Patent Publication Number: US-2021187149-A1

Title: Distributing light in a reaction chamber

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of, and priority to, Canadian patent application no. 2,980,178 filed Sep. 25, 2017, the entire contents of which are incorporated by reference herein. 
     FIELD 
     This disclosure relates generally to distributing light in a reaction chamber. 
     RELATED ART 
     Fluids, such as water or air for example, may be treated, for example to deactivate pathogens, by subjecting the fluid to ultraviolet (“UV”) light in a reaction chamber. Solid-state light sources such as light-emitting diodes (“LEDs”) may produce such UV light, but such light may not be adequately distributed throughout a reaction chamber. 
     As a result, a reaction chamber may have one or more dark regions exposed to little or no such light. For example, a fully collimated or converging-collimated radiation pattern may conserve power, but may leave dark regions that may lead to decrease in reactor performance, particularly when the reaction chamber consists of one channel only. 
     Similarly, when local fluid velocity is higher in some locations of a reaction chamber, for example due to introduction of fluid to the reaction chamber from a side of the reaction chamber, fluid at such a higher fluid velocity requires higher UV intensity to reach to similar level of disinfection when compared to fluid having a lower velocity. 
     Pathogens in fluid passing through such dark regions, or flowing with such high-velocity fluid, may not be deactivated, which may be hazardous to health. 
     SUMMARY 
     According to one embodiment, there is provided a method of distributing electromagnetic radiation in a reaction chamber extending in a longitudinal direction at least between an inlet of the reaction chamber and an outlet of the reaction chamber, the method comprising causing at least some electromagnetic radiation from at least one electromagnetic radiation emitter to be refracted by at least one lens into the reaction chamber as refracted electromagnetic radiation skewed laterally relative to the longitudinal direction. 
     According to another embodiment, there is provided a method of distributing electromagnetic radiation in a reaction chamber, the method comprising causing at least some electromagnetic radiation from at least one electromagnetic radiation emitter to be refracted by at least one lens into the reaction chamber as refracted electromagnetic radiation skewed laterally relative to the at least some electromagnetic radiation from the at least one electromagnetic radiation emitter. 
     In some embodiments, the reaction chamber extends in a longitudinal direction at least between an inlet of the reaction chamber and an outlet of the reaction chamber. 
     In some embodiments, causing the at least some of the refracted electromagnetic radiation to be refracted into the reaction chamber comprises causing the refracted electromagnetic radiation in the reaction chamber to be skewed laterally relative to the longitudinal direction. 
     In some embodiments, the longitudinal direction is parallel to a central longitudinal axis of the reaction chamber. 
     In some embodiments, the inlet is configured to direct fluid into the reaction chamber in an inlet direction non-parallel to the longitudinal direction. 
     In some embodiments, the inlet direction is substantially perpendicular to the longitudinal direction. 
     In some embodiments, causing the at least some of the refracted electromagnetic radiation to be refracted into the reaction chamber comprises causing fluence rate of the refracted electromagnetic radiation in the reaction chamber and along the inlet direction from the inlet to be higher with increased distance from the inlet. 
     In some embodiments, causing the at least some of the refracted electromagnetic radiation to be refracted into the reaction chamber comprises causing a fluence rate of the refracted electromagnetic radiation in a first transverse side of the reaction chamber proximate the inlet to be less than a fluence rate of the refracted electromagnetic radiation in a second transverse side of the reaction chamber opposite the first transverse side of the reaction chamber and opposite the inlet. 
     In some embodiments, the inlet is configured to direct fluid into the reaction chamber in an inlet direction substantially parallel to the longitudinal direction. 
     In some embodiments, causing the refracted electromagnetic radiation in the reaction chamber to be skewed laterally relative to the longitudinal direction comprises causing the refracted electromagnetic radiation in the reaction chamber to be skewed laterally relative to the longitudinal direction and towards an extension in the reaction chamber of the inlet direction from the inlet. 
     In some embodiments, causing the at least some electromagnetic radiation from the at least one electromagnetic radiation emitter to be refracted by the at least one lens into the reaction chamber comprises causing the at least some electromagnetic radiation from the at least one electromagnetic radiation emitter to be: refracted into the reaction chamber by a plurality of lenses spaced apart around an inlet axis extending along the inlet direction; and skewed laterally relative to the longitudinal direction and towards the extension in the reaction chamber of the inlet direction from the inlet. 
     In some embodiments, the plurality of lenses surround the inlet axis. 
     In some embodiments, the electromagnetic radiation comprises ultraviolet (“UV”) radiation. 
     In some embodiments, the at least one electromagnetic radiation emitter comprises at least one UV light-emitting diode (“UV-LED”). 
     In some embodiments, the at least one electromagnetic radiation emitter comprises at least one light-emitting diode (“LED”). 
     In some embodiments, the at least some electromagnetic radiation from the at least one electromagnetic radiation emitter has a principal radiation direction. 
     In some embodiments, the at least some electromagnetic radiation from the at least one electromagnetic radiation emitter is substantially axially symmetric about the principal radiation direction. 
     In some embodiments, the refracted electromagnetic radiation is distributed axially asymmetrically relative to the principal radiation direction of the at least some electromagnetic radiation from the at least one electromagnetic radiation emitter. In some embodiments, a fluence rate of the refracted electromagnetic radiation on a first transverse side of the principal radiation direction is greater than a fluence rate of the refracted electromagnetic radiation on a second transverse side of the principal radiation direction opposite the first transverse side of the principal radiation direction. 
     In some embodiments, the at least one lens comprises at least one lens having an optical axis non-parallel to the principal radiation direction. 
     In some embodiments, the at least one lens comprises at least one lens having an optical axis parallel to and spaced apart from the principal radiation direction. 
     In some embodiments, the at least one lens comprises at least one axially asymmetric lens. 
     According to another embodiment, there is provided a reactor apparatus comprising: a body defining an inlet, an outlet, and a reaction chamber extending in a longitudinal direction at least between the inlet and the outlet; at least one electromagnetic radiation emitter; and at least one lens configured to refract at least some electromagnetic radiation from the at least one electromagnetic radiation emitter into the reaction chamber as refracted electromagnetic radiation skewed laterally relative to the longitudinal direction. 
     According to another embodiment, there is provided a reactor apparatus comprising: a body defining a reaction chamber; at least one electromagnetic radiation emitter; and at least one lens configured to refract at least some electromagnetic radiation from the at least one electromagnetic radiation emitter into the reaction chamber as refracted electromagnetic radiation skewed laterally relative to the at least some electromagnetic radiation from the at least one electromagnetic radiation emitter and into the reaction chamber. 
