Patent Application
20100314551
The present invention relates to the treatment of water and other fluids using ultraviolet (UV) radiation.
Liquids, including water, are commonly used for many domestic and industrial purposes such as drinking, food preparation, manufacturing, processing of chemicals, and cleansing. Often it is necessary to purify a liquid prior to its use. Filters such as ceramic filters are typically used to remove particulate and chemical impurities from liquids. In addition, a liquid can be exposed to UV radiation to neutralize microorganisms and deleterious pathogens that may be present in the liquid. Exposure to short wavelength (e.g., 200 nm-320 nm) UV radiation can have a germicidal effect, i.e., the radiation can disrupt the DNA of many cellular microorganisms—thereby virtually destroying them or rendering them substantially harmless. The exposure to UV radiation can also substantially prohibit the growth and/or reproduction of microorganisms that may be present in the liquid.
Some known methods of purifying a liquid using UV radiation require the liquid to be stored in a container such as a small tank or a bottle. The liquid in the container is generally still or may flow at a slow rate due to actions such as a drip from a filter or sipping. A UV source such as a light-emitting diode (LED) or UV lamp radiates a predetermined amount of UV energy toward the liquid. After exposure to the UV energy for a pre-determined duration, the liquid in the container is considered purified. These purification systems, however, may not be effective when used to purify flowing liquids.
In many applications, the liquid used is not held steady in a container. Instead, it may flow at a high rate through various components of the application system such as chambers, filters, tubes, and pipes. Moreover, the flow rate of the liquid can change over time as the amount of liquid required by the application changes. The flow-rate change can also be unpredictable. Indeed, a component of the application may be replaced with a component of a different size or shape, causing the flow rate of the liquid to change. Finally, even when the flow rate of the liquid does not change substantially, the degree of contamination of the liquid may change, requiring a different level of UV radiation energy (i.e., target fluence) for effective purification of the liquid.
The germicidal effect of UV radiation on flowing liquid depends on the energy density of the UV radiation, i.e., the fluence of radiation, which in turn is related to the power of the radiation and the duration of exposure. The radiation power depends on the power supplied to the source of radiation, and the duration of exposure depends on the flow rate of the liquid. To illustrate, Table 1 shows the required power of a UV LED to purify water flowing at different rates and in tube of different sizes. The values shown in Table 1 assume that the flowing water would be exposed to UV radiation energy of approximately 40 mJ/cm2, which is usually sufficient to substantially purify water. It can be seen from Table 1 that as the flow rate increases, greater LED power is required. Greater LED power is also required as the volume of the chamber in which the water is purified increases. The calculations in the table assume a water UV transparency at 254 nm wavelength of about 98% over a 10 cm distance. If the transparency is lower, either the LED power needs to be increased, the water flow decreased, or the length of the chamber adjusted so that the total dose received by the water contaminants is sufficient for purification. The values in Table 1 are offered only as an example, and it is understood that they are in no way constraining this invention to a certain geometry, flow rate, chamber dimensions or shape nor water quality.
Purification systems radiating a constant amount of energy may not produce a sufficient germicidal effect as the purification parameters (e.g., flow rate, target fluence, chamber dimensions, degree of contamination) change, requiring a greater amount of UV energy. On the other hand, in a purification system that radiates high amounts of UV energy when the system is turned on, a significant amount of power supplied to the system may be wasted. Thus, there is a need for improved systems and methods for purifying flowing liquids.
In various embodiments of the present invention, a flowing liquid is exposed to UV radiation sufficient to have a desired germicidal effect, thereby substantially purifying the liquid while avoiding waste of energy consumed by the UV radiation source. This is achieved, in part, by using one or more purification parameters such as the target fluence, the dimensions of the purification chamber, and/or the flow rate of the fluid to determine the input power required by a UV source. By regulating the UV source according to the determined power, UV radiation sufficient to cause a germicidal effect, thereby substantially purifying the flowing liquid, can be produced. If the purification parameters change (e.g., the flow rate decreases) the updated parameters can be used to recalculate the power required by the UV source. Thus, by not having to produce the maximum UV radiation at all times excess UV radiation, and hence, excess power consumption by the UV source can be avoided while ensuring that the flowing liquid is substantially purified. The purification parameters can be provided to the purification system by a user. Alternatively, the system can include sensors to automatically determine some purification parameters. As used herein, the term “substantially” generally means±10%, and in some embodiments, ±5%.
