Increasing turbulent mixing in a UV system

Turbulent mixing in a UV system is increased by positioning one or more ring-shaped devices, such as washers, at one or more predetermined locations on the exterior surface of each lamp unit in the system. The washers may have the same or different diameters. Turbulent mixing is also increased by retaining the upstream end of each lamp unit in a ring-shaped device, alone or in combination with washers positioned on each lamp unit exterior surface as described above.

FIELD OF THE INVENTION 
This invention relates to systems that use ultraviolet (UV) light to 
control organisms and more particularly to the dosage of UV radiation that 
the organism is subjected to in passing through the system. 
DESCRIPTION OF THE PRIOR ART 
As is well known, UV light may be used to disinfect water including 
wastewater. The UV light inhibits the replication of any pathogenic 
microorganisms in the water or wastewater. Recently, UV light has been 
proposed for controlling zebra and related mussels present in the lake and 
river water used by power plants. 
The key to using UV light to control an organism, be it a microorganism or 
mussel, is that the organism receive an adequate dose of UV light so that 
it will be unable to survive. The dose of radiation received by an 
organism is defined by: 
EQU Dose=Intensity.times.Time. 
wherein Time is the time of exposure of a given organism to the UV light in 
seconds, Intensity is measured in W/cm.sup.2, and Dose is measured in 
W.multidot.sec/cm.sup.2. For a given UV lamp power output, the intensity 
will diminish with increasing radial distance from the lamp. 
One example of using UV light to control an organism is the wastewater 
disinfection system described in U.S. Pat. No. 5,019,256 ("the '256 
Patent") which issued on May 28, 1991 and is assigned to an assignee who 
is related to the assignee of the present invention. The system has a 
frame on which are mounted one or more modular racks. Each rack has an 
array of two or more lamp units. Each lamp unit consists of a UV lamp 
surrounded by a quartz sleeve. Each lamp has contacts for connection to a 
source of electrical power only at one end of the lamp and the quartz 
sleeve is closed at one end. 
The lamp units are assembled so that the closed end of the quartz sleeve is 
at end of the lamp not having the electrical power connection contacts. 
Each rack has two opposed legs. One of the legs has two or more swivel 
sleeves mounted thereon. Each swivel sleeve is associated with a 
respective one of the lamp units. The lamp units are mounted on the rack 
so that the closed end of the quartz sleeve slides into the swivel sleeve. 
A portion of the closed end of the quartz sleeve resides in the swivel 
sleeve. 
In a UV system such as that described '256 Patent, the intensity is at a 
minimum at point 2 in FIG. 7c. If an organism remains near the centerline 
when it passes through the lamp array it will experience a reduced UV 
dosage as compared to the UV dosage received by an organism that travels 
an irregular turbulent path through the lamp array. The turbulent pathline 
will bring the organism closer to the quartz sleeves and therefore closer 
to the lamps. 
Therefore, it is desirable to increase the turbulent mixing already 
existent in the system as the organism traverses the lamp array. Since the 
cost of the quartz sleeve is related to its length, it is also desirable 
to increase the turbulent mixing in the system in a manner that reduces 
the length of the quartz sleeve. It is further desirable to ensure that 
there is turbulent mixing throughout the UV system lamp array as the 
organism traverses the system. 
SUMMARY OF THE INVENTION 
A method for increasing turbulent mixing in a UV system that is to be 
immersed in a liquid. The system has at least one lamp unit. The method 
includes the step of installing a ring-shaped device at a predetermined 
location on the exterior surface of the lamp unit. 
A UV system for immersion in a liquid. The system has at least one lamp 
unit. The system also has a ring-shaped device located at a first 
predetermined position on the exterior surface of the lamp unit. 
A UV system for immersion in a liquid. The system has a UV lamp unit 
mounted between upstream and downstream end retainers. The system also has 
a ring-shaped device mounted on the upstream end retainer adjacent the 
lamp unit.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
Referring now to FIG. 1, there is shown a perspective view of the UV system 
100 described in the '256 Patent. The system 100 has one or more modular 
racks 10 each of which have a horizontal hangar bar 11. Depending from bar 
11 at an upstream position is a vertical metal rod 12, and depending from 
bar 11 at a downstream position is a vertical metal conduit 15. Conduit 15 
serves as a waterproof passage for electrical cables. 
