Patent Application
20220176281
Airborne particles, when inhaled, can cause significant health problems in humans. For example, smog is a type of air pollution that significantly affects human health. Many cities in the world suffer from air pollution associated with smog, and medical problems are caused when individuals breathe in airborne microparticles containing heavy metals and chemical composites that are commonly found in smog. The toxicity of microparticles increases when it is combined with other chemical and biological matters such as water and some low surface tension liquids (e.g., nitric acid and other acids) (forming smog) as well as pathogens. In addition to the artificial microparticles, natural microparticles like plant pollens also cause other health-related problems such as allergies. Additionally, liquid droplets in the air can contain germs, viruses, etc.
An illustrative airborne particle removal system includes a wire filter having a housing that includes a wall. The wall has an interior surface and an exterior surface. The wire filter also has a plurality of layers of wires mounted to the interior surface of the wall of the housing. Each layer in the plurality of layers includes a plurality of wires designed to collect airborne particles from air and release the airborne particles. The system also includes a receptacle configured to receive the airborne particles released from the plurality of wires.
An illustrative method of forming an airborne particle removal system includes forming a housing of a wire filter, where a wall of the housing has an interior surface and an exterior surface. The method also includes mounting a plurality of layers of wires to the interior surface of the wall of the housing, where each layer in the plurality of layers includes a plurality of wires designed to collect airborne particles from air and release the airborne particles. The method further includes positioning a receptacle such that the receptacle receives the airborne particles released from the plurality of wires.
Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description, and the appended claims.
Illustrative embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like numerals denote like elements.
for airborne particle removal systems having design parameters specified in
with respect to the predicted ηac to investigate the effects of design parameters to ηac in accordance with an illustrative embodiment.
Current state-of-the-art air cleaning technology utilizes mesh filters to collect particles within the air. These systems are fundamentally limited because the filters get clogged due to aggregated microparticles, which results in a filter replacement cycle of less than 1 week in some instances (depending on the air pollution level) and added maintenance costs, in addition to the energy costs involved with running the system. Described herein are systems and methods for improving air quality that avoids the problem of rapidly clogging filters and the associated increased maintenance costs to replace them.
In an illustrative embodiment, the proposed system uses wires, which may be flexible, to efficiently collect airborne particles and remove them from the air. As used herein, airborne particles can refer to any combination of chemical particles, biological particles, pathogens, germs, viruses, natural microparticles such as pollen, water, etc. that are present in the air. Through experimentation, it has been determined that wires with smaller diameters lead to better fog/smog collection efficiency per unit area. In this document, the terms ‘smog’ and ‘fog’ are used interchangeably. Moreover, the bending of flexible wires can facilitate the transport of collected smog particles using an air drag force and/or gravity so that the clogging issue can be prevented. Similarly, vibration of the flexible wires in combination with air flow (e.g., wind) can also help to transport the collected airborne particles off the wires so that they do not become clogged. Additionally, the modification of surface properties such as texturing the surfaces with nanostructures can provide additional useful functionalities such as self-cleaning and anti-bio/chemical fouling of the wires while they are operating in a harsh environment.
The systems described herein can be used to collect airborne particles created from factory processes, which will enhance protection of the environment. Also, using the proposed system within closed environments such as hospitals, cars, trains, airplanes, livestock farms, greenhouses, etc. can effectively prevent the airborne dissemination of diseases that typically spread through the air (e.g., common cold, influenza, SARS, MERS, Covid-19, etc.). The methods and systems described herein can also be used for a variety of other applications, including chemical processing plants, fuel processing/distillation towers, environmental pollution reduction, indoor air quality control (including cars, airplanes, and hospitals), portable outdoor personal filters, etc. The proposed methods and systems are also valuable for enhancing energy efficiency associated with phase change heat transfer in chemical plants and buildings, reducing environmental pollution, and controlling indoor air quality.
Effective filtration of airborne particles from the air is an extremely valuable technique for improving the environment and air quality. However, as discussed above, traditional air filtration systems are inefficient in collecting particles due in part to filter clogging and other design issues. The systems and methods described herein are based on experiments conducted with various arrangements of solid structures to improve airborne particle collection efficiency and to avoid clogging of the solid structures with the collected particles. For some of these experiments, the system includes different layers of inclined wires with varying quantities and diameters that are packed into a tube (housing) and used to investigate the effects of solid structure arrangement on airborne particle collection efficiency. These experiments provide a proven basis that guides the design of airborne particle filters, as described herein. While the total surface areas of wires are fixed, wires with smaller diameters and packed into more layers lead to higher smog collection efficiency. Moreover, in at least some embodiments, flexible wires are used because the bending of flexible wires facilitates the transport of collected airborne particles so that the wires do not clog (i.e., become saturated with airborne particles such that further particulate collection is reduced or eliminated). The conducted experiments also studied the optimal shape of wires and the corresponding elastic modulus that leads to the fastest transport. These experiments are described in more detail below.
