Air purifier for refrigerator

Abstract

The invention relates to an air purifier (10; 10 '), containing in the path of air flow through the purifier: a photocatalyst (22; 22- ), wherein a tungsten oxide (WO3)-based layer is applied to a ceramic foam support. The layer may also contain tin oxide and silver oxide, and platinum. The oxide layer may be applied by impregnation without applying a primer. A method for increasing the shelf life of fruits, in particular strawberries, salads and vegetables, in a refrigerator and related refrigerators are also described. The purifier is characterized by low energy consumption benefited from using white light to activate the photocatalyst (22; 22 '), and at the same time, the toxicity influence is also very small.

Description

Technical Field

[0001] The present invention relates to an air purifier for use in a refrigerator, the air purifier comprising: a housing having an inlet for a fluid, in particular air, and an outlet for the fluid; and a photocatalytic chamber adapted for the fluid to pass through and in communication with the inlet and the outlet, the photocatalytic chamber further comprising a photocatalyst and a light source for activating the photocatalyst. Background Art

[0002] Several air purifiers are known for keeping the indoor environment of homes and workplaces, industrial spaces and laboratories clean. These purifiers utilize the purification capabilities of plants or filters, the filters including photocatalytic filters that are generally based on titanium oxide and activated using ultraviolet (UV) light. The materials themselves and the UV rays pose many problems in terms of toxicity, such as the formation of ozone, as well as high energy consumption.

[0003] In sensitive environments, such as refrigerators for storing food, such purifiers are not ideal and are often unsatisfactory in eliminating odors and microorganisms to increase the shelf life of, for example, fruits and vegetables. Summary of the Invention

[0004] The object of the present invention is to overcome the above-mentioned drawbacks and to propose an air purifier for use in a refrigerator, characterized by low energy consumption, reduced ozone emissions and non-toxic materials for humans. Another object of the present invention is to propose a related air purifier that reduces the total bacterial load during use in a refrigerator, such that the shelf life of vegetables, salads and fruits, especially strawberries, is significantly increased.

[0005] In a first aspect of the present invention, this object is achieved by the purifier initially described, wherein the photocatalyst comprises a ceramic foam carrier coated with a layer containing tungsten trioxide, and wherein the light source is a visible light source.

[0006] Preferably, the fluid path is configured such that the photocatalytic filter is placed perpendicular to the path, and thus perpendicular to the fluid flow. Positioning the filter perpendicular to the flow can minimize the loss of the photocatalyst loading.

[0007] In a preferred embodiment of the present invention, the visible light source for activating the photocatalyst comprises a plurality of LEDs arranged in a decagon, with each vertex occupied by an LED, and two additional LEDs arranged so as to form a triangle, wherein the two LEDs are located at two vertices of the same side of the decagon, and wherein the two sides forming the triangle with the additional LEDs are separated by the other side of the decagon.

[0008] In another advantageous embodiment of the present invention, the lower side portion of the housing has an annular opening at its bottom, which annular opening surrounds a basket-like structure including a fluid inlet on its side, and the bottom of the basket-like structure corresponds to the bottom of the lower side portion of the housing. The inlet in the basket-like structure communicates with the annular opening and thus with the outside.

[0009] The ceramic foam carrier implies its porosity and allows to avoid using a primer to coat the photocatalytically active substance, thus reducing the processing time and cost. A preferred immersion bath for applying a WO 3 -based coating (e.g., product CLC-W from Inpigest srl, Bodio Lomnago, Italy) is aqueous and preferably further contains a fixative and a promoter.

[0010] In a preferred variant of the present invention, the layer further includes tin oxide and silver oxide. Tin oxide and silver oxide are oxides combined with tungsten trioxide for reducing the total bacterial count (TBC). A particularly suitable composition of the layer contains these three oxides, wherein the weight ratio of tungsten trioxide, tin oxide and silver oxide corresponds to 0.9-1.1∶1.3-1.7∶0.05-0.15, especially approximately 1∶1.5∶0.1.

[0011] The purification effect can be further improved by adding platinum, and advantageously, the weight ratio of platinum to tungsten trioxide is 0.9-1.1∶0.9-1.1, especially about 1∶1.

