Photocatalytic air treatment

Abstract

A photocatalytic reactor is provided, comprising a reaction chamber arranged to receive an airflow containing one or more airborne pollutants. The reaction chamber comprises a first inner surface, a second inner surface, photocatalysts disposed on both the first inner surface and the second inner surface for photocatalytic decomposition of one or more of the pollutants, and a light source arranged to illuminate at least a portion of the photocatalysts disposed on the first inner surface and the second inner surface. The first inner surface and the second inner surface have distinct parabolic contours, and the contour of the first inner surface is a mirror image of the contour of the second inner surface. The first inner surface and the second inner surface may be continuous.

Description

[Technical field]

[0001] The present invention relates to a photocatalytic reactor for treating an air stream and to an air treatment device comprising a photocatalytic reactor. [Background technology]

[0002] Air treatment devices treat the air to remove contaminants. Traditional air treatment devices use particulate filters alone, which physically trap airborne particles by size exclusion, and high-efficiency particulate air (HEPA) filters, which remove at least 99.97% of 0.3 μm particles. Some air treatment devices use activated carbon filters to filter volatile chemicals from the air. When used to purify the air, activated carbon has a limited removal capacity because it removes contaminants by adsorption, and as a result, the activated carbon filter must be replaced if filtration performance is to be maintained. Rather than trapping the contaminants, it is possible to destroy certain air pollutants using techniques such as photocatalytic oxidation (PCO). Photocatalytic oxidation can be used to oxidize harmful air pollutants into less harmful compounds, for example, to oxidize volatile organic compounds (VOCs) to carbon dioxide and water. The reaction is catalyzed by a catalytic surface that is activated by the absorption of photons. Moisture and oxygen in the air provide the hydrogen and oxygen atoms necessary for the reaction to proceed, so no reactive chemicals are consumed other than the pollutants. Summary of the Invention

[0003] According to a first aspect of the present invention, there is provided a photocatalytic reactor comprising a reaction chamber arranged to receive an airflow containing one or more airborne pollutants. The reaction chamber comprises a first inner surface, a second inner surface, a photocatalyst for photocatalytic decomposition of one or more pollutants arranged on both the first inner surface and the second inner surface, and a light source arranged on the first inner surface and the second inner surface to illuminate at least a portion of the photocatalyst. The first inner surface and the second inner surface have distinct parabolic shaped contours, the contour of the first inner surface being a mirror image of the contour of the second inner surface. The first inner surface and the second inner surface may be continuous.

[0004] The light source may include a light emitting diode. The first and second inner surfaces may be symmetrically arranged about an optical axis of the light emitting diode. The first and second inner surfaces may be arranged such that at least a portion of the first inner surface is illuminated by a first half of the light emitting diode, and such that at least a portion of the second inner surface is illuminated by a second half of the light emitting diode.

[0005] The light source may comprise a plurality of light emitting diodes arranged to each illuminate at least a portion of both the first and second inner surfaces, the first and second inner surfaces being symmetrically arranged about an optical axis of each of the plurality of light emitting diodes. The plurality of light emitting diodes may be distributed to each illuminate a different length portion of both the first and second inner surfaces. The reaction chamber may be elongate in shape, and the plurality of light emitting diodes are aligned longitudinally.

[0006] The reaction chamber may include an air inlet and an air outlet and may be positioned such that air flow passing between the air inlet and the air outlet contacts the photocatalyst.

[0007] The reaction chamber may include at least one layer of transparent material that separates the photocatalyst from the light source.

[0008] The first inner surface and the second inner surface may be separated from the outermost surface of the at least one layer of transmissive material by a distance of at most 10 mm or less, preferably 7 mm or less, preferably between 1 mm and 7 mm.

[0009] The photocatalytic reactor may include a plurality of reaction chambers. The plurality of reaction chambers may be distributed around a common axis, each reaction chamber being arranged such that the first and second inner surfaces face inward and the light source is centrally located relative to the first and second inner surfaces. The plurality of reaction chambers may be arranged in series. The plurality of reaction chambers may be arranged such that the arrangement has rotational symmetry around the common axis, preferably n-fold rotational symmetry, where n is equal to the number of reaction chambers.

[0010] According to a second aspect of the present invention there is provided an air treatment device comprising a photocatalytic reactor according to the first aspect. [Brief description of the drawings]

