Original Project Proposal
ENGR 103 - Spring 2016
Freshman Engineering Design Lab
Heat Pipes for Electronics Cooling
Date Submitted: April 7, 2016
|
Group Members Alec Carlson, anc84@drexel.edu
Tran Ly, tl633@drexel.edu
Matthew McConomy, mwm64@drexel.edu
Shjon Powelczyk, smp393@drexel.edu
Technical Advisors John H. Speidel, speidel@drexel.edu
Long Nguyen, lkn25@drexel.edu
Abstract:
As assigned by the section advisor, a working prototype of a heat pipe is expected to be produced from this design project. Based on the temperature of the heat source used to test the pipe, appropriate working fluid and hardware materials will be used, which will consist of copper for the pipe, water as the working fluid, and an aluminum wick. These materials have been chosen due to their low cost and the temperature range at which they are most effective. In order to obtain desirable results, background research, part acquisition and assembly, and proper analysis and modifications will need to be made. A project timeline is included to roughly outline the tasks expected to be done in a certain week. A total of ten weeks is needed to complete this project. The machine shop at Drexel University will be utilized frequently to perform part assembly as well as to obtain necessary tools. A list of any expenses needed to be made for this project is provided in this proposal. At the end of the project, a working prototype will be produced and analyzed in the context of its use in a variety of electronics cooling applications.
1 Introduction
The management of excess heat is a common problem in many of today’s technologies. Facilitating the transport of this heat away from the source is crucial to ensuring the longevity and reliability of any machine. Heat pipes provide a simple and unique solution to this problem because of the effectiveness with which they conduct heat. Ideally, heat sinks and coolants would be placed next to every heat source, however due to issues of safety, materials compatibility, and space, this is not always feasible. Heat pipes serve as the best solution to this issue as they can effectively remove the heat from a source to be cooled at a separate location.
The goal of this project is to build a working prototype of a heat pipe which can conduct heat quickly and effectively. Through working on the project, fundamental knowledge on heat conduction, heat pipes and their components will be acquired. It is important to learn about different types of materials and their physical properties prior to deciding on which ones will be the best fit for the end product.
The prototype will serve as an example of the effectiveness of the materials used at transporting heat away from a source. This analysis is intended to influence future materials decisions in the use and construction of heat pipes, as well as encourage the exploration of their versatility in an ability to function in a variety of cooling applications.
2 Deliverables
Upon completion of the project, an operable copper heat pipe with water working fluid and an aluminum wick will be produced. Using a hot air blower, it will be shown that this heat pipe is effective in transferring heat away from a heat source. This copper/water heat pipe with aluminum wick combination will serve as a prototype to demonstrate the effectiveness of these materials for future electronics applications.
3 Technical Activities
Major tasks include conducting research, assembly, and testing the end product. Within these tasks, sub-tasks need to be completed, such as the decision of which materials will be most effective in the completed design. The most challenging task will most likely be creating a partial vacuum inside of the pipe. Too much air left inside could prevent the pipe from functioning efficiently.
3.1 Research
Review of academic literature on the variety of materials and applications of heat pipes is necessary before beginning the development of a prototype. Consultations with experts and professionals may be scheduled if needed.
3.1.1 Finalization of Materials
The effectiveness of the heat pipe will entirely depend on the materials from which it is constructed. It is imperative to use materials that will operate under the temperature range of 250°F to 500°F, the conditions at which the pipe will be tested. It is also important to be aware of the chemical interactions of the materials to ensure that they will not oxidize, corrode, or otherwise react during operation.
3.1.2 Review of Equations
Various energy equations can be used to observe the relationship between variables such as pipe length, pipe radius, working fluid density and viscosity, temperature, and wick capillary radius. Some of these properties are inherent to the materials being used, however variables such as pipe length and radius as well as the capillary size of the wick can be chosen to maximize the transfer of heat under the temperature range at which the pipe will be operating. The use of thermal conductivity equations as well as numerical materials properties (such as viscosity and surface density) will be needed to complete the analysis.
3.2 Assembly
The materials need to be carefully and quickly assembled to ensure that there is a partial vacuum on the interior of the pipe where gas or liquid cannot escape.
3.2.1 Securing the Endcap
The two ends of the copper pipe must first be cleaned with a steel wool to maximize the effectiveness of the solder. One end is then coated in flux and the endcap secured. The flux prevents the copper from oxidizing when the pipe is heated, which will improve the life and the effectiveness of the soldered components. The endcap will then be heated and lead-free solder applied to close the seal between the cap and the pipe. After the solder has cooled, it will be necessary to check for and to fill any holes or leaks before continuing.