Accordingly, in one aspect, the invention relates to method of germicidally treating a flowing fluid. In various embodiments, the method comprises the steps of obtaining one or more purification parameters associated with flow of the fluid, and based on the parameter(s), exposing the flowing fluid to UV radiation at a target fluence sufficient to achieve a desired germicidal effect in the fluid. The exposing step may comprise determining, based on the parameter(s), the intensity of UV radiation sufficient to achieve the target fluence, and regulating a UV radiation source in response to the determined intensity. For example, the target fluence may be minimally sufficient to achieve the desired germicidal effect.
In various embodiments, the exposing step is accomplished using at least one LED radiating into the flowing fluid. Proper exposure may be achieved in various ways. In one approach, the power level of the LED(s) is adjusted. Alternatively, the exposing step may be accomplished using a plurality of LEDs radiating into the flowing fluid, and proper exposure is achieved by activating a sufficient number of the LEDs.
The purification parameter may be one or more of the fluid flow rate, the target fluence, an exposure time, and/or at least one dimension of a chamber through which the fluid flows. The parameter(s) may be obtained via a user interface, and/or may involve sensing the fluid flow rate using a sensor.
In another aspect, the invention relates to a system for germicidally treating a flowing fluid. In various embodiments, the system comprises a source of UV radiation directed into the flow; a computation unit for determining, based on at least one flow parameter, a configuration of the UV source to achieve a desired germicidal effect in the fluid; and a mechanism for controlling the UV source in response to the determined configuration. The configuration of the UV source may be determined, for example, by computing a UV intensity sufficient to achieve a desired germicidal effect in the fluid. The system may contain a mechanism, such as a user interface (e.g., touch pad) for obtaining the flow parameter(s). The flow parameter(s) may be or include the flow rate, in which case the mechanism for obtaining the flow rate may be a flow sensor—e.g., a time-of-flight sensor and/or a pressure sensor.
The UV source may comprise at least one UV LED oriented to radiate into the flowing fluid. In various embodiments, the controlling mechanism adjusts a power level of the UV LED(s), which may, for example, be positioned on an interior wall of a chamber through which the fluid flows or within flow path of the fluid. The UV LED(s) may be sealed by a UV-transparent material. In some embodiments, the source of UV radiation comprises a plurality of LEDs, the configuration comprises a group of LEDs to be activated, and the controlling mechanism activates the LEDs in the group. The configuration may further comprise a power level of each LED in the group, in which case the controlling mechanism may adjust the power supplied to each LED in the group.
In some embodiments, the system includes a sensor for sensing fluid flow and a switching mechanism, responsive to the sensor, for activating the UV source only when fluid flow is sensed.
In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present invention are described with reference to the following drawings, in which:
With reference to the representative application system 100 shown in
Depending upon a desired rate of flow of the purified liquid, a valve 106 can be adjusted to regulate the flow of the liquid into the conventional filter 102 and the purification system 110. As explained below, the purification system 110 uses the liquid's flow rate and other parameters to adjust the UV radiation to which the liquid is exposed.
The purification system 200 also includes a purification chamber 210 containing five UV LEDs 212, 214, 216, 218, 220 affixed to the inner surface 224 of the chamber 210. The UV LEDs 212, 214, 216, 218, 220 are oriented to provide UV radiation to the liquid flowing through the chamber 210. Although
The parameters input through the touch-pad keyboard 204 are received by a computation unit 230. If the degree of contamination of the liquid is provided, the computation unit 230 can determine the target fluence, i.e., the fluence required to substantially purify the liquid. Alternatively, as described above, the target fluence can be directly supplied by the user. The liquid entering through the inlet 226 and exiting through the outlet 228 of the chamber 210 is exposed to UV radiation from the UV LEDs 212, 214, 216, 218, 220 for the duration of time it takes the liquid to pass through the chamber 210. The computation unit 230 computes the average passage time using the (sensed or user-provided) flow rate and the dimensions of the chamber 210. Based on the target fluence (computed or supplied as described above) and the time for which the liquid should be exposed to UV radiation from UV LEDs 212, 214, 216, 218, 220 (i.e., the average passage time), the computation unit 230 determines the intensity of UV radiation from the LEDs 212, 214, 216, 218, 220 required to cause an adequate germicidal effect on the liquid flowing through the chamber 210.
