Changes in internal pressure

In summary, the speaker is trying to develop a model for calculating internal room pressure using the vent opening equation. They provide values for various variables and calculate the resulting air flow and pressure difference. However, they encounter issues with the pressure difference and ask for suggestions.
  • #1
1
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I am trying to develop a basic model for calculating internal room pressure. I am using the vent opening equation. q = Cd A ((2 *delta P )/p)^0.5
If I have a set the vent 2500 mm2; A = 2.5e-3 m^2
Cd = 0.61
Internal pressure to be 102,135 and the external pressure to be 102,140;
p = 1.21205 (at 20 C)
delta P = 5 Pa.
volume = 55 m^3q = Cd A ((2 *delta P )/p)^0.5

so q = 0.004308549 m^3/s or 0.258512945 m^3/ minIf I wanted to calculate the next internal pressure,

the mass entering the room is 0.313331 kg,

Converting this back into a pressure value,
P = m * R *T / V

P = 480 Pa. So the new internal pressure is 102135 + 480 = 101715 Pa

So the next pressure difference is 475, which causes a larger air flow and a larger difference pressure the next time. It starts to spiral out of control.

Any ideas?
 
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  • #2
Jimmy Boy said:
So the next pressure difference is 475
Actually, the next pressure difference is -475, which would give a negative flow (from inside to outside).

The pressure will probably equalize before the 1 minute time difference you estimated. Reduce your time difference.
 

What is internal pressure?

Internal pressure refers to the force exerted by the molecules within a closed system against the walls of the container.

What causes changes in internal pressure?

Changes in internal pressure can be caused by a variety of factors such as changes in temperature, volume, and the number of molecules present in the system.

How does temperature affect internal pressure?

As temperature increases, the molecules within a closed system have more kinetic energy and move faster, resulting in more frequent collisions with the container walls and an increase in internal pressure.

What is Boyle's law and how does it relate to changes in internal pressure?

Boyle's law states that at a constant temperature, the pressure and volume of a gas are inversely proportional. This means that as the volume decreases, the pressure increases and vice versa, resulting in changes in internal pressure.

How do changes in internal pressure affect the behavior of gases?

Changes in internal pressure can cause gases to compress, expand, or change state. It is also a crucial factor in determining the direction of gas flow and can influence the rate of chemical reactions involving gases.

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