WEEK 4: MATERIAL SELECTION

Materials For Design Assignment - Thermos Flask

Serves as a recap on the COWS Matrix learnt in Materials For Design
Identify qualities, objectives and obstructions of making a product which will help with other projects to come and our current one.

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HOW DID WE DO IT?

We asked ourselves a few questions such as "What is the purpose of a thermos flask?" and afterwards "How does it do so?" These questions has allowed us to get a deeper understanding of the product and to help identify the most suitable material.

Purpose of thermos flask: A thermos helps to reduce the amount of heat loss due to radiation and eliminates heat losses through convection and conduction through a vacuum. When the thermos is holding a hot substance, it helps to prevent heat loss and then helps prevent heat gain when the thermos is holding a cold substance. So a thermos can keep hot things hot and cold things cold.

How does a thermos flask do so?: The thermos flask consists of a double-walled glass vessel resting on a cork inside a metal or plastic case. The outer surface of its inner wall and the inner surface of its outer wall are silvered. This prevents heat transfer due to radiation. The space between the two walls is almost vacuum and the walls are sealed at the top. The double-walled glass vessel and vacuum prevents heat loss by conduction. The insulating stopper or cork at the top minimises heat loss by convection.

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MATERIAL FOR THE THERMOS FLASK

Since we were tasked with two separate items to work on which is:

The stopper of the thermos flask
The inner walls of the thermos flask

Both of which will come in contact with liquids so toxicity is something that we had to consider apart from other criteria, our idea was that it made sense for the stopper to be made from a plastic-like material such as polypropylene or silicone and the inner walls would be made of metals such as 314 stainless steel.

We have decided to add 5 criteria for our COW’s Matrix which consists of: Corrosion resistance to water (Rusting), Thermal conductivity, Toxicity to humans, specific heat capacity and melting point.

We have also decided to give each of them an equal weightage of 20% each as we felt that all of the properties listed in the Cows matrix are equally important.

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CONCLUSION: STOPPER OF THERMOS FLASK

According to the COWs Matrix, it can be seen that silicone has the best properties according the the criteria that we have listed so therefore we deduced that it is the most efficient for this purpose.

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CONCLUSION: INNER WALLS OF THERMOS FLASK

According to the COWs Matrix it can be seen that 304 Stainless Steel has the best properties according to the criteria that we have listed so therefore we deduced that it is the most efficient for this purpose.

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REFERENCES

Matweb.com. 2021. MatWeb - The Online Materials Information Resource. [online] Available at: <http://www.matweb.com/search/DataSheet.aspx?MatGUID=d16a64a389df424f8e53ed481e77477b&ckck=1> [Accessed 14 May 2021].

Matweb.com. 2021. AISI Type 304L Stainless Steel. [online] Available at: <http://www.matweb.com/search/DataSheet.aspx?MatGUID=e2147b8f727343b0b0d51efe02a6127e> [Accessed 13 May 2021].

Matweb.com. 2021. Alclad Aluminum 3003-H112. [online] Available at: <http://www.matweb.com/search/DataSheet.aspx?MatGUID=a594182a80f24ed6bd45c93847eabbc4> [Accessed 13 May 2021].

Chris, W., 2019. Vacuum Flasks [online]. ExplainThatStuff. Available from: https://www.explainthatstuff.com/vacuumflasks.html [Accessed 14th May 2021]

Plastics International. 2021. Chemical Resistance Chart | Plastics International. [online] Available at: <https://www.plasticsintl.com/chemical-resistance-chart> [Accessed 13 May 2021].

Phelpsgaskets.com. 2021. Chemical Resistance Chart - Elastomers | Phelps Industrial Products. [online] Available at: <https://www.phelpsgaskets.com/useful-resources/chemical-resistance-chart-elastomers> [Accessed 13 May 2021].

News. 2021. BPA, chemical used to make plastics, found to leach from polycarbonate drinking bottles Into humans. [online] Available at: <https://www.hsph.harvard.edu/news/press-releases/bpa-chemical-plastics-leach-polycarbonate-drinking-bottles-humans/#:~:text=2020%20Multimedia-,BPA%2C%20chemical%20used%20to%20make%20plastics%2C%20found%20to%20leach%20from,polycarbonate%20drinking%20bottles%20Into%20humans&text=Exposure%20to%20BPA%2C%20used%20in,disease%20and%20diabetes%20in%20humans.> [Accessed 14 May 2021].

Matmatch.com. 2021. Polypropylene Homopolymer (PPH) - Polypropylene (PP) - Matmatch. [online] Available at: <https://matmatch.com/materials/mbas001-polypropylene-homopolymer-pph-> [Accessed 14 May 2021].

Healthline. 2021. Is Polypropylene Safe and BPA Free?. [online] Available at: <https://www.healthline.com/health/is-polypropylene-safe#is-it-safe> [Accessed 14 May 2021].

Healthline. 2021. Silicone Safety: Risks, Exposure Sources, Is Silicone Toxic & More. [online] Available at: <https://www.healthline.com/health/body-modification/is-silicone-toxic#:~:text=It's%20used%20for%20medical%2C%20electrical,use%20and%20likely%20not%20toxic.&text=Liquid%20silicone%20may%20block%20blood,to%20an%20extremely%20dangerous%20situation.> [Accessed 14 May 2021].

Coleparmer.com. 2021. Chemical Compatibility Database from Cole-Parmer. [online] Available at: <https://www.coleparmer.com/chemical-resistance> [Accessed 14 May 2021].

Santonen, T. et al., 2010. Review On Toxicity of Stainless Steel. Finnish Institute of Occupational Health [online]. Available from: https://core.ac.uk/download/pdf/84322713.pdf [Accessed 14 May 2021].

Davis, J.R., 2001. Aluminum and Aluminum Alloys. ASM International [online]. Available from: https://materialsdata.nist.gov/bitstream/handle/11115/173/Aluminum%20and%20Aluminum%20Alloys%20Davis.pdf [Accessed 14 May 2021].

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