Air purifier for refrigerators

Abstract

The present invention relates to an air purification device (10; 10') for use in a refrigerator, which includes a photocatalyst (22; 22') in the air flow path through the air purification device. In the photocatalyst (22; 22'), a layer based on tungsten oxide (WO3) is applied to a ceramic foam carrier. This layer may also include tin oxide and silver oxide, or even platinum. The oxide layer can be obtained by immersion without the application of a primer. A method for extending the shelf life of fruits, particularly strawberries, salads, and vegetables, in a refrigerator, and the associated refrigerator are also described. The air purifier is characterized by its energy saving due to the use of white light to activate the photocatalyst (22; 22') and its low toxic effects.

Description

[Technical Field]

[0001] The present invention relates to an air purification device comprising a housing with an inlet for a fluid, particularly air, and an outlet for the fluid, and a photocatalytic chamber through which the fluid can pass and which communicates with the inlet and the outlet. The photocatalytic chamber comprises a photocatalyst and a light source for activating the photocatalyst. [Background technology]

[0002] Several air purifiers are known for maintaining clean indoor environments in homes, workplaces, industrial spaces, and laboratories. These purifiers utilize the purifying capabilities of plants or filters, typically titanium dioxide-based photocatalytic filters activated by ultraviolet (UV) light. These materials and UV rays pose numerous problems, including toxicity, such as ozone generation, and high energy consumption. In delicate environments like refrigerators where food is stored, these purifiers are not ideal; many fail to adequately remove odors and microorganisms, for example, to extend the shelf life of fruits and vegetables. Summary of the Invention [Problem to be solved by the invention]

[0003] The object of the present invention is to propose an air purifying device for use in refrigerators that overcomes the aforementioned drawbacks and is characterized by low energy consumption, reduced ozone emissions, and materials that are harmless to humans. Another object of the present invention is to propose a related air purifying device that reduces the total amount of bacteria while used in the refrigerator, so as to significantly extend the shelf life of vegetables, salads, fruits, and in particular strawberries. [Means for solving the problem]

[0004] In a first aspect of the invention, this object is achieved by a purification device as described at the outset, in which the photocatalyst consists of a ceramic foam support coated with a layer comprising tungsten trioxide and the light source is a visible light source.

[0005] Preferably, the fluid pathway is configured such that the photocatalytic filter is positioned perpendicular to the pathway and thus perpendicular to the fluid flow, which minimizes photocatalytic load loss.

[0006] In a preferred embodiment of the present invention, the visible light source for activating the photocatalyst comprises a plurality of LEDs, one at each vertex of a decagon, and two further LEDs arranged to form a triangle with the two LEDs at both ends of one side of the decagon, two of the constituent sides of the triangle being separated by another side of the decagon.

[0007] In another advantageous embodiment of the invention, the lower part of the housing has a ring-shaped opening at its bottom, surrounding a basket-like structure, the basket-like structure has an inlet on its side, and its bottom corresponds to the bottom of the lower part of the housing, the inlet in the basket-like structure communicates with the ring-shaped opening and ultimately with the outside.

[0008] The porous nature of foam ceramic substrates allows the use of a primer to be omitted when coating with a photocatalytically active material, thereby reducing processing time and costs. When applying a coating layer based on WO3 (e.g., CLC-W from Inpigest, Bodio-Romanago, Italy), the preferred application bath is aqueous and preferably further contains a fixing agent and / or an accelerator.

[0009] In a preferred embodiment of the invention, the layer further comprises tin oxide and silver oxide, which, in combination with tungsten trioxide, provide oxides useful for reducing total bacterial count (TBC). A particularly preferred composition of the layer is a weight ratio of tungsten trioxide, tin oxide, and silver oxide of 0.9-1.1:1.3-1.7:0.05-0.15, especially about 1:1.5:0.1.

[0010] The purification effect can be further increased by adding platinum, advantageously in a weight ratio of platinum to tungsten trioxide of 0.9-1.1:0.9-1.1, in particular about 1:1.