     In some embodiments: the body further defines an inlet of the reaction chamber and an outlet of the reaction chamber; and the reaction chamber extends in a longitudinal direction at least between the inlet and the outlet. 
     In some embodiments, the at least one lens is configured to cause the refracted electromagnetic radiation in the reaction chamber to be skewed laterally relative to the longitudinal direction. 
     In some embodiments, the longitudinal direction is parallel to a central longitudinal axis of the reaction chamber. 
     In some embodiments, the inlet is configured to direct fluid into the reaction chamber in an inlet direction non-parallel to the longitudinal direction. 
     In some embodiments, the inlet direction is substantially perpendicular to the longitudinal direction. 
     In some embodiments, the at least one lens is configured to cause fluence rate of the refracted electromagnetic radiation in the reaction chamber and along the inlet direction from the inlet to be higher with increased distance from the inlet. 
     In some embodiments, the at least one lens is configured to cause a fluence rate of the refracted electromagnetic radiation in a first transverse side of the reaction chamber proximate the inlet to be less than a fluence rate of the refracted electromagnetic radiation in a second transverse side of the reaction chamber opposite the first transverse side of the reaction chamber and opposite the inlet. 
     In some embodiments, the inlet is configured to direct fluid into the reaction chamber in an inlet direction substantially parallel to the longitudinal direction. 
     In some embodiments, the at least one lens is configured to cause the refracted electromagnetic radiation in the reaction chamber to be skewed laterally relative to the longitudinal direction and towards an extension in the reaction chamber of the inlet direction from the inlet. 
     In some embodiments, the at least one lens comprises a plurality of lenses spaced apart around an inlet axis extending along the inlet direction. 
     In some embodiments, the plurality of lenses surround the inlet axis. 
     In some embodiments, the at least one electromagnetic radiation emitter comprises at least one emitter of UV radiation. 
     In some embodiments, the at least one emitter of UV radiation comprises at least one UV-LED. 
     In some embodiments, the at least one electromagnetic radiation emitter comprises at least one LED. 
     In some embodiments, the at least one electromagnetic radiation emitter is configured to cause the at least some electromagnetic radiation from the at least one electromagnetic radiation emitter to have a principal radiation direction. 
     In some embodiments, the at least one electromagnetic radiation emitter is configured to cause the at least some electromagnetic radiation from the at least one electromagnetic radiation emitter to be substantially axially symmetric about the principal radiation direction. 
     In some embodiments, the at least one lens is configured to cause the refracted electromagnetic radiation to be distributed axially asymmetrically relative to the principal radiation direction of the at least some electromagnetic radiation from the at least one electromagnetic radiation emitter. In some embodiments, the at least one lens is configured to cause a fluence rate of the refracted electromagnetic radiation on a first transverse side of the principal radiation direction to be greater than a fluence rate of the refracted electromagnetic radiation on a second transverse side of the principal radiation direction opposite the first transverse side of the principal radiation direction. In some embodiments, the at least one lens has an optical axis non-parallel to the principal radiation direction. 
     In some embodiments, the at least one lens has an optical axis parallel to and spaced apart from the principal radiation direction. 
     In some embodiments, the at least one lens comprises an axially asymmetric lens. Other aspects and features will become apparent to those ordinarily skilled in the art upon review of the following description of illustrative embodiments in conjunction with the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a reactor apparatus according to one embodiment. 
         FIG. 2  is a cross-sectional view of the reactor apparatus of  FIG. 1 , taken along the line  2 - 2  in  FIG. 1 . 
         FIG. 3  is a cross-sectional view of a reactor head of the reactor apparatus of  FIG. 1 . 
         FIG. 4  is a cross-sectional view of a reactor head according to another embodiment. 
         FIG. 5  is a cross-sectional view of a reactor head according to another embodiment. 
         FIG. 6  is a cross-sectional view of a reactor head according to another embodiment. 
         FIG. 7  is a cross-sectional view of a reactor head according to another embodiment. 
         FIG. 8  is a cross-sectional view of a reactor head according to another embodiment. 
         FIG. 9  is a cross-sectional view of a reactor head according to another embodiment. 
         FIG. 10  is a perspective view of a reactor head according to another embodiment. 
         FIG. 11  is a side view of the reactor head of  FIG. 10 . 
         FIG. 12  is a perspective view of a reactor head according to another embodiment. 
         FIG. 13  is a side view of the reactor head of  FIG. 12 . 
         FIG. 14  is a perspective view of a reactor head according to another embodiment. 
         FIG. 15  is a cross-sectional view of a reactor apparatus according to another embodiment. 
         FIG. 16  is a cross-sectional view of a reactor apparatus according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 and 2 , a reactor apparatus according to one embodiment is shown generally at  100  and includes a reactor body  102  that defines a reaction chamber  104  that extends in a longitudinal direction  106  between longitudinal ends  108  and  110  of the reaction chamber  104 . The reactor body  102  also defines an inlet  112  of the reaction chamber  104  proximate the longitudinal end  108  and an outlet  114  of the reaction chamber  104  proximate the longitudinal end  110 . The reaction chamber  104  therefore extends in the longitudinal direction  106  at least between the inlet  112  and the outlet  114 . 
     The inlet  112  extends along an inlet axis  116  and is therefore configured to direct fluid into the reaction chamber  104  in an inlet direction  118  that may be an extension of the inlet axis  116  into the reaction chamber  104  and may be substantially perpendicular to the longitudinal direction  106 . However, the inlet direction  118  may differ in other embodiments and may, for example, be in other directions non-parallel to the longitudinal direction  106 . The reaction chamber  104  has a transverse side  120  proximate the inlet  112 , and a transverse side  122  opposite the transverse side  120  and opposite the inlet  112 . In the embodiment shown, because the inlet direction  118  is non-parallel to the longitudinal direction  106 , fluid in the reaction chamber  104  may flow faster in regions of the reaction chamber  104  that are downstream from the inlet  112  than in other regions of the reaction chamber  104 , and fluid in the reaction chamber  104  may flow faster in the transverse side  122  than in the transverse side  120 . 
