Design of a Solar Powered Portable Refrigerator Phase 4



Group 28Design of a Solar Powered Portable Refrigerator Phase 4Chris Berberoglu, Stephen Vargas, Jake Witter, Carl Caserta, Price HuClass of 20152/17/2015Contents TOC \o "1-3" \h \z \u Solar Vac Pack Summary PAGEREF _Toc411929833 \h 3Phase IV Project Statement PAGEREF _Toc411929834 \h 3Overall Design & Engineering Analysis PAGEREF _Toc411929835 \h 3Prototype Fabrication Plan PAGEREF _Toc411929836 \h 7Overview PAGEREF _Toc411929837 \h 7Major Components: Overview/Shaping/Assembly PAGEREF _Toc411929838 \h 8Electrical Components: Overview & Assembly PAGEREF _Toc411929839 \h 12Cost PAGEREF _Toc411929840 \h 16Performance Testing PAGEREF _Toc411929841 \h 20Overview PAGEREF _Toc411929842 \h 20Equipment PAGEREF _Toc411929843 \h 20Baseline Assumptions PAGEREF _Toc411929844 \h 20Test Scenario PAGEREF _Toc411929845 \h 21Setup PAGEREF _Toc411929846 \h 21Testing Results PAGEREF _Toc411929847 \h 22Actions based on the major comments and suggestions from ME 423 panel. PAGEREF _Toc411929848 \h 24Gantt Chart PAGEREF _Toc411929849 \h 25Works Cited PAGEREF _Toc411929850 \h 26Solar Vac Pack SummaryThe goal for this project is for the team to design a portable solar-powered refrigerator to be used primarily as a vaccine transportation device by the World Health Organization and other humanitarian users. Today there are many places around the globe that do not have access to enough, if any, electrical power. As such, the team will aim to develop a self-sustaining, green energy refrigeration device to help those in such remote places keep necessities cold during transportation. The team will work to design a product that will incorporate solar energy, Peltier cooling modules and phase change materials to increase efficiency and cooling power. The team aims to create a device that will be able to keep its internal temperature within a 2-7 degrees Celsius range for extended periods of time to ensure that vaccines do not spoil. Phase IV Project StatementIn this stage within the project life cycle the team aims to begin fabrication of a working prototype which will demonstrate the feasibility of our design. The main goals or milestones that the team aims to reach with the cooler is that it will successfully be able to cool the interior volume from a specified exterior temperature to within a 2-7 degree Celsius range running off of stored solar energy. The next goal will be to maintain the interior temperature without any external power supply for a minimum of 24 hours indicating that the phase change material is effective. The final goal will be to ensure that the entire build is sturdy enough to handle transportation and light enough to remain portable. In order to complete this phase of the project successfully the team will need to meet all of the required deliverables following the timeline structured through our Gantt chart. These include creating a fabrication plan for building the prototype in addition to an in depth performance testing section to analyze the running operation of the system once built. The team plans to take all comments and critique from phases one through three and incorporate any suggestions and improvements into our design in order to successfully bring this project from the virtual stage into the physical world. Overall Design & Engineering Analysis The team focused on updating the design selected in phase three. An optimization study using Microsoft Excel was done with the objective of maximizing the time until vaccine spoilage while maintaining the weight, volume, and energy specifications all outlined in phase two of the project. Five scenarios were tested with each optimized design before the design was approved. The calculations for each scenario are as follows:The first was a steady state scenario, where solar panels would theoretically supply enough power to keep the thermoelectric coolers running and withdrawing enough heat from the cooler to keep the vaccine cool and the phase change materials completely frozen. The second scenario was a transient scenario, where the vaccine and phase change materials had to be cooled down to the phase change temperature, and the phase change material frozen. The third scenario was designed to see how much power and time were required to cool the phase change material and vaccine down when the thermoelectric modules were operating under maximum loads. The fourth scenario was designed to see how long it would take the vaccines to spoil in the absence of any sort of electrical power. The last scenario was designed to see how long it would take the vaccines to spoil while the thermoelectric modules were operating on battery power alone. Each scenario will be explored in turn in order to lay out the calculations used and assumptions made. After all the scenarios have been explained, an example will be given using the Microsoft Excel calculator