A device for generating a jet of a medium comprising gas and liquid nitrogen

Abstract

The invention concerns a device (100) for generating a jet of a medium (M) comprising gas (G) and liquid nitrogen (LN), wherein the device comprises: an orifice (102) connected or connectable to a tank of liquid nitrogen; and one or more gas nozzles (101) connected or connectable to a source of pressurized gas, wherein the orifice (102) and the one or more gas nozzles (101) are directed in a substantially similar direction and wherein the one or more gas nozzles (101) at least partly surround the orifice (102) so that, when liquid nitrogen flows from the tank and out through the orifice (102) and gas is flowing from the gas source and out through the one or more gas nozzles (101), the liquid nitrogen is at least partly surrounded by the gas in the medium jet (M) that is expelled from the orifice (102) and the one or more gas nozzles (101). The invention also concerns a method for operating the device (100).

Description

[0001] P486870PC00

[0002] 1

[0003] A device for generating a jet of a medium comprising gas and liquid nitrogen

[0004] TECHNICAL FIELD

[0005] This invention relates to a device for generating a jet of a medium comprising gas and liquid nitrogen. The invention also relates to methods for operating the device, such as for cooling, firefighting and snow production purposes.

[0006] BACKGROUND OF THE INVENTION

[0007] Liquid nitrogen is in principle very useful for e.g. firefighting since it is inflammable and an efficient cooler if brought in direct contact with an object to be cooled. However, handling of liquid nitrogen is a challenge and there is a need for devices that in a reliable way can produce a flow of liquid nitrogen that also can be directed in an efficient way towards a target object.

[0008] SUMMARY OF THE INVENTION

[0009] The invention concerns a device for generating a jet of a medium comprising gas and liquid nitrogen, wherein the device comprises: an orifice connected or connectable to a tank of liquid nitrogen; and one or more gas nozzles connected or connectable to a source of pressurized gas, wherein the orifice and the one or more gas nozzles are directed in a substantially similar direction and wherein the one or more gas nozzles at least partly surround the orifice so that, when liquid nitrogen flows from the tank and out through the orifice and gas is flowing from the gas source and out through the one or more gas nozzles, the liquid nitrogen is at least partly surrounded by the gas in the medium jet that is expelled from the orifice and the one or more gas nozzles.

[0010] When operating a device of the above type, the pressurized gas forms a high-speed shielding tubular gas volume around the liquid nitrogen, i.e. the gas protects and transports the liquid nitrogen. The shielding gas keeps the liquid nitrogen together and prevents it, for at least some time, from moving through stationary air where it quickly loose speed and also splits intodroplets surrounded by evaporated nitrogen, which insulates the liquid nitrogen and makes it more difficult to bring the liquid nitrogen in direct contact with a target object. The device of the present disclosure creates a long-reaching jet containing a bulk of liquid nitrogen that more efficiently can be directed to and contacted with e.g. a heart of a fire. As described more in detail below, a medium jet conduit may be arranged downstream the gas nozzles and the orifice in order to both increase the flow rate, due to increased pressure from liquid nitrogen that to some extent evaporates in the jet, as well as to reach closer to the target object before the jet is expelled through some pipe end to the surroundings. The latter is useful both for coming closer with the pipe end to a position that otherwise is difficult to reach, for instance a fire that is difficult to approach due to extreme heat, or for reaching into a central region of some object that is on fire, such as a stack of sawdust.

[0011] Liquid nitrogen is especially useful as firefighting medium when water cannot be used, e.g. because it may lead to destruction of equipment. Besides firefighting, the device of this disclosure is useful also for cooling objects, such as an overheated generator or electric battery. Further, the device is useful in combination with a “snow gun” in snowmaking, in particular when the ambient temperature is not sufficiently low for normal snowmaking. The medium jet may be mixed with a stream of air and water droplets generated in a snowmaking machine.

