Abstract:
An ultraviolet radiation lamp comprising a heat absorbing element on the exterior thereof such that, during operation of the lamp, the temperature of the lamp in contact with the heat absorbing element is at a lower temperature than the remainder of the lamp. The use of the lamp in a radiation source module and a fluid treatment system is also described. The ultraviolet radiation lamp is particularly useful for treatment of fluids such ambient air (e.g., containing pollutants), warm liquids and the like.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     In one of its aspects, the present invention relates to an ultraviolet radiation lamp. In another of its aspects, the present invention relates to a radiation source module comprising the ultraviolet radiation lamp. In another of its aspects, the present invention relates to a fluid treatment system comprising the ultraviolet lamp. 
     2. Description of the Prior Art 
     Fluid treatment systems are known generally in the art. 
     For example, U.S. Pat. Nos. 4,482,809, 4,872,980, 5,006,244, 5,418,370, 5,504,335, 5,539,210 and 5,590,390 (all in the name of Maarschalkerweerd and all assigned to the assignee of the present invention), the contents of each of which are hereby incorporated by reference, all describe gravity fed fluid treatment systems which employ ultraviolet (UV) radiation. 
     Generally, such prior fluid treatment systems employ an ultraviolet radiation lamp to emit radiation of a particular wavelength or range of wavelengths (usually between 185 and 400 run) to effect bacterial kill in or other treatment of the fluid being treated. Many conventional ultraviolet radiation lamps are known as “low pressure” mercury lamps. 
     In use, it is usually necessary that a “cold spot” be maintained in such lamps to allow the excess mercury in the lamp to condense thereby maintaining an adequate mercury vapour pressure for efficient emission of ultraviolet radiation. If the “cold spot” temperature is not within a narrow temperature range, the mercury vapour pressure in the low pressure lamp may not be suitable for efficient generation of UV radiation. Specifically, too high or too low a “cold spot” temperature will result in loss of efficiency of emission of UV radiation. This can lead to inadequate treatment of the fluid being treated. 
     When such mercury lamps are used in a fluid treatment system such as one of the specific systems described and illustrated in the Maarschalkerweerd patents referred to above, the necessary “cold spot” is through heat exchange with the water being treated since the water is moving and is typically at ambient temperature. However, when it is desirable to treat a fluid such as ambient air (e.g., containing pollutants that could be photocatalyzed) or relatively warm fluids (e.g., at temperatures greater than about 40° C.), there is a significant risk that the a “cold spot” having the desired suitable temperature will not be formed leading to the problems set out above. 
     Accordingly, it would be desirable to have an ultraviolet radiation lamp which, in use, provides the needed “cold spot” in a controllable fashion and could be used to treat ambient air, ambient gas or relatively warm fluids. It would be advantageous if the solution to the problem could be achieved with little or no redesign df the ultraviolet radiation lamp. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to obviate or mitigate at least one of the above-mentioned disadvantages of the prior art. 
     It is another object of the present invention to provide a novel ultraviolet radiation lamp. 
     It is yet another object of the present invention to provide a novel radiation source module for use in a fluid treatment system. 
     It is yet another object of the present invention to provide a novel fluid treatment system. 
     Accordingly, in one of its aspects the present invention provides an ultraviolet radiation lamp comprising a heat absorbing element on the exterior thereof such that, during operation of the lamp, the temperature of the lamp in contact with the heat absorbing element is at a lower temperature than the remainder of the lamp. 
     In another of its aspects the present invention provides a radiation source module for use in a fluid treatment system, the module comprising an ultraviolet radiation lamp comprising a heat absorbing element on the exterior thereof such that, during operation of the lamp, the temperature of the lamp in contact with the heat absorbing element is at a lower temperature than the remainder of the lamp, and support means to mount the module in the fluid treatment system. 
     In yet another of its aspects, the present invention provides a fluid treatment system comprising a fluid treatment zone and a radiation source module, the module comprising an ultraviolet radiation lamp disposed in the fluid treatment zone, the ultraviolet radiation lamp comprising a heat absorbing element on the exterior thereof such that, during operation of the lamp, the temperature of the lamp in contact with the heat absorbing element is at a lower temperature than the remainder of the lamp, and support means to mount the module to the fluid treatment system. 
     Thus, the present inventors have discovered that placement of a heat absorbing element on the exterior of the ultraviolet lamp provides a simple and effective manner for creating a cold spot in the lamp which allows for efficient emission of ultraviolet radiation. Thus, the invention may be practiced by retrofitting an otherwise conventional ultraviolet radiation lamp with the heat absorbing element. In other words, the complete redesign of the ultraviolet radiation lamp is not necessary to practice the invention. 
     In use, the heat absorbing element in the present ultraviolet radiation lamp functions as a “heat sink” on the exterior surface of the lamp. As such, during use in a fluid incapable of inherently providing the desirable “cold spot”, the heat absorbing element removes heat from the area of the lamp with which it is in contact. The result is the creation of a “cold spot” on the interior surface of lamp (i.e., wherein the mercury vapour is contained) corresponding to that area. The mercury vapour condenses on the cold spot thereby resulting in efficient emission of ultraviolet radiation from the lamp. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the present invention will be described with reference to the accompanying drawings, in which: 
     FIG. 1 is a side elevation, in partial cross-section, of a preferred embodiment of the present fluid treatment system; 
     FIGS. 2A-D illustrate a side elevation of various embodiments of a heat absorbing element useful in the present ultraviolet radiation lamp; 
     FIGS. 3A-D illustrate an end view of each of the various embodiments of the heat absorbing elements illustrated in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIG. 1, there is illustrated a fluid treatment system  10 . Fluid treatment system  10  comprises a fluid treatment zone  15 . Fluid treatment zone  15  is defined by a chamber having a chamber wall  20  (for clarity, the entirety of the chamber is not illustrated). 