that the group created in order to simplify the calculation and design process. However, before explaining these scenarios, it is important to understand how the thermoelectric modules were modeled, so the relation between the amount of heat that needs to be offloaded and the amount of heat that is required to run the thermoelectric module can be understood.The heat transferred by a thermoelectric module can be modeled using the Peltier equation:Where Q’ is the heat transferred out, P is the Peltier coefficient of the module, and I is the applied current. Because P is a function of the voltage across the Peltier Module and the temperature differential created by the model, the required current for any given heat load can be modeled as follows:Using information from manufacturer websites, the Peltier coefficient can be determined. The electrical power required to run the Peltier module is simply the current required to run the Peltier module times the voltage across the Peltier module,This equation lets the group know if the selected Peltier modules, phase change materials, and dimensions of the cooler will be sufficient to meet design requirements. In each scenario, the amount of heat that the thermoelectric modules needed to offload was calculated and fed into this series of equations to determine the power requirements of the batteries and solar panels, and if they would be sufficient to power the set-up. The first scenario is a simple energy balance - the energy that flows into the cooler should ideally be removed from the cooler by the thermoelectric modules. The energy in can be found with the following equation:Where Q’ is the total heat in from the surrounding environment, Ts is the surface temperature of the cooler (assuming that the surface temperature is roughly equal to the surrounding air temperature), and Ti is equal to the inner temperature of the cooler, which is equal to the phase change temperature of the phase change material. The second scenario requires knowing how much daylight is available to charge the vaccine carrier using the solar panel, along with the specific heat capacities of the phase change material and vaccine, modeled here as water, and the latent heat of fusion of the phase change material. By finding the energy required to cool the phase change material and vaccine to the temperature of phase change and to freeze the phase change material, it can be determined if the selected thermoelectric module is capable of handling these loads, in addition to the heat load in:AndWhere Ecool is the energy required to cool the phase change material and the vaccine; Efreeze is the energy required to freeze the phase change material, m is the mass of the specified material; Cp is the specific heat of the specified material, and hfg is the specific enthalpy of the phase change material. By summing these, and dividing them by the available daylight time, in seconds, the group found the required wattage to cool and freeze the respective liquids. By adding the steady-state heat into the cooler, the group found the required heat load for the thermoelectric modules:Where Q’req is the required heat draw of the thermoelectric modules, and Q’ss is the steady state heat in.The third scenario is used to find the time it takes to chill and freeze the phase change material and vaccine when the thermoelectric modules are operating at their peak power draw. Each thermoelectric module has a peak amount of power it can transmit, which is a function of the voltage applied and the temperature differential. By subtracting the power required to cool the modules in steady state, and dividing the energy required to cool and freeze the liquids by the remainder, the time it takes to carry out this process can be determined:It should be noted that for both the second and third scenarios, the temperature that the vaccine is cooled from should not exceed 8℃. Additionally, the vaccine should not be placed in a carrier that is above the acceptable temperature range to avoid spoilage; therefore, the phase change material should not need to be cooled down from more than 8℃. The fourth scenario is used to determine how much time it would take the vaccine to spoil when there is no electricity to run the thermoelectric coolers (i.e. there is insufficient sunlight and the battery-backups are depleted). The energy it takes to melt the phase change materials and spoil the vaccine should be approximately equal to the energy it takes to cool the vaccine and PCM from 8℃. Thus, determining the time it takes to spoil the vaccine can be found by dividing the energy required to spoil the vaccine by the steady state heat into the cooler:Of course, this makes the assumption that the external temperature does not change. In reality, the external temperature is always fluctuating, so this cooler is designed to operate at extreme conditions; the lower the external temperature, the