Abstract:
A reactor that operates with ultraviolet light emitting diodes (UV-LEDs) to attain UV photoreactions or UV photo-initiated reaction in a fluid flow for various applications, including water purification. The UV-LED reactor is comprised of a conduit means for passing fluid flow, an ultraviolet light emitting diode (UV-LED), and a radiation-focusing element to focus the UV-LED radiation to the fluid in the longitudinal direction of the conduit. The UV-LED reactor may include photocatalysts or chemical oxidants, which are activated by UV emitted by UV-LEDs for photocatalytic and photo-initiated reactions.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/896,554, filed Oct. 28, 2013, the disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to ultraviolet (UV) reactors, and more particularly, to a UV reactor operating with ultraviolet light emitting diode (UV-LED). 
         [0003]    Ultraviolet (UV) reactors—reactors that contains UV radiation—are applied to many photoreactions, photocatalytic reactions, and photo-initiated reactions. One of the main applications of UV reactors is for water and air purification. In particular, UV reactors have emerged in recent years as one of the best water treatment alternatives. UV reactor systems currently operating use low- and medium-pressure mercury lamps. 
         [0004]    Light emitting diodes (LEDs) emit radiation of a single wavelength. With recent advances in LED technology, they may be designed to generate UV radiation at different wavelengths, which include the wavelength for DNA absorption as well as a wavelength that can be used for photocatalyst activation. UV-LEDs have many advantages compared to traditional mercury UV lamps, including a compact and robust design, lower voltages and power requirements, and the ability to turn on and off with high frequency. The UV-LEDs advantages make them an attractive alternative for replacing UV lamps in UV reactor systems. This replacement also makes possible the development of novel UV reactors with new applications. 
         [0005]    The performance of UV-LED reactors (reactors that operate with UV-LEDs as a source of UV radiation) may significantly improve with optimizations to the reactor geometry, the reactor hydrodynamics, and UV radiation distribution. Unlike UV lamps, UV-LEDs are radiation sources with individual small sizes. They may be positioned in a reactor with a higher degree of freedom compared to the arrangement of UV lamps. 
       SUMMARY OF THE INVENTION 
       [0006]    A new UV-LED reactor concept with precise control of both the fluidic and optical environments, which would provide high and uniform radiation exposure to a fluid flow at a small footprint, is of great interest to the UV reactor industry. Such an efficient and compact UV-LED reactor will make it capable of being incorporated into some devices for various UV photoreaction applications, including UV-based water treatment. 
         [0007]    In one aspect, the present invention is an ultraviolet (UV) reactor comprising a conduit for transporting fluid flow; an ultraviolet light emitting diode (UV-LED); and a radiation-focusing element. The fluid flow moves in the longitudinal direction of the conduit and is irradiated in the longitudinal direction of the conduit by UV-LED radiation that is passed through the focusing element. 
         [0008]    The UV reactor may be a fluid treatment reactor, such as water treatment reactor. Further, the reactor may be a water treatment reactor of an appliance or a healthcare device. The focusing element of the reactor may be a focusing lens disposed proximate to the UV LED. The focusing lens may be a collimating lens, or a collimating lens and a converging lens. The UV-LED and the collimating lens may be arranged, such that UV-LED radiation that is emitted into the fluid flow in the conduit extensively covers the transverse cross-section of the conduit. Further the reactor may be array of conduits, wherein the fluid flow in at least one conduit is irradiated by one or more UV-LEDs. The UV-LED may be positioned at a longitudinal end of the conduit. The UV-LED reactor may contain several UV-LEDs that emit different UV wavelengths. The UV reactor may contain a photocatalyst supported on a structure in the reactor; it may also contain a chemical reagent that is added to the reactor. The UV-LED may be turned on and off automatically by an external signal. The reactor may contain an element to restrain the fluid flow in the conduit, such as a static mixer. 
         [0009]    In another aspect, the present invention is a method of attaining UV photo reaction or UV photo-initiated reaction in a fluid flow. This is accomplished through passing the fluid flow in the longitudinal direction of a conduit; focusing the ultraviolet radiation from an ultraviolet light emitting diode (UV-LED) by means of a focusing element, such as a collimating lens; and emitting the focused ultraviolet radiation from the UV-LED in the longitudinal direction of the conduit. A photocatalyst may be used to promote photocatalytic reactions in the fluid. 
