Abstract:
An apparatus for cooling an enclosure provided. The enclosure has at least one opening for receiving cool air and discharging heated air. The apparatus includes a vortex tube with a first end for discharging warm air and a second end for discharging cool air. The apparatus further includes an inlet between the ends of the vortex tube for directing compressed air tangentially into the interior of the vortex tube. A first housing covers the first end of the vortex tube and creates a space through which warm air is channeled to the exterior. The vortex tube is connected by an attachment to the opening of the enclosure so that the vortex tube can discharge cool air into the interior of the enclosure. The apparatus further includes an air outlet conduit at an end of the attachment to facilitate discharge of heated air for the enclosure. Also, the apparatus includes at least one barrier that permits the outflow of warm air from the first housing and heated air from the air outlet conduit while blocking the inflow of moisture and other substances.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a national phase application, filed pursuant to 35 U.S.C. §371, of PCT Application No. PCT/CA2009/001059 filed on 29 Jul. 2009, which claims the Convention Priority benefit of U.S. Patent application No. 61/107,127 filed on Oct. 21, 2008. PCT/CA2009/001059 and U.S. 61/107,127 are incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed to the field of devices for cooling an enclosed space such as an enclosure for electronic components, using principles of vortex tube technology. 
     BACKGROUND OF THE INVENTION 
     The vortex tube, also known as the Ranque-Hilsch vortex tube, is a device that separates a compressed gas into hot and cold streams. It has no moving parts. Pressurized gas (usually air) is injected tangentially into a swirl chamber and accelerates to a high rate of rotation within an extended tube. As the rotating gas travels along the tube, it separates into a relatively warm outer shell and a cool core. The outer shell of the compressed gas can be allowed to escape from the end of the tube through an annular opening. The remainder of the gas can be forced to return in an inner vortex of reduced diameter within the outer vortex. The rotation rate (angular velocity) of the inner gas is the same as that of the outer gas, resulting in a “solid body rotation” of the gas. The solid body rotation is thought to be due to the relatively long time in which each parcel of air remains in the vortex. This allows friction between the inner parcels and outer parcels of gas to have a notable effect. For this effect to occur, the swirl chamber must be suitably dimensioned, for example to be sufficiently long for the solid body rotation and separation to occur. 
     Vortex tube-operated enclosure coolers, which are known in the art, have been developed to maintain a cool environment within relatively small enclosures such as electrical enclosures and control panels by producing a refrigerated air stream directed into the enclosure. Systems for electronics enclosures can be required to meet various industry standards, including NEMA standards. 
     NEMA ratings are standards that are useful in defining the types of environments in which an electrical enclosure can be used. The NEMA rating system is defined by the National Electrical Manufacturer Association (NEMA), and frequently signifies a fixed enclosure&#39;s ability to withstand certain environmental conditions. 
     NEMA ratings are mainly applied to fixed enclosures. For example, a NEMA rating would be applied to a fixed electrical box mounted outside, or a fixed enclosure used to house a wireless access point. Most enclosures rated for use in environments where the enclosure is subjected to spraying of water or cleaning have a NEMA type 4 rating. NEMA ratings have more stringent testing requirements to verify protection from external ice, corrosive materials, oil immersion, dust, water, etc. 
     The NEMA type 12 rating indicates that a given enclosure is rated appropriately for indoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment, to provide a degree of protection against dirt, circulating dust, lint, fibers, and other airborne particles and against dripping and light splashing of liquids. 
     The NEMA type 4 rating indicates that the enclosure is rated for either indoor or outdoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment, to provide a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water, and hose-directed water. The NEMA type 4 rating also indicates that the enclosure will be undamaged by the external formation of ice on the enclosure. 
     The NEMA type 4X rating indicates that the enclosure is rated for harsh corrosive conditions as well as the conditions specified for NEMA type 4 above. 
     It has proven to be difficult to provide a vortex tube cooling apparatus suitable for cooling electronics enclosures that meets the more rigorous NEMA standards. As well, prior art cooling systems suffer other disadvantages. One drawback of known systems stems from the difficulty inherent in a system that permits a flow of external air through an enclosure that may contain sensitive components. As well, when a conventional vortex tube is used, it can provide an opening into the enclosure that permits moisture or other unwanted substances to enter. Further, conventional vortex tubes tend to be larger so that openings are oriented away from possible sources of contaminants. 
