What determines the pressure inside this experimental setup?

  • #1
Dario56
289
44
I have two gas tanks of nitrogen and oxygen. Mixture of gases is created and used in the system of interest.

Let's say I want to create an atmospheric conditions in my system, mass ratio of oxygen to nitrogen is 0.3 and total pressure of 1 bar (oxygen partial pressure 0.21 bar). Therefore, mass flow ratio of the gases needs to be 0.3 to create a gas mixture of atmospheric composition. Gas tanks are equipped with volumetric flowmeters. This isn't a problem as mass and volumetric flowrates can be easily related by the ideal gas law. I'm planning using air at atmospheric pressure and temperatures 500-800 ##^\circ$## which I think justifies ideal gas law.

What I'm not clear about is when the tanks are opened and the flowrates are specified, what will determine the pressure in the system? This is important as I need to know and change the oxygen partial pressure during this experiment (electrical conductivity relaxation). The papers I've read about this method mention that change in oxygen partial pressure is induced by the change in the flowrate ratio (Dalton's law). This assumes that total pressure in the system is constant and therefore independent of the gas flowrates.

In another words, when the change in oxygen partial pressure is increased, why would nitrogen partial pressure decrease in this setup (or vice versa)? What mechanism is keeping the total pressure constant?

Schematic is provided to give a better insight into the process:
ECRPhoto.png
 
Last edited:
Engineering news on Phys.org
  • #2
Dario56 said:
What mechanism is keeping the total pressure constant?
The gas outlet from the sample chamber, venting to the atmosphere.
 
  • Like
Likes Dario56 and Lord Jestocost
  • #3
Baluncore said:
The gas outlet from the sample chamber, venting to the atmosphere.
That makes sense as I didn't notice the crucial detail of the system being opened to the atmosphere through the venting pipe. In another words, total pressure in this setup is always atmospheric. By changing the ratio of mass flow rates of oxygen and nitrogen, we can change the oxygen partial pressure.
 
  • Like
Likes Baluncore

What factors influence the pressure in a sealed experimental setup?

The pressure inside a sealed experimental setup is primarily determined by the temperature of the gases inside, the amount and type of gas, and the volume of the container. According to the ideal gas law (PV=nRT), pressure increases with temperature and the amount of gas, and decreases as the volume of the container increases.

How does temperature affect the pressure inside the experimental setup?

Temperature directly affects the pressure in an experimental setup through the kinetic energy of the gas molecules. As temperature increases, the molecules move faster and collide with the walls of the container more frequently and with greater force, thereby increasing the pressure. Conversely, cooling the setup will decrease the pressure.

Does changing the gas type alter the pressure in the setup?

Yes, different gases have different properties, such as molecular weight and size, which can affect the pressure in the setup. For example, heavier or larger molecules may exert different pressures at the same temperature and volume compared to lighter gases, due to differences in density and the rate of collisions with the container walls.

What role does the volume of the container play in determining the pressure?

The volume of the container is inversely proportional to the pressure inside it, assuming a constant temperature and amount of gas. This is described by Boyle’s Law. If the volume of the container is decreased, the same number of gas molecules occupy a smaller space, leading to more frequent collisions and increased pressure.

Can external environmental conditions affect the pressure inside the experimental setup?

Yes, external conditions such as ambient temperature and atmospheric pressure can impact the pressure inside an experimental setup. For example, an increase in external temperature can indirectly heat the container, thus raising the internal temperature and pressure. Similarly, changes in atmospheric pressure can alter the differential pressure across the container walls, potentially affecting the internal pressure if the container is not completely rigid.

Similar threads

Volumetric flow rate ratio calculation
    • Materials and Chemical Engineering
Replies
1
Views
443
Predicting Remaining Pressure in Compressed Gas Cylinder
    • Mechanical Engineering
Replies
3
Views
955
Pressure in a sealed vessel
    • Mechanics
Replies
4
Views
2K
How pressure affects partial pressures (and dewpoint)
    • Mechanics
Replies
10
Views
1K
What does "limit of zero pressure" mean for ideal gas temperature?
    • Chemistry
Replies
14
Views
2K
B Could Nuclear Powered Bulldozers Create a Habitable Cavity for a Mars Colony?
    • Astronomy and Astrophysics
Replies
17
Views
2K
Membrane separations experimental set up
    • Materials and Chemical Engineering
Replies
11
Views
2K
Adiabatic Expansion of Pressurized Air in a Piston-Cylinder Setup
    • Introductory Physics Homework Help
Replies
8
Views
746
Volumetric flow rate through a pipe vented to atmosphere
    • Materials and Chemical Engineering
Replies
2
Views
5K
Time to empty gas cylinder (problem worked, but would like feedback)
    • Mechanical Engineering
Replies
7
Views
749

Hot Threads

Recent Insights

Back
Top