Thursday, 9 May 2013
REAL LIFE APPLICATIONS
Several years from now all aspects of society will drastically change for the better, as technology advances so will other areas such as economic, political, and social. With all these factors changing there will be an environmental impact throughout all. This project allowed us to experience the role of an engineer and how they make devices and technology more efficient yet also environmental. Creating the thermos showed on a smaller scale what engineers consider when making something; they do research, test, troubleshoot, and re-test again. From making the thermos we learned about the first and second thermodynamics, this design and information could help apply to other inventions. The need for efficient devices is significant it creates a positive impact for the society, because it allows people to work more conveniently and life becomes more sustainable for them since technology is advancing.
HOW EFFICIENT ARE THE THERMOSES MADE TODAY?
Most thermoses during this age come with an efficiency of at least 90%,and usually can't exceed 100% efficiency because it doesn't go along the law of second thermodynamics. Which states that nothing can be 100% efficient because due to conversions between substances heat is lost. The flask of a thermos is made of a thin low thermal conductance material, the space is a vacuum filled so conduction doesn't occur, and the shiny interior outside and inside of the thermos is used to prevent radiation.
http://uk.answers.yahoo.com/question/index?qid=20111005104556AAfamnZ
http://uk.answers.yahoo.com/question/index?qid=20111005104556AAfamnZ
HOW HAS THE MODERN DAY THERMOS CHANGED FROM PREVIOUS MODELS?
spacers which provide additional support between the two layers of a thermos were added to eliminate the impact of the inner flask being too heavy for the outer flask to hold its contents. Another improvement to the thermos includes vapor cooled neck to reduce evaporation from the flask.
WHICH MATERIALS WILL PROVIDE THE BEST INSULATION FOR THE THERMOS?
*Styrofoam : Since the air pockets are too small they are unable to make a convection current between substances.
All the isolated gas bubbles slow down the transfer of heat.
REFERENCE: wiki.answers.com, http://www.ehow.com/how-does_4898717_why-styrofoam-good-insulator.html
REFERENCE: wiki.answers.com, http://www.ehow.com/how-does_4898717_why-styrofoam-good-insulator.html
*A Cotton Sock: Cotton is a good thermal insulator as it traps air and has only little pockets of holes that air can go through, and that makes heat transmit slowly.
REFERENCE::wiki.answers.com ›
*Steel wool: Steel wool is a fair thermal insulator (thanks to the trapped air)
REFERENCE:amlloyd.appspot.com
*Duct tape: It's not as conductive as metals, but a lot more insulated than foam or fiberglass insulation. Probably about the same as wood.
REFERENCE:answers.yahoo.com ›
*Bubble Wrap: Each bubble contains air inside , which is a very good insulator. Very little heat exchange occurs, so whatever is wrapped in the bubble wrap is kept at a more or less constant temperature.
REFERENCE:uk.answers.yahoo.com*Plastic: Because it's also made up of small air pockets tightly packed together so that heat is lost very slowly.
http://wiki.answers.com/Q/Why_is_plastic_a_good_insulator_of_heat
*Rubber: Rubber is a very dense material which makes it a good heat insulator because the denser the material is, the tigher the atoms are. When atoms are tightly packed together they're a stronger bond, so heat can't escape.
http://answers.yahoo.com/question/index?qid=1006052112417
OVERALL ANALYSIS
- Test 1 : Efficiency = 85%
- Test 2: Efficiency = 76%
We lost majority of our heat from around the bottle, this may be because of the insulators we choose. Less heat was being transmitted from the bottom, and that was because we had the support of the rice preventing the bottom part of the bottle from touching the outer layer. We could've improved our materials by looked at the heat capacity of each material so we could get an idea of how much they generally insulates. I would've changed some of the materials for future versions and do more testing/improvements so we could compare results with a thermos that has a better efficiency than ours.
Laws of thermodynamics are the principles that govern heat transfer and thermal energy. The first law of thermodynamics state that, "Energy can be transformed into another form, but can't be created or destroyed." If you were to experiment with volatile heat sources you could have seen that liquid forms into gas when the temperature rises. When you lift the lid off of the thermos, gas will come out because of the hot temperature making the liquid evaporate. If we look at the heat capacity of plastic which is, c = 39.6K Jkg-1 K-1 we can find out how much heat is measured to heat up a gram of plastic, or any other material thus finding out if the heat source if volatile. The equation for relating heat energy to a specific heat capacity in terms of mass is; Q = m c ΔT.