[0012] Even without using a primer, the ceramic foam carrier particularly suitable for being coated with the oxide-based layer contains alumina Al 2 O 3 and silica SiO 2 . Surprisingly, the ceramic filter for filtering molten aluminum and its molten alloys is particularly suitable for the purposes of the present invention. Advantageously, the pores of the ceramic foam carrier have a density of 8 ppi - 10 ppi (pores per inch), which has been proven particularly suitable for ensuring a sufficient flow rate of the fluid to be purified while cleaning the fluid chemically and microbiologically.

[0013] In a highly preferred variant of the present invention, the tungsten trioxide-based layer is in direct contact with the ceramic foam carrier without an intermediate primer layer. The coating adheres directly to the ceramic foam.

[0014] Photocatalysis is a surface phenomenon. The coating on a carrier with a large amount of available surface, i.e., the ceramic open-cell foam geometry, promotes photocatalysis. It is necessary to have the lowest pressure drop, thus the lowest pressure drop of the photocatalytically active substance, to ensure the effectiveness of the system. Using a ceramic foam of 8 ppi - 10 ppi also helps to reduce the load.

[0015] During the production process of the filter, a support for WO 3 and other oxides and metals is pretreated to receive the material. The pretreatment procedure includes cleaning the support; instead, it is not necessary to apply a primer to promote the adhesion of the photocatalytic material. The use of foam ceramics can skip the "primer" step because foam ceramics are very porous and allow the coating to be well fixed on the support.

[0016] Another aspect of the present invention relates to a refrigerator for food, which includes an air purifier according to the present invention. During the use of the purifier, such a refrigerator has an internal environment that is odorless and hardly contaminated by chemicals and microorganisms, which can significantly increase the shelf life of fruits, vegetables, and salads. The air purifier can be simply placed in the refrigerator or fixed on the inner wall of the refrigerator through relevant fixing devices.

[0017] Another aspect of the present invention relates to a method for keeping the inside of a refrigerator clean and odorless and for increasing the shelf life of fruits, salads, and vegetables, the method comprising the following steps:

[0018] (a) Providing a refrigerator according to the present invention;

[0019] (ii) Activating the photocatalyst by irradiating the photocatalyst with a light source; and

[0020] (iii) Circulating the air present in the refrigerator through the air purifier.

[0021] In order to generate a fluid flow from the inlet through the photocatalytic system to the outlet, the purifier according to the present invention further includes a fan or pump system.

[0022] The fourth aspect of the present invention relates to a photocatalyst for an air purifier, particularly for a refrigerator, which comprises a ceramic foam support based on Al 2 O 3 and SiO 2 with a pore density of 8 ppi - 10 ppi, the support being coated with a layer containing tungsten trioxide, tin oxide, silver oxide, and preferably platinum 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.

[0023] As will be described below, such a photocatalyst is particularly suitable for increasing the shelf life of fruits, vegetables, and salads in a refrigerator, and thus is particularly suitable for use in an air purifier for a refrigerator according to the present invention. This effect is particularly evident in the storage of strawberries, which usually tend to rot after two or three days.

[0024] Another aspect of the present invention relates to a method for producing the above-mentioned photocatalyst, comprising the following steps:

[0025] (α) Providing a foamed ceramic support based on Al 2 O 3 and SiO 2 , having a pore density of 8 ppi - 10 ppi, preferably cleaned with compressed air;

[0026] (β) Immersing the foamed ceramic support in an aqueous bath containing tungsten trioxide, tin oxide, silver oxide and preferably platinum, with a weight ratio of 0.9 - 1.1∶1.3 - 1.7∶0.05 - 0.15∶0.9 - 1.1, especially about 1∶1.5∶0.1∶1;

[0027] (γ) Drying the thus-coated support, preferably by direct spraying with compressed air or accelerated by means of a dryer, preferably heated to 70°C - 80°C.

[0028] In a highly preferred variant of the production method, no primer is applied between step (α) and step (β). This may be due to a specific combination of the support and the coating. The evaporation of water usually lasts for several hours, for example three hours.

[0029] As an alternative to step (β), it is possible to consider using, for example, a gun with a nozzle having a diameter of 1.5 mm - 2 mm for spray treatment to spread a uniform atomized coating on the surface of the support.