Pivotally mounted on rod 12 at equi-spaced points therealong are metal 
sleeves 13, each of which has a bullet shaped cap therein. Each of the 
sleeves swivels in a horizontal plane. Mounted on conduit 15 in a 
direction facing sleeves 13 are couplers 16, each housing a lamp socket. 
Extending between sleeve 13 and the corresponding coupler 16 is a lamp unit 
17. The upstream end of each lamp unit is slidably received in the 
associated sleeve and the downstream end is received in the associated 
coupler in a manner well known in the art. 
Each lamp unit 17 comprises of an elongated tubular UV lamp. Each lamp is 
protectively housed in a quartz sleeve which is transparent to the UV 
radiation of the lamp. The upstream end of the quartz sleeve is closed. 
The open downstream end of the sleeve is received in coupler 16 in a 
manner so as to seal the open end. The electrical cables in conduit 15 
pass through coupler 16 to thereby connect to each lamp at the open end of 
the associated sleeve. 
Referring now to FIG. 2, there is shown an upstream end view of a flow 
channel in which a system 100 having five racks 10 is immersed. Each rack 
has four lamp units extending between the associated one of sleeves 13 
mounted on rod 12 and the associated downstream end coupler (not shown). 
FIG. 3 shows a sectional side view of the flow channel 20 with system 100 
of FIG. 2 immersed therein. 
In order to increase the turbulent mixing of each rack 10 in system 100, 
ring-shaped devices, such as washers, were installed over the quartz 
sleeve in each lamp unit. In one embodiment, two washers of the same size 
were installed over each quartz sleeve. FIG. 4 shows a sectional side view 
of the flow channel 20 with the system 100 immersed therein and the two 
washers 22a and 22b installed on the quartz sleeve of each lamp unit in 
the rack. 
One washer was installed at a point that is one-third of the distance from 
the upstream end of the rack to the downstream end. The other washer was 
installed at a point that is two-thirds of the distance from the upstream 
end to the downstream end. Each of the washers were held in place by a 
rubber ring (not shown) located right behind the washer. The washers may 
also be held in place by other means well known to those skilled in the 
art such as a metal piece which presses against but does not crack the 
quartz sleeve. 
Referring now to FIG. 5, there is shown an upstream end view of a flow 
channel in which there is immersed another embodiment for each of the five 
racks in system 100. In this embodiment, turbulent mixing is increased by 
rod 24 and rings 26 which replace rod 12 and metal sleeves 13 of the 
upstream end of the system described in the '256 Patent. The rings 26 were 
welded onto rod 24. The rings 26 hold the upstream end of each lamp unit. 
Whereas each rack of the system described in the '256 patent employs quartz 
sleeves that are 1.61 m in length, each rack of the system of FIG. 5 
employs quartz sleeves that are only 1.56 m in length. Therefore, not only 
does the system of FIG. 5 increase turbulent mixing it also results in a 
reduction of the length of, and thus the cost of, the quartz sleeve. 
A further embodiment (not shown) for each of the five racks in system 100 
increases turbulent mixing by combining the washers 22a, 22b of the 
embodiment shown in FIG. 4 with the rod 24 and rings 26 of the embodiment 
shown in FIG. 5. 
The embodiments shown in FIGS. 4 and 5 and the embodiment which is the 
combination of those embodiments were each tested to determine the 
increase in turbulent mixing. The tests were performed by immersing each 
embodiment in a channel that measures 38.89 cm in width, 46 cm in depth 
and has an approximate length of 12 m. A neutrally buoyant red dye was 
injected into the flow so that video recordings could be made of the 
turbulent mixing and flow patterns. As is known to those skilled in the 
art, a neutrally buoyant dye is a dye that is at the same temperature as 
the water in the channel. 
