Notice: The page only covers some aspects of the job and project, as more detailed information is restricted under an NDA.

Personal Cooling Device Development - Background

This job initially started as a senior design project in which the goal was to design and build a personal cooling device. After that quarter, I was offered a position as the lead design engineer in which I would continue working on the project both independently and as the lead on subsequent teams. This project and job were also during the time of the Covid-19 pandemic and so all design and manufacture was done with very limited access to university resources, and with some team members working exclusively remotely.

Action Plan - Round 1

1. Determine minimum and maximum cooling requirements

2. Investigate a broad range of heat transport and heat pump technologies

3. Investigate existing products that attempt to resolve the same or similar issues

4. Select the appropriate technology based on cooling, size, electrical power, and noise considerations.

5. Plan the next design, validation, and manufacture stages

Round 1 Findings and Decisions

• Cooling requirements were calculated and the boundaries of safe cooling of a person were investigated and documented

• Current consumer products that attempt to tackle personal cooling were investigated

  • Most of the less expensive options do not use active cooling and would only be able to cool a small amount of heat

  • The more expensive options have a lot of room for improvement in many of the stages of removing heat, and are bulky and heavy

• During the course of our technology investigation many useful research papers were found that were later used in development and validation

• Based on our investigations, we then selected a heat transport and also a heat pump technology

Action Plan - Round 2

1. Determine key performance characteristics to be measured for the heat transport and heat pump systems (Heat power, C.O.P, Thermal Resistance)

2. Design heat transport and heat pump systems and determine the expected performance characteristics

3. Design validation experiments to test subcomponents and small scale subsystems

4. Test subcomponents and small scale subsystems

5. If subcomponents and small scale subsystems are operating within the expected performance range, build a prototype of the entire system

Action Plan - Round 3

1. Validate the performance of the entire system

   • If performance and operation is within expected ranges and is good: Plan manufacturing stages

   • Else: Determine sources of performance loss, iterate on design, build, and repeat Action Plan - Round 2 and 3

Challenges

• Due to the covid lockdown measures access to university resources was limited, and as the project budget was limited, much of the validation equipment that was used also had to be designed and built in house in parallel with the project itself.

• Due to the lack of a dedicated workspace and due to the fact that some team members could only work remotely, proper planning and work load management was critical to ensuring that the goals for each quarter were reached. Scheduling regular meeting times to discuss design, assemble, and test with the appropriate team members ensured that all tasks were finished on time.

Datalogger (Solo design and build)

In order to characterize the performance of the system, accurate temperature and flow measurements were required. Inexpensive off the shelf temperature measurement systems are inaccurate and do not include a mechanism to log temperature over a long period of time, and there are also no inexpensive off the shelf systems that log both temperature and flow rate.

Since off the shelf systems that could fulfill the necessary requirements are expensive, it was decided that building a datalogger using an arduino microcontroller and custom assembled temperature probes was the best course of action.

Specifications

1. Ideally, less than 0.1 °C delta between the various temperature probes in the range of 10 °C to 50 °C, when reading the same temperature

2. Temperature probes should have an accuracy of less than 1 °C over the above listed temperature range

3. Flow sensor should ideally have less than a 10% error

4. The datalogger must log 6 temperature values and 2 flow rate values at most within half a second, and at least every 5 seconds

5. Must be able to operate and log data internally and in a high temperature environments

Result

The datalogger was able to be built to within the specifications listed above by calibrating the purchased components to a higher degree of accuracy than what what is listed by the manufacturers of those components.