ENGR 103 - Spring 2016
Freshman Engineering Design Lab
Freshman Engineering Design Lab
“Outdoor Water Heating System”
Final Report
Date
Submitted: May 12, 2016
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Submitted
to:
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John Speidel, speidel@drexel.edu
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Group
Members:
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Jonathan Altland, jsa65@drexel.edu
|
Pooja Anantha, pa327@drexel.edu
|
|
Kerianne Chen, kmc492@drexel.edu
|
|
Manyah Kohli, mk3336@drexel.edu
|
|
Abigail Martin, aem374@drexel.edu
|
Abstract:
Heat pipes are used to transfer heat and energy to help
regulate temperatures. This Outdoor Water Heating System utilizes solar energy
to heat water. The goal of the project was to design, construct, and test a
heat pipe that will raise water temperatures to prevent freezing in outdoor
water storage units, specifically for use on farms. Heat pipes have been
extensively researched in order to ensure that the system matches the abilities
of previous projects and to determine the proper size and materials for the
project. The main components of the heat pipe are a copper pipe, copper end
cap, copper adapter, and iron end cap. An aluminum wire mesh wick transfers the
distilled water through capillary pressure from the condensation portion to the
evaporation portion, which has the applied heat source, of the pipe. The entire
system is created to fit within a glass solar tube. Challenges include creating
the initial design, attempting to join different types of materials, and
acquiring accurate testing data. Testing was done using a heat gun and two
temperature probes at each end of the heat pipe. The deliverables include
testing data, as well as a working heat pipe of 12 inches length and ½ inches
diameter which heats water.
Introduction
1.1
Problem Overview
The intended purpose of this design is to prevent the
freezing of water in animal troughs. During winter months, precautions must be
taken on farms in order to ensure that animals have access to drinking water at
all times. On some farms this is ensured through the use of electric water
heaters which require an extra source of power. The prospective customers for
this project are farmers who live in cold climates and would have to deal with
potential freezing of water for their animals. The most defining constraint for
this project is the size requirements for it to be properly integrated into the
solar tube system. The requirements are that the pipe must fit within a 1 inch
diameter glass tube and should be 12 inches long so that it extends beyond the
glass solar tube when integrated into the system. Cost was to be minimized so
that profit, when the item is put on market, would be maximized. The weight of
the system is not important since it would be stationary and the consumers
would only need to support the weight during installation.
1.2
Existing Solutions
Since our design is
intended to be used for heating outdoor water systems, the most pertinent
solution existing is solar thermal systems. Such designs are generally designed
for buildings rather than maintaining trough temperatures, but the idea can be
implemented for water troughs or tanks [1]. In general, heat pipes implement
various pipe and wick designs. Pipe designs vary in size and material, and wick
designs vary in terms of material and design. Solar thermal systems are
generally either active or passive [3]. Active systems involve either a direct
circulation system that pumps water through the house, or indirect circulation
that heats water before pumping it into the house. Passive systems involve
thermosiphon systems where warm water rises and cool water sinks, so the system
needs to be positioned below the tank so that the warm water enters the tank.
Solar collectors can also be used with either a flat-plate collector, integral
collector-storage system, or evacuated-tube solar collectors. Flat-plate
collectors contain a dark absorber plate located beneath a glass/polymer cover.
The integral collector-storage systems feature black tank or tubes in an
insulated box, where cold water passes through into a backup water heater and
care should be taken so the pipes do not freeze in extreme temperatures.
Lastly, evacuated-tube solar collectors are composed of metal tubes encased in
a glass outer tube [3]. The systems utilize solar energy to heat water, as our
project is designed to accomplish. Solutions outside of heat pipes or other
solar thermal systems might also prove to be effective. Simpler methods such as
gathering water troughs together and only filling the troughs with the amount
of water animals will drink prevent excess water from freezing. Automatic
watering units and electric tank heaters rely on constant energy and will fail
if the power supply is lost. Propane tank heaters offer an alternative to
electricity based devices but fuel costs and levels need to be taken into
consideration [2]. Overall, these methods can be effective depending on the
intended purposes, but for utilizing solar power, solar thermal systems are the
most practical.