longer it will take the vaccine to spoil due to the decreased steady-state heat in. The fifth and last scenario used to design the thermoelectric cooler is to determine how long the battery life is under steady-state conditions. Each battery manufacturer releases specifications about how many amp-hours a battery can last for under certain amperages; by relating amp hours to current draw from the battery, it can be determined how long a battery with a full charge would be able to supply cooling to the thermoelectric modules. Using this information, suitable batteries and solar panels can be selected based on the power requirements of the cooler. Back loading can be adjusted through the use of adjustable backpack straps to maximize user comfort for a wide range of body types.After using the Excel optimization function, an updated design was selected. The updated design uses four thermoelectric coolers instead of two. Two sets of two coolers are placed back to front in order to lower the temperature difference across each cooler. This allows each cooler to operate more efficiently and handle a larger heat load.Additionally, the amount of phase change material was increased from approximately 2.5 liters to 6.8 liters. The extra phase change material allows for more energy to be absorbed during the phase change. To compensate for the extra volume taken up by the phase change material and keep the cooler within the size requirements, some of the insulation was removed. It was determined by the optimization study that, provided the phase change material initially started completely frozen, the time until vaccine spoilage was much longer. However, some insulation was still required in order to reduce the amount of heat transferred to the phase change material, and because it is less dense and therefore less heavy than the insulation (780 kg/m^3 vs 100 kg/m^3, respectively).The improvements in the design can be seen when comparing the spoilage time of the original design with the optimized design:Figure SEQ Figure \* ARABIC 1: Spoilage Time ComparisonPrototype Fabrication PlanThe following prototype fabrication plan will serve as a timeline for building, as well as addressing possible manufacturing issues that may be encountered.Overview Prototyping is the design verification phase of Product Development which is used to demonstrate and prove certain aspects of a design. It is the phase where the team will take this project from the virtual world into the physical world. There are many different levels of prototyping with some models consisting of basic mock ups made of duct tape and wire while others are highly polished fragile pieces of show and tell. For the purpose of this project, the team aims to build a prototype which will be a fully functional representation of the final product, with the only discrepancy being in the fit and finish. Any quality issues that might exist could be corrected once a product like this enters a large scale manufacturing phase where parts can be injection molded or die casted to precise design specifications rather than cut and pasted together as is planned. Through phases one to three, the team felt it was not necessary to build any mock-ups or fabricated prototypes as the final product relies on the use of several expensive components packaged into a fairly simple design. Throughout the final prototyping process; however, the team will test and analyze the individual components before final assembly to ensure proper functionality. While all of the theoretical data that the team has gathered thus far proves very promising, it will be necessary to build this prototype in order to verify its performance. The team does not anticipate any radical design improvements going into the fabrication phase; however, if this is the case, our timeline should allow for any necessary changes to our final product. The team does not expect any issues with the manufacturing, as the geometry and assembly procedures are fairly simple. The most difficult part of the manufacturing process will be the installation of the heat pipes and heat sink. Though the drawings are finalized for the inner components, since the heat pipes need to be custom sized, any discrepancies will cause an imperfect fit which risks breaking the wick within the pipes rendering them useless. Because of this and the fact that they are expensive, the team plans to assemble the rest of the refrigerator before ordering and installing the heat pipes. The refrigerator will be built from the inside to the outside so that shells can be layered on top of each other. This will ensure that the components will fit snug with one another if any discrepancies arise between the drawings and the final cut pieces. The following sections will discuss the overview, shaping, and assembly of all major physical and electrical components. Major Components: Overview/Shaping/AssemblyAt