3.2.2 Forming a Partial Vacuum
To start, 25% of the pipe will be filled with water. Slightly more water than necessary is added since the excess will boil off when the vacuum is formed. The open end of the pipe is prepared by clearing with a steel scrub and coating with flux. The closed end of the pipe is heated about a quarter of the way up from the bottom to ensure that the existing solder does not liquify. Once steam is observed exiting the open end of the pipe, the cap is secured with solder. A check for leaks will be necessary once the solder has hardened.
Because the cap is placed on top after some of the liquid has vaporized, a partial vacuum is formed inside of the pipe. The upward traveling vapor ensures that most of the trapped air was pushed out and could not re-enter. This partial vacuum is crucial to the operation of the heat pipe. If too much air is left inside the pipe, the pressure will not allow the water to easily vaporize, which will reduce it’s ability to transfer heat. However, if too much vapor is allowed to leave the pipe, the remaining water will all vaporize once the pipe is heated, which will prevent condensation and not allow the working fluid to collect and transfer heat.
3.3 Testing and Analysis
The effectiveness of the heat pipe prototype can be tested using a heat source and a temperature sensor. Starting at room temperature, the pipe can be heated using a heat source such as a blow dryer or some hot water. This can then be repeated with a standard copper pipe without working fluid or a wick. The time it takes for the other end of the pipe to reach a certain temperature can be found for each pipe and compared. If the prototype transfers heat as expected, the end should reach the target temperature more quickly than the regular pipe.
4 Project Timeline
Table 1: Anticipated Project Timeline
Week
| ||||||||||
Task
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
9
|
10
|
Literature study
|
x
|
x
|
x
| |||||||
Finalize design
|
x
|
x
| ||||||||
Order materials
|
x
| |||||||||
Soldering instruction
|
x
| |||||||||
Prepare materials and assemble
|
x
|
x
| ||||||||
Design testing and modifications
|
x
|
x
|
x
|
x
|
x
| |||||
Final report preparation
|
x
|
x
|
x
| |||||||
5 Facilities and Resources
Access to the machine shop will be necessary to complete the construction of the heat pipe. Soldering materials, such as a soldering iron or blowtorch (preferred), as well as lead free solder will be needed to secure the endcaps of the heat pipe. Access to a small workspace within the machine shop with a table and various clamps will be needed for a period of about 2 hours. Access to a testing apparatus, like the one provided by the technical advisor for the lab, will be necessary for analysis of the completed design.
6 Expertise
This project requires some familiarization with heat pipes, how they operate, and their various applications in the real world. Expertise is also required in techniques of soldering for the purpose of securely attaching two metals.
7 Budget
Table 2: Project Budget
Category
|
Projected Cost
|
Manufacturer
|
Location
|
0.5 in x 5 ft Copper Type M Pipe
|
$9.92
|
Mueller
|
Grainger
|
5/8 in Copper Tube Cap (2)
|
$2.20
|
NIBCO
|
Grainger
|
Metal Pipe Cutting Tool
|
$6.98
|
GOCHANGE
|
Amazon
|
Lead Free Tinning Flux
|
$2.96
|
Oatey
|
Amazon
|
Steel Wool
|
$5.71
|
Red Devil
|
Amazon
|
36 in x 7 ft Aluminum Screen
|
$10.90
|
New York Wire
|
Grainger
|
Estimated Shipping
|
$20.00
| ||
TOTAL
|
$58.67
|
7.1 0.5 in x 5 ft Copper Type M Pipe
The length of copper pipe will be cut to 3 ft. to fit the constraints of the final testing apparatus. The copper pipe serves as the chamber for the wick and working fluid, which together create the heat pipe.
7.2 5/8 in Copper Tube Cap (2)
Two copper tube caps are used to close each end of the heat pipe. They will be secured using flux and lead-free solder to ensure that a partial vacuum is formed within the pipe chamber and that no gas or fluid can escape.
7.3 Metal Pipe Cutting Tool
A hand operated metal pipe cutting tool will be used to cut the length of copper pipe to the proper size. Since it will only be needed for a few cuts, a cheap, single-use type tool can be acquired.
7.4 Lead Free Tinning Flux
Flux will be used to coat the copper pipe before securing the endcap. The flux ensures that the copper does not oxidize when it is heated during the soldering process. This is critical, as tin solder adheres best to copper that has not been oxidized.
7.5 Steel Wool
Steel wool will be used to clean the copper pipe before securing the endcaps. Cleaning the pipe ensures that the flux and solder will adhere securely to the pipe so that no gas or fluid can escape.
