Volume of compressed air question.

In summary, the conversation is about a person asking for help with a personal project involving compressing air in a container up to 100psi. They are trying to figure out how many strokes of a single cylinder compressor will be needed to achieve this and are seeking guidance on how to calculate the number of strokes required to increase the pressure from 50psi to 60psi. They are also discussing the use of Boyles Law and seeking clarification on certain mathematical concepts. Another person suggests using a specific equation to calculate the number of cycles needed and recommends wearing safety gear when working with compressed air. The conversation ends with a simplified explanation of the process using the ratio of absolute pressures.
  • #1
Flint
4
0
Hi,

Can anyone help me with a personal project I am working on?

I wish to compress air in a container up to 100psi. I'm making a small single cylinder compressor to achieve that. The container is small, approx 0.05 cubic feet.

I'm trying to work out how many strokes of the compressor it will take. I know the swept volume of the compressor. Am I right to assume that the number of strokes required against pressure is not linear? I have researched Boyles Law etc but I'm just getting confused!

How do I work out how many strokes to get from say, 50 psi to 60 psi?

Any help would be much appreciated.
 
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  • #2
I was hopeful that one of the over a hundred people that have viewed my question might have been able to help. Any takers? I really need a bit of guidance here!

:smile:
 
  • #3
Sorry man, I don't have an experience in working with something like this.
 
  • #4
Each stroke adds the same volume of the gas. Calculate total volume added by n strokes (hint: no pressure changes, each volume is just of the atmospheric air entering th ecompressor). Apply Boyles law - P1V1 are atmospheric pressure and total volume of the gas put into tank, P2V2 are pressure and (known) volume of the main tank. There is only one unknown here.

Note: This is a homework or homework type problem, so it should be posted in the HW section.
 
  • #5
Hi Borek,

Thanks for the reply. I'm not sure I understand it though - yet. I'm good at many things but maths is not one of them!

It might sound like a Homework question but I assure you I left school a good while ago! I placed the question here as I thought it was similar to many others being asked and thought it appropriate.

I'm still in the dark here so perhaps I could rephrase it in the manner of a HW question i.e.

QUESTION: Calculate number of cycles required to increase tank internal pressure from 0 to 50psi.

If :

X = compressor volume

V2 = Tank Vol

n = compressor cycles

P1= Atmos. pressure (I assume because I want a relative increase, this will be 0 and not 14.7psi?

P2 = Final pressure in tank

Could it be presented as an eqauation i.e. n= ?

If you still think I should put this in the HW section should I ask again there?

Best regards

Les
 
  • #6
http://www.egr.msu.edu/classes/me416/Compressor.pdf [Broken]

This site might be helpful. Do you know inlet temperature and mass flow rate of the air?
 
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  • #7
You know the volume of your tank, you know what pressure you want to achieve assume that the final temperature in the tank will be the same as the atmosphere.
Think about the tank at full pressure and calculate using Boyles law the volume that the air in the tank would occupy if you opened the valve and let it out to atmosphere.
Calculate the volume of your pump
Divide the first number by the second number for the number of strokes.
When using compressed air (especially with home made kit) as a minimum wear a pair of safety glasses at all times.
 
  • #8
Flint said:
Atmos. pressure (I assume because I want a relative increase, this will be 0 and not 14.7psi?

No, you are intested in ratio of absolute pressures.

If you still think I should put this in the HW section should I ask again there?

I have already moved the thread.

See Jobrag answer. While he states basically the same I did, he uses different angle, so perhaps it will be easier to catch for you.
 
  • #9
This is a good question and not too hard to visualize. Take a empty volume at a pressure of 14.7 psi absolute and raise it to 114.7 psia. This is a ratio of 7.8. Therefore the number of strokes is equal to 7.8 * Vtank/Vstroke where Vtank is the volume of the tank and Vstroke is the volume of the stroke. So, if the tank is 1 cu.ft and the stroke is 1 cu ft, then it would take 7.8 strokes to fill the tank.
 
Last edited by a moderator:

What is the definition of "volume of compressed air"?

The volume of compressed air refers to the amount of space occupied by a certain amount of air that has been compressed to a higher pressure than atmospheric pressure.

How is the volume of compressed air measured?

The volume of compressed air can be measured using various units such as cubic feet, cubic meters, or liters. It can also be measured using pressure and temperature values and the ideal gas law equation.

What factors affect the volume of compressed air?

The volume of compressed air is affected by the initial pressure of the air, the temperature, and the final pressure after compression. The type of compressor and the amount of time the air is compressed also play a role in determining the volume.

Why is the volume of compressed air important?

The volume of compressed air is important because it determines the amount of air that can be stored in a compressed air system, which in turn affects the performance and efficiency of the system. It is also important for safety reasons, as over-compressing air can lead to explosions.

How can the volume of compressed air be increased?

The volume of compressed air can be increased by using larger tanks or compressors, reducing the initial pressure of the air, or using a refrigerated dryer to lower the temperature of the air before compression. Proper maintenance of the compressor and regular checks for leaks can also help to increase the volume of compressed air.

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