INHIBITING OPEN CHANNEL FLOW IN WATER TUBES OF AN ULTRAVIOLET FLUID DISINFECTION SYSTEM

An ultraviolet-based disinfection system is presented here. The system includes a fluid flow tube configured to accommodate fluid to be treated, and an ultraviolet energy source adjacent to the fluid flow tube. The ultraviolet energy source is configured to emit ultraviolet energy for treating fluid flowing within the fluid flow tube. The fluid flow tube is configured to inhibit open channel flow conditions and to promote plug flow conditions.

DETAILED DESCRIPTION

For the sake of brevity, conventional techniques related to system control, fluid dynamics, ultraviolet-based disinfection, water treatment, and other functional aspects of the systems (and the individual operating components of the systems) may not be described in detail herein. Furthermore, connecting lines shown in any figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in an embodiment of the subject matter.

FIG. 1is a simplified schematic representation of an exemplary embodiment of a fluid disinfection system100that utilizes ultraviolet light technology to disinfect water flowing through the system100. Although this description assumes that the fluid under treatment is water, the disinfection system and technology disclosed herein could be modified to treat and disinfect other fluids and liquids if so desired. For the sake of generality, the system100is depicted as a multistage embodiment in that the system100includes a first stage102, a second stage104, and so on. In practice, the system100may include only one stage (i.e., the first stage102by itself), only two stages (i.e., only the first stage102in series with the second stage104), or any number of stages in series with one another. The first stage102receives water to be treated (represented by the “IN” label). The final stage106emits treated water (represented by the “OUT” label). In a multistage implementation as depicted inFIG. 1, the output of the first stage102serves as the input to the second stage104, the output of the second stage104serves as the input to the final stage106, and so on. In this regard, water flows through the system100in series through the various stages. In practice, each stage of the system100may be similarly configured in accordance with the following description. Notably, the system100does not utilize an open channel flow scheme. Moreover, the system100need not maintain the input and/or output water levels at any defined height. In this regard, the system100need not include a weir at the outlet side, or anything functionally equivalent to a weir.

FIG. 2is a simplified perspective view of a stage112of the system100, andFIG. 3is a simplified schematic representation of a cross-sectional view through a stage of the system100.FIG. 2has been simplified to depict a typical arrangement of water flow tubes110, which may be arranged along the major longitudinal axis of the stage112. The number, shape, size, and arrangement of tubes110within any given stage may vary from one embodiment to another. For ease of illustration and description, the embodiment depicted inFIG. 2andFIG. 3includes twelve tubes110arranged in a three-by-four configuration. In a multistage implementation, each tube continues from one stage to another. In other words, each tube110in the first stage102is coupled to a respective and corresponding tube110in the second stage104, and so on. For example, the tube110a(depicted in the top left position inFIG. 3) has a corresponding tube110ain each of the stages and in the same relative position.

Referring toFIG. 3, the stage also includes a plurality of ultraviolet lamp fixtures116that are designed to emit ultraviolet radiation to disinfect water as it flows through the tubes110. InFIG. 3, each of the larger (shaded) circles represents a flow tube110, and each of the smaller circles represents a lamp fixture116(i.e., a UV disinfecting lamp). Although not required in all embodiments, the exemplary implementation illustrated inFIG. 3has the lamp fixtures116configured and arranged in lamp racks118that flank the tubes110. In practice, a stage in the system100may have any number of lamp racks118, and each lamp rack118may include any number of lamp fixtures116. In the illustrated embodiment, the lamp fixtures116are substantially aligned with the tubes110. In this regard, all but two of the rows inFIG. 3includes three tubes110and four lamp fixtures116. The uppermost and the lowermost rows inFIG. 3include four lamp fixtures116, but no tubes110. Consequently, each tube110is surrounded by six neighboring lamp fixtures116, two of which are immediately adjacent to and flanking the tube110.

Although not separately shown inFIG. 2, the lamp fixtures116in the system100are preferably arranged in a longitudinal configuration such that they run substantially parallel to the tubes110. In alternative embodiments, however, one or more of the lamp fixtures116could be perpendicularly arranged relative to the major longitudinal axis of the tubes110. In yet other embodiments, the lamp fixtures116and the tubes110need not be orthogonally arranged relative to one another. Moreover, any combination of parallel, perpendicular, and/or non-orthogonal arrangements could be utilized if so desired.