A first objective of the inventors was to investigate how the arrangement of solid structures affect the airborne particle collection efficiency. When the liquid loss during transport is neglected, the collection rate ({dot over (V)}c) is proportional to the aerodynamic collection efficiency (ηac) and deposition efficiency (ηd), as:
{dot over (V)}c∝ηac·ηd. Equation 1
The aerodynamic collection efficiency (ηac) describes the interaction between the collection system and the particle-laden flow (i.e., fog, smog, etc.). The aerodynamic collection efficiency can be approximated as a function of the solid fraction facing normal to the flow (referred to as shade coefficient, SC), the pressure drop coefficient of the system (Co), and the drag coefficient for an impermeable plate (Cd), as follows:
and Co can be also approximated as a function of shade coefficient (SC), as:
where Cd can be considered as the numerical constant which has secondary effects on ηac as compared with SC and Co.
Both the denominator (Co) and numerator (SC) are a function of SC, and therefore there exists a SC that leads to a largest ηac. Experimental results indicate that using a single layer of mesh, the largest ηac is around 0.2 when SC is around 0.55. Such an ηac of around 0.2 is low, which means a significant portion of airborne droplets cannot be collected or filtered. Moreover, the captured liquid can clog the collector/filter so that the actual collection efficiency is significantly lower, especially on the currently commercialized mesh-like collectors. These results therefore indicate that modifications of collectors are needed to improve the ηac and overcome the clogging issue, and the proposed system is designed to remedy these issues.
Based on the experimental results, some implementations of the proposed system include individually aligned, flexible wires in contrast to the commonly used meshes. The commonly used meshes are horizontally mounted, rigid, and interconnected. Using such meshes, the transport of the collected liquid/particles is made difficult, and severe clogging issues occur in such configurations. By contrast, the bending of flexible wires under gravity and air-drag force (when present) help facilitate the transport of liquid/particles such that the flexible wires do not become clogged with particles, inefficient, or unusable. In alternative embodiments, rigid wires may be used in the proposed system, and the rigid wires can be mounted at an angle to help facilitate liquid/particle transport.
It was also found that the speed of liquid/particle transport along the wires depends on the extent of bending, which essentially depends on the elastic modulus of the wires used. Therefore, inclined wires were tested at various angles relative to a wall, and an optimal inclination that leads to the fastest liquid transport was identified, as discussed herein. By matching the shape of the bent wire with the optimal inclination, the elastic modulus of the wire under specific wind speeds was determined.
In some embodiments, wires having the optimal inclination are mounted at different layers along a tube, which is different from the single-layer mesh approach used in traditional systems. There are two area fractions of solid structures (shade coefficient, SC). One is denoted as SCtotal, which represents the total area fraction of solids that are facing the incoming flow, the other is denoted as SClocal (SClocal=SCtotal/Layers, where Layers represents the number of layers), which represents the area fraction of solids per layer. Thus, Equations 2 and 3 can be re-written, respectively, as:
It can be seen that when the numerator in Equation 4, SCtotal, is maintained as a constant, the denominator in Equation 4 can be decreased by decreasing Co. This is possible by decreasing SClocal via having multiple layers of wires, as shown in Equation 5. Therefore, the collection efficiency ηac can be increased by using multiple layers of wires.
