Methods and apparatus for controlling radiation dose to fluids in UV-LED photoreactors

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 proportionally to the fluid velocity in the cross section of the conduit.

TECHNICAL FIELD

The present invention relates to ultraviolet (UV) photoreactors, and more particularly, to a UV reactor operating with ultraviolet light emitting diodes (UV-LEDs). Particular embodiments provide methods and apparatus for controlling the delivery of radiation dose to fluids moving through UV-LED photoreactors.

BACKGROUND

Ultraviolet (UV) reactors—reactors that administer UV radiation—are applied to many photoreactions, photocatalytic reactions, and photo-initiated reactions. One application for UV reactors is for water and air purification. In particular, UV reactors have emerged in recent years as one of the most promising technologies for water treatment. Prior art UV reactor systems typically use low- and medium-pressure mercury lamps to generate UV radiation.

Light emitting diodes (LEDs) typically emit radiation of such narrow bandwidth that radiation emitted by LEDs may be considered (for many applications) to be monochromatic (i.e. of a single wavelength). With recent advances in LED technology, LEDs may be designed to generate UV radiation at different wavelengths, which include wavelengths for DNA absorption as well as wavelengths that can be used for photocatalyst activation.

UV-LED reactors may generally be used for irradiating fluids, with applications such as water disinfection. However, in a typical UV-LED reactor, there is considerable variation of the radiant power distribution, resulting in uneven radiant fluence rate distribution, which may be quite significant in some cases. Fluence rate (in W/m2) is the the radiant flux (power) passing from all directions through an infinitesimally small sphere of cross-sectional area dA, divided by dA. Further, there is typically variation in the fluid velocity distribution, causing a residence time distribution of fluid in the reactor. Either of these two phenomena of fluence rate distribution and velocity distribution, or a combination of these two phenomena, may result in a considerably wide range of UV dose distribution of fluid elements, as it passes through the reactor. The variation in UV fluence rate distribution and velocity distribution (the velocity distribution being related to residence time distribution) may cause part of the fluid to traverse a UV reactor without receiving sufficient UV dose (a product of UV fluence rate and residence time), which is a known issue in the field of UV reactors and may be referred to as “short-circuiting”. Short-circuiting can have a significantly unfavorable impact on the performance of a UV reactor.

SUMMARY

One aspect of the invention provides a UV-LED reactor with precise control of both the fluidic and optical environments. The UV-LED reactor may advantageously provide high and uniform radiation exposure to a fluid flow at a small footprint, and may advantageously provide for a more efficient and compact UV-LED reactor than at least some prior art reactors. The UV-LED reactor may be incorporated into devices for various UV photoreaction applications, including, for example, UV-based water treatment and/or the like (as explained in further detail below).

One aspect of the present invention provides an ultraviolet (UV) reactor comprising a fluid conduit for transporting fluid flow; a solid-state UV emitter (e.g. ultraviolet light emitting diode or UV-LED); and a radiation-focusing element comprising one or more lenses. The fluid conduit may comprise a fluid inlet and a fluid outlet and a longitudinally extending fluid flow channel located between the inlet and the outlet, the fluid flow channel extending in a longitudinal direction for permitting a flow of fluid in a longitudinal direction therethrough. The one or more lenses may be positioned in a radiation path of radiation emitted from the solid-state UV emitter for directing radiation from the solid-state UV emitter to impinge on the fluid flowing in the fluid flow channel. The one or more lenses may be configured to provide an average, over a longitudinal dimension of the fluid flow channel, radiation fluence rate profile over a portion of a cross-section of a bore of the fluid flow channel which is positively correlated with an average, over the longitudinal dimension of the fluid flow channel, longitudinal direction fluid velocity profile over the portion of the cross-section of the bore of the fluid flow channel. The one or more lenses may be configured, by one or more of selection of the one or more lenses from among a variety of lens types, shape of the one or more lenses, position of the one or more lenses and indices of refraction of the one or more lenses, to provide the average, over the longitudinal dimension, radiation fluence rate profile over the portion of the cross-section which is positively correlated with the average, over the longitudinal dimension, longitudinal direction fluid velocity profile over the portion of the cross-section.

The radiation-focusing element may comprise a focusing lens or a combination of two or more focusing lenses disposed proximate to the solid-state UV emitter. The focusing lens(es) may comprise a converging lens, a diverging lens, a collimating lens, or any combination of a collimating lens, a converging lens, a diverging lens or any other type of lens. In some embodiments, the focusing lenses may comprise a converging lens optically adjacent to the UV emitter and a collimating lens at some suitable distance away from the converging lens.

For example, at any cross-sectional location within the portion of the cross-section of the bore of the fluid flow channel, embodiments of the technology provide an average, over the longitudinal dimension, radiation fluence rate which may be higher where the average, over the longitudinal dimension, longitudinal direction fluid velocity is higher, and lower where the average longitudinal direction fluid velocity is lower—i.e. a positive correlation between the average radiation fluence rate and the average longitudinal direction velocity. For example, at any location within the portion of the cross-section of the bore of the fluid flow channel, embodiments of the technology provide an average, over the longitudinal dimension, radiation fluence rate which may be relatively high at the center of the bore of the fluid flow channel, where the average, over the longitudinal dimension, longitudinal direction fluid velocity may be higher, and relatively low near the edges of the bore of the fluid flow channel or at other locations spaced apart from the center of the cross-section, where the average, over the longitudinal dimension, longitudinal direction fluid velocity may be lower. In general, the positive correlation between the average radiation fluence rate and the average longitudinal direction velocity is not limited to situations where the average longitudinal direction velocity is higher at the center of the cross-section and suitable configuration of lens(es) may be used to establish this positive correlation for other average longitudinal direction velocity cross-sectional profiles. In some embodiments, it may be desirable for this positive correlation between the average radiation fluence rate and the average longitudinal direction fluid velocity within the portion of the cross-section of the bore of the fluid flow conduit to be a general proportionality of the average radiation fluence rate to the average longitudinal direction fluid velocity. In some embodiments, this proportionality of the average radiation fluence rate to the average longitudinal direction fluid velocity within the portion of the cross-section of the bore of the fluid flow channel need not be an exact proportionality, but instead may be proportional in a manner which has a proportionality constant that varies less than +/−50% over the portion of the cross-section. In some embodiments, this proportionality constant varies less than +/−25%. In some embodiments, this proportionality constant varies less than +/−15%. In some embodiments, this proportionality constant varies less than +/−10%. The portion of the cross-section of the bore of the fluid flow channel over which the aforementioned proportionality exists may be greater than 50% of the total cross-sectional area of the bore of the fluid flow channel in some embodiments, may be greater than 75% of the total cross-sectional area of the bore of the fluid flow channel in some embodiments, and may be greater than 85% of the total cross-sectional area of the bore of the fluid flow channel in some embodiments.

Further, for any specific radiation fluence rate profile within a portion of a cross-section of a bore of the longitudinally extending fluid flow channel, one or more flow-restraining elements may be deployed in the fluid flow channel to restrain the fluid flow in the bore of the longitudinally extending fluid flow channel and may be shaped and/or positions for providing the average (over the longitudinal dimension) longitudinal direction velocity profile over the portion of the cross-section of the bore of the longitudinally extending fluid flow channel which is positively correlated with an average (over the longitudinal dimension) radiation fluence rate profile over the portion of the cross-section of the bore of the longitudinally extending fluid flow channel.

For example, for a particular case where the average radiation fluence rate is relatively high at a center of the cross-section of the bore of the fluid flow channel, a ring baffle having an aperture at the center can be deployed with the aperture at the cross-sectional center of the bore to provide relatively high average longitudinal direction velocity at the center of the cross-section of the bore of the fluid flow channel, where the average radiation fluence rate is higher, and relatively low average longitudinal direction velocity near the edges of the cross-section of the bore of the fluid flow channel, where the average radiation fluence rate is lower. The baffle shape and/or position can be adjusted to provide an average longitudinal direction velocity distribution that is positively correlated with the average radiation fluence rate distribution over a portion of the cross-section of the bore of the fluid flow channel (in which the aforementioned proportionality exists). In some embodiments, it may be desirable for this positive correlation between the average longitudinal direction fluid velocity and the average radiation fluence rate within the portion of the cross-section of the bore of the fluid flow conduit to be a general proportionality of the average longitudinal direction fluid velocity to the average radiation fluence rate. In some embodiments, this proportionality of the average longitudinal direction fluid velocity to the average radiation fluence rate within the portion of the cross-section of the bore of the fluid flow channel need not be an exact proportionality, but instead may be proportional in a manner which has a proportionality constant that varies less than +/−50% over the portion of the cross-section. In some embodiments, this proportionality constant varies less than +/−25%. In some embodiments, this proportionality constant varies less than +/−15%. In some embodiments, this proportionality constant varies less than +/−10%. The portion of the cross-section of the bore of the fluid flow channel over which the aforementioned proportionality exists may be greater than 50% of the total cross-sectional area of the bore of the fluid flow channel in some embodiments, may be greater than 75% of the total cross-sectional area of the bore of the fluid flow channel in some embodiments, and may be greater than 85% of the total cross-sectional area of the bore of the fluid flow channel in some embodiments.

The baffle (or other flow-restraining element(s)) may be static. The baffle (or other flow-restraining element(s)) may also be adjusted dynamically to accommodate various incoming flow regimes to match the UV radiation fluence rate profile in the fluid flow channel. For example, a baffle's angle relative to the longitudinal direction of the fluid flow may be changed by rotating it around a pivot; or its longitudinal and/or transverse dimension(s) can be adjusted by sliding suitable adjustment of extendable portion(s) of the baffle.

In some embodiments, the reactor may comprise an array of longitudinally extending fluid flow channels, any number of which may comprise properties similar to the longitudinally extending fluid flow channel described herein. In some embodiments, each such fluid flow channel can be irradiated by one or more corresponding solid state UV emitters through a corresponding radiation-focusing element. The corresponding solid state UV emitters and/or the corresponding radiation-focusing elements may be positioned at longitudinal ends of their corresponding longitudinally-extending fluid flow channels so that a direction of irradiation is generally parallel to, (and in the direction of and/or opposing the direction of) the fluid flow (i.e. in longitudinal directions). The reactor may comprise a plurality of UV-LEDs that emit different UV wavelengths. The reactor may comprise a photocatalyst supported on a structure in the reactor. The reactor may comprise 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 one or more components to restrain the fluid flow in the conduit, such as static mixers, vortex generators, baffles and/or the like.

In another aspect, the present invention provides a method of attaining UV photo reaction or UV photo-initiated reaction in a fluid flow through a conduit comprising a fluid inlet and a fluid outlet and a longitudinally extending fluid flow channel located between the inlet and the outlet, the fluid flow channel extending in a longitudinal direction for permitting a flow of fluid in a longitudinal direction therethrough. This is accomplished by causing the fluid flow in the longitudinal direction through the longitudinally extending fluid flow channel; positioning a radiation-focusing element comprising one or more lenses in a radiation path of at least one solid-state UV emitter; and positioning the one or more lenses such that the focused radiation from the solid state UV emitter is directed to impinge (e.g. in the longitudinal direction) on the longitudinally flowing fluid in the longitudinally extending fluid flow channel. The method may comprise configuring the one or more lenses to provide an average, over a longitudinal dimension of the fluid flow channel, radiation fluence rate profile over a portion of a cross-section of a bore of the fluid flow channel which is positively correlated with an average, over the longitudinal dimension of the fluid flow channel, longitudinal direction fluid velocity profile over the portion of the cross-section of the bore of the fluid flow channel. Configuring the one or more lenses may comprise selecting the one or more lenses from among a plurality of lens types, shaping the one or more lenses, positioning the one or more lenses and fabricating the one or more lenses from materials having indices of refraction. In some embodiments, it may be desirable for this positive correlation between the average radiation fluence rate and the average longitudinal direction fluid velocity within the portion of the cross-section of the bore of the fluid flow conduit to be a general proportionality of the average radiation fluence rate to the average longitudinal direction fluid velocity. The relationship between the average radiation fluence rate profile and the average longitudinal direction fluid velocity profile within the portion of the cross-section of the bore of the fluid flow channel over which the aforementioned proportionality exists may have any of the properties described above or elsewhere herein. A photocatalyst may be used to promote photocatalytic reactions in the fluid. A UV-reactive chemical reagent may be used to promote photo-initiated reactions.