FIG. 4is a simplified side view of an exemplary embodiment of a stage200suitable for use in a UV-based fluid disinfection system, such as the water disinfection system described above with reference toFIGS. 1-3.FIG. 5is an end view of the stage200as viewed from line5-5inFIG. 4, andFIG. 6is an end view of the stage200as viewed from line6-6inFIG. 4. The stage200includes a housing202having a fluid entry side204and a fluid exit side206.FIG. 5corresponds to an elevation view of the fluid entry side204, andFIG. 6corresponds to an elevation view of the fluid exit side206. The housing202includes a plurality of fluid flow tubes210located and maintained therein (as described previously with reference toFIGS. 1-3), wherein the fluid flow tubes210are configured to accommodate the fluid to be treated, e.g., water. Although not always required, the illustrated embodiment includes sixteen fluid flow tubes210that are generally oriented in a four-by-four arrangement. In this regard, there are four “levels” of tubes (horizontally aligned inFIG. 5andFIG. 6). Notably, the fluid flow tubes210are angled or tilted within the housing202such that their input ends are lower than their output ends. The angled pitch of the fluid flow tubes210is discernible inFIG. 4, which shows the fluid flow tubes210in dashed lines.

Each fluid flow tube210is accessible from the fluid entry side204and from the fluid exit side206. Thus, water to be treated can enter the fluid flow tubes210via the fluid entry side204, and water that has been treated can exit the fluid flow tubes210via the fluid exit side206. For the embodiment depicted inFIGS. 4-6, the inlet end of each fluid flow tube210terminates at or near the fluid entry side204, and the outlet end of each fluid flow tube210terminates at or near the fluid exit side206. As described above with reference toFIGS. 1-3, the stage200includes at least one UV energy source adjacent to each fluid flow tube210, wherein the UV energy source is configured to emit UV energy for treating the fluid as it flows within the fluid flow tubes210between the fluid entry side204and the fluid exit side206.

Although not shown in the figures, the fluid entry side204of the stage200may include additional features, structures, or components that are designed to deliver and accommodate the incoming fluid to be treated. For example, the fluid entry side204of the stage200may include or cooperate with a tank, an input reservoir, a fluid conduit, a pump system, or the like. For this particular example, as flow increases at the inlet side, the water level increases because the head loss increases (higher flow requires more energy to pass fluid through a fixed tube size). As the water level increases, the fluid flow tubes210begin to fill from the lowermost row (level) to higher rows. Referring toFIGS. 4-6, the lower level of fluid flow tubes210dwill be the first to flow, followed by the second level of fluid flow tubes210cand the third level of fluid flow tubes210b.The upper level of fluid flow tubes210awill be the last to flow.

Some conventional UV water treatment systems utilize an outlet tank having a weir that maintains the water level at a desired height to ensure that all of the tubes remain filled during operation. The downside to that approach is that, during low flow conditions, there may not be enough water flowing through the tubes (there could be a minimum flow rate that the system is designed for, to sustain turbulent flow, which in turn results in a self-cleaning action). With a weir system at the output side, the desired minimum flow rate may not always be achieved.

In practice, the system100need not utilize an outlet weir, and need not maintain a specified water level. Instead, the system100can be operated such that the water level is self-regulated based on the water pressure and inlet flow rate. As the inlet flow rate drops, the pressure required to push the water through the system100drops. This results in a decrease in the inlet water level. Accordingly, some of the upper fluid flow tubes210may be void of water, while only the lower fluid flow tubes210remain full and flowing. In other words, the water level in the stage200can vary such that certain fluid flow tubes210may be empty or not completely full of water at any given time.

The exemplary embodiments described here contemplate the scenario where a tube is not completely full and, therefore, is exhibiting an open channel flow condition (as depicted inFIG. 7).FIG. 7depicts a relatively level or horizontally oriented tube300having water302flowing through it. The water302does not completely fill the tube300and, therefore, the flow of water302through the tube300resembles an open channel. The techniques and technology presented here are intended to inhibit or prevent channel flow conditions within the fluid flow tubes210. To this end, the fluid flow tubes210are suitably configured to inhibit open channel flow conditions and to promote plug flow conditions (as depicted inFIG. 8).FIG. 8depicts an upwardly tilted and angled fluid flow tube310, wherein the inlet end312of the fluid flow tube310is lower than the outlet end314of the fluid flow tube310. Thus, at least a portion of the fluid flow tube310exhibits a plug flow condition, where the water316has completely filled the fluid flow tube310.

As shown inFIG. 4andFIG. 8, the fluid flow tubes210,310are arranged and maintained in position within the housing202such that the fluid flow tubes210,310have a predetermined amount of rise associated therewith (from the inlet end to the outlet end). In other words, there is a height differential wherein the outlet end of each fluid flow tube210,310is higher in elevation than the inlet end. The rise in the fluid flow tubes210,310prevents water from flowing through any given tube unless there is sufficient pressure and flow energy to completely fill at least a primary section of the tube and, therefore, to establish a plug flow condition.