- Q : Heat energy input or output of the substance
- m : Mass of substance
- c : Specific heat capacity
- ΔT: Temperature differential
The second law of thermodynamics states that," In all energy exchange if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state." or in other words no process can be 100% efficient because some energy will always remain in the form on thermal energy. An example of this would be when a car runs out of gas in the middle of the desert and will not run again until you walk 10-15 miles to a gas station and refuel the car. When energy exchange occurs some energy is transfer into thermal energy; Our project is evidence that this is true, as heat can be felt (meaning it's not 100% efficient).
http://answers.yahoo.com/question/index?qid=20071215081939AALhW4z
http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookener1.html
http://wiki.answers.com/Q/What_is_plastic's_specific_heat_capacity
Wednesday, 8 May 2013
ANALYSIS [RESULTS OF TEST 2]
Time loss testing#2 of thermos (May 8, 2013)
Period of 60 minutes
Total efficiency of test#2 is 76%
Test#2 : 54/71 x100 = 76%
Period of 60 minutes
Time
|
Temperature (fahrenheit)
|
10:25 am
|
71 degrees
|
10:27 am
|
70 degrees
|
10:29 am
|
69 degrees
|
10:31 am
|
67 degrees
|
10:33 am
|
66 degrees
|
10:35 am
|
65 degrees
|
10:37 am
|
64 degrees
|
10:39 am
|
63 degrees
|
10:41 am
|
62 degrees
|
10:43 am
|
62 degrees
|
10:45 am
|
62 degrees
|
10:47 am
|
61 degrees
|
10:49 am
|
60 degrees
|
10:51 am
|
60 degrees
|
10:53 am
|
59 degrees
|
10:55 am
|
59 degrees
|
10:57 am
|
59 degrees
|
10:59 am
|
58 degrees
|
11:01 am
|
58 degrees
|
11:03 am
|
58 degrees
|
11:05 am
|
57 degrees
|
11:07 am
|
57 degrees
|
11:07 am
|
57 degrees
|
11:09 am
|
56 degrees
|
11:11 am
|
56 degrees
|
11:13 am
|
56 degrees
|
11:15 am
|
56 degrees
|
11:17 am
|
55 degrees
|
11:19 am
|
55 degrees
|
11:21 am
|
55 degrees
|
11:23 am
|
54 degrees
|
11:25 am
|
54 degrees
|
Total efficiency of test#2 is 76%
Test#2 : 54/71 x100 = 76%
ANALYSIS [RESULTS OF TEST 1]
Time loss testing#1 of thermos (May 7, 2013)
Period of 26 minutes
Period of 26 minutes
Time
|
Temperature (Fahrenheit)
|
9:17 am
|
70 degrees
|
9:19 am
|
69 degrees
|
9:21 am
|
68 degrees
|
9:23 am
|
67 degrees
|
9:25 am
|
66 degrees
|
9:27 am
|
65 degrees
|
9:29 am
|
64 degrees
|
9:33 am
|
64 degrees
|
9:36 am
|
63 degrees
|
9:40 am
|
62 degrees
|
9:43 am
|
62 degrees
|
9:46 am
|
61 degrees
|
9:47 am
|
60 degrees
|
The total efficiency for the first test is 85%
Testing#1: 60/71 x100 = 85%
Day 7: [FINAL TESTING]
Another testing was done so that we could compare the results to our first test and see how similar or different the results were and why. Testing#2 efficiency was lower at 76% compared to testing#1 which had the efficiency of 85%, one reason that this probably happened is because testing#1 had a shorter period of time recorded in comparison of testing#2. Our thermos was completed and all final adjustments were made the day before, thus today was just a work period on completing our research. Heat v.s. time graph was made, and the analysis was getting done.
Tuesday, 7 May 2013
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.
WHAT IS THE PURPOSE OF A THERMOS?
The purpose of a thermos is to retain the temperature in a container by allowing heat to flow out or in so that its contents are kept cold or hot depending on the liquid in the container. Heat can only flow from hot surfaces to cold ones by three ways.
- CONDUCTION: Is when heat is transferred from one molecule to another though a substance, in other words it's the flow of heat through solids. An example of this would be when one end of a nail is under a flame over a period of time till the other side of the nail will be hot as well. This is because of conduction.
