EP0609140A1 - Process and plant for making snow - Google Patents

Abstract

The subject of the invention is a process and an installation for producing snow in a closed circuit. This process consists in blowing air, using a turbine (4), into a tunnel including an element (5) for cooling the air, an element (6) for relative reheating of the air, one or more snow cannons (7a, 7b) and a chamber (2) for depositing the snow. This method and the corresponding installation can be used for testing the behaviour of materials in a snowy atmosphere. <IMAGE>

Description

The present invention relates to a method and an installation for producing snow in an essentially confined environment, that is to say isolated at least in part and preferably completely from the natural external atmosphere.

The problem of producing snow in an environment isolated from the atmosphere arises in particular for industrial or experimental purposes. It is indeed desirable to be able to study the behavior of various materials subjected to harsh climatic conditions and in particular to snow. However, if such tests can sometimes be carried out outside in particularly cold climates, it is not the same when the outside temperature is above zero degrees centigrade or when the required conditions, for example snow and wind at at the same time, are not obtained or properly mastered. You also cannot choose the quality of the snow produced (wet or dry).

It has already been proposed to produce snow production installations in a confined environment, in particular for studying the behavior of motor vehicles in the face of bad weather and their consequences, in particular penetration of snow through openings such as ventilation or air conditioning vents, snow deposit on the cooling system, in particular on the radiator, thermal shocks on certain parts normally brought to high temperature, loss of grip on the ground, abrasion effect on paint or other fragile parts of the vehicle.

A snow production installation of this type is described, for example, in US-A-4,798,331. This installation in the form of a loop or circuit essentially closed on itself successively comprises a zone for blowing a gaseous fluid, for example air, sucked in from the snow collection or deposition zone below, a zone for cooling said blown gaseous fluid, to bring its temperature below 0 ° C., a zone for injecting water, for example in the form of fine droplets, into the blown gaseous fluid and a zone for collecting or depositing the snow formed, said zones communicating the with each other, two by two, in the order of the preceding list which is also the direction of circulation of the gaseous fluid. The resulting gaseous fluid, at least partly freed from the snow which has settled in the collection zone, is taken up at least partly to return by suction to the blowing zone.

In the realization of the aforementioned patent, the air is taken upstream of the snow deposition chamber, but one could consider taking this air at the opposite end of the snow deposition chamber, especially if the installation was performed horizontally and not vertically as in the aforementioned patent.

Installations are known in particular for testing the behavior of vehicles with respect to snow driven by air at controlled speed, these installations comprising, in the order of the essential elements of a closed circuit, a zone blowing air, an area for cooling the flow of blown air, to bring its temperature below 0 ° C, for example below -2 ° C and in particular between -5 and -50 ° C where beyond, a zone for injecting water into the stream of blown and cooled air and a zone for depositing snow entrained by the stream of blown and cooled air. The air at least partially cleared of the snow, is at least partly re-aspirated from the deposition zone and returns to the blowing zone.

The authors of the present invention have found that this type of installation does not make it possible to carry out a satisfactory control of the quality of the snow. In particular, if you want to have dry snow, you must greatly reduce the amount of water injected, which lowers the production of snow; in the absence of this precaution the snow is wet and sticky which is not suitable for certain uses of this snow.

Also, to remedy these drawbacks, the subject of the invention is a process for producing snow in an essentially confined environment, in a snow collection zone, in which a gaseous fluid is circulated, from the snow collection zone. snow, successively through a cooling zone of said gaseous fluid, to bring its temperature below - 2 ° C., a zone of heating of said gaseous fluid, said reheating being positive but moderate so that the temperature of the gaseous fluid remains below 0 ° C after said reheating and a zone for injecting water into the gaseous fluid to form the snow collected in the snow collection zone, characterized in that at least part of the thermal energy taken from the fluid gas in the cooling zone is transferred to the gaseous fluid in the heating zone.