In practice, the amount of rise for a given fluid flow tube210,310must be greater than the diameter of that tube. This minimum rise ensures that a plug flow state will be established within the fluid flow tube210,310. In this regard,FIG. 8depicts a state where the fluid flow tube310has not yet reached a total plug flow state. The rise of the fluid flow tube310inhibits open channel flow for a period of time. It should be appreciated that a typical operating environment will provide more than enough pressure and energy at the inlet end312to overcome the rise in the fluid flow tube310and gravitational forces associated with “pushing” the water uphill. In operation, water will remain trapped inside of a partially filled fluid flow tube310until the point where the fluid flow tube310becomes completely filled. At that time, the water in the fluid flow tube310will have reached the outlet end314, where it can be discharged as usual under plug flow conditions. The predetermined rise can be achieved by tilting the entire length of the fluid flow tubes210within the housing202(seeFIG. 4), or by tilting only an exit section of an otherwise horizontally oriented fluid flow tube, such that the upwardly tilted exit section terminates at or near the fluid exit side206of the housing202(seeFIG. 9andFIG. 10).

The embodiment depicted inFIG. 4utilizes sixteen fluid flow tubes210, each of which is maintained in a position within the housing that results in the same predetermined amount of rise (within practical tolerances). In alternative embodiments, however, different amounts of rise may be utilized for different fluid flow tubes, for different rows of tubes, or the like. In yet other embodiments, some of the fluid flow tubes may have little to no rise, while others have some amount of rise.

FIG. 9is a simplified side view of another embodiment of a stage400suitable for use in a UV-based fluid disinfection system. The stage400may include a number of features and functionality that have already been described above in the context of the system100and the stage200; common features, functions, and aspects will not be redundantly described in detail here in the context of the stage400.

As depicted inFIG. 9, the stage400includes a plurality of fluid flow tubes410located within a housing402. Each fluid flow tube410is characterized by a primary section450and an upwardly tilted exit section452that is fluidly coupled to the primary section450(for simplicity and clarity, these sections are only labeled for the bottom fluid flow tube410inFIG. 9). Although not shown inFIG. 9, a fluid flow tube410may also include one or more additional sections, e.g., a transition section fluidly coupled between the primary section450and the upwardly tilted exit section452.

The primary section450includes or defines the inlet end412of the fluid flow tube410, and the tilted exit section452includes or defines the outlet end414of the fluid flow tube410. The outlet end414terminates at an exit opening454of the fluid flow tube410; the treated water flows out of the exit opening454. In certain embodiments, the exit opening454is positioned at a height that is above the height of the primary section450. In this regard, the exit opening454exhibits a rise relative to the level of the primary section450and, therefore, relative to the inlet end412of the fluid flow tube410. As mentioned above, the rise associated with the upwardly tilted exit section452is configured to inhibit open channel flow conditions and to promote plug flow conditions within the fluid flow tube410.

The fluid flow tubes410shown inFIG. 9are contained within the housing402. In alternative embodiments, at least a portion of the upwardly tilted exit sections protrude from the housing. One alternative configuration of this type is shown inFIG. 10, which illustrates a stage500having a housing502and a plurality of fluid flow tubes510. The stage500may include a number of features and functionality that have already been described above in the context of the system100and the stages200,400; common features, functions, and aspects will not be redundantly described in detail here in the context of the stage500.

As depicted inFIG. 10, each fluid flow tube510includes a primary section550and an upwardly tilted exit section552that is fluidly coupled to the primary section550(for simplicity and clarity, these sections are only labeled for the bottom fluid flow tube510inFIG. 10). In contrast to the configuration shown inFIG. 9, the upwardly tilted exit section552is located outside of the housing502. In alternative embodiments, one segment of the upwardly tilted exit section552is located within the housing502, and the terminating segment of the upwardly tilted exit section552extends outside of the housing502(this alternative configuration is not shown in the figures). Thus, the primary sections550of the fluid flow tubes510are nominally horizontal and level within the confines of the housing502. The upwardly tilted exit sections552, however, provide a predetermined amount of rise from the inlet ends512to the outlet ends514of the fluid flow tubes510, which inhibits open channel flow conditions and promotes plug flow conditions in the manner described previously.

In lieu of (or in addition to) tilted tubes or tilted exit sections, a stage of a UV-based fluid disinfection system may include a suitably configured fluid outlet structure that is designed to inhibit open channel flow conditions and is designed to promote plug flow conditions. In this regard,FIG. 11is a perspective view of an exemplary embodiment of a fluid outlet structure600suitable for use with a stage602of a UV-based fluid disinfection system. The stage602may include a number of features and functionality that have already been described above in the context of the system100and the stages200,400,500; common features, functions, and aspects will not be redundantly described in detail here in the context of the stage602.