In an illustrative embodiment, the inlet port 120 has a tapered shape in which a circumference of a proximal end of the inlet port 120 is larger than a circumference of a distal end of the inlet port 120. Alternatively, the circumference of the proximal end can be the same as the circumference of the distal end of the inlet port 120. In some embodiments, the proximal end of the inlet port 120 can have a profile of a first shape (e.g., a square, rectangle, circle, oval, triangle, etc.) and the distal end of the inlet port 120 can have a profile of a second shape (e.g., a square, rectangle, circle, oval, triangle, etc.). In alternative embodiments, the profiles of the proximal and distal ends of the inlet port 120 can have the same shape and/or size. In some embodiments, the proximal and distal ends of the inlet port 120 can have the same shape, but different sizes. In the embodiment of
The inlet port 120 directs the air to be cleaned into the first elbow 125. A distal end of the first elbow 125 mates with and mounts to a proximal end of the wire filter 130. As shown, the first elbow 125 transitions the air flow from horizontal (i.e., substantially parallel to a ground/floor surface) to vertical (i.e., substantially perpendicular to the ground/floor surface). As discussed in more detail below, this configuration allows gravity to act upon collected particles such that they collect in the receptacle 140. In the orientation of the embodiment of
The wire filter 130 includes a housing and a plurality of layers of wires mounted within the housing. The plurality of layers of wires are designed to collect airborne particles from the air as the air passes through the wire filter 130. Each of the wires is mounted to an interior surface of the housing of the wire filter 130. The wires can be mounted to the housing using a weld, solder, adhesive, clip, fastener, etc. In some embodiments, the wires are detachable from the housing such that they can be replaced. In such an embodiment, the wires can attach to the housing via a removable fastener, a friction fit male/female connection (e.g., peg and hole, loop and hook, etc.), a magnetic connection, etc. The wires are described in more detail in
A distal end of the wire filter 130 mates with and mounts to a proximal end of the second elbow 135. In an illustrative embodiment, gravity and/or air flow causes collected particles 145 to move from the wire filter 130 into the second elbow 135, from which they are directed into the receptacle 140. The fan 115 is mounted at the distal end of the second elbow 135. In alternative embodiments, the fan 115 may not be used. In such implementations, wind and other natural phenomenon can be used to direct air into and through the system. In alternative embodiments, the humidifier 105, the inlet port 120, the first elbow 125, the second elbow 135, and/or the fan 115 may not be included in the airborne particle removal system 100. In such embodiments, a proximal end of the wire filter can act as the inlet port and the distal end of the wire filter can be directly or indirectly mounted to the receptacle such that collected particles are deposited therein. In other embodiments, the receptacle 140 may not be included.
In an illustrative embodiment, the receptacle 140 can be an enclosed container (i.e., not exposed to the environment) that is designed store accumulated collected particles. The receptacle 140 can be mounted directly or indirectly (i.e., using a duct or other conduit) to the distal end of the second elbow 135 in some embodiments. In one embodiment, the receptacle 140 can include an access panel (e.g., a hinged door, removable panel, plugged hole, drain, etc.) that allows collected particles to be removed therefrom. Alternatively, the receptacle 140 may include a port connected to a vacuum hose that is used to vacuum the collected particles out of the receptacle 140 such that it does not exceed its collection capacity.
The wire filter 200 of
In an illustrative embodiment, all of the wire 215 or at least a portion of the wire 215 can be flexible such that the curvature of the wire 215 changes as airborne particles accumulate thereon. For example, the wire 215 can be made of a semi-flexible material such as a metal, rubber, plastic, polymeric, etc. In some embodiments, only a portion of the wire 215 is flexible. For example, a distal ½ (or ⅓, ¼, ⅕, etc.) of the wire 215 may be flexible and the remainder may be rigid. In another alternative embodiment, the wire 215 may be rigid (in either a curved or straight configuration) and adjustable such that a user can remotely or directly adjust an angle of the wire 215 relative to the wall of the housing 210. The wire 215 can have a circular cross-sectional profile in one embodiment. Alternatively, the cross-sectional profile of the wire 215 can be an inverted V, a square, a rectangle, a triangle, an oval, etc.
The wire 215 can be mounted to the housing 210 using a weld, solder, adhesive, clip, fastener, hinge, friction fit (e.g., a cup mounted to the wall and designed to receive the wire 215), etc. The wire 215 can be permanently or detachably mounted to the housing 210 depending on the implementation. In one embodiment, an actuator or manual control can be used to adjust an angle of the wire 215. For example, an actuator 217 can be optionally mounted to the wire 215 such that movement of the actuator 217 moves the angle of the wire 215 relative to the wall of the housing 210. The actuator 217 can also be used to vibrate or shake the wire 215 to facilitate more rapid release of the collected particles from the wire 215. The actuator 217 can be remotely controlled through a wired or wireless connection. In the case of wireless control, the actuator 217 can include a transceiver to receive the control signal from the remote location. The actuator 217 can also include a power source (e.g., battery), processor, memory, and/or other components to control movement of the wire 215. In an alternative embodiment, an actuator can be used to move the entire system such that all of the wires within the wire filter are moved/vibrated simultaneously.
