Vapor Pressure In Closed Cylinder

In summary, the conversation discusses whether a vacuum or simply low pressure is present in a scenario where a pump supplies water to a pipe and the water discharges several kilometers away. It is determined that there is no such thing as a negative pressure and the pressure in the pipe is dependent on temperature and can be checked using water vapor pressure tables.
  • #1
AshleySNL87
2
0
Hi There, I am trying to understand if I have a vacuum in the below scenario or simply just really low pressure.

A pump supplies a pipe with a constant supply of water at one end (Point A) the water discharges several kilometers away at some lower elevation (Point B). At "Point A" a valve closes and seals. I assume that the water level in the pipe begins to drop, however, at some point it stops. At this instance have I created a Vacuum at point A? Or is the pressure at Point A simply below atmospheric pressure but above 0 pressure (by some small amount) due to the pressure created by water vapor?

The Engineering side of me sees the pipe as a cylinder and the fluid level acting as a piston, and as the piston lowers it creates a vacuum in the pipe, but I feel as if this is a poor way to look at the situation.
 
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  • #2
Closed space above anything is (if allowed to reach the equilibrium) saturated with the vapors of whatever is present. Technically even in the steel container evacuated of air there exist an iron vapor (although the pressure is so low we will assume it is just a vacuum).
 
  • #3
So to be more clear about it. I would have a very low pressure at or near 0 bar. But I would not have a negative pressure (I.e below 0 bar) Correct ?
 
  • #4
There is no such thing as a negative pressure (unless you mean a relative pressure, which doesn't make sense here).

The pressure you will see depends on the temperature and doesn't have to be low (guess what it will be at the boiling point), you can easily check the value in the water vapor pressure tables.
 

Related to Vapor Pressure In Closed Cylinder

What is vapor pressure in a closed cylinder?

Vapor pressure in a closed cylinder refers to the pressure exerted by the vapor molecules of a liquid inside a sealed container. This pressure is caused by the equilibrium between the liquid and its vapor, and it increases as the temperature of the liquid increases.

How does temperature affect vapor pressure in a closed cylinder?

As the temperature of the liquid inside a closed cylinder increases, the vapor pressure also increases. This is because higher temperature means more energy for the liquid molecules to escape into the vapor phase, increasing the number of vapor molecules and therefore the pressure they exert.

What factors can affect vapor pressure in a closed cylinder?

Apart from temperature, the type of liquid, the volume of the container, and the presence of other substances (such as solutes or gases) can also affect the vapor pressure in a closed cylinder.

Why is vapor pressure important to understand in a closed cylinder?

Vapor pressure is important to understand because it determines the amount of vapor present in a closed cylinder, which can have implications on the safety and stability of the container. It also plays a role in processes such as distillation and evaporation.

How is vapor pressure measured in a closed cylinder?

Vapor pressure in a closed cylinder can be measured using a device called a pressure gauge, which measures the pressure inside the container. It can also be calculated using the ideal gas law and experimental data on the temperature and volume of the container.

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