156B Week 8

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

• Completed Prototype 1

• Prototype 2 in progress

Accomplishments from Previous Week

• Water Block

  • • Using LMTD, determined that improvements could be made to the water.

    • Ex) a factor of 5 increase in the product h*As would improve thermal resistance from 0.067 °C/W to 0.017 °C/W

• Completed packaging of dermal cooling device

  • • Device ran free from wall power supply - completely battery powered

    • Sponsor tested and approved prototype 1

      • • Feedback from sponsor in 'sponsor comment' section

• Finished CAD and began printing prototype 2 packaging

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

• Ansys - Jocelyne, Josh

  • • Continue working on heat exchange model

• Finish printing and Assemble prototype 2 packaging - Vlad, Edgar, Tyler

  • Add potentiometer

• Assemble prototype 2

Sponsor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)

Zoom - 02/12/2021

• The sponsor advised that we could proceed without an app-based control system

  • • He was going to deliver an app that we would need to integrate into our control system, however, it is not ready in time

    • He is satisfied with our current solution of incorporating a potentiometer to adjust voltage

      • • We are currently working on installing a potentiometer that will be fitted on the backpack strap for easy access

• The sponsor asked about the status of the water connections

  • • We let him know that prototype 1 is currently connected to the backpack without quick disconnect fittings

    • The quick-disconnect fittings have just arrived today and are ready for assembly for prototype 2

• The sponsor also recommended Ball-lock fittings if the quick disconnect fittings pose an issue

In-Person Meeting - 02/23/2021

• We invited the sponsor to meet with us in order to try on the 1st prototype and give us some early feedback

• The sponsor approved of the two-part vest + backpack design, which makes putting on the vest simple

• He tried the system on with an estimated cooling of ~80 W (which should last ~2 hours)

  • • He advised that he would like us to proceed with more cooling, even if it means sacrificing battery life

• He was impressed with how quiet the system is (fans are rated at 25.1 dB)

• He would like us to focus on getting the prototype as polished as possible and to work on optimizations from this point on

Instructor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)

Zoom - 02/18/2021

• We talked about LMTD with Professor. He performed a quick calculation and validated our efforts in optimizing the water block.

  • • We met one more time with Professor Tustaniwskyj and performed our own calculation.

• Professor asked about our power supply. He suggests that we use PWM and calculate its efficiency and compare its efficiency to the efficiency of a buck converter.

  • • We discussed this further the sponsor and he said that at the moment, using a buck converter would be fine. We will add this to our design recommendations for the future.

• Professor Tustaniwskyj suggested that we place the Peltiers in series.

  • • The Peltiers were rewired to be series.

• The Professor said that performing skin temperature tests was a good idea. He suggested that we perform the test as close to ASTM International Standard F2300-10, a standard testing method that uses physiological testing on volunteers to quantify the effects of personal cooling garments.

  • • We met with our sponsor to further discuss performing this test. Dr. Suarez, thinks that this is a good test to perform. Since we have already used most of our budget, Dr. Suarez wants us run all further purchases by him.

Zoom - 02/22/2021

• We met with Professor to discuss the LMTD calculation he wanted us to perform. He explained that we should calculate thermal resistance and see how changing values affect thermal resistance.

  • • We performed calculations. See graphs above.

Comments from Other Students in the Class (indicate date of comments and if via email or in person)

• None.

Risks and Areas of Concern

• None.

Resources or Information Required but not Available

• None.

Schedule

• • Upcoming milestone

    • • Will complete a fully portable system test under high temperature conditions

        • • Plan A - Sauna test

          • Plan B - Attic testing at 95°C, similar to previous experiments

  • Updated Gantt chart link

    • • Screenshot of the most recent updates included below

Budget (list amount spent and amount remaining)

• N/A

• Amount Remaining: $35.77

Progress on Report and Webpage

• Currently updating and filling out sections of report and website.