this moment the team is in the final process of placing orders for all of the major components which include the aluminum, HDPE, Polystyrene, and Phase Change packs which will make up the bulk of the container. Almost all components in the refrigerator will be stationary. The assembly will primarily consist of cutting the HDPE and aluminum sheets to the appropriate dimensions (via band saw). The aluminum sections will either be welded or fixated together via brackets depending on the availability of spot welding. The polystyrene insulation need only be cut to fit in its space and placed. The images below represent how the team will cut the HDPE and aluminum sheets. As can be seen in the following figures, there is just enough left over material in each sheet to account for the material lost from cutting. Figure SEQ Figure \* ARABIC 2: HDPE cuts (24”x48” + 12”x 24” sheets)Figure SEQ Figure \* ARABIC 3: First 24” x 48” HDPE cut linesFigure SEQ Figure \* ARABIC 4: Second 24” x 48” HDPE cut linesFigure SEQ Figure \* ARABIC 5: 12” x 24” HDPE cut linesFigure SEQ Figure \* ARABIC 6: Aluminum cuts (24” x 24” sheets)Figure SEQ Figure \* ARABIC 7: 24” x 24” Aluminum cut linesFigure SEQ Figure \* ARABIC 8: 24” x 48” Aluminum cut linesElectrical Components: Overview & AssemblyThe appropriate 12 volt battery was selected in conjunction with a 50 watt portable solar panel which includes a 10 amp PWM charger controller for this project. This controller is an essential part of the overall system as it regulates the voltage/current coming from the solar panels to keep the battery from overcharging. For most controllers this is done through a 3-stage charge cycle that involves bulking, absorption and floating. During the bulk phase of the cycle, the voltage gradually rises to the bulk level (14.4 to 14.6 volts) while the battery will draw the maximum current. When the bulk level voltage is reached the absorption stage begins [1]. During this phase, the voltage is maintained at bulk level for a specific time while the current gradually tapers off as the batteries charge up as can be seen below.Figure SEQ Figure \* ARABIC 9: 3-Stage Charge CycleAfter this point, since the controller is a PWM model (pulse with modulation) the float stage is different. Instead of a steady output from the controller, it sends out a series of short charging pulses to the battery like a rapid on-off switch. The controller constantly checks the state of the battery to determine how fast to send pulses, and how long the pulses should be. This method of float charging is quite popular and effective which is why it was chosen for this project. Controllers are also extremely important as most 12 volt panels actually put out about 16 to 20 volts which can damage the battery if unregulated. The reason that these panels are advertised as 12 volts yet put out roughly 17 is because they are accounting for the imperfect conditions that might exist, i.e. cloud cover, haze, or high temperatures. A fully charged 12 volt battery is around 12.7 volts at rest (around 13.6 to 14.4 under charge), so the panel has to put out at least that much under worst case scenarios [2]. The figure below shows a typical wiring scheme between the solar panel, controller and charger. Figure SEQ Figure \* ARABIC 10: Wiring scheme for solar panelThe figure above shows an accurate model to what the team plans on building with the exemption of the 12V power inverter which is used to convert direct current from the battery to alternating current which is readily used by most technologies. However, thermoelectric coolers use direct current so this costly component will not be necessary. The science behind this is that in order to keep heat pumping in the same direction, the polarity of the applied voltage must be maintained. This means that some form of direct current is required. If alternating current was applied instead, the polarity would change each half cycle, and so would the direction of heat pumping. As a result, the net amount of heat removed would be zero and both sides of the system would get warmer from the I^2*R dissipation with the Peltier device [3].It was determined in phase 3 that two 50 watt panels would be needed in order to provide transient cooling. However, due to cost limitations the team is restricted to the purchase of only one of these panels which should be enough to provide steady state cooling. The team plans on working around this drawback in the testing phase by both manually charging the battery with a 12 volt 500 mA/hr charger in conjunction with providing artificial light to the solar panel indoors during dark hours to be discussed later on.With the power supply in place the next phase would be to figure out how to transfer the energy from the battery to the thermoelectric coolers, temperature sensors, heat sink fan, and LED display. This will be accomplished through the use of an Arduino