[0011] [Figure 1A] FIG. 1 is a perspective view of an example of a photocatalytic reactor for use in an air treatment device. [Figure 1B] FIG. 1B is an end view of the photocatalytic reactor of FIG. 1A. [Figure 2A] FIG. 2 is a perspective view of an example of a further photocatalytic reactor for use in an air treatment device. [Figure 2B] FIG. 2B is an end view of the photocatalytic reactor of FIG. 2A. [Figure 3A] FIG. 2 is a perspective view of another example photocatalytic reactor for use in an air treatment device. [Figure 3B] FIG. 3B is an end view of the photocatalytic reactor of FIG. 3A. [Figure 4] FIG. 2 is an end view of an example of a further photocatalytic reactor for use in an air treatment device. [Figure 5A] FIG. 2 is a perspective view of another example of an alternative photocatalytic reactor for use in an air treatment device. [Figure 5B] FIG. 5B is an end view of the photocatalytic reactor of FIG. 5A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An example of an improved photocatalytic reactor will now be described, by way of example only, with reference to Figures 1A and 1B. The photocatalytic reactor is generally designated by reference numeral 1000. The photocatalytic reactor 1000 comprises a reaction chamber 1001 arranged to receive an airflow containing one or more airborne pollutants, and a photocatalyst 1004 for photocatalytic decomposition of the one or more pollutants, the photocatalyst 1004 being disposed on a substrate 1003 provided by the reaction chamber 1001. The photocatalytic reactor 1000 further comprises a light emitting diode printed circuit board ("LED PCB") 1012 comprising a printed circuit board 1008 having a plurality of light emitting diodes 1009 attached to a first side 1006 of the printed circuit board 1008. The photocatalytic reactor 1000 is arranged such that the substrate 1003 is illuminated by the light emitting diodes 1009 to facilitate the photocatalytic decomposition. In particular, the substrate 1003 is positioned to intercept the LED PCB 1012 such that light emitted from the light emitting diodes 1009 of the LED PCB 1012 impinges on the substrate 1003 .

[0013] In the example shown in Figures 1A and 1B, the photocatalytic reactor 1000 comprises an elongated reaction chamber 1001 surrounding an elongated LED PCB 1012 extending along the length of the reaction chamber 1001. The reaction chamber 1001 comprises a reaction chamber inlet (not shown) at a first end of the reaction chamber 1001 and a reaction chamber outlet (not shown) at a second end of the reaction chamber 1001, and air flow passing between the reaction chamber inlet and the reaction chamber outlet contacts a photocatalyst 1004 disposed on a substrate 1003. A partition / barrier 1005A, 1005B then separates the reaction chamber of the photocatalyst 1004 from the LED PCB 1012, and at least a portion of the partition 1005A, 1005B is transparent to radiation emitted by the light emitting diode 1009, so that the photocatalyst 1004 can be illuminated by the light emitting diode 1009. The multiple light emitting diodes 1009 of the LED PCB 1012 are then spaced apart and aligned longitudinally along a first side 1006 of the length of the LED PCB 1012 , thereby providing a light source along the entire length of the photocatalytic reactor 1000 .

[0014] In the example shown in Figures 1A and 1B, the substrate 1003 of the reaction chamber 1001 comprises a plurality of protrusions provided by fins 1011A, 1011B each extending inwardly away from the inner surface of the reaction chamber 1001, and a photocatalyst 1004 is disposed on at least one surface of each fin 1011A, 1011B. These fins 1011A, 1011B provide a high surface area for the photocatalytic decomposition of pollutants. Each fin 1011A, 1011B is elongated and has a length L along the length of the elongated reaction chamber 1001 and a height H defined by how far the fins 1011A, 1011B extend inwardly away from the respective inner surface of the reaction chamber 1001. Thus, the fins 1011A, 1011B are elongated in shape, and the longitudinal axis of each fin 1011A, 1011B is perpendicular to the optical axis of the light emitting diode 1009. The fins 1011A, 1011B thus define a channel 1002 extending along the length of the reaction chamber 1001 for the flow of air from the air inlet to the air outlet between the fins 1011A, 1011B. In the illustrated example, each fin 1011A, 1011B has a cross-section (i.e., the fin profile) that is partially curved along its height. However, in alternative arrangements, each fin 1011A, 1011B may have a straight cross-section.

[0015] The fins 1011A, 1011B comprise a first set of fins 1011A and a second set of fins 1011B, and a photocatalyst 1004 is disposed on each fin. The first set of fins 1011A and the second set of fins 1011B are disposed such that light from the light emitting diodes 1009 illuminates at least a portion of the length of the face 1013 of each fin 1011A, 1011B along the entire height of the face 1013. In other words, each light emitting diode 1009 illuminates the entire height of at least one face 1013 of each fin 1011A, 1011B without receiving a shadow from an adjacent fin. However, multiple light emitting diodes (e.g., multiple light emitting diodes distributed in the longitudinal direction) 1009 may be required to illuminate the entire length of the fins 1011A, 1011B. The light emitting diodes 1009 are distributed so as to each illuminate different, but possibly overlapping, portions of the length of at least one face 1013 of each fin 1011A, 1011B.

[0016] 1A and 1B, each of the first set of fins 1011A is positioned such that a line extending from the base end 1015 of the fin 1011A through the tip 1016 of the fin (e.g., a line extending along the height of the fin and similar to a chord line) is directed to a first convergence point or intersection point F1. Then, each of the second set of fins 1011B is positioned such that a line extending from the base end 1015 of the fin 1011B through the tip 1016 of the fin 1011B is directed to a second convergence point F2. The first convergence point F1 is different from the second convergence point F2, and both the first convergence point F1 and the second convergence point F2 are offset relative to the position of the light emitting diode 1009.

[0017] A first set of fins 1011A extends inward from a first inner surface 1018A of the reaction chamber 1001, and a second set of fins 1011B extends inward from a second inner surface 1018B of the reaction chamber 1001, with the first inner surface 1018A and the second inner surface 1018B generally facing the light-emitting diodes 1009. The first inner surface 1018A and the second inner surface 1018B are symmetrically arranged around the optical axis O of the light-emitting diodes, such that the first set of fins 1011A is arranged to be illuminated by a first half of each light-emitting diode 1009, and the second set of fins 1011B is arranged to be illuminated by a second half of each light-emitting diode 1009. In the example shown in FIGS. 1A and 1B, the photocatalyst 1004 is also arranged on both the first inner surface 1018A and the second inner surface 1018B of the reaction chamber 1001.

