How to send a circle of friends who want others to send thermos cups?

If you want someone to send you a thermos, you just need to send a "I want a thermos" and then take a photo of the thermos.

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A thermos cup is usually a water container made of ceramic or stainless steel with a vacuum layer. There is a lid on the top of it, which is tightly sealed. Vacuum insulation layer can delay the heat dissipation of water and other liquids to achieve the purpose of insulation. The thermos cup is developed from the thermos bottle, and the heat preservation principle is the same as that of the thermos bottle, except that people make the bottle into a cup for convenience. There are three ways to spread heat: radiation, convection and conduction. The silver liner in the thermos cup can reflect the radiation of hot water, and the vacuum between the liner and the cup can block the heat transfer, while the bottle which is not easy to transfer heat can prevent the heat convection. vacuum bottle