How much power required to generate a particular pressure

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SUMMARY

The discussion centers on the power requirements for pressurizing a cylinder, emphasizing that there is no universal formula connecting power and pressure. It highlights the differences in energy storage between incompressible fluids like water and compressible fluids like air, particularly in the context of diving cylinders. The power needed varies significantly based on the method of compression (isothermal vs. adiabatic) and the speed of air input, with practical examples illustrating that a car tire can be inflated using various methods, each with different power outputs. Ultimately, the time taken for compression plays a crucial role in determining the power required.

PREREQUISITES
  • Understanding of isothermal and adiabatic processes
  • Familiarity with the principles of fluid dynamics
  • Knowledge of pressure measurement units (e.g., kPa)
  • Basic concepts of energy and power calculations
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  • Research the equations for isothermal and adiabatic compression of gases
  • Explore the impact of temperature on gas compression efficiency
  • Investigate the specifications and power ratings of various air compressors
  • Study the safety protocols for pressurizing gas cylinders
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Engineers, technicians, and hobbyists involved in pneumatic systems, diving equipment manufacturers, and anyone interested in the principles of gas compression and safety in pressurization.

escape_velocity
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Are there any general guidelines or rule of thumb regarding how much power in watts would be required to pressurize a cylinder to a particular pressure and can I use this as a general rule,

For eg. I want to pressurize a vessel of volume 1 cu. m how much power would be required and can we generalize this so the this formula can be applied to a vessel of any volume?
 
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There is no meaningful general relation between power and pressure. Not even between energy and pressure.
 
Testing divers' compressed air cylinders is done by pressurising them with (nearly incompressible) water). If they 'fail' catastrophically, they just form a split and there is very little disturbance. There is very little energy stored.
OTOH, if a cylinder fails when being over-pressured with air, you have a BOMB on your hands. So much more energy involved. You can pressure test a cylinder with a few strokes of a manual water pump but an air compressor (a few h. p.) runs for minutes and everything gets too hot to touch.
No simple rule to connect the two. [emoji846]
 
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sophiecentaur said:
No simple rule to connect the two. [emoji846]
What if I say that the fluid is "air" now would there be an equation for power to pressurize a cylinder with air to a particular pressure?
 
escape_velocity said:
What if I say that the fluid is "air" now would there be an equation for power to pressurize a cylinder with air to a particular pressure?
OK But that is still not specific enough. Are we doing this quickly or very slowly? (Isothermal or Adiabatic) Diving cylinders are kept cool (in a water bath) during compression or their 'final' pressure will go down as their temperature drops.
Actually, if you Google Divers' Air compression, you may find some actual examples. That could answer your question if it is practical rather than theoretical.
 
The pressure (and other info such as temperature) give you the energy stored in the tank.

Power = ΔEnergy/ΔTime so to calculate the power you need (at least) some info on how fast you are putting the air in.

Even then it's not that simple because (as Sophiecentaur says) the temperature may also depend on how fast you put the air in and factors such as the thermal mass of the container, how well insulated it is etc.

How accurate an answer do you need?
 
sophiecentaur said:
OK But that is still not specific enough...
Actually, if you Google Divers' Air compression, you may find some actual examples. That could answer your question if it is practical rather than theoretical.
Let me provide some examples in hopes they may help:

Say, you are pressurizing a car tire to 200 kpa. You can:
1. Use a base mounted compressor with a tank, which can provide compressed air at thousands or tens of thousands of Watts.

2. You can stomp on a foot-pedal pump for a peak power of perhaps a thousand Watts.

3. You can use a hand-held bike pump with a peak power of perhaps 50 Wattts.

As you can see, all of these give the same result (an inflated tire) but require/use vastly different power to do it. The main difference is how long it takes. So you see, there is more to finding the power required than just the final pressure.
 
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