Alternatively, the wire 215 may be manually adjustable. For example, an extension can extend through the wall of the housing 210 such that a user can manipulate the angle of the wire 215 relative to the wall of the housing 210 by manipulating the extension. The extension can be a portion of the wire, or a lever, handle, or other control mounted to the proximal end of the wire 215. In such an embodiment, the wire 215 can be mounted to the wall of the housing 210 such that the wire 215 pivots relative to the wall. As such, moving the extension in a downward direction would cause the distal end of the wire 215 to rise in elevation and moving the extension in an upward direction would cause the distal end of the wire 215 to drop in elevation (assuming the wire filter 205 is mounted vertically as depicted).
The wire filter 205 of
In some embodiments, at least a portion of the wire 225 can be flexible such that the wire 225 changes from straight to curved as airborne particles are collected thereon. For example, the wire 225 can be made of a semi-flexible material such as a metal, rubber, plastic, etc. In some embodiments, only a portion of the wire 225 is flexible. For example, a distal ½ (or ⅓, ¼, ⅕, etc.) of the wire 225 may be flexible and the remainder may be rigid. In one embodiment, the wire 225 may be adjustable such that a user can remotely or directly adjust an angle of the wire 225 relative to the wall of the housing 220. The angle of the wire 225 can be adjusted using any of the techniques described herein. Similarly, the wire 225 can be mounted to the housing 210 using any of the techniques described herein.
The left portion of
The right portion of
A system similar to that depicted in
To explore the effect of wire elasticity to liquid transport, flexible wires with ˜4 centimeter (cm) in length and 1 millimeter (mm) in diameter were prepared using Polydimethylsiloxane (PDMS) with different base/curing agent mass ratios. The base/curing agent ratios were 5:1, 10:1, and 16.7:1, resulting in elastic moduli of 3.59, 2.61, and 1.21 megapascals (MPa), respectively. The flexible wires were horizontally mounted inside of a tube housing. The shape of the bent flexible wires was recorded by a camera and the maximum bending is depicted herein with reference to
To explore the effect of wire inclination to the speed of liquid transport, rigid, superhydrophilic wires of ˜4 cm in length were used. The wire inclination (angle) with the wall, β, varied from 10° to 80° and various wire diameters were used (0.81, 1.02, 1.30, 1.63, and 2.06 mm). Alternatively, different lengths (e.g., 1 mm, 5 mm, 2 cm, 5 cm, 10 cm, 20 cm, 100 cm, etc.), angles (e.g., 0-90°), and/or diameters (e.g., 1 micron-10 mm) may be used. The speed of liquid transport in fog collection can be quantified as the time taken to observe the first detachment of the liquid droplet from the wire, denoted as onset time (tfirst). The shorter onset time represents the faster liquid transport. As shown in
Wires with lengths of ˜4 cm were packed inside of the transparent tube (inner diameter of 7 cm) to collect droplets. As noted above, all of the wires were inclined at an angle relative to the wall of ˜60°. Therefore, the length of wire perpendicular to the incoming flow was ˜3.5 cm. The collected liquid on the wires eventually dipped down and flowed into a reservoir (or receptacle) of the system. Horizontally mounted meshes with three different diameters (0.41, 0.51, and 0.64 mm) and corresponding shade coefficients (0.54, 0.49, 0.44) were also tested. Wires with eight different diameters (0.41, 0.51, 0.64, 0.81, 1.02, 1.30, 1.63, and 2.06) were mounted at different layers (1, 2, and 4). The number of wires was adjusted to match the shade coefficient of the meshes. The distance between adjacent layers was 2 cm. The specific design parameters, including total (SCtotal) and local (SClocal) shade coefficient, wire diameters (dwire), number of layers (Layers), and number of wires per layers (N) are shown in
In order to find out the optimal state of bending, superhydrophilic wires with various inclination angles with the wall of the housing were examined. A portion of this experiment is depicted in
Building on the fact the wire inclination of 60° showed the fastest liquid transport, airborne droplet collectors/filters with inclination angles of 60° were prepared and tested. Using actual fog droplets (rfog≈5 μm) and individual solid wires (e.g., 0.33 to 2.06 mm) showed that ηd can be approximated as:
where St represents the Stokes number, given as:
where ρliquid, rfog, μair, vo, and dwire represent the liquid density (it should change corresponding to the properties of fog/smog droplets), radius of fog/smog droplets, air viscosity, wind flow speed, and wire diameter, respectively. Combining Equations (1) and (6), one would expect the following relation:
for airborne particle removal systems having design parameters specified in
is less than 0.15, a clear linear relationship (denoted by the dashed line) between the measured {dot over (V)}c and the predicted one can be detected. Fog collectors made with a single-layer mesh (hollow symbols) collected much less liquid than those made with individual wires, although the shade coefficient is similar. For example, the wires with 0.51 mm in diameter mounted at four layers (26 wires per layer) collected 200% more liquid than the corresponding single-layer mesh with the same shade coefficient. Moreover, a smaller wire diameter leads to a larger collection efficiency.