[0012] What pressure to use for the pressurized gas depends on the intended application, the design and size of the gas nozzles, the pressure of the liquid nitrogen, etc. The gas pressure may be in the range 5-200 bar. In many applications, a gas pressure of 30 bar or above is suitable. The source of pressurized gas may be one or more gas tanks and / or compressors.

[0013] The liquid nitrogen may be supplied from a flask fluidly connected to the orifice. The flask can be pressurized by evaporating liquid nitrogen andcontrolled by a pressure relief valve set to e.g. 2 bar or, preferably, 5 bar or more. Another alternative is to pump the liquid nitrogen to the orifice.

[0014] The pressure of the gas is preferably higher than that of the liquid nitrogen to provide a useful medium jet.

[0015] The one or more gas nozzles may include one or more slits that extend circumferentially around (most of) the orifice or a plurality of regular holes / openings (such as circular holes) circumferentially distributed around the orifice. A combination of slits and regular holes is also possible. Circular holes are generally more easy to provide than holes with other shape. The size (width) of the nozzles may be variable, for instance by means of a movable plate, to adapt the nozzles to a particular application or a particular gas pressure.

[0016] In an embodiment, the one or more gas nozzles comprises a plurality of openings circumferentially distributed, preferably evenly distributed, around the orifice. Each of the openings may have a diameter of 0.1-5 mm, or 0.5-3 mm, or 1-2 mm. The number of such openings / holes may be 4-8. Even three (small) openings may be sufficient in certain applications. Higher number of openings may be provided to generate a more even distribution of the gas. However, around six openings is sufficient in many applications.

[0017] In an embodiment, the one or more gas nozzles are arranged to form a tubular volume of gas around the liquid nitrogen when liquid nitrogen flows from the tank and out through the orifice and gas is flowing from the gas source and out through the one or more gas nozzles. As noted above, this provides a gas shield around the liquid nitrogen that allows the liquid nitrogen to be “thrown” a longer distance than without such a gas shield. In some applications, the thickness of this gas shield is around 3-10 mm.In an embodiment, the one or more gas nozzles is / are located in a position that is substantially aligned with or upstream a position of the orifice with reference to a flow direction of the medium jet. That is, the gas nozzles are preferably not located downstream the orifice since this is may lead to turbulence and a poorer gas shield.

[0018] In an embodiment, the device comprises a medium jet conduit arranged to guide the gas and the medium jet in a downstream direction from the one or more gas nozzles. The gas nozzles may be located around 0-50 mm or around 10-40 mm upstream the orifice, or the nozzles may be located a distance upstream the orifice corresponding to around 0-100% or around 20-80% of a diameter of the medium jet conduit. That is, the liquid nitrogen is to be introduced into the medium jet conduit at or slightly downstream the position at which the gas is to be introduced into the medium jet conduit.

[0019] In an embodiment, the one or more gas nozzles is / are located upstream the orifice wherein a length of the medium jet conduit is such that it extends in the downstream direction at least to the orifice.

[0020] In an embodiment, a length of the medium jet conduit is such that it extends at least 50 mm, or at least a distance corresponding to twice its diameter, from the orifice in the downstream direction. The medium jet conduit may be much longer, for instance several meters or 100 times its diameter. As noted above, the medium jet conduit may be used to increase medium flow rate and to reach closer to a target object with the conduit end. Which length to chose for the medium jet conduit may depend on the intended application, the pressure of the gas, the mass flow rate of liquid nitrogen, etc. The device may comprise one or more connectable medium jet conduit sections so that the total length may be adapted to a particular situation.

[0021] In an embodiment, the orifice is arranged at an end section of an LN (liquid nitrogen) conduit connected or connectable to the tank of liquid nitrogen.In an embodiment, the device comprises a gas conduit connected or connectable to the source of pressurized gas and wherein the gas conduit is arranged to supply gas to the one or more gas nozzles. A gas blocking member provided with one or more through holes forming the one or more gas nozzles may be arranged in the gas conduit so as to block the flow of gas besides the gas flowing through the through holes.