[0018] The first inner surface 1018A and the second inner surface 1018B have distinct arc-shaped profiles (i.e., their cross sections are curved segments with different foci), and the profile of the first inner surface 1018A is a mirror image of the profile of the second inner surface 1018B. In other words, the first inner surface 1018A and the second inner surface 1018B are reflections of each other, such that they both have mirror / reflection symmetry. The first inner surface 1018A and the second inner surface 1018B can each have either an arc-shaped profile or a parabolic profile.

[0019] In the example shown in Figures 1A and 1B, the partition 1005A, 1005B comprises two layers of transparent material disposed between and separating the light emitting diode 1009 and the photocatalyst 1004. These two layers of transparent material comprise a first layer of transparent material 1005A separated from a second layer of transparent material 1005B by a gap. These layers of transparent material 1005A, 1005B are impermeable to air and transparent to radiation emitted by the light emitting diode 1009. In the example shown in Figures 1A and 1B, the two layers of transparent material 1005A, 1005B are tubular and disposed concentrically around the LED PCB 1012, the innermost of these tubes providing a conduit within which the LED PCB 1012 is located and disposed such that airflow can pass through the conduit to cool the light emitting diode 1009.

[0020] By providing a double layer barrier between the light emitting diodes 1009 and the photocatalyst 1004, heat loss between the first portion 1019 of the reaction chamber 1001 arranged to receive the contaminant-containing airflow and the second portion 1020 housing the LED PCB 1012 is reduced, thereby improving energy efficiency. This reduced heat loss is particularly beneficial when implementing active cooling of the light emitting diodes 1009.

[0021] 2A and 2B show a further example of an improved photocatalytic reactor. The photocatalytic reactor is generally indicated by reference number 2000. The photocatalytic reactor 2000 comprises a reaction chamber 2001 arranged to receive an airflow containing one or more airborne pollutants, and a photocatalyst 2004 for photocatalytic decomposition of the one or more pollutants, the photocatalyst 2004 being disposed on a substrate 2003 provided by the reaction chamber 2001. The photocatalytic reactor 2000 is very similar to that described above with reference to FIGS. 1A and 1B, and therefore corresponding reference numbers are used for similar or corresponding parts or features of these embodiments. In particular, the photocatalytic reactor 2000 comprises an elongated reaction chamber 2001 surrounding an elongated LED PCB 2012 extending along the length of the reaction chamber 2001. The reaction chamber 2001 comprises a reaction chamber inlet (not shown) at a first end of the reaction chamber 2001 and a reaction chamber outlet (not shown) at a second end of the reaction chamber 2001, and airflow passing between the reaction chamber inlet and the reaction chamber outlet contacts a photocatalyst 2004 disposed on a substrate 2003. A partition / barrier 2005 then separates the reaction chamber 2001 from an LED PCB 2012, and at least a portion of this partition 2005 is transparent to radiation emitted by the light emitting diodes 2009, 2010, so that the photocatalyst 2004 can be illuminated by the light emitting diodes 2009, 2010.

[0022] In the example shown in Figures 2A and 2B, the LED PCB 2012 is double-sided. Thus, the LED PCB 2012 comprises a printed circuit board 2008 having a plurality of first light emitting diodes 2009 mounted on a first side 2006 of the printed circuit board and a plurality of second light emitting diodes 2010 mounted on a second side 2007 of the printed circuit board. Thus, the LED PCB 2012 comprises either a double-sided circuit board or a multi-layer circuit board. The first light emitting diodes 2009 of the LED PCB 2012 are spaced apart and aligned longitudinally along the first side 2006 of the length of the LED PCB 2012, and the second light emitting diodes 2010 are spaced apart and aligned longitudinally along the second side 2007 of the length of the LED PCB 2012, thereby providing a light source along the entire length of the photocatalytic reactor 2000.

[0023] Next, to promote photocatalytic decomposition, the photocatalytic reactor 2000 is positioned such that the substrate 2003 is illuminated by both the first light emitting diode 2009 and the second light emitting diode 2010. In particular, the substrate 2003 is positioned to block the LED PCB 2012, and the light emitted from the light emitting diodes 2009, 2010 of the LED PCB 2012 impinges on the substrate 2003. For this purpose, the substrate 2003 is positioned to surround the LED PCB 2012.

[0024] 2A and 2B, the reaction chamber 2001 of the photocatalytic reactor 2000 is also double-sided. Thus, the reaction chamber 2001 comprises a first side 2001A and a second side 2001B, the first side 2001A being arranged to be illuminated by a first light emitting diode 2009 provided on the first side 2006 and the second side 2001B of the printed circuit board 2008, and a second light emitting diode 2010 provided on the second side 2007 of the printed circuit board 2008.

[0025] By providing a double-sided photocatalytic reactor, the length of the reactor is reduced without compromising the overall volume, which is particularly important when integrating the photocatalytic reactor into a home air treatment device, and reduces the cost of materials, particularly those associated with the bulkheads 2005A, 2005B and the printed circuit board 2008.