The invention also relates to an installation allowing the implementation of the above method. This installation successively comprises means for blowing a gaseous fluid, means for cooling said gaseous fluid, means for reheating said gaseous fluid, means for injecting water spray and means for collecting snow, said means being connected two by two to each other in the order of the preceding enumeration by conduits allowing the passage of gaseous fluids and arranged to form a continuous circuit closed on itself.

According to a preferred embodiment, the installation further comprises means for circulating in a loop a refrigerant successively in said cooling means and said reheating means, means for recompressing said refrigerant between the outlet of the cooling means and the inlet of the reheating means and means for expanding said refrigerant between the outlet of the reheating means and the inlet of the cooling means.

According to another embodiment, the installation comprises means for circulating in loop a first heat transfer fluid successively in the cooling means and in first heat exchange means and means for circulating in loop a second heat transfer fluid successively in the reheating means and in second heat exchange means and means for passing a refrigerant in a loop successively in said first and second heat exchange means under conditions making it possible to take thermal energy on the first heat transfer fluid and to transfer at least part of this thermal energy to the second heat transfer fluid.

The invention will be described in more detail below with reference to air which is the preferred gaseous fluid. For example, if the air temperature after cooling is between -5 ° C and -50 ° C, reheating may raise the air temperature by minus 2 ° C provided that the temperature of the heated air remains below -2 ° C and preferably below -4 ° C. Preferably, it will be cooled to a temperature T1 between -8 ° and -20 ° C and it will be reheated by at least 3 ° C, preferably by at least 5 ° C to obtain a temperature T2 greater than T1 and located at preferably between -5 ° and -12 ° C.

By operating according to the above improvement, it is possible to obtain non-sticky or slightly sticky "dry" snow with higher productivity than according to the known technique.

The installation can be arranged vertically or obliquely, but it is preferred to arrange the various areas above in the same horizontal plane.

In a preferred embodiment, there is an indirect contact cooling exchanger in the cooling zone and an indirect contact heating exchanger in the heating zone and a vaporizable refrigerant is circulated successively in a closed circuit in these two exchangers. . Preferably the fluid evaporates at least partly in the exchanger of the cooling zone and condenses at least partly in the exchanger of the reheating zone, which causes the cooling and the heating of the air respectively. circulating on the opposite face of the exchanger considered. Condensation can be completed, if desired, in another exchanger arranged in series or in parallel with the exchanger of the heating zone and exchanging heat for example with the atmosphere. The operating mode is preferably "compression", that is to say that the refrigerant at least partly condensed at relatively high pressure. high in the heating exchanger is expanded and evaporated at least in part at lower pressure, therefore at relatively low pressure, in the cooling exchanger; the resulting vapor is at least partially recompressed, then at least part of the resulting compressed vapor passes through the reheating exchanger where it condenses, at least in part.

According to another embodiment, the operating mode is absorption, using for example an ammonia circuit.

Without wishing to be limited in any way by a theory explaining the advantages obtained, it is believed that the air which has passed through the cooling zone is completely, or very strongly saturated with water vapor and is relatively unfit for the production of snow other only wet snow, while the air which was initially rather strongly cooled and which left water in the form of frost in the cooling zone, then was heated outside the aforementioned icing zone in accordance to the invention is undersaturated with water vapor, which makes it more suitable for the production of "dry" snow and this in a relatively higher amount.

Thus, for example, air saturated with water vapor at -12 ° C and then reheated to -4 ° C without any new water supply is only more than 50% saturated.

It is preferred in the invention that the air, after reheating, is only saturated at 20 - 90%, preferably 30 - 80%.

For example, while in a conventional type installation, the air was cooled to -5 ° C before snow production, it can according to the invention be first cooled to, for example -12 ° C, leaving frost on the exchanger and leaving this exchanger saturated at almost 100%. It can then be reheated, in the absence of water supply, to -5 ° C, which will lower its percentage of water vapor saturation to, for example, 70%.