1.3
Project Objectives
The project is a copper heating pipe
designed to conduct heat, solar energy, to regulate heat for outdoor tanks to
maintain non-freezing temperatures. The pipe itself is 12 inches long with an
inner diameter of 0.5 inches. Inside the pipe is a coiled sheet of aluminum
designed to act as a wick and aids in transporting the working fluid. Distilled
water acts as the working fluid and evaporates and condenses to transport heat
throughout the pipe. The working fluid is contained inside the pipe at one end
with a solid copper cap soldered to it, and at the other end with a threaded
adapter and threaded cap. The heat pipe is unique in its size, as it is small
enough to be better adapted into a solar panel or used in solidarity for
smaller tanks/devices. It is better suited than previous methods because of its
simplicity and its dependence on either solar energy or electricity to provide
heat. The final deliverable for the project is a working heat pipe composed of
aforementioned pipe, internal components, and caps.
2
Technical Activities
2.1
Designing the System
The first three weeks of lab consisted of research and
initial designing. In order to create the most efficient design, several
factors were considered. Research showed that a conductive metal, such as
copper, was necessary to create a well-functioning system. The next task was
creating a wick, which would reside inside the copper pipe to help move the
working fluid from the condenser end to the evaporator end. The last design
aspect, which was probably the most difficult, was determining how the pipe
would be sealed. While it seemed easiest to just solder end caps onto the
copper pipe, this could not be done since the working fluid would have to be sealed
inside. To
solve this, a threaded adapter and threaded end cap were used on one side so
that the working fluid could be added after the other end piece had been
soldered to the pipe.
Figure 2: Final Heat Pipe
2.2
Constructing the System
The heat pipe was constructed over the course of two weeks with
the materials purchased from Home Depot. The first step was to cut the copper
pipe to a length of one foot using a pipe cutter, since the length of the pipe
is inversely proportional to the amount of heat it can transfer. It also needed
to be short enough to work with the one foot
glass pipe in which it would harness solar energy. The next step was to fasten
the end cap and threaded adapter to the pipe so that the pipe could be sealed.
These were soldered to the pipe. In order to help move the working fluid,
distilled water, a piece of aluminum mesh wire was cut and shaped into a
cylinder to fit inside the copper pipe. Initially, aluminum fins were going to
be added to the heat pipe in order to help conduct heat, but since it would
take additional materials to fasten to the copper pipe, it was decided that
they would not be used. If the heat fins were added, thermal paste and an epoxy
might have been used to attach them, but the results in the testing suggested
that the system worked well enough without the added fins. The addition of the
heat fins would also make it difficult for the heat pipe to remain within the
design parameters.
Figure 3: Iron End Cap Fusion 360 drawing
2.3
Testing the System
In order to test the heat pipe, a heat gun
and temperature probes were used. The heat gun heated one end of the pipe,
while the temperature probes measured the temperatures at 3 inches and 12
inches from the applied heat. The initial
temperature for the heat applied side was 102 degrees, and the opposite end was
82 degrees. The temperatures plateaued at around 156 for the heated side, and
162 for the farther end, after a total of 590 seconds. Figure 3 shows the data
from the first testing of the system. The jumps in the graph are indicative of
the simplistic testing method. Since the probes were only held by a student
rather than a piece of equipment, it was easy for the probes to get moved,
which would cause spikes in the temperatures seen.
Figure 3: Data from Testing 1
2.4
Modifying the System
Although the system functioned as it
should, a few changes will be tested to determine the optimal heat pipe which
will transfer the most heat. First, the testing will require another person to
help hold the temperature probes in place so that the temperature data is more
consistent. Additionally, the working fluid within the copper pipe will be
altered slightly to find the amount of fluid which transfers the most heat.