In yet another aspect, the present invention provides a method for the treatment of a fluid, such as water or air, the fluid flowing through a conduit comprising a fluid inlet and a fluid outlet and a longitudinally extending fluid flow channel located between the inlet and the outlet, the fluid flow channel extending in a longitudinal direction for permitting a flow of the fluid therethrough in the longitudinal direction. This is accomplished by causing the fluid flow in the longitudinal direction through the longitudinally extending fluid flow channel; positioning a radiation-focusing element in a radiation path of at least one UV light emitting diode (UV-LED); and configuring (e.g. selecting, shaping, positioning, fabricating from materials with suitable index of refraction and/or the like) the radiation-focusing element such that focused radiation from the UV-LED is directed to impinge (e.g. in the longitudinal direction) on the longitudinally flowing fluid in the longitudinally extending fluid flow channel. The radiation-focusing element may comprise one or more lenses which may be configured (e.g. selected, positioned, shaped, fabricated from materials with suitable index of refraction and/or the like) for providing an average (over a longitudinal dimension of the longitudinally extending fluid flow channel) radiation fluence rate profile within a portion of a cross-section of a bore of the longitudinally extending fluid flow channel which is positively correlated with the average (over the longitudinal dimension of the longitudinally extending fluid flow channel) longitudinal direction fluid velocity profile within the portion of the cross-section of the bore of the longitudinally extending fluid flow channel. In some embodiments, it may be desirable for this positive correlation between the average radiation fluence rate and the average longitudinal direction fluid velocity within the portion of the cross-section of the bore of the fluid flow conduit to be a general proportionality of the average radiation fluence rate to the average longitudinal direction fluid velocity. The relationship between the average radiation fluence rate profile and the average longitudinal direction fluid velocity profile within the portion of the cross-section of the bore of the fluid flow channel over which the aforementioned proportionality exists may have any of the properties described above or elsewhere herein. The microbial and chemical contaminants in the fluid flow may be inactivated and/or eliminated while the ultraviolet radiation is emitted into the fluid flow.

The efficiency of a UV reactor may be 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 comprises, or is related to, the incident radiant power (as the integral of the radiant power passing from all directions through an infinitesimally small sphere of cross-sectional area dA divided by dA), and the exposure time. The fluence rate in a UV reactor may be controlled by adjusting the UV-LED radiant power profile in the reactor, while the exposure time may be controlled by adjusting the reactor hydrodynamics of the fluid moving through the reactor. The UV-LED reactor of some embodiments of the present invention provides high reactor performance through its precise control of both the radiant power profile and the hydrodynamics of the fluid moving through the reactor. Further, the UV-LED reactor of some embodiments of the present invention may improve efficiency by increasing uniformity in UV dose (fluence) distribution to the fluid being treated in the reactor and by delivering the majority of UV radiation directly to the fluid, instead of losing the UV radiant energy to the reactor wall(s).

In one variation, an aspect of the present invention provides a reactor operating with one or more ultraviolet light emitting diodes (UV-LEDs) to cause photoreactions or photo-initiated reactions in a fluid. The UV-LED reactor comprises a single or series of longitudinally extending flow channels (conduit, tube) through which fluid flows in corresponding longitudinal direction(s), which is irradiated, either with one UV-LED, or with an array of UV-LEDs. The reactor may comprise a single longitudinally extending fluid flow channel, a series of parallel fluid flow channels, or a stack of multiple fluid 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 in fluid communication at their ends). The fluid may flow mainly in the longitudinal direction of the longitudinally extending channels. The UV-LED radiation is focused via a radiation-focusing element, such as one or more converging lenses, one or more collimating lenses, or a combination of one or more converging lenses and one or more collimating lenses. In some embodiments, the focusing element may comprise a converging lens optically adjacent to the UV emitter and a collimating lens at some suitable distance away from the converging lens. The fluid flowing in the longitudinal directions in the reactor channels is irradiated by the focused radiation from the UV-LEDs in the longitudinal directions of the channels. The LEDs may be positioned at one or both ends of the flow channels. The total UV dose (UV fluence) delivered to a fluid may be controlled by adjusting the fluid flow rate and/or regulating UV-LED radiant power, and/or turning on/off the number of UV-LEDs. The reactor configuration according to some embodiments of the present invention facilitates the design and fabrication of an efficient and compact UV reactor with all-integrated components.

In some embodiments of the present invention, the radiation-focusing element comprises one or more focusing lenses, such as one or more collimating lenses or one or more converging lenses, disposed proximate to the UV-LED. Each 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 one or more collimating lenses and one or more converging lenses may be used in some embodiments. The radiation-focusing element may be adjusted to provide higher fluence rate at the center of the bore of the longitudinally extending flow channel, where the fluid typically has a higher velocity (and lower residence time) and lower fluence rate near the channel wall (the edges of the bore), where the fluid typically has a lower velocity (and higher residence time). As a result, by the time that the fluid leaves the reactor or the longitudinally extending fluid flow channel, each component of the fluid has received similar or comparable UV dose. In practice, one way that this could be achieved is using one or more focusing lenses as the radiation-focusing element (for example a converging lens or a combination of a converging lens and a collimating lens that is not necessarily positioned in its focal length distance with respect to the radiation source) to focus the radiation fluence rate in the channel based on the velocity profile. This particular configuration of the UV-LED reactor, which involves adjusting the UV-LED radiation in accordance to the velocity profile, may result in a more effective utilization of UV-LED radiant power and improves reactor performance.

To explain the concept of average radiation fluence rate proportional to the average fluid velocity, here we provide a non-limiting example. For a cylindrical fluid flow channel (i.e. having a bore with a circular cross section), the velocity profile of the fluid may be an elliptic paraboloid (a three-dimensional parabolic shape); with a radius r corresponding to the radius R of the channel cross-section. If the length of the longitudinally extending flow channel is 0.2 m and the average (over the longitudinal length of the flow channel) velocity at the center of the cross section of the channel bore (r=0) is 0.2 m/s, the residence time (in the longitudinally extending fluid flow channel) of the fluid that moves at r=0 is 1 s. If we assume that the average velocity at r=0.5R is 0.1 m/s, for example, then the residence time (in the longitudinally extending fluid flow channel) of the fluid that moves at r=0.5R is 2 s. Since UV dose (UV fluence) is a product of residence time (exposure time) multiplied by UV fluence rate, to make both the part of the fluid moving at r=0 and at r=0.5R to receive the same dose, it would be desirable for the radiation fluence rate to be adjusted so that at r=0, the average (over the longitudinal length of the flow channel) radiation fluence rate is approximately twice the value of that at r=0.5R. For instance, if the fluence rate at r=0 is 2 mJ/cm2, its value at r=0.5R is 1 mJ/cm2. This is particularly advantageous where there is minimal cross-sectional (e.g. radial) mixing of the fluid. Adjusting the radiation fluence rate to be exactly proportional to the velocity profile may not always be easily attainable or practical. In some embodiments, it is sufficient for the average longitudinal direction fluid velocity to the average radiation fluence rate to be positively correlated over a suitable portion of the surface area of the cross-section of the bore of the fluid flow channel (or a suitable portion of the volume of the bore of the fluid flow channel). The portion of the cross-section of the bore of the fluid flow channel, for which the positive correlation of velocity and fluence rate exist, may be greater than 50% of the total cross-section of the bore of the fluid flow channel in some embodiments, may be greater than 75% of the total cross-section of the bore of the fluid flow channel in some embodiments and may be greater than 85% of the total cross-section of the bore of the fluid flow channel in some embodiments. The proportionality of the average longitudinal direction fluid velocity to the average radiation fluence rate within the portion of the cross-section of the bore of the fluid flow channel need not be an exact proportionality, but instead may be proportional in a manner which has a proportionality constant that varies less than +/−50% over the portion of the cross-section. In some embodiments, this proportionality constant varies less than +/−25%. In some embodiments, this proportionality constant varies less than +/−15%. In some embodiments, this proportionality constant varies less than +/−10%. In some embodiments, however, tolerance levels within +/−50% of the fluence rate may be suitable. For instance, for the example described above the fluence rate at r=0.5R could be between 0.75 mJ/cm2and 1.25 mJ/cm2.

To explain the foregoing concepts in an alternate way: if the velocity profile of a fluid in cross-section of the bore of the channel, when averaged over the longitudinal length of the channel, has the shape of an elliptic paraboloid (a quadratic surface which has elliptical cross section), of height h, semi major axis a, and semi minor axis b (a and b will be the same for a circular cross section), the average UV fluence rate (averaged over the length of the longitudinally extending channel) at any cross-section of the bore of the channel will have the same shape of an elliptic paraboloid with the same h, a, and b parameters. Since a perfect match is not likely to be easily attainable or practical, a threshold of +/−50% of the perfect match values may be applied for the fluence rate values. The proportionality of the average longitudinal direction fluid velocity to the average radiation fluence rate within the portion of the cross-section of the bore of the fluid flow channel need not be an exact proportionality, but instead may be proportional to in a manner which has a proportionality constant that varies less than +/−50% over the portion of the cross-section. In some embodiments, this proportionality constant varies less than +/−25%. In some embodiments, this proportionality constant varies less than +/−15%. In some embodiments, this proportionality constant varies less than +/−10%. This proportionality of the average fluence rate and the average velocity may be true over a portion of the cross-section of the bore of the longitudinally extending fluid flow channel. Such portion of the cross-section of the bore of the fluid flow channel may be greater than 50% of the total cross-section of the bore of the fluid flow channel in some embodiments, may be greater than 75% of the total cross-section of the bore of the fluid flow channel in some embodiments and may be greater than 85% of the total cross-section of the bore of the fluid flow channel in some embodiments.

Residence time for fluid (in a reactor or a portion of the reactor) is defined as the time that the fluid spends (inside of the reactor or the portion of the reactor) while being irradiated. Given the velocity profile within any fluid flow conduit, usually each part of the fluid spends a different amount of time in the reactor and, as a result, different parts of the fluid have different residence times in the reactor (there is a residence time distribution that can be averaged to calculate the average residence time). Part of the fluid that travels mainly at the center of a channel typically has a higher velocity and therefore shorter residence time in the channel.

The UV-LED reactor of the present invention may be used for many photoreactions, photocatalytic reactions, and photo-initiated reactions. One particular application is the purification of water or purification of other UV-transparent fluids.

Some aspects of the invention provide UV-LED reactors for treating water and methods for using UV-LED reactors to treat water. These UV-LED reactors and corresponding methods may have features similar to those described above or elsewhere herein. 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, 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 may be powered by a wall plug or a battery. If applicable, a photocatalyst may be immobilized on a solid substrate, where the fluid passes over, and/or on a perforated substrate where the fluid passes through, including for example a mesh, screen, metal foam, cloth or combination thereof. The photocatalysts that are supported on the solid and/or perforated substrates may be positioned in the longitudinally extending fluid flow channels. The photocatalyst may also be positioned in the cross section of the fluid flow channel, to cover the cross section partially or entirely. If the photocatalyst covers the entire cross section of the flow channel, a perforated substrate may be used to allow for the fluid to pass through the photocatalyst substrate. The photocatalyst is irradiated with focused UV radiation from the UV-LED, providing a UV-LED photocatalytic reactor. The photocatalyst may comprise titanium dioxide TiO2, or any other photocatalyst. In certain embodiments, a combination of one or more photocatalysts, catalyst supports and co-catalysts are provided on the solid and/or perforated substrate(s). If applicable, chemical reagents, such as chemical oxidants may be injected into the UV reactor. The chemical oxidant may comprise hydrogen peroxide H2O2, ozone O3, or other chemicals.

In some applications of the UV-LED reactor described herein, the UV-LED reactor may be used to treat water in point-of-use applications, particularly in low to moderate flow applications. For example, the UV-LED reactor may be incorporated into appliances that dispense or use water or water-based fluids (e.g. coffee or other beverages) for human consumption. Such appliances may include refrigerators, freezers, ice machines, frozen beverage machines, water coolers, coffee makers, vending machines and the like. Other applications of the UV-LED reactor described herein include the treatment of water used in healthcare-related devices. Such devices may include, for example, hemodialysis machines, colon hydrotherapy equipment, or the like. The UV-LEDs of the reactor which are incorporated into any one of the aforementioned appliances or devices may be turned on and off automatically as the water starts or stops flowing, to treat the water used in or dispensed from the appliances or devices. The UV-LED reactor reduces the microbial contamination in the water leaving the waterline (for consumption or use) and reduces the risk for infection. The UV-LED reactor may be integrated in these devices along with other forms of water purification methods such as filtration and the like.

In some embodiments, static mixers, vortex generators, baffles, or the like may be deployed in the longitudinally extending fluid flow channels to increase mixing and/or to rotate the flow as it goes through the fluid flow channels. This may enhance the UV-LED reactor performance by delivering a more uniform UV dose or by improving mass transfer near the photocatalyst surface where photocatalysts are presents in the reactor. The static mixers, vortex generators, baffles or the like may also serve as flow-restraining elements which may be adjusted dynamically to accommodate various incoming flow regimes to match the UV radiation fluence rate profile in the fluid flow channel as described herein.