         [0010]    In yet another aspect, the present invention is a method for the treatment of a fluid, such as water or air. This is accomplished through passing the fluid flow in the longitudinal direction of a conduit; focusing the ultraviolet radiation from an ultraviolet light emitting diode (UV-LED) by means of a focusing element, such as a collimating lens; and emitting the focused ultraviolet radiation from the UV-LED in the longitudinal direction of the conduit. The microbial and chemical contaminants in the fluid flow may be eliminated while the ultraviolet radiation is emitted into the fluid flow. 
         [0011]    The following will describe, in detail, several variations of the present invention. 
         [0012]    The efficiency of a UV reactor is determined by the total UV fluence, which is the radiant exposure delivered to a fluid in the reactor. The UV fluence is the product of the UV fluence rate, which is the incident radiant power, and the exposure time. The fluence rate in a UV reactor may be controlled by adjusting the UV-LED radiation pattern in the reactor, while the exposure time may be controlled by adjusting the reactor hydrodynamics. The UV-LED reactor of the present invention offers high reactor performance through its precise control of both the radiation pattern and the hydrodynamics. Further, the UV-LED reactor of the present invention provides high efficiency by increasing uniformity in UV fluence distribution to the fluid and by delivering the majority of UV radiation directly to the fluid, instead of losing the UV radiant energy to the reactor wall. 
         [0013]    In one variation, the present invention is a reactor operating with one or more ultraviolet light emitting diodes (UV-LEDs) in order to cause photoreactions or photo-initiated reactions in a fluid. The UV-LED reactor comprises a single or series of flow channels (conduit, tube), which is irradiated, either with one UV-LED, or with an array of them. The reactor may comprise a single flow channel, a series of parallel flow channels, or a stack of multiple flow channels. In a multi-channel reactor, the fluid flow may go through the channels in parallel or in series (fluid flow going from one channel to another, where the flow channels are connected at one end). The fluid flow is moving mainly in the longitudinal direction of the channels. The UV-LED radiation is focused through a focusing element, such as a collimating lens. The fluid flowing in the reactor channels is irradiated by focused radiation from the UV-LEDs in the longitudinal direction of the channels. The LEDs may be positioned at one or both ends of the flow channels. The total UV dose delivered to a fluid may be controlled by adjusting the flow rate and/or regulating UV-LED power, and/or turning on/off the number of UV-LEDs. The reactor configuration of the present invention makes the design and fabrication of an efficient and compact UV reactor with all-integrated components possible. 
         [0014]    In one variation of the present invention, the focusing element is a focusing lens, such as a collimating or a converging lens, disposed proximate to the UV-LED. This lens may be either a stand-alone lens or a lens integrated into the UV-LED device. The lens may be made of quartz or another UV transparent material. A combination of a collimating lens and a converging lens may also be used. Applying a collimating lens to focus the radiation into the reactor channels causes minimal attenuation of the UV energy through the reactor length and negligible UV energy loss to the reactor channel walls. This particular configuration of the UV-LED reactor, which involves collimating the UV-LED radiation, may results in an effective utilization of UV-LED radiant power, and may lead to a superior reactor performance. 
         [0015]    In another variation of the present invention, one or more photocatalysts may be used in the UV-LED reactor to be activated by UV, which would then form oxidative hydroxyl radicals, as well as other active radicals. The photocatalyst may be any combination of different photocatalysts, catalyst supports, and co-catalysts. This configuration may result in photocatalytic or photo-initiated oxidation/reduction reactions. The photocatalysts may be supported on a structure, such as a solid substrate, a porous substrate, mesh, screen, metal foam, cloth, or a combination thereof. The photocatalysts that are supported on different solid or perforated substrates may be positioned in the flow channels. In particular, a UV-LED reactor containing a photocatalyst on a perforated support substrate in the cross section of the reactor channel, irradiated with collimated UV radiation from a UV-LED, will efficiently utilize the UV-LED radiation. This configuration may result in a highly effective UV-LED photocatalytic reactor. 