     The reactor apparatus  100  includes a translucent or transparent wall  124  at the longitudinal end  108 , and a translucent or transparent wall  126  at the longitudinal end  110 . The reactor apparatus  100  also includes a reactor head  128  proximate the longitudinal end  108  and positioned to direct electromagnetic radiation through the translucent or transparent wall  124  and into the reaction chamber  104  from the longitudinal end  108 . The reactor apparatus  100  also includes a reactor head  130  proximate the longitudinal end  110  and positioned to direct electromagnetic radiation through the translucent or transparent wall  126  and into the reaction chamber  104  from the longitudinal end  110 . Therefore, the translucent or transparent walls  124  and  126  may be translucent or transparent electromagnetic radiation from different reactor heads such as those described herein, for example. 
     The reactor head  128  includes a UV light-emitting diode (“UV-LED”)  132 , a lens  134 , and a lens  136 . In the embodiment shown, the lens  134  is a half-ball lens and the lens  136  is a plano-convex lens, although alternative embodiments may differ. At least some UV radiation from the UV-LED  132  may be refracted by the lens  134 , at least some UV radiation refracted by the lens  134  may be refracted by the lens  136 , and at least some UV radiation refracted by the lens  136  may be directed through the translucent or transparent wall  124  and into the reaction chamber  104  from the longitudinal end  108 . Therefore, the UV-LED  132 , the lens  134 , and the lens  136  may collectively function as a UV source (or, more generally, as an electromagnetic radiation source) for a reaction chamber such as reaction chambers described herein, for example. As shown in  FIG. 2 , such UV radiation refracted from the UV-LED  132  and into the reaction chamber  104  from the longitudinal end  108  may be substantially collimated or may be divergent, and a principal radiation direction of such UV radiation refracted from the UV-LED  132  and into the reaction chamber  104  may be substantially parallel to the longitudinal direction  106 . However, alternative embodiments may differ. 
     In general, a principal radiation direction of electromagnetic radiation may be an intensity-weighted average direction of travel of the electromagnetic radiation or may be defined in other ways. In general, electromagnetic radiation may be axially symmetric or may be axially asymmetric about its principal radiation direction. 
     Referring to  FIGS. 2 and 3 , the reactor head  130  includes a UV-LED  138 , a lens  140 , and a lens  142 . In the embodiment shown, the lens  140  is a half-ball lens and the lens  142  is a plano-convex lens, although alternative embodiments may differ. At least some UV radiation from the UV-LED  138  may be refracted by the lens  140 , at least some UV radiation refracted by the lens  140  may be refracted by the lens  142 , and at least some UV radiation refracted by the lens  142  may be directed through the translucent or transparent wall  126  and into the reaction chamber  104  from the longitudinal end  110 . Therefore, the UV-LED  138 , the lens  140 , and the lens  142  may collectively function as a UV source (or, more generally, as an electromagnetic radiation source) for a reaction chamber such as reaction chambers described herein, for example. 
     As shown in  FIG. 3 , the lens  140  has an optical axis  144 , and the lens  142  has an optical axis  146 . Further, in the embodiment shown, the optical axes  144  and  146  are substantially collinear, and UV radiation from the UV-LED  138  may be substantially axially symmetric about the optical axis  144 , although alternative embodiments may differ. However, the optical axes  144  and  146  are non-parallel and oblique to the longitudinal direction  106 . In the embodiment shown, an oblique angle between the optical axes  144  and  146  and the longitudinal direction  106  may be between about  1  degree and about  45  degrees, although alternative embodiments may differ. As a result, as shown in  FIGS. 2 and 3 , UV radiation refracted from the UV-LED  138  and into the reaction chamber  104  from the longitudinal end  110  is skewed laterally relative to the longitudinal direction  106 , and a principal radiation direction  148  of the UV radiation refracted by the lens  142  is an oblique angle  150  from the longitudinal direction  106 . 
     As shown in  FIG. 3 , the UV radiation refracted from the UV-LED  138  and into the reaction chamber  104  from the longitudinal end  110  is skewed laterally relative to the UV radiation refracted from the UV-LED  138  in a transverse direction away from the inlet  112 . As a result, along the inlet direction  118  from the inlet  112 , a fluence rate (density of intensity) or local intensity of the UV radiation refracted from the UV-LED  138  and into the reaction chamber  104  from the longitudinal end  110  increases with increased distance from the inlet  112 . Also, as a result, a fluence rate or local intensity of the UV radiation refracted from the UV-LED  138  and into the transverse side  120  of the reaction chamber  104  from the longitudinal end  110  is less than a fluence rate or local intensity of the UV radiation refracted from the UV-LED  138  and into the transverse side  122  of the reaction chamber  104  from the longitudinal end  110 . 
     As indicated above, in the embodiment shown, fluid in the reaction chamber  104  may flow faster in regions of the reaction chamber  104  that are downstream from the inlet  112  than in other regions of the reaction chamber  104 , and fluid in the reaction chamber  104  may flow faster in the transverse side  122  than in the transverse side  120 . As shown in  FIG. 2 , because the UV radiation refracted from the UV-LED  138  and into the reaction chamber  104  from the longitudinal end  110  is skewed laterally in a transverse direction away from the inlet  112 , UV radiation fluence rate or local intensity in the reaction chamber  104  may correlate with fluid flow velocity in the reaction chamber  104 . In other words, in general, UV radiation fluence rate or local intensity in the reaction chamber  104  may be higher in regions where fluid flow velocity in the reaction chamber  104  may also be higher, and total UV exposure to fluid flowing through the reaction chamber  104  may be more consistent than in other reactor apparatuses without such skewed UV radiation. 
     Referring to  FIG. 4 , a reactor head according to another embodiment is shown generally at  156  and includes a UV-LED  158 , a lens  160  having an optical axis  162 , and a lens  164  having an optical axis  166 . In the embodiment shown, the lens  160  is a half-ball lens and the lens  164  is a plano-convex lens, although alternative embodiments may differ. At least some UV radiation from the UV-LED  158  may be refracted by the lens  160 , at least some UV radiation refracted by the lens  160  may be refracted by the lens  164 , and at least some UV radiation refracted by the lens  164  may be directed into a reaction chamber, for example through the translucent or transparent wall  124  and into the reaction chamber  104  from the longitudinal end  108  or through the translucent or transparent wall  126  and into the reaction chamber  104  from the longitudinal end  110 , or more generally into one or both longitudinal ends of a reaction chamber such as reaction chambers as described herein. Therefore, the UV-LED  158 , the lens  160 , and the lens  164  may collectively function as a UV source (or, more generally, as an electromagnetic radiation source) for a reaction chamber such as reaction chambers described herein, for example. 