If the preferred process of heat transfer between the cooling and reheating exchangers is implemented and thanks to the energy savings which it entails, the additional energy consumption due to the initial lowering of temperature is greater in the invention is fairly largely compensated and therefore remains low compared to the significant gain in productivity and / or quality of snow obtained.

The elements of the installation other than the cooling / heating couple can be of the conventional type and therefore do not require a detailed description. The heat exchangers themselves can be of any type, for example plate or tubular exchangers.

The water spraying members are of the conventional type and for example of the type known as a "snow cannon". Water can be injected alone or as a spray into an auxiliary air stream. One can also "seed" using small snow or ice crystals, according to a known technique.

The speed of the blown air (or other gas) can be chosen at will, for example from 1 to 30 m / s or more, preferably from 5 to 20 m / s; the air can for example be in a homogeneous or pulsed or turbulent vein.

The installation, and this is one of its many advantages, can be easily modified to operate occasionally in conditions outside the invention, for example to form freezing rain or even to operate at temperatures above 0 ° C. . In the latter case, the exchangers are not used or are on the contrary traversed by a heating fluid.

Although the invention finds a preferred application in the automotive field, the installation can be used to test the resistance to snow of packaging materials, clothing, power lines, water, gas or petroleum, this list is not exhaustive.

As an embodiment, the installation was used by cooling the blown air to 10 m / s (circulating in a loop) at -15 ° C, by heating it to -7 ° C, by injecting a fine mist water sprayed at + 2 ° C, driven by an auxiliary air stream at -20 ° C under pressure of 40 bars. A height of 0.2 m of dry snow was collected in 1 hour in the snow deposit chamber. The refrigeration plant operated with R - 22 using the cooling exchanger as an evaporator.

The condensation of R - 22 took place partly in the heating exchanger and partly in an exchanger with the outside air.

Figures 1 and 2 attached show two embodiments of the invention.

According to FIG. 1, the installation takes the form of a closed-loop tunnel 1. The tunnel comprises the snow-receiving chamber 2 where, for example, a motor vehicle 3, a blowing turbine 4 has been placed , an air cooling exchanger battery 5, a heating exchanger battery 6 and snow cannons 7a and 7b. The thermal installation comprises a compressor 8 for the fluid vapor coming from the cooling exchanger 5. The compressed fluid is condensed at least in part in the heating exchanger 6 and, for the rest, in the exchanger 9 which is advantageously placed outside and is cooled either by water or by atmospheric air. After passing through the exchangers 6 and 9, the fluid is in the condensed state. It passes through the regulator 10, of static or dynamic type, to join the exchanger 5 where it receives heat from the air blown by the turbine of the ventilation 4, causing the air to cool.

In FIG. 2, only part of FIG. 1 has been repeated, that which includes the turbine 4 and the exchangers 5 and 6. The refrigerant circuit is different because the fluid which undergoes the compression / expansion cycle does not pass not in exchangers 5 and 6; using two separate circuits of an auxiliary heat transfer fluid of any type, adapted to the chosen temperature range, for passage through each of these exchangers, the fluid not necessarily being the same for each of the circuits. It is not useful for this auxiliary fluid to undergo a change of state, it may therefore remain gaseous or preferably liquid on each of the circuits.

The refrigerating agent proper which undergoes changes in liquid / vapor state, passes through the evaporator 11, the compressor 12, the condensers in parallel 13 and 14 and the pressure reducer 15 and the pipes connecting these devices, namely 16 to 21 The cooling circuit of the exchanger 5 comprises only the exchangers 5 and 11 and the lines 22 and 23 with one or more pumps, for example 24 and 25; it is traversed by a first auxiliary heat transfer fluid. The other auxiliary heat transfer fluid passes through the condensation exchanger 13 and the reheating exchanger 6 as well as the connecting pipes 26 and 27 passing through one or more pumps (not shown).

Two condensers in parallel 13 and 14 have been shown, although the condenser 14 is not entirely essential for the invention. The heat received in this condenser is transmitted to an auxiliary fluid which discharges it into the cooling tower 28 passing through the pump 29 and the lines 30 and 31.