In some embodiments, the reactor comprises a plurality of UV-LEDs that emit different UV wavelengths. This may result in a synergistic effect and increase the rate of photoreactions and photocatalytic reactions.

Some embodiments comprise UV-LEDs which are operated in a pulsed mode. For example the LEDs may be pulsed at high frequencies. This mode of operation may affect the photoreaction rate as well as the photocatalyst's electron-hole recombination so as to increase photocatalytic efficiencies.

The UV-LEDs may be programmed to turn on and off automatically in some embodiments. For example it may be desirable to turn on/off the UV-LEDs as the fluid flow starts or stops moving in the reactor (which may be useful for water purification in point-of-use applications), or at specific time intervals. To control the UV-LEDs' on/off status, a sensor may be used to detect the fluid motion in the fluid flow channels. Alternatively, a user may activate a sensor physically, either directly (for example, by turning a switch on and off), or as an indirect action (for example through turning the tap on and off). This feature may advantageously save energy used by the reactor. As another example, it may be desirable to turn on/off the UV-LEDs at specific time intervals for cleaning of the UV reactor chamber when it is not in operation for some time, in order to prevent any potential growth of microorganisms, diffusion of microorganisms from untreated upstream fluid, and/or to prevent any biofilm formation. To control the UV-LEDs' on/off status, a microcontroller may be applied and programmed to turn the UV-LEDs on for a time period (for example, a few seconds), at specific time intervals (for example, once every few hours).

In some embodiments, at least some of the UV-LEDs may be programmed to adjust their power output or to turn on or off automatically, in response to receiving a signal. The signal may be generated, for example, as the flow rate (or other measurable characteristic) of the fluid passing through the UV-LED reactor changes. In embodiments where the fluid is water, the measurable characteristic may be one that is indicative of the water quality or concentration of contaminants. Examples of water quality indicators include UV transmittance and turbidity. This configuration may facilitate appropriate radiation energy being directed to the fluid based on the particular operating conditions.

In some embodiments, a visual indicator, such as for example a liquid crystal display (LCD) or a light signal (such as a colored LED) may be provided on the UV-LED reactor, or in another visible place (for example, on the tap if the application is water treatment) to inform the user of the status of the reactor and UV-LEDs. As an example, when the UV-LEDs are on, a sign on the LCD can be displayed or a colored LED can be turned on which indicates the “on” status of the UV-LEDs to the user.

To increase or maintain the lifespan of the UV-LEDs, the fluid flowing through the fluid flow channels may be used for the thermal management of the UV-LEDs by transferring the heat generated by the LEDs. The UV reactor may be configured so that part of the fluid is circulated in the proximity of the UV-LEDs or the UV-LED circuit board, and/or by incorporating thermally conductive material in the walls of the fluid flow channels.

DESCRIPTION

The present technology is directed to a reactor (photoreactor) operating with one or more solid-state UV emitters (e.g. ultraviolet light emitting diodes or UV-LEDs, thin dielectric films that emit UV, and the like), which emit UV radiation to cause photoreactions in a fluid. One or more photocatalyst structures, activated by UV, may be used in the photoreactor for photocatalytic reactions. Chemical oxidants may also be added to the reactor to react with the UV radiation and generate highly active radicals such as hydroxyl radicals for photo-initiated oxidation reactions. Embodiments of the UV-LED reactors described herein may be efficient and compact, with integrated components, and may offer precise control of both their fluidic and optical environments. The UV-LED reactors comprise one or more specifically designed flow channels and an array of UV LEDs configured for irradiating the fluid flowing through the flow channels. Radiation-focusing elements may be integrated in or disposed near the UV LEDs and may be configured (e.g. by suitable selection of lens(es) (e.g. from among a plurality of lens types, construction methods and/or the like), positioning (including orientation) of lens(es), shaping (including sizing) of lens(es), fabrication of lens(es) from materials with suitable indices of refraction and/or the like) to focus the UV radiation emitted by the UV LEDs to provide an average (over the longitudinal dimension of the longitudinally extending fluid flow channel) radiation fluence rate profile over a cross-section of a bore of the longitudinally extending fluid flow channel (or a portion thereof) which is positively correlated with an average (over the longitudinal dimension of the longitudinally extending fluid flow channel) longitudinal direction fluid velocity profile within the cross-section of the bore of the longitudinally extending fluid flow channel (or the portion thereof). In some embodiments, this positive correlation may comprise an average (over the longitudinal dimension of the longitudinally extending fluid flow channel) radiation fluence rate profile within the cross-section of the bore of the longitudinally extending fluid flow channel (or the portion thereof) which is generally proportional to an average (over the longitudinal dimension of the longitudinally extending fluid flow channel) longitudinal direction fluid velocity profile within the cross-section of the bore of the longitudinally extending fluid flow channel (or the portion thereof). While these parameters (radiation fluence rate and fluid velocity) may exhibit these features (positive correlation and/or general proportionality) when averaged over a longitudinal dimension of the fluid flow channel, in some embodiments, these parameters (radiation fluence rate and fluid velocity) may exhibit these features (positive correlation and/or general proportionality) at each cross-section over a portion of the longitudinal dimension of the fluid flow channel. The UV-LED reactor may comprise baffles, vortex generators, static mixers, or the like (e.g. other flow-restraining elements), to alter the hydrodynamics of the flow, thereby enhancing the performance of the UV-LED reactor. In particular, the baffles, vortex generators, or static mixers may be adjusted dynamically to accommodate various incoming flow regimes to correlate positively with the UV radiation fluence rate profile in the fluid flow channel.

Embodiments of the UV-LED reactor may be used for water purification by inactivating microorganisms (e.g. bacteria, viruses and/or the like) and/or degrading micro-pollutants such as chemical contaminants (e.g. toxic organic compounds and/or the like) by direct photoreaction, and/or photocatalytic reactions, and/or photo-initiated oxidation. The fluid (e.g., water) flows through the UV-LED reactor by forced convection, using, for example, electrical pumps. The UV-LEDs may be powered by wall plug, solar cells, or battery. The UV-LEDs may be turned on and off automatically as the fluid flows or stop flowing. A photocatalyst such as titanium dioxide TiO2or other suitable photocatalyst may be immobilized on a solid substrate (where the fluid passes over the substrate) or on a perforated substrate (where the fluid passes through the substrate). In some embodiments, a combination of photocatalysts, catalyst supports, and/or co-catalysts may be disposed in the substrate in the fluid flow channel. If applicable, chemical oxidants may additionally or alternatively be injected into the reactor. The chemical oxidant may comprise hydrogen peroxide H2O2or ozone O3or other chemicals. If applicable, chemical reducing agents may additionally or alternatively be injected into the reactor. The chemical oxidant or chemical reducing agents may be generated in the flow upstream of the UV reactor or inside of the UV reactor by electrochemical methods or other methods.

Reactors that operate with UV-LEDs as a source of UV radiation have advantages over traditional mercury UV lamps, including, without limitation, their compact and robust design, lower voltage and power requirements, and the ability to turn on and off with high frequency. 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 (e.g. greater precision) compared to the arrangement of UV lamps. Further, the performance of UV-LED reactors may be improved with optimizations to the reactor geometry, the reactor hydrodynamics, and UV radiation distribution as described herein. In particular, embodiments of the UV-LED reactor described herein may be optimized based on a combination of UV-LED radiation patterns and the flow field hydrodynamics, thereby facilitating improved UV dose delivery to the fluid.

FIGS. 1A and 1Bare schematic side views of UV-LED collimated radiation11(FIG. 1A) and converged radiation12(FIG. 1B).FIG. 1Ashows radiant beams13emitted from an LED14after passing through a collimating lens15.FIG. 1Bshows radiant beams16emitted from an LED17after passing through a converging lens18. The arrows shown inFIGS. 1A and 1Bindicate the main direction of the radiant beams.

FIGS. 2A and 2Bshow partial side views of longitudinally extending fluid flow channels of two corresponding UV-LED reactor configurations according to exemplary embodiments.FIGS. 2A and 2Bshow the illustrated flow channels being irradiated from one of their longitudinal ends. In general, the channels of UV-LED reactors in which the longitudinally extending channels ofFIGS. 2A-2Bare deployed may be irradiated from either or both longitudinal ends of the fluid flow channel. In general, UV-LED reactors in which the longitudinally extending channels ofFIGS. 2A-2Bare deployed may comprise single channel reactors (i.e. having a single channel similar to that shown inFIGS. 2A-2B) or multiple channel reactors having a plurality of longitudinally extending channels similar to the longitudinally extending channels of theFIG. 2A or 2Breactors. 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 arrows shown inFIGS. 2A and 2Bindicate the main direction of the fluid flow which is in the same longitudinal direction in which the fluid flow channel extends.

FIG. 2Ashows the side view of a portion of a UV-LED reactor30having a longitudinally extending fluid flow channel101, and a UV-LED106, in which the fluid (not shown) is moving with a longitudinal direction velocity profile102which varies across the cross-section of the bore of the fluid flow channel101. In particular, the fluid in theFIG. 2Aembodiment has a maximum velocity (umax) at or near the center of the cross-section of fluid flow channel101and lower velocities at locations away from the center of the cross-section of fluid flow channel101. Radiation105emitted from the UV-LED106passes through a radiation-focusing element104(which may comprise one or more lenses) and is focused (at103) to impinge on fluid that is traveling in the longitudinal direction in the bore of the longitudinally extending flow channel101. Radiation-focusing element104may be configured (e.g. with lens(es) that are selected, positioned, shaped, fabricated from materials with suitable index of refraction and/or the like) to focus the radiation from UV-LED106in such a manner to provide relatively high radiation fluence rate at the center of the cross-section of the bore of the fluid flow channel101, where the fluid has a relatively high longitudinal direction velocity. Conversely, radiation-focusing element104may be configured (e.g. with lens(es) that are selected, positioned, shaped, fabricated from materials with suitable index of refraction and/or the like) to focus the radiation from UV-LED106in such a manner to provide relatively low radiation fluence rate at locations spaced apart from the center of the cross-section of the bore of the fluid flow channel101. With a suitably configured radiation focusing element104(e.g. with lens(es) that are selected, positioned, shaped, fabricated from materials with suitable index of refraction and/or the like), the average (over the longitudinal dimension of the longitudinally extending fluid flow channel101) radiation fluence rate profile across the cross-section of the bore of longitudinally extending flow channel101(or a portion thereof) can be positively correlated with, or in some embodiments generally proportional to, the average (over the longitudinal dimension of the longitudinally extending fluid flow channel101) longitudinal direction velocity fluid velocity profile within the cross-section of the bore of longitudinally extending flow channel101(or the portion thereof). Therefore, by the time that the fluid leaves the reactor (or leaves fluid flow channel101), each component of the fluid may receive similar or comparable aggregate UV radiation dose.

In practice, this may be achieved by constructing radiation-focusing element104to comprise one or more focusing lens(es) which focus the radiation into the bore of fluid flow channel101, based on the expected velocity profile of the fluid in channel101, in a manner which achieves the above described characteristics. In some embodiments, such focusing lens(es) may comprise: a converging lens18as shown inFIG. 1Band/or a collimating lens15as shown inFIG. 1Athat may not necessarily be positioned at its focal length distance with respect to the UV radiation source; however, other combinations of one or more converging lenses, diverging lenses, and/or collimating lenses may also be used) to achieve the desired radiation fluence rate profile. While only one focusing lens is shown in the illustrated embodiment ofFIG. 2A, this is for illustrative convenience only. In some embodiments, focusing element104shown inFIG. 2Amay comprise multiple lenses (including converging lenses, collimating lenses, a combination thereof and/or the like). In some embodiments (such as those described below with reference toFIGS. 7 and 8), a plurality of focusing lenses (including converging lenses, collimating lenses, a combination thereof and/or the like) may be provided as the radiation-focusing element to focus the radiation into the bore of fluid flow channel101, based on the expected velocity profile of the fluid in channel101, in a manner which achieves the above described characteristics. In the illustrated embodiment ofFIG. 2A, the radiation103inside the bore of fluid flow channel101is shown as being semi-transparent, so that the longitudinal direction velocity profile102of fluid in the bore of fluid flow channel101can be observed.