End Original Proposal
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Updated Design Proposal (Wick Comparison)
ENGR 103 - Spring 2016
Freshman Engineering Design Lab
Heat Pipes for Electronics Cooling
Date Submitted: April 14, 2016
|
Group Members Alec Carlson, anc84@drexel.edu
Tran Ly, tl633@drexel.edu
Matthew McConomy, mwm64@drexel.edu
Shjon Powelczyk, smp393@drexel.edu
Technical Advisors John H. Speidel, speidel@drexel.edu
Long Nguyen, lkn25@drexel.edu
Abstract:
As assigned by the section advisor, a working prototype of a heat pipe is expected to be produced from this design project. Based on the temperature of the heat source used to test the pipe, appropriate working fluid and hardware materials will be used, which will consist of copper for the pipe, water as the working fluid, and an aluminum wick. These materials have been chosen due to their low cost and the temperature range at which they are most effective. In order to obtain desirable results, background research, part acquisition and assembly, and proper analysis and modifications will need to be made. A project timeline is included to roughly outline the tasks expected to be done in a certain week. A total of ten weeks is needed to complete this project. The machine shop at Drexel University will be utilized frequently to perform part assembly as well as to obtain necessary tools. A list of any expenses needed to be made for this project is provided in this proposal. At the end of the project, a working prototype as well as an analysis will be produced to describe the relationship between wick mesh size and rate of heat transfer. The most efficient wick size will be used in the prototype to display its effectiveness in non-vertical cooling applications and its possible use in electronics will be detailed in a final report.
1 Introduction
The management of excess heat is a common problem in many of today’s technologies. Facilitating the transport of this heat away from the source is crucial to ensuring the longevity and reliability of any machine. Heat pipes provide a simple and unique solution to this problem because of the effectiveness with which they conduct heat. Ideally, heat sinks and coolants would be placed next to every heat source, however due to issues of safety, materials compatibility, and space, this is not always feasible. Heat pipes serve as the best solution to this issue as they can effectively remove the heat from a source to be cooled at a separate location.
The goal of this project is to compare different internal metal mesh wicks that can be used in copper/water heat pipes. The aim is to establish a relationship between wick mesh size and rate of heat transfer. Through working on the project, fundamental knowledge on heat conduction, heat pipes and their components will be acquired. It is important to learn about different types of materials and their physical properties prior to deciding on which ones will be the best fit for the end product.
The prototype will serve as an example of the effectiveness of the mesh wick used at transporting heat away from a source. This analysis is intended to influence future materials decisions in the use and construction of heat pipes, as well as encourage the exploration of their versatility in an ability to function in a variety of cooling applications.
2 Deliverables
Upon completion of the project, an operable copper heat pipe with water working fluid and the most effective aluminum wick will be produced. Using a hot air blower, it will be shown that this heat pipe is effective in transferring heat away from a heat source. This copper/water heat pipe with aluminum wick combination will serve as a prototype to demonstrate the effectiveness of these materials for future electronics applications. In addition to the final report, a final analysis will be produced, comparing the effectiveness of the three wick sizes tested and describing the relationship between mesh size and heat transfer.
3 Technical Activities
Major tasks include conducting research, assembly, and testing the end product. Within these tasks, sub-tasks need to be completed, such as the decision of which materials will be most effective in the completed design. The most challenging task will most likely be creating a partial vacuum inside of the pipe. Too much air left inside could prevent the pipe from functioning efficiently.
3.1 Research
Review of academic literature on the variety of materials and applications of heat pipes is necessary before beginning the development of a prototype. Consultations with experts and professionals may be scheduled as needed.
3.1.1 Finalization of Materials
The effectiveness of the heat pipe will entirely depend on the materials from which it is constructed. It is imperative to use materials that will operate under the temperature range of 250°F to 500°F, the conditions at which the pipe will be tested. It is also important to be aware of the chemical interactions of the materials to ensure that they will not oxidize, corrode, or otherwise react during operation. Three wicks, of the same material and manufacturing quality but of different size, will need to be obtained for comparison.
3.1.2 Review of Equations
Various energy equations can be used to observe the relationship between variables such as pipe length, pipe radius, working fluid density and viscosity, temperature, and wick capillary radius. The analysis will focus on the rate of heat transfer using data collected from the temperature sensor. An equation describing the relationship between wick mesh size (holes per inch) and rate of heat transfer will be found using the relationships observed.
3.2 Assembly
The materials need to be carefully and quickly assembled to ensure that there is a partial vacuum on the interior of the pipe where gas or liquid cannot escape.
3.2.1 Inserting the Wick
To start, 25% of a 2 ft long copper pipe will be filled with water. Slightly more water than necessary is added since the excess will boil off when the vacuum is formed. The aluminum, wire mesh wick is then inserted and thoroughly wetted. It is imperative that the wick is not dry, else the vapors will not condense and be transported upon it. If this does not occur, the heat pipe will not transfer heat as expected, and the wick’s impact on that heat transfer cannot be measured.
