Planning, Process, Analysis:
Prototype Testing Procedure:
Goal: The goal for our procedure is to determine how effective each of our thermos. prototypes are at conserving heat of 150ml of boiling water over time. We also needed to stay within a budget and make it aesthetic pleasing.
-Beaker (250 ml)
-150ml of boiling water
Step 1: Plug in hot plate
Step 2: Fill 250ml beaker with 150 ml of lukewarm water from the tap.
Step 3: Put beaker on hot plate and wait until boiling.
Step 4: Check the temperature of the water and record onto data table. Pour the boiling water into the thermos and wait 15 minutes.
Step 5: Test water temperature loss with a thermometer and check the temperature every 5 minutes until a total of 15 minutes have passed. Make any changes to the design if needed and test using the same procedure.
We put the temperature loss over time on to a chart and will graph all three charts on the same graph at the end. This will help us understand what improvements we could make and what helps and what doesn’t help as much as we thought it would. We organized this by labeling and storing our data in a similar place and fashion.
When we made our first prototype, we wanted to use materials that had a low thermal conductivity as these are good insulators. We used a Styrofoam cup and wrapped it in foam underlay so that very little heat would be transferred to the cup. The less conduction means the heat stays in the water rather than transferring to the cup. The biggest change we needed to make was adding a lid. Without a lid the heat was escaping due to convection. Heat rises and without anything to keep it in the cup the temperature was quickly decreasing.
Picture of the prototype:
This prototype added in the lid, which was also made of foam underlay, another great insulator. The water was losing heat because there was nothing to keep it in. Convection was causing the heat to rise. So, when we added the lid, we saw a large difference as the heat wasn’t able to leave the cup.
Picture of Prototype 2:
With the added lid we were able to stop most of the heat loss, but we wanted to add something that would radiate the heat back to the water. So, we decided to add a survival blanket to the lid. The blanket had low thermal conductivity and as it was reflective it radiated heat back to the water. Adding this blanket made a huge difference. We lost way less heat than before.
Picture of prototype 3:
Temperature vs Time Graph:
This is our graph representing the temperature of the water in our thermos’ over a time of 15 minutes, checking the water every 5 minutes.
Starting Temp: 85.5°C
Final Temp: 60.8 °C
Change in Temp: down 24.7 °C
3x Foam insulation squares (total is $0.90 )
Styrofoam cup ($0.85)
5 inches of tape ($0.25)
9 square inches of safety blanket ($0.90)
Picture of final product:
We picked the design to keep as much heat in from every surface of the cup, while paying especially close attention to the lid/top. The reason for surrounding the cup with foam was to limit the spread or transfer of energy to outside of the cup. The foam had a low thermal conductivity (0.03 W/m K) which meant that it will not lose heat energy to conduction and transfer it elsewhere. We put foam all around the cup and the cup itself was also Styrofoam (0.03 W/m K). We put a safety blanket on top of the lid to keep heat in (0.04 W/m K thermal conductivity). We know that heat energy rises, and this is called convection. We also knew that the heat would radiate upwards so having a safety blanket with a low conductivity, but a high reflection would help stop the spread of the heat energy and reflect the radiating heat back into the thermos, limiting heat loss and transfer. We feel that therefore the final thermos was so effective, because of low conductivity and reflection of the rising heat. Our thermos could have been better however, with different materials we could have limited heat loss even more, if we had more resources this would be the case as well. Using thicker foam to surround the cup would be crucial for minimizing heat transfer to outside the cup. All of the materials we used had a very low thermal conductivity to prevent transfer of heat. The type of tape used was different in the final product and we also put the blanket on top of the lid instead of below it but everything else was the same as prototype 3. The tape was better at holding what it needed to in place.