[0026] The first side 2001A and the second side 2001B of the reaction chamber 2001 then replicate the finned arrangement of the reaction chamber 1001 shown in Figures 1A and 1B, respectively. Specifically, the first side 2001A of the reaction chamber 2001 comprises a first set of fins 2011A and a second set of fins 2011B, and the second side 2001B of the reaction chamber 2001 comprises a third set of fins 2011C and a fourth set of fins 2011D, with the photocatalyst 2004 disposed on at least one face 2013 of each fin 2011. The first set of fins 2011A and the second set of fins 2001B are positioned such that light from the first light emitting diodes 2009 illuminates at least a portion of the length of the face 2013 of each fin 2011A, 2011B along the entire height of the face 2013. The third set of fins 2011C and the fourth set of fins 2011D are then positioned such that light from the second light emitting diode 2010 illuminates at least a portion of the length of the face 2013 of each fin 2011C, 2011D along the entire height of the face 2013.

[0027] On the first side 2001A of the reaction chamber 2001, each of the first set of fins 2011A is positioned such that a line extending from the base end 2015 of the fin 2011A through the tip 2016 of the fin (e.g., a line extending along the height of the fin and similar to a chord line) is directed to a first convergence point or intersection point F1. Then, each of the second set of fins 2011B is positioned such that a line extending from the base end 2015 of the fin 2011B through the tip 2016 of the fin 2011B is directed to a second convergence point F2. The first convergence point F1 is different from the second convergence point F2, and both the first convergence point F1 and the second convergence point F2 are offset relative to the position of the first light emitting diode 2009.

[0028] Correspondingly, on the second side 2001B of the reaction chamber 2001, each of the third set of fins 2011C is positioned such that a line extending from the base end 2015 of the fin 2011C through the tip end 2016 of the fin is directed to a third convergence point or intersection point F3. Then, each of the fourth set of fins 2011D is positioned such that a line extending from the base end 2015 of the fin 2011D through the tip end 2016 of the fin 2011D is directed to a fourth convergence point F4. The third convergence point F3 is different from the fourth convergence point F4, and both the third convergence point F3 and the fourth convergence point F4 are offset relative to the position of the second light emitting diode 2010.

[0029] A first set of fins 2011A extend inwardly from a first inner surface 2018A on a first side 2001A of the reaction chamber 2001, and a second set of fins 2011B extend inwardly from a second inner surface 2018B on a first side 2001B of the reaction chamber 2001, the first inner surface 2018A and the second inner surface 2018B generally facing the first light emitting diode 2009. A third set of fins 2011C extend inwardly from a third inner surface 2018C on the second side 2001B of the reaction chamber 2001, and a fourth set of fins 2011D extend inwardly from a fourth inner surface 2018D on the second side 2001B of the reaction chamber 2001, the third inner surface 2018C and the fourth inner surface 2018D generally facing the second light emitting diode 2010.

[0030] As can be seen in Figures 2A and 2B, the LED PCB 2012 is centrally located within the spatial volume defined by the substrate 2003. A partition wall 2005 then comprises a single layer of transparent material disposed between and separating the light emitting diodes 2009, 2010 and the photocatalyst 2004. This layer of transparent material is impermeable to air and transmits radiation emitted by the light emitting diodes 2009, 2010. In the example shown in Figures 2A and 2B, the single layer of transparent material 2005 is tubular and disposed concentrically around the LED PCB 3012. This tube of transparent material 2005 provides a conduit within which the LED PCB 1012 is located and is disposed to allow airflow to pass through the conduit to cool the light emitting diodes 2009, 2010.

[0031] Those skilled in the art will appreciate that it is possible to combine key features of the photocatalytic reactors of Figures 1A, 1B, 1A and 1B. Accordingly, a further example of an improved photocatalytic reactor will now be described with reference to Figures 3A and 3B. The photocatalytic reactor is generally designated by reference number 3000. The photocatalytic reactor 3000 comprises a reaction chamber 3001 arranged to receive an airflow containing one or more airborne pollutants, and a photocatalyst 3004 for photocatalytic decomposition of the one or more pollutants, the photocatalyst 3004 being disposed on a substrate 3003 provided by the reaction chamber 3001. The photocatalytic reactor 3000 is very similar to that described above with reference to Figures 2A and 2B, and therefore corresponding reference numbers are used for similar or corresponding parts or features of these embodiments. In particular, the photocatalytic reactor 3000 comprises an elongated reaction chamber 3001 surrounding an elongated LED PCB 3012 extending along the length of the reaction chamber 3001. The reaction chamber 3001 comprises a reaction chamber inlet (not shown) at a first end of the reaction chamber 3001 and a reaction chamber outlet (not shown) at a second end of the reaction chamber 3001, and the air flow passing between the reaction chamber inlet and the reaction chamber outlet contacts the photocatalyst 3004 disposed on the substrate 3003. A partition / barrier 3005A, 3005B then separates the reaction chamber 3001 from the LED PCB 3012, and at least a portion of the partition 3005A, 3005B is transparent to the radiation emitted by the light emitting diodes 3009, 3010, so that the photocatalyst 3004 can be illuminated by the light emitting diodes 3009, 3010.