FIG. 2Bshows the side view of a portion of a UV-LED reactor40having a longitudinally extending fluid flow channel111, and a UV-LED116, in which the fluid (not shown) is moving with a longitudinal direction velocity profile112which varies across the cross-section of the bore of fluid flow channel101. In particular, the fluid in theFIG. 2Bembodiment has a maximum velocity (umax) at or near the center of the cross-section of fluid flow channel111and lower velocities at locations away from the center of the cross-section of fluid flow channel111. Comparing the illustrated embodiments ofFIGS. 2A and 2B, the fluid velocity profile of theFIG. 2Bembodiment varies by a greater relative amount across the cross-section of channel111than the variation of the fluid velocity profile of theFIG. 2Aembodiment across the cross-section of channel101. That is, in theFIG. 2Aembodiment, the difference between the maximum velocity at the center of the cross-section of channel101and the velocity at locations away from the center of the cross-section of channel101is relatively low, whereas, in theFIG. 2Bembodiment, the difference between the maximum velocity at the center of the cross-section of channel111and the velocity at locations away from the center of the cross-section of channel111is relatively high.

Similarly to theFIG. 2Aembodiments, in theFIG. 2Bembodiment radiation115emitted from the UV-LED116passes through a radiation-focusing element114(which may comprise one or more lenses) and is focused (at113) to impinge on fluid that is traveling in the longitudinal direction in the bore of the longitudinally extending flow channel111. Radiation-focusing element114may be configured (e.g. with lens(es) that are selected, positioned, shaped, fabricated from materials with suitable index of refraction and/or the like) to focus the radiation from UV-LED116in such a manner to provide higher relative radiation fluence rate at the center of the cross-section of the bore of the fluid flow channel111, where the fluid has a higher relative longitudinal direction velocity. Conversely, radiation-focusing element114may be configured (e.g. with lens(es) that are selected, positioned, shaped, fabricated from materials with suitable index of refraction and/or the like) to focus the radiation from UV-LED116in such a manner to provide lower relative radiation fluence rate at locations spaced apart from the center of the cross-section of the bore of the fluid flow channel111. With a suitably configured radiation focusing element114(e.g. with lens(es) that are selected, positioned, shaped, fabricated from materials with suitable index of refraction and/or the like), the average (over the longitudinal dimension of the longitudinally extending fluid flow channel111) radiation fluence rate profile across the cross-section of the bore of longitudinally extending flow channel111(or a portion thereof) can be positively correlated with, or in some embodiments generally proportional to, the average (over the longitudinal dimension of the longitudinally extending fluid flow channel111) longitudinal direction velocity fluid velocity profile within the cross-section of the bore of longitudinally extending flow channel111(or the portion thereof). The result of theFIG. 2Bembodiment is the same as that of theFIG. 2Aembodiment—i.e. by the time that the fluid leaves the reactor (or leaves fluid flow channel111), each component of the fluid may receive similar or comparable aggregate UV radiation dose.

In practice, this may be achieved by constructing radiation-focusing element114to comprise one or more focusing lens(es) which focus the radiation into the bore of fluid flow channel111, based on the expected velocity profile of the fluid in channel111, in a manner which achieves the above described characteristics. In some embodiments, such focusing lens(es) may comprise: a converging lens18as shown inFIG. 1Band/or a collimating lens15as shown inFIG. 1Athat may not necessarily be positioned at its focal length distance with respect to the UV radiation source; however, other combinations of one or more converging lenses, diverging lenses, and/or collimating lenses may also be used) to achieve the desired radiation fluence rate profile. While only one focusing lens is shown in the illustrated embodiment ofFIG. 2Bembodiment, this is for illustrative convenience only. In some embodiments, focusing element114shown inFIG. 2Bmay comprise multiple lenses (including converging lenses, collimating lenses, a combination thereof and/or the like). In some embodiments (such as those described below with reference toFIGS. 7 and 8), a plurality of focusing lenses (including converging lenses, collimating lenses, a combination thereof and/or the like) may be provided as the radiation-focusing element to focus the radiation into the bore of fluid flow channel111, based on the expected velocity profile of the fluid in channel111, in a manner which achieves the above described characteristics. In the illustrated embodiment ofFIG. 2B, the radiation113inside the bore of fluid flow channel111is shown as being semi-transparent, so that the longitudinal direction velocity profile112of fluid in the bore of fluid flow channel111can be observed.

FIG. 2Cshows the side view of a portion of a UV-LED reactor50having a longitudinally extending fluid flow channel121, and a UV-LED126, in which the fluid (not shown) is moving with a longitudinal direction velocity profile122which varies across the cross-section of the bore of the fluid flow channel121. In particular, the fluid in theFIG. 2Cembodiment has a maximum velocity (umax) at or near the center of the cross-section of fluid flow channel121and lower velocities at locations away from the center of the cross-section of fluid flow channel121. Radiation125emitted from the UV-LED126passes through a radiation-focusing element124(which may comprise one or more lenses) and is focused (at123) to impinge on fluid that is traveling in the longitudinal direction in the bore of the longitudinally extending fluid flow channel121. Radiation-focusing element124may be configured (e.g. with lens(es) that are selected, shaped, positioned, fabricated from materials with suitable index of refraction and/or the like) to focus the radiation from UV-LED126in such a manner to provide relatively high radiation fluence rate at the center of the cross-section of the bore of the flow channel121(where the fluid has a relatively high longitudinal direction velocity) by first converging (as a result of passing through the one or more lenses of radiation focusing element124) and then naturally diverging (once it all converges and the photons continue travelling along their paths). Conversely, radiation-focusing element124may be configured (e.g. with lens(es) that are selected, shaped, positioned, fabricated from materials with suitable index of refraction and/or the like) to focus the radiation from UV-LED126in such a manner to provide relatively low radiation fluence rate at locations spaced apart from the center of the cross-section of the bore of the fluid flow channel121. With a suitably configured radiation focusing element124(e.g. with lens(es) that are selected, positioned, shaped, fabricated from materials with suitable index of refraction and/or the like), the average (over the longitudinal dimension of the longitudinally extending fluid flow channel121) radiation fluence rate profile across the cross-section of the bore of longitudinally extending flow channel121(or a portion thereof) can be positively correlated with, or in some embodiments generally proportional to, the average (over the longitudinal dimension of the longitudinally extending fluid flow channel121) longitudinal direction velocity fluid velocity profile within the cross-section of the bore of longitudinally extending flow channel121(or the portion thereof). The result of theFIG. 2Cembodiment is the same as that of theFIG. 2Aembodiment and theFIG. 2Bembodiment—i.e. by the time that the fluid leaves the reactor (or leaves fluid flow channel121), each component of the fluid may receive similar or comparable UV aggregate radiation dose.

In practice, this may be achieved by constructing radiation-focusing element124to comprise one or more focusing lens(es) which focus the radiation into the bore of fluid flow channel121, based on the expected velocity profile of the fluid in channel121, in a manner which achieves the above-described characteristics. In some embodiments, such focusing lens(es) may comprise: a converging lens18as shown inFIG. 1Band/or a collimating lens15as shown inFIG. 1Athat may not necessarily be positioned at its focal length distance with respect to the UV radiation source; however, other combinations of one or more converging lenses, diverging lenses, and/or collimating lenses may also be used) to achieve the desired radiation fluence rate profile. While only one focusing lens is shown in theFIG. 2Cembodiment, this is for illustrative convenience only. In some embodiments, focusing element124shown inFIG. 2Cmay comprise multiple lenses (including converging lenses, collimating lenses, a combination thereof and/or the like). In some embodiments (such as those described below with reference toFIGS. 7 and 8), a plurality of focusing lenses (including converging lenses, collimating lenses, a combination thereof and/or the like) may be provided as the radiation-focusing element to focus the radiation into the bore of fluid flow channel121, based on the expected velocity profile of the fluid in channel121, in a manner which achieves the above described characteristics. In the illustrated embodiment ofFIG. 2C, the radiation123inside the bore of the fluid flow channel is shown as being semi-transparent, so that the velocity profile122of fluid in the bore of fluid flow channel121can be observed.

The velocity profile112in theFIG. 2Bembodiment differs from the velocity profile102in theFIG. 2A. InFIG. 2B, the velocity variation across the cross-section of fluid flow channel111is greater when compared to the variation in velocity of theFIG. 2Aembodiment (i.e. the variation of the fluid velocity as between the maximum velocity umaxat the center of the cross-section of the bore of the fluid flow channel111and locations spaced apart from the center of the cross-section of the bore of fluid flow channel111of theFIG. 2Bembodiment is greater than the variation of the fluid velocity as between the maximum velocity umaxat the center of the cross-section of the bore of the fluid flow channel101and locations spaced apart from the center of the cross-section of the bore of fluid flow channel101of theFIG. 2Aembodiment). As such, the radiation-focusing element114of theFIG. 2Bembodiment is configured (e.g. with lens(es) that are selected, positioned, shaped and/or fabricated from materials with suitable indices of refraction) to focus the radiation in a manner which provides significantly higher fluence rate variation across the cross-section of bore111of theFIG. 2Bembodiment, relative to the fluence rate variation of theFIG. 2Aembodiment (i.e. the variation of the radiation fluence rate as between the center of the cross-section of the bore of the fluid flow channel111and locations spaced apart from the center of the cross-section of the bore of fluid flow channel111of theFIG. 2Bembodiment is greater than the variation of the radiation fluence rate as between the center of the cross-section of the bore of the fluid flow channel101and locations spaced apart from the center of the cross-section of the bore of fluid flow channel101of theFIG. 2Aembodiment). The UV radiation in theFIG. 2Bembodiment may be significantly more focused in the center of the cross-section of the bore than at locations spaced apart from the center of the cross-section of the bore.

In comparison, in theFIG. 2Aembodiment the velocity is only moderately higher at the center of the cross-section of the bore of the fluid flow channel101. As such, the radiation-focusing element104of theFIG. 2Aembodiment is configured (e.g. with lens(es) that are selected, positioned, shaped and/or fabricated from materials with suitable indices of refraction) to provide moderately higher fluence rate variation across the cross-section of bore101of theFIG. 2Aembodiments relative to the fluence rate variation of theFIG. 2Bembodiment (i.e. the variation of the radiation fluence rate as between the center of the cross-section of the bore of the fluid flow channel101and locations spaced apart from the center of the cross-section of the bore of fluid flow channel101of theFIG. 2Aembodiment is less than the variation of the radiation fluence rate as between the center of the cross-section of the bore of the fluid flow channel111and locations spaced apart from the center of the cross-section of the bore of fluid flow channel111of theFIG. 2Bembodiment). The UV radiation of theFIG. 2Aembodiment may be moderately more focused in the center of the cross-section of the bore than at locations spaced apart from the center of the cross-section of the bore.

It is to be understood that the radiation-focusing element(s) incorporated into the embodiments of a UV-LED reactor as described herein may be configured (e.g. by suitable selection of lens(es), shaping of lens(es), positioning of lens(es) and/or fabrication of lens(es) out of materials with suitable indices of refraction) to focus the radiation in a manner which can provide relatively different magnitudes of the radiation fluence rate at different locations in the cross-section of the bore and that such radiation fluence rate variation can depend on the fluid velocity profile across the cross-section of the bore. Thus, in cases where the velocity is significantly higher in the center of the cross-section of the bore, the UV radiation may be significantly more focused in the center of the cross-section of the bore of the fluid flow channel to provide significantly greater fluence rate at the center of the cross-section of the bore of the fluid flow channel, as shown inFIG. 2Bfor example.

FIG. 3shows the side view of a portion of a UV-LED reactor60having a longitudinally extending fluid flow channel133, a UV-LED136, and a UV-transparent window135, in which the fluid (not shown) is moving with a longitudinal direction velocity profile which is shown by arrows131. The radiation emitted from the LED136has a specific radiation fluence rate profile, in the illustrated embodiment, being of relatively high fluence rate at the center of a cross-section of fluid flow channel133and relatively low fluence rate at locations away from the center of the cross-section of fluid flow channel133. A flow restraining element132is disposed in fluid flow channel133and is configured (e.g. shaped and/or the like) to provide relatively high longitudinal direction flow rate (and velocity) at the center of a cross-section of the bore of flow channel133, where the fluid is exposed to relatively high radiation fluence rate and relatively low velocity at locations spaced apart from the center of the cross-section of the bore of fluid flow channel133. Applying an appropriate shape of a flow restraining element132can result in alteration of the average (over the longitudinal dimension of flow longitudinally extending flow channel133) cross-sectional velocity profile of the longitudinally flowing fluid in the bore of the fluid flow channel133so that the average (over the longitudinal dimension of flow longitudinally extending flow channel133) longitudinal direction velocity profile across the cross-section of the bore of the flow channel133(or a portion thereof) may be positively correlated with, or in some embodiments generally proportional to, the average (over the longitudinal dimension of flow longitudinally extending flow channel133) radiation fluence rate profile across the cross-section of the bore of flow channel133(or the portion thereof). Therefore, by the time that the fluid leaves the reactor (or fluid flow channel133), each component of the fluid may receive similar or comparable UV radiation dose.