     SUMMARY OF THE INVENTION 
     Because vortex tubes introduce a stream of cooled air into an enclosure, the enclosure must also be equipped with ventilation means to allow warm air to be discharged from the enclosure. This can pose a problem because the contents of such enclosures usually include electronics or other sensitive materials which could be damaged by extraneous elements such as moisture or other substances which could enter via an air intake or discharge opening. There is a need in the art for providing a vortex tube-operated enclosure cooler with a barrier to entry of such elements that still allows air to be vented from the enclosure. The barrier of the present invention provides improved resistance to the elements and may result in the enclosure attaining a NEMA type 4 or lower rating, thereby presenting advantages at a reduced cost. 
     In one aspect of the invention, there is provided an apparatus for cooling an enclosure, wherein the enclosure includes at least one opening for receiving a stream of cool air and for discharging heated air from the enclosure. The apparatus comprises a vortex tube having a first opening for discharge of warm air. The vortex tube also includes an opposed second end with a second opening for a discharge of cool air. The vortex tube further includes an inlet between said ends for directing a stream of compressed air tangentially into the interior of the vortex tube. The vortex tube, openings and inlet are configured to achieve a Ranque-Hilsch vortex effect. The apparatus further includes a first housing covering the first end of the vortex tube and a space within the first housing communicating with the first opening and the exterior of the first housing to channel the warm air to the exterior. The apparatus also includes an attachment to connect the vortex tube to at least one opening in the enclosure such that the second end of the vortex tube discharges the cool air stream through the attachment into the interior of the enclosure. The apparatus also includes an air outlet conduit at an end of the attachment proximate to the enclosure. The air outlet conduit is configured to communicate with the at least one opening in the enclosure for discharge of heated air from the enclosure. Also, the apparatus includes at least one barrier to permit the outflow of the warm air from the first housing and the heated air from the air outlet conduit while blocking the inflow of moisture and other substances. 
     In another aspect of the invention, there is provided a method for cooling an enclosure. The method includes the steps of directing compressed air tangentially into the interior of a vortex tube. A further step included in the method is forcing warm air past a barrier to permit the discharge of the warm air from a first opening of the vortex tube. A further step is the discharge of cool air toward the enclosure from an opening defined by an attachment attached to said vortex tube. 
     Directional references such as “upper”, “lower” and the like are used herein merely for convenience of description and do not limit the scope of the invention. All such directional references, whether in the present specification or claims, are defined as being purely relational in nature. It will be understood that the invention may be oriented in essentially any direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of the enclosure cooler of an embodiment of the present invention. 
         FIG. 2  is a cross-sectional side view of the enclosure cooler embodiment shown in  FIG. 1  taken along line  2 - 2 . 
     
    
    
     DETAILED DESCRIPTION 
     As used herein the term “enclosure” refers to a movable or immovable container or housing that provides shelter for equipment or components that require protection from various elements. A given enclosure may have contents requiring protection against incidental contact or from water or other indoor elements such as dirt, circulating dust, lint, fibers, and other airborne particles and from outdoor elements such as dirt and precipitation. In some embodiments, the enclosure is for protection of electronics and the enclosure cooler is for providing cooling action to the heat generated within the enclosure by the electronics. The term “enclosure cooler” as used herein refers to a device operating to provide cool air from a compressed air source according the principles of vortex tube technology as described in the Background section. 
     According to one embodiment shown in  FIGS. 1 and 2 , there is provided a vortex tube-operated enclosure cooler  10  which includes a tube  12 . The cooler also has a generator  13  with one or more tangential inlets  14  for entry of compressed air and an upper outlet  16  for exit of warm air. The cooler  10  also has an attachment  17  for connecting to an enclosure. The attachment  17  has a lower outlet  18  for the exit of cooled air. 
     The tangential inlets  14  are ideally equally displaced about the circumference of a top portion of the generator  13 . 