[0022] In an embodiment, the LN conduit extends inside the gas conduit, at least in a region immediately upstream of the one or more gas nozzles. For instance, the gas conduit may have a larger diameter than the LN conduit and form a bend with a straight section downstream the bend. A straight LN conduit may then be arranged to extend through a wall of the gas conduit in the bend and extend inside the straight section of the gas conduit at a central position thereof. The LN conduit may extend through the gas blocking member so as to be circumferentially surround by the through holes arranged in the gas blocking member.

[0023] In an embodiment, the device comprises a source of pressurized gas fluidly connected to the one or more gas nozzles. The source may be a gas tank, a compressor, or a connection to an external gas supply line.

[0024] In an embodiment, the gas is nitrogen, carbon dioxide or air. Nitrogen and carbon dioxide are useful for firefighting and cooling, whereas air is a better choice (e.g. due to costs) for shielding and driving the medium jet in snowmaking applications.

[0025] In an embodiment, the device comprises a tank of liquid nitrogen fluidly connected to the orifice.The invention also concerns a method for operating a device of the above type, the method comprising: supplying liquid nitrogen to the orifice; and supplying pressurized gas to the one or more gas nozzles.

[0026] In an embodiment, a pressure of the pressurized gas supplied to the one or more gas nozzles is higher than a pressure of liquid nitrogen supplied to the orifice.

[0027] In an embodiment, the pressurized gas is nitrogen or carbon dioxide, wherein the method further comprises: directing the medium jet towards an object for cooling the object and / or extinguishing a fire.

[0028] In an embodiment, the pressurized gas is air, wherein the method further comprises: mixing the medium jet with a flow comprising air and water droplets so as to produce snow.

[0029] BRIEF DESCRIPTION OF DRAWINGS

[0030] In the description of the invention given below reference is made to the following figure, in which:

[0031] Figure 1 shows a schematic sideview of a first example of an embodiment of a device according to this disclosure.

[0032] Figure 2 shows an upstream view (front view) of the embodiment according to figure 1.

[0033] Figure 3 illustrates schematically how a medium jet may behave when expelled from the embodiment according to figure 1.

[0034] Figure 4 shows a schematic sideview of a second example of an embodiment of a device according to this disclosure, wherein the device is provided with an extended medium jet conduit.

[0035] DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0036] As shown in figures 1 and 2, the exemplified device 100 for generating a jet of a medium M comprising gas G and liquid nitrogen (LN) comprises a gasconduit 103, a plurality of gas nozzles 101 and an LN conduit 104 provided with an orifice 102. The orifice 102 is, via the LN conduit 104, fluidly connected to a tank of liquid nitrogen (not shown). The gas nozzles 101 are, via the gas conduit 103, connected a source of pressurized gas (not shown).

[0037] The orifice 102 and the gas nozzles 101 are directed in a substantially similar direction (to the right in figure 1) and the gas nozzles 101 (in this example six nozzles, see figure 2) surround the orifice 102 so that, when liquid nitrogen flows from the tank and out through the orifice 102 and gas is flowing from the gas source and out through the one or more gas nozzles 101, the liquid nitrogen is surrounded by the gas in the medium jet M that is expelled from the orifice 102 and the gas nozzles 101.

[0038] The gas nozzles 101 are provided as through holes in a gas blocking member located in the gas conduit 103, i.e. the flow of gas is blocked besides the gas flowing through the through holes / gas nozzles.

[0039] The gas conduit 103 has a larger diameter than the LN conduit 104 and the gas conduit 103 forms a bend with a straight section downstream the bend, i.e. towards the gas nozzles 101. The LN conduit 104 is straight and is arranged to extend through a wall of the gas conduit 103 in the bend and to further extend inside the straight section of the gas conduit 103 at a central position thereof in a direction towards the gas nozzles 101. The LN conduit 104 extends further through the gas blocking member so as to be circumferentially surrounded by the through holes / gas nozzles 101 arranged in the gas blocking member.

