Week 10

          This final lab day was dedicated to group presentations. Each group presented their functional heat pipe as well as the results that they have acquired through testing. They explained the design and application of their heat pipe and stated the total cost to construct their heat pipe. The most important aspects of the final report were used to create the final presentation. This includes the cost, the results, and the heat pipe's application. 
          The total cost for the solar heat pipe that was constructed was $38.19. This price was a little over budget, which was $30.75. This is due to the fact that extra materials were bought in case of manufacturing error or if it is damaged during testing. The timeline that was set for the construction of the heat pipe was followed, with minor revisions due to new materials having to be bought in Week 6 because the materials bought during Week 5 were not effective. 
          A total of three trials were recorded and plotted on a graph, as shown in Figure 1. As seen, the temperature increased, but at different rates, depending on how much of the working fluid was in the heat pipe. Having 100 mL of water inside the pipe, indicated by the red hued lines, did not have a rapid increase of temperature, and therefore was deemed time inefficient. Having 50 mL of water, indicated by the blue hued lines, had a parabolic curve and displayed a cooling trend sooner. Having 66 mL of water in the pipe, indicated by the green-hued lines, had a consistent increase of temperature and was considered the best option as it reached a higher temperature than the other two trials and because the temperature increased consistently. 

Figure 1: Results

          As previously stated in prior blog posts, the heat pipe was designed to cool solar panels. If a solar panel gets too hot, it is not able to create electricity efficiently. By using a heat pipe, the solar panel could be cooled so that it could operate at its maximum potential. Three heat pipes will be used to fulfill this goal, as shown in Figure 2 and Figure 3. Heat travels from a location of high temperature to a location of low temperature, and so it is expected that the heat will travel from the far end of the solar panel to where the heat pipe is attached. The heat will be transferred into the surrounding environment through the condenser section of the pipe.

Figure 2: Back View of Solar Panel

Figure 3: Front View of Solar Panel

          
          The final presentation went well and the heat pipe worked as expected. It was a great experience to work with heat pipes and to gain experience in the chemical engineering field. Using this knowledge and experience, it is felt that any engineering problem can be tackled and accomplished. 

Week 9

       During this week in lab, 67mL of distilled water was used. This was decided upon after reviewing the results of the previous week's lab. The prediction that was made concerning the addition of more water was correct - the heat pipe was able to operate at a higher temperature. It reached a temperature of 160°F, compared to 150°F when only 50mL of water was used.
       It was discussed that for the final presentation, the results of the various trials that were conducted will be shown on one graph. The results can then be easily seen compared to one another. The work will be divided to create the presentation, and there will be time set aside after class to practice presenting. In order for the presentation to go well, the knowledge gained throughout this lab must be utilized and expressed in a timely manner. By practicing multiple times, lapses in speech can be fixed and the expressed knowledge of heat pipes can be more solidified.

Week 8

          This week in lab, the final report draft was reviewed and questions were asked to the leading fellow. Doubts about the calculations and formulas were voiced, and the fellow responded that it was best if the final report included formulas associated with heat pipes even if the formulas weren't actually used. So, in the future, the final report will include formulas, such as the ones involved with the sonic limit, boiling limit, capillary limit, and entrainment limit. The fellow also mentioned that the final report was allowed to exceed more than the eight page limit, as long as the extra information included is relevant to the topic at hand.               

           The heat pipe was tested once again. Similar to the last trial, the heat pipe was placed in a vertical position during testing. Instead of 100mL, 50mL of distilled water filled the heat pipe. The results obtained showed that the heat within the pipe reached up to 150°F. 50mL of fluid was used because it was perceived that filling one-fourth of the pipe with fluid would be the best for the pipe's overall performance. But, after studying the results, it was decided that adding extra water would probably allow the heat within the pipe to reach a much higher temperature, which would be ideal so that the heat pipe could be used to cool down solar panels.

