Under pressure -- flow rate through multiple holes in a pipe

In summary, to calculate the total volume of air in nm3/hr that will escape a pipe with 40-2 mm round holes under a constant pressure of 350 mbar, you can use the equations on this website to define the velocity of the fluid and then multiply it by the total exit area of the holes. The velocity must be in m/hr and the area in m² to get the answer in m³/hr.
  • #1
Bruce Center
1
0
I am looking at air system that is under a constant pressure of 350 mbar into a pipe that has 40 - 2 mm round holes. Is there a formula that I can use to calculate the total volume of air nm3/hr that will escape the system?
Let's just say the air temp is constant.
Can anyone help with this?
 
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  • #2
On this website, you have the equations to define the velocity of your fluid based on your known pressure drop in the section Static, dynamic and total pressure, flow velocity and Mach number ([itex]\gamma[/itex] = 1.4 for air). You will have to do trial and error to find it since M = v / c (where c = 343 m/s at 20°C, see speed of sound for air). The density [itex]\rho[/itex] is defined in equation (8) based on Mach number where [itex]\rho_t = \frac{P_t}{RT_t}[/itex] where [itex]P_t[/itex] & [itex]T_t[/itex] are the pressure (in Pa) and temperature (in K) of your air when at rest (may be your initial pressure and ambient temperature if your air inside the pipe can be assumed to be immobile) and [itex]R[/itex] = 287 J/kg/K for air.

Then you multiply that velocity by your total exit area of your holes to get your volumetric flow rate. The velocity must in m/hr and the area in m² to get the answer in m³/hr.
 

1. How does the number of holes in a pipe affect the flow rate?

The number of holes in a pipe can significantly affect the flow rate. As the number of holes increases, the total cross-sectional area for the fluid to flow through also increases. This means that more fluid can flow through the pipe at a given time, resulting in a higher flow rate.

2. Is the flow rate through multiple holes in a pipe equal to the sum of each individual hole's flow rate?

No, the flow rate through multiple holes in a pipe is not equal to the sum of each individual hole's flow rate. This is because as the fluid flows through each hole, it experiences friction and pressure loss, which reduces the overall flow rate.

3. How do the size of the holes affect the flow rate through a pipe?

The size of the holes in a pipe can have a significant impact on the flow rate. Smaller holes will result in a higher velocity of the fluid, which can lead to increased pressure loss and a lower flow rate. Larger holes, on the other hand, will allow for a higher flow rate due to a lower velocity and less pressure loss.

4. Can the flow rate through multiple holes in a pipe be controlled?

Yes, the flow rate through multiple holes in a pipe can be controlled by adjusting the size and number of the holes, as well as the pressure and velocity of the fluid. By manipulating these factors, the flow rate can be increased or decreased as needed.

5. What other factors can affect the flow rate through multiple holes in a pipe?

Aside from the size and number of holes, other factors that can affect the flow rate through multiple holes in a pipe include the viscosity of the fluid, the length and diameter of the pipe, and the overall design and configuration of the system. Additionally, external factors such as elevation changes and external forces can also impact the flow rate.

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