[0011] Ceramic foam carriers that are particularly suitable for coating with oxide-based layers without the use of a primer consist of aluminum oxide Al2O3 and silicon oxide SiO2. Surprisingly, ceramic filters for filtering molten aluminum and its molten alloys are particularly suitable for the purposes of the present invention. Advantageously, the pores of ceramic foam carriers have a density of 8 to 10 ppi (pores per inch), which has proven particularly suitable for ensuring a sufficient flow rate of the fluid to be purified while simultaneously cleaning the fluid from a chemical and microbiological standpoint.

[0012] In a highly preferred variant of the invention, the tungsten oxide based layer is in direct contact with the ceramic foam support without an intermediate layer of primer: the coating adheres directly to the ceramic foam.

[0013] Photocatalysis is a surface phenomenon. Therefore, applying the coating to a support with a large available surface area, such as a ceramic open-foam structure, enhances the photocatalytic reaction. To ensure the effectiveness of this system, pressure drop must be minimized even in photocatalytically active materials. Using ceramic foam with a pore density of 8-10 ppi (pore density) is also effective in keeping pressure drop low.

[0014] During filter manufacturing, the substrate onto which the WO3 or other oxides or metals are applied is prepared to receive the material. Pretreatment involves cleaning the substrate, but applying a primer to promote adhesion of the photocatalytic material is not necessary. When using ceramic foam, the "primer" step can be omitted because the porous nature of the substrate allows the coating to adhere well to the substrate.

[0015] A further aspect of the present invention relates to a food refrigerator comprising an air purification device according to the present invention. Such a refrigerator has an internal environment that is odorless and resistant to chemical and microbiological contamination during use of the air purification device, thereby significantly extending the shelf life of fruits, vegetables and salads. The air purification device can be simply installed inside the refrigerator or fixed to the interior wall of the refrigerator by associated fixing means.

[0016] A further aspect of the present invention is a method for keeping a refrigerator clean and odor-free and for extending the shelf life of fruits and vegetables, comprising: (a) preparing a refrigerator according to the present invention; (ii) activating the photocatalyst by irradiating it with a light source; (iii) circulating the air within the refrigerator through an air purification device; Includes:

[0017] The purification device according to the present invention further comprises a fan or pump system to generate a fluid flow from the inlet through the photocatalytic system towards the outlet.

[0018] A fourth aspect of the present invention relates to a photocatalyst for use in air purification devices, in particular refrigerators, comprising a ceramic foam support based on Al2O3 and SiO2, having a pore density of 8-10 ppi, coated with a layer comprising tungsten trioxide, tin oxide, silver oxide, and advantageously platinum, in weight ratios of tungsten trioxide, tin oxide, and silver oxide of 0.9-1.1:1.3-1.7:0.05-0.15:0.9-1.1, preferably about 1:1.5:0.1:1.

[0019] Such photocatalysts are particularly suitable for improving the shelf life of fruits, vegetables, and salads in refrigerators, as exemplified below, and are therefore particularly suitable for use in the refrigerator air purifier of the present invention. This effect is particularly pronounced when preserving strawberries, which normally tend to spoil after 2-3 days.

[0020] A further aspect of the present invention relates to a method for producing the above-mentioned photocatalyst, said method comprising the steps of: (α) preparing a ceramic foam carrier based on Al2O3 and SiO2, having a pore density of 8-10 ppi, and preferably cleaned with compressed air; (β) immersing the ceramic foam carrier in an aqueous bath containing tungsten trioxide, tin oxide, and silver oxide in a weight ratio of 0.9-1.1:1.3-1.7:0.05-0.15:0.9-1.1, particularly about 1:1.5:0.1:1, and more preferably platinum; (γ) a step of drying the thus coated support, preferably with compressed air, or a step of heating the support at 70 to 80°C; Includes:

[0021] In a highly preferred variant of the manufacturing process, no primer is applied between steps (α) and (β). This is due to the special combination of substrate and coating layer. The evaporation time for the water is usually a few hours, for example 3 hours.

[0022] As an alternative to step (β), it is possible to carry out a spray treatment using a spray gun with a nozzle diameter of, for example, 1.5 to 2 mm to form a uniform film on the surface of the support.

