BURTSCHER HEINZ (CH)
KASPER MARKUS (CH)
MAYER ANDREAS (CH)
CZERWINSKI JAN (CH)
BURTSCHER HEINZ (CH)
KASPER MARKUS (CH)
MAYER ANDREAS (CH)
| WO2004101113A1 | 2004-11-25 | |||
| WO2003093734A1 | 2003-11-13 |
| US5637216A | 1997-06-10 | |||
| US6358374B1 | 2002-03-19 | |||
| GB1462211A | 1977-01-19 | |||
| EP0736403A2 | 1996-10-09 |
Claims
1. A method for heating a filtrate mass trapped on a filter material at low temperature filtration to at least 100 degree Celsius, to obtain benefits such as but not limited to drying and suppressing microbial activity in the filtrate mass.
2. The method of heating a filtrate mass as in claim 1, wherein the heating involves conduction of heat via the filter material .
3. The method of heating a filtrate mass as in claims 1 and 2 , wherein the heating involves the generation of heat in the filter material, such as but not limited to resistive heating obtained by the passage of an electric current and/or direct contact to a heat source.
4. The method of heating a filtrate mass as in claims 1-3, wherein the heating involves other routes of heat transmission such as but not limited to convectional heating via the fluid stream to be filtered, and/or radiative heating of the filtrate mass .
5. The method of heating a filtrate mass as in claims 1-4, wherein the heating may be in a continuous manner, but is preferably made in a cyclical or discontinuous manner, to obtain benefits such as but not limited to energy efficiency of heating the filtrate mass whilst the fluid stream to be filtered flows .
6. The method of heating a filtrate mass as in claims 1-5, wherein the filtrate mass is subjected to a periodic mechanical shock, applied by methods such as but not limited to an acoustic shock-wave, a pressure wave, and/or mechanical vibration, to obtain benefits such as but not limited to the deadherence of the filtrate mass from the filter material.
7. The method of heating a filtrate mass as in claims 1-6, wherein the filtrate mass is obtained by filtering a fluid stream, where this fluid stream may be gaseous, liquid, or a mixed fluid medium.
8. The method of heating a filtrate mass as in claims 1-7, wherein the filtrate is obtained by filtering a fluid stream, where this fluid stream may be flowing in a continuous or discontinuous manner, and preferably where the continuous / discontinuous nature of the flow may also be subject to external regulation.
9. The method of heating a filtrate mass as in. claims 1-8, wherein the filtrate is obtained by filtering a fluid stream, and where the imposition of the periodic mechanical shock as in claims 6-8 may take place either when the fluid stream is flowing, or not, and preferably where whether the fluid stream is flowing, or not, is subject to external regulation as in claim 8.
10. The method of heating a filtrate mass as in claims 1-9, wherein the imposition of the mechanical shock as in claims 6-9 may be applied on a regular periodic basis or preferably a basis subject to external regulation, triggered by events such as but not limited to the mass of, and/or thickness of, and/or dryness of, and/or pressure drop across the filter induced by, the filtrate mass .
11. The method of heating a filtrate mass as in claims 1-10, wherein the use of the heating and the imposition of the me ¬ chanical shock as in claims 6-10 causes the deadherence of the filtrate mass without significant structural damage to the filter material, thus allowing benefits such as but not limited to the longevity of function of the filter material, thus allowing benefits such as but not limited to the reuse / recycling / lack of need to change of the filter material, thus allowing benefits such as but not limited to the removal of frequent maintenance / filter changing .
12. The method of heating a filtrate mass as in claims 1-11, wherein this filtrate mass has been formed at low flow velocities (<5cm/sec) of the fluid stream to be filtered, thus allowing benefits such as but not limited to the ability of the filter to capture particles in the nanoparticulate size range of 20-300nm.
13. The method of heating a filtrate mass as in claims 1-12, wherein the filter mass is exposed to ultraviolet radiation, especially an UV-lamp or the sun.
14. An air cleaner filter system device including a method of heating a filtrate mass as in claims 1-13.
15. The air cleaner system including a method of heating a filtrate mass as in claims 1-13, where this device is capable of forming a filtrate mass at low flow velocities (< 5cm/second) of the fluid stream to be filtered, thus allowing benefits such as but not limited to the ability of the filter to capture particles in the nanoparticulate range of 20-3OOnm.
16. The air cleaner system as in claims 14-15 where this device contains filter materials as in claims 1-13 where these filter materials are capable at least in part of conducting heat to the filtrate mass.
17. The air cleaner system as in claims 14-16 where this device contains filter materials as in claims 1-16 where these materials are at least in part preferably made of or contain a heat- conducting material, such as but not limited to metals and ceramics .
18. The air cleaner system as in claims 14-17 where this device contains filter materials as in claims 1-17 where these materials are at least in part preferably made of or contain a heat- generating material, such as but not limited to metals and ceramics able to generate heat as a result of resistive heating when an electrical current is passed through them.
19. The air cleaner system as in claims 14-18 where this device contains filter materials as in claims 1-18 where these filter materials are capable of withstanding a mechanical shock as in claims 6-18 without sustaining significant structural damage.
20. The air cleaner system as in claims 14-19 where this device contains one or more filter materials as in claims 1-19 where at least one of these materials is able to be optimized for filter efficiency (F) for capturing filtrate particles in a certain size range by a formula involving at least the quantities 'filter thickness' (L), 'filter pore size' (P), 'filter web dimension' (Q) and λ fluid flow rate' (C), where one or more of these quantities can be optimized if others are fixed.
21. The air cleaner system as in claims 14-20 where this device contains one or more filter materials as in claims 1-19 where at least one of these materials is able to be optimized for filter efficiency (F) for capturing filtrate particles in a certain size range by a formula involving at least the quantities x fil- ter thickness' (L), 'filter pore size' (P), 'filter web dimension' (Q) and 'fluid flow rate' (C), where one or more of these quantities can be optimized if others are fixed, and where if the formula used is F = L/ (P. Q. C), and the size range of capture includes efficient capture of particles in the nanoparticulate range 20.-300nm the F should be in the range > 10^7 s/m.2 .
22. The air cleaner system as in claims 14-21 where this device contains one or more filter materials able to be optimized according to claims 19-20, where an additional benefit for a given flow stream volume is being able to select physical dimensions of the filter materials such as but not limited to thickness (L) and effective area (A) to obtain benefits such as but not limited to the optimization and/or minimization of these physical dimensions to match certain application situations .
23. The air cleaner system as in claims 14-22 where this device contains filter materials such as but not limited to sintered- metal-powder-masses e.g. sintered metal powder sheet metal structures, and /or sintered-metal-fibre-masses, e.g. sintered metal fibre porous structures.
24. The air cleaner system as in claims 14-23 where this device contains filter materials such as but not limited to hybrid, laminated, coated, or otherwise heterogeneously composed materials, where these materials preferably include material components such as but not limited to sintered-metal-powder-masses e.g. sintered metal powder sheet metal structures , and /or sintered-metal-fibre-masses, e.g. sintered metal fibre porous structures .
25. The air cleaner system as in claims 14-24 where the filter materials may also contain e.g., antimicrobial coatings such as but not limited to nanoparticulate or solid coatings of metals such as but not limited to silver and copper.
26. The air cleaner system as in claims 14-25 where this device also contains a component capable of creating a pressure difference across the filter, such as but not limited to a ventilator, compressor, or fan.
27. The air cleaner system as in claims 14-26 where this device also contains a component capable of creating a pressure difference across the filter, where this pressure difference can be used as a measure of the quantity (mass) and quality (such as but not limited to dryness and porosity) of the filtrate mass, thus enabling a control device measuring this pressure difference and/or components thereof such as but not limited to backpressure, to react to trigger a mechanical shock as in claims 6- 25, simultaneously preferably controlling other aspects of the device such as but not limited to fluid flow, fluid flow velocity, and heating of the filtrate mass.
28. The air cleaner system as in claims 14-27 containing a control device as in claim 26 where this control device is able to provide additional benefits such as but not limited to a higher average efficiency of removal of filtrate material from the fluid stream over time, and such as but not limited to the elimination of low-efficiency filtration * spikes' from the filtration efficiency profile over time /cycles of the filter.
29. The air cleaner system as in claims 14-28 where the dead- hered filtrate, mass can either be collected in a suitable receptacle, and/or allowed to be discarded, and/or allowed to be removed from the vicinity of the device by means such as but not limited to a fluid stream.
30. The air cleaner system as in claims 14-29 where the dead- hered mass can be removed efficiently according to the control system as in claims 25-28 controlling the mechanical shock as in claims 6-28, with the advantages that the filtrate mass is almost entirely removed from the 'dirty' side of the filter, and/or with the further advantage that the control system can regulate the filter cleaning to severely limit the penetration of filtrate to the λ clean' side of the filter.
31. The air cleaner system as in claims 14-30 where the dead- hered filtrate mass can have the added advantage of being largely dry and thus easier to collect and/or dispose of.
32. The air cleaner system as in claims 14-31 as used for air filtration of air already present in nominally enclosed environments in situations such as but not limited to cars, trucks, boats, buses, houses etc.
33. The air cleaner system as in claims 14-32 as used for air filtration of intake air into nominally enclosed environments in situations such as but not limited to cars, trucks, boats, buses, houses etc.
34. The air cleaner system as in claims 14-33 as used for air filtration of intake air into nominally enclosed and air- quality-critical environments in situations such as but not limited to clean rooms, surgical theatres, isolation tents, archival storage compounds, etc .
35. The air cleaner system as in claims 14-34 as used of air filtration of intake air into nominally enclosed environments not hitherto provided with a positive pressure in the nominally enclosed environment, particularly such as but not limited to buses, to provide benefits such as but not limited to expelling rather than drawing in particulate matter.
36. The air cleaner system as in claims 14-35 as used for the air filtration of air in, or air intake in, nominally enclosed environments with the advantage that if this air is heated, this heat is not significantly reduced by the device.
37. The air cleaner system as in claims 14-36 with a control device as in claims 25-33 where this control device may be used in conjunction with other sensors and control devices.
38. An air cleaner system comprising: an inlet and an outlet, creating an air path between the inlet and the outlet, a filter mounted between the inlet and the outlet, an air moving device to create an air flow between the inlet and the outlet through the filter, an heating element adapted to heat said filter, an disruption element to disrupt a filtrate mass accumulated on said filter, an electronic control unit to control the heating element and/or the disruption element based on sensor or time information. '
39. The air cleaner system as in claims 1-13, wherein the filter mass is exposed to ultraviolet radiation, especially an UV-lamp or the sun. ' •
40. A method to clean air comprising: creating an airflow between an inlet and an outlet of a fil ¬ ter system, measuring properties of the filter system as humidity, back pressure, temperature to create control signals, using said control signals to control a heating element adapted to heat said filter and/or an disruption element to disrupt a filtrate mass accumulated on said filter. |
Air cleaner system
Field of the invention
The invention relates to an air cleaner system using a method to heat a filtrate mass .
Prior Art
Methods and devices for filtering a medium are well known by- prior art. It is known that filtered particles are building a filter cake changing the filtering conditions.
WO 03/093734 discloses a filter system to clean an airflow from gaseous contaminants. The filter system uses a heater in order to change bacteria in non-polluting material. It is mentioned that the filter has not to be cleaned manually, when the filter is made of microporous/nanoporous materials as metal oxide frameworks consisting of transition metals, wherein the heater is embedded in the metal oxide/complementary zeolite material. The formation of a filter cake is not mentioned.
CH 688,402 shows a filter system that cleans an airflow from dust . The filter cake is removed by means of rotation of the filter element. The filter element is looped around propel means, due to this redirection, the filter cake cracks. A pres ¬ surised airflow removes the cracked filter cake. This filter system is rather complicated, because it shows various elements that have to be powered by means such as motor. Another drawback is that the filter system is only applicable to systems, which have large dimensions and are stationary.
US 6,585,792 discloses an air filtering system with easily re-
movable and replaceable filter elements. It is a disadvantage of this device that the filter has to be replaced after a certain operation time.
Summary of the invention
Based on the methods and devices of prior art, it is an object of the present invention to provide a method and a device, which is more efficient, more flexible and simpler to use than devices of prior art .
The set object is met in accordance with the invention by means of a method whereas the filtrate mass will be heated by heating means, in order to dry the filtrate mass and to prevent microbial activity.
The set object is further achieved with the invention by means of a method whereas a periodic mechanical shock is imposed to the filter system. The mechanical shock is preferably caused by an acoustic shock-wave, by a pressure wave and/or mechanical vibration. Due to the mechanical shock deadherence of the filtrate mass from the filter material may be obtained.
This is a very easy und comfortable way to clean such a filter element. Due to the cleaning of the filter, the back pressure sinks and the degree of efficiency is better.
The mechanical shock is applied on a regular periodic basis or preferably on a basis subject to external regulation. External regulation is triggered by events, which may be mass of, and/or thickness of, and/or dryness of the filtrate mass, and/or the pressure drop across the filter induced by the filtrate mass.
This makes very comfortable as well, since the filter triggers the impose of the mechanical by itself.
Brief description of the drawings
The drawings will be explained in greater detail by means of a description of an exemplary embodiment, with reference to the following figures:
Fig. 1 shows schematically a cylindrical stand-alone device of a filter device according to the present invention.
Pig. 2 shows schematically half of a top view of the sealing element .
Fig. 3 shows schematically a rectangular stand-alone device of a filter device according to the present invention.
Fig. 4 shows schematically a top view of the filter device of figure 4.
Fig. 5 shows schematically the cross-sectional view of a filter element .
Fig. 6 shows schematically the cross-sectional view of another filter element.
Fig. 7 shows schematically the cross-sectional view of a further filter element.
Fig. 8 shows the filter element of figure 7 in a top view.
Fig. 9 shows schematically the installation under the front seat of car of the filter device according to the present invention.
Fig. 10 shows the same device as Fig. 9, installed behind the back seat of a car.
Fig. 11 shows the same device as Fig. 9, installed on the roof of a bus .
Fig. 12 shows the same device as Fig. 9, installed behind the driving cab of a truck.
Pig. 13 shows the size distribution of particles and the efficiency of different filter types .
Fig. 14 shows the efficiency and back pressure over time of filters of prior art and filters according to the present invention.
Fig. 15 shows the plot of a lung deposition to illustrate that a substantial part of particles smaller than 0.1 μm get trapped in the respiratory tract and cause disease.
Detailed description of the preferred embodiments
Figure 1 shows a device according to the present invention. A casing 4 has the shape of a cylinder, and comprises at least filter chambers 20, 21, a contaminated air inlet 5, an exit 13, a cleaning air assembly 7, 8 ,9 and a filter element 3.
The ventilator 2, fan or a similar air moving device, which is located on one front end of the cylinder, creates a pressure difference across the filter chambers 20, 21. The ventilator 2 is powered by an electric motor 1, alternatively it may be powered by the air stream that is created when the ventilator 2 is located on a driving vehicle, e.g. indirectly by an additional driving fan. It is also possible to arrange the ventilator 2 in front of inlet 5 and pushing the air through the filter chambers 20, 21.
The filter chamber 20, 21 is divided by a tube shaped filter element 3, which will be described by means of figure 6, into an inner cylindrical chamber 21 and into an outer ring-shaped chamber 20. Due to the structure of the filter the created pressure difference is in the ring-shaped chamber 20 as well as in the cylindrical chamber 21. As explained with Fig. 5 it is also possible to use an inverted flow direction.
Due to the pressure difference a fluid stream is generated, a contaminated medium is sucked into the ring-shaped chamber 20 via an inlet 5. Further on the contaminated air enters the filter element 3. The filter element 3 decontaminates the contaminated medium. The filtrate which is obtained from the contaminated medium is held back by the filter element 3 on its outer surface 23, which is the surface that is adjacent to the ring- shaped chamber 20 and its inner structure. A filtrate mass or a filter cake builds itself up on the outer surface 23, which is also designated as "dirty side" and on the surfaces located on the interior of the filter element 3. The medium then passes the inner surface 24 of the filter element, which is also designated as "clean side" . The filter is designed in a way that no or almost no contaminated particles reach the clean side. This is based on the air velocity of the medium passing through the filter and this can be calculated on the basis of the sucked/pushed air volume and the surface and cross-section of the filter element.
Said filtrate has three states: (a) suspended particles in the fluid (air) stream to be cleaned (b) a so called cake as the trapped mass on the filter, which can be wet or dry, depending on the fraction of water, and (c) a deadhered cake collected residue .
The medium is now decontaminated and passes the ventilator 2, an exit 13, a tube 12 and a silencer 11 and leaves the device. The cleaned medium may be used for several purposes such as supply the interior of a car, house etc. with clean air.
In order to maintain a good filter characteristic, which is de ¬ scribed below by means of figure 14, it is necessary to clean
the filter element 3 from the obtained filtrate mass or filter cake. The cleaning process comprises at least a mechanical shock .
