Final Design

Figure 1. A schematic of the dermal cooling vest is shown, with the method of transferring heat- embedded tubbing.

Figure 2. The radiator, fans, battery and water channels with peltier plates are shown.

Figure 3. A schematic is shown of the vest with with the fans and radiator removed, leaving the pumps and tubing visible.

Design Solution

The dermal cooling system uses Peltier devices to cool a circulating fluid throughout a network of tubes surrounding the user’s torso. Peltier devices are thin plates that use electrical currents to create a temperature difference between each side of the plate. Water channels enclose the Peltier device’s hot and cold sides, allowing them to exchange thermal energy with the flowing water on either side (see Figure 7). The heated flow is pumped through a radiator that uses fans to expel heat away from the system. A second pump circulates the cooled flow through 36 tubes that wrap around the user’s torso and absorb heat from the body, as shown in Figures 1 and 4. The vest component consists of a mesh undervest in which the cooling tubes are woven and the neoprene outer shell. This shell is responsible for compressing the tubing against the body and insulating the tubes from the exterior environment. To control the vest, an on/off button is used to run the system at its maximum cooling potential.

Figure 4. The first vest layer with the water filled tubes is shown above,

Figure 5. The outer shell of the dermal cooling vest provides compression without trapping heat.

Figure 6. The wooden frame houses the components necessary for the vest to run such as the radiator, fans, peltier plates, and battery.

Figure 7. Depicts a basic representation of the vest functionality. The cold water absorbs heat from the body; it is cooled via Peltier devices. A radiator expels the body and Peltier generated heat away from the body.

Final Results

Analysis and optimization of the dermal cooling system increased its cooling capacity from approximately 100W to 220W, which is 70W greater than the desired cooling of 150W. This increase in performance can be attributed to a decreased thermal resistance of the water channels and operating at the optimized flow rate. The model of Peltier devices was also changed and the quantity was increased from 4 to 8. The working prototype runs for approximately 30 minutes and weighs 14 pounds. While the weight of the system was kept under the 15-pound limit, it became clear through testing that the system is too heavy to remain comfortable for prolonged usage. Controlling the cooling with an on/off switch proved to be effective, however multiple settings of cooling would be preferred in future iterations of the system. A laser cut piece of plywood and brackets creates the frame that contains the cooling hardware. In the process of designing and manufacturing the frame, the final and compacted water channel design did not yet exist, therefore there is excess space in the frame. With the current hardware, the frame could easily be compacted to allow for a more ergonomic design.

Sauna Test Results

Figure 8. Temperature of the coolant at the inlet and outlet of the cooling system over time.

The overall temperature of the system increased from about 90 degrees to 94 degrees in the first 6 minutes. At this point, there is an irregularity in the data, most likely caused by the fans being inadvertently shifted, causing the heat being expelled from the radiator to reenter into the system. The data returns to a more expected trend at about 9 minutes which likely means that the fans position was corrected. The irregularity in the data may also be due to the water content in the sauna increasing at that time, suggesting the vest performs better in humid environments.

Figure 9. Difference between the temperature of the inlet and outlet of the cooling system over time.

The difference between the inlet and outlet temperatures, or the delta, shows the effectiveness of the cooling system. The larger the difference, the more heat is being removed between the inlet and outlet, so the more cooling that is being created. As shown in the Figure, the delta decreases from 2 minutes until about 6 minutes. This is expected as the Peltier plats are more effective at cooling initially. The large spike in effectiveness at about 8 minutes may be a result of the fan shifting or water being added to the sauna.

Space Heater Test Results

Figure 10. Temperature of the coolant at the inlet and outlet of the cooling system over time.

As time went on, the overall temperature of the water flowing through the vest increased, but the delta between the inlet and outlet also grew. There is an unexpected jump in the inlet data at the beginning possibly due to initial movements.

Figure 11. Difference between the temperature of the inlet and outlet of the cooling system over time.

Unlike the sauna test, as time went on, the delta increased showing promising results, suggesting that the vest performs slightly better at less extreme temperatures.

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