[0023] The photocatalytic filter of the present invention is recyclable. Fouling on the filter may result from low photocatalytic efficiency (low surface area, crystalline phase) after long-term use, or from uneven and / or insufficient and / or short-term irradiation, resulting in the deposition of organic substances not decomposed by the photocatalyst. The surface area and porosity of the photocatalyst are physical properties that affect the quality and behavior of porous materials. Materials of the same weight and volume can exhibit differences in surface activity and adsorption capacity depending on their specific surface area. Porosity is measured by heating the filter under vacuum to remove impurities, followed by analysis of the volume of gas adsorbed under a specific pressure, e.g., at 77 K in liquid nitrogen. The Brunauer-Emmett-Teller (BET) theory is the most widely used model for determining surface area. To measure pore size by gas adsorption, isotherms are recorded over a range from low pressure to saturation pressure. The pressure range is determined by the size range of the pores to be measured, with a pressure range of approximately 0.00001 Torr to 0.1 Torr for microporous materials and a pressure range of 0.9 to 0.44 Torr (1 Torr / g) for mesoporous materials.

[0024] X-ray fluorescence (XRF) is an analytical technique applicable to most inorganic materials that can identify contaminants in the filters and determine the regeneration efficiency and residual material on the filters. Different regeneration methods were tested using this technique.

[0025] While simple heating to 250 °C was insufficient to regenerate the filters, and hydrogen peroxide washing was also ineffective, a combination of sodium hypochlorite washing, followed by hydrogen peroxide washing, and a final heat treatment showed satisfactory results. Even when filters were immersed in 30% (w / w) hydrogen peroxide for 24 hours and then muffle-heated in air at 250 °C for 5 hours, the presence of organic matter was consistently observed. Treatment with hypochlorous acid, on the other hand, proved effective. For example, materials could be immersed in a hypochlorous acid solution for 2 hours, then removed and immersed in a 3% (w / w) hydrogen peroxide solution, followed by heat treatment. The hydrogen peroxide wash serves the dual purpose of removing any residual hypochlorous acid (and its unpleasant odor) and further oxidizing any residues that survived the hypochlorous acid treatment. The treated materials were then heat-treated, ultimately resulting in a white color. The tungsten (W) content in the samples was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES), which showed that the tungsten oxide could withstand the regeneration treatment.

[0026] Features and advantages described with respect to one aspect of the invention may be applied mutatis mutandis to other aspects of the invention.

[0027] The industrial applicability of this air purification device is clear, as it can extend the shelf life of food products and can be achieved in a system with low energy consumption and no toxicity issues.

[0028] Objects and advantages will be further emphasized in the disclosure of preferred examples of embodiments of the invention, given by way of non-limiting example only.

[0029] Variations and further features of the invention are set forth in the dependent claims. A description of preferred embodiments of the invention is given by way of example and without limitation with reference to the accompanying drawings. Unless specifically stated otherwise, the number, shape, dimensions and materials of the system and its individual components may be modified and the application of equivalent elements does not depart from the spirit of the invention. [Brief explanation of the drawings]

[0030] [Figure 1] 1 shows a perspective view of an embodiment of an air purification device of the present invention. [Figure 2] 2 shows a longitudinal cross-sectional view of the air purifying device shown in FIG. [Figure 3] 2 shows a perspective view of a photocatalytic filter used in the air purification device of FIG. 1. [Figure 4] 4 shows a detailed cross-sectional view of the photocatalytic filter of FIG. 3. [Figure 5] 4 shows the results of light intensity or heat distribution diagrams measured according to the number of LEDs (light emitting diodes) in the photocatalytic filter of FIG. 3. [Figure 6] The graph shows the amount of formaldehyde reduction in an air purifier equipped with a photocatalytic filter based on titanium dioxide irradiated with ultraviolet light. [Figure 7] The graph shows the reduction in formaldehyde in a purifier equipped with a tungsten trioxide-based photocatalytic filter exposed to visible light. [Figure 8] The graph shows the reduction in total bacterial count (TBC) in a purifier equipped with a photocatalytic filter based on titanium dioxide exposed to ultraviolet light. [Figure 9] The graph shows the reduction in total bacteria count in an air purifier equipped with a tungsten trioxide-based photocatalytic filter exposed to visible light. [Figure 10] FIG. 2 shows a perspective view of a second embodiment of the air purification device of the present invention. [Figure 11] 11 shows a longitudinal cross-sectional view of the air purifying device of FIG. [Figure 12] 11 shows a perspective view of the air purifying device of FIG. 10 as seen from below. [Figure 13] The measurement results of the light intensity or heat distribution diagram in the photocatalytic filter of the air purifier of FIG. 10 are shown according to the number of applied LEDs (light emitting diodes). DETAILED DESCRIPTION OF THE INVENTION

[0031] 1 is a perspective view of an example embodiment of an air purifying device 10 according to the present invention, which comprises a housing having an upper portion 12 and a lower portion 14 inserted one into the other. Also shown is an inlet 16 for the outlet of air. Reference numeral 28 denotes a battery compartment.