The intensity of light and/or UV radiation emitted from an LED depends on the current flowing through the LED, and is thus related to the power supplied to the LED. Therefore, the computation unit 230 can also determine total power that must be delivered to the LEDs to provide the required radiation intensity. An LED driver 240 can supply the determined power (i.e., current) to the various LEDs. All LEDs may receive the same amount of power, or different LEDs may receive different amounts of power. In addition, the driver may choose to turn on only some LEDs (e.g., LEDs 212, 220) and may choose to turn off the other LEDs 214, 216, 218 in order to achieve the target fluence.
In the purification system 300 illustrated in
Using the determined flow rate of the liquid and the other parameters, the computation unit 330 determines the power that must be supplied to each LED 312 in the grid 314 so as to substantially purify the liquid, as described above with reference to
Another system and method of determining the flow rate of a liquid is illustrated with reference to
The purification system shown in
The UV LED 430 desirably has a high wall-plug efficiency, i.e., the fraction of the total electric power delivered to the UV LED 430 that is converted into UV radiation is greater than 10%. The UV LED 430 also has an operating lifetime of approximately 5,000 hours. Such UV LEDs can be constructed by growing pseudomorphic layers of AlxGa1-xN on AlN single-crystal substrates as described, for example, in U.S. patent application Ser. No. 12/020,006, filed on Jan. 25, 2008. High-efficiency UV LEDs are described in U.S. patent application Ser. Ser. No. 10/910,162, filed on Aug. 3, 2004. These applications are incorporated herein by reference in their entireties.
As the UV LED 430 has a long life and because it is hermetically sealed, it may have to be replaced less frequently than UV LEDs in other applications. Due to the relatively high efficiency of the UV LED 430, the cost of operating the purification system 400 may also be relatively small. It should be understood, however, that high efficiency, long life, and hermetic sealing are not essential features of the present invention, and that UV LEDs not having one or more of these properties (e.g., an unsealed UV LED having a wall-plug efficiency less than 10% (e.g., 2%) and a relatively short lifetime (e.g., 2,000 hours)) can also be used.
The UV LED 430 has a Lambertian output profile, i.e., the energy density of the UV radiation 434 emitted by the LED is substantially uniform across the cross-sectional area 436 of diameter d at a distance L from the LED. As a result, liquid flowing through various locations 442, 444, 446, 448 in the cross-section 436 is exposed to approximately the same intensity of UV radiation or fluence. Again, a Lambertian output profile is a beneficial but not an essential feature, and UV LEDs having non-uniform output profiles can also be used in other embodiments of the present invention.
As described above, the computation unit 450 determines the power required by the UV LED 430 to produce fluence having adequate germicidal effect within the portion 418 of length L of the chamber 410. The computation unit 450 can be configured to determine a minimum required power such that the produced fluence is minimally sufficient. The driver 460 regulates the UV LED 430 according to the computed power.
Although the system 400 uses one UV LED 430, it should be understood that other configurations of UV LEDs such as LEDs affixed to the inner surface of the chamber 410 or affixed, for example, to a circular grid inside the chamber 410 are also within the scope of the invention. As explained with reference to
According to one embodiment of the invention, a safety mechanism is added that acts if not enough UV radiation is provided in order to achieve purification. The safety mechanism comprises, for example, a UV detector that measures the output UV power and compares it against the UV power needed according to the purification parameters. If the measured UV power is lower than that determined as needed by the system, a safety shut-off lock and/or an alarm is activated.
Although the present invention has been described with reference to specific details, it is not intended that such details should be regarded as limitations upon the scope of the invention, except as and to the extent that they are included in the accompanying claims.
This application claims priority to and the benefit of, and incorporates herein by reference in its entirety, U.S. Provisional Patent Application No. 61/186,203, which was filed on Jun. 11, 2009.
| Number | Date | Country | |
|---|---|---|---|
| 61186203 | Jun 2009 | US |