The time it takes for the other side of the nail to become hot depends if it's the material is a heat conductor or insulator. If it's a conductor then heat can easily be transfer, but if it's a insulator heat is difficult to be transmitted.
- CONVECTION: Is the transfer of heat by a movement of liquid and gas due to different density levels which is caused by the difference in temperature. An example of this would be when a kettle is being heated up by a stove. The bottom of the kettle is heated first then the heat rises to the top and the cooler water flows down to be heated. This continues to circulate making the heat in the kettle transfer throughout the liquid.
- THERMAL RADIATION: Is electromagnetic radiation created by thermal motion. Radiation is something that emits energy through waves, electromagnetic radiation is just a type of wave that sustains electric and magnetic components. Hence thermal motion produces energy in the form of waves that maintain electric and magnetic substances.
HOW ARE CURRENT THERMOSES CONSTRUCTED?
A typical thermos would have a flask (inner chamber inside of an outer chamber.) The inner layers (glass and vacuum) would be coated with mercury to allow heat rays to enter the flask and be reflected between the two layers; this prevents the transfer of heat.
Sometimes modern thermoses are made of stainless steel-Inside and out, so it does not shatter. It's naturally reflective so a reflective coating sometimes doesn't need to be added. Although other thermoses have a shiny interior coat insulator such as metal, to expel thermal radiation because it causes heat loss.
Thermoses often use rubber or cork material to make bottle stoppers, this prevents the glass container from touching the the outer container surrounding the flask so that conduction doesn't occur.
Sometimes modern thermoses are made of stainless steel-Inside and out, so it does not shatter. It's naturally reflective so a reflective coating sometimes doesn't need to be added. Although other thermoses have a shiny interior coat insulator such as metal, to expel thermal radiation because it causes heat loss.
Thermoses often use rubber or cork material to make bottle stoppers, this prevents the glass container from touching the the outer container surrounding the flask so that conduction doesn't occur.
WHAT MATERIALS ARE CURRENTLY USED TO MAKE A THERMOS AND WHY?
Often current thermos are made out of two layers (Glass & Vacuum) to decrease the amount of heat escaping, a rubber support so that conduction doesn't occur, and a shiny interior coat around the outside layer of the bottle. The shiny coat is used to lessen the amount of thermal radiation. Some other materials that could be used to make a thermos could be,
http://answers.yahoo.com/question/index?qid=20100107222756AALF6q1
- 2L Bottle
- Plastic bottle
- Tin foil
- Foam layer
- Duct tape
- Steel wool
- Sock
- Rice
- Clay
- Bubble
- Wrap
- These two layers are nestled together at the neck and all the air in between them is evacuated.
- A reflective coating is added to the surfaces of both layers so that radiative heat loss can be minimized.
Tin foil: The tin foil will be going inside the 2L bottle and around the plastic bottle so that the heat keeps circulating and the heat content isn’t being lost but reflected.
Foam layer & Steel wool: The foam layer and steel wool will act as the main insulator. The foam layer can’t conduct air because of its plastic pockets, thus heat/cold temperatures can’t be release easily. Steel wool is used in many industrial places for high heat insulation; this proves that steel wool can retain heat as it’s been tested and used numerous times.
Duct tape: To keep everything together as well as add extra insulation
Rice: To secure materials together, and get rid of extra crevices that is not needed.
- This material could be used for the bottom of the thermos to prevent conduction
Cotton sock: to maintain the steel wool or any other materials and to add extra insulation. Cotton traps air which build up in heat.
Bubble Wrap: Contains patches of trapped air which is a good insulator, as temperatures can’t be transferred.
http://wiki.answers.com/Q/How_is_bubble_wrap_a_good_insulator
http://wiki.answers.com/Q/How_is_bubble_wrap_a_good_insulator
Clay: The minerals in clay have low thermal conductivity so it’s a good heat insulator. Which is why we choose this for the top cover of our thermos.
- Since most of the heat loss in a thermos occurs through the neck and opening of the flask, the openings are usually stoppered with cork, polyethylene plastic or rubber that is attached to the lid to prevent any additional heat loss.
http://answers.yahoo.com/question/index?qid=20100107222756AALF6q1
Monday, 6 May 2013
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.
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