Blog #3 - Capstone 2 - Sept. 24 - Oct. 22, 2021

    There's been an additional 5 tests the team has conducted since our last blog entry. In our 5th test, we configured our Peltier devices to run at 8.0 volts, 6.5 Amps and 7.5 volts, 5.0 Amps, respectively. Figure 1 below shows the results of this test, where lowering the amps resulted in an overall improvement in cooling our main loop by only slightly increasing the temperature of the radiator loop. For this test we applied a heat load to the main loop to simulate the heating effect produced by a person. This was done by connecting a 2 ft section of copper pipe to the main loop and submerging it in a large volume of 20 C water. This applied a heat load of approximately 4-5 W on 0.12 L of liquid which is about 2-3x the heating amount our final system will receive during operation since our final system will contain more liquid.

Figure 1: Cooling the main loop with a heat load applied

    The rest of the tests we conducted, Test 6 thru Test 9, were run at 8 volts and 5.5 Amps. The ability to tune the Peltiers in this manner is due to the addition of the voltage regulator(s) to our electronic system. It has allowed us to improve the performance and efficiency of our system to obtain better results than we initially proposed. The next addition to our system was the copper pipe that we will be implementing/installing in our chair. First we gathered data from using 50/50 Antifreeze with 50 feet of coiled copper piping. The reason we decided to use antifreeze as our working fluid is because we were able lower the temperature of the water in the main loop to below zero, causing it to freeze at about -3 C. This temperature is much lower than necessary, but it is possible for the system to reach it which would damage the system's components.

    To simulate the integration of the pipe to the chair, we sandwiched it between two polyurethane foam cushions. Figure 2 showcased below shows the results from Test 6 and Test 7, in which we cooled and heated the water, respectively.

 

Figure 2: Exploded view of our current system

Figure 3: Copper pipe and foam padding

Figure 4: Cooling and heating tests on 50ft of well insulated copper pipe

    We found during heating the temperature can increase to a point where it would be uncomfortable and possibly even dangerous to the user and system. The team decided the best solution is to use a temperature regulator device. We implemented a thermostat controller that can be configured to turn off the system once it reaches a certain temperature and restart once the temperature drops below a set temperature below the cut-off.

  Figure 5: Thermostat controller

    As of October 16, 2021, we began implementing our system to the chair. We started to plan the configuration of our components to the undercarriage of the chair. Also, we began bending the copper pipe section to integrate it inside the cushions of the chair. We have tested to see if the cooling and heating effect produced by the pipe can be felt through the leather when a person sits on it. Our preliminary testing has shown the surface temperature can be brought to the desired degree. Although, we need to better integrate the pipe into the cushion so it is not as  noticeable while sitting on it. We plan to use adhesive to keep the pipe set in the cushion. These adjustments and more will be done in the next week, so we can have our full system ready to be demonstrated by our demonstration time Thursday, October 28th.