Integrated System Build & Test
Table of Contents
Team Vision for Integrated System Build & Test PhaseThe team planned to complete and completed the following during this phase:
- Determined the most effective insulative and fabric materials
- Ordered insulative and fabric materials for the prototype
- Ordered second sealer for packaging of phase change materials
- Determined most effect phase change material to be used in the prototype
The team also decided to push back initial human testing until the next phase.
Updated Bill of Materials (BOM)here.
Test Results Summary
The plots below detail the results of the insulation and fabric comparison tests. These tests were run in order to determine the ideal insulation and fabric since the DOE was inconclusive.
The set-up included the insulation or fabric sample placed on the hot plate, which was set to 37 degrees Celsius. A temperature sensor was placed on either side of the insulation or fabric sample to measure the temperature difference across the sample. The criteria for the ideal sample were as follows:
Insulation: Greatest temperature difference across sample to indicate highest level of insulation. In the final design, the insulation will ensure that a majority of the cooling effect is not lost to the outside environment, therefore the insulation should have a large temperature gradient across it.
Fabric: Least temperature difference across sample to indicate ability for heat transfer through the material. In the final design, heat transfer will occur across the fabric between the body and the cooling device, so to ensure ideal cooling, the fabric should not have a large temperature gradient across it.
After analyzing these test results, the Thinsulate J250 was determined to be the best insulation and the Mesh was determined to be the best fabric. After consulting with the manufacturer of the insulation (3M) it was determined that Thinsulate J250 is currently out of stock and the shortest possible lead time for more would be at least 16 weeks. At this point, it was decided to move forward with the Thinsulate 150 in order to keep the testing moving, but future iterations of this project will want to consider using Thinsulate J250 in order to increase the insulation ability.
To determine the effectiveness of each PCM, each material was melted and frozen into an insulated container (shown above) and then slowly melted while the temperature profile was recorded by 4 temperature probes embedded into the frozen material. Each of the 4 probes recorded their own, slightly different data as shown below on the left plot. To make the data more useable and comparable to the respective plots of the other PCMs, the different data sets were averaged, shown on the curve to the right.
After averaging the different data sets for each of the PCM tests, the averaged curves were plotted on a single diagram to best compare the results, shown below.
In this plot, the preferred PCM would melt at the lowest possible temperature and stay low for the longest period of time, maximizing the rate of heat transfer due to the temperature gradient, and maximizing the length of the heat transfer. Mathematically speaking, the ideal substance would have a temperature profile that maximizes the area between the curve and the horizontal line at 37 Degrees Celsius (the temperature of the hot plate). As is clearly seen in the above plot, Puretemp25 and Puretemp27 were by far the least effective, melting in less than 2000 seconds and rapidly warming. Nexotherm had a noticeably better temperature profile, lasting nearly 9000 seconds, but price, availability, and corporate requirements make its use prohibitive. Puretemp23 was chosen as the final material for the prototype, due to its lower melting temperature and relatively higher specific heats. These results match our initial calculations well; Puretemp 23 was the second best PCM (Puretemp 24 was superior but unavailable for purchase) with regards to net energy storage capabilities starting from room temperature, followed by Puretemp 25 and Puretemp 27. No specifications were provided for Nexotherm, so calculations were not possible.
Preliminary heat sealing of the chosen PCM was accomplished successfully via the heat sealer and vacuum sealer shown below. These devices will be utilized to build the final prototype.
Risk and Problem Tracking
Functional Demo MaterialsMeeting minutes from the Integrated System Build & Test Demo will be posted once the team has discussed and allocated action items.
Plans for next phase
For the full updated timeline document, click here.
Below is an overview of the project timeline and Gantt chart for MSDII. Click the picture to view it larger and the zoom in and out tools will allow movement around the document for a closer look at specific phases.
The following are the team's individual 3-week plans for the next phase as well as the activities accomplished during the past phase: