Aluminium has high thermal diffusivity ;therefore heat will diffuse swiftly through the foil.What is the logic behind wrapping our food items in aluminium foil ?? A sheet of paper has much lower thermal diffusivity as compared to aluminium foil so any food item wrapped in a sheet of paper will remain warmer for more duration as compared to food item wrapped in aluminium foil..right?
Recently they are using aluminum foil coated with paper to avoid the contamination of food with aluminum by direct contact, which is proven to be causing Alzheimer disorder. Aluminum having very thin naturally form oxide protecting layer, which is piratically immune in reacting with air and any other mild acidic and basic environment caused by food such as cheese etc. under the vacuum packing conditions.
Secondly it is very easy to handle aluminum foil for wrapping without showing any fracture.
From my point of view the reason is related with the very low emissivity of the aluminium foil, which means that either the radiation gains either the radiation losses will be minimized. So, it means that you reduce the risk of burning the surface of the food while cooking it and the food wil be kept warmer for a longer time because radiation losses are minimized. The reason is the same why after rescue operations in the sea, people are covered with an aluminion foil sleeping bag.
Dear Mr. Nair
Aluminum foil considered as non toxic material that is why food is wrapped by it.
Best regards
@Mr. Khaleel.. then we can opt for some other non toxic material which has much lesser thermal conductivity...why aluminium?
@Mr. Manuel..your answer seems intriguing .i never thought about radiation heat transfer when this doubt cropped up in my mind!!...so according to you radiation heat transfer takes over conduction heat transfer..right??...i will get back to you once i analyse it..thank you!!
Dear Vipin,
If you consider, for instances, the heat losses of the human body, radiation losses normally represent as much as convection losses or even a little bit more. Only in case you have high velocities of air, convection will represent more than radiation
Aluminum act as the radiation shield to keep the food warmer for its highly reflective nature. Although the thermal diffusivity is higher in aluminum, both side of foil cases some hindrance in heat transfer. inner side attain very low radiation energy and high conductivity helps to pass this energy to outside layer of the foil. then, air adjacent to the outside foil allows very low conduction and natural convection. Another interesting thing is that there is an air gap between the food and foil in most of the portion as it is not laminated; eventually, the heat is transferred from food to foil mostly by radiation rather than conduction.
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