[0030] The photocatalytic filter according to the present invention is renewable. The dirt on the filter may be caused by organic materials deposited due to the low efficiency (low surface area, crystalline phase), non-uniformity and / or insufficiency and / or too short illumination of the photocatalyst after long-term use and not degraded by the photocatalyst. The surface area and porosity of the photocatalyst are physical properties that affect the quality and performance of porous materials. For materials of the same weight and volume, their surface activity and adsorption volume may be different according to their specific surface area. The porosity is measured by heating the filter under vacuum to remove impurities and then analyzing the adsorbed gas volume at a specific pressure and low temperature (for example, 77 K in liquid nitrogen). The BET (Bruna uer - Emmett - Teller) theory is the most widely used model for determining the area. To measure the pore size by gas adsorption, the isotherm from low pressure to saturation pressure is recorded. The pressure range is determined by the size range of the pores to be measured: microporous materials are measured by the isotherm in the pressure range of about 0.00001 Torr to 0.1 Torr, while mesoporous materials are usually measured by the isotherm in the pressure range of 1 Torr to about 760 Torr. Since the area of the material is very small, krypton Kr must be used as the gas to make the surface area value S BETIt has good precision. The photocatalytic filter according to the present invention preferably has an S value in the range of 0.9 to 0.44 (m / g). BET value (m 2 / g).

[0031] X-ray fluorescence (XRF) is an analytical technique that can be applied to most inorganic materials to identify foreign materials in the filter and determine the regeneration efficiency and residual materials of the filter. Different regeneration methods were tested using this technique.

[0032] Simply heating to 250 °C is not sufficient, and cleaning with hydrogen peroxide is also not sufficient to regenerate the filter. The combination of cleaning with sodium hypochlorite and subsequent hydrogen peroxide and final heat treatment is satisfactory. Immersing the filter in 30% (w / w) hydrogen peroxide for 24 hours and then calcining in air at 250 °C for 5 hours still shows the presence of organic materials. On the other hand, treatment with hypochlorite was proven to be suitable. For example, the material can be immersed in a hypochlorite solution for two hours, then recovered and immersed in a 3% (w / w) hydrogen peroxide solution, followed by heating. Washing in hydrogen peroxide serves a dual purpose, namely to eliminate residual hypochlorite (and thus its unpleasant odor) and to further oxidize any residues that resist the action of hypochlorite. The material so treated is then heat-treated. At the end of the treatment, the material is white. The tungsten W content in the sample was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) analysis, and the anti-regenerability of tungsten oxide was demonstrated.

[0033] The features and advantages described for one aspect of the present invention can be adapted, mutatis mutandis, to other aspects of the present invention.

[0034] Industrial applicability is evident since the shelf life of food can be increased with an air purifier, which is related to a low-energy consumption system without toxicity problems.

[0035] The objects and advantages will be further highlighted in the disclosure of the preferred examples of the embodiments of the present invention given by way of non-limiting example only.

[0036] Variations and further features of the present invention are the subject of the dependent claims. A description of the preferred example embodiments of the present invention is given by way of example and not limitation with reference to the accompanying drawings. In particular, unless otherwise stated, the number, shape, size, and material of the system and the individual components can vary, and equivalent elements can be applied without departing from the inventive concept. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A perspective view showing an embodiment of an air purifier according to the present invention is shown.

[0038] Figure 2 Shown according toFigure 1 Longitudinal section of an air purifier.

[0039] Figure 3 Shows Figure 1 Perspective view of a photocatalytic filter used in an air purifier.

[0040] Figure 4 Shows Figure 3 Details in the cross-section of the photocatalytic filter.

[0041] Figure 5 Shows Figure 3 Measurement results of the light intensity or heat map on the photocatalytic filter, as a function of the number of applied LEDs (light-emitting diodes).

[0042] Figure 6 The reduction of formaldehyde in a purifier with a titanium dioxide-based photocatalytic filter after UV light irradiation is shown in the graph.

[0043] Figure 7 The reduction of formaldehyde in a purifier with a tungsten trioxide-based photocatalytic filter after visible light irradiation is shown in the graph.

[0044] Figure 8 The reduction of the total bacterial count (TBC) in a purifier with a titanium dioxide-based photocatalytic filter after UV light irradiation is shown in the graph.

[0045] Figure 9 The reduction of the total bacterial count in a purifier with a tungsten trioxide-based photocatalytic filter using visible light irradiation is shown in the graph.

[0046] Figure 10 Perspective view showing a second exemplary embodiment of the air purifier according to the present invention.

[0047] Figure 11 Shows according to Figure 10 Longitudinal section of the air purifier.