[0040] In an example, the gas conduit 103 has a circular cross section with an inner diameter of 30 mm, the LN conduit 104 has an outer diameter of 15 mm, and each of the through holes / gas nozzles 101 has a circular cross section with a diameter of 1.5 mm. Further, the gas pressure is 70 bar and the pressure of the liquid nitrogen is 7 bar.Figure 1 shows that the gas nozzles 101 are located in a position that is slightly upstream a position of the orifice 102 with reference to a flow direction of the medium jet M. The gas conduit 103 extends downstream to the position of the orifice 102 where an ned of the gas conduit 103 forms a main outlet 105. The extension of the gas conduit 103 downstream the gas nozzles 101 may instead be seen as a short variant of a medium jet conduit 103B described in relation to figure 4.

[0041] The gas nozzles 101 are arranged to form a tubular volume of gas around the liquid nitrogen when liquid nitrogen flows from the tank and out through the orifice 102 and gas is flowing from the gas source and out through the one or more gas nozzles 101.

[0042] Figure 3 illustrates schematically how a medium jet may behave when expelled from the embodiment according to figure 1. The expelled gas 107 surrounds the liquid nitrogen leaving the outlet 105 and due to the high speed of the gas and its insulating properties, the stream 106 of liquid nitrogen can be kept homogenous and narrow while moving a significant distance. At some point, indicated by reference number 108, droplets split off from the liquid nitrogen and turbulence increases. Wavy double lines indicate that the flight length of the medium jet M typically is much longer than suggested by the size of the main outlet of the device 100. The flight length may be e.g. 5-10 meters or more depending on e.g. gas pressure.

[0043] Figure 4 shows a variant where the device 100 is provided with an extended medium jet conduit 103B arranged to guide the gas and the medium jet M in a downstream direction from the one or more gas nozzles 101. To provide a significant effect, the medium jet conduit 103B should normally have a length L so as to extend at least 50 mm, or at least a distance corresponding to twice its diameter D, from the orifice 102 in the downstream direction.The medium jet conduit 103B restricts radial expansion of the medium jet M and due to increased pressure from liquid nitrogen that to some extent evaporates in the jet, it can be used to increase the flow rate of the medium jet M. However, if the medium jet conduit 103B is too long, the flow rate may decrease because of increased flow restriction. A total length L of around 5 m or 100 times the diameter D of the medium jet conduit 103B is often applicable, depending e.g. on the gas pressure.

[0044] A further use of the medium jet conduit 103B is to reach closer to the target object before the jet is expelled through the outlet at the end of the medium jet conduit 103B. This may be useful for coming closer with the pipe end to a position that otherwise is difficult to reach, for instance a fire that is difficult to approach due to extreme heat or for reaching into a central region of some object that is on fire, such as a stack of sawdust. It could also be useful when combining the device 100 with a snowmaking machine to locate the outlet properly in a flow of air and water droplets used for making the snow,

[0045] Depending on the application, the gas supplied to the gas nozzles 101 may typically be nitrogen, carbon dioxide or air.

[0046] The conduits 103, 104 and 103B are preferably made of steel or other metal alloy adapted for cryogenic applications, such as stainless steel 316L. Also connectors, fittings, hoses, etc. should preferably be adapted for cryogenic applications.

[0047] A method for operating the device comprises:

[0048] - supplying liquid nitrogen to the orifice 102; and

[0049] - supplying pressurized gas to the one or more gas nozzles 101.

[0050] Liquid nitrogen may be supplied from an LN flask at a pressure of e.g. 5 bar. Gas may be supplied from a gas tank, a compressor or an external source at a pressure of e.g. at least 50 bar. The pressure of the gas is preferablyhigher than the pressure of liquid nitrogen to generate an efficient medium jet M.

[0051] In a firefighting or cooling application, the pressurized gas might be nitrogen or carbon dioxide and the method may comprise: directing the medium jet M towards an object for cooling the object and / or extinguishing a fire.

[0052] In a snowmaking application, the pressurized gas might be air and the method may comprise: mixing the medium jet M with a flow comprising air and water droplets so as to produce snow.

[0053] Air may be used also for cooling if the risk of fire is not relevant.