[0032] The longitudinal cross-section of the air purifier shown in FIG. 1 more clearly illustrates the main components of the system, as shown in FIG. 2. Air enters the housing through inlet 18, as indicated by arrow F1, and passes through photocatalytic filter 22 in photocatalytic chamber 20. In this photocatalytic chamber 20, LED light 21 illuminates the upper surface of photocatalytic filter 22 with vertical light. After passing through filter 22 and photocatalytic chamber 20, the air is expelled from air purifier 10 through outlet 16, as indicated by arrow F2, with the assistance of fan 23. Electronic circuitry 24 controls the LED and fan 23 and generates airflow that travels vertically from inlet 18 to filter 22. A battery located in battery compartment 28 powers electronic circuitry 24. Element 26 serves as an interface with the LED ring button.

[0033] FIG. 3 is a perspective view of the photocatalytic filter 22 used in the air purifier of FIG. 1, and FIG. 4 is a cross-sectional view of the photocatalytic filter of FIG. 3 in detail.

[0034] Ceramic foam filters (e.g., VUKOPOR® A, manufactured by Lanik, Boskovice, Czech Republic) were originally designed for primary and secondary processing of aluminum and non-ferrous alloys in foundries, as well as for filtration of molten metals. However, they have surprisingly proven to be highly suitable for use in completely different applications, such as the present invention. These filters are also advantageous in that they can be coated with tungsten oxide (WO3) without the need for a primer. A typical structural feature of ceramic foam filters is a labyrinthine, three-dimensional open pore network within the ceramic body. This structure and the filtering ceramic allow optimal coverage by the tungsten oxide layer and uniform air flow over a large surface area. These filters have a uniform ceramic structure with minimal restriction points within the effective surface and are resistant to chemicals and heat. Their chemical composition also provides effective adhesion to the substrate to which they are applied.

[0035] All types of filters, in various sizes and shapes, can be equipped with sealing or inflatable gaskets to secure them in place and prevent bypass flow. It is advisable to preheat the filter (350-400°C) before first use, as this maximizes speed and filtration capacity. The ceramic material advantageously contains Al2O3 and SiO2. The porosity is 8-10 ppi (pores per inch).

[0036] Preferably, there are no closed holes, cracks, or breaks in the active area of ​​the filter.The side length (A) and height (B) can be varied as needed.

[0037] Figure 5 shows the results of light intensity measurements, i.e., heat maps, on the photocatalytic filter of Figure 3, depending on the number of light sources (LEDs). Brighter images indicate higher light intensity. Selected light configurations (illumination configurations) are shown on the right, and images of the light intensity (heat) generated by these configurations are shown on the left as top views. The central diagram shows the corresponding heat intensity scale (heat is higher with greater transparency).

[0038] Each photocatalyst requires a specific wavelength for activation. WO3 requires and tolerates wavelengths in the visible range, preferably around 450 nm. For example, 300 lux is required to activate the filter surface. The lux reaching the filter can be adjusted by the LED intensity (measured in lumens), their distance from the photocatalyst surface, and the number of LEDs used. Depending on the number of LEDs and the lumens of each LED selected, the power required to operate the LEDs and therefore the associated power consumption also varies. In the purification device of the present invention, the illumination of the filter is optimized with the aim of minimizing the associated energy consumption. In this sense, by increasing the number of LEDs, reducing zones below 300 lux, and reducing zones significantly above 300 lux, the most uniform filter illumination possible can be achieved. As can be seen from the analysis shown in Figure 5, increasing the number of LEDs in this application limits the areas with excess lux. This also reduces the amount of energy absorbed. In this specific case, the total power consumption was reduced from 110 mW to 100 mW.