[0032] In the example shown in Figures 3A and 3B, both the LED PCB 3012 and the reaction chamber 3001 have two sides. However, unlike the example shown in Figures 2A and 2B, the partition 3005A, 3005B separating the photocatalyst 304 from the LED PCB 3012 comprises two layers of transparent material. These two layers of transparent material comprise a first layer of transparent material 3005A separated from a second layer of transparent material 3005B by a gap. The transparent materials 3005A, 3005B of these layers are impermeable to air and permeable to radiation emitted by the light emitting diodes 3009, 3010. In the example shown in Figures 3A and 3B, the two layers of transparent material 3005A, 3005B are tubular and are arranged concentrically around the LED PCB 3012, the innermost of these tubes providing a conduit within which the LED PCB 3012 is located and allowing airflow to pass through the conduit to cool the light emitting diodes 3009, 3010.

[0033] A further example of an improved photocatalytic reactor is described with reference to Figure 4. The photocatalytic reactor is generally designated by reference numeral 4000 and is shown in cross section in Figure 4. The photocatalytic reactor 4000 comprises three reaction chambers 4001, 4101, 4201 each arranged to receive an airflow containing one or more airborne pollutants, and a photocatalyst 4004 for photocatalytic decomposition of the one or more pollutants, the photocatalyst 4004 being disposed on a substrate 4003 provided by each of the reaction chambers 4001, 4101, 4201. The photocatalytic reactor 4000 further comprises a light emitting diode printed circuit board ("LED PCB") 4012, 4112, 4212 within each of the reaction chambers 4012, 4112, 4212. Each LED PCB 4012, 4112, 4212 comprises a printed circuit board 4008 having a plurality of light emitting diodes 4009 attached to a first side of the printed circuit board 4008. The photocatalytic reactor 4000 is positioned such that the substrate 4003 provided by each of the reaction chambers 4001, 4101, 4201 is illuminated by the light emitting diodes 4009 of the corresponding LED PCB 4012, 4112, 4212 to facilitate photocatalytic decomposition. In particular, the substrate 4003 provided by each of the reaction chambers 4012, 4112, 4212 is positioned to shade the corresponding LED PCB 4012, 4112, 4212, such that light emitted from the light emitting diodes 4009 of the LED PCB 4012, 4112, 4212 impinges on the substrate 4003.

[0034] In the example shown in FIG. 4, each of the reaction chambers 4001, 4101, 4201 is elongated and surrounds a respective elongated LED PCB 4012, 4112, 4212 that extends along the length of the reaction chamber 4001, 4101, 4201. Each of the reaction chambers 4001, 4101, 4201 includes a reaction chamber inlet (not shown) at a first end of the reaction chamber and a reaction chamber outlet (not shown) at a second end of the reaction chamber, and airflow passing between the reaction chamber inlet and the reaction chamber outlet contacts a photocatalyst 4004 disposed on a substrate 4003. A partition / barrier 4005 then separates the photocatalyst 4004 from each LED PCB 4012, 4112, 4212, and at least a portion of the partition 4005 is transparent to radiation emitted by the light emitting diode 4009, and the photocatalyst 4004 can be illuminated by the light emitting diode 4009. In turn, the multiple light emitting diodes 4009 of each LED PCB 4012, 4112, 4212 are spaced apart and aligned longitudinally along a first side of the length of the printed circuit board 4008, thereby providing a light source along the entire length of the respective reaction chamber 4001, 4101, 4201.

[0035] In the example shown in Figure 4, the substrate 4003 of each reaction chamber 4001, 4101, 4201 includes a plurality of protrusions provided by fins 4011A, 4011B each extending inwardly away from the inner surface of the reaction chamber 4001A, 4001B, 4001C, and a photocatalyst 4004 is disposed on at least one side of each fin 4011A, 4011B. These fins 4011A, 4011B provide a high surface area for the photocatalytic decomposition of pollutants. Each fin 4011A, 4011B is elongated and has a length along the length of the elongated reaction chamber 4001A, 4001B, 4001C and a height defined by how far the fin 4011A, 4011B extends inwardly away from the inner surface of the reaction chamber 4001, 4101, 4201, respectively. The fins 4011A, 4011B are thus elongate in shape, with the longitudinal axis of each fin 4011A, 4011B being perpendicular to the optical axis of the light emitting diode 4009. The fins 4011A, 4011B thus define between them a channel 4002 extending along the length of the respective reaction chamber 4001, 4101, 4201 for the flow of air from the air inlet to the air outlet. In the illustrated example, each fin 4011A, 4011B has a straight cross section (i.e., the profile of the fin) along its height. However, in an alternative arrangement, each fin 4011A, 4011B may have a curved cross section.

[0036] The fins 4011A, 4011B in each reaction chamber 4001, 4101, 4201 include a first set of fins 4011A and a second set of fins 4011B, and a photocatalyst 1004 is disposed on each fin. The first set of fins 4011A and the second set of fins 4011B are disposed such that light from a corresponding light emitting diode 4009 illuminates at least a portion of the length of the face 4013 of each fin 4011A, 4011B along the entire height of the face 4013. In other words, within the reaction chamber 4001, 4101, 4201, each light emitting diode 4009 illuminates the entire height of at least one face 4013 of each fin 4011A, 4011B without being shadowed by adjacent fins. However, multiple light emitting diodes 4009 (e.g., multiple light emitting diodes distributed longitudinally) may be necessary to illuminate the entire length of the fins 4011A, 4011B. Within each reaction chamber 4001, 4101, 4201, the light emitting diodes 4009 are distributed to each illuminate different, but potentially overlapping, portions of the length of at least one face 4013 of each fin 4011A, 4011B.