     The UV radiation from the UV-LED  158  may be substantially axially symmetric about a principal radiation direction  168 , and the optical axis  162  is substantially collinear with the principal radiation direction  168 , although alternative embodiments may differ. However, the optical axis  166  is non-parallel and oblique to the principal radiation direction  168  and to the optical axis  162 . In the embodiment shown, an oblique angle between the optical axis  166  and the principal radiation direction  168  (or between the optical axis  166  and a longitudinal direction of a reaction chamber, such as the longitudinal direction  106  of the reaction chamber  104 , for example) may be between about  1  degree and about 45 degrees, although alternative embodiments may differ. As a result, UV radiation refracted by the lens  164  is not substantially axially symmetric about the principal radiation direction  168 , but is rather skewed laterally relative to the principal radiation direction  168  and skewed laterally relative to the UV radiation refracted from the UV-LED  158 . In other words, a fluence rate or local intensity of the UV radiation from the UV-LED  158  and refracted by the lenses  160  and  164  is greater on one transverse side of the principal radiation direction  168  (above the principal radiation direction  168  in the orientation of  FIG. 4 ) than on an opposite transverse side of the principal radiation direction  168  (below the principal radiation direction  168  in the orientation of  FIG. 4 ). Further, UV radiation refracted by the lens  164  may be refracted into a reaction chamber, and UV radiation refracted by the lens  164  and into a reaction chamber may be skewed laterally relative to a longitudinal direction of the reaction chamber, similarly to the reactor head  130  as described above with reference to  FIG. 2 , for example. 
     In the embodiment of  FIG. 4 , the UV-LED  158 , the lens  160 , and the lens  164  may be positioned in the reactor head  156  such that the principal radiation direction  168  and the optical axis  162  may be parallel to a longitudinal direction of a reaction chamber (such as the longitudinal direction  106  of the reaction chamber  104 , for example), but alternative embodiments may differ. For example, referring to  FIG. 5 , a reactor head according to another embodiment is shown generally at  170  and includes a UV-LED  172 , a lens  174 , and a lens  176  having an optical axis  178 . The UV-LED  172 , the lens  174 , and the lens  176  may be similar to the UV-LED  158 , the lens  160 , and the lens  164  except that the UV-LED  172 , the lens  174 , and the lens  176  may be positioned in the reactor head  170  such that the optical axis  178  may be parallel to a longitudinal direction of a reaction chamber (such as the longitudinal direction  106  of the reaction chamber  104 , for example). As a result, the reactor head  170  may direct UV radiation into a reaction chamber skewed laterally similarly to the reactor head  130  as described above with reference to  FIG. 2 , for example. 
     Referring to  FIG. 6 , a reactor head according to another embodiment is shown generally at  180  and includes a UV-LED  182 , a lens  184  having an optical axis  186 , and a lens  188  having an optical axis  190 . In the embodiment shown, the lens  184  is a half-ball lens and the lens  188  is a plano-convex lens, although alternative embodiments may differ. At least some UV radiation from the UV-LED  182  may be refracted by the lens  184 , at least some UV radiation refracted by the lens  184  may be refracted by the lens  188 , and at least some UV radiation refracted by the lens  188  may be directed into a reaction chamber, for example through the translucent or transparent wall  124  and into the reaction chamber  104  from the longitudinal end  108  or through the translucent or transparent wall  126  and into the reaction chamber  104  from the longitudinal end  110 , or more generally into one or both longitudinal ends of a reaction chamber such as reaction chambers as described herein. Therefore, the UV-LED  182 , the lens  184 , and the lens  188  may collectively function as a UV source (or, more generally, as an electromagnetic radiation source) for a reaction chamber such as reaction chambers described herein, for example. 
     The UV radiation from the UV-LED  182  may be substantially axially symmetric about a principal radiation direction  192 , and the optical axes  186  and  190  are parallel to and spaced apart from the principal radiation direction  192 . In the embodiment shown, a separation distance between the optical axes  186  and  190  and the principal radiation direction  192  may be about 1% to about 37.5% of a diameter of the lens  184 , although alternative embodiments may differ. As a result, as with the reactor head  156 , UV radiation refracted by the lens  188  is not substantially axially symmetric about the principal radiation direction  192 , but is rather skewed laterally relative to the principal radiation direction  192  and skewed laterally relative to the UV radiation refracted from the UV-LED  182 . In other words, a fluence rate or local intensity of the UV radiation from the UV-LED  182  and refracted by the lenses  184  and  188  is greater on one transverse side of the principal radiation direction  192  (above the principal radiation direction  192  in the orientation of  FIG. 6 ) than on an opposite transverse side of the principal radiation direction  192  (below the principal radiation direction  192  in the orientation of  FIG. 6 ). Further, UV radiation refracted by the lens  188  may be refracted into a reaction chamber, and UV radiation refracted by the lens  188  and into a reaction chamber may be skewed laterally relative to a longitudinal direction of the reaction chamber, similarly to the reactor head  130  as described above with reference to  FIG. 2 , for example. 
     Referring to  FIG. 7 , a reactor head according to another embodiment is shown generally at  194  and includes a UV-LED  196 , a lens  198  having an optical axis  200 , and a lens  202  having an optical axis  204 . In the embodiment shown, the lens  198  is a half-ball lens and the lens  202  is a plano-convex lens, although alternative embodiments may differ. At least some UV radiation from the UV-LED  196  may be refracted by the lens  198 , at least some UV radiation refracted by the lens  198  may be refracted by the lens  202 , and at least some UV radiation refracted by the lens  202  may be directed into a reaction chamber, for example through the translucent or transparent wall  124  and into the reaction chamber  104  from the longitudinal end  108  or through the translucent or transparent wall  126  and into the reaction chamber  104  from the longitudinal end  110 , or more generally into one or both longitudinal ends of a reaction chamber such as reaction chambers as described herein. Therefore, the UV-LED  196 , the lens  198 , and the lens  202  may collectively function as a UV source (or, more generally, as an electromagnetic radiation source) for a reaction chamber such as reaction chambers described herein, for example. 