[0039] Switching from UV-A LEDs to activate titanium dioxide-based coatings offers energy benefits. Regarding the absorbed power, for the same number of LEDs and their arrangement, in a specific example, with UV LEDs and TiO2 photocatalyst, the firmware limited the LEDs' absorbed power to 3.75% of their capacity, resulting in a total absorbed power of approximately 50 mW per LED, for a total of 200 mW. For white LEDs and WO3 photocatalyst, the maximum power absorbed by each white LED was approximately 43 mW. By default, this value was set to 50%, resulting in a total power of approximately 21.5 mW. Under the same conditions, i.e., when both UV and white LEDs were used at 100% of their available power, the current consumption of the white LEDs was 98% lower than that of the UV LEDs, resulting in a significant energy savings. An additional advantage is that the white LEDs can all be connected in series, halving the current consumption compared to the UV LEDs, which would otherwise have to be split into separate branches. Finally, the lifespan of UV LEDs is 3,000-4,000 hours, while that of white LEDs is 40,000-60,000 hours, which means less waste and less environmental pollution, and lower costs for users.

[0040] Laboratory tests using prototypes investigated the difference in the practical effectiveness of the new WO3 coating compared to TiO2 coatings, which, unlike tungsten oxide-based filters, do not achieve zero TBC after 8 hours.

[0041] Figure 6 shows a graph of formaldehyde reduction in a purification system using a titanium dioxide-based photocatalytic filter exposed to UV light. Compared to natural attenuation (top curve), the titanium dioxide-based filter reduces formaldehyde concentrations more quickly, with a fairly linear trend. Sampling was performed at the time of initial contamination, and after 60, 150, and 300 minutes of photocatalytic treatment; other points were interpolated.

[0042] In contrast, Figure 7 shows a graph of formaldehyde reduction in a purifier using a tungsten oxide-based photocatalytic filter exposed to visible light. The tungsten trioxide filter reduces formaldehyde very quickly in the first two hours, with formaldehyde nearly eliminated after two hours.

[0043] In both graphs of Figures 8 and 9, the left side shows the TBC 0 and 10 minutes after the purifier is turned off, and the right side shows the TBC 1 hour, 2 hours, ... 8 hours after the purifier is turned on.

[0044] The results show that the visible light system is faster and, most importantly, more durable.

[0045] In 2020, IARC (International Agency for Research on Cancer) classified TiO2 (titanium dioxide) as a "possibly carcinogenic to humans (Group 2B)," and in 2021, after many years of use in the food industry, its safety as a food additive was denied by EFSA (European Food Safety Authority). Meanwhile, tungsten trioxide (WO3) is identified by CAS number 1314-35-8 and EC number 215-231-4, the full text of which is available on the European Chemicals Agency (ECHA) website (https: / / echa.europa.eu / registration-dossier / - / registered-dossier / 15315 / 2 / 3). WO3 is classified as a non-PBT (persistent, bioaccumulative, and toxic) substance, meaning it does not fall under either the "vPvB" (very persistent and very bioaccumulative) category. EFSA has also issued a positive opinion on the use of WO3 (CAS number 39318-18-8) as an additive in materials that come into contact with food.

[0046] Figure 8 is a graph showing the reduction in total bacterial count in a purification device using a photocatalytic filter based on titanium oxide irradiated with ultraviolet light, and Figure 9 is a graph showing the reduction in total bacterial count in a purification device using a photocatalytic filter based on tungsten oxide irradiated with visible light.

[0047] Laboratory tests have shown that the purifying device of this invention can remove more than 80% of odors and VOCs (volatile organic compounds) in the refrigerator through photocatalytic technology, preventing cross-contamination and changes in organic properties between foods in the refrigerator.

[0048] In collaboration with the National Inter-university Consortium for Materials Science and Technology (INSTM), the inventors conducted tests using artificial contamination with two odorous compounds. These tests confirmed that the air purifier of the present invention removed 80% of the selected compounds within 24 hours and 50% within 5 hours. The odorous compounds used were hexanal and pentyl butyrate, molecules that, when present in high concentrations, produce an odor similar to oxidized (spoiled) odor. Furthermore, ArcoSolution, a spinoff company of the University of Trieste, conducted tests on actual contamination inside a refrigerator and confirmed that the air purifier of the present invention significantly reduced VOC (volatile organic compound) concentrations, even immediately after the refrigerator was filled with fresh food, achieving an 80% reduction after just 5 hours. The air purifier of this invention uses photocatalytic technology to reduce bacterial and mold loads on food in the refrigerator by up to 10 times, extending the shelf life of fruits, salads, vegetables, etc. by up to 7 days, delaying the occurrence of wilting, softening, staining, and decay.