3.2.2 Forming a Partial Vacuum
As the pipe is heated, the end is closed with a compression cap as soon as vapors are observed exiting from the pipe.
Because the cap is placed on top after some of the liquid has vaporized, a partial vacuum is formed inside of the pipe. The upward traveling vapor ensures that most of the trapped air was pushed out and could not re-enter. This partial vacuum is crucial to the operation of the heat pipe. If too much air is left inside the pipe, the pressure will not allow the water to easily vaporize, which will reduce it’s ability to transfer heat. However, if too much vapor is allowed to leave the pipe, the remaining water will all vaporize once the pipe is heated, which will prevent condensation and not allow the working fluid to collect and transfer heat.
3.3 Testing and Analysis
The effectiveness of the heat pipe prototype can be tested using a heat source and a temperature sensor. Starting at room temperature, the pipe is to be heated using a hot air blower on the lowest temperature setting. The pipe will be mounted on an angle of 30 degrees with the horizontal to test the effectiveness of each wick. After each trial, the pipe is allowed to cool and the wick replaced. A vacuum is again formed and the data collection repeated.
After all trials (one with each wick, and a fourth with no wick) are completed, the rate of heat transfer for each wick test is analyzed. Using the slopes from the graph obtained, an equation can be formed describing the rate of heat transfer as a function of mesh size (holes per inch).
4 Project Timeline
Table 1: Anticipated Project Timeline
Week
| ||||||||||
Task
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
9
|
10
|
Literature study
|
x
|
x
|
x
| |||||||
Finalize design
|
x
|
x
| ||||||||
Order materials
|
x
| |||||||||
Data Recording Training
|
x
| |||||||||
Prepare materials and assemble
|
x
|
x
| ||||||||
Design testing and analysis
|
x
|
x
|
x
|
x
|
x
| |||||
Analysis and final report preparation
|
x
|
x
|
x
| |||||||
5 Facilities and Resources
Access to the machine shop will be necessary to complete the construction of the heat pipe. A small workspace in which to construct the heat pipe as well as to collect data will be needed for a period of roughly 3 hours (nonconsecutive).
6 Expertise
This project requires some familiarization with heat pipes, how they operate, and their various applications in the real world. This will occur during the literature study phase of the project. Some training is also required in the use of the temperature sensor data recording software. One week is allotted for this training.
7 Budget
Table 2: Project Budget
Category
|
Projected Cost
|
Manufacturer
|
Location
|
0.5 in x 5 ft Copper Type M Pipe
|
$6.76
|
Mueller
|
Home Depot
|
Compression pipe cap (2)
|
$13.84
|
SharkBite
|
Home Depot
|
Metal Pipe Cutting Tool
|
$9.97
|
SharkBite
|
Home Depot
|
Heat Insulation Tape
|
$7.28
|
Nashua
|
Home Depot
|
Dual Temperature Heat Gun
|
$21.70
|
Genesis
|
Home Depot
|
Temperature Sensor
|
$26.99
|
Nicety
|
Amazon
|
Aluminum Screen (3)
|
$33.00
|
Saint-Gobain
|
Home Depot
|
Estimated Shipping
|
$0.00
| ||
TOTAL
|
$119.54
|
7.1 0.5 in x 5 ft Copper Type M Pipe
The length of copper pipe will be cut to 3 ft. to fit the constraints of the final testing apparatus. The copper pipe serves as the chamber for the wick and working fluid, which together create the heat pipe.
7.2 Compression Pipe Cap (2)
Two compression pipe end caps are used to close off each end of the tube. They can be easily removed to allow for replacement of the screen.
7.3 Metal Pipe Cutting Tool
A hand operated metal pipe cutting tool will be used to cut the length of copper pipe to the proper size. Since it will only be needed for a few cuts, a cheap, single-use type tool can be acquired.
7.4 Heat Insulation Tape
Heat insulation tape will be used to secure the temperature sensor to the outside of the heat pipe. The tape is insulated to ensure that the temperature of the pipe surface is recorded, and is minimally affected by the ambient temperature in the room.
7.5 Dual Temperature Heat Gun
The heat gun will be used to heat the end of the copper pipe. It will be kept at a constant setting for each trial to ensure comparability of results.
7.6 Temperature Sensor
A high heat temperature sensor will be used to record the temperature on the surface of the heat pipe. The sensor has been designed to work at temperatures in excess of 750 F, well beyond the necessary range for the proposed tests.
7.7 Aluminum Screen
Three different mesh sizes of aluminum wire screen will be tested as wicks. Analysis will be conducted to find the relationship between mesh size (holes per inch) and heat transfer capability.
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