     The UV radiation from the UV-LED  196  may be substantially axially symmetric about a principal radiation direction  206 , and the optical axis  200  is substantially collinear with the principal radiation direction  206 , although alternative embodiments may differ. However, the optical axis  204  is parallel to and spaced apart from the principal radiation direction  206  and from the optical axis  200 . In the embodiment shown, a separation distance between the optical axis  204  and the optical axis  200  may be about  1 % to about  37 . 5 % of a diameter of the lens  198 , although alternative embodiments may differ. As a result, as with the reactor head  156 , UV radiation refracted by the lens  202  is not substantially axially symmetric about the principal radiation direction  206 , but is rather skewed laterally relative to the principal radiation direction  206  and skewed laterally relative to the UV radiation refracted from the UV-LED  206 . In other words, a fluence rate or local intensity of the UV radiation from the UV-LED  196  and refracted by the lenses  198  and  202  is greater on one transverse side of the principal radiation direction  206  (above the principal radiation direction  206  in the orientation of  FIG. 7 ) than on an opposite transverse side of the principal radiation direction  206  (below the principal radiation direction  206  in the orientation of  FIG. 7 ). Further, UV radiation refracted by the lens  202  may be refracted into a reaction chamber, and UV radiation refracted by the lens  202  and into a reaction chamber may be skewed laterally relative to a longitudinal direction of the reaction chamber, similarly to the reactor head  130  as described above with reference to  FIG. 2 , for example. 
     Referring to  FIG. 8 , a reactor head according to another embodiment is shown generally at  208  and includes a UV-LED  210 , a lens  212  having an optical axis  214 , and a lens  216  having an optical axis  218 . In the embodiment shown, the lens  212  is a half-ball lens and the lens  216  is a plano-convex lens, although alternative embodiments may differ. At least some UV radiation from the UV-LED  210  may be refracted by the lens  212 , at least some UV radiation refracted by the lens  212  may be refracted by the lens  216 , and at least some UV radiation refracted by the lens  216  may be directed into a reaction chamber, for example through the translucent or transparent wall  124  and into the reaction chamber  104  from the longitudinal end  108  or through the translucent or transparent wall  126  and into the reaction chamber  104  from the longitudinal end  110 , or more generally into one or both longitudinal ends of a reaction chamber such as reaction chambers as described herein. Therefore, the UV-LED  210 , the lens  212 , and the lens  216  may collectively function as a UV source (or, more generally, as an electromagnetic radiation source) for a reaction chamber such as reaction chambers described herein, for example. The UV radiation from the UV-LED  210  may be substantially axially symmetric about a principal radiation direction  220 , and the optical axes  214  and  218  are substantially collinear with the principal radiation direction  220 , although alternative embodiments may differ. However, the lens  216  is axially asymmetric. As a result, as with the reactor head  156 , UV radiation refracted by the lens  216  is not substantially axially symmetric about the principal radiation direction  220 , but is rather skewed laterally relative to the principal radiation direction  220  and skewed laterally relative to the UV radiation refracted from the UV-LED  210 . In other words, a fluence rate or local intensity of the UV radiation from the UV-LED  210  and refracted by the lenses  212  and  218  is greater on one transverse side of the principal radiation direction  220  (above the principal radiation direction  220  in the orientation of  FIG. 8 ) than on an opposite transverse side of the principal radiation direction  220  (below the principal radiation direction  220  in the orientation of  FIG. 8 ). Further, UV radiation refracted by the lens  216  may be refracted into a reaction chamber, and UV radiation refracted by the lens  216  and into a reaction chamber may be skewed laterally relative to a longitudinal direction of the reaction chamber, similarly to the reactor head  130  as described above with reference to  FIG. 2 , for example. 
     The reactor heads of  FIGS. 3 to 8  are examples only, and alternative embodiments may differ. For example, each of the reactor heads of  FIGS. 3 to 8  includes a UV-LED, but alternative embodiments may include more than one UV-LED, one or more other LEDs, one or more other emitters of UV radiation that may not necessarily be LEDs or UV-LEDs, or one or more emitters of electromagnetic radiation that may not necessarily be emitters of UV radiation. Further, each of the reactor heads of  FIGS. 3 to 8  includes two lenses, but alternative embodiments may include fewer or more than two lenses. Further, in some embodiments, at least one lens may be incorporated into one or more electromagnetic radiation emitters, and at least one lens may be separate from one or more electromagnetic radiation emitters. 
     As another example, referring to  FIG. 9 , a reactor head according to another embodiment is shown generally at  222  and includes UV-LEDs  224  and  226 , a lens  228  having an optical axis  230 , a lens  232  having an optical axis  234 , and a lens  236  having an optical axis  238 . In the embodiment shown, the lenses  228  and  232  are half-ball lenses and the lens  236  is a biconvex or convex lens, although alternative embodiments may differ. At least some UV radiation from the UV-LED  224  may be refracted by the lens  228 , at least some UV radiation refracted by the lens  228  may be refracted by the lens  236 , and at least some UV radiation refracted by the lens  228  and by the lens  236  may be directed into a reaction chamber, for example through the translucent or transparent wall  124  and into the reaction chamber  104  from the longitudinal end  108  or through the translucent or transparent wall  126  and into the reaction chamber  104  from the longitudinal end  110 , or more generally into one or both longitudinal ends of a reaction chamber such as reaction chambers as described herein. 
     Therefore, the UV-LEDs  224  and  226  and the lenses  228 ,  232 , and  236  may collectively function as a UV source (or, more generally, as an electromagnetic radiation source) for a reaction chamber such as reaction chambers described herein, for example. Further, at least some UV radiation from the UV-LED  226  may be refracted by the lens  232 , at least some UV radiation refracted by the lens  232  may be refracted by the lens  236 , and at least some UV radiation refracted by the lens  232  and by the lens  236  may be directed into the same reaction chamber. 
     The UV radiation from the UV-LED  224  may be substantially axially symmetric about a principal radiation direction  240 , and the optical axis  230  is substantially collinear with the principal radiation direction  240 , although alternative embodiments may differ. Further, the 
     UV radiation from the UV-LED  226  may be substantially axially symmetric about a principal radiation direction  242 , and the optical axis  234  is substantially collinear with the principal radiation direction  242 , although again alternative embodiments may differ. However, the optical axis  238  is non-parallel and oblique to the principal radiation directions  240  and  242  and to the optical axes  230  and  234 . In the embodiment shown, an oblique angle between the optical axis  238  and the principal radiation directions  240  and  242  (or between the optical axis  238  and a longitudinal direction of a reaction chamber, such as the longitudinal direction  106  of the reaction chamber  104 , for example) may be between about  1  degree and about  45  degrees, although alternative embodiments may differ. 