     In certain embodiments such as those described herein, the dimensions of the tube  12  depend on the size of the cooler  10 . By way of non-limiting examples, for a small cooler, the inside diameter of the tube  12  may be 0.25 inches and its length may be 3.25 inches. For a medium cooler, the inside diameter of the tube  12  may be 0.437 and its length may be 3.95 inches. 
     In some embodiments, a sleeve  19  is inserted into the tube  12  and press fit. The sleeve  19  has a smaller internal diameter than the tube  12  and may be formed from brass. Sleeves with varying internal diameters may be used depending on the volume of the compressed air introduced into the cooler  10 . Alternatively, an embodiment is contemplated in which no sleeve  19  is incorporated and the internal diameter of the tube  12  is uniform along the length of the tube  12 . In a further embodiment, the tube  12  may accommodate a sleeve  19  which is inserted, but which is not press fit. In this embodiment the tube  12  is machined slightly so that the sleeve  19  is removable. Again in this embodiment, sleeves with varying internal diameters may be used depending on the volume of the compressed air introduced into the cooler  10 . 
     The tube  12  is encased in a jacket  26  formed of hard and durable material such as stainless steel. The jacket  26  also includes an annular chamber  28  at its lower end. The generator  13  resides within the chamber  28 . The generator  13  is provided with tangential inlets  14  and with a flange  15  around the circumference of the generator  13 . The generator  13  has measurements that can vary significantly. By way of non-limiting example, a hole  27  defined by the generator  13  and extending along the length of the generator  13  can have an internal diameter between 0.096 inches and 0.154 inches for a small vortex tube and an internal diameter between 0.189 inches and 0.330 inches for a medium vortex tube. The length of the generator  13  may vary between 1.12 inches and 1.2 inches. 
     Chamber  28  has an air inlet port  30  protruding radially outwardly which opens into the chamber  28 . Port  30  is configured for attachment of a gas line (not shown) for providing compressed air into the chamber  28  at pressures between 0 to 250 psig with optimal pressures between 20 and 120 psig. The compressed air is directed toward the inlets  14 . A seal of the flange  15  with the interior sidewall of the swirl chamber  28  is optionally made with an o-ring  29 . The flange  15 , in combination with the o-ring  29 , prevent the input air A from leaking out of the jacket  26  and ensure that input air A is directed upward. 
     Chamber  28  has a lower opening which may be provided with threads for threaded connection into an enclosure exhaust chamber  32  in the connecting piece  17 . 
     The upper portion  34  of the jacket  26  adjacent the upper outlet  16  of the tube  12  may be provided with threads for connection of a cap  36  in a male-female connection. The cap  36  is provided with one or more cap ventilation holes  38  which allow warm air to escape from the upper outlet  16  of the tube  12 . Optionally, the inner side wall of the cap  36  defines a space for a muffler  40  whose function is to reduce the noise of air escaping from the upper outlet  16 . The muffler  40  may be formed from flame retardant sound reducing foam or high pressure resistant porous plastic. The muffler  40  may also be formed from sintered bronze or any other sound reducing material. 
     An upper housing  42  is provided which is optionally removable and is configured to fit over the upper portion of the jacket  26 . Housing  42  encases the tube  12 . The lower end  44  of the upper housing  42  rests upon the outer edge of the chamber  28 . The cap  36  includes an upper disc-shaped plate  46  which fits over, and is flush with, the upper edge of the upper housing  42 . The cap  36  thereby fixes the upper housing  42  in place above the chamber  28  providing a streamlined appearance for the cap  36 , upper housing  42  and chamber  28 . 
     Upper housing  42  is provided with one or more upper ventilation holes  48 . In the embodiments shown in  FIGS. 1 and 2 , there are four rows of five upper ventilation holes  48  disposed around the circumference of the upper housing  42  and located towards the lower end of the upper housing  42 . Warm air escaping from the upper outlet  16  through the cap ventilation holes  38  will then enter the interior of the upper housing  42  and escape from the upper housing ventilation holes  48 . 
