Liquid Flow Calculation out of a pressurized tank

In summary, a chemical transport engineer is seeking assistance in calculating discharge times for a large cylindrical tanker carrying various liquid chemicals. The discharge process involves maintaining an over pressure of air in the tank and draining the fluid through a hose into an open tank. The engineer is unsure how to account for the over pressure and wonders if it should be added to the force of gravity.
  • #1
Evan Jones
I am an engineer who needs to help my chemical transport girl friend with a little basic physics. It has been about 35 years since basic physics for me so I am rusty. She wants to understand how to calculate the following:

She drives a large tanker (cylindrical) which carries a variety of liquid chemicals and wants to understand how to calculate the discharge times. When they discharge the chemicals at the destination, they pump (and maintain) an over pressure of air in the tank during the discharge process. The fluid drains through a hose into an open (non-pressurized) tank. I know the fluid properties of the various chemicals, I just need to see if anyone can assist with the calculation. Am I just adding the force of the over pressure to the force due to gravity? If this were an open tank, I know how to make that calculation from the tank, through the hoses, and into the destination tank. I just don't understand how to account for the over pressure.
 
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  • #2
The answer to your question is Yes.
 

1. How is the liquid flow rate calculated from a pressurized tank?

The liquid flow rate from a pressurized tank can be calculated by using the Bernoulli's equation, which takes into account factors such as the tank's pressure, height, and cross-sectional area of the outlet. The equation is:
Q = A √(2gh(P1-P2)/ρ), where Q is the flow rate, A is the cross-sectional area of the outlet, g is the acceleration due to gravity, h is the height of the liquid level in the tank, P1 is the pressure at the outlet, P2 is the pressure at the top of the tank, and ρ is the density of the liquid.

2. What factors can affect the liquid flow rate from a pressurized tank?

There are several factors that can affect the liquid flow rate from a pressurized tank, including the tank's pressure, temperature, height of the liquid level, outlet size, and the viscosity of the liquid. Additionally, any blockages or restrictions in the outlet or piping system can also impact the flow rate.

3. How does the outlet size of a pressurized tank affect the liquid flow rate?

The outlet size of a pressurized tank plays a significant role in determining the liquid flow rate. A larger outlet will allow for a higher flow rate, while a smaller outlet will decrease the flow rate. This is because a larger outlet has a larger cross-sectional area, which allows for more liquid to flow through at a faster rate.

4. What is the relationship between pressure and liquid flow rate in a pressurized tank?

In a pressurized tank, the higher the pressure, the higher the liquid flow rate will be. This is because as pressure increases, the liquid is pushed out of the tank with more force, resulting in a faster flow rate. However, there is a limit to this relationship as the flow rate will eventually reach a maximum value, even with increasing pressure.

5. Are there any safety considerations when calculating the liquid flow rate from a pressurized tank?

Yes, there are several safety considerations to keep in mind when calculating the liquid flow rate from a pressurized tank. These include ensuring the tank is properly designed and maintained, using proper safety equipment when working with pressurized tanks, and following all safety protocols and regulations. It is also important to consider the properties of the liquid being stored, such as its corrosiveness or flammability, and take appropriate precautions to prevent accidents or spills.

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