Uno board. These boards (in addition to all other electrical components) are capable of running off of a DC power source, so again a power inverter is not needed, saving weight and money. The programming for the board has not been completed yet as the team has not acquired the components. A basic flow diagram showing all the major components and inter-relationships can be seen below:Figure SEQ Figure \* ARABIC 11: Flow DiagramThough the team does not have the program written yet for controlling the thermoelectric modules the architecture is fairly basic. With power available, the temperature sensors will relay information to the Arduino board. The program will then decide what to do based on the highest recorded temperature from the 4 sensors. If any of the sensors read above the 7 degree Celsius limit, all four thermoelectric modules will be commanded to turn on. The heat sink fan will be programmed such that whenever a TEC module is working, it will automatically run. Once the highest recorded temperature drops below a certain threshold that was discovered in Phase 3, the TEC’s and fan will be commanded off. The LED display on the top of the unit will display the highest temp sensor reading and indicate whether TECs are running or not. The solar panel to be used for this project measures 21.6 x 26.7 x 1.2 inches and weighs 11 pounds. As such, the team anticipates some complications with mounting this panel to the main infrastructure of the refrigerator. The panel is said to come supplied with several Z brackets for mounting; however, the team will have to explore additional mounting possibilities once we’ve physically received it in order to make the panel easily detachable for proper setup and angle to sunlight. The PMW controller comes with screws which will allow it to be anchored to either the panel or close to the battery. The mounting of this component is also an unknown as the team does not know the exact dimensions of said controller. The battery measures exactly 5.95 x 3.86 x 3.74 inches and weighs 9.68 pounds. The dimensions are small enough to be mounted at the bottom of the cooler depicted in the figure below.Figure SEQ Figure \* ARABIC 12: 3-D Model of CoolerLooking above, imagining that the section that is highlighted in red is the portion that would be in contact with the travelers back, the battery would be located at the bottom of this half. However, with the battery attached (via brackets and screws), this could potentially be too much weight in an awkward position for one person to carry. As such, this aspect of the design will need to be re-evaluated once the main structure is assembled and weight tested. The Arduino board will be mounted at the bottom of the cooler regardless of the battery location. Excess aluminum will be used to shield the board from the environment yet ensuring that the leads from the battery will be easily accessible (depending on the batteries location). Since the cooler is to be built from the inside out, the first electronics that will need to be positioned are the temperature sensors. These sensors will be fixated at the four corners within the interior volume of the HDPE with epoxy. Port holes will be drilled through the HDPE to provide tunnels for the necessary wiring to flow through back to the Arduino board. The thermoelectric modules in addition to the aluminum tabs and gaskets will be mounted to the middle HDPE component using epoxy. The heat sink fan will be screwed to the top of the cooler to come into contact with the copper plate. All wiring will run down through the main half of the cooler to the Arduino board via a small hollowed out path. The LED display will sit next to the heat sink fan and all wiring will run through the same channel.CostThe table below shows all of the major components that will be used in the construction of the team’s prototype. The last column indicates whether the team decided to purchase or borrow said components from engineering labs within the school. Some components are designated with “buy/borrow” which means that it is unsure yet whether the part is available on campus for second hand use. Ideally, the more parts borrowed would be beneficial in lowering the total cost; however, the team anticipates that the “buy/borrow” components might need to be purchased in a worst case scenario. Since there are no moving parts (except for the heat sink fan), the team is not concerned with components breaking. As such, only the exact number of components needed will be purchased in order to remain within budget. If any issues arise during construction, the team will aim to use second hand parts to complete fabrication/testing. MaterialDescriptionCostQTYTotal Cost (includes shipping & tax)Buy, Borrow, or either/orAluminum.040” thick 3003 Aluminum sheet (24” x 24”)$13.683$41.04BuyHigh Density Polyethylene0.187” thick HDPE sheet (24” x 48”)0.187” thick HDPE sheet (12” x 24”)$21.26$10.7721$53.29BuyPolystyrene1” thick EcoBox Expanded Polystyrene Foam Sheet 4-pack (24” x 48”) $29.721$29.72BuyPhase Change PackArctic Ice Tundra Series Reusable Cooler Pack$29.992$64.20BuyHeat PipeMade to order - delaying purchase until other parts of cooler have been completed$52$10BuyCopper heat sinkIntel 100W heat sink$02$0BorrowHeat sink fanIntel heat sink fan$01$0BorrowThermoelectric ModuleHP-127-1.4-1.5-74 Unpotted TEC$28.804$122.11BuyRubber Gasket12” x 12” 1/32” thick silicone sheet$11.372$22.74BuyBatteryGruber 12 Volt, 12 Amp Hour (AH) Battery$39.441$39.44Buy/BorrowBattery charger12 Volt 500 MA/HR Battery Charger - Dual Stage$23.401$23.40Buy/Borrow50 Watt Solar Panel50 Watt Renogy Starter Polycrystalline Solar Panel Kit$129.991$129.99BuyTemperature SensorTMP36 - Temperature Sensors$5.954$23.80BorrowLED display0.56” 4 digit LED display$13.491$13.49Buy/BorrowArduino Uno ControlN/A$27.951$27.95BorrowArduino Power SupplyAC/DC Adapter charger cord plug - 9V 650 mA$9.691$9.69BorrowDrawbolt LatchLatch for securing two major halves$2.792$5.58Buy/BorrowHingesHinge for halves to articulate on$1.972$3.94Buy/BorrowEpoxy AdhesiveAdhesives for securing all components not welded/screwed$15.671$15.67BuyMiscellaneous WiringWiring for Arduino board---BorrowTOTAL (assuming buy/borrow is purchased)$574.61 TOTAL (assuming buy/borrow is borrowed)$488.76 The second to last row in the table above indicates the total cost for when the items listed as “buy/borrow” are considered purchased in the case that the team was unable to accrue the parts from campus. This represents the maximum cost the team anticipates for this project and was found to be $574.61. The last row indicates the total cost for when the items listed “buy/borrowed” are found at school or for free. The items listed as “borrow” are not added to the total cost for either of the last two rows as these items will be used for free. As such the cheapest fabrication of this project will cost the team $488.76, an almost $100 difference from the previous case. Seeing as both cases are within the $700 budget limit, the team aims to move forward with ordering the necessary parts.**The timeline for building can be found in the Gantt chart at the end of this report.Performance TestingThe following outlines the approach to verifying that the product meets desired specifications and will serve as an independent testing document.OverviewVaccine carriers are used to transport temperature sensitive vials over extended periods of time. The time that a vaccine carrier can maintain the target temperature is known as its Cold Life. This study will observe whether or not the product can reach the target temperature range as well as how long it can maintain the target temperature. The target Cold Life will be 96 hours or more at a temperature range of 2 to 8 degrees Celsius (with 5 degrees Celsius being the desired average temperature). To account for varying climates the controls in this study will be the ambient temperature and solar exposure. Equipmentprototype vaccine carriersolar panelsbatterythermal sensorsolar simulatortemperature controlled environmentelectronic timerfreezer thermometerlaptop with Arduino board data loggerBaseline AssumptionsDue to budget and time limits, assumptions must be made for the scope of the testing procedure relating to; climate, sunlight, and manufacturing quality. These assumptions are addressed below.The product will be marketed firstly towards countries in South Africa where average daylight is 12 hours per day and temperatures can range from 85 degrees Fahrenheit to 106 degrees Fahrenheit. Due to the variable nature of day to day operation testing will be conducted at a stable temperature throughout the entirety of one test. Multiple tests will be conducted at different ambient temperatures. However, humidity will not be factored in for these tests due to the lack of a climate controlled environment. The use of a solar simulator will be used to test the solar panels. Direct sunlight conditions will be assumed with exposure being controlled by an electronic timer set to simulate a 12 hour daylight cycle. Other assumptions about equipment and the manufacturing process.Equipment bought by third party suppliers will not be tested due to time constraints and product specifications will be assumed to be true unless proven otherwise. For example, solar panels with a 50W power rating will be assumed to be working at optimal conditions although it is common for power ratings to be off slightly due to quality variance. Due to the nature of the product, there may be human error during the assembly of the product, effecting insulation and efficiency. A heat leak test may be performed at a later date if necessary. Overall, testing will assume direct sunlight and non-varying climate during the course of each test. Test ScenarioAs stated in the previous section, testing will be