As an example of auxiliary fluids, mention may be made of Dowtherm and Gilotherm 12 (registered trademarks).

It is understood that the above-mentioned installations can be widely modified without departing from the scope of the invention. Thus, the heat transfer fluid circuit of FIG. 1 can include the exchangers 6 and 9 arranged in series, or use only the exchanger 6. Similarly, this circuit can be of several stages or in cascade. Specialists in refrigeration techniques may consider many obvious modifications. Likewise, it is possible to operate with a partially looped tunnel 1 open by recycling only part of the air and supplementing with fresh air.

Claims (10)

Method of producing snow in an essentially confined environment, in a snow collection zone, in which a gaseous fluid is circulated, from the snow collection zone, successively through a cooling zone of said gaseous fluid, to bring its temperature below -2 ° C, a zone for reheating said gaseous fluid, said reheating being positive but moderate so that the temperature of the gaseous fluid remains below 0 ° C after said reheating and a zone for injecting water in the gaseous fluid to form the snow collected in the snow collection zone, characterized in that at least part of the thermal energy taken from the gaseous fluid in the cooling zone is transferred to the gaseous fluid in the zone reheating. Method according to claim 1, in which the gaseous fluid is air and the temperature T1 of this air is between -5 ° C and -50 ° C after cooling and the temperature T2 of this air is at most equal to -2 ° C after reheating, while being greater than T1 by at least 2 ° C. Method according to claim 1 or 2, in which T1 is between -8 and -20 ° C and T2 between -5 and -12 ° C, with T2 greater than T1 by at least 3 ° C. Method according to any one of Claims 1 to 3, in which the zones of the circuit are arranged in the same horizontal plane. Process according to any one of Claims 1 to 4, in which the same vaporizable refrigerant provides cooling in the region of cooling and reheating in the reheating zone. Process according to Claim 5, in which the refrigerant is evaporated at least in part in the cooling zone under a relatively low pressure, then the resulting vapor is at least partially recompressed, at least part of it is sent into the region of reheating where it condenses at least in part under a relatively high pressure, the resulting condensate being returned after expansion to the cooling zone to reconstitute the refrigerant there. Method according to any one of Claims 1 to 6, in which a first heat transfer fluid is circulated in a loop for the cooling of the gaseous fluid successively in the cooling zone and in a first heat exchange zone and a second heat transfer fluid for reheating the gaseous fluid successively in the reheating zone and in a second heat exchange zone and a refrigerant is passed in a loop successively in the first heat exchange zone and in the second heat exchange zone heat in conditions where the refrigerant takes thermal energy from the first heat transfer fluid to cool it and gives up at least part of the thermal energy taken from the second heat transfer fluid to heat it. Installation for implementing the method of claim 1, characterized in that it comprises, linked in pairs between them in the order indicated below by conduits allowing the passage of gaseous fluids and arranged in a continuous circuit at least in part closed on itself, successively, means for blowing a gaseous fluid (4), means for cooling said gaseous fluid (5), means for reheating said gaseous fluid (6), means for injecting water spray (7a and 7b) and snow collection means (2). Installation according to claim 8, further comprising means for looping a refrigerant through said cooling means (5) and said reheating means (6), means (8) for recompressing said refrigerant between the outlet of the cooling means and the inlet of the heating means and means (10) for relaxing said refrigerant between the outlet of the heating means and the inlet of the cooling means. Installation according to claim 8, further comprising means for looping a first heat transfer fluid in succession in the cooling means (5) and in first heat exchange means (11) and means for circulating in a loop a second heat transfer fluid successively in the heating means (6) and in second heat exchange means (13) and means for passing a refrigerant in a loop successively in said first and second heat exchange means in conditions making it possible to take thermal energy from the first heat transfer fluid and to transfer at least part of this thermal energy to the second heat transfer fluid.

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