     Disposed in fluid treatment zone  15  is an ultraviolet radiation lamp  25 . The nature of the ultraviolet radiation lamp  25  is not particularly restricted. As stated hereinabove the present invention is particularly applicable to mercury-based ultraviolet radiation lamps. Thus, it is preferred to selected lamp  25  from one of such lamps. Lamp  25  may be a conventional low pressure lamp, commonly referred to as G36T6L and G64T5L, supplied by manufacturers such as Light Sources Inc. and Voltarc Technologies Inc. 
     Lamp  25  is disposed within a protective sleeve  30 . Preferably, protective sleeve  30  is a quartz sleeve. 
     The unit of lamp  25  and protective sleeve  30  are connected to chamber wall  20  by a conventional sleeve/compression seal nut assembly  35 . Thus, assembly  35  comprises a sleeve  40  having a threaded end to which a nut  45  is engaged. Disposed between sleeve  40  and nut  45  is a rubber O-ring  50  which is compressed to form a seal with protective sleeve  30 . 
     At the end of lamp  25  there are a series of electrical connector pins  55 . Pins  55  are connected via a suitable connection (not shown) to an electrical supply (not shown). The mode of connection and the electrical supply are conventional. 
     Lamp  25  comprises an electrode filament  60  disposed adjacent pins  55 . An opposed electrode filament (not shown) is disposed at the opposite end of lamp  25 . As is known in the art, the region in lamp  25  between the electrodes is known as the “arc length”—i.e, the region of the lamp from which ultraviolet radiation is emitted. Depending on the nature of lamp  25 , the electrical connections from both electrodes in a lamp can be disposed at one end of the lamp or at opposed ends of the lamp. Either type of electrical connection scheme is suitable herein. 
     Disposed on the exterior of lamp  25  is a heat absorbing element  65 . In the preferred embodiment of the present ultraviolet radiation lamp, heat absorbing element  65  is an annular helical copper spring—see embodiment C in FIGS. 2 and 3. Of course, heat absorbing element  65  may be made from any other material having suitable heat absorbing capability (e.g., aluminum, brass and the like). 
     Adjacent lamp  25 , there is disposed a heat exchange unit  70 . Unit  70  comprises an air conditioning unit (not shown) capable of cooling air which travels through unit  70  in the direction of arrow A. 
     Alternative embodiments A, B and D of heat absorbing element  65  are illustrated in FIG. 2 and 3. 
     Fluid treatment system  10  may be operated in the following manner. 
     Air influent (e.g., containing bacterial or other pollutant to be treated) is fed into fluid treatment zone  15  in either of the directions of arrow B. Lamp  25  is powered and heat exchange unit  70  is activated. 
     The air to be treated passes by protective sleeve  30 . Protective sleeve  30  insulates lamp  25  and, in itself, causes lamp  25  to operate at a relatively high temperature which prevents formation of an adequate “cold spot” along the surface of protective sleeve  30 . The provision of heat absorbing element  65  on the exterior of lamp  25  allows for the formation of the “cold spot” on the interior of lamp  25  since heat absorbing element  65  acts as a heat sink. 
     The heat sink function of heat absorbing element  65  is enhanced by the use of heat exchange unit  70 . Specifically, relatively cool air from unit  70  is passed over heat absorbing element  65  enhancing its heat sink properties. If desired, heat exchange unit  70  may be controlled by a thermostat (not shown) which monitors the temperature of the air passing over heat absorbing element  65  and compares that with a pre-determined temperature value—the use of such a thermostat is conventional. 
     The provision of the “cold spot” allows for improved and/or optimum operation of lamp  25 . 
     While the present invention has been described with reference to preferred and specifically illustrated embodiments, it will of course be understood by those of skill in the arts that various modifications to these preferred and illustrated embodiments may be made without the parting from the spirit and scope of the invention. For example, while the illustrated embodiment has been shown with reference to air treatment, the present ultraviolet radiation lamp may be used with a variety of different modules (e.g., see the modules in the Maarschalkerweerd patents referred to hereinabove) and a variety of other fluid treatment techniques (e.g., in combination with photocatalysts to degrade organic pollutants). Further, the present ultraviolet lamp does not necessarily require a protective sleeve. Still further, while the heat absorbing element may be disposed at any location on the exterior of the lamp, it is preferred to located it outside the arc length to avoid blockage of the ultraviolet radiation. Still further, the heat absorbing element may be disposed on the exterior of the ultraviolet lamp such that the protective sleeve, if used, covers the heat absorbing element. Still further, it is possible to utilize a plurality of heat absorbing elements—i.e., this allows for modularization of the heat sink features of the heat absorbing element along the length of the lamp. Still further, the use of a heat exchange unit with the present ultraviolet radiation lamp is optional. Still further, the specific heat exchange unit may be modified to provide a direct connection to the heat absorbing element. Other modifications will be readily apparent to those with skill in the art.