Weekly Progress

Week 1: How A Heat Pipe Works

For our first laboratory we researched how a heat pipe works and we found the following:

• Heat pipes work as a closed evaporator-condenser system.
• It consists of a sealed, hollow tube, whose inside walls are lined with a capillary structure. This capillary is also know as the wick.
• Heat pipes use thermodynamic fluids (eg. water).
• When heat is applied, the liquid in the wick heats and evaporates. As the fluid evaporates, it fills the hollow center.
• Condensation occurs when the evaporated fluid cools down to a temperature below it's evaporation point. As the vapor condenses, the heat acquired from the evaporation is given off.
• This thermal conductivity helps the pipe maintain a constant temperature along it's entire length.

https://www.aavid.com/product-group/heatpipe/operate

Week 2: Brainstorming a Design for Our Heat Pipe

During week 2, Jakob Siegel joined the group. We also brainstormed some design ideas for the heat pipe. Our heat pipe brainstorming consisted of three major components:

• The structure of the pipe 
• The wick design 
• The working fluid

When considering the structure of the pipe, we focused on the strength, the thickness, the diameter, and the material of the pipe. We decided that choosing the pipe material should be the firs step. We discovered that the choice of the pipe material depended on the choice of the working fluid. Therefore, we decided to examine the choices of working fluid first. Our main concern in this choice was the temperature at which the fluid would be used efficiently considering the temperature of the air gun. The appropriate temperatures for each working fluid can be found in the graph below.

We found water and Naphthalene had the best temperature range, water’s efficiency range being from 25-300*C while Naphthalene was efficient at 110-500*C. We plan to test both of these, but we figure water is the better choice because it is more affordable, easier to heat up, and safer. Both of these fluids are compatible copper, so we decided a copper pipe would be the best choice. A thin pipe with a half inch diameter is most desirable because it will be easier to heat up, and it will respond more quickly to the process. Finally, we assessed the practicality of using a wick. The inclusion of wick, will preferred, is our last priority. We looked up the different types of wicks, and we think that the grooved wick would suit our heat pipe the best. However, adding a wick design will increase the possibility of a leak. After we finish our first prototype of a heat pipe, we will design a second that includes the wick, and we will the test the differences.

Overall, we decided to use a foot-long, half-inch diameter copper pipe, water or Naphthalene for the working fluid, and a grooved wick or no wick at all. The next step is purchasing the materials and beginning the construction of our pipe.

Week Three

In this week's design lab we continued research on Heat Exchange Pipes, with a focus upon how wick choice and shape will influence the heat pipe's performance. Our research showed that since a heat exchange pipe's effectiveness can be influenced heavily by surface area. 

CPU heat sinks utilize fans and redundant sheets to

 maximize heat transfer by actively cooling the pipes

This research led us to consider ways we may be able to optimize our pipe's heat transfer capability. One idea which has been suggested is to use some of the techniques used in heat sinks such as using a fan to actively cool the transfer end of the pipe if we intend to use our heat pipe for purely cooling purposes as opposed to transferring the heat.

Week Four

During lab this week we continue our investigation taking in consideration the limitations and applications that a heat pipe may have.

Limitations:

-Heat pipes depend upon their size, material and the coolant being used. These factors all have optimal temperatures, that must be taken into consideration for the heat pipe work.

-Heat pipe manufacturers usually can’t make heat pipes with a diameter smaller than 3mm due to the material limitations.

Applications:

-Spacecrafts: On modern spacecraft the transfer of heat has been accomplished without electrical power or moving parts through heat pipes. Heat pipes or loop pipes are used because they don’t require any power to operate. Heat pipes operate isothermally, managing the transportation of heat over long distances. The heat pipes used in spacecrafts are built from aluminium. The pipes posses grooved wicks since heat pipes don’t need to operate against gravity in space. The fluid used within these pipes is ammonia or ethane.

-Computer systems: Heat pipes began to be used in computer systems around 1990. The increasement of power resulted in an increase in the heat transmission, which demanded better cooling system. Now a day uses heat pipes are used to move heat away from central processing unit and graphics processing unit.

-Solar Thermal: Heat pipes are used in solar thermal water heating. The pipe material is copper, while the fluid used is distilled water.

-Ventilation heat recovery: In heating and air conditioning systems, heat pipes are placed in the supply and exhaust air streams of an air handling system, in order to recover the heat energy. These heat pipes posses a capillary wick. Also the fluid used within these heat pipes is refrigerant. 

-Nuclear power conversion: Heat pipes made from alkali metals are used in order to transfer heat from the heat source to a thermionic or thermoelectric converter and generate electricity. Since 1990 a large number of nuclear reactor power systems have been proposed the use of heat pipes for the transmission of heat between the reactor core and the power conversion system. But it was until the 3rd of September of 2012, when the first nuclear reactor was first operated using heat pipes.

-Permafrost Cooling: Heat pipes are used in extreme cold environments, where permafrost exists. Without the use of heat pipes the heat generate could thaw the permafrost and cause destabilization. One example where heat pipes are used is the Trans-Alaska Pipeline System. The fluid used along these heat pipes is ammonia. 

-Finally, at the end of lab we discussed the materials that were needed for our next lab.

Materials:

-1 x 5’ x ½’’ copper tube.

-10 x ½’’Copper Tube caps.

Week Five

During Week 5, we brought together all of our materials, and we planned out how we could effectively use them. Although we debated for a while over the various designs we wanted to use to save money/materials, we ultimately decided to begin by creating one design and working from there. Although cost and materials are definitely important concerns, we do not want to compromise the effectiveness of our heat pipe by being stingy. The success of the first design of the heat pipe would ultimately determine how conservative we would be with our materials. If the first design is a success, we will be more liberal with our materials since we already have a working product. However, if the product is troublesome, we will be more cautious because we will have a lot of work to go. Once we decided how much material we would be using, we then discussed whether or not a wick was worth it. While a proper wick would be more effective, there is a higher likelihood that our heat pipe can have a leak.

As seen in the image above, a wick would stick out the top, and even though it could be soldered, we weren't sure whether the risk was worth it. We finally decided to make a functional heat pipe without the wick before making a second product with a wick to ensure time. the Overall, the majority of this lab section was spent debating over how we would use our materials and the incorporation of a wick or not.

WEEK SIX

In week six we suggest for the best performance started the procedure by cutting the heat pipe one feet with that piece called killer pipe. Then we flux one of pipe head by in cab from any leakage will eventually render the pipe inoperable. We solder the head with the metal wire to sealed it and ensure reliable from any leaks in the test.

Week Seven:

During this weeks lab we concluded that there were certain difficulties in connecting the one feet pipe to an external piece. The problem emerged when we found out the pipe and the metal part had the same thickness of 1/2 inch. We needed to solve this problem because this external metal piece was essential in order to be able to screw the iron cap. Therefore some adjustments needed to be performed.

Using heat and a fusible metal alloy we were able to solder, create a permanent bond, the two metal pieces. This action allowed us to terminate the production of our first heat pipe. Consequently, we added thread seal tape where we screw the iron cap.

Finally, we are looking forward to collect our data and probably built other heat pipes.