            The following is a picture that shows the testing of the heat pipe:

Two group members testing the heat pipe while another member records the results

Week 7

              Another test trial was conducted to determine the efficiency of the heat pipe. The pipe was held by a stand in a vertical position, so that the flow of liquid into the evaporator section would not only be aided by the wick but also by gravity. The blower was placed right beneath the end of the pipe that marked the beginning of the evaporator section. The thermometer that was meant to measure the temperature at the condenser section was not taped to the pipe as usual, because it was suggested that the tape may prohibit the tip of the thermometer from touching the pipe, thereby leading to inaccurate results. Instead, all three thermometers that measured the temperatures at the evaporator, adiabatic, and condenser sections were held by hand. A challenged faced due to holding the thermometers was that uncontrollable shaking of the hand led to the thermometers' tip often losing contact with the pipe. Even after fifteen minutes had passed by, the evaporator section did not reach a constant temperature, which means that the water inside did not reach its boiling point. The condenser section was still hot despite the water not boiling, because the heat being applied to the pipe could have spread to that section through the copper metal itself and also because the air above the water was getting hot. 100mL of water was inside of the pipe during testing. In the future, less water will be used to fill the pipe so that the water won't take as much time to boil. There was not enough time to wait until all of the liquid had boiled because there were other teams waiting to test their pipes and the lab period had ended. Therefore, the pipe wasn't tested more than once this week.

Week 6

        As mentioned last week, new materials had to be bought due to the lack of flexibility in regards to the heat pipe's liquid volume. Over the weekend, the aforementioned Teflon tape was bought; however, instead of the threaded copper cap, a copper male adapter and a brass cap were bought instead. In order for copper to be threaded, it would need to be thick; however, a cap is supposed to be thin. To overcome this issue, a male adapter and a brass cap were used. On the lab day of week six, the heat pipe was constructed in the machine shop.

        Scotch-Brite was used to clean and smoothen the materials for ease of attachment. Flux coating was then applied to the areas that were going to be soldered together. A thread composed of lead and other metals was then melted along the enclosures that were to be soldered and therefore sealed. After soldering both ends and letting it cool, Teflon tape was wrapped around the threaded male adapter and a wrench was used to tighten the brass cap.

        Testing ensued: the pipe was tilted at about an angle of 45° and testing lasted for about ten minutes. Results only accounted for six minutes of the experimentation due to human error and mid-adjustments made throughout the running experiment. The blower's position was changed midway. The thermometer was not consistently in contact with the heat pipe in terms of position. Data was collected as best as possible, but many problems had occurred regardless.

        The rest of the lab day was then spent on measuring the amount of fluid used as there was no actual liquid measurement tool to do so. It was determined that 87mL was used during the test, and the entire heat pipe itself can hold 200mL. Next week, a rough final draft will be completed and another test will be held for more accurate results.

Week 5

This week in lab, calculations to determine the amount of water that should be in a heat pipe was researched. However, after searching for a long period of time, no formulas surfaced. The professor was questioned and it became known that there are no calculations for heat pipes yet discovered. The professor stated that heat pipe testing takes a lot of trial and error and that the usual amount of water inside of the pipe is equal to 25%-30% the length of the pipe.

The parts that were bought from Home Depot were a ¾ inch by 2 feet copper pipe, wire mesh, and two ¾ inch copper end caps. When lab began this week, it was realized that not all of the parts would work well for this project. If the parts that were bought were used, both ends of the copper pipe would have had to be soldered. This means that it would not be possible to fluctuate the amount of water in the pipe to improve it. Therefore, a screw would have to be placed at one end to allow different amounts of water to be tested. The new parts that will be bought from Home Depot will be a threaded end piece, a threaded cap, and Teflon tape. The Teflon tape will be used to allow the threaded cap to be easily screwed onto the threaded end piece and therefore prevent leakage of the vapor inside of the pipe.