[0048] Figure 12 Shows Figure 10 Bottom perspective view of the air purifier.

[0049] Figure 13 Shows according to Figure 10 Measurement results of the light intensity or heat map on the photocatalytic filter of the air purifier, as a function of the number of applied LEDs (light-emitting diodes). Detailed description

[0050] Figure 1A perspective view showing an example of an embodiment of an air purifier 10 according to the present invention, the air purifier including a housing having an upper portion 12 and a lower portion 14, one of which is embedded in the other. Further, an inlet 16 for air discharge can be noted. Reference numeral 28 denotes a battery case.

[0051] As Figure 2 shown, a longitudinal section of the air purifier according to Figure 1 better shows the main parts of the system. Air enters the housing through inlet 18 (arrow F1), passes through the photocatalytic filter 22 in the photocatalytic chamber 20, where the LED lamp 21 irradiates the upper surface of the photocatalytic filter 22 with vertical light. After passing through the filter 22 and the photocatalytic chamber 20, the air is discharged from the purifier 10 through the outlet 16 with the help of the fan 23 (arrow F2). The electronic device 24 controls the LED and the fan 23, and the fan 23 helps to generate a gas flow that vertically reaches the filter 22 through the space 18. The battery in the battery case 28 powers the electronic device 24. Element 26 acts as an interface with the LED ring button.

[0052] Figure 3 The photocatalytic filter 22 used in the air purifier is shown in a perspective view, while Figure 1 the air purifier of Figure 4 shows Figure 3 details in the cross-section of the photocatalytic filter.

[0053] Ceramic foam filters (e.g., the brand VUKOPOR of Lanik s.r.o., Boskovice, Czech Republic A) were originally designed for filtering aluminum and non-ferrous metal alloys in foundries, especially in the primary and secondary processing of molten metals, and for filtering melts in foundries, and have proven to be particularly suitable for use as filters. Surprisingly, such filters have proven to be very suitable for this completely different field of the present invention and also allow the avoidance of using a primer during the process of coating them with the oxide WO 3 The typical characteristic of the structure of the foam ceramic filter is a three-dimensional network of open pores that form a labyrinthine structure in its ceramic body. It is this structure together with the filter ceramic that optimizes the coverage of the tungsten oxide layer and allows for uniform air flow over a large area. The filter has a typical homogeneous ceramic structure with a minimum of restriction points both in the effective area and inside the filter, and is chemical-resistant and heat-resistant. The chemical composition of the filter has an active adhesion strength with respect to the substance to be applied.

[0054] For all types of filters of various sizes and shapes, sealing or expandable gaskets can be provided for them to fix the filter in the correct position and avoid bypass flow of the filter. It is recommended to preheat the filter (350 °C–400 °C) before first use to obtain maximum speed and filtering capacity. Advantageously, the ceramic material comprises Al 2 O 3 and SiO 2 . The porosity is 8 ppi - 10 ppi (pores per inch).

[0055] Preferably, there are no closed pores, cracks or fractures in the active area of the filter. The side length (A) and height (B) can vary as required.

[0056] Figure 5 Describes Figure 3 Measurements of the light intensity or heat map on a photocatalytic filter as a function of the number of light sources (LEDs) applied. The brighter the image, the higher the light intensity. In a top view, the selected light configuration can be seen on the right, and the light intensity (heat) image generated by the configuration on the right can be seen on the left. The middle figure shows the corresponding heat intensity scale (heat increases with clarity).

[0057] Each photocatalyst requires a specific wavelength to be activated. WO 3 Requires and allows wavelengths in the visible light range. Advantageously, the wavelength is equal to approximately 450 nm. For example, the filter surface requires 300 illuminance (lux) to be activated. The illuminance reaching the filter can be adjusted by the intensity of the LEDs (measured in lumens), the distance between the LEDs and the surface of the photocatalyst, and the number of LEDs used. Based on the selection of the number of LEDs and the lumens per LED, the power required to operate the LEDs and thus the associated power consumption will vary. In the purifier according to the present invention, the illumination of the filter has been optimized to minimize energy consumption. In this sense, as uniform as possible illumination of the filter can be achieved by increasing the LEDs, reducing the area with an illuminance <300, and reducing the area with an illuminance >>300. From Figure 5 As can be seen from the analysis shown, by increasing the number of LEDs, the area with excessive illuminance in this application can be restricted. This also results in lower energy absorption, which in the specific case shown corresponds to a reduction from a total of 110 mW to 100 mW.