     The attachment  17  can be any size that minimizes back pressure. By way of a non-limiting example, for a small vortex tube, the attachment  17  may be 3.2 inches long. For a medium vortex tube, the attachment  17  may be 3.5 inches long. As mentioned previously, the attachment  17  defines a passage  31 . The internal diameter of the passageway  31  defined by the attachment  17  used with a small vortex tube is 0.252 inches. The internal diameter of the passageway  31  defined by a attachment  17  used with a medium vortex tube is 0.400 inches. 
     The enclosure exhaust chamber  32  is formed of a sidewall  50  which contains there within the passageway  31 . The sidewall  50  is provided with one or more lower ventilation holes  52 . A removable lower housing  54  is configured to cover the outside of the sidewall  50  of the enclosure exhaust chamber  32  forming a space therein. A threaded cylindrical nut  55  locks the housing in place. 
     The outer sidewall of the exhaust chamber  32  is threaded and configured to be received in a threaded female opening in the enclosure  100 . 
     The enclosure cooler  10  is provided with an upper seal  56  and a lower seal  58  which collectively act as barriers to entry of extraneous elements, particularly entry of water. Seals  56  and  58  may be formed from any impervious material including rubber, plastic and metal. The material from which the seals  56  and  58  are formed is ideally resistant to water and any cleaning chemicals or solutions that may be used on any NEMA type 4X enclosure. The material is also preferably resistant to any corrosion. In a preferred embodiment, the seals  56  and  58  are flexible and resilient and formed of VITON® or an equivalent material. Also, the seals  56  and  58  are preferably annular. The outer diameter of the upper seal  56  is slightly larger than the internal diameter of the upper housing  42 . As a result, the upper seal  56  is pressed downward slightly so that the upper seal  56  is slightly domed when engaged with the upper housing  42  so that the inner portion of the upper seal  56  is slightly elevated above the outer portion of the upper seal  56 . Similarly, the outer diameter of the lower seal  58  is slightly larger than the internal diameter of the lower housing  54 . As a result, the lower seal  58  is pressed downward slightly so that the lower seal  58  is slightly domed when engaged with the lower housing  54  so that the inner portion of the lower seal  58  is slightly elevated above the outer portion of the lower seal  58 . 
     The upper seal  56  may be fastened to an upper portion of the tube  12  or, in the embodiment shown in  FIGS. 1 and 2 , to the outside of an upper portion of the jacket  26  which encases the tube. The fastening may be done with glue or a hinge or other such fastening means known to those with skill in the art. Alternatively, the upper seal  56  may be fixed in position by machining a groove into the upper portion of the tube  12  or the outside of an upper portion of the jacket  26 . Alternatively, the upper seal  56  may frictionally engage the housing of the tube  12 . In any case, the upper seal  56  is ideally disposed between the upper outlet  16  and the upper ventilation holes  48 . The upper seal  56  may be fixed by providing it with a central opening and fitting the seal onto the upper portion of the tube  12  or, in the case of the embodiments shown in  FIG. 1  and  FIG. 2 , onto an upper portion of the jacket  26  and sliding it downwards to an appropriate position. With reference to  FIGS. 1 and 2 , the upper seal  56  is shown at a position below the upper outlet  16  of the tube  12  and above the uppermost of the upper ventilation holes  48 . The outer edges of the upper seal  56  make contact with the inside wall of the upper housing  42 . 
     The lower seal  58  is fastened to the outside of the side wall  50  of the exhaust chamber  32  at a location below the lower ventilation holes  52 . In some embodiments, the lower seal  58  is fastened using glue or a hinge or other such means known to those skilled in the art. In other embodiments, a groove is provided in the outside of the exhaust chamber side wall  50  and the lower seal  58  fits within this groove (not shown). Alternatively, the lower seal  58  may frictionally engage the side wall  50  of the exhaust chamber  32 . The outside edges of the lower seal  58  make contact with the inner wall of the lower housing  54 . 
     In operation, a compressed air line is connected to the side inlet  30  of the enclosure cooler  10 . Compressed air A is then allowed to flow through the air line and the side arm  30  toward the inlets  14 . The air then vortexes upward in the tube  12  until it reaches the top of the tube  12 . At this point, some of the warm air B exits the upper outlet  16 , passes through the cap ventilation holes  38  and enters the interior space defined by the outside wall of the jacket  26  and the inside wall of the upper housing  42 . This warm air B moves downward through this space and exerts a downward force against the upper seal  56 . In response, the upper seal  56  flexes downward and breaks its contact with the inner wall of the upper housing  42  allowing the warm air B to move past the upper seal  56  and exit through the upper ventilation holes  48  to the atmosphere. 