[0054] The invention is not limited by the embodiments described above but can be modified in various ways within the scope of the claims. For instance, other gases or gas mixtures may be used.

Claims

CLAIMS1. A device (100) for generating a jet of a medium (M) comprising gas (G) and liquid nitrogen (LN), wherein the device comprises:- an orifice (102) connected or connectable to a tank of liquid nitrogen; and - one or more gas nozzles (101) connected or connectable to a source of pressurized gas,wherein the orifice (102) and the one or more gas nozzles (101) are directed in a substantially similar direction and wherein the one or more gas nozzles (101) at least partly surround the orifice (102) so that, when liquid nitrogen flows from the tank and out through the orifice (102) and gas is flowing from the gas source and out through the one or more gas nozzles (101), the liquid nitrogen is at least partly surrounded by the gas in the medium jet (M) that is expelled from the orifice (102) and the one or more gas nozzles (101).

2. The device (100) according to claim 1, wherein the one or more gas nozzles (101) comprises a plurality of openings circumferentially distributed around the orifice (102).

3. The device (100) according to claim 2, wherein each of the openings has a diameter of 0.1-5 mm, or 0.5-3 mm, or 1-2 mm.

4. The device (100) according to any of the above claims, wherein the one or more gas nozzles (101) are arranged to form a tubular volume of gas around the liquid nitrogen when liquid nitrogen flows from the tank and out through the orifice (102) and gas is flowing from the gas source and out through the one or more gas nozzles (101).

5. The device (100) according to any of the above claims, wherein the one or more gas nozzles (101) is / are located in a position that is substantially aligned with or upstream a position of the orifice (102) with reference to a flow direction of the medium jet (M).

6. The device (100) according to any of the above claims, wherein the device (100) comprises a medium jet conduit (103B) arranged to guide the gas and the medium jet (M) in a downstream direction from the one or more gas nozzles (101).

7. The device (100) according to claim 6, wherein the one or more gas nozzles (101) is / are located upstream the orifice (102) and wherein a length (L) of the medium jet conduit (103B) is such that it extends in the downstream direction at least to the orifice (102).

8. The device (100) according to claim 6 or 7, wherein a length (L) of the medium jet conduit (103B) is such that it extends at least 50 mm, or at least a distance corresponding to twice its diameter (D), from the orifice (102) in the downstream direction.

9. The device (100) according to any of the above claims, wherein the orifice (102) is arranged at an end section of an LN conduit (104) connected or connectable to the tank of liquid nitrogen.

10. The device (100) according to any of the above claims, wherein the device (100) comprises a gas conduit (103) connected or connectable to the source of pressurized gas and wherein the gas conduit (103) is arranged to supply gas to the one or more gas nozzles (101 ).

11. The device (100) according to claims 9 and 10, wherein, at least in a region immediately upstream of the one or more gas nozzles (101), the LN conduit (104) extends inside the gas conduit (103).

12. The device (100) according to any of the above claims, wherein the device (100) comprises a source of pressurized gas fluidly connected to the one or more gas nozzles (101).

13. The device (100) according to claim 12, wherein the gas is nitrogen, carbon dioxide or air.

14. The device (100) according to any of the above claims, wherein the device (100) comprises a tank of liquid nitrogen fluidly connected to the orifice (102).

15. A method for operating a device (100) according to any of the above claims, the method comprising:- supplying liquid nitrogen to the orifice (102); and- supplying pressurized gas to the one or more gas nozzles (101).

16. The method according to claim 15, wherein a pressure of the pressurized gas supplied to the one or more gas nozzles (101) is higher than a pressure of liquid nitrogen supplied to the orifice (102).

17. The method according to claim 15 or 16, wherein the pressurized gas is nitrogen or carbon dioxide and wherein the method further comprises:- directing the medium jet (M) towards an object for cooling the object and / or extinguishing a fire.

18. The method according to claim 15 or 16, wherein the pressurized gas is air and wherein the method further comprises:- mixing the medium jet (M) with a flow comprising air and water droplets so as to produce snow.

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