1. Double-Walled Construction: A vacuum flask consists of two layers of glass or stainless steel with a small gap between them. This gap is referred to as the vacuum layer.
2. Vacuum Layer: The space between the two layers is evacuated to create a vacuum. This eliminates the transfer of heat through conduction and convection, as there is no air or other gas particles present to carry heat.
3. Reflective Coating: The inner surface of the outer layer and the outer surface of the inner layer are often coated with a reflective material, such as silver or aluminum. This coating helps to minimize heat loss by reflecting heat back into the flask.
4. Insulation: The vacuum layer, combined with the reflective coating, creates a highly efficient insulating barrier. Heat transfer is significantly reduced, allowing the contents of the flask to stay hot for an extended duration.
5. Tight Sealing: The flask is equipped with a tight-fitting stopper or lid that prevents heat from escaping through the opening. The stopper may have a rubber or plastic gasket to ensure a snug fit and further reduce heat loss.
6. Limited Heat Conduction: The materials used in the construction of the flask, such as glass or stainless steel, have low thermal conductivity. This means they do not conduct heat easily, further contributing to the flask's ability to retain heat.
By combining these design features, a vacuum flask effectively minimizes heat transfer and keeps tea hot for several hours, making it an ideal container for storing and transporting hot beverages.
