Question

a thermos bottle has the following features to control transfer of heat energy in and out: a) a tight cover, b) a shiny metallic outside coating, and c) an air layer between the inside and outside surfaces. what function does each of these features serve in controlling heat energy transfer? Which of the heat transfer processes is most reduced by each design feature of the thermos

Answer 1

a) The tight cover on the top prevents hot water vapor (steam) coming out of the bottle. So it prevents heat transfer via convection.

b) the shiny metallic outer coating acts as a perfect reflector and does reflect all the heat from the outer surface back into the atmosphere.It does not allow heat energy to be transmitted to the inner surface as maximum energy is reflected. also, the metal surface reflects the heat energy inside the thermos to the inner volume of the thermos and does not allow heat to come out. The metal surface prevents geat transfer via Thermal Radiation mode.

c) Air has a very poor thermal conductivity, the coefficient of thermal conductivity of air is very less such that it allows very less amount of heat to pass through it. So air prevents heat transfer via Thermal conduction.