[0049] The tests showed that with WO3 the reduction in total bacteria count was faster and, above all, longer lasting. It should be noted that already after the fourth hour of operation the total bacteria count (TBC) fluctuated between 0 and 2, which has almost the same microbiological and statistical meaning.

[0050] Thus, the superiority of tungsten oxide (WO3)-based filters over titanium oxide (TiO2)-based filters was demonstrated in two tests: a microbiological test and a chemical test.

[0051] Microbiological testing is approximately 8m 3 , chemical testing is about 4m 3 The study was conducted in a 2015-nCoV environment. Contaminant sampling was performed using a device called the "Uniphos Precision Air Sampling Pump," which consists of a high-precision manual pump and a colorimetric vial inserted into it, which changes color in proportion to the amount of target substance contained in the aspirated air (method: EN ISO 17621:2015 standard). For TiO2, the reduction rate was 67.6% after 1 hour and 86.5% after 8 hours. For WO3, the reduction rate was 81.5% after 1 hour and 99.9% after 8 hours.

[0052] The best-known photocatalyst is titanium dioxide (TiO2), the most widely used material to date. TiO2 requires ultraviolet light to activate. In the purification device of the present invention, the photocatalyst is based on tungsten trioxide (WO3), which offers several advantages. Because ultraviolet light is not used, no ozone is generated; visible light is not harmful to the eyes, avoiding stricter usage regulations; the low cost and low energy consumption of visible light LEDs make it a less expensive technology; and WO3 has a high air purification effect.

[0053] Tests have shown that there is no ozone release in the short term (5 hours of continuous operation). After 24 hours of operation, a slight presence of ozone was observed, probably less than 1 cubic meter (0.57 m 3 The reported values ​​are in any case negligible, and are below the WHO (World Health Organization) threshold of 0.2 mg / m³. 3The values ​​recorded were clearly lower than those of the previous study, more than 100 times lower. The tests involved switching on the purifier according to the invention for 5 and 24 hours in a closed hood measuring 1.70 m x 45 cm x 75 cm. The analysis was carried out using an impinger solution characterized by iodide ions, which capture ozone and form iodide ions, as reported in a scientific paper (Byers, D.H., Satzman, B.E. "Determination of Ozone in Air by Neutral and Alkaline Iodide Procedures", Journal of the American Industrial Hygiene Association, 1958, Vol. 19 (No. 3), 251-257). In the short term, there was no release of ozone, and after 24 hours of operation, a slight presence of ozone was observed, probably less than 1 cubic meter (0.57 m). 3 This is likely due to the heat released from the equipment when it is operated continuously for 24 hours in a sealed hood.

[0054] To understand user habits regarding the use of domestic refrigerators, energy consumption was monitored. Results showed that the door is opened 20 to 50 times per day (32 times on average). This contributes to 7% of annual energy consumption (maximum 23%), averaging approximately 50 to 120 kWh. This consumption is equivalent to 20 dishwasher cycles or 50 washing machine cycles. Refrigerator energy consumption is directly proportional to the number of cooling cycles performed by the compressor. Each time the refrigerator is opened, unpurified air enters, requiring the purifier to operate more frequently. Therefore, energy conservation in purifiers is desirable.

[0055] In laboratory tested foods stored in refrigerators with a purifying device according to the invention, it was observed that bacterial and fungal contamination generally remained lower (by one to two orders of magnitude, i.e., by a factor of 10 or 100) than in the respective products stored in refrigerators without a purifying device during the monitoring period.

[0056] Sensory evaluation showed that the purifying agent slowed the aging of the test products and delayed the onset of wilting, softening, staining and decay.

[0057] As shown in Table 1 below, evidence from this study shows encouraging results regarding the air purifier's ability to extend the shelf life of fresh food stored in a refrigerator.

[0058] [Table 1]

[0059] It was shown that a coating solution (pH 7.5-9.5) containing the following components is useful for photocatalytic coating of porous ceramic supports.