In practice, this may be achieved using a baffle or other flow restraining element132to modify the longitudinal direction velocity profile of the fluid flowing in the bore of the fluid flow channel133based on the radiation fluence rate profile. For example, if the radiation fluence rate is significantly higher at the center of the bore of fluid flow channel133than at locations away from the center of the bore, a truncated conical baffle (or nozzle)132(as shown inFIG. 3) can be applied (with its axis aligned with the longitudinally oriented channel axis) to lead the fluid more to the center of the cross-section of the bore of channel133and provide higher fluid velocity at the center of the cross-section of the bore of channel133and therefore non-uniform fluid velocity profile at the center of the cross-section of the bore of channel133. It will be appreciated that flow restraining devices having other shapes having apertures at the center of the cross-section can be used to provide higher fluid velocity at the center of the cross-section of the bore of channel133. On the other hand, if the radiation fluence rate is relatively uniformly distributed across the cross-section of the bore of channel133′, a small circular or conical baffle132′ (as shown inFIG. 3A) may be used at the center of the cross-section of the bore of channel133′ (held to the channel wall with small holders) to lead the fluid more to the edges of the cross-section of the bore of channel133′ and to thereby increase the velocity at locations away from the center of the cross-section (relative to the velocity at the cross-section), when averaged over the longitudinal length of the channel. It will be appreciated that flow restraining devices having other shapes having apertures away from the cross-sectional center can be used to provide relatively higher fluid velocity at locations away from the center of the cross-section of the bore of channel133′.

The above-described concepts may also be applied to each channel of multi-channel reactors (e.g. reactors having a plurality of longitudinally extending channels, each such channel similar to the channel shown inFIGS. 2A, 2B, 2C and 3), as described in the following. For the UV-LED reactors described in the exemplary embodiments ofFIGS. 4 to 6, the LEDs' radiation patterns may be 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 the exemplary embodiments ofFIGS. 4 to 6, are not expressly shown in the drawings, for the sake of illustrative convenience, as well as for clearer visualization of the reactor concepts.

FIG. 4andFIG. 5show a schematic perspective view (FIG. 4), a top view (FIG. 5A), and side views (FIG. 5BandFIG. 5C) of a UV-LED reactor10according to an exemplary embodiment. UV-LED reactor10comprises a housing31, longitudinally extending flow channels32with channel walls37for conveying fluid (e.g., water) in longitudinal directions therethrough, an inlet33for the fluid to enter and an outlet34for the fluid to exit, one or more UV-LEDs35placed in LED housing38, and a UV-transparent window36, such as a quartz window, disposed between LED housing38and flow channels32. UV-LEDs35may be mounted on a printed circuit board (not shown). As will be appreciated by those skilled in the art, UV-LED reactor10may comprise one or more heat sinks, drive circuits for UV-LEDs35, microcontrollers and other electronic mechanisms, a power port, and an on/off switch. For the sake of illustrative simplicity, these components are not shown inFIGS. 4 and 5. One or more lenses (not expressly shown inFIGS. 4 and 5), including collimating, converging, and/or other lenses, or a combination thereof, may be disposed in the reactor10between UV-LEDs35and fluid flow channels32to focus the UV-LED radiation pattern into each of longitudinally extending flow channels32. Each pair of interior adjacent flow channels32is in fluid communication at one end of reactor10for the fluid to go from one channel32to the adjacent channel32(the fluid travels through multiple fluid flow channels32on its way through the reactor10). The main fluid flow directions are shown inFIGS. 4 and 5by the arrows, showing that the fluid flow enters reactor10from inlet33, flows through the longitudinally extending channels32and turns at the ends of adjacent interior channels32and exits from outlet34.

In the embodiment ofFIG. 4andFIG. 5, the fluid flows in and out of UV-LED reactor10, passes through longitudinally extending channels32, and is irradiated by UV radiation from UV-LEDs35. LED(s)35are positioned at one end of flow channels32. The main direction of the radiant beams and of the flow are back and forth along the longitudinal direction (e.g., in directions aligned with a longitudinal axis) of longitudinally extending fluid flow channels32. Reactor10may be used for attaining UV photoreaction(s) in the fluid flow. Reactor10may also be used for the treatment of a fluid, such as treatment of water. UV-LEDs35may be turned on and off automatically by an external signal, such as a signal from a device that detects the fluid flow rate.

FIG. 6shows a UV-LED reactor20according to an exemplary embodiment of the present invention. In the illustrated embodiment ofFIG. 6, UV-LED reactor20comprises a housing54, flow channel walls55(which define corresponding longitudinally extending fluid flow channels53for conveying fluid such as water in longitudinal dimensions therethrough), an inlet56for the fluid to enter and an outlet57for the fluid to exit, LEDs58, and a UV-transparent window59disposed between LEDs58and the longitudinally extending channels. One or more lenses (not expressly shown inFIG. 6), including collimating, converging, and/or other lenses, or a combination thereof, may be disposed in the reactor20between UV-LEDs58and the fluid flow channels53to focus the UV-LED radiation pattern into each of the longitudinally extending flow channels53. UV-LED reactor20is a multi-channel reactor, where the fluid flow is irradiated by UV-LEDs in some of the longitudinally extending channels53A from one end (the two exterior channels53A on the sides of reactor20of theFIG. 6embodiment) and in some of the channels53B from two ends (the two interior channels53B of reactor20of theFIG. 6embodiment), as the fluid flow moves through the reactor channels53. As with any of the embodiments described above, in general, any of the fluid flow channels53of reactor20could be irradiated from one or both of their longitudinal ends. In some embodiments, this may involve appropriate orientation of inlet56and outlet57relative to the longitudinal direction, so that the LEDs58can be placed at both longitudinal ends of the channel in which the flow enters and exits. The main fluid flow directions of the FIG. reactor20are shown by the arrows.

The concepts described above in connection withFIGS. 2A, 2B, 2C and 3may be applied to each channel of the multi-channel reactors of the embodiments illustrated inFIGS. 4-6. In particular, with suitably configured radiation focusing elements (e.g. with lens(es) that are selected, positioned, shaped, fabricated from materials with suitable index of refraction and/or the like) and/or with suitable selection of flow control element(s), the average (over the longitudinal dimension of each longitudinally extending fluid flow channel) radiation fluence rate profile across the cross-section of the bore of the longitudinally extending flow channel (or a portion thereof) can be positively correlated with, or in some embodiments generally proportional to, the average (over the longitudinal dimension of the longitudinally extending fluid flow channel) longitudinal direction velocity fluid velocity profile within the cross-section of the bore of the longitudinally extending flow channel (or the portion thereof).

Some embodiments of a UV-LED reactor comprise a plurality of UV-LEDs irradiating the fluid flowing through each longitudinally extending fluid flow channel (i.e. a many to one ratio of LEDs to fluid flow channels). In some embodiments, such as those shown inFIGS. 7 and 8(as described below), a plurality of focusing elements is incorporated (one focusing element for each UV-LED), and the radiation from each UV-LED is focused by its corresponding focusing element and directed into its corresponding channel. In other embodiments, such as those shown inFIGS. 11 and 12(as described below), one or more focusing elements (or portions thereof) are shared between multiple UV-LEDS and radiation from the multiple UV-LEDs passes through the one or more shared focusing elements into their corresponding channel. In some embodiments, groups of one or more LEDs may share groups of one or more corresponding focusing elements (or one or more corresponding lenses from within one or more corresponding focusing elements) in any suitable matter. For example, there may be a total of 9 LEDs and 3 lenses, where the LEDs are grouped into three groups of 3 LEDs, and the radiation from each group of 3 LEDs passes through a single lens corresponding to the LED group. A UV-LED reactor incorporating multiple UV-LEDs may be particularly suitable for fluid flow channels which have a bore having relatively large cross-section. The multiple UV-LEDs may help to maximize irradiance coverage by increasing irradiance in such fluid flow channels, as compared to an embodiment operated with a single UV-LED for irradiating the fluid flow channel.

FIGS. 7 and 8show UV-LED reactors300,400in accordance with embodiments comprising multiple UV-LEDs for irradiating each longitudinally extending fluid flow channel (i.e. a many to one ratio of LEDs to fluid flow channels) and multiple focusing elements (i.e. a one to one ratio of LEDS to focusing elements, it being understood that a focusing element may actually comprise multiple lenses). UV-LED reactors300,400are similar in some respects to the reactors30,40ofFIGS. 2A and 2B. However, UV-LED reactors300,400differ from UV-LED reactors30,40in that UV-LED reactors300,400comprise a plurality of LED-focusing element assemblies308,408for emitting UV radiation to irradiate the fluid in the longitudinally extending fluid flow channel301,401of each UV-LED reactor300,400. Each LED-focusing element assembly308,408comprises a UV-LED306,406and a corresponding radiation-focusing element307,407comprising one or more focusing lenses304,404. In the illustrated embodiment, focusing elements308,408are shown to comprise one lens304,404for each UV-LED306,406. The lens304,404may be integrated in, or disposed proximate or adjacent to, its corresponding UV-LED306,406. In some embodiments, focusing elements308,408may comprise one or more lenses304,404, each of which may be integrated in, or disposed proximate or adjacent to, its corresponding UV-LED306,406. A UV-transparent window318,418, such as a quartz window, may be disposed between the LED-focusing element assemblies308,408and the fluid flow channels301,401.

In UV-LED reactors300,400, the fluid (not shown) is moving with a longitudinal direction velocity profile312,412which varies (as shown by dashed lines319,419) across the cross-section of the bore of the fluid flow channel301,401. Radiation315,415emitted from the UV-LEDs306,406passes through focusing elements307,407(each focusing element307,407corresponding to a corresponding one of the UV-LEDs306,406) and is focused to impinge on fluid that is traveling in the longitudinal direction in the bore of the longitudinally extending flow channel301,401. Focusing elements307,407and/or their focusing lenses304,404may be configured (e.g. with lens(es) that are selected, positioned, shaped, fabricated from materials with suitable index of refraction and/or the like) to provide higher relative radiation fluence rate at the center of the cross-section of the bore of the fluid flow channel301,401, where the fluid has a higher relative longitudinal direction velocity. Conversely, focusing elements307,407and/or their focusing lenses304,404may be configured (e.g. with lens(es) that are selected, positioned, shaped, fabricated from materials with suitable index of refraction) to provide lower relative radiation fluence rate at locations spaced apart from the center of the cross-section of the bore of the fluid flow channel301,401. With suitably configured radiation focusing elements307,407(e.g. with lens(es)304,404that are selected, positioned, shaped, fabricated from materials with suitable index of refraction and/or the like), the average (over the longitudinal dimension of the longitudinally extending fluid flow channel301,401) radiation fluence rate profile across the cross-section of the bore of longitudinally extending flow channel301,401(or a portion thereof) can be positively correlated with, or in some embodiments generally proportional to, the average (over the longitudinal dimension of the longitudinally extending fluid flow channel301,401) longitudinal direction velocity fluid velocity profile within the cross-section of the bore of longitudinally extending flow channel301,401(or the portion thereof). Therefore, by the time that the fluid leaves the reactor (or leaves fluid flow channel301,401), each component of the fluid may receive similar or comparable aggregate UV radiation dose.

In practice, for example, this may be achieved by constructing each of focusing elements307,407to comprise one or more focusing lenses304,404which focus the radiation into the bore of fluid flow channel301,401, based on the expected velocity profile of the fluid in channel301,401in a manner which achieves the above-described characteristics. In some embodiments, such focusing lenses may comprise: a converging lens18as shown inFIG. 1Band/or a collimating lens15as shown inFIG. 1Athat is not necessarily positioned at its focal length distance (with respect to the UV radiation source) or any other suitable lens(es) or combinations of lenses to focus the radiation into the bore of the fluid flow channel301,401based on the expected velocity profile to achieve the desired radiation fluence rate profile. In the illustrated embodiment ofFIGS. 7 and 8, the radiation315,415inside the bore of the fluid flow channel301,401is shown as being semi-transparent, so that the longitudinal direction velocity profile312,412of fluid in the bore of the fluid flow channel301,401can be observed.

