claims (4)

1. A snowmaking gun comprising inlet means for water, inlet means for compressed air, passage means enabling said air and water to mix, said passage means leading to outlet means comprising a nozzle, said nozzle having a tubular outer housing with an internal member axially arranged in said housing, extending to said orifice, whereby to form an annular passage between said member and to occlude said orifice to restrict exit of air/water mixture to the forms of an annular stream, wherein the annular passage formed between said internal member and said housing has a substantially constant crossesectional area being 2 to 17 times greater than the free crossisectional area of said orifice.

2. A snowmaking gun as claimed in claim 1 wherein said nozzle is composed of aluminium.

3. A snowmaking gun as claimed in claim 1 substantially as hereinbefore described and illustrated with respect to the drawings.

4. A method of snowmaking using the snowmaking gun as claimed in claims 1 to 3 substantially as hereinbefore described. WOOMERA SNOW GUNS PTY LTD '4 DATED: 12 DEC 89 E NT7,4 l