[0060] [Table 2]

[0061] The components are non-toxic in small amounts (e.g., toxic concentration of WO3: 840 mg / kg).

[0062] Finally, a second embodiment of the air purifying device of the present invention will be described, which offers slightly different construction options and has some differences and commonalities with the first embodiment of the air purifier, particularly those shown in Figures 1 to 5.

[0063] Figure 10 shows a perspective view of a second embodiment of an air purifying device 10' according to the invention, which comprises a housing having an upper portion 12' and a lower portion 14' inserted one into the other. Also shown is an opening 16' for venting air. Reference numeral 28' denotes a battery compartment. In both examples, a wall can be seen at the opening 16', which essentially has two functions:

[0064] A longitudinal cross-section of the air purifier according to FIG. 10, as depicted in FIG. 11, more clearly shows the main components of the system. Air enters the housing through opening 18' (arrow F1'), passes through photocatalytic filter 22', and enters photocatalytic chamber 20'. LED light 21 (LEDs not shown, but reference numbers indicate approximate location) illuminates the top surface of photocatalytic filter 22' with a vertical beam. Air passing through filter 22' and photocatalytic chamber 20' is exhausted from purifier 10' through outlet 16' (arrow F2') with the aid of fan 23'. Electronics 24' controls the LEDs and fan 23' and helps direct airflow through space 18' vertically above filter 22'. A battery in battery compartment 28' powers electronics 24'. Element 26' serves as a push-button interface to the LED ring.

[0065] In this embodiment, the fan 23' is larger than in the first embodiment, improving the performance of the purifier 10'. Similarly, due to the different dimensions of the battery, only the LEDs on the board are visible, and all other elements are hidden.

[0066] By changing the structure of the housing, elements of different sizes (batteries, fans, catalysts, etc.) can be inserted.

[0067] The photocatalytic filter 22' used in the air purifier 10 of FIG. 10 (second embodiment) corresponds to the photocatalytic filter 22'' of the air purifier 10' shown in FIG. 1 (first embodiment). The side length (A') and height (B') of the photocatalytic filter 22 can be changed as needed.

[0068] Figure 12 is a see-through view from below of the air purifying device 10' in Figure 10. Compared to the photocatalytic filter 10 in Figure 1, the inlet 18' is located at the bottom of the air purifying device 10' rather than at the side. In this regard, the lower part 14' of the housing (12', 14') has an annular opening 19' at its bottom so as to surround the basket-like structure 21', and the basket-like structure 21' has the inlet 18' at its side, and its bottom corresponds to the bottom of the lower part 14' of the housing.

[0069] Figure 13 shows the light intensity measurement results, i.e., heat map, on the photocatalytic filter of Figure 12 versus the number of light sources (LEDs). Brighter images indicate higher light intensity. Compared to the photocatalytic filter 22 in the first embodiment, the arrangement of the LEDs has been changed here to be essentially circular (with two additional LEDs slightly placed outside the circle).

[0070] Image A on the left shows how the filter 22' is illuminated in the range of 0 to 11k lux, while image B in the middle confirms the same result in the range of 0 to 300 lux (the target value for system operation). The large circular area encloses the zone where the filter is operating correctly. Compared to the LED arrangement in Figure 5, operation is optimized.

[0071] In image C on the right, you can see the placement of the individual LEDs. It shows that there is a small area in the center that does not perform according to specification, below 300 lux. This is a compromise chosen by the inventors to optimize battery consumption. If a problem occurs, it is enough to increase the brightness of the LEDs slightly to cover the central "defective" area.

[0072] The LED arrangement in this embodiment can also be described as a decagon, with each LED occupying one vertex. Two LEDs are arranged to form a triangle with the two LEDs at either end of one side of the decagon, and two of the sides of the triangle are separated by another side of the decagon with the other LED. This LED arrangement is particularly advantageous for conserving battery power while nearly optimally utilizing the photocatalytic filter.

[0073] In particular, in the second embodiment, the inlet 18' is located in a basket-like structure 21' that is accessible from below through an annular opening 19' in the bottom 14'. This particular configuration reduces the power consumption by approximately 25% to process the same flow rate.