         [0016]    In another variation of the present invention, static mixers and vortex generators may be used in the flow channels to increase mixing and/or to rotate the flow as it goes through the flow channels. This configuration may result in enhanced UV-LED reactor performance by delivering a more uniform UV dose or by improving mass transfer near the photocatalyst surface (provided that photocatalyst presents in the reactor). 
         [0017]    In another variation of the present invention, UV-LEDs that emit UV radiation of different wavelengths may be used. This configuration may result in a synergistic effect and increase the rate of photoreactions and photocatalytic reactions. 
         [0018]    In another variation of the present invention, the LEDs may operate in a pulsed mode (likely at high frequencies). This mode of operation may affect the photoreaction rate as well as the photocatalyst&#39;s electron-hole recombination, and thereby increase photocatalytic efficiencies. 
         [0019]    In another variation of the present invention, the LEDs may be programmed to turn on and off automatically, for example, as the fluid flow starts or stops moving in the reactor, or at specific time intervals. For controlling UV-LEDs&#39; on/off status, a sensor may be used to detect the fluid motion or the like. This configuration may result in saving energy used by the reactor. 
         [0020]    In another variation of the present invention, the LEDs may be programmed to adjust their power output, or to turn some of the LEDs on and off automatically by receiving a signal. The signal may be generated, for example, as the flow rate or as the quality of the fluid passing through the UV-LED reactor changes. This configuration may result in providing appropriate radiation energy to the fluid based on any particular operating conditions. 
         [0021]    In another variation of the present invention, the fluid flowing through the channels may be used to transfer the heat generated by the LEDs. This may be achieved by using part of the fluid to be circulated in the proximity of the LEDs or their circuit board. This may also be achieved by using highly thermal conductive material, as the LED board connected to flow channel walls is also made of highly thermal conductive material. This configuration may improve thermal management and the lifetime of the UV-LEDs. 
         [0022]    While the UV-LED reactor of the present invention may be used for many photoreactions, photocatalytic reactions, and photo-initiated reactions, one of the main applications is the purification of water or purification of other UV-transparent fluids. 
         [0023]    In another variation, the present invention is a UV-LED reactor that uses a focusing element to focus UV radiation of a UV-LED into the water flow as it moves through the reactor flow channel for water purification. Water treatment may be achieved by the inactivation of microorganisms (e.g., bacteria and viruses) and the degradation of micro-pollutants, such as chemical contaminants (e.g., toxic organic compounds), by direct photoreactions, and/or photocatalytic reactions, and/or photo-initiated oxidation reactions. Water may flow through the UV-LED reactor by the use of a fluid-moving device, such as an electrical pump. The UV-LEDs are preferably powered by a wall plug or a battery. If applicable, a photocatalyst may be immobilized on a solid substrate, where the fluid passes over, or on a perforated substrate where the fluid passes through. The photocatalyst may be titanium dioxide TiO 2 , or other photocatalysts. If applicable, chemical reagents, such as chemical oxidants may be injected into the UV reactor. The chemical oxidant may be hydrogen peroxide H 2 O 2 , ozone O 3 , or other chemicals. 
         [0024]    In one variation of the present invention, the UV-LED water purification reactor is incorporated in appliances that dispense or use water for consumption. The UV-LED reactor treats the water that is used in the appliances, such as refrigerators, freezers, water coolers, coffee makers, wending machines, and the like. The water may be pure water or water-based fluids such as coffee. The UV-LEDs of the reactor may be turned on and off automatically as the water starts or stops flowing. A UV-LED reactor that is incorporated in appliances, such as water coolers and refrigerators is an effective technique to reduce the microbial contamination in the water leaving the waterline (for consumption) and to reduce the risk for infection. 
         [0025]    In another variation of the present invention, the UV-LED water purification reactor is incorporated in a healthcare device. The UV-LED reactor treats the water used in or by the healthcare devices, such as hemodialysis devices (hemodialysis machine) or colon hydrotherapy equipment. The UV-LED reactor may be integrated in these devices/equipment along with other forms of water purification methods such as filtration. 