[0058] There is an energy advantage in converting from UV-A LEDs to activating a titanium oxide-based coating. In terms of the power absorbed, in the case of the same number of LEDs and their positioning, in a specific example, using UV LEDs and TiO 2Photocatalyst, the electric power absorbed by the LED is limited by the firmware to 3.75% of its capacity, such that each LED absorbs approximately 50 mW of electric power, for a total of 200 mW. Using white LEDs and WO 3 Photocatalyst, the maximum power that each white LED can absorb is approximately 43 mW. By default, this value is set to 50%, so the power value is set to approximately 21.5 mW. Under the same conditions, i.e., when both the UV LED and the white LED are at 100% of their possible power, the current consumption of the white LED is -98% of that of the UV LED, resulting in a significant energy saving. Another advantage is that the white LEDs can all be connected in series, and the current consumption is halved compared to the case where the UV LEDs are forced to be divided into different branches. Finally, the lifespan of the UV LED is 3,000 - 4,000 hours, while that of the white LED is 40,000 - 60,000 hours. In terms of environmental pollution, this ensures less waste generation and also reduces the user's cost.

[0059] In tests conducted in the laboratory using a prototype, the actual difference in the efficacy of the new WO 3 coating was studied relative to the TiO 2 coating. Different from the filter based on tungsten oxide, in the case of TiO 2 , the TBC does not return to zero after eight hours.

[0060] Figure 6 The reduction of formaldehyde in a purifier with a titanium dioxide-based photocatalytic filter after UV light irradiation is shown in the graph. Relative to natural attenuation (upper curve), the use of a TiO 2 -based filter reduces the formaldehyde concentration more quickly in a fairly linear trend. Sampling was carried out at the initial contamination, and other points were interpolated after 60 minutes, 150 minutes, and 300 minutes of photocatalytic treatment.

[0061] In contrast, Figure 7 the reduction of formaldehyde in a purifier with a tungsten oxide-based photocatalytic filter after visible light irradiation is shown in the graph. The tungsten trioxide filter reduces formaldehyde very quickly within the first two hours and almost eliminates it after two hours.

[0062] In Figure 8 and Figure 9 's two graphs, the TBC at 0 minutes and 10 minutes when the purifier is off can be seen on the left, and the sample data at 1 hour, 2 hours,..., up to 8 hours after the purifier is turned on is on the right.

[0063] It can be seen from the results that the visible light system is faster and, most importantly, more durable.

[0064] In 2020, TiO 2 was classified by IARC( I nternational A gency for R esearch on C ancer (International Agency for Research on Cancer) as a possible human carcinogen (Group 2B). In 2021, after being used in the food industry for many years, TiO 2 was determined to be an unsafe food additive (EFSA( E uropean F ood S afety A uthority) - the European Food Safety Authority). The CAS number of tungsten trioxide is 1314 - 35 - 8 and the EC number is 215 - 231 - 4. The full dossier is available on the website of the European Chemicals Agency (ECHA (European Chemical Agency)): https: / / echa.europa.eu / registration-dossier / - / registered-dossier / 15315 / 2 / 3. WO 3 is classified as non-PBT (Persistent, Bioaccumulative and Toxic) and non-vPvB (Very Persistent and Very Bioaccumulative). The European Food Safety Authority (EFSA) has expressed a positive opinion on WO 3 (CAS number: 39318 - 18 - 8) as an additive used in materials in contact with food.

[0065] Figure 8 shows in graphical form the reduction in the total number of bacteria in a purifier with a titanium dioxide-based photocatalytic filter after UV light irradiation, while Figure 9 shows in graphical form the reduction in the total number of bacteria in a purifier with a tungsten oxide-based photocatalytic filter after visible light irradiation.

[0066] Laboratory tests have shown that thanks to photocatalytic technology, the purifier according to the present invention removes more than 80% of the odors and VOCs (volatile organic compounds) from the refrigerator, preventing cross-contamination between foods in the refrigerator and changes in sensory properties.