Week 4

        This week, the design team readjusted and finalized that the heat pipe being built would serve the purpose of a solar panel cooler. Once this was done, the purchase of materials had to be made in order to adhere to the timeline.

        The designated time in the lab was spent working on and discussing the scope of the calculations for this design project. This was followed by a conversation about the parameters, limitations, and constraints of the heat pipe.

        A trip to the local Home Depot was conducted on Friday during the afternoon. The total cost of the components rounded off to $20.00. The following items were purchased:

• Qty. 1 3/4" by 2 ft. Copper Pipe
• Qty. 2 3/4" Copper tube Caps
• Qty. 1 36" by 84" Wire mesh

Copper Tube Caps

Copper Pipe (with wire mesh)

Wire Mesh (wick)

Week 3

             This week in lab, further literature study regarding how to build a heat pipe was conducted. Resources portraying and explaining the calculations needed to build a heat pipe were evaluated and studied.

Week 2

      Today, the heat pipe's application was further understood after discussing a proposed design project with the professor and the fellow. After reconfirming the workings of a heat pipe, having the blog thoroughly checked, and examing the design proposal, the fellow questioned the application of the heat pipe. After much mulling, three possible applications of the heat pipe were considered: a solar panel cooler, a liquid cooler, and a self-sustaining thermal phone charger.
      For the solar panel cooler, the heat pipe was to be utilized to absorb the solar panels' heat in order to cool it down. Solar panels are susceptible to overheat, which could damage the solar cells of the panel; therefore, a heat pipe would be a good tool to use. 
      A liquid cooler was to be used as a drink appliance for cooling down lukewarm drinks such as water. The self-sustaining thermal phone charger was a creative idea that involved transforming the phone's released heat into a source of electrical energy that could be used to then charge the phone itself.
      The professor confirmed that the heat pipe did not need to be a sealed vacuum. He suggested to control and adjust the fluid amount in the heat pipe by implementing a cap-like design. Concluding the day, the liquid cooler idea was agreed upon.

Week 1

       On this day, ideas for how to create a heat pipe were discussed. First, it had to be understood as to what a heat pipe is and how it works. A heat pipe is used to transport heat from one location to another. When the pipe is heated, the liquid inside of the pipe begins to evaporate and the vapor travels to the far end, where heat escapes. This allows for the vapor inside to condense and to continue the cycle of evaporation and condensation.

       The metal that can be used for the heat pipe can either be copper, brass, nickel, or any other type of metal. It was deduced that copper would be the best metal to use because it has a high thermal conductivity and a high melting point. When heat is applied to the copper metal, it would not melt and heat would distribute throughout the metal slowly, which is ideal.

      The liquid inside of the heat pipe that can be used can be ammonia, ethanol, acetone, water, and many other liquids. However, water would be the best liquid to use because it has a high boiling point and a useful temperature working range between the temperatures of 303^oF to 550^oF¹.

       The dimensions of the heat pipe were also deliberated. Heat pipes are usually twenty-five centimeters long and about three to four millimeters wide. Therefore, it was decided that the heat pipe that will be constructed in this lab will be twenty-five centimeters in length with a three millimeter diameter.
       The pipe may be filled with water to 1/8 the length of the pipe because research showed that initially, the amount of water is around that amount. The amount of liquid inside of the pipe will continue to be discussed as the weeks progress.

       It has been determined that the machine shop will be utilized to construct the heat pipe. The pipe itself has to be welded at both ends to make it a closed pipe, and the inside of the pipe has to be devoid of air and only filled with water. As decided, the machine shop will be used in the coming weeks when parts are ordered and when the heat pipe is able to be constructed.

References:

1. Faghri, Amir. "Working Fluids and Temperature Ranges of Heat Pipes."ThermalFluidsCentral. N.p., 12 Mar. 2014. Web. 05 Apr. 2016. <https://www.thermalfluidscentral.org/encyclopedia/index.php/Working_Fluids_and_Temperature_Ranges_of_Heat_Pipes>