         [0026]    These and other features, aspects, and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1A  illustrates the schematic of UV-LED radiant beams from a collimating optical lens; 
           [0028]      FIG. 1B  illustrates the schematic of UV-LED radiant beams from a converging optical lens; 
           [0029]      FIG. 2  is a partially-diagrammatic perspective view of a UV-LED reactor of the present invention; 
           [0030]      FIG. 3A  is a partially-diagrammatic top view of the UV-LED reactor shown in  FIG. 2 ; 
           [0031]      FIG. 3B  is a partially-diagrammatic side view of the UV-LED reactor shown in  FIG. 2 ; 
           [0032]      FIG. 3C  is a partially-diagrammatic side view of the UV-LED reactor shown in  FIG. 2 ; 
           [0033]      FIG. 4  is a partially-diagrammatic top view of a UV-LED reactor of the present invention; 
           [0034]      FIG. 5A-5E  are partially-diagrammatic side views of various variations of UV-LED reactor of the present invention; 
           [0035]      FIG. 6A  is a partially-diagrammatic side view of a variation of UV-LED reactor of the present invention; 
           [0036]      FIG. 6B  is a partially-diagrammatic side view of a variation of UV-LED reactor of the present invention; 
           [0037]      FIG. 7A  is a partially-diagrammatic top view of a UV-LED reactor of the present invention; 
           [0038]      FIG. 7B  is a partially-diagrammatic side view of a UV-LED reactor of the present invention; 
           [0039]      FIG. 7C  is a partially-diagrammatic perspective view of a UV-LED reactor of the present invention; 
           [0040]      FIG. 8A  is a partially-diagrammatic top view of a UV-LED reactor of the present invention; 
           [0041]      FIG. 8B  is a partially-diagrammatic side view of a UV-LED reactor of the present invention; 
           [0042]      FIG. 8C  is a partially-diagrammatic perspective view of a UV-LED reactor of the present invention; 
           [0043]      FIG. 8D  are partially-diagrammatic top view of a UV-LED reactor of the present invention, showing UV rays; 
           [0044]      FIG. 9A  is a partially-diagrammatic perspective view of a UV-LED reactor of the present invention; 
           [0045]      FIG. 9B  is a partially-diagrammatic perspective view of a UV-LED reactor of the present invention; 
           [0046]      FIG. 10A  is a partially-diagrammatic perspective view of a UV-LED reactor of the present invention; 
           [0047]      FIG. 10B  is a partially-diagrammatic perspective view of a UV-LED reactor of the present invention; 
           [0048]      FIG. 11  is a partially-diagrammatic perspective view of a UV-LED reactor applied to water treatment; 
           [0049]      FIG. 12  is a partially-diagrammatic perspective view of a refrigerator containing a UV-LED reactor; and 
           [0050]      FIG. 13  is a partially-diagrammatic perspective view of a hemodialysis machine containing a UV-LED reactor. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0051]    The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
         [0052]    Referring to  FIG. 1A-1B , there are shown the side views of the schematics of UV-LED collimated radiation  11  (in  FIG. 1A ) and converged radiation  12  (in  FIG. 1B ). Referring to  FIG. 1A , there is shown a side view of radiant beams  13  emitted from an LED  14  after passing through a collimating lens  15 . Referring to  FIG. 1B , there is shown the side view of radiant beams  16  emitted from an LED  17  after passing through a converging lens  18 . The arrows indicate the main direction of the radiant beams. 
         [0053]    For the invention described in the following figures,  FIG. 2  to  FIG. 10 , the LEDs&#39; radiation pattern is focused by applying appropriate optical lenses that are either integrated in, or disposed close to, the UV-LEDs. The optical lenses used for focusing UV-LED radiation in several of the following figures,  FIG. 2  to  FIG. 10 , are not shown for the sake of simplicity, as well as for clearer visualization of the reactor concepts. 
