Day 6: [THERMOS EFFICIENCY CHALLENGE!]

Today most of the period was dedicated to the design log section, but we did have other team members work on the thermos. For the "Thermos Efficiency Challenge," we checked how efficient our thermos was, and recorded the temperature to make our heat v.s. time graph. However the recording may need to be done again as the time and temperature when it first entered the thermos was not recorded because of human error. During the testing we made a few minor adjustments along the way as we noticed that the clay on top of the lid was becoming wet and soggy, so we put a small circular layer of foam underneath the clay. We also rechecked that our bottle held the physical requirements of 500 ml just in case, and at the very end of class we started doing the calculations for efficiency.     

Day 5: [TROUBLESHOOTING AND RE-TESTING]

After the thermos was rebuild our initial focus was on troubleshooting. Once the testing took place again for the second time, now with the requirements, it occurred to us that the thermos wasn't retaining all the heat as the bottle still felt warm. There was only a certain spot that was maintaining the heat which was the bottom of the bottle, that held rice. The reason for this is because in current thermoses they hold a rubber support at the bottom which prevents the flask from touching the outer layer. When the flask isn't touching the outer layer, heat isn't being transferred because of the insulation (rubber) between them. In this case, the thick layer of rice at the bottom of our thermos acted as a good heat insulator based on our experience.

Therefore we applied the same method by adding bubble wrap which is a thicker layer of insulation inside of the 2L bottle to surround the plastic bottle, and furthermore having tin foil and tape entwine outside of the 2L bottle to insure extra insulation. We decided to keep the plastic lid of the bottle as it is, because from our research we found out that plastic is a good head insulator and it's a easy material to cut though so we can insert our thermos in. The very last detail we added was a piece of clay for the lid to prevent the heat coming out of the hole that was made for the thermos. The clay would just be placed on top without being glued or taped on so that it can be removed when liquid is needed to be poured in the thermos. Clay is also a good heat insulator because the minerals that it's made out of are low in thermal conductivity. 

http://answers.yahoo.com/question/index?qid=20080303114828AAD6eis

http://answers.yahoo.com/question/index?qid=20100107222756AALF6q1

Day 4: [BACK TO THE DRAWING BOARD]

Even though the top of the thermos wasn't completed and the thermometer was not in place, we decided to start testing anyways to check the durability of the thermos. The thermos was generally able to retain the heat, but the plastic bottle which we had placed inside the 2L bottle was more than 500 mL, which did not meet the requirements because we needed to use 500 mL or less. Trouble-shooting began as more adjustments are being made and further research was being done. Some of the ideas we shared were, to use a Styrofoam cup or coffee cup for the inside of the 2L bottle as they were both small so would probably use less then 500 ml  Luckily enough a plastic bottle was given to us that met the requirements so we started rebuilding using it right away. Another thing we changed besides the bottle was the sock which was switched to a thicker cotton sock because it's a better insulator as it can trap air from being transferred.

(http://wiki.answers.com/Q/Why_cotton_is_a_good_insulator#page2)