As the pace of life accelerates, many people are unwilling to queue for a few hours to eat a hot pot, but they miss the taste of hot pot, so a kind of Internet celebrity "self-heating hot pot" came into being. This kind of self-heating hot pot does not require fire or electricity, and only a bottle of water can make you eat fragrant hot pot. However, many people do not know the risk source of self-heating hot pot, which causes it to become a "mini heat bomb", posing a threat to people's health. The principle of
self-heating hot pot
self-heating hot pot not only contains the food and sauces we need, but it also has a heating pack. Its main ingredient is quicklime, which is the material used to produce heat. The main chemical formula of quicklime is CaO, which can be obtained by calcining limestone containing calcium carbonate at 900 degrees Celsius in a kiln. Quicklime is water-absorbent. It is often used as a desiccant for food. It reacts with water to quicken mature lime (chemical name calcium hydroxide) and releases a lot of heat.
When we add water to the quicklime in the self-heating hot pot, and then close the lid. The heat released by their chemical reaction is enough to boil water and turn it into steam. Then the heat is transferred to the food through heat conduction and heat convection, and we can eat the hot pot in just a few minutes.
Dangerous source of self-heating hot pot
November 9th is National Fire Safety Day, CCTV invited firefighters to do an experiment. During the work of the self-heating hot pot, firefighters blocked the vent of the lid with tape. In less than 5 seconds, the outer packaging of the self-heating hot pot began to expand, and finally it burst open, and the lid flew out, and the hot water inside was sprayed all over the place. According to the introduction of firefighters, the temperature of hot water can exceed 100 degrees Celsius, and the temperature of steam can reach 200 degrees Celsius. If we are just by the self-heating hot pot, we will be exposed to these hot liquids and gases, which will inevitably cause extensive burns.
When we accidentally blocked the vent of the lid, the self-heating hot pot has formed a closed space at this time. At this time, the water inside will always boil into steam, which increases the pressure of the gas in the hot pot. The higher the pressure, the higher the boiling point of water, just like a pressure cooker, when the temperature of the water has exceeded 100 degrees Celsius. The temperature of the gas will also increase. According to the Gas-Lussac law, the higher the temperature, the greater the pressure, and the increase in pressure at this time becomes more terrifying. When the pressure difference between the inside and outside is greater than the bearing capacity of the self-heating hot pot box, it will burst and splash out the liquid and gas inside.
Immediately afterwards, firefighters did a more extreme experiment. He opened the bag of quicklime, poured the quicklime directly into the mineral water, and tightened the lid. We saw that under the pressure of the bottle, the diameter of the bottle became three times larger, and in the end it exploded directly.
Other precautions for self-heating hot pot
In addition to being careful not to block the air outlet of the lid, self-heating hot pot actually has a lot to pay attention to. At the bottom of the box, there is a sign indicating the upper limit of the water level. When we add water, remember not to exceed it. Moreover, we can only add cold water to it, not heating water. Because hot water may cause the reaction to become more violent, the water may boil violently, causing danger.
We also don't put the self-heating hot pot on the glass table, if it is really impossible, then we must add a heat insulation pad. We know that the heat source of the self-heating hot pot is at the bottom, and when its bottom is in contact with the glass, that part of the glass will become hot. Thermal expansion and contraction are well-known truths. That part of the heated glass will expand, but it is bound by other parts of the glass, which will cause a great thermal stress. If this force is too large, the final result of the glass can only be burst, which threatens human health.
Finally, it should be noted that not all occasions can carry self-heating hot pot. From the perspective of civil aviation, its heating pack is a flammable solid, and it cannot be carried on the plane or checked in.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-