For simplicity and clarity,FIG. 6only depicts a fluid exit side604of the housing606of the stage602. The exit openings608of the fluid flow tubes terminate at (or extend from) the fluid exit side604. Only the uppermost row of exit openings608are numbered inFIG. 11; there are sixteen fluid flow tubes and, therefore, sixteen exit openings608. The fluid flow tubes, which are hidden from view inFIG. 11, may be level and horizontal within the housing606, they may be tilted as shown inFIG. 4, or they may have a level primary section coupled to a tilted exit section as shown inFIG. 9. In some embodiments, the stage602may include any combination of the various types of fluid flow tubes described here.

The fluid outlet structure600is located at the fluid exit side604of the housing606. In certain embodiments, the fluid outlet structure600is attached to (or is integrated with) the fluid exit side604. The fluid outlet structure600is arranged such that it is in fluid communication with the fluid flow tubes, and such that it promotes plug flow conditions within the fluid flow tubes. In accordance with the embodiment depicted inFIG. 11, the fluid outlet structure600includes a plurality of fluid retention troughs612, each coupled to the fluid exit side604. Each fluid retention trough612may be assigned to one or more of the fluid flow tubes. The illustrated embodiment includes fluid flow tubes arranged and maintained within the housing606at a plurality of different levels (heights), wherein a respective one of the fluid retention troughs612is assigned to each level. As shown inFIG. 11, one fluid retention trough612serves as a collection basin for the lowermost row of exit openings608, another fluid retention trough612serves as a collection basin for the uppermost row of exit openings608, and so on. In alternative configurations, there could be one fluid retention trough612per fluid flow tube, or there could be any number of fluid flow tubes assigned to a given fluid retention trough612.

Each fluid retention trough612functions to collect the treated water that flows out of the fluid flow tubes. In this regard, each fluid retention trough612is shaped and sized to inhibit open channel flow within the fluid flow tubes. Thus, each fluid retention trough612has an overflow edge616that is positioned at a height that promotes plug flow conditions within the fluid flow tubes. During operation, the treated water pools within the fluid retention troughs612, allowing the water to fill the fluid flow tubes to achieve the plug flow conditions. Eventually, the level of the discharged water rises above the overflow edges616, and the treated water spills over (into an output tank, a fluid conduit, or the like).

FIG. 12is a perspective view of another embodiment of a fluid outlet structure700suitable for use with a stage702of a UV-based fluid disinfection system. The stage702may include a number of features and functionality that have already been described above in the context of the system100and the stages200,400,500,602; common features, functions, and aspects will not be redundantly described in detail here in the context of the stage702.

For simplicity and clarity,FIG. 7only depicts a fluid exit side704of the housing706of the stage702. The fluid flow tubes are hidden from view within the housing706. The fluid flow tubes may be level and horizontal within the housing706, they may be tilted as shown inFIG. 4, or they may have a level primary section coupled to a tilted exit section as shown inFIG. 9. In some embodiments, the stage702may include any combination of the various types of fluid flow tubes described here.

The fluid outlet structure700is located at the fluid exit side704of the housing706. In certain embodiments, the fluid outlet structure700includes a plurality of upwardly tilted or curved exit sections710associated with the fluid flow tubes. In certain embodiments, the number of exit sections710equals the number of fluid flow tubes, such that each exit section710is fluidly coupled to a respective one of the fluid flow tubes (as depicted inFIG. 12). In this regard, each exit section710may represent an extension of a fluid flow tube maintained within the housing706.

Although not always required, the illustrated embodiment employs a fluid outlet structure700that is suitably configured such that each of the exit sections710terminates at a common height. Notably, this common height is located above the height of the uppermost fluid flow tube. This feature is preferred to ensure that all of the fluid flow tubes exhibit plug flow conditions as the water passes through the housing706.

The particular embodiment shown inFIG. 12utilizes L-shaped exit sections710. The horizontal segment of each L-shaped exit section710transitions to a vertical segment, which in turn rises to the common fluid outlet height. In accordance with alternative embodiments, the fluid outlet structure700may include angled or curved segments that serve as fluid conduits to reach the desired fluid outlet height. In this regard, the fluid outlet structure700may resemble the outlet configuration depicted inFIG. 10.

The various embodiments presented here promote plug flow conditions within the primary sections of the fluid flow tubes and, conversely, inhibit open channel flow conditions within the fluid flow tubes. Plug flow is desirable in UV-based water disinfection systems because the water travels through the fluid flow tubes in a relatively uniform flow rate/velocity. A stable and consistent water flow rate ensures that the UV dosage is even and consistent within each stage of the disinfection system.