         [0054]    Referring now to the invention in in more detail in  FIG. 2  and  FIG. 3 , there are shown a perspective view ( FIG. 2 ), a top view ( FIG. 3A ), and side views ( FIG. 3B  and  FIG. 3C ) of a UV-LED reactor according to an exemplary embodiment of the present invention. There is shown a UV-LED reactor  10  having a housing  31 , flow channels  32  with channel walls  37 , an inlet  33  for fluid (e.g., water) to enter and an outlet  34  for fluid to exit, one or more LEDs  35  placed in LED housing  38 , and a UV-transparent window  36 , such as a quartz window. The LEDs may be mounted on a circuit board (not shown to keep the drawing simple). There may be one or more heat sinks, drive circuits for UV-LEDs, microcontrollers and other electronic mechanisms, a power port, and an on/off switch (none is shown here to keep the drawing simple). Different lenses, including collimating, converging, and other lenses (not shown), are disposed in the reactor in front of the UV-LEDs to focus the UV-LED radiation pattern. Two adjacent flow channels are connected at one end of some flow channels for the fluid to go from one channel to another channel (the fluid goes through multi-passes through the rector). The main fluid flow directions are shown by the arrows, showing the fluid flow enters the reactor from inlet  33 , flow through the reactor channels and turns at the end of some of the channels and exits from outlet  34 . 
         [0055]    Still referring to the invention of  FIG. 2  and  FIG. 3  in more detail, the fluid flows in and out of the UV-LED reactor, passes through the channels, and is irradiated by UV radiation from UV-LEDs. The LED(s) are positioned at one end of the flow channel. The main direction of the radiant beams and of the flow are along the longitudinal direction of the reactor channels. The internal wall of the channels can be made of or be coated with material with high UV reflectivity to reflect to the fluid any part of the radiation that is emitted to the channel walls. Using a collimating lens may be particularly advantageous for this design to keep the radiation intensity relatively high through the flow channel. The reactor may be used for attaining UV photoreaction in a fluid flow. The reactor may also be used for the treatment of a fluid, such as treatment of water. The UV-LEDs may be turned on and off automatically by an external signal, such as a signal from a device that detects the fluid flow rate. 
         [0056]    Referring now to  FIG. 4 , there is shown a UV-LED reactor according to an exemplary embodiment of the present invention. In  FIG. 4 , there is shown the top view of a UV-LED reactor  20 , having a housing  54 , flow channel walls  55 , an inlet  56  for fluid (e.g., water) to enter and an outlet  57  for fluid to exit, LEDs  58 , and a UV-transparent window  59 . The UV-LED reactor is a multi-channel reactor where the fluid flow is irradiated by the LEDs in some of the channels from one end (the two channels on the sides) and in some of the channels from two ends (the two channels in the middle), as the fluid flow moves through the reactor channels. The main fluid flow directions are shown by the arrows. 
         [0057]    Referring now to  FIGS. 5A-5E , there are shown the side views of several single channel UV-LED reactor configurations according to an exemplary embodiment of the present invention. In general, these configurations may be applied to both single and multi-channel UV-LED reactors. The inlet and outlet orientations and their fluid flow directions may be different for a multi-channel reactor compared to those for a single-channel reactor. The straight black arrows indicate the main direction of the flow, both in the reactors and in the inlet and outlet of the reactors. 
         [0058]    Referring now to  FIG. 5A , there is shown the side view of a UV-LED reactor  30  having a housing  61 , a UV-LED  62 , and a UV-transparent window  63 . This single-channel reactor is irradiated from one end of the flow channel, offering the flexibility of the outlet direction. A chemical reagent (not shown) may be added to the reactor along with the fluid flow to cause some desirable photoreactions. 
         [0059]    Referring now to  FIG. 5B , there is shown the side view of a UV-LED reactor  40  having a housing  64 , UV-LEDs  65 , and UV-transparent windows  66 . This single-channel reactor is irradiated from both ends of the flow channel, offering a higher radiation fluence compare to the one irradiated form one end. Each UV-LED may emit UV radiation of a specific wavelength to provide a combination of different wavelengths irradiating the fluid flow. 