     As a result, as with the reactor head  156 , UV radiation refracted by the lens  238  is not substantially axially symmetric about the principal radiation direction  240  or  242 , but is rather skewed laterally relative to the principal radiation directions  240  and  242  and skewed laterally relative to the UV radiation refracted from the UV-LEDs  224  and  226 . In other words, a fluence rate or local intensity of the UV radiation from the UV-LEDs  224  and  226  and refracted by the lenses  228 ,  232 , and  236  is greater on one transverse side of the principal radiation directions  240  and  242  (above the principal radiation directions  240  and  242  in the orientation of  FIG. 9 ) than on an opposite transverse side of the principal radiation directions  240  and  242  (below the principal radiation directions  240  and  242  in the orientation of  FIG. 9 ). Further, UV radiation refracted by the lens  236  may be refracted into a reaction chamber, and UV radiation refracted by the lens  236  and into a reaction chamber may be skewed laterally relative to a longitudinal direction of the reaction chamber, similarly to the reactor head  130  as described above with reference to  FIG. 2 , for example. 
     Again, the reactor head of  FIG. 9  is an example only, and alternative embodiments may differ. For example, the reactor head of  FIG. 9  includes two UV-LEDs, but alternative embodiments may include fewer or more UV-LEDs, one, two, or more than two other LEDs, one, two, or more than two other emitters of UV radiation that may not necessarily be UV-LEDs, or one, two, or more than two emitters of electromagnetic radiation that may not necessarily be emitters of UV radiation. Further, the reactor head of  FIG. 9  includes three lenses, but alternative embodiments may include fewer or more than three lenses. Further, in some embodiments, at least one lens may be incorporated into one or more electromagnetic radiation emitters, and at least one lens may be separate from one or more electromagnetic radiation emitters. In general, lenses as described herein may be configured to refract electromagnetic radiation from different emitters of electromagnetic radiation such as those described herein, for example. 
     Further, similar to the embodiment of  FIG. 4 , the UV-LEDs  224  and  226  and the lenses  228 ,  232 , and  236  may be positioned in the reactor head  222  such that the principal radiation directions  240  and  242  and the optical axes  230  and  234  may be parallel to a longitudinal direction of a reactor (such as the longitudinal direction  106  of the reaction chamber  104 , for example), but alternative embodiments may differ. For example, similar to the embodiment of  FIG. 5 , the UV-LEDs  224  and  226  and the lenses  228 ,  232 , and  236  may be positioned in the reactor head  222  such that the optical axis  238  may be parallel to such a longitudinal direction of a reactor, and still the reactor head  222  may direct UV radiation into a reaction chamber skewed laterally similarly to the reactor head  130  as described above, for example. 
     The reactor heads of  FIGS. 3 to 9  are examples only, and in general, in different embodiments, electromagnetic radiation (such as UV radiation, for example) may be refracted by at least one lens having an optical axis non-parallel to a longitudinal direction of a reaction chamber (such as the longitudinal direction  106  of the reaction chamber  104 , for example), by at least one lens having an optical axis non-parallel to a principal radiation direction of an emitter of electromagnetic radiation (such as the principal radiation direction  168 ,  192 ,  206 , or  220 , for example), by at least one lens having an optical axis parallel to and spaced apart from the principal radiation direction, by at least one axially asymmetric lens, by one or more other lenses, or by a combination of two or more thereof. 
     Reactor heads according to other embodiments may define one or more fluid conduits that may function as inlets or outlets to reaction chambers. Further, reactor heads according to other embodiments may include more than one electromagnetic radiation emitter. For example, referring to  FIGS. 10 and 11 , a reactor head according to another embodiment is shown generally at  244  and includes a body  246  having opposite sides  248  and  250 . The body  246  defines a fluid conduit  252  extending between the opposite sides  248  and  250 . The fluid conduit  252  extends along an axis  254  and may function as an inlet or as an outlet to a reaction chamber. Therefore, if the fluid conduit  252  functions as an inlet to a reaction chamber, then the fluid conduit  252  is configured to direct fluid into the reaction chamber in an inlet direction  256  that may be an extension of the axis  254  into the reaction chamber. Likewise, if the fluid conduit  252  functions as an outlet to a reaction chamber, then the fluid conduit  252  is configured to direct fluid out of the reaction chamber in an outlet direction that may be an extension of the axis  254 . The reactor head  244  also includes electromagnetic radiation sources  258 ,  260 ,  262 ,  264 ,  266 ,  268 ,  270 , and  272 , although alternative embodiments may include more or fewer electromagnetic radiation sources. Each electromagnetic radiation source may include one or more electromagnetic radiation emitters and one or more lenses such as those described above, for example, although for simplicity,  FIGS. 10 and 11  illustrate only outermost lenses of the electromagnetic radiation emitters. In the embodiment shown, the electromagnetic radiation sources  258 ,  260 ,  262 ,  264 ,  266 ,  268 ,  270 , and  272  are on the side  248  and surround the fluid conduit  252 , although alternative embodiments may differ. 
     The electromagnetic radiation sources  258 ,  260 ,  262 ,  264 ,  266 ,  268 ,  270 , and  272  may be similar to electromagnetic radiation sources as described above and as illustrated in  FIGS. 3 to 9 , for example, and may therefore produce electromagnetic radiation (such as UV radiation, for example) skewed laterally as illustrated in  FIGS. 3 to 9 , for example. Further, in the embodiment shown, the electromagnetic radiation sources  258 ,  260 ,  262 ,  264 ,  266 ,  268 ,  270 , and  272  may produce electromagnetic radiation skewed laterally towards the inlet direction  256 . For example, as shown in  FIG. 11 , a principal radiation direction  272  of electromagnetic radiation from the electromagnetic radiation source  262  is skewed laterally towards the inlet direction  256 , a principal radiation direction  274  of electromagnetic radiation from the electromagnetic radiation source  264  is skewed laterally towards the inlet direction  256 , a principal radiation direction  276  of electromagnetic radiation from the electromagnetic radiation source  268  is skewed laterally towards the inlet direction  256 , and a principal radiation direction  278  of electromagnetic radiation from the electromagnetic radiation source  270  is skewed laterally towards the inlet direction  256 . The principal radiation directions  272 ,  274 ,  276 , and  278  are shown in  FIG. 11  for simplicity, but principal radiation directions of other electromagnetic radiation sources of the reactor head  244  may also be skewed laterally towards the inlet direction  256 . In other words, the reactor head  244  includes a plurality of lenses (namely lenses of the electromagnetic radiation sources  258 ,  260 ,  262 ,  264 ,  266 ,  268 ,  270 , and  272 ) that are spaced apart around, and that surround, an axis that extends along the inlet direction  256  and that are configured to cause refracted electromagnetic radiation to be skewed laterally towards an extension of the inlet direction  256 , although alternative embodiments may differ. 