Claims

1. An air purifying device (10; 10') for use in a refrigerator, comprising: (a) a housing (12, 14; 12', 14') with an inlet (18; 18') for a fluid, in particular air, and an outlet (16; 16') for said fluid; (b) a photocatalytic chamber (20; 20') through which said fluid can pass and which communicates with said inlet (18; 18') and said outlet (16; 16'); Equipped with The photocatalytic chamber (20; 20') (b-1) a photocatalyst (22; 22') consisting of a ceramic foam carrier coated with a layer containing tungsten trioxide; (b-2) a visible light source for activating the photocatalyst (22; 22'); Equipped with An air purification device (10; 10') characterized in that

2. Preferably, the fluid path is configured such that the filter (22; 22') is arranged perpendicular to the path and thus to the flow of said fluid. Air purification device (10; 10') according to claim 1, characterized in that it

3. the layer further comprises tin oxide and silver oxide; Air purification device (10; 10') according to claim 1 or 2, characterized in that it comprises:

4. the weight ratio of tungsten trioxide, tin oxide, and silver oxide is 0.9-1.1:1.3-1.7:0.05-0.15, particularly about 1:1.5:0.1; Air purification device (10; 10') according to claim 3, characterized in that it

5. It also contains platinum, Preferably, the weight ratio of platinum to tungsten trioxide is 0.9-1.1:0.9-1.1, in particular about 1:

1. Air purification device (10; 10') according to claim 3 or 4, characterized in that it

6. The ceramic foam support is aluminum oxide Al ２ O ３ and SiO ２ Consists of: Air purification device (10; 10') according to any one of claims 1 to 5, characterized in that it comprises:

7. the pores of the ceramic foam carrier have a density of 8 to 10 ppi (pores per inch); Air purification device (10; 10') according to any one of claims 1 to 6, characterized in that it comprises:

8. the tungsten oxide layer is in direct contact with the ceramic foam support without an intermediate layer of primer; Air purification device (10; 10') according to any one of claims 1 to 7, characterized in that it comprises:

9. The visible light source for activating the photocatalyst (22') comprises a plurality of LEDs, the plurality of LEDs being arranged one at each vertex of a decagon, and two further LEDs being arranged to form a triangle together with two LEDs at both ends of one side of the decagon, and two of the sides of the triangle together with another LED being separated by another side of the decagon. An air purification device (10') according to any one of the preceding claims, characterized in that it comprises:

10. The lower part (14') of the housing (12', 14') has a bottom provided with an annular opening (19') surrounding a basket-like structure (21'), and the basket-like structure (21') has the inlet (18') on its side, and its bottom corresponds to the bottom of the lower part (14') of the housing. An air purification device (10') according to any one of the preceding claims, characterized in that it comprises:

11. Equipped with an air purification device (10; 10') according to any one of claims 1 to 10, A food refrigerator characterized by:

12. A method for keeping a refrigerator clean and odor-free and for extending the shelf life of fruits and vegetables, comprising: (i) preparing the refrigerator according to claim 11; (ii) activating the photocatalyst (22; 22') by irradiating it with the light source; (iii) circulating the air in the refrigerator through the air purifier (10; 10'); Including, A method characterized by:

13. A photocatalyst (22; 22') for an air purification device, Aluminum oxide Al ２ O ３ and SiO ２ a ceramic foam carrier having a pore density of 8 to 10 ppi and coated with a layer containing tungsten trioxide, tin oxide, and silver oxide, wherein the weight ratio of tungsten trioxide to tin oxide to silver oxide is 0.9 to 1.1:1.3 to 1.7:0.05 to 0.15, preferably about 1:1.5:0.1; A photocatalyst (22; 22') characterized by:

14. 14. A method for producing a photocatalyst (22; 22') according to claim 13, comprising the steps of: (α) Al ２ O ３ and SiO ２ providing a ceramic foam carrier based on the above, having a pore density of 8-10 ppi, and preferably cleaned with compressed air; (β) immersing the ceramic foam carrier in an aqueous bath containing tungsten trioxide, tin oxide, and silver oxide in a weight ratio of 0.9-1.1:1.3-1.7:0.05-0.15, particularly about 1:1.5:0.1; (γ) drying the thus coated support, preferably with compressed air or heating at 70-80° C.; Including, A manufacturing method characterized by:

15. No primer is applied between the step (α) and the step (β). The method according to claim 14 .

Images