The red dye was injected into the channel at selected spots. FIG. 6a shows 
a side view of the channel and the four transverse positions 1-4 where the 
dye was injected. The axial location of the dye injection point was fixed 
at 5 cm upstream of each set of washers. FIG. 6b shows a cross sectional 
view of the channel and the dye injection points and FIG. 6c shows a close 
up view of dye injection points 1, 2 & 4. 
In conjunction with the red dye described above, velocity measurements were 
also conducted on the racks. An acoustic doppler velocimeter (ADV) made by 
Sontek was used for these measurements. The ADV was held in place by a 
modified equatorial telescope mount. Since changes in water temperature 
produce corresponding changes in the speed of sound in water the 
temperature of the channel water was monitored using a mercury thermometer 
or other appropriate instrument. 
For the embodiment shown in FIG. 4, velocity measurements were sampled at 
the 27 axial locations identified by the numbers 1-27 shown in FIG. 7a. 
Twenty-four of the 27 axial locations are within the rack. For the 
embodiment shown in FIG. 5, velocity measurements were sampled at the 
twelve locations identified by the numbers 1-12 in FIG. 7b. Nine of the 12 
axial locations are within the rack. 
At each axial location shown in FIGS. 7a and 7b the velocity measurements 
were acquired at the two transverse positions identified as 1 and 2 in 
FIG. 7c. Position 1 is midway between the centerline of adjacent vertical 
and horizontal lamps and position 2, where the UV intensity is at a 
minimum, is equidistant from the four quartz sleeves. 
The testing showed that while the mixing at the upstream end of a rack with 
washers embodied as is shown in FIG. 4 is either equal to or slightly 
reduced as compared to a system with racks embodied as shown in the '256 
Patent, there is a clear increase in mixing throughout the rest of the 
system. The testing also showed that the racks with washers embodied as is 
shown in FIG. 4 had increased average turbulence intensity values as 
compared to a system with racks embodied as shown in the '256 Patent. The 
testing further showed that the average turbulence intensity values 
increased as the washer size increased. The testing also further showed 
that the racks embodied as is shown in FIG. 5 also had increased average 
turbulence intensity values as compared to a system with racks embodied as 
shown in the '256 Patent. 
The results described above for a system with racks embodied as shown in 
FIG. 4 are for that system wherein all of the washers in a system have the 
same diameter. That system was tested with all of the washers having one 
of five different washer diameters to account for differing flow 
velocities. Those washer diameters were 3.81 cm, 4.13 cm, 4.45 cm, 4.76 cm 
and 5.08 cm. 
A system having racks embodied as shown in FIG. 4 was also tested wherein 
each rack had two washers of different diameters installed on the quartz 
sleeve of each lamp unit. One washer of 5.08 cm diameter was positioned 
one third the length of the rack downstream from the upstream entrance 
adjacent to rod 12. Another washer of 3.81 cm diameter was positioned 
two-thirds of the length of the rack downstream from the upstream 
entrance. That system also showed an increased average turbulence 
intensity values as compared to a system with racks embodied as shown in 
the '256 Patent. 
The testing showed a slight decrease in residence time for those systems 
having racks embodied using the present invention as compared to the 
residence time in a system having racks embodied as shown in the '256 
Patent. The increase in turbulence in all of the systems having racks 
embodied in accordance with the present invention is, however, quite large 
in comparison to the small decrease in residence time. 
While the present invention has been described in connection with the 
system shown in the '256 Patent and the multiple racks having multiple 
lamp units described therein, it should be appreciated that turbulent 
mixing can be increased in a system consisting of a single lamp unit by 
using the rings of the present invention. It should further be appreciated 
that while the present invention has been described by an embodiment that 
has shown two rings mounted on each lamp unit and another embodiment which 
shows a single ring mounted on the upstream rod of the rack which holds 
the lamp unit, turbulent mixing may be increased by a single ring located 
either at the upstream or downstream of a lamp unit. 
It is to be understood that the description of the preferred embodiment(s) 
is (are) intended to be only illustrative, rather than exhaustive, of the 
present invention. Those of ordinary skill will be able to make certain 
additions, deletions, and/or modifications to the embodiment(s) of the 
disclosed subject matter without departing from the spirit of the 
invention or its scope, as defined by the appended claims.