     Referring to  FIGS. 12 and 13 , a reactor head according to another embodiment is shown generally at  280  and includes electromagnetic radiation sources  282 ,  284 ,  286 ,  288 ,  290 ,  292 ,  294 , and  296 , although alternative embodiments may include more or fewer electromagnetic radiation sources. Again, each electromagnetic radiation source may include one or more electromagnetic radiation emitters and one or more lenses such as those described above, for example, although for simplicity,  FIGS. 12 and 13  illustrate only outermost lenses of the electromagnetic radiation emitters. Also, in the embodiment shown, the electromagnetic radiation sources  282 ,  284 ,  286 ,  288 ,  290 ,  292 ,  294 , and  296  surround a central axis  298  of the reactor head  280 , although alternative embodiments may differ. 
     The electromagnetic radiation sources  282 ,  284 ,  286 ,  288 ,  290 ,  292 ,  294 , and  296  may be similar to the UV-LED  132 , the lens  134 , and the lens  136  shown in  FIG. 2 . Therefore, the electromagnetic radiation sources  282 ,  284 ,  286 ,  288 ,  290 ,  292 ,  294 , and  296  may produce electromagnetic radiation (such as UV radiation, for example) that is substantially collimated or that diverges, and principal radiation directions of electromagnetic radiation produced by the electromagnetic radiation sources  282 ,  284 ,  286 ,  288 ,  290 ,  292 ,  294 , and  296  may be substantially parallel to the central axis  298  of the reactor head  280 . For example, as shown in  FIG. 13 , a principal radiation direction  300  of electromagnetic radiation from the electromagnetic radiation source  286  is substantially parallel to the central axis  298 , a principal radiation direction  302  of electromagnetic radiation from the electromagnetic radiation source  288  is substantially parallel to the central axis  298 , a principal radiation direction  304  of electromagnetic radiation from the electromagnetic radiation source  290  is substantially parallel to the central axis  298 , a principal radiation direction  306  of electromagnetic radiation from the electromagnetic radiation source  292  is substantially parallel to the central axis  298 , and a principal radiation direction  308  of electromagnetic radiation from the electromagnetic radiation source  294  is substantially parallel to the central axis  298 . The principal radiation directions  300 ,  302 ,  304 ,  306 , and  308  are shown in  FIG. 13  for simplicity, but principal radiation directions of other electromagnetic radiation sources of the reactor head  280  may also be substantially parallel to the central axis  298 . 
     Referring to  FIG. 14 , a reactor head according to another embodiment is shown generally at  310  and includes electromagnetic radiation sources  312 ,  314 ,  316 ,  318 ,  320 ,  322 ,  324 ,  326 , and  328 , although alternative embodiments may include more or fewer electromagnetic radiation sources. The electromagnetic radiation sources  312 ,  314 ,  316 ,  318 ,  320 ,  322 ,  324 , and  326  may be similar to the electromagnetic radiation sources  282 ,  284 ,  286 ,  288 ,  290 ,  292 ,  294 , and  296  as described above and surround a central axis  330  of the reactor head  310 , although alternative embodiments may differ. Further, like the electromagnetic radiation sources  282 ,  284 ,  286 ,  288 ,  290 ,  292 ,  294 , and  296 , the electromagnetic radiation sources  312 ,  314 ,  316 ,  318 ,  320 ,  322 ,  324 , and  326  may produce electromagnetic radiation (such as UV radiation, for example) that is substantially collimated or that diverges, and principal radiation directions of electromagnetic radiation produced by the electromagnetic radiation sources  312 ,  314 ,  316 ,  318 ,  320 ,  322 ,  324 , and  326  may be substantially parallel to the central axis  330  of the reactor head  310 . 
     The electromagnetic radiation source  328  may be positioned along the central axis  330  so that the electromagnetic radiation sources  312 ,  314 ,  316 ,  318 ,  320 ,  322 ,  324 , and  326  also surround the electromagnetic radiation source  328 . Like the electromagnetic radiation sources  312 ,  314 ,  316 ,  318 ,  320 ,  322 ,  324 , and  326 , the electromagnetic radiation source  328  may also produce electromagnetic radiation (such as UV radiation, for example) that is substantially collimated or that diverges, and a principal radiation direction of electromagnetic radiation produced by the electromagnetic radiation source  328  may also be substantially parallel to the central axis  330  of the reactor head  310 . In some embodiments, the electromagnetic radiation source  328  may be larger and/or may produce electromagnetic radiation at more power or intensity than the electromagnetic radiation sources  312 ,  314 ,  316 ,  318 ,  320 ,  322 ,  324 , and  326  individually. 
     In general, reactor heads such as those described above may direct electromagnetic radiation (such as UV radiation, for example) into different reaction chambers of different reactor apparatuses. In some embodiments, such reaction chambers may have longitudinal ends, and such reactor heads may be positioned to direct electromagnetic radiation into such reaction chambers from one or both of such longitudinal ends. 
     For example, referring to  FIG. 15 , a reactor apparatus according to another embodiment is shown generally at  332  and includes a reactor body  134  that defines a reaction chamber  336  that extends in a longitudinal direction  338  between longitudinal ends  340  and  342  of the reaction chamber  336 . 
     The reactor apparatus  332  also includes a reactor head  344  proximate the longitudinal end  340  and positioned to direct electromagnetic radiation into the reaction chamber  336  from the longitudinal end  340 . The reactor head  344  may be similar to the reactor head  244 . 
     Therefore, the reactor head  344  defines an inlet  346  to the reaction chamber  336  proximate the longitudinal end  340 , the inlet  346  extends along an inlet axis  348 , and the inlet  346  is configured to direct fluid into the reaction chamber  336  in an inlet direction that may be an extension of the inlet axis  348  into the reaction chamber  336 . In the embodiment shown, the inlet axis  348  and the inlet direction are substantially collinear with or parallel to a central longitudinal axis  350  of the reaction chamber  336  extending in the longitudinal direction  338 , but alternative embodiments may differ. 
     Fluid in the reaction chamber  336  may flow faster in regions of the reaction chamber  336  that are downstream from the inlet  346  than in other regions of the reaction chamber  336 . Also, because the reactor head  344  may be similar to the reactor head  244 , principal radiation directions of electromagnetic radiation sources of the reactor head  344  may also be skewed laterally towards the inlet direction and thus towards the central longitudinal axis  350  of the reaction chamber  336 , as shown in  FIG. 15 , but again alternative embodiments may differ. 
