It is not normal that the thermos bottle expands seriously when charging. Because the charging hot water bottle contains a certain amount of liquid, and a kind of heating powder is added, the flow of water is accelerated by electrifying, and the black powder is stimulated to produce a chemical reaction to release heat, which is the working principle of the charging hot water bottle.

The water in the thermos bottle is not ordinary domestic water, but water mixed with impurities, which becomes the conductor of electricity. But if there are too many impurities in the water in the bag, the concentration will be high. When the water is electrified, these excess impurities are electrolyzed to produce a large amount of gas, which makes the thermos bottle expand. After the water in the bag is poured out, the same amount of purified water is added to dilute the water inside, so that the concentration of the internal solution reaches a predetermined value, and a large amount of gas will not be generated after electrification.

Extended data:

Precautions:

1. Suitable for infants, the elderly, coma, poor peripheral circulation, unconsciousness under anesthesia, sensory disturbance and other patients. The water temperature of the thermos bottle should be adjusted below 50℃ and wrapped with a big towel to avoid direct contact with the patient's skin and causing burns.

2, hot water bottle in the process of use, should always observe the color of local skin. If you find that your skin is red, you should stop using it immediately and apply vaseline locally, which can protect your skin.

3. If the hot water bottle needs to be used continuously, the hot water should be replaced in time.

4, strictly implement the system of succession.

Baidu encyclopedia-hot water bottle