[0067] The inventor conducted an experiment in collaboration with INSTM (National Inter-university Consortium for Materials Science and Technology), in which artificial contamination using two odoriferous compounds was used. It was confirmed that the purifier eliminated 80% of the selected compounds within 24 hours and 50% of the selected compounds within 5 hours. The experiment was conducted with hexanal and amyl butyrate, and these molecules resemble the smell of putrefaction at high concentrations. ArcoSolution (a spin-off of the University of Trieste) conducted an experiment to reduce the actual contamination of refrigerators: it was verified that thanks to the purifier, the VOC concentration in a newly filled refrigerator remained at a very low level, with an 80% reduction after only 5 hours. Thanks to the photocatalytic technology, the purifier according to the present invention reduces the bacterial and fungal load on the food in the refrigerator, even by up to 10 times, and increases the shelf life of fruits, salads and vegetables by up to 7 days, delaying the appearance of wilting, softening, spotting and rotting.

[0068] It can be seen from the experiment that WO 3 reduced the total number of bacteria faster and, most importantly, more persistently; it should be noted that after the fourth hour of operation, the total number of bacteria (TBC) had fluctuated between 0 and 2, which are almost similar from a microbiological and statistical perspective.

[0069] Therefore, the superiority of the filter based on tungsten oxide (WO 3 ) over the filter based on titanium dioxide (TiO 2 ) was proven in two experiments, one microbiological and one chemical.

[0070] The microbiological experiment was conducted in an environment of approximately 8 m 3 , and the chemical experiment was conducted in an environment of approximately 4 m 3 . The device under test was placed one at a time in the center of the experimental environment, and a pollutant sampling was carried out using an instrument called "Uniphos precision air sampling pump", which consists of a high-precision manual pump with a colorimetric flask inserted, and the colorimetric flask is colored proportionally according to the amount of the analyte to be detected present in the inhaled air (method: standard EN ISO 17621:2015). In the case of TiO 2 , the reduction was 67.6% after 1 hour and 86.5% after 8 hours, while in the case of WO 3In this case, it decreased by 81.5% after 1 hour and by 99.9% after 8 hours.

[0071] The most well-known photocatalyst is titanium dioxide (TiO 2 ), which is the most widely used material to date. TiO 2 requires UV light to be activated. In the purifier according to the present invention, the photocatalyst is based on tungsten trioxide (WO 3 ), which has several advantages: it is a safer material as it does not produce ozone without using light in the UV band and avoids the application of more stringent usage regulations as visible light is harmless if it comes into contact with the eyes; it is a lower-cost technology given that visible light LEDs have a lower cost and lower energy consumption; and WO 3 has better air purification effect.

[0072] The tests conducted showed that there was no ozone emission in the short term (continuous operation for five hours); a small amount of ozone was observed after 24 hours of operation, which may be due to the heat released from continuous operation for 24 hours in a sealed enclosure of less than 1 cubic meter (0.57m 3 ). In any case, the recorded values were negligible and significantly lower than the threshold of 0.2 mg / m 3 indicated by the WHO (World Health Organization). The recorded values were more than 100 times lower. For the test, the purifier according to the present invention was turned on for 5 hours and 24 hours in a sealed enclosure with dimensions of 1.70 m × 45 cm × 75 cm, and only ambient air was present in the enclosure. Analysis was carried out using an impinger solution characterized by iodide ions, which was capable of capturing ozone and forming iodide ions. The specific details can be found in the following scientific article: "Determination of Ozone in air by Neutral and AlkalineIodide procedures", D.H. Byers, B.E. Satzman, American Industrial HygieneAssociation Journal, (1958), 19(3), 251 - 257. It was observed that there was no ozone emission in the short term, and a small amount of ozone was observed after 24 hours of operation, which may be due to the heat released from continuous operation for 24 hours of the device in a sealed enclosure of less than 1 cubic meter (0.57m 3 ).

[0073] To understand the habits of users in using household refrigerators, the energy consumption was monitored. It can be seen that the refrigerator door is opened 20 to 50 times a day (average 32 times). This affects 7% of the annual energy consumption (up to 23% at most), with an average of approximately 50 kWh to 120 kWh: equivalent to 20 dishwasher cycles or 50 washing machine cycles. Especially when the frequency is fixed, the consumption of the refrigerator is proportional to the refrigeration cycle performed by the compressor. Since each opening of the refrigerator introduces unclean air and requires the purifier to be started more frequently, it is desirable to achieve energy savings in the purifier.