[0037] 4, within each reaction chamber 4001, 4101, 4201, each of the first set of fins 4011A is positioned such that a line extending from the base end 4015 of the fin 4011A through the tip 4016 of the fin (e.g., a line extending along the height of the fin and similar to a chord line) is directed to a first convergence point or intersection point F1. Then, each of the second set of fins 4011B is positioned such that a line extending from the base end 4015 of the fin 4011B through the tip 4016 of the fin 4011B is directed to a second convergence point F2. The first convergence point F1 is different from the second convergence point F2, and both the first convergence point F1 and the second convergence point F2 are offset relative to the position of the light emitting diode 4009.

[0038] A first set of fins 4011A extends inwardly from a first inner surface 4018A of each reaction chamber 4001, 4101, 4201, and a second set of fins 4011B extends inwardly from a second inner surface 4018B of each reaction chamber 4001, 4101, 4201, with the first inner surface 4018A and the second inner surface 4018B generally facing the light emitting diodes 4009. The first inner surface 4018A and the second inner surface 4018B are symmetrically arranged about the optical axis of the light emitting diodes such that the first set of fins 4011A are positioned to be illuminated by a first half of each light emitting diode 4009, and the second set of fins 4011B are positioned to be illuminated by a second half of each light emitting diode 4009. In the example shown in FIG. 4, a photocatalyst 4004 is also disposed on both the first inner surface 4018A and the second inner surface 4018B of each reaction chamber 4001, 4101, 4201.

[0039] Within each reaction chamber 4001, 4101, 4201, the first inner surface 4018A and the second inner surface 4018B have distinct arcuate profiles (i.e., their cross sections are curved segments with different focal points), with the first inner surface 4018A having a profile that is a mirror image of the second inner surface 4018B profile. In other words, the first inner surface 4018A and the second inner surface 4018B are reflections of each other, and thus both have mirror / reflection symmetry. The first inner surface 4018A and the second inner surface 4018B may each have either a circular arc-shaped profile or a parabolic-shaped profile.

[0040] As can be seen from FIG. 4, the reaction chambers 4001, 4101, 4201 are distributed around a common axis. In particular, the three reaction chambers 4001, 4101, 4201 are arranged such that the arrangement has three-fold rotational symmetry around the common axis. The three reaction chambers 4001, 4101, 4201 are also arranged in succession such that the substrates 4003 of the reaction chambers 4001, 4101, 4201 define a volume of space within which the LED PCBs 4012, 4112, 4212 are located. The partition wall 4005 comprises a single layer of transparent material arranged between the LED PCBs 4012, 4112, 4212 and separating them from the photocatalyst 4004. This layer of transparent material is impermeable to air and transparent to the radiation emitted by the light-emitting diodes 4009. 4, the single layer of transparent material 4005 has the form of a manifold tube and is concentrically disposed around the LED PCBs 4012, 4112, 4212. The manifold transparent material 4005 provides a conduit within which the LED PCBs 4012, 4112, 4212 are located and is disposed to allow airflow therethrough for cooling the light emitting diodes 4009.

[0041] The photocatalytic reactor 4000 shown above comprises three reaction chambers. Those skilled in the art will appreciate that the photocatalytic reactor 4000 may comprise any number of reaction chambers. The photocatalytic reactor 4000 shown above is elongated. Those skilled in the art will appreciate that this does not necessarily have to be the case.

[0042] 1A, 1B, 2A, 2B, 3A, 3B, and 4 all include fins arranged to maximize the illuminated surface area, thereby maximizing the efficiency of the photocatalytic reactor. In doing so, this arrangement also minimizes the number of light emitting diodes required to illuminate the fins, since the lack of shadows optimizes the surface area illuminated by each light emitting diode.

[0043] The photocatalytic reactors of Figures 1A, 1B, 2A, 2B, 3A, 3B and 4 all include fins that provide a relatively large surface area for the photocatalyst. An example of an alternative improved photocatalytic reactor without such fins is described with reference to Figures 5A and 5B. The photocatalytic reactor is generally indicated by the reference number 5000. The photocatalytic reactor 5000 includes two reaction chambers 5001, 5101 each arranged to receive an airflow containing one or more airborne pollutants, and a photocatalyst 5004 for photocatalytically decomposing the one or more pollutants, the photocatalyst 5004 being disposed on a substrate 5003, 5103 provided by each of the reaction chambers 5001, 5101. In the example shown in Figures 5A and 5B, the photocatalytic reactor 5000 further includes a double-sided light-emitting diode printed circuit board ("LED PCB") 5012. Thus, the LED PCB 5012 comprises a printed circuit board 5008 having a plurality of first light emitting diodes 5009 mounted to a first side 5006 of the printed circuit board 5008 and a plurality of second light emitting diodes 5010 mounted to a second side 5007 of the printed circuit board 5008. Thus, the LED PCB 5012 comprises either a double sided circuit board or a multi-layer circuit board.