The velocity profile312in theFIG. 7embodiment differs from the velocity profile412in theFIG. 8embodiment. InFIG. 7, the velocity variation319across the cross-section of the fluid flow channel301is greater when compared to the variation in velocity419of theFIG. 8embodiment (i.e. the variation of the fluid velocity between the maximum velocity at the center of the cross-section of the bore of the fluid flow channel301and locations spaced apart from the center of the cross-section of the bore of fluid flow channel301of theFIG. 7embodiment is greater than the variation of the fluid velocity as between the maximum velocity at the center of the cross-section of the bore of the fluid flow channel401and locations spaced apart from the center of the cross-section of the bore of fluid flow channel401of theFIG. 8embodiment). As such, the focusing elements307and/or focusing lenses304of theFIG. 7embodiment are configured (e.g. with lenses that are selected, positioned, shaped and/or fabricated from materials having suitable indices of refrations) to focus the radiation in a manner which provides considerably higher fluence rate variation across the cross-section of the bore of channel301of theFIG. 7embodiment, relative to the fluence rate variation across the cross-section of the bore of channel401of theFIG. 8embodiment (i.e. the variation of the radiation fluence rate as between the center of the cross-section of the bore of the fluid flow channel301and locations spaced apart from the center of the cross-section of the bore of fluid flow channel301of theFIG. 7embodiment is greater than the variation of the radiation fluence rate as between the center of the cross-section of the bore of the fluid flow channel401and locations spaced apart from the center of the cross-section of the bore of fluid flow channels401of theFIG. 8embodiment). The UV radiation in theFIG. 7embodiment may be significantly more focused in the center of the cross-section of the bore than at locations spaced apart from the center of the cross-section of the bore.

In comparison, in theFIG. 8embodiment the velocity is only moderately higher at the center of the cross-section of the bore of the fluid flow channel401. As such, the focusing elements407and/or lenses404of theFIG. 8embodiment are configured (e.g. with lenses that are selected, positioned, shaped and/or fabricated from materials having suitable indices of refraction) to provide moderately higher fluence rate variation across the cross-section of bore401of theFIG. 8embodiment relative to the fluence rate variation of theFIG. 7embodiment (i.e. the variation of the radiation fluence rate as between the center of the cross-section of the bore of the fluid flow channel401and locations spaced apart from the center of the cross-section of the bore of fluid flow channel401of theFIG. 8embodiment is less than the variation of the radiation fluence rate as between the center of the cross-section of the bore of the fluid flow channel301and locations spaced apart from the center of the cross-section of the bore of fluid flow channel301of theFIG. 7embodiment). The UV radiation may be moderately more focused in the center of the cross-section of the bore401of theFIG. 8embodiment than at locations spaced apart from the center of the cross-section of the bore401.

FIG. 9is a top perspective representation of a UV-LED reactor500comprising multiple LED-lens assemblies508irradiating a longitudinally extending fluid flow channel501having a fluid inlet533, in a manner similar to the UV-LED reactors300,400shown inFIGS. 7 and 8. In theFIG. 9embodiment, each LED-lens assembly508may have similar components to the LED-lens assemblies308,408described above with respect to theFIGS. 7 and 8embodiments, including radiation-focusing elements which focus the radiation into the bore of the fluid flow channel501based on the expected velocity profile so as to provide higher relative radiation fluence rate at the center of the cross-section of the bore of the fluid flow channel501(where the fluid has a higher relative longitudinal direction velocity) and lower relative radiation fluence rate at locations spaced apart from the center of the cross-section of the bore of the fluid flow channel501(where the fluid has a lower relative longitudinal direction velocity). For clarity of illustration, not specifically shown inFIG. 9, are the components of each LED-lens assembly508. Also not shown is a UV-transparent window, which may be located between the LED-lens assemblies508and the fluid flow channel501. With suitably configured radiation focusing elements (e.g. with lens(es) that are selected, positioned, shaped, fabricated from materials with suitable index of refraction and/or the like), the average (over the longitudinal dimension of the longitudinally extending fluid flow channel501) radiation fluence rate profile across the cross-section of the bore of longitudinally extending flow channel501(or a portion thereof) can be positively correlated with, or in some embodiments generally proportional to, the average (over the longitudinal dimension of the longitudinally extending fluid flow channel501) longitudinal direction velocity fluid velocity profile within the cross-section of the bore of longitudinally extending flow channel501(or the portion thereof). In theFIG. 9embodiment, a plurality of fluid outlets534are located at one end of the fluid flow channel501where the irradiated fluid exits. The multiple outlet configuration shown inFIG. 9may facilitate relatively more uniform velocity distribution across the cross-section of fluid flow channel501, particularly for a fluid flow channel which has a bore having a relatively larger cross-section.

FIG. 10is a top perspective representation of a UV-LED reactor600comprising multiple LED-lens assemblies608(each comprising similar components to UV-LED assemblies308,408) irradiating a longitudinally extending fluid flow channel601having a fluid inlet633. Reactor600is similar to the UV-LED reactor500ofFIG. 9. However, UV-LED reactor600differs from UV-LED reactor500in that UV-LED reactor600also comprises a flow distributor674near inlet633. Flow distributor674may comprise one or more flow-restraining elements, such as static mixers, vortex generators, baffles and/or the like. Flow distributor674may additionally or alternatively comprise a perforated (e.g. porous) material where the perforation (e.g. porosity) is distributed evenly or unevenly through the body of distributor674. The porosity of flow distributor674may provide a more uniform distribution of the fluid velocity within the cross section of the fluid flow channel601and to eliminate the effect of jet flow generated by an inlet633with a small cross section, as compared to the cross section of the bore of fluid flow channel601, if a more uniform velocity distribution is desirable. Flow distributor674may be deployed in the fluid flow channel601to restrain the fluid flow in the bore of the longitudinally extending fluid flow channel601and may be configured (e.g. by suitable shape, size, density, porosity and/or the like) to achieve a desired velocity profile and/or for providing an average (over the longitudinal dimension of the longitudinally extending fluid flow channel601) longitudinal direction velocity profile over the cross-section of the bore of the longitudinally extending fluid flow channel601(or a portion thereof) which is correlated with an average (over the longitudinal dimension of the channel601) radiation fluence rate profile over the cross-section of the bore of the longitudinally extending fluid flow channel601(or a portion thereof).

FIGS. 11 and 12show UV-LED reactors700,800in accordance with embodiments comprising multiple UV-LEDs706,806for irradiating each longitudinally extending fluid flow channel (i.e. a many to one ratio of LEDs to fluid flow channels). In the embodiments ofFIGS. 11 and 12, a plurality of LEDs706,806share radiation-focusing elements707,807(i.e. a many to one LED to radiation focusing element ratio) or portions thereof. In the illustrated embodiments ofFIGS. 11 and 12, each focusing element707,807is shown as comprising a single lens704,804. This is not necessary. In some embodiments, each focusing element707,807may comprise a plurality of lenses704,804. In some such embodiments, a plurality of LEDs706,806may share portions of radiation focusing elements707,807(e.g. one or more lenses704,804from within a radiation focusing element707,807). UV-LED reactors700,800are similar in some respects to the UV-LED reactors300,400ofFIGS. 7 and 8. For example, similarly to UV-LED reactors300,400, UV-LED reactors700,800comprise multiple UV-LEDs706,806. However, UV-LED reactors700,800differ from UV-LED reactors300,400in that UV-LED reactors700,800comprise multiple LEDs706,806which share radiation focusing elements707,807(i.e. a many to one LED to radiation focusing element ratio) or portions thereof. Radiation-focusing elements707,807focus UV radiation emitted by UV-LEDs706,806to irradiate the fluid in the longitudinally extending fluid flow channel701,801of each UV-LED reactor700,800. In the illustratedFIGS. 7 and 8embodiments, radiation from multiple UV-LEDs706,806passes through shared focusing elements707,807(or portions thereof). A UV-transparent window718,818, such as a quartz window, may be disposed between the focusing elements707,807and the fluid flow channels701,801.

In UV-LED reactors700,800, the fluid (not shown) is moving with a longitudinal direction velocity profile712,812which has a corresponding variation719,819across the cross-section of the bore of the fluid flow channel701,801. Radiation715,815emitted from the UV-LEDs706,806passes through focusing elements707,807to impinge on fluid that is traveling in the longitudinal direction in the bore of the longitudinally extending flow channel701,801. Lenses704,804of focusing elements707,807may be selected, positioned, shaped, fabricated from materials with suitable index of refraction and/or the like to provide higher relative radiation fluence rate at the center of the cross-section of the bore of the fluid flow channel701,801, where the fluid has a higher relative longitudinal direction velocity. Conversely, focusing elements707,807and/or focusing lenses704,804may be configured (e.g. selected, positioned, shaped, fabricated from materials with suitable index of refraction) to provide lower relative radiation fluence rate at locations spaced apart from the center of the cross-section of the bore of the fluid flow channel701,801. With suitably configured radiation focusing elements707,807(e.g. with lens(es)704,804that are selected, positioned, shaped, fabricated from materials with suitable index of refraction and/or the like), the average (over the longitudinal dimension of the longitudinally extending fluid flow channel701,801) radiation fluence rate profile across the cross-section of the bore of longitudinally extending flow channel701,801(or a portion thereof) can be positively correlated with, or in some embodiments generally proportional to, the average (over the longitudinal dimension of the longitudinally extending fluid flow channel701,801) longitudinal direction velocity fluid velocity profile within the cross-section of the bore of longitudinally extending flow channel701,801(or the portion thereof). Therefore, by the time that the fluid leaves the reactor (or leaves fluid flow channel701,801), each component of the fluid may receive similar or comparable UV radiation dose.

In practice, this may be achieved by constructing focusing elements707,807to comprise one or more lenses704,804which focus the radiation into the bore of fluid flow channel701,801in a manner which achieves the above-described characteristics. In some embodiments, such focusing lenses may comprise: a converging lens18as shown inFIG. 1Band/or a collimating lens15as shown inFIG. 1Athat is not necessarily positioned at its focal length distance (with respect to the UV radiation source) or any other suitable lens(es) or combinations of lenses to focus the radiation into the bore of the fluid flow channel701,801based on the expected velocity profile to achieve the desired radiation fluence rate profile. In the illustrated embodiment ofFIGS. 11 and 12, the radiation715,815inside the bore of the fluid flow channel701,801is shown as being semi-transparent, so that the longitudinal direction velocity profile712,812of fluid in the bore of the fluid flow channel701,802can be observed.

The velocity profile712in theFIG. 11embodiment differs from the velocity profile812in theFIG. 12embodiment. InFIG. 11, the velocity variation719across the cross-section of the fluid flow channel701is greater when compared to the variation in velocity819of theFIG. 12embodiment (i.e. the variation of the fluid velocity between the maximum velocity at the center of the cross-section of the bore of the fluid flow channel701and locations spaced apart from the center of the cross-section of the bore of fluid flow channel701of theFIG. 11embodiment is greater than the variation of the fluid velocity as between the maximum velocity at the center of the cross-section of the bore of the fluid flow channel801and locations spaced apart from the center of the cross-section of the bore of fluid flow channel801of theFIG. 12embodiment). As such, the focusing elements707and/or focusing lens(es)704of theFIG. 11embodiment are configured (e.g. with lenses704that are selected, positioned, shaped and/or fabricated from materials having suitable indices of refraction) to focus the radiation in a manner which provides considerably higher fluence rate variation across the cross-section of the bore of channel701of theFIG. 11embodiment, relative to the fluence rate variation across the cross-section of the bore of channel801of theFIG. 12embodiment (i.e. the variation of the radiation fluence rate as between the center of the cross-section of the bore of the fluid flow channel701and locations spaced apart from the center of the cross-section of the bore of fluid flow channel701of theFIG. 11embodiment is greater than the variation of the radiation fluence rate as between the center of the cross-section of the bore of the fluid flow channel801and location spaced apart from the center of the cross-section of the bore of fluid flow channel801of theFIG. 12embodiment). The UV radiation in theFIG. 11embodiment may be significantly more focused in the center of the cross-section of the bore than at locations spaced apart from the center of the cross-section of the bore.

In comparison, in theFIG. 12embodiment the velocity is only moderately higher at the center of the cross-section of the bore of the fluid flow channel801. As such, the focusing elements807and/or lenses804of theFIG. 8embodiment are configured (e.g. with lenses that are selected, positioned, shaped and/or fabricated from materials having suitable indices of refraction) to provide moderately higher fluence rate variation across the cross-section of bore801of theFIG. 12embodiment relative to the fluence rate variation of theFIG. 11embodiment (i.e. the variation of the radiation fluence rate as between the center of the cross-section of the bore of the fluid flow channel801and locations spaced apart from the center of the cross-section of the bore of fluid flow channel801of theFIG. 12embodiment is less than the variation of the radiation fluence rate as between the center of the cross-section of the bore of the fluid flow channel701and locations spaced apart from the center of the cross-section of the bore of fluid flow channel701of theFIG. 11embodiment). The UV radiation may be moderately more focused in the center of the cross-section of the bore801of theFIG. 12embodiment than at locations spaced apart from the center of the cross-section of the bore801.