The filtrate mass is removed from the filter element 3 by the mechanical shock that is applied to the system. This detaches the filtrate mass from the filter element 3. The mechanical shock may be applied when the fluid stream is flowing or if the fluid stands still . The imposition of the mechanical shock may be applied on a regular periodic basis, on a basis subject to external regulations or triggered by any other event. An event may be the mass of and/or the thickness of and/or the dryness of the filtrate mass or the pressure drop across the filter caused by the filtrate mass. Corresponding sensor elements are not shown in the drawings but are known to someone skilled in the art.
The mechanical shock may be a result of a pressurized air flow. A cleaning air compressor 9 pressurises cleaning air, which is stored in a cleaning air tank 8. As soon as the mechanical shock is required, a valve 7 opens and a pressure-impulse is sent via a cleaning air inlet 14 into the cylindrical chamber 21. The pressure-impulse expands itself in the cylindrical chamber 21 and permeates through the filter element 3. Thereby the filtrate mass will be detached from the filter element 3 and falls down through the ring-shaped chamber 20 to the bottom 19 of the ring- shaped chamber 20. Since the filtrate is built up on the outer side 24, which is the "dirty side", it is ensured that almost no filtrate falls into the inner cylinder 21, which is the "clean side" . A residue slot 6 is shut by a ring-shaped sealing element 16, which shows circular arranged holes 17. The bottom 19 of the ring-shaped chamber 20 comprises also holes 18, which are ar ¬ ranged in the same manner as the holes 17 in the sealing element
16. The sealing element 16 may be turned around a middle axis 15. As soon as the holes 17 overlap the holes 18 it is possible to remove the filtrate mass. Additionally the ventilator 2 can be stopped or even closed through a shutter. The air stored in the air tank 8 can be provided beforehand through, guiding a fraction of the clean air flow 11 into a compression chamber to fill said tank 8. The pressure of the cleaning air pulse may be 3 to 5 bar .
Beside the use of mechanical shocks it is also contemplated to use a heating of the filter element 3. The filter element 3 will be heated by means of an electrical heating circuit 31. The filter material may be made out of or contain heat-generating material such as metals or ceramics in order to generate heat as a result of resistive heating, when a electrical current is passed through the heating circuit 31. A temperature control sensor 32 measures the temperature in the core of the filter element 3. Due to increasing the heat, the filtrate mass will be dried and microbial activity in the filtrate mass will be suppressed. The heat may be conducted via the filter material. It is also possible to provide heat elements adjacent to the filter and use conduction or convection to heat the filtrate mass. It is also much more convenient to collect filtrate from the residue slot 6, which was dried by the heating system 31.
The pressure of the mechanical shock, the temperature and the material as well as the structure of the filter are parameters to dimension the properties of the filter in view of its mechanical stability. Those parameters have to be chosen in order to prevent a mechanical deformation of the filter element 3, when the mechanical shock or the heating is applied.
The filter element 3 comprises material, which allows building a
filtrate mass at low flow velocities, preferably under 5cm/sec of the fluid stream. This allows to capture particles in the nanoparticulate size range of 20 - 300 nm. Such material may be sintered metal powder porous sheet metal structures, sintered metal fibre porous structures and metallised filter structures.
A temperature signal, which results from a temperature sensor
32, and a pressure signal, which results from a pressure sensor
33, will be analysed in a electronic control unit 10. The control unit is able to analyse various parameters of the filter device and to provide signals for various purposes .
The pressure sensor 33 measures the pressure difference inside the cylindrical chamber 21. This pressure difference may be used as a measure of quantity (mass) and quality (such as dryness and porosity) of the filtrate mass. This parameters may be used to trigger the mechanical shock and/or the heating action.
Other parameters such as fluid flow, fluid flow velocity or temperature of the heating may also be controlled.
Furthermore, the control unit is able to make the filter device much more efficient because it starts actions, such as the mechanical shock as described above, in order to maintain a very high efficiency, which means that low-efficient "spikes" will be eliminated from the filtration efficiency profile over time.
The medium which has to be decontaminated may show various states such as gaseous, liquid or a mixed fluid medium. The fluid stream of said medium may be flowing in a continuous or discontinuous manner. The medium may also show various temperatures but due to the compact construction of the filter element the temperature of the medium will not change significantly.
In a further embodiment, which is not shown in the drawings, the mechanical shock may be an acoustic shock-wave or a mechanical vibration.