[0044] Next, the photocatalytic reactor 5000 is arranged such that the substrate 5003 of the first reaction chamber 5001 is illuminated by a first light emitting diode 5009 mounted on a first side 5006 of the printed circuit board 5008, while the substrate 5103 of the second reaction chamber 5101 is illuminated by a second light emitting diode 5010 mounted on a second side 5007 of the printed circuit board 5008. In particular, the substrate 5003 of the first reaction chamber 5001 is arranged to intercept the LED PCB 5012, and light emitted from the first light emitting diode 5009 impinges on the substrate 5003, while the substrate 5103 of the second reaction chamber 5101 is arranged to intercept the LED PCB 5012, and light emitted from the second light emitting diode 5010 impinges on the substrate 5103.

[0045] 5A and 5B, the photocatalytic reactor 5000 is elongated and the first and second reaction chambers 5001, 5101 are distributed around the axis of the photocatalytic reactor 5000, with the arrangement having two-fold rotational symmetry around the axis. Also, the reaction chambers 5001, 5101 are arranged in series such that the substrates 5003, 5103 of the reaction chambers 5001, 5101 define spatial volumes within which the LED PCB 5012 is located. In particular, the LED PCB 5012 is elongated and axially aligned within the elongated photocatalytic reactor 5000, extending along the length of the reaction chambers 5001, 5101. The first light emitting diodes 5009 of the LED PCB 5012 are spaced apart and aligned longitudinally along a first side 5006 of the length of the LED PCB 5012, and the second light emitting diodes 5010 are spaced apart and aligned longitudinally along a second side 5007 of the length of the LED PCB 5012, thereby providing a light source along the entire length of the photocatalytic reactor 5000.

[0046] Then, the reaction chambers 5001, 5101 each comprise a reaction chamber inlet (not shown) at a first end of the reaction chamber 5001, 5101 and a reaction chamber outlet (not shown) at a second end of the reaction chamber 5001, 5101, and the air flow passing between the reaction chamber inlet and the reaction chamber outlet contacts the photocatalyst 5004 disposed on the respective substrate 5003, 5103. A partition / barrier 5005 then separates the reaction chambers 5001, 5101 from the LED PCB 5012, at least a portion of which is transparent to the radiation emitted by the light emitting diodes 5009, 5010, and the photocatalyst 5004 can be illuminated by the light emitting diodes 5009, 5010. In the example shown in Figures 5A and 5B, the partition 5005 is tubular and comprises a single layer of transparent material disposed concentrically around the LED PCB 5012. This tube of transparent material provides a conduit within which the LED PCB 5012 is located and is arranged such that air can flow through the conduit to cool the light emitting diodes 5009,5010.

[0047] In the example shown in Figures 5A and 5B, each of the reaction chambers 5001, 5101 comprises a first inner surface 5018A, 5118A and a second inner surface 5018B, 5118B, and the photocatalyst 5004 is disposed on both the first inner surface 5018A, 5118A and the second inner surface 5018B, 5118B. The first inner surface 5018A, 5118A and the second inner surface 5018B, 5118B have distinct parabolic-shaped contours, meaning that their cross sections are curved segments with different foci, with the contour of the first inner surface 5018A, 5118A being a mirror image of the contour of the second inner surface 5018B, 5118B. The photocatalytic reactor 5000 is then arranged such that the light emitting diodes 5009, 5010 on the corresponding faces 5006, 5007 of the LED PCB 5012 illuminate both the first inner surface 5018A, 5118A and the second inner surface 5018B, 5118B. In particular, the first inner surface 5018A, 5118A and the second inner surface 5018B, 5118B of each reaction chamber 5001, 5101 are arranged symmetrically around the optical axis O of the corresponding light emitting diode 5009, 5010, such that the first inner surface 5018A, 5118A is illuminated by the first half of the light emitting diode 5009, 5010, and the second inner surface 5018B, 5118B is illuminated by the second half of the light emitting diode 5009, 5010. The first inner surface 5018A, 5118A and the second inner surface 5018B, 5118B of each reaction chamber 5001, 5101 are also contiguous.

[0048] 5A and 5B, the total surface area of ​​the photocatalyst 5004 is reduced compared to the arrangements shown in FIGS. 1A, 1B, 2A, 2B, 3A, 3B and 4 due to the lack of surface features (e.g., fins or other protrusions), while the substrate 5003, 5103 carrying the photocatalyst 5004 is positioned as close as possible to the light source 5009, 5010 to maximize the irradiance of the photocatalyst 5004. However, a gap is required between the partition 5005 and the substrate 5003, 5103 to allow air to pass through the photocatalytic reactor 5000, and optimizing the separation distance between the partition 5005 and the substrate 5003, 5103 provides a thinner layer of air that optimizes the cleaning and mixing of the air in the reaction chamber 5001, 5101. 5A and 5B, the partition 5005 has a diameter D of about 35 mm, and the separation distance S between the outer surface of the partition 5005 and the substrates 5003, 5013 is about 3 mm at most. However, the separation distance S may be up to 10 mm or less, preferably 7 mm or less, and more preferably 1 mm to 7 mm.