     Because fluid in the reaction chamber  336  may flow faster in regions of the reaction chamber  336  that are downstream from the inlet  346  than in other regions of the reaction chamber  336 , and because principal radiation directions of electromagnetic radiation sources of the reactor head  344  may be skewed laterally towards the inlet direction as shown in  FIG. 15 , a UV fluence rate (density of UV intensity) or local UV intensity in the reaction chamber  336  may, in general, be higher in regions where fluid flow velocity in the reaction chamber  336  may also be higher, and total UV exposure to fluid flowing through the reaction chamber  336  may be more consistent than in other reactor apparatuses without such skewed UV radiation. 
     The reactor body  334  also defines an outlet  352  of the reaction chamber  336  proximate the longitudinal end  342 . The reaction chamber  336  therefore extends in the longitudinal direction  338  at least between the inlet  346  and the outlet  352 . 
     The reactor apparatus  332  also includes a reactor head  354  proximate the longitudinal end  342  and positioned to direct electromagnetic radiation into the reaction chamber  336  from the longitudinal end  342 . The reactor head  354  may be similar to the reactor head  280  or the reactor head  310 . Therefore, electromagnetic radiation from electromagnetic radiation sources of the reactor head  354  may be substantially collimated or may be divergent, and principal radiation directions of electromagnetic radiation sources of the reactor head  354  may be substantially parallel to a central axis  356  of the reactor head  354 , as shown in  FIG. 15 , but again alternative embodiments may differ. In the embodiment shown, the central axis  356  of the reactor head  354  is substantially collinear with or parallel to the central longitudinal axis  350  of the reaction chamber  336 , so the principal radiation directions of electromagnetic radiation sources of the reactor head  354  may be substantially parallel to the central longitudinal axis  350  of the reaction chamber  336 , but again alternative embodiments may differ. 
     Referring to  FIG. 16 , a reactor apparatus according to another embodiment is shown generally at  358  and includes a reactor body  360  that defines a reaction chamber  362  that extends in a longitudinal direction  364  between longitudinal ends  366  and  368  of the reaction chamber  362 . 
     The reactor apparatus  358  also includes a reactor head  370  proximate the longitudinal end  366  and positioned to direct electromagnetic radiation into the reaction chamber  362  from the longitudinal end  366 . The reactor head  370  may be similar to the reactor head  244  and defines an inlet  372  to the reaction chamber  362  proximate the longitudinal end  366 . Therefore, the inlet  372  extends along an inlet axis  374 , and the inlet  372  is configured to direct fluid into the reaction chamber  362  in an inlet direction that may be an extension of the inlet axis  374  into the reaction chamber  362 . In the embodiment shown, the inlet axis  374  and the inlet direction are substantially collinear with or parallel to a central longitudinal axis  376  of the reaction chamber  362  extending in the longitudinal direction  364 , but alternative embodiments may differ. Because the reactor head  370  may be similar to the reactor head  244 , principal radiation directions of electromagnetic radiation sources of the reactor head  370  may also be skewed laterally towards the inlet direction and thus towards the central longitudinal axis  376  of the reaction chamber  362 , as shown in  FIG. 16 , but again alternative embodiments may differ. 
     The reactor apparatus  358  also includes a reactor head  378  proximate the longitudinal end  368  and positioned to direct electromagnetic radiation into the reaction chamber  362  from the longitudinal end  368 . The reactor head  378  may be similar to the reactor head  244  and defines an outlet  380  to the reaction chamber  362  proximate the longitudinal end  366 . Therefore, the reaction chamber  362  extends in the longitudinal direction  364  at least between the inlet  372  and the outlet  380 . Further, the outlet  380  extends along an outlet axis  382 . In the embodiment shown, the outlet axis  382  is substantially collinear with or parallel to the central longitudinal axis  376  of the reaction chamber  362 , but alternative embodiments may differ. Because the reactor head  378  may be similar to the reactor head  244 , principal radiation directions of electromagnetic radiation sources of the reactor head  378  may also be skewed laterally towards the central longitudinal axis  376  of the reaction chamber  362 , as shown in  FIG. 16 , but again alternative embodiments may differ. 
     Fluid in the reaction chamber  362  may flow faster in regions of the reaction chamber  362  that are downstream from the inlet  372  and that are upstream from the outlet  380  than in other regions of the reaction chamber  362 . Because principal radiation directions of electromagnetic radiation sources of the reactor heads  370  and  378  may be skewed laterally towards the central longitudinal axis  376  of the reaction chamber  362 , as shown in  FIG. 16 , UV radiation fluence rate or local intensity in the reaction chamber  362  may, in general, be higher in regions where fluid flow velocity in the reaction chamber  362  may also be higher, and total UV exposure to fluid flowing through the reaction chamber  362  may be more consistent than in other reactor apparatuses without such skewed UV radiation. 
     The reactor apparatuses and reactor heads described above are examples only, and alternative embodiments may differ. For example, reactor heads according to alternative embodiments may include different combinations of one or more electromagnetic radiation emitters and one or more lenses that may skew electromagnetic radiation from the one or more electromagnetic radiation emitters laterally similarly to the embodiments described above, or in different ways. 
     Further, reactor apparatuses according to alternative embodiments may have one or more inlets, one or more outlets, one or more reaction chambers, and one or more reactor heads that may be similar to the embodiments described above, or that may vary in different ways. For example, reactor apparatuses according to alternative embodiments may define one or more than one reaction chamber, and may include one, two, or more than two reactor heads such as those described herein positioned to direct electromagnetic radiation into each such reaction chamber. 
     In general, embodiments such as those described herein may involve laterally skewed electromagnetic radiation in a reaction chamber such that UV radiation fluence rate or local intensity in the reaction chamber may, in general, be higher in regions where fluid flow velocity in the reaction chamber may also be higher, and total UV exposure to fluid flowing through the reaction chamber may be more consistent than in other reactor apparatuses without such skewed UV radiation. Such relatively more consistent total UV exposure may enhance treatment of fluid that flows in the reaction chamber and may, for example, deactivate pathogens in the fluid more effectively than in other reactor apparatuses without such skewed UV radiation. 
     Although specific embodiments have been described and illustrated, such embodiments should be considered illustrative only and not as limiting the invention as construed according to the accompanying claims.