     Returning now to the point where the warm air B reaches the top of the tube  12 , as mentioned above, some of the warm air B escapes from the upper outlet  16 . At this point, some of this warm air B is also deflected downwards by the upper top wall of the cap  36  and vortexes more slowly downwards in the center of the tube  12  along the axis of the tube  12 . Transfer of heat occurs from the downward vortexing air to the upward vortexing air, thereby cooling the downward vortexing air. There are different explanations for this previously known vortex and heat transfer behaviour referred to as the Ranque-Hilsh effect. One explanation is the solid body rotation of the air in the tube whereby the inner air rotates at the same rate as the outer air, contrary to standard vortex behaviour. The rotation rate of the inner air may be caused by the effect of friction and the length of time that each parcel of air remains in the vortex. Further, because of the effect of centrifugal force, the outer air is under higher pressure, thus increasing the temperature. 
     The downward vortexing air continues downward in the tube  12 . The downwardly vortexing air is cooled significantly when it enters hole  27  from the tube  12  because of the smaller diameter of the tube  12 . The downwardly vortexing air continues into the passageway  31 , exits the lower outlet  18  of the tube and enters the interior of the enclosure as significantly cooled air C. 
     As a result of the cooled air entering the enclosure  100 , air D contained within the enclosure (which has been heated by the electronic components within the enclosure) is displaced out of the enclosure and into the enclosure exhaust chamber  32 . This enclosure-warmed air D moves upwards in the exhaust chamber  32 , is vented through the lower ventilation holes  52  in the side wall of the exhaust chamber  32 , and enters the space defined by the outer wall of the exhaust chamber  32  and the inner wall of the lower housing  54 . This enclosure-warmed air D reverses direction and moves downward through this space and exerts a downward force against the lower seal  58 . In response, the lower seal  58  flexes downwards and breaks its contact with the inner wall of the lower housing  54 , thus allowing the enclosure-warmed air D to move past the lower seal  58  to the outer atmosphere. 
     If the device is subjected to a spray of water (for example in a test to establish a NEMA rating) some of the sprayed water will enter the upper ventilation holes  48  and move upward to make contact with the upper seal  56 . At this point, if the device is at rest (i.e. no air is circulating through it) the upper seal  56  will, upon impact by the spray of water, maintain contact with the inner wall of the upper housing  42  to thereby prevent water from moving further up the interior of the upper housing  42  where it could potentially enter the tube and enclosure via the upper outlet  16 . In some embodiments, the upper seal  56  flexes upwards upon contact with the spray of water and the upward flexing causes the seal to maintain contact with the inner wall of the upper housing  42  to maintain the barrier to entry of water. If the device is operating, the downward flow of warmed air B past upper seal  56  prevents inflow of water. Thus the upper seal  56  must be configured so as to quickly return to its resting position in contact with upper housing  42 . Similarly, when in operation, the downward movement of enclosure warmed air D prevents the entry of moisture and other contaminants through the lower ventilation holes  52  and eventually into the enclosure. At rest, the lower seal  58  prevents such entry by flexing upwards upon contact with the spray of water and the upward flexing causes the lower seal  58  to maintain contact with the inner wall of the lower housing  54  to maintain the barrier to entry of water. Thus the lower seal  58  must be configured to quickly return to its resting position when the device is not operating. 
     The upper seal  56  and lower seal  58  therefore work to provide the enclosure cooler  10  with a water barrier for protection of the enclosure from entry of water, chemicals used for cleaning and/or other detrimental elements. 
     It will be seen that the present invention has been described by way of preferred embodiments of various aspects of the invention. However, it will be understood that one skilled in the art may readily depart from the embodiments described in detail herein, while still remaining within the scope of the invention as defined in this patent specification as a whole including the claims thereto. If will be further understood that structural or functional equivalents of elements described herein are considered to be within the scope of the invention, as well as departures from any directional references, dimensions or configurations described herein.