[0049] It is also desirable to generate uniform irradiance across the catalyst surface so that the air in the photocatalytic reactor is treated evenly. However, LEDs do not emit light with cylindrical symmetry, but rather with a Lambertian distribution. Conventional photocatalytic reactors utilizing LED light sources typically have a cylindrical substrate and therefore require a lens disposed between the LED and the substrate to distribute the light emitted by the LED uniformly across the substrate's surface, which adds cost and bulk to the LED package. To overcome this problem, applicants have discovered that a more uniform irradiance of the substrate can be obtained by providing a substrate whose cross-sectional shape is defined by two separate parabolic arcs. In particular, the use of such a parabolic contour facilitates shaping of the catalyst-bearing inner surface to take into account the local irradiance provided by the LED light source. Such an inner surface with a parabolic contour allows for a reduction in the difference in irradiance at the inner surface as a function of angle α, providing greater irradiance uniformity at the photocatalytic inner surface. In this regard, the cross-sectional profile of each of the first inner surface 5018A, 5118A and the second inner surface 5018B, 5118B may be defined by a Bezier curve, in particular a quadratic Bezier curve. Thus, the cross-sectional profile of each of the first inner surface 5018A, 5118A and the second inner surface 5018B, 5118B may be defined by a three-point Bezier curve defined by the following equation:

[0050]

number

[0051] where P0 is the start point of the curve, P2 is the end point of the curve, and P1 is the control point of the curve. Using a Bézier curve, it is possible to provide a more uniform irradiance at the photocatalytic surface as a function of the angle α.

[0052] As previously mentioned, those skilled in the art will appreciate that the photocatalytic reactors described above may be used in place of conventional photocatalytic reactors in air treatment systems.

[0053] Where the foregoing description refers to integers or elements having known, obvious or foreseeable equivalents, such equivalents are incorporated herein as if set forth separately. Reference should be made to the claims to determine the true scope of the invention, which should be interpreted to encompass such equivalents. The reader will also understand that any components or features of the invention described as preferred, advantageous, convenient, etc. are optional and do not limit the scope of the independent claims. Furthermore, it should be understood that any such integers or features may be beneficial in some embodiments of the invention, but may not be desirable and therefore may not be present in other embodiments.

Claims

1. 1. A photocatalytic reactor comprising: a reaction chamber disposed to receive an airflow containing one or more airborne contaminants; the reaction chamber comprises a first inner surface, a second inner surface, a photocatalyst disposed on both the first inner surface and the second inner surface for photocatalytic decomposition of one or more of the pollutants, a light source having a longitudinally shaped substrate extending along the path of the air flow and including a plurality of light emitting diodes disposed on a surface along a path of the air flow facing at least a portion of the photocatalyst disposed on the first inner surface and the second inner surface, and a transmissive material disposed between the light source and the first and second inner surfaces, an air flow is passed between the transmissive material and the light source, the first inner surface and the second inner surface have distinct parabolic shaped contours, and the contour of the first inner surface is a mirror image of the contour of the second inner surface; Photocatalytic reactor.

2. 10. The photocatalytic reactor of claim 1, wherein said first inner surface and said second inner surface are contiguous.

3. 3. The photocatalytic reactor of claim 1 or 2, wherein the light source comprises a light emitting diode, and the first inner surface and the second inner surface are symmetrically disposed around the light emitting diode.

4. 4. The photocatalytic reactor of claim 1, wherein the light source comprises a plurality of light emitting diodes arranged so that each of the light emitting diodes illuminates at least a portion of both the first inner surface and the second inner surface, the first inner surface and the second inner surface being arranged symmetrically around each of the plurality of light emitting diodes.

5. 5. The photocatalytic reactor of claim 4, wherein said plurality of light emitting diodes are distributed such that each illuminates a different portion of the length of both said first inner surface and said second inner surface.

6. 6. The photocatalytic reactor of claim 4 or 5, wherein the reaction chamber is elongated and the plurality of light emitting diodes are aligned in the longitudinal direction.

7. 7. The photocatalytic reactor of claim 1, wherein the reaction chamber comprises an air inlet and an air outlet, and is positioned such that air flow passing between the air inlet and the air outlet contacts the photocatalyst.

8. 8. The photocatalytic reactor of claim 1, wherein the reaction chamber comprises at least one layer of the transparent material separating the photocatalyst from the light source.

9. 9. The photocatalytic reactor of claim 8, wherein the first and second inner surfaces are separated from an outermost surface of the at least one layer of transparent material by a distance of at most 10 mm or less.

10. The photocatalytic reactor of claim 1 , wherein the photocatalytic reactor comprises a plurality of reaction chambers.

11. 11. The photocatalytic reactor of claim 10, wherein the plurality of reaction chambers are distributed about a common axis, each reaction chamber is positioned such that the first inner surface and the second inner surface face inwardly, and the light source is centrally positioned relative to the first inner surface and the second inner surface.

12. 12. The photocatalytic reactor of claim 10 or 11, wherein a plurality of said reactors are arranged in series.

13. The photocatalytic reactor of claim 11 or claim 12 when claim 11 is recited, wherein the reaction chambers are arranged such that the arrangement has rotational symmetry about the common axis.

14. An air treatment device comprising a photocatalytic reactor according to any one of claims 1 to 13.

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