I. Abstract
IV. Discussion & Analysis
With Edison’s invention of the first public coal burning power plant
in the 1800’s, electricity generation became a necessity for
industrialized nations, and thermal power plants proliferated
throughout society. However, these plants required cooling
facilities, lest the heated effluent damage aquatic life in the nearby
reservoirs the plants drew their cooling water from. As a result,
many methods of cooling water emerged, in order to attempt to
alleviate the thermal pollution problem. However, many of them
are extremely large or require power on their own, making them
unfeasible for developing nations, and costly to construct. As a
result, our group wished to find a newer, cheaper method to cool
water, resulting in the development of a riffle system. Our riffle
system uses forest detritus, wire mesh, and clay barriers to
function, all of which are easily obtained and inexpensive.
Our hypothesis was supported, as riffles were shown to be more
effective at cooling water and reintroducing dissolved oxygen
than both the natural rate of cooling and an empty pipe. The
riffles, on average, cooled the water 20°C more than the natural
cooling rate of water, and added 2mg/L more dissolved oxygen
than standing water. However, the riffle system, by design, is
heavily reliant on ambient air temperatures. As a result, we
predict that it will be unable to cool water as effectively in
warmer conditions, due to the lack of cool air available for heat
transfer. This is partially alleviated, however, by warmer receiving
waters on days with high air temperatures. Therefore, future
experimentation may focus on
improving the riffle design to cool
thermal effluent more effectively,
through the use of heat conductive
and insulating materials, improved
design concepts, as well as possibly
introducing
an
element
of
bioremediation that may also purify
Figure 1.7: Water movement
effluent as it passes through.
Figure 1.5: Heating Simulated Effluent
Figure 1.6 Testing with the Riffle System
The starting temperatures and dissolved oxygen content was
measured and recorded, then 5 liters of boiling water was
run through the riffle system. We performed three trials for
each different system. The ending temperatures and
dissolved oxygen were then taken, recorded, and compared
to the starting measurements
III. Results
The results of our experiment are shown in Figure 2.1 and in
Figure 2.2. From t-tests compared to the empty pipe, the
riffles had a p-value of 0.01, while the empty pipe had a pvalue, of 0.004, both of which are shown to be statistically
significant.
Figure 1.1: Hyperboloid Cooling Towers
Figure 1.2: Crossflow Cooling Towers
II. Methods
To create our new cooling method, we decided to go for the
cheapest options possible. We obtained 6 ft. and 7 ft. 3 PVC
pipes with 3 in. radii and sawed them in half. Afterwards, we
connected them using a 45 degree PVC connector. We placed
plant material (Douglas Fir Boughs) into the 7 ft. end, and
created a system of wire and clay barriers in the 6 ft. section.
Both pipes were laid at a 15° angle for testing
Dissolved Oxygen (mg/L)
6
2.1: Average Ending Dissolved Oxygen
V. Conclusion
5
•
4
•
3
2
•
1
0
Empty Pipe
0
Riffle System
Natural Cooling
2.2: Average Change in Temperature
•
Riffles significantly reduce effluent temperature, and
reintroduces significant amounts of dissolved oxygen
Riffle systems are notably cheaper and easier to construct
and maintain than larger cooling systems.
Riffle systems may be used in third world countries, or
areas that cannot afford a cooling tower, but require a
water cooling system to prevent environmental damage.
Riffle systems are versatile; their design can be adjusted for
the means available, cooling requirements, and
construction expertise of the builders.
Temperature Change (°C)
-5
References & Acknowledgements
-10
Special thanks to our parents for transport and letting us test, as well as pictures. Also, thanks to
the Camas MST Magnet staff, for encouragement on the project, Mr. Liu for information on
thermal materials, and Mr. Chase for letting us use the workshop to cut the pipe
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Turpin, Joanna R. "A Solution for Thermal Pollution." Engineered Systems Sept. 2004:
44,46,48,50,52.Web. 1 Oct.2014. http://search.proquest.com
“Water Properties: Dissolved Oxygen.” Dissolved Oxygen, from USGS Water Science for Schools: All
about water. U.S. Govt., n.d. Web. 20 Nov. 2014
Wolfe, J. (2008). Special Report. Water Management: Costlier, scarcer supplies dictate making
thermal plants less thirsty. Power, 152(1), 46-46. Retrieved October 1, 2014, from
http://search.proquest.com
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Figure 1.3 Setup of the Riffle System
Figure 1.4 The PVC Joint
Empty Pipe
Riffle System
Natural Cooling