Why thermo-flask keeps warm water warm and cold water cold.
The thermoflask is built by considering heat transfer and how substance gain and loose heat, which is by only Conduction, Convention and Radiation.
Conduction: It is process by which heat energy is gain or loses by the passage of heat from one molecule or particle to another, without actual movement of the molecule itself.
Convection: It is a process by which heat is gain or loses by actual movement of the heated particle.
Radiation: It is a process by which heat is gain or loses through a vacuum (Empty space)
How thermoflask is built to avoid heat loss or gain.
- Thermoflask is built with vacuum in between two walls. The vacuum there is to prevent heat loss or gain by conduction and convention.
- It is built with two interior walls facing each other and coated with silver. The silver coated wall is to prevent heat gain or loss by Radiation.
- It is also built with insulating cork support at bottom. This prevent heat gain or loss by conduction
- Thermoflask is built with an insulating plastic or cork stopper; this is to stop heat gain or loss by conduction and convention.
Therefore with all these in place thermoflask will always keep warm water warm and cold water cold.