HP Air Bottle Sizing for 4.19m³ Tank at 10 Bar

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    Air Sizing
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Discussion Overview

The discussion revolves around calculating the amount of high-pressure (HP) air required to empty a 4.19 cubic meter tank filled with water, under two scenarios: one at atmospheric pressure and another at a depth of 5 meters. Participants seek formulas or references to aid in these calculations.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant presents two scenarios for emptying the tank and requests formulas or references for the calculations.
  • Another participant calculates that for the second scenario, 0.5 bar is needed to displace the water, and with a supply of 10 bar, the required air volume is approximately 0.57 cubic meters at 10 bar.
  • A different participant suggests that the volume of air needed is equivalent to the volume of water displaced, but notes that practical engineering challenges may prevent complete emptying due to air tunneling effects.
  • A later reply emphasizes the need for 0.5 bar psig in the tank to effectively remove water from the bottom, reiterating the pressure considerations based on the tank's depth.

Areas of Agreement / Disagreement

Participants express differing views on the calculations and practical implications of using air to empty the tank. There is no consensus on the exact amount of air required or the effectiveness of the proposed methods.

Contextual Notes

Participants highlight the importance of considering the pressure differences due to water depth and the potential engineering challenges that may affect the efficiency of the air displacement process.

Nasir6992
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Senario-1

I have a tank of Volume = 4.19 Cubic meter which is filled with water. I want to empty the tank by giving a HP air blow at 10 Bar. How much air is required to empty the tank completely.
If someone can give any formula or any reference that can help me.

Senario-2

I have a tank of Volume = 4.19 Cubic meter which is filled with water and the tank is dipped in water at a depth of 5 meter depth. I want to empty the tank by giving a HP air blow at 10 Bar. How much air is required to empty the tank completely.

If someone can give any formula or any reference that can help me.
 
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Scenario 1.
Don't understand.
scenario 2
1 bar = 10 meters of water, so you will need 0.5 bar (1.5 bar absolute) to empty the tank. Your air source is 10 bar (11 bar absolute) so your air supply wil expand by 11/1.5 = 7.33. Your water tank is 4.19 cubic meter, so you will need 4.19/7.33 = 0.57 cubic meters of air at 10 bar (11 bar absolute).
 
You simply need the volume of air to fill the tank at the pressure you are displacing the water to.

So for a 4.19 cubic meters of water at 1 bar is displaced by 4.19 cubic meters of air at 1bar. Now if the water is being displaced to a higher height than the bottom of the tank, or at a higher pressure then you need to account for the difference.

Now what I mentioned is the truth from a physics standpoint. From an engineering standpoint you are not going to get the tank empty with the volume of air required to empty it because the air will tunnel out to the drain at the bottom causing the water to start spraying at the end instead of a solid stream. If you want to get an idea of how much air you are going to need to run some sort of fluid simulations taking into account the size and shape of your tank as well as the way you introduce the air to blow the tanks. Alternatively you can just live with a small amount of water in the bottom and blow the tanks slowly.
 
chayced said:
You simply need the volume of air to fill the tank at the pressure you are displacing the water to.QUOTE]
The tank is 5 meters deep so he needs 0.5 bar psig in the tank to get the water out the bottom. His pressurized air tank is pressurized to 10 bar.
 

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