Generally, the insulated lunch box is a food container made of double-layer plastic or stainless steel plus vacuum layer or heat insulation layer. The top is covered and tightly sealed. The vacuum layer or heat insulation layer can delay the heat dissipation of the food installed inside, so as to achieve the purpose of heat preservation. Thermal insulation lunch box is developed from thermos, and the thermal insulation principle is the same as thermos. There are three ways of heat transmission: radiation, convection and transmission. The silver liner in the heat preservation barrel can reflect heat radiation, and the vacuum layer or heat insulation layer of the cup body can block heat transfer.
Modern insulation lunch box applies high-tech vacuum technology to vacuum the interior of double-layer high-quality 304 stainless steel, which can effectively block the heat source and achieve the effect of thermal insulation. The design is more humanized. It is usually designed into three or four layers (as shown in Figure 1). Lunch boxes and soup boxes requiring higher temperature are placed under the insulation barrel, then the middle is covered with a heat insulation board, and then the vegetable box is placed on it. It can not only bring you the best heat insulation effect, but also make your food and drinks longer and fresher.
