Thermal Energy Transfer Portfolio 2
Portfolio Activity: Create
A team of students is trying to determine the best materials to use for thermal pads. They have two projects: a cold pack that absorbs thermal energy and a heat pad that emits thermal energy. Both projects have the same goal: to maximize the flow of thermal energy.
At first the students thought they could get the initial thermal energy into the heat pad and out of the cold pack by creating a chemical reaction inside the pad. They knew that there are existing products that generate heat from an exothermic reaction — one that gives off thermal energy — as well as other products that cool things by creating an endothermic reaction — a chemical reaction that absorbs thermal energy. Ultimately, though, they decided that generating energy in that way was too risky because they didn’t have the chemistry knowledge required to do it safely. Instead they would put thermal energy into the heat pad using a microwave oven, and reduce the thermal energy in the cold pack using a freezer.
When discussing what to house the devices in, they considered paper bags, zippered food-storage bags, and tube socks, among other items. For the contents of the container, they discussed washcloths, towels, wet washcloths and/or towels, oatmeal, and rice.
In the end, the students created two thermal pads by putting moistened towels into zippered food-storage bags. The thermal pads intended to be ice packs were frozen in a freezer for an hour, while the thermal pads intended to be heat packs were microwaved on high for 30 seconds.
To start, the students inserted a thermometer into the thermal pad and recorded its temperature. This is the initial temperature in the table below. Then they prepared their pads by cooling or heating them. As soon as that process was finished, they recorded the internal temperature of the pad again and put that in the
.0s
0s, zero seconds, column. They continued to check the temperature every 60 seconds over a total span of 300 seconds (5 minutes). They recorded each temperature reading. With this information, the students could judge how well thermal energy was transferred to or from each pad.
Table
Time of Temperature Reading
in seconds
Thermal Pad
Initial
0
60
120
180
240
300
Cold Pack
21° C
1° C
2° C
2° C
3° C
4° C
4° C
Heat Pad
21° C
80° C
74° C
68° C
62° C
54° C
52° C
Based on the temperature readings from the table, it is clear that both thermal pads were able to transfer thermal energy, but in different ways.
The cold pack had an initial temperature of 21°C and quickly dropped to 1°C after being placed in the freezer. Over the course of 5 minutes, the temperature gradually increased to 4°C. This indicates that the cold pack was able to absorb thermal energy from the environment and retain some of it, although not as efficiently as the heat pack.
The heat pack had an initial temperature of 21°C and then heated up to 80°C after being microwaved for 30 seconds. Over the course of 5 minutes, the temperature gradually decreased to 52°C. This indicates that the heat pack was able to emit thermal energy and gradually cool down, although it retained more thermal energy compared to the cold pack.
It is important to note that the thermal pads were made using moistened towels placed inside zippered food-storage bags. This choice of materials may have influenced the thermal energy transfer. Additionally, the duration of cooling and heating may also have affected the temperature readings.
Overall, the students' design of using moistened towels in zippered food-storage bags was successful in creating thermal pads that transfer thermal energy. However, further experiments and modifications can be done to improve the efficiency and effectiveness of the thermal pads.
Thermal Energy Transfer Portfolio 2
Portfolio Activity
Create Your Device, Part 1
For this activity, you want to create and test a thermal pad: either a heating pad that will emit thermal energy or a cold pack that will absorb thermal energy. While some examples were provided earlier, it is important to make the device your own.
To begin, you will use the following rubric to write out your design plan. Be sure to include how the materials will work well to absorb or emit thermal energy. How will your thermal pad be different from the basic plan? Can you think of creative ways to improve the basic design?
Design Plan:
Thermal Pad - Heating Pad
Materials:
1. Insulating fabric - to trap and retain thermal energy
2. Heating element - such as a resistance wire or heating coil
3. Temperature control mechanism - to regulate the temperature and prevent overheating
4. Power source - to provide the necessary energy for heating
How it works:
1. The insulating fabric will act as a barrier to minimize the loss of thermal energy, allowing it to be retained within the thermal pad.
2. The heating element will generate heat when electric current passes through it. This heat will then be transferred to the insulating fabric, which will further distribute it across the pad.
3. The temperature control mechanism will ensure that the heating pad doesn't exceed a safe and comfortable temperature. This can be achieved through a thermostat or a timer switch.
4. The power source will provide the necessary electrical energy to run the heating element.
Improvements to the basic design:
1. Multi-layer insulation: By using multiple layers of insulating fabric, we can enhance the pad's ability to retain thermal energy effectively.
2. Adjustable temperature control: Adding a control mechanism with different heat settings can provide users with the option to customize the temperature according to their comfort level.
3. Incorporating heat distribution: By integrating heat distribution channels or materials into the design, we can ensure that the thermal energy is evenly spread throughout the pad.
4. Soft and comfortable casing: Using a soft and comfortable outer casing material will enhance the user experience, making the pad more pleasant to use.
5. Safety features: Adding features like automatic shut-off in case of overheating or short-circuit protection can ensure the safety of the user and prevent any potential hazards.
By incorporating these improvements, the heating pad will provide a more efficient and comfortable experience for users.
When the pad is warm to touch, handle it using a potholder or oven mitt.
Procedure
Create your thermal pad by placing the substance or substances you chose into the container you chose.
As you work, think about how your thermal pad could be useful.
Use a thermometer to find the internal temperature of your device. Record that temperature in a table like the one below. Be sure to use the standard SI units degrees Celsius and seconds.
If your thermometer is only calibrated in degrees Fahrenheit, you convert your reading to Celsius using this formula:
(º F – 32) ⋅ 1.8 = º C
Proceed as planned to put initial thermal energy into the heat pad and/or reduce the amount of thermal energy in the cold pack.
When the process is complete, record the internal temperature of the thermal pad.
Continue recording the water temperature at regular intervals of a length you determine to be appropriate. Record all the readings in your table.
When you have finished and cleaned up your materials, write a short paragraph that answers these questions:
Did the temperature of the thermal pad change as quickly or as much as you expected it to?
Do you consider your thermal pad to be a success? Why or why not?
In what situations might the thermal pad be useful?
In what situations might the thermal pad be useful?
Time of Temperature Reading
in seconds
Thermal Pad
Initial
use this information to improve your design plan
Table: Temperature Readings
Time (s) | Thermal Pad Temperature (°C)
---------|----------------------------
Initial |
60 |
120 |
180 |
240 |
300 |
Based on the procedure, the temperature readings will be recorded at regular intervals to observe how the thermal pad performs over time.
Improving the design plan:
1. In order to improve the accuracy of temperature readings, a more precise thermometer could be used, such as a digital thermometer with decimal readings.
2. Implementing insulation layers within the thermal pad can enhance the heat retention or cooling effect, depending on the objective of the pad.
3. Incorporating a device or mechanism to allow the user to adjust the temperature within a desired range can provide more customization.
4. If applicable, considering alternative power sources or energy-efficient components can optimize the energy consumption of the thermal pad.
5. Testing the thermal pad in various scenarios and environments to assess its performance and reliability.
Paragraph answering the questions:
The temperature of the thermal pad may change differently than expected, as it depends on various factors like the materials used, insulation effectiveness, and energy transfer efficiency. The success of the thermal pad would depend on whether it fulfills its intended purpose. If the thermal pad effectively transfers or absorbs thermal energy, and the temperature changes as desired within a reasonable duration, it can be considered a success. The thermal pad can be useful in situations where localized heating or cooling is required, such as relieving muscle pains, providing warmth during cold weather, easing menstrual cramps, or alleviating sports-related injuries. Additionally, it can be useful in medical settings for treatments that require controlled temperature applications.