conducted at different ambient temperatures and will measure the cold life of the product. A single test run will end once the internal temperature of the vaccine carrier goes over 8 degrees Fahrenheit or reaches the target cold life.SetupPrior to each test the Phase Change Material must be frozen to the target temperature range and verified using a calibrated thermometer. The solar simulator will be positioned to optimize solar panel exposure as well as plugged into an electronic timer. The electronic timer will be set to shut off power to the solar simulator every 12 hours in order to simulate day and night. Day cycle should coincide with actual day time. Testing shall be performed in a temperature controlled environment (room with thermostat control). Room should avoid disturbance. A laptop shall be connected to the Arduino board to record data using a data logger in the form of a .txt file. Scenario 0: Measuring Cooling TimeThe vaccine carrier will undergo cooling from ambient temperature to 2 degrees Fahrenheit while unloaded. The time it takes to reach this temperature will be recorded and will be defined as the cooling time. Cooling time is not a primary focus of the product however a shorter cooling time will be ideal as well as being valuable information for planning further testing. Note: This test does not include the use of PCM.Scenario 1: Cold Life without PowerTo measure the cold life without power, the batteries should be removed from the vaccine carrier (with PCM) once the target temperature has been reached. The vaccine carrier must then be left in a room with the desired ambient temperature until the target temperature range is breached. Scenario 2: Cold Life with PowerTo measure cold life with a power source, the vaccine carrier must have a fully charged battery and PCMs before unplugging from a power source. Solar panels must also be connected and the solar simulator turned on. The vaccine carrier must then be left in a room with the desired ambient temperature until the target temperature range is breached. Average temperature will also be recorded in this step to observe the programming of the Arduino board, which should regulate when to send power to the vaccine carrier and when to store energy.Scenario 3: Outdoor SimulationThe final scenario will test the vaccine carrier under real world application with a variable climate. The vaccine carrier must have a fully charged battery and PCMs before unplugging from a power source. Solar panels must also be connected and positioned away from shade as best possible. To avoid shade the test will most likely be conducted in an open space with good exposure, like a roof. The vaccine carrier must then be left alone until the target range is breached. An additional thermal sensor must be placed outside of the vaccine carrier in order to track temperature. This sensor can be substituted by another temperature recording device.Testing ResultsThe outcome of each test will be recorded using the template. Additionally, the information from the data logger may be presented in the from a chart or table tracking performance for each test.Scenario 0Ambient Temperature (Fahrenheit)Cooling Time (Seconds)70?80?90?Average Cooling Time?Scenario 1Ambient Temperature (Fahrenheit)Cold Life (Hours)70?80?90?Average Cold Life?Scenario 2Ambient Temperature (Fahrenheit)Solar Simulator Exposure (Hours)Average Running Temperature (Fahrenheit)Cold Life (Hours)7012??8012??9012??Average ?Scenario 3Trial #Average Ambient Temperature (Fahrenheit)Sunlight Exposure (Hours)*Cold Life (Hours)1???2???3???Average Cold Life?*sunlight exposure will be determined using weather records such as Actions based on the major comments and suggestions from ME 423 panel. During the phase three presentation, some questions were brought up regarding the heat pipes used to remove heat from the heat exchanger. Variable conductance heat pipes with a temperature range of between 2 and 50 degrees Celsius were chosen. The variable conductance heat pipe allows for heat transfer at a wide range of temperatures. Because these parts are uniquely shaped and must be made to order, the team decided to hold off ordering them until preliminary construction of the cooler is finished, in case any further changes are made.Gantt chartBelow is the Gantt chart that the team is scheduled to follow for phase 4 of this project beginning with reviewing all previous comments made from the design panel to the final testing and analysis of the prototype, the team is confident that this timeline is reasonable for accomplishing all goals, objectives and deliverables defined throughout this report. In addition, the materials and components are all within the team’s $700 budget so the cost of the prototype is reasonable for our purposes. Figure SEQ Figure \* ARABIC 13: Gantt chartWorks Cited ................
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