         [0060]    Referring now to  FIG. 5C , there is shown the side view of a UV-LED reactor  50  having a housing  71 , a UV-LED  72 , a UV-transparent window  73 , and an element to restrain the fluid flow functioning as a static mixer  74 . The curved black arrows indicate mixing of the fluid after passing through the static mixer. The static mixer is applied for the enhancement of mixing and the generation of potential vortices for the improvement of the UV-LED reactor hydrodynamics. Mixing may result in a more uniform distribution of the fluence delivered to the fluid moving in the reactor channels, thereby increasing the reactor performance. 
         [0061]    Referring now to  FIG. 5D , there is shown the side view of a UV-LED reactor  80  having a housing  81 , UV-LEDs  82 , UV-transparent windows  83 , and photocatalyst immobilized on support structures  84 . The photocatalyst is activated by UV radiation from the UV-LEDs to initiate photocatalytic reactions in the UV-LED reactor. 
         [0062]    Referring now to  FIG. 5E , there is shown the side view of a UV-LED reactor  90  having a housing  85 , UV-LEDs  86 , UV-transparent windows  87 , and photocatalyst immobilized on perforated support structures  88 . The photocatalyst is activated by UV radiation from the UV-LEDs to initiate photocatalytic reactions. This configuration, in which the photocatalyst is disposed in the reactor channel cross-section, along with collimated UV radiation focused to irradiate the photocatalyst, may provide high radiation flux to the photocatalyst. 
         [0063]    Referring now to  FIGS. 6A and 6B , there are shown the side views (with the dotted lines showing the direction of the third dimension) of two UV-LED reactors  80  and  90 , comprising a stack of UV-LED flow channels according to an exemplary embodiment of the present invention. In  FIG. 6A  there is shown the side view of a UV-LED reactor  80  with rectangular flow channels, having a housing  91 , flow channels  92 , and UV-LEDs  93  (other components including UV-transparent windows, etc. are not shown for making the figure simple). In  FIG. 6B  there is shown the side view of a UV-LED reactor  90  with triangular flow channels, having a housing  95 , flow channels  96 , and UV-LEDs  97  (other components including UV-transparent windows, etc. are not shown to keep the drawing simple). The fluid is irradiated by the LEDs, as it moves through the channels. This configuration makes possible the manufacturing of UV-LED reactors with the potential of delivering high UV fluence (dose) and/or high throughput. The flow channel cross section may be rectangular  FIG. 6A , triangular  FIG. 6B , or other shapes. The main fluid flow directions are shown by the arrows. 
         [0064]    Referring now to  FIG. 7A-7C , there are shown a top view ( FIG. 7A ), a side view ( FIG. 7B ), and a perspective view ( FIG. 7C ) of a UV-LED reactor according to an exemplary embodiment of the present invention in more details. There is shown a UV-LED reactor  110 , having a housing  119 , an inlet port  111  for fluid to enter, an outlet port  112  for fluid to exit, flow channels  113  with channel walls  114 , two UV-LEDs  115  mounted on a circuit board  116 , a UV-transparent window  118 , on/off switch  121 , and a power port  122 . The drive circuits for UV-LED, microcontrollers, and other electronic mechanisms (none is shown here to keep the drawing simple) may be placed in the electronic housing  123  between the LED circuit board and the on/off switch. Different focusing lenses (not shown), such as a collimating lens may be installed in the reactor in front of the UV-LEDs to focus the UV-LED radiation into the fluid moving in the flow channels. The fluid flows in and out of the UV-LED reactor, passes through the channels, and is irradiated by UV radiation from UV-LEDs. 
