# Hole Sizing to Drain Fluids [Pressurized Container]

• nn2e19
In summary, the conversation discusses the process of sizing a system to get rid of fluids without any head buildup. The speaker is confused about which formula to use for their problem and is seeking clarification. They mention using the Bernoulli equation to size the hole and a different formula for calculating the pipe diameter. The expert suggests using the total head as the vertical distance from the fluid surface to the discharge end of the pipe and outlines a method for calculating flow rate using an assumed flow rate, pressure drop, and head loss through the pipe. They also mention taking into account any pressure or vacuum in the container in the head loss calculation. The expert provides a hint that the head loss will be proportional to the square of the flow rate.
nn2e19
Hello,

I want to size my system to be able to get rid of fluids without any head buildup within the container. I am just a bit confused as to what formula I should use. My problem is summed up in the following schematic. Note that P1>P2, I have assumed H=10^(-4)m and my flow rate is 0.1 m3/s, dynamic viscosity is 10^(-3) Pa.s. the pipe length is 3.2m. I do not really care about the numbers, I just want to be sure the methodology is correct.

If I use the Bernoulli eqn to size D_hole I use this: Q = Cd*Area*sqrt(2*(g*H+dP/rho)), Area = pi*D_hole^2/4

If I use the same dP and flowrate to get D_pipe I use Q = ((dP-rho*g*L*sin(theta)*pi*D^4)/(128μL))

I'm just baffled as to which one is more suitable for my problem.

Any help is greatly appreciated.

#### Attachments

• Schematic.png
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In your case, the total head is the vertical distance from the fluid surface to the discharge end of the pipe. The method I use for calculating flow rate is as follows:

1) Assume a flow rate.
2) Calculate the pressure drop through an orifice diameter equal to the pipe ID.
3) Calculate the head loss through the pipe. I use a Moody diagram for this.
4) Sum the two losses.
5) Iterate as needed until the calculated head loss matches the actual head. That's your flow rate.
6) Remember that any pressure/vacuum in the container is part of the head loss calculation.

Hint: With your dimensions, the head loss will be approximately proportional to the square of the flow rate. Use this in your iteration.

anorlunda

## 1. What is the purpose of hole sizing in pressurized containers?

Hole sizing in pressurized containers is important for draining fluids because it allows for controlled release of pressure and prevents sudden bursts or explosions. It also ensures that the desired amount of fluid is drained without causing damage to the container or surrounding environment.

## 2. How is the size of the hole determined for draining fluids?

The size of the hole for draining fluids is determined by considering the pressure and volume of the container, as well as the viscosity and flow rate of the fluid. Calculations and experiments may be performed to determine the optimal hole size for a specific container and fluid combination.

## 3. Can the hole size be too small for draining fluids?

Yes, if the hole size is too small, it may result in slow or incomplete draining of the fluid. This can lead to increased pressure buildup and potential damage to the container. It is important to carefully consider the appropriate hole size for efficient and safe draining of fluids.

## 4. Is there a standard hole size for draining fluids in pressurized containers?

There is no one standard hole size for draining fluids in pressurized containers as it depends on various factors such as the type of container, fluid, and intended use. However, there are guidelines and regulations that may dictate the minimum and maximum hole sizes for certain applications.

## 5. Are there any risks associated with hole sizing for draining fluids?

Yes, there are potential risks associated with hole sizing for draining fluids, such as the release of hazardous or toxic fluids, as well as the potential for explosions or other accidents if the hole size is not appropriate. It is important to carefully consider all factors and follow proper safety protocols when determining the hole size for draining fluids in pressurized containers.

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