[0074] In the food tested in the laboratory and stored in a refrigerator with a purifier according to the present invention, it was observed that, compared to the corresponding products stored in a refrigerator without a purifier, during the monitored time period, the bacterial and fungal contamination generally remained low (even 1 - 2 orders of magnitude lower, which means 1 to 10 and 1 to 100).

[0075] Sensory evaluation shows that the purifier can effectively slow down the aging of the test products and delay the appearance of wilting, softening, color spots, and rotting.

[0076] The evidence obtained from the research has produced encouraging results, that is, the purifier can extend the shelf life of fresh food stored in the refrigerator, as shown in Table 1 below:

[0077] Table 1

[0078]

[0079] To prepare a photocatalytic coating on a porous ceramic carrier, a coating solution with the following composition (pH 7.5 to 9.5) has been shown to be useful:

[0080]

[0081]

[0082] These components are non-toxic at low concentrations (for example: the toxicity concentration of WO 3 is 840 mg / kg).

[0083] Finally, a second exemplary embodiment of the air purifier according to the present invention is described. Except for slightly different construction choices, this embodiment provides certain differences and similarities compared to the first exemplary embodiment of the air purifier shown especially with reference to Figures 1 to 5 and shown.

[0084] Figure 10Shows a perspective view of a second embodiment of the air purifier 10' according to the present invention. The air purifier 10' includes a housing having an upper side portion 12' and a lower side portion 14' with one embedded in the other. Also noted is the opening 16' for air escape. The reference numeral 28' denotes the battery compartment. In both examples, a wall portion can be seen in the opening 16', which essentially has two functions: the wall portion is an affordance element of the product opening and serves as protection for the fan.

[0085] As Figure 11 shown, the longitudinal section of the air purifier according to Figure 10 better shows the main parts of the system. Air (arrow F1') enters the housing through the opening 18', passes through the photocatalytic filter 22' into the photocatalytic chamber 20', where the LED lights 21 (the LEDs are not visible, and the reference numerals indicate their approximate positions) irradiate the upper surface of the photocatalytic filter 22' with vertical light beams. After the air passes through the filter 22' and the photocatalytic chamber 20', it is discharged from the purifier 10' through the outlet 16' (arrow F2') with the help of the fan 23'. The electronic device 24' controls the LEDs and the fan 23', and the fan 23' helps generate a gas flow vertically through the space 18' above the filter 22'. The battery in the battery compartment 28 provides power to the electronic device 24'. The element 26' serves as a button interface for the LED ring.

[0086] In the example of this embodiment, the fan 23' is larger than that in the example of the first embodiment, improving the performance of the purifier 10'; similarly, the battery also has different sizes, so only the LEDs on the board can be seen instead of all the other elements.

[0087] The structural changes of the housing enable the embedding of elements of different sizes (battery, fan, catalyst,...); it helps to select different positions for the air inlet, such as from below and / or from the side.

[0088] Figure 10 (Example of the second embodiment) The photocatalytic filter 22' used in the air purifier 10 corresponds to Figure 1 (First embodiment) The photocatalytic filter 22 of the air purifier 10'. The side length (A') and height (B') of the photocatalytic filter 22' can vary according to needs.

[0089] Figure 12 Shows Figure 10 the bottom perspective view of the air purifier 10' in Figure 1Compared with the photocatalytic filter 10, the inlet 18' is not located on the side part of the air purifier 10', but on the lower side part. In this regard, the lower side part 14' of the housing (12', 14') has an annular opening 19' at its bottom surrounding the basket-like structure 21'. The basket-like structure 21' includes the inlet 18' on its side, and its bottom corresponds to the bottom of the lower side part 14' of the housing.

[0090] Figure 13 The results of the light intensity measurement are shown, that is, the Figure 12 thermogram on the photocatalytic filter in is shown as a function of the number of light sources (LEDs) used. The brighter the image, the higher the light intensity. Compared with the photocatalytic filter 22 in the example of the first implementation, the arrangement of the LEDs has changed and is basically circular here (with two additional LEDs slightly outside the circle).

[0091] The left figure A shows the situation where the 22' filter is illuminated in the illuminance range of 0k to 11k, and the middle figure B confirms the same result (the target value of the system operation) in the illuminance range of 0 to 300. The large circular area defines the area where the filter operates normally. Compared with Figure 5 the LED arrangement in, the operation has been optimized.

