The heating principle of hand warmers

Hand warmer, can be broadly divided into three kinds, the heating principle is also about three kinds: 1, by heating water to heat, which is commonly known as hot water bags, and the traditional hot water bags are different, electric hot water bags save the trouble of adding water, just plug in the power supply and so on for 10 minutes to heat up, in fact, the water inside boil, so the general temperature will be very high.
2, through the chemical reaction to heat, the market is this type of hand warmer, through the contact of chemical substances inside, the heat generated, the temperature is about 40 ℃. 3, the use of lithium battery function, the internal heating pad heat, the use of USB interface charging and discharging, similar to hand warmer mouse pad, due to the lithium battery can charge and discharge function, generally can also be used as a mobile power.
Small size, easy to carry around, the temperature can reach about 50 ℃.