In a further embodiment, which is not shown in the drawings, the heating involves for example convectional heating via the fluid stream to be filtered and/or radiative heating of the filtrate mass. The heating may be in continuous, cyclical or discontinuous manner.
Figure 2 shows a top view of the sealing element 16. Circular arranged holes 17 give way to the residue as described above.
Figure 3 is a cross-sectional view of figure 4 and shows a further device according to the present invention. Identical or similar features receive the same reference numerals in all drawings. The casing 4 has a cuboid shape. Openings 43 on its outer wall are the inlet for decontaminated air, as well as the outlet of the residue that is removed when the mechanical shock is applied. An electro-mechanical vibrator 41 is used to shake the filter cake of the medium periodically.
The cleaning process as well as any other properties are identical to the embodiment as described in figure 1.
Figure 5 shows the top view of a filter element 3. The filter element 3 has an encasing tube-like shape. Within that tube-like shape the filter shows several pleats 60 in order to enhance its surface. The contaminated medium enters into the filter element 3 in direction of arrow 63. In the filter element 3 the contaminated medium will be filtered and the particles remain in the filter as filtrate mass. The decontaminated medium exits the
filter element 3 into the inner chamber 64.
It is understood, that the flow of the medium may also be reversible as indicated by an arrow 65. In that situation, the medium in the inner part 64 is contaminated and it is being decontaminated when it passes the filter element 3 in the direction of arrow 65.
The filter element 3 may be made out of sintered-metal-powder- masses and/or sintered-metal-fibre-masses and the like. Furthermore, the filter elements may be made out of hybrid, laminated, coated or otherwise heterogeneously composed materials wherein such material components as mentioned before. A further preferred material may also comprise antimicrobial coatings such as nanoparticultae or solid coatings of metals whereas silver or copper may be used. The pore size can be chosen between 10 and 30 micron, whereas the porosity can be between 80 and 90 percent.
The filter material is chosen to be heat resistant up to at least 200 degree Celsius. The heating could also be conducted with a infrared heating source in the centre of the filter unit, e.g. to reach temperatures between 80 and 140 degree Celsius. Such filter material is mentioned before.
Figure 6 shows another filter element 3 in a cross-sectional view. Generally the filter element 3 has the shape of a cylinder and is rotationally symmetric around its middle axis 66. The filter element 3 shows several pleats 60, with the same purpose as already mentioned. The airflows are the same as described in figure 5.
Figure 7 and 8 show a further filter element 3 which is used in
a device as described by means of figure 3. As it can be seen in figure 8, which is the top view, the filter has a rectangular shape. The characteristic and the airflows of the filter element 3 is according to the ones as already described.
Figure 9 shows a first possible application of the device and the method as described above. The filtration system 50 is placed under the front seat 105 of a car 110. In a continuous manner it sucks in contaminated air 100 from the interior of the car. The decontaminated air 101 exits via an opening.
Figure 10 shows a second possible application of the device and method as described above. The filtration system 50 is located in the boot 106 of the car 110.
Figure 11 shows a further application of the device and method as described above. The filtration system 50 is arranged on the roof of a bus 111. Via an intake opening the filtration system 50 sucks in contaminated air 100 from the interior of the bus 111. After decontamination in the filtration system 50 decontaminated air 101 exits the filtration system 50 via a pipe 120. The pipe 120 guides the decontaminated air 101 back into the interior of the bus 111. Depending on the volume of the cabin, several filtration systems 50 have to be arranged.
Figure 12 shows another application of the filtration system, which is arranged on a truck 112. Contaminated air 100 is sucked in to the filtration system via a tube 124. Decontaminated air 101 exits the filtration system 50 via an exit and enters into the interior of the truck.
Within these applications the dimension of the filter system can be chosen to have a face velocity between 5 and 10 cm/s, whereas
the air flow has a value which is equivalent exchanging three to five times the volume of the cabin of the vehicle per hour.
In a further preferred embodiment, which is not shown by the figures, the filtration system is used for any nominally enclosed environments as well as air-critical environments such as surgical theatres and the like.
Figure 13 shows the characteristic of the device and method according to the present invention. Graph 200 shows a possible size distribution of engine soot in ambient air, whereas graph 201 shows a possible size distribution of atmospheric dust in ambient air. Graph 202 shows the characteristic of the efficiency of a standard cabin air filter such as a filter known from prior art. It is obvious that the standard cabin filter is at its most efficient, when the particles are larger than 5 μm.
