156B Week 6

Overview of Status of Analysis, Design, Fabrication, Tests, etc.

• All major tests with lab bench power supply are completed and the performance of the system is validated

• Vest is fully assembled

• All major components purchased

• Vest is ready to be converted into a portable system

Accomplishments from Previous Week

• Finished Tube Routing on first vest

• Purchase remaining peltiers

• Completed Testing With 2 Peltiers - Tested in high heat (35 °C, 95°F)

  • • Qualitatively, it is significantly cooler with the vest.

    • Power draw in line with expectations

    • Cooling efficiency a bit lower than expected,

      • • COP ~2 (40W power draw for two peltiers)

        • Likely due to a lack of compression, thick shirt, shorter tubing on prototype 1, and lack of insulation from ambient.

• Met with Abhijith Karkisaval Ganapati to discuss Ansys.

  • • Our model looked good; residuals are converging

    • He suggested that we add parameters to make optimizations faster

    • We will continue to be in contact with him

Goals for Next Week (list names after each item). Use specific and measurable objectives.

• Design and Build Backpack Mounting - Josh, Edgar, Tyler

• Request Refunds - All

• Test Neoprene Vest and Space Blanket - Edgar, Tyler, Vlad

• Test portable power management systems - Vlad

  • • Battery

    • Buck Converter

    • Low Voltage Cutoff

• Route New Tube Vest - Tyler

• Calculate Log Mean Temperature Difference - Jocelyne, Josh

• Ansys Analysis - Jocelyne, Josh

  • • Channel Block

    • Jet Block

    • Tubing

Sponsor Comments from Last Meeting and Actions Taken to Address these Comments

Zoom - 02/05/2021

• The sponsor was impressed with first prototype test

  • • We performed a full prototype test on Tuesday (2/10)

• The sponsor mentioned that we need to avoid kinks in the tubing

  • • We can use a piece of rubber/plastic shielding on the shoulders to avoid kinks in the tubing

• The sponsor advised us that a lot of heat is generated in the upper torso

  • • We will increase the density of tubing in the upper torso to ensure adequate cooling

• The sponsor indicated that he will follow up with RIMAC to see if we can find a location for high heat testing

Instructor Comments from Last Meeting and Actions Taken to Address these Comments

Zoom (Presentation Feedback) - 02/04/2021

• Professor advised that we move the location of the pump to create negative pressure & avoid leaks.

  • • We moved the pump for the second full system test and will continue to keep it in that position.

• Professor advised that we use Ansys more wisely by solving for more complicated issues rather than the simple layout we initially tested

  • • We will be testing variations in the tube layout to make sure that the system still performs as expected.

• Professor advised that we be more clear about variables and results in our presentations and reports to avoid ambiguity.

  • • We will be careful to precisely describe the variables such as power into the TEC, cooling power acheived, etc.

Comments from Other Students in the Class

Zoom (Presentation Feedback) - 02/04/2021

• A student asked if we had considered safety concerns in our design, such as a user falling while wearing the vest.

  • • We will be sure to consider safety while designing the packaging for the backpack that will power the vest. All of the electrical components ( TEC, pumps, battery, radiator) will be contained in the backpack. We are working on the design this week and we will ensure that the critical components are protected from fall damage.

• A student asked about what the possible solutions to preventing vapor migration are.

  • • We have been in contact with John Hamer from Laird Engineered Thermal Systems (the manufacturer we are sourcing from)

    • They stated that the ceramic used in the TEC is impermeable to water and there should be no issue with direct water cooling.

    • They did mention that the perimeter of the TEC is sealed with RTV silicone sealant but that a second sealant would be advised to avoid vapor migration from condensation

Risks and Areas of Concern

• None

Resources or Information Required but not Available

• None

Schedule

• • Upcoming milestone

    • • Will complete the packaging design and begin packaging electronic components

  • Updated Gantt chart link

    • • Screenshot of the most recent updates included below

Budget (list amount spent and amount remaining)

• Neoprene sauna suit, thermal blankets (4) $32.30

• Hose clamps $32.28

• Flexible resin $70.04

• Battery management system $12.67

• 16 AWG wire $14.00

• EC5 male/female connector, voltage protection module $36.56

• 24V to 12V buck converter $16.99

• EC5 male connector $11.84

• Battery charger $51.71

• 15, 1.5 Ohm resistors, alligator clips $43.60

• Nitrile gloves $18.87

• Peltier (2) $296.47

• Amount Remaining: $57.27

Progress on Report and Webpage

• Currently waiting for feedback from instructor and TA