The clogging issue due to poor liquid transport is regarded as the major reason leading to the deterioration of the fog collection performance using a single-layer mesh. When
is more than 0.15, the measured {dot over (V)}c reached a plateau and cannot increase with the increase in the prediction. It was speculated that this deviation is mainly related to ηac rather than the deposition efficiency,
especially for wires packed at multiple wires. Therefore,
is considered to remain unchanged and an investigation of ηac was conducted. It was found that re-arranging Equation (8) as
can be regarded as the measured aerodynamic collection efficiency.
with respect to the predicted ηac to investigate the effects of design parameters to ηac in accordance with an illustrative embodiment. More specifically,
plotted with respect to the aerodynamic collection efficiency (ηac). As shown, a clear linear relationship for the date points in between the solid line and the black-dotted line can be detected, where the solid and the black-dotted lines represent the ±10% deviation from the linear line (dashed line). The data points below the lines represent the under-performed fog collectors, including the collectors made with single-layer mesh and the individual wires that are packed at multiple layers.
In one embodiment, the airborne particle removal system includes a plurality of tubes (or individual housings) that are formed within a main housing. Each of the plurality of tubes includes a plurality of layers of wires that are used to collect airborne particles from air that passes through the main housing.
Thus, described herein are airborne particle removal systems and methods to design such systems to efficiently capture airborne particles. Currently, the commercially available collectors suffer from low collection efficiency, mainly because (1) the remaining liquid on the solid structures blocked the system permeability (clogging issues) and (2) the arrangement of solid structures are not designed with high aerodynamic collection efficiency. To address the first problem, individually aligned, flexible wires are used to enhance the transport of the captured liquid to avoid the clogging issues. Flexible wires can bend under gravity and a wind flow, and it was found that the inclination angle of a wire with the wall at ˜60° gives the fastest liquid transport (shortest time taken to allow a detachment of a droplet from a wire). The experiments described herein also visualized the bending of wires with various elastic modulus under various wind speeds. This visualization provides a guideline for choosing the appropriate wire elasticity to achieve the wire inclination of ˜60° under a given wind speed.
The second problem can be solved by reducing the pressure drop coefficient of the collector/filter, via distributing the wires from one layer onto multiple layers. Specifically, individually aligned, inclined (˜60°), superhydrophilic wires with various wire diameters were mounted within a tube at various layers (see detailed design parameters in
The housing used to form the systems described herein can be formed from a plastic, metal, rubber, or other material. Similarly, the wires can be made from plastic, rubber, metal, etc. In some embodiments, the wires are made from used aluminum or Polydimethylsiloxane (PDMS). The specific wettability of the wires can be determined by considering the higher or optimal adhesion strength between the liquid droplets and the wires. The wires can be coated with a hydrophilic coating or a superhydrophilic coating in some embodiments to facilitate particle collection. The wires can also be coated with an oleophilic coating or a superoleophilic coating in some embodiments to facilitate particle collection. In some embodiments, the wires are decorated with functional particles such as nanoparticles that help facilitate the collection and/or release of particles. Additionally, coupling the flexible wires with nanostructures can be used to help the wires resist bio/chemical fouling in various harsh environments.
In one embodiment, a computing system can be used to perform any of the operations described herein to generate a design for an optimal wire filter based on filter size, wind speed, application, etc. The computing system can include a processor, memory, user interface, and transceiver. The memory can store the operations described herein as computer-readable instructions. The processor can access the computer-readable instructions from the memory and execute them to perform the operations such that a wire filter design is generated. Data and preferences can be input through the user interface by a user, and the transceiver is used for communication with other local and remote computing systems.
Although the embodiments described herein have referenced filtration of air, it is to be understood that the proposed methods and systems are not so limited. The proposed methods and systems can similarly be used to remove particles from other types of gases such as natural gas, propane, methane gas, etc.
The word “illustrative” is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “illustrative” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Further, for the purposes of this disclosure and unless otherwise specified, “a” or “an” means “one or more.”
The foregoing description of illustrative embodiments of the invention has been presented for purposes of illustration and of description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and as practical applications of the invention to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.
The present application claims the priority benefit of U.S. Provisional Patent App. No. 62/833,885 filed on Apr. 15, 2019, the entire disclosure of which is incorporated by reference herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2020/028310 | 4/15/2020 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62833885 | Apr 2019 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2019/056463 | Oct 2019 | US |
| Child | 17602175 | US |