         [0065]    Referring now to  FIG. 8A-8D , there are shown a top view ( FIG. 8A  and  FIG. 8D ), a side view ( FIG. 8B ), and a perspective view ( FIG. 8C ) of a UV-LED reactor according to an exemplary embodiment of the present invention with more details. There is shown a UV-LED reactor  120 , having a housing  139 , an inlet port  131  for fluid to enter, an outlet port  132  for fluid to exit, flow channels  133  with channel walls  134 , UV-LEDs  135  mounted on a circuit board  136 , collimating lenses  137  disposed in front of the UV-LEDs, a frame  144  for holding the collimating lenses in place, a UV-transparent window  138 , an on/off switch  141 , and a power port  142 . The drive circuits for UV-LEDs, microcontrollers, and other electronic mechanisms (none is shown here to keep the drawing simple), may be placed in the electronic housing  143 , between the LED circuit board and the on/off switch. The collimating lenses collimate UV radiation from the UV-LEDs into the fluid flow channels. The UV-LED  135  may have a converging lens integrated in the LED. The presence of both a converging lens and a collimating lens in front of a UV-LED may provide a more effective way of irradiating the fluid flow. Referring to  FIG. 8D , there are shown UV rays  145  emitted from the UV-LEDs  135  after passing through the collimating lenses  137 , are becoming collimated rays  146 . The fluid flows in and out of the UV-LED reactor, passes through the channels, and is irradiated by UV collimated rays  146  in the reactor channels. This reactor configuration may have circular cross section of the flow channels, with a diameter similar to that of the collimating lens, so that the UV-LED radiation that is emitted into the fluid flow in the flow channels substantially covers the transversal (or radial) cross-section of the flow channel. The main directions of UV rays are shown by the dashed arrows. 
         [0066]    Referring now to  FIG. 9A-9B , there are shown partially-diagrammatic perspective views of two configurations for UV-LED reactors, irradiated by UV-LEDs, and disposed through the length of the UV-LED reactor channels. Only the UV-LEDs, UV-LED boards, and photocatalyst structures of the UV-LED reactors are shown in these figures (for simplicity and for a better illustration of the concepts).  FIG. 9A  illustrates a UV-LED reactor  130 , having a series of UV-LEDs  152  mounted on perforated boards  153 , wherein the fluid flow (not shown) in the UV-LED reactor channel  151  is irradiated by the UV-LEDs  152 .  FIG. 9B  illustrates a UV-LED reactor  140 , having a series of UV-LEDs  155  mounted on a perforated board  156 , and a series of photocatalyst structures  157 , wherein the fluid flow (not shown) and the photocatalyst structures in the UV-LED reactor channel  154  are irradiated by the UV-LEDs. The fluid flow passes through the LED perforated boards and the photocatalyst structures. This configuration may cause photoreactions and photocatalytic reactions in the fluid. The arrows show the overall direction of the fluid flow as it moves through the UV-LEDs and photocatalyst structures. 
         [0067]    Referring now to  FIG. 10A-10B , there are shown partially-diagrammatic perspective views of two configurations for UV-LED reactors, irradiated by UV-LEDs, and disposed throughout the length of the UV-LED reactor channels. Only the UV-LEDs, UV-LED boards, and photocatalysts parts of the UV-LED reactors are shown in these figures (for simplicity and for a better illustration of the concepts).  FIG. 10A  illustrates a UV-LED reactor  160 , which has a series of UV-LEDs  162  mounted on solid boards  163 , wherein the fluid flow (not shown) in the UV-LED reactor channel  161  is irradiated by the UV-LEDs  162 .  FIG. 10B  illustrates a UV-LED reactor  170 , which has a series of UV-LEDs  165  mounted on a solid board  166 , and a series of photocatalyst structures  167 , wherein the fluid flow (not shown) and the photocatalyst structures in the UV-LED reactor channel  164  are irradiated by the UV-LEDs. The fluid flow passes (as shown by the curved arrows) on the open side of the LED board (part of the channel that is not occupied by the UV-LED board) and through the photocatalyst structures. This configuration may cause photoreactions and photocatalytic reactions in the fluid. The arrows show the overall direction of the fluid flow mowing through the UV-LEDs and photocatalyst structures. 
         [0068]    In the UV-LED reactor configurations presented in  FIG. 9  and  FIG. 10 , the fluid flow and the photocatalyst structures may be irradiated by UV-LEDs from one or both sides; this means that UV-LEDs may be mounted on either side of the LED board. Further, in both configurations presented in  FIG. 9  and  FIG. 10 , static mixers (not shown) may be used to enhance the fluid flow hydrodynamics. 