[0092] In the right figure C, the arrangement of the individual LEDs can be seen. In the figure, the small central area indicates that there is a small area that does not work as specified, but is less than 300 illuminance; this is a compromise chosen by the inventor to optimize the battery consumption. If there is a problem, slightly increasing the brightness of the LEDs is sufficient to cover the central "defective" area.

[0093] The configuration of the LEDs in the example of this implementation can also be described as a decagon, where each LED occupies a vertex, and two additional LEDs are arranged to form a triangle, where the two LEDs are located at the two vertices of the same side of the decagon, and the two sides forming the triangle with the additional LEDs are separated by another side of the decagon. This arrangement of the LEDs is particularly beneficial for almost optimally using the photocatalytic filter while saving battery consumption.

[0094] In the example of the second implementation, especially due to the special structure of the inlet 18' located in the basket-like structure 21', it can enter from below through the annular opening 19' in the bottom 14' of the housing, and processing the same flow rate consumes approximately 25% of the power.

Claims

1. An air purifier for use in a refrigerator (10 ； 10'), which includes: (a) a housing (12, 14; 12', 14'), provided 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') suitable for the passage of the fluid and connected to the inlet (18; 18') and the outlet (16; 16'), the photocatalytic chamber (20; 20') comprising (b-1) a photocatalyst (22; 22') comprising a foam ceramic support coated with a layer containing tungsten trioxide; and (b-2) A visible light source for activating the photocatalyst (22; 22').

2. The air purifier (10; 10') according to claim 1, It is characterized in that The fluid path is preferably arranged in such a way that the filter (22; 22') is perpendicular to the path and thus perpendicular to the fluid flow.

3. The air purifier (10; 10') according to claim 1 or 2, It is characterized in that The layer also includes tin oxide and silver oxide.

4. The air purifier (10; 10') according to claim 3, It is characterized in that The weight ratio of tungsten trioxide, tin oxide and silver oxide corresponds to 0.9-1.1:1.3-1.7:0.05-0.15, in particular about 1:1.5:0.

1.

5. The air purifier (10; 10') according to claim 3 or 4, Features Platinum is also included, and preferably the weight ratio of platinum to tungsten trioxide is 0.9-1.1:0.9-1.1, especially about 1:

1.

6. An air purifier (10; 10') according to any one of the preceding claims, It is characterized in that The foam ceramic carrier comprises aluminum oxide Al 2 O 3 and SiO 2 .

7. An air purifier (10; 10') according to any one of the preceding claims, It is characterized in that The pore density of the foam ceramic carrier is 8 ppi-10 ppi (pores per inch).

8. An air purifier (10; 10') according to any one of the preceding claims, It is characterized in that The tungsten oxide layer is in direct contact with the foam ceramic substrate without an intermediate layer of primer.

9. An air purifier (10') according to any one of the preceding claims, It is characterized in that The visible light source for activating the photocatalyst (22') includes a plurality of LEDs arranged in a decagon, wherein each vertex is occupied by an LED, and two additional LEDs are arranged to form a triangle, wherein the two LEDs are located at two vertices of the same side of the decagon, wherein the two sides forming the triangle with the additional LEDs are separated by another side of the decagon.

10. The air purifier (10') according to any one of the preceding claims, It is characterized in that The lower part (14') of the housing (12', 14') has an annular opening (19') at its bottom surrounding a basket-like structure (21'), the basket-like structure comprising the inlet (18') at its side and having a bottom corresponding to the bottom of the lower part (14') of the housing.

11. A food refrigerator comprising an air cleaner (10; 10') according to any one of the preceding claims.

12. A method for keeping the interior of a refrigerator clean and odor-free and for increasing the shelf life of fruits and vegetables, The following steps are involved: (i) providing a refrigerator according to claim 11; (ii) activating the photocatalyst (22; 22') by irradiating the photocatalyst (22; 22') with the light source; and (iii) circulating the air present in the refrigerator through the air purifier (10; 10').

13. A photocatalyst (22; 22') for an air purifier, comprising: 2 O 3 and SiO 2 A ceramic foam substrate having a pore density of 8ppi-10ppi, the substrate being coated with a layer containing tungsten trioxide, tin oxide and silver oxide, preferably in a weight ratio 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.

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

15. The production method according to claim 14, Features No primer was applied between stage (α) and stage (β).

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