The reactors and methods of using the reactors described herein may provide efficient and compact UV-LED reactors that may be applied to any UV-activated photoreaction or photocatalytic reaction. One of these applications is UV-based water treatment, particularly water purification or disinfection by UV-inactivation of microorganisms and UV-based degradation of chemical contaminants. For example, some embodiments may be particularly suitable for processing low to moderate flow rates of water, such as in point-of-use or point-of-entry water purification applications, as described elsewhere herein, including the description below. Further, the reactors and methods of using reactors described herein can be optimized based on a combination of UV-LED radiation patterns and the flow field hydrodynamics to provide superior (or at least relatively more consistent) UV dose delivery to the fluid as compared to existing UV-LED reactors.

Some aspects of the invention provide a reactor designed to control the average (over a longitudinal dimension of a longitudinally extending channel) radiation fluence rate distribution and/or the average (over a longitudinal dimension of a longitudinally extending channel) longitudinal direction velocity distribution over a cross-section (or a portion of the cross-section) of the bore of a longitudinally extending fluid flow channel, so that the reactor imparts similar or comparable UV dose (a product of radiation fluence rate and residence time) to all (or substantially all) of the fluid elements travelling through the bore of the fluid flow channel. As discussed, one or both of these parameters (the average radiation fluence rate distribution across the cross-section (or portion thereof) and/or the average longitudinal direction fluid velocity across the cross-section (or portion thereof)) may be controlled to achieve an average radiation fluence rate that is positively correlated with, and in some embodiments generally proportional to, an average velocity profile over a cross-section of the bore of the channel (or a portion thereof). For brevity, these characteristics (as described in more particular detail elsewhere herein) may be referred to as velocity-fluence rate matching. In some embodiments. such velocity-fluence rate matching may achieve similar or comparable UV dose to all of the fluid elements as the fluid traverses the longitudinal dimension of the longitudinally extending fluid flow channel. It will be appreciated that the cross-sectional longitudinal direction velocity profile of a fluid travelling in the bore of a longitudinally extending fluid flow conduit depends on the Reynolds number of the fluid, which is a material characteristic of the fluid properties along with the characteristics of the bore of the fluid flow channel and the fluid velocity. It will be further appreciated that the longitudinal direction fluid flow velocity of any fluid element need not be constant, but can change as the fluid moves along the longitudinal dimension of the flow channel (e.g. the fluid element may move from a higher velocity central location within the cross-section to a lower velocity location away from the center of the cross-section or vice versa during its movement through the flow channel).

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 embodiments, methods, and examples herein. The invention should therefore not be limited by the above described embodiments, methods, and examples.

Further example embodiments of UV-LED based photoreactors which could incorporate the above-described radiation dose-control methods and apparatus (with reference toFIGS. 1 to 12) are described below.

For example, various channel configurations of UV-LED reactors according to example embodiments are described below with reference toFIGS. 13 to 18. In these embodiments, the UV-LED reactors may incorporate radiation dose-control methods and apparatus (such as radiation-focusing elements and/or flow-restraining elements, as described elsewhere herein) even if such radiation-focusing elements and/or flow-restraining elements are not specifically shown or described in the figures.

FIGS. 13A to 13Eshow side views of single channel UV-LED reactor configurations according to exemplary embodiments. 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 as 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.

FIG. 13Ais a side view of a UV-LED reactor70A comprising a housing61, a UV-LED62, and a UV-transparent window63. This single-channel reactor is irradiated from only one end of the flow channel, providing flexibility in the outlet direction. A chemical reagent (not shown) may be added to the reactor along with the fluid flow to cause desirable photoreactions. Velocity-fluence rate matching may be achieved in theFIG. 13Aembodiment using any of the techniques described herein.

FIG. 13Bis a side view of a UV-LED reactor70B comprising a housing64, two or more UV-LEDs65, and UV-transparent windows66. UV-LED reactor70B is irradiated from both ends of the flow channel (by at least one UV-LED65positioned at each end), offering a higher radiation fluence compared to theFIG. 7Aconfiguration which is irradiated from only one end. Each UV-LED65may emit UV radiation of a specific wavelength (which may be the same or different). Where the wavelengths of each UV-LED65are different, theFIG. 13Bembodiment may provide a combination of different wavelengths irradiating the fluid flow and one (or both) of these wavelengths may exhibit velocity-fluence rate matching. Where the wavelengths of each UV-LED65are the same, the radiation from the combination of UV-LEDs65in theFIG. 13Bembodiment may exhibit velocity-fluence rate matching.

FIG. 13Cis a side view of a UV-LED reactor70C comprising a housing71, a UV-LED72, a UV-transparent window73, and a static mixer74or other such element to restrain the fluid flow. The curved black arrows indicate mixing of the fluid after passing through the static mixer74. The static mixer74is applied to facilitate mixing and the generation of potential vortices for the improvement of the UV-LED reactor hydrodynamics and may thus be referred to as a vortex generator. Mixing may result in a relatively more uniform distribution of the longitudinal direction fluid velocity, even although velocity components in other directions may be relatively less uniform. Providing relatively more uniform distribution of the longitudinal direction fluid velocity may make it easier to implement a corresponding fluence rate distribution and ultimately easier to achieve velocity-fluence rate matching.

FIG. 13Dis a side view of a UV-LED reactor70D comprising a housing81, one or more UV-LEDs82, UV-transparent windows83, and a photocatalyst immobilized on support structures84. The photocatalyst is activated by UV radiation from the UV-LEDs to initiate photocatalytic reactions in the UV-LED reactor. Velocity-fluence rate matching may be achieved in theFIG. 13Dembodiment using any of the techniques described herein.

FIG. 13Eis a side view of a UV-LED reactor70E comprising a housing85, UV-LEDs86, UV-transparent windows87, and photocatalyst immobilized on perforated support structures88. 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 may provide high radiation flux to the photocatalyst. Velocity-fluence rate matching may be achieved in theFIG. 13Eembodiment using any of the techniques described herein.

FIGS. 14A and 14Bare side views (with the dotted lines showing the direction of the third dimension) of two UV-LED reactors80and90according to exemplary embodiments comprising a stack of longitudinally extending fluid flow channels.FIG. 14Ashows a side view of a UV-LED reactor80comprising a housing91, a stack of longitudinally extending fluid flow channels92, each having a rectangular cross section, and a plurality of UV LEDs93.FIG. 14Bshows the side view of a UV-LED reactor90comprising a housing95, a stack of longitudinally extending fluid flow channels96, each having a triangular cross-section, and a plurality of UV-LEDs97. In either of these embodiments, the fluid is irradiated by the UV LEDs as it moves through the stack of longitudinally extending fluid flow channels. Velocity-fluence rate matching may be achieved in each of the flow channels of theFIGS. 14A and 14Bembodiments using any of the techniques described herein. Such configuration facilitates the manufacture of UV-LED reactors which may deliver high UV fluence (dose) and/or high throughput. The cross-section of the fluid flow channels may be rectangular (FIG. 14A), triangular (FIG. 14B), or another shape. The main fluid flow directions are shown by the arrows. Other components of UV-LED reactors80,90including UV-transparent windows, etc. are not shown so as not to obscure the remaining components in the illustration.

FIGS. 15A to 15Cshow a top view (FIG. 15A), a side view (FIG. 15B), and a perspective view (FIG. 15C) of a UV-LED reactor1110according to an exemplary embodiment. The UV-LED reactor1110comprises: a housing1119, a pair of adjacent longitudinally extending fluid flow channels1113with channel walls1114for conveying fluid (e.g. water) in longitudinal directions therethrough, an inlet1111for the fluid to enter and an outlet1112for the fluid to exit. UV-LED reactor1110also comprises: two (or more) UV-LEDs1106mounted on a circuit board1116, a UV-transparent window1118such as a quartz window disposed between the circuit board1116and the fluid flow channels1113, an on/off switch1121, and a power port1122. The drive circuits for the UV-LED, microcontrollers, and other electronic mechanisms (not shown) may be placed in an electronic housing1123between the LED circuit board1116and the on/off switch1121. Different lenses (not shown), including collimating, converging, diverging and/or other lenses (not shown) may be disposed in the reactor1110between UV-LEDs1106and the longitudinally extending fluid flow channels1113to focus the UV-LED radiation pattern into the fluid flow channels1113. The fluid flow channels1113are in fluid communication at one end for the fluid to go from one channel1113to the adjacent channel1113. As indicated by the arrows, which show the main fluid flow directions, the fluid enters reactor1110from inlet1111, flows through a first longitudinally extending fluid flow channel1113and after turning at the end of the adjacent interior channels1113continues through the second longitudinally extending fluid flow channel1113before exiting from outlet1112. The fluid flows in and out of the UV-LED reactor1110, passes through the channels1113, and is irradiated by UV radiation from UV-LEDs1106. Velocity-fluence rate matching may be achieved in each of the flow channels of theFIG. 15A-150embodiment using any of the techniques described herein.

FIGS. 16A to 16Dshow a top view (FIG. 16AandFIG. 16D), a side view (FIG. 16B), and a perspective view (FIG. 16C) of a UV-LED reactor1120according to an exemplary embodiment. UV-LED reactor1120comprises a housing1139, a pair of adjacent longitudinally extending fluid flow channels1133with channel walls1134for conveying fluid (e.g. water) in longitudinal directions therethrough, an inlet1131for the fluid to enter, an outlet1132for the fluid to exit, and UV-LEDs1135mounted on a circuit board1136. Collimating lenses are1137may be disposed on a frame1144in the reactor1120between UV-LEDs1135and fluid flow channels1133to focus the UV-LED radiation pattern into the longitudinally extending fluid flow channels1133. Reactor1120also comprises a UV-transparent window1138, such as a quartz window, disposed between the frame1144holding the collimating lenses1137and the fluid flow channels1133. Reactor1120comprise an on/off switch1141and a power port1142. The drive circuits for UV-LEDs, microcontrollers, and other electronic mechanisms (not shown), may be placed in the electronic housing1143, between the LED circuit board1136and the on/off switch1141. The collimating lenses1137collimate UV radiation from the UV-LEDs1135into the fluid flow channels. In some embodiments, the UV-LED1135may have a converging lens integrated in the LED. The presence of both a converging lens and a collimating lens disposed in front of a UV-LED1135may provide a more effective way of irradiating the fluid flow. Referring toFIG. 16D, there are shown UV rays1145emitted from the UV-LEDs1135and passing through the collimating lenses1137to become collimated rays1146. The fluid flows in and out of the UV-LED reactor1120, passes through the channels1133, and is irradiated by UV collimated rays1146in the reactor channels1133. This reactor configuration may have a circular cross section of the flow channels. The main directions of UV rays are shown by the dashed arrows. Velocity-fluence rate matching may be achieved in each of the flow channels of theFIG. 16A-16Dembodiment using any of the techniques described herein.

FIGS. 17A and 17Bshow partially-diagrammatic perspective views of two configurations for UV-LED reactors, irradiated by UV-LEDs, and disposed through the length of the longitudinally extending fluid flow channels. For clearer illustration of the concepts explained herein, only the UV-LEDs, UV-LED boards, and photocatalyst structures of the UV-LED reactors are shown in these figures.FIG. 17Aillustrates a UV-LED reactor1130comprising a series of perforated boards1153on which are mounted UV-LEDs1152, wherein the fluid flow (not shown) in the longitudinally extending fluid flow channel1151is irradiated by the UV-LEDs1152.FIG. 17Billustrates a UV-LED reactor1140, comprising a series of perforated boards1156on which are mounted UV-LEDs1155, and a series of photocatalyst structures1157, wherein the fluid flow (not shown) and the photocatalyst structures in the longitudinally extending fluid flow1154are irradiated by the UV-LEDs1155. The arrows show the overall direction of the fluid flow as it moves past the UV-LEDs and photocatalyst structures. The fluid flow passes through the LED perforated boards and the photocatalyst structures. This configuration may cause photoreactions and photocatalytic reactions in the fluid. Velocity-fluence rate matching may be achieved in the embodiments ofFIGS. 17A and 17Busing any of the techniques described herein.