         [0069]    The UV-LED reactors described in  FIGS. 1 to 10  may have any shape of the flow channel cross section, such as a circle, a semi-circle, a square, a rectangle, a triangle, a trapezoid, a hexagon, or any suitable shape. These flow cross sections may enhance the reactor performance by improving the reactor hydrodynamics and/or radiation distribution under certain fluid flow conditions and UV-LED radiation pattern. For example the circular cross section channel may provide optimal radiation transfer to the fluid for an UV-LED collimated radiation. 
         [0070]    Referring now to  FIG. 11 , there is shown partially-diagrammatic perspective view of a UV-LED reactor applied to water treatment  200 , having an inlet pipe  201 , an outlet pipe  202 , a UV-LED reactor  203 , operating with UV-LEDs  204 , and a water tap  205 . The water enters the reactor from inlet  201 , passes through the UV-LED reactor  203 , and is irradiated by UV radiation emitted form the UV-LEDs  204  for treatment, prior to exiting from outlet pipe  202  and going to the tap  205  for general use. The general fluid flow directions are shown by the arrows. 
         [0071]    Referring now to  FIG. 12 , there is shown partially-diagrammatic perspective view of a refrigerator containing a UV-LED reactor  210 , having a body  211 , a UV-LED reactor  212 , a pipe  213 , and a water/ice dispenser  214 . The water flowing in the pipe  213  passes through the UV-LED reactor  212  for treatment prior to entering the water/ice dispenser  214 . The refrigerator is illustrated as an example of appliances. The general fluid flow directions are shown by the arrows. 
         [0072]    Referring now to  FIG. 13 , there is shown partially-diagrammatic perspective view of a hemodialysis machine containing a UV-LED reactor  220 , having a body  221 , a UV-LED reactor  222 , and a pipe  223 . The water flowing in the pipe  223  passes through the UV-LED reactor  222  for treatment prior to use in the hemodialysis machine. The hemodialysis machine is illustrated as an example of healthcare devices. 
         [0073]    The construction details of the invention, as shown in  FIG. 2  to  FIG. 10 , are that the UV-LED reactor housing may be made of aluminum, stainless steel, or of any other sufficiently and strong material, such as metal, alloy, high-strength plastic, or the like. The various components of the UV-LED reactor may also be made of different materials. Further, UV-LEDs of different peak wavelengths may be used to cause synergistic effects to enhance the photoreaction efficiency. Further, a combination of different configuration concepts, which include the concepts presented in  FIG. 2  to  FIG. 10 , may be used. For example, static mixers may be used with photocatalysts. 
         [0074]    The advantages of the present invention include, without limitation, that it is an efficient compact UV-LED reactor that can be applied to any UV-activated photoreaction or photocatalytic reaction. One of these applications is water purification by UV-inactivation of microorganisms and UV-based degradation of chemical contaminants. Further, the reactor concept presented in this invention, which can be optimized based on a combination of UV-LED radiation patterns and the flow field hydrodynamics, provides superior UV dose delivery to the fluid. Further, the reactor configurations of the present invention make the design of a small UV reactor with all-integrated components possible. Other advantages of the UV-LED reactor of the present invention include a robust design, lower voltages and power requirements, as well as the ability to turn on/off automatically and with high frequency. These features can result in the application of this UV-LED reactor concept to conditions in which UV-Lamp reactors cannot be used effectively. Further, the UV reactor concept can be applied to both UV photo reactors and photocatalytic reactors for water purification. 
         [0075]    Further advantages of the present invention are that it is a simple and efficient water disinfection device suitable for processing low to moderate flow rates of water—ideally suited for point-of-use applications. Further, due to its compact configuration and high efficiency, the UV-LED reactor of the present invention may be incorporated in appliances, particularly refrigerators, freezers, water coolers, coffee machines, or any other kind of water dispenser or icemaker. Further, the UV-LED reactor of the present invention may be incorporated in healthcare facilities or medical devices using water for operation and/or cleaning, such as hemodialysis machines. 
         [0076]    In broad embodiment, the present invention is an efficient and compact UV-LED reactor, which is applicable to a range of photoreactions and photocatalytic reactions in a fluid, including a UV-based water treatment. 
         [0077]    While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope and spirit of the invention as claimed.