In my opinion, there is no furnace tripod in dantian, and this process is not that water (body fluids) is gasified in the furnace tripod. It is a complex electrochemical reaction of body fluids in the abdomen, mainly the polarization reaction of ions in body fluids, which produces atoms, molecules, electrons, substances, heat and energy. Material energy for short. When the energy of these substances accumulates to a certain extent, they can move, and at this time they can be guided by thoughts. Why did the ancients say that one furnace made a tripod? Because the ancients didn't have so much scientific knowledge and didn't understand any reaction, they thought that the heat here must have been caused by a fire. Qi is gasified from body fluid, which is very close to modernization. In fact, strictly speaking, it should be gasified from body fluids. This gasification is essentially a complex electrochemical reaction. There may even be biological reactions and more complex reactions.
It should be pointed out that this reaction can occur not only in Xiadantian, but also in other places, but with different speed and quantity. Here, only the energy in body fluids (especially ions) is easier to concentrate, diffuse and transport. So the general practitioners will choose to vaporize in this place. Then guide the whole body to run. But as I said before, middle-aged and elderly people (people with negative constitution) should not blindly practice Qi here, because this is the cathode, and the main gasification is cation (I don't think it is scientifically confirmed, for reference only). The yin and yang of constitution are determined by the ratio of yin and yang ions in body fluids (also for reference), so it is necessary to maintain the balance of yin and yang ions in body fluids to maintain the health of the body. Therefore, attention should be paid to the proper gasification of anions at the anode (Yang point) to maintain the balance of anion and cation. For reference.