Planning and Processing
Prototype materials and procedures
Prototype #1
Prototype #2
Prototype #3
The foam insulations and cotton balls were damp from the water molecules that went into the second layer cup. The tape lid was also damp on the inside as well as the outer layer of the styrofoam cup. A lot of heat went in between the two cups.
Final Product
Materials: 1 Styrofoam cup, 1 paper cup, 1 foam insulation, 1 layer of black paint, 6″ by 3″ aluminum foil (body), 3″ by 3″ aluminum foil (lid).
Total cost: $3.00
Results: Our water temperature dropped from 80°C to 56°C which is a drop of 24°C. The outside of the cup was a little warm and the foil lid was very hot when touched. When placing the hand above the lid (not touching), it was a little warm like the cup but not hot like when it was touched. The foam insulation was a little damp, but it did not absorb too much water.
First, we used the styrofoam cup as our main container to hold hot water because it has a thermal conductivity of 0.03. This means that it is a poor thermal conductor and it prohibits heat transfer through the cup. The styrofoam acts as an insulator so the heat doesn’t move from the higher temperature to the lower temperature materials (law of conservation of energy). The water is in the form of thermal energy (kinetic energy). We used the aluminum foil to wrap the cup so the heat can reflect off the foil and back inside. The foil lid would also prevent the heat from escaping and instead, maintain inside the cup. We also painted the paper cup for radiation heat that would go out into the air. The black paint would keep the heat from going out since it can even travel through the air space without any objects (radiation). Through convection the cold air from outside would try to replace the warm air inside so the usage of foam insulation would prevent the warm air from reaching the cold air. The paper cup (thermal conductivity: 0.05) provide a double layer of strong insulators so little heat conducts through the two cups. The lid covered the styrofoam cup so the heat does not directly get lost. From our previous prototypes, the lids were on the second cup which caused the heat to escape to the outer layer of insulation where it gets lost faster. Having the lid on the inner cup also prevents the outer layer from becoming damp, losing the full function to trap heat. With more money, another foil lid for the second cup and more foam insulation to fully cover the styrofoam cup would have trapped the heat in more.