FIGS. 18A and 18Bshow partially-diagrammatic perspective views of two configurations for UV-LED reactors, irradiated by UV-LEDs, and disposed throughout the length of the fluid flow channels. For clearer illustration of the concepts explained herein, only the UV-LEDs, UV-LED boards, and photocatalysts parts of the UV-LED reactors are shown in these figures.FIG. 18Aillustrates a UV-LED reactor1160, comprising a series of solid boards1163on which are mounted UV-LEDs1162, wherein the fluid flow (not shown) in the longitudinally extending fluid flow channel1161irradiated by the UV-LEDs1162.FIG. 18Billustrates a UV-LED reactor1170, comprising a series of solid boards1166on which are mounted UV-LEDs1165, and a series of photocatalyst structures1167, wherein the fluid flow (not shown) and the photocatalyst structures in the longitudinally extending fluid flow channel1164are irradiated by the UV-LEDs1165. The arrows show the overall direction of the fluid flow moving past the UV-LEDs1162,1165and photocatalyst structures1167. As indicated by the curved arrows, the fluid flow passes 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. Velocity-fluence rate matching may be achieved in the embodiments ofFIGS. 18A and 18Busing any of the techniques described herein.

In the UV-LED reactor configurations presented inFIG. 17andFIG. 18, the fluid flow and the photocatalyst structures may be irradiated by UV-LEDs from one or both sides. As such, UV-LEDs may be mounted on either or both sides of the LED board. Further, in either of the configurations presented inFIGS. 17 and 18, static mixers (not shown) may be disposed in the reactor to alter the fluid flow hydrodynamics.

The longitudinally extending fluid flow channels described herein have a cross section which may take any suitable shape, including, without limitation, a circle, a semi-circle, a square, a rectangle, a triangle, a trapezoid, a hexagon, and the like. These cross sections may enhance the reactor performance by improving the reactor hydrodynamics and/or radiation distribution given certain fluid flow conditions and UV-LED radiation patterns. For example, a fluid flow channel having a circular cross section may provide optimal radiation transfer to the fluid for UV-LED collimated radiation.

Embodiments of the technology described herein are directed to providing an efficient and compact UV-LED reactor which is applicable to a range of UV-activated photoreaction or photocatalytic reaction in a fluid. For example, as described herein, one of these applications is water purification by UV-inactivation of microorganisms and UV-based degradation of chemical contaminants.

Particular applications of the UV-LED reactor include processing and treating water of low to moderate flow rates, for example, in point-of-use applications. Further, due to its compact configuration and high efficiency, the UV-LED reactor in accordance with the embodiments described herein may be incorporated in appliances (e.g. refrigerators, freezers, water coolers, coffee machines, water dispensers, icemakers, etc.), health care or medical devices or facilities, dental equipment, and any other devices which require the use of clean water. The UV-LED reactor may be either incorporated into the device or be applied as an add-on into the existing device. For example, the UV-LED reactor may be positioned somewhere through the waterline so that the UV-LED reactor treats the water that is used in (e.g. passing through the waterline of) the device. This may be of particular interest where it is desirable that the fluid be irradiated/treated while passing through a pipe, or where there is a desire to prevent the formation of potential microorganism biofilm inside a pipe, or where it is desirable that the flow be treated at the end of a pipeline before being used. The UV-LED reactor may be integrated in the device along with one or more other forms of water purification methods (such as filtration). Exemplary point-of-use fluid treatment applications of the UV-LED reactor are next described with references toFIGS. 19 to 21.

FIG. 19shows a water treatment system200, comprising an inlet pipe201, an outlet pipe202, and a water tap205, and incorporating a UV-LED reactor203operated with UV-LEDs204for the treatment of water. The water enters the reactor203via inlet201, passes through the UV-LED reactor203, and is irradiated by UV radiation emitted from the UV-LEDs204, prior to exiting from outlet pipe202and going to the tap205for general use. The general fluid flow directions are shown by the arrows.

In some embodiments, the UV-LED reactor may be incorporated in appliances that dispense or use water (or water-based fluids) for human consumption. such as freezers, water coolers, coffee makers, vending machines, and the like. The water used for human consumption needs a high degree of purification. The main water supply for refrigerators, freezers, and water coolers, for example, may contain harmful pathogens. This is of particular concern in developing countries and remote areas where water may not be treated properly before distribution in the water network. In addition, due to its particular structure, a refrigerator/freezer waterline may be prone to biofilm and microbial contamination. Polymeric tubing typically transfers water from the main water supply to refrigerators to be used in through-the-door ice and drinking water. Bacterial biofilm can form in the waterline, in particular when the water is not in use (e.g., biofilm can form within 8 hours). Intermittent patterns of water use lead to stagnation of the entire water column within the waterlines for extended periods during the day. The susceptibility of water supply tubes to colonization of bacteria on surfaces and formation of biofilm is a well-recognized problem.

The UV-LEDs of the reactor may be turned on and off automatically in response to the water starting and stopping flowing. Sensors may be used to detect the flow of fluid and send a signal to the reactor to turn the UV-LEDs on or off. The UV-LED reactor may reduce the microbial contamination in the water leaving the waterline (for consumption) and reduce the risk for infection. This is facilitated by the operating conditions of UV-LEDs. For example, a UV-LED can operate at a range of temperatures and can be turned on and off with high frequency, which is particularly important for refrigerator and water cooler applications.

Any appliances which dispense or use water or water-based fluids (e.g. coffee or other beverages) intended for human consumption may incorporate a UV-LED reactor according to the embodiments described herein to treat the water. For example,FIG. 20shows a refrigerator210comprising a body211and a pipe213for delivering water to a water/ice dispenser214. Refrigerator210incorporates a UV-LED reactor212. The water flowing in the pipe213passes through the UV-LED reactor212where it is irradiated by UV radiation prior to entering the water/ice dispenser214. The general fluid flow directions are shown by the arrows. Similarly, other appliances which may benefit from incorporating a UV-LED reactor include, without limitation, freezers, ice machines, frozen beverage machines, water coolers, coffee makers, vending machines and the like.

Other applications of the UV-LED reactor according to the embodiments described herein include the treatment of water or other fluids used in or by healthcare or dental-related or medical devices or facilities, either for operation, cleaning or another purpose which requires clean water. In particular, many healthcare applications require water quality to be of a higher standard than drinking water. The efficiency and compactness of the UV-LED reactors described herein may make them more attractive than conventional UV-lamp reactors for implementation in healthcare devices.

For example,FIG. 21shows a hemodialysis machine comprising a body221and a pipe223containing a UV-LED reactor222. The water flowing in the pipe223passes through the UV-LED reactor222for treatment prior to use in the hemodialysis machine. Similarly, other appliances which may benefit from incorporating the UV-LED reactor include, without limitation, colon hydrotherapy equipment, and dental equipment which dispenses water for cleaning or operation, or the like

With respect to applications in dental equipment, surveys of dental unit waterlines (DUWLs) indicate that biofilm formation is a problem and a great majority of bacteria that have been identified in DUWL are ubiquitous. Although such bacteria may be present in only low numbers in domestic water distribution systems, they can flourish as biofilms on the lumen surfaces of narrow-bore waterlines in dental units. Microorganisms from contaminated DUWL are transmitted with aerosol and splatter, generated by working unit hand-pieces. Various studies emphasize the need for reducing the microbial contamination in DUWL.

In some embodiments, a UV-LED reactor may be incorporated in a dental unit to treat the water used in the unit. The UV-LED reactor may be integrated in the dental units (such as a dental chairs) or the UV-LED reactor may be placed within the tray of the dental chair (assistant tray) holding the water spry, or within the water spray handle, or somewhere else through the waterline, for the treatment of the water prior to use. Features including instant on and off may be included in the UV-LED reactor integrated in a dental unit.

Velocity-fluence rate matching may be achieved in the reactors of any of the embodiments ofFIGS. 19-21using any of the techniques described herein.

The body or housing for embodiments of the UV-LED reactor described herein may be made of aluminum, stainless steel, or of any other sufficiently rigid and strong material such as metal, alloy, high-strength plastic, and the like. In some embodiments, for example, a single channel reactor similar to a pipe, it may also be made of flexible material such as UV-resistance PVC and the like. Also, the various components of the UV-LED reactor may be made of different materials. Further, photocatalyst structures may be used in the reactors, for UV-activated photocatalytic reactions. The photocatalyst may be incorporated in the reactor either by being immobilized on porous substrate, where fluid passes through, and/or by being immobilized on a solid substrate, where fluid passes over. Static mixers or other forms of flow modifiers may be applied to alter the reactor hydrodynamics. Further, a combination of different design concepts may be used. For example, static mixers may be used with photocatalysts.

While the embodiments described herein are presented with particular features and fluid flow channel configurations or lens configurations and the like, it is to be understood that any other suitable combination of the features or configurations described herein may be present in a UV-LED reactor.

Further, the UV-LED reactor may incorporate UV-LEDs of different peak wavelengths to cause synergistic effects to enhance the photoreaction efficiency.

The flow channels and UV-LED arrays of various embodiments can be arranged in a way that the flow is exposed to the desired number of LEDs. The design may be a single flow channel, a series of parallel flow channels, or a stack of multiple 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. This design enables the manufacture of thin planar UV-LED reactors. For example, in some embodiments the UV-LED reactor may be approximately the size of a smart phone, in terms of geometry and dimensions, with inlet and outlet ports for a fluid.

The internal wall of the channels may be made of or be coated with material with high UV reflectivity for facilitating radiation transfer to the fluid and for helping to achieve the velocity-fluence rate matching described herein. Suitable reflective materials may include, by way of example, aluminum, Polytetrafluoroethylene (PTFE), quartz and/or the like. Two adjacent fluid flow channels may be connected at one end, for the fluid to go from one channel to another channel (fluid experiences multi-pass through the reactor). Different lenses including collimating, diverging, converging, and other lenses may be installed in the UV-LED reactor to adjust the UV-LED radiation pattern. The lenses may be configured to provide velocity—fluence rate matching, as described elsewhere herein.

In some embodiments portions of the reactor, where there is little or no radiation fluence rate may be blocked (e.g. filled) so that the fluid does not flow in these regions. This (effectively shaping the fluid flow channels) may help to prevent part of the fluid to receive low dose as a result of spending portions of its residence time in such regions. For example, this may be done in the embodiment ofFIG. 2Cfor the regions where there is no (or little) fluence rate.

Many of the embodiments described herein refer to a cross-section of the bore of a fluid flow conduit or a portion thereof. In some embodiments, unless the context dictates otherwise, references to a cross-section of the bore of a fluid flow channel or to a portion of such a cross-section should be understood to mean a portion of the cross-section that incorporates more than 50% of the surface area of the total cross-section of the bore of the fluid flow channel. In some embodiments, unless the context dictates otherwise, references to a cross-section of the bore of a fluid flow channel or to a portion of such a cross-section should be understood to mean a portion of the cross-section that incorporates more than 75% of the surface area of the total cross-section of the bore of the fluid flow channel. In some embodiments, unless the context dictates otherwise, references to a cross-section of the bore of a fluid flow channel or to a portion of such a cross-section should be understood to mean a portion of the cross-section that incorporates more than 85% of the surface area of the total cross-section of the bore of the fluid flow channel. In some embodiments, unless the context dictates otherwise, references to a cross-section of the bore of a fluid flow channel or to a portion of such a cross-section should be understood to mean a portion of the cross-section that incorporates more than 95% of the surface area of the total cross-section of the bore of the fluid flow channel.

Many of the embodiments described herein comprise focusing elements which are configured (e.g. by suitable lens selection, lens shape, lens position and/or index of refraction of particular lens(es) to focus radiation from one or more UV-LEDs such that the radiation fluence rate profile across a cross-section of a bore of a longitudinally extending flow channel is generally proportional to the cross-sectional velocity profile of the longitudinally flowing fluid across the cross-section of the bore of the flow channel (or the portion thereof), when averaged over the length of the longitudinally extending flow channel. In some such embodiments, the phrase “generally proportional to” may mean that the radiation fluence rate profile across the cross-section of the bore of the flow channel is proportional to the cross-sectional velocity profile of the longitudinally flowing fluid across the cross-section of the bore of the flow channel (or the portion thereof) with a constant of proportionality that varies by less than 50% over the cross-section (or the portion thereof), when averaged over the length of the longitudinally extending flow channel. In some embodiments, this constant of proportionality varies by less than 25% over the cross-section (or the portion thereof), when averaged over the length of the longitudinally extending flow channel. In some embodiments, this constant of proportionality varies by less than 15% over the cross-section (or the portion thereof), when averaged over the length of the longitudinally extending flow channel. In some embodiments, this constant of proportionality varies by less than 10% over the cross-section (or the portion thereof), when averaged over the length of the longitudinally extending flow channel.

While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the scope of the following appended claims and claims hereafter introduced should not be limited by the embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.