3
Project Timeline
Table 1: Project Timeline
Week
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||||||||||
Task
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1
|
2
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3
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4
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5
|
6
|
7
|
8
|
9
|
10
|
Form groups
and brainstorm ideas for project
|
X
|
|||||||||
Continued
research and more detailed design of the system
|
X
|
X
|
||||||||
Get
materials for construction
|
X
|
|||||||||
Construction
of the heating system
|
X
|
X
|
||||||||
Testing and
modifications to the system
|
X
|
X
|
X
|
|||||||
Final
report preparation and final touches
|
X
|
X
|
X
|
X
|
||||||
4
Materials and Budget
Materials and
Supplies:
- 1/2" inner
diameter Copper
pipe
- Copper end cap
- 1/2"
lead-free threaded iron flare cap
- 1/2" threaded
copper adapter
- 0.0329” thickness aluminum sheet
- Aluminum wire mesh
- Thread seal tape (polytetrafluoroethylene)
- Pipe Cutter
- Blow Torch
- Solder
- Flux
- Temperature probes
- Working Fluid: distilled water
Table
2: Project Budget
Item
|
Specifications
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Price
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Supplier
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Copper Pipe
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24" Length, 0.62" OD, ½” inner
diameter
|
$4.11
|
|
Copper End Cap
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½” copper tube cap
|
$0.67
|
|
Threaded End Cap
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½” black malleable iron cap
|
$1.57
|
|
Threaded Adapter
|
½” copper adapter
|
$1.42
|
|
Aluminum Sheet
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6" x 18" x 0.0329"
|
$8.97
|
|
Wire Mesh
|
Aluminum Insect Screen
|
$7.48
|
5
Results
The
final deliverables that have been produced are the constructed copper heat pipe;
data recorded using the temperature probes, and the final report detailing the
process of construction and the methodology of the heat pipe. The final
construction of the heat pipe was slightly modified. Aluminum fins could not be
attached to the copper pipe because they were made of different materials. The
rest of the heat pipe was constructed as planned. The copper tube was cut to
one foot in length and the end cap was soldered on one end. Inside of the tube,
aluminum wiring was used as a wick. The threaded adapter was soldered to the
other end of the tube, and the working fluid, distilled water, was added. The
initial objective for this heat pipe was to create a solar heat pipe system.
Due to the complexity of the solar aspect, the final heat pipe created was
designed to fit inside a glass solar tube. For the testing, a heat gun was on
the evaporation end of the tube, and there were temperature probes at three and
twelve inches from the applied heat to measure the temperature in degrees
Fahrenheit. Temperatures of both ends of the tube were recorded every 10
seconds for a total of 590 seconds. The initial temperature of the evaporating
side was 102 degrees Fahrenheit and the initial temperature of the condensing
end was 82 degrees Fahrenheit. Temperatures plateaued around 156 degrees
Fahrenheit for the evaporating side and around 162 degrees Fahrenheit. Between
550 and 560 seconds, the temperatures on both ends of the tube were the same -
about 156 degrees Fahrenheit.
6
Discussion
The
project produced a working heat pipe which performed in a way that met the
initial criteria and constraints. Changing conditions which could be run into
for the project in the practical application are changes in the outdoor
temperature, variations in the exposure to sunlight, and other cooling factors
such as wind, rain and snow. As the pipe was heated the temperatures at both
the heated and unheated ends rose gradually with the unheated end reaching
higher temperatures more quickly. The unheated end rose in temperature faster
because as the temperature of the heated end rose the working fluid within the
pipe evaporated and facilitated the transfer of heat to the unheated end.
Certain alterations would drastically alter the functionality of the heat pipe.
If the heat pipe were made longer, its ability to move heat would be decreased
and the pipe would be less efficient. If the pipe had a wider diameter the
ability of the pipe to move heat would increase and it could be made more
efficient. However these changes would not allow the heat pipe to fulfill the
role for which it was designed. Heat fins could also be added to aid in the
heat absorption but the size limitations of the pipe would not allow for the
fins to be large enough to have a meaningful impact. If the amount of working
fluid within the heat pipe is changed it will affect the ability of the pipe to
move heat. This could be tested in order to find the optimal amount of fluid
for conducting heat. Some of the main sources of error for the results are the
inconsistency of the placement of temperature probes and the inaccuracy of the
probes themselves. The effects of these errors are minimal since the testing
was done over an extended time period. This time period allows for the testing
to show a general range where the heat pipe is most effective. To improve
testing, the temperature probes might be attached more securely in order to
reduce movement throughout testing. The accuracy could also be improved by
allowing more time between testing with the same equipment so that the probes
have time to cool back to room temperature.
7
References
[1] "Planning and Installing Solar Thermal
Systems", Google Books, 2005. [Online]. Available:
https://books.google.co.uk/books?id=vwp-rDWzEa0C&pg=PA30&dq=solar+thermal+pipes&hl=en&sa=X&ei=zSyJUfD5BYWs0QWXloHgAw&redir_esc=y#v=onepage&q=solar%20thermal%20pipes&f=false.[Accessed:11-May-2016].
[2] P. Cash, "6 Winter Tricks That Keep Livestock Water
From Freezing | Off The Grid News", Offthegridnews.com, 2014. [Online].
Available:
http://www.offthegridnews.com/how-to-2/6-winter-tricks-that-keep-livestock-water-from-freezing/.
[Accessed:11-May-2016].
[3] "Solar Water Heaters | Department of Energy",
Energy.gov, 2016. [Online]. Available: http://energy.gov/energysaver/solar-water-heaters.
[Accessed:11-May-2016].
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