Since the soot particles are between 0.01 μm and 1 μm it is apparent, that only a little amount of soot particles are filtered with such air filter.
Graph 203 and 204 shows characteristics of a filtration system according to the present invention at various velocities of flow. Graph 203 shows the characteristic of the filtration system with a velocity of flow of 1 cm/s, it can be seen, that the efficiency is nearly 100 percent for all different particle diameters. The efficiency sinks about 5 percent when the particles are in a range between 0.01 and 1 μm. If the velocity of flow around 10 cm/s the efficiency sinks down to 80 percent in said range. However, it can be seen that a device according to the present invention is much more efficient, than the standard cabin air filter, even at larger velocities of the air stream. Therefore air velocities of 2 mm/s to 50 cm/s are contemplated to be used according to the invention, preferably air velocities
of 5 iran/s to 10 cm/s and more preferably air velocities of 1
Figure 14 shows the efficiency over time of the filter system according to prior art (300, 302) and to the present invention (400, 402) .
It can be seen that the efficiency 300 of the filter of prior art starts at around 15 percent increases over time up to 100 percent, this is due to the fact that particles are held back by the filter and a filter cake is built up on the surface of the filter. Due to the filter cake the back pressure 302 is also increasing. When the backpressure 302 reaches a certain limit, the filter has to be cleaned. After cleaning the filter the efficiency 300 is rather low again. In the case that cleaning is equivalent to replacing there is an additional time, wherein there is no filter action or no air flow.
With the filter element 3 according to the present invention the efficiency 400 starts at around 80 percent, which is a high level. Within in a very short time, the filter reaches its maximum efficiency, this is due to the fact particles are held back by the filter and a filter cake is built on the surface of the filter. Due to the filter cake the back pressure 404 increases also. When the backpressure 402 reaches' a certain limit, the filter will be cleaned according to the present invention. In the case that the cleaning step is performed with a closed air outlet, then there is a short time, wherein there is no air flow. After cleaning the filter through de-caking, the efficiency 400 starts at around 80 percent and the backpressure 402 is low as well. The just described cycle starts again. The cycle according to the present invention is around 3 times shorter than the cycle of prior art. This is to minimise the negative
effect of the back pressure. The use of the heating changes the slope of the curve, i.e. reduces the inclination and allows a longer standing time. It is preferable to use the heating in a discontinuous way, to maintain the temperature of the filter and filtrate mass in a range to secure the antimicrobial action and properties of the filter. The back pressure may be between 100 and 500 mbar.
Figure 15 illustrates that there are a substantial proportion of particles under IOOA (O.lum) which get trapped in the respiratory tract and which can cause disease, and that (by comparison with figure 13) such soot particles are not removed by standard cabin air filters of prior art .
Every embodiment described above can be combined with one or more features of any other embodiment from the disclosure. Additionally it is possible to add an ultraviolett light source to the device, directed onto the filter masse to kill biological material, especially viruses, trapped by the filter element. It is possible to provide a lamp emitting UV-radiation near the filter wall elements, it is also possible in case of the embodiments of Fig. 11 and 12 to arrange, preferably additionally, a transparent wall of the filter element near an upper surface of the case of the filter element, so that UV light from the environment, i.e. from the sun, can act upon the filter mass.
Reference Numerals
1 Electric motor
2 Ventilator
3 Filter element
4 Casing
5 Contaminated air inlet
6 Residue slot
Cleaning air valve Cleaning air tank Cleaning air compressor Electronic control unit with pressure and temperature sensors Silencer tube exit Cleaning air inlet middle axis Sealing member Holes Holes Bottom of ring-shaped chamber Ring-shaped chamber for contaminated air Cylindrical chamber for decontaminated air wave-like structure outer surface Heating circuit Temperature Sensor Pressure Sensor casing Vibrator Filter chamber Filtration system Pleat Arrow Inner chamber Arrow Contaminated air Decontaminated air Car Bus
112 Truck 120 Pipe 124 Pipe
200 Distribution of engine soot
201 Distribution of dust
202 Characteristic of standard cabin air filter
203 Characteristic of the filtration system according to the present invention
204 Characteristic of the filtration system according to the present invention
300 Efficiency (prior art)
302 Backpressure (prior art)
400 Efficiency (present invention)
402 Backpressure (present invention)