The issue of increased boiling point of water due to hydrostatic pressure
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This post was last edited by zhenshui*an on 2015-7-11 at 12:36. We know that the boiling point of water is 100 degrees at standard pressure, and it increases when the pressure is higher. Imagine a vertical 20m tube filled with water. After being filled with water, the hydrostatic pressure of the water at the bottom is 2 kg/cm2 (gauge pressure), and the bottom is heated to 120 degrees. At the bottom, due to the hydrostatic pressure of water, the boiling point is around 132.9 degrees; the water at the bottom does not reach this boiling point under such pressure and therefore does not boil. The question is: Will the water at the top boil? View 1: It will not boil. The static pressure of water causes the boiling point of the water at the bottom to rise; if the water at the bottom does not boil, then the water at the top will not boil either. Viewpoint 2: It will boil. When heated, the temperature difference between the top and bottom causes the water to have different densities, leading to natural circulation; the temperature of the water at the top also rises gradually. However, since it is under atmospheric pressure, the water boils. What do you all, sea friends, think?
The question you asked is a bit strange, but it’s interesting; I lean towards the second option. But the pipe must be large enough not to interfere with natural circulation.
This is a quite debatable issue; however, I think these two viewpoints are also somewhat related to each other. Bubbles begin to form (that is, boiling) at the corresponding saturated vapor pressure at the bottom: lol
I tend to agree with the second explanation – a difference in density does occur, and this is probably similar to what happens when water is boiled. Theoretically, the water at the bottom boils first, after which bubbles form and help to bring the water above to a boil as well. In other words, the water will become mixed and agitated. But this is on the premise that heat is supplied together; with sufficient heat, boiling will occur throughout. If the temperature is not enough, boiling requires a boiling core, and without bubbles rising, the flow of water between the upper and lower layers will not be very intense. This can also be observed from the temperature differences in seawater. Referencing the eruptions of undersea volcanoes, the water on the sea surface should not boil.
It should also be related to the amount of heat applied and heat dissipation. If the heating is sufficient and the tube is insulated, it should be the second case.
You can’t heat it to over 120°C, bro. During the heating process, there is convection of heat between the water and its surroundings, and eventually the water boils at the current atmospheric pressure, haha.
I agree with the second opinion; it should reach 120 degrees
Bubbles forming at the bottom cannot be called boiling; boiling occurs only when the water temperature at the top reaches 100 degrees.
Has anyone done this experiment?
The top will boil at 100 degrees, while the bottom won’t reach 120 degrees, as all the heat flows upward