What is Compressed: Definition and 319 Discussions

Compressed air is air kept under a pressure that is greater than atmospheric pressure. Compressed air is an important medium for transfer of energy in industrial processes, and is used for power tools such as air hammers, drills, wrenches and others, as well as to atomize paint, to operate air cylinders for automation, and can also be used to propel vehicles. Brakes applied by compressed air made large railway trains safer and more efficient to operate. Compressed air brakes are also found on large highway vehicles.
Compressed air is used as a breathing gas by underwater divers. It may be carried by the diver in a high pressure diving cylinder, or supplied from the surface at lower pressure through an air line or diver's umbilical. Similar arrangements are used in breathing apparatus used by firefighters, mine rescue workers and industrial workers in hazardous atmospheres.
In Europe, 10 percent of all industrial electricity consumption is to produce compressed air—amounting to 80 terawatt hours consumption per year.

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  1. Scott Davies

    Easy way to find the potential energy in compressed air

    I have a .81 Cu. Ft. cylinder which is at a static pressure of 80 Psi. What is the easiest way to calculate the Potential Energy of the compressed air?
  2. C

    Is Space Really Empty and What Does That Mean for Propulsion?

    I guess my confusion lies in propulsion. Not fantasy, real propulsion. If space cannot be compressed then what do the expanding gases push against to gain propulsion( forward motion). All systems currently in use as propulsion in space rely on the expansion of gases that are directed in one...
  3. J

    Need suggestions on transfering compressed air to rotating object

    If you had a rotating object like a tire or barrel that you wanted to distribute compressed air to while it's rotating, what would some ways to do it? One way I'm thinking is just a tight seal at the axis, but then there would be a lot of friction. Any other ideas??
  4. B

    Compressed Springs: 100N Force, 30cm Length, k=1000N/m

    Homework Statement A man compresses a 30 cm spring against a wall. If he applies a 100 N force and the wall is rigid, by how much does he shorten the spring? (k = 1000 N/m). Homework Equations Fs=-kx The Attempt at a Solution Drew a FBD and labeled applied force of 100 N and calculated the...
  5. P

    Identical Springs: Compressed vs Uncompressed Mass

    Two springs (with indentical, invariant, Rest mass) are indentical except that one spring is compressed. Both springs are at rest. Doesn’t the compressed spring have more mass than the uncompressed spring? (With mass equivalent to the energy required to compress the spring?) Assuming the...
  6. K

    Air machine and compressed air

    Homework Statement Air at pressure 20[atm] enters an air machine and leaves at 1[atm]. what must be the temperature of the air at the entrance so that when it leaves it is 00C. Assume adiabatic process. Homework Equations PV=nRT Adiabatic: ##P_1V_1^\gamma=P_2V_2^\gamma## The Attempt at a...
  7. K

    Water flows from a compressed tank

    Homework Statement A tank of height 3.6[m] and closed at the top is filled with water to height 3[m], see drawing. the pressure P1 above the water is 1.055[kgf/cm2. A pipe is coming out from the bottom and the opening is 1.5[m] above the ground. what is the water's velocity out of the pipe when...
  8. K

    Air is compressed in a cylinder

    Homework Statement A cylinder of height 1[m] has a weightless piston on it's head. mercury is spilled slowly on the piston and it goes in. at what distance will the mercury start to spill over the cylinder. the process is at constant temperature. Homework Equations $$PV=nRT$$ At constant...
  9. stephenranger

    Using Compressed Air Tools Outdoors: Can it be Done?

    Homework Statement Car mechanics use compressed air tools to open bolts. Instead of using an air compressor one can also use a tank of pressurized air. There is an air tank with a volume of 50 L to work with. The pressure of the tank is 50 bars when it is stored indoors at 20 °C. The bolt...
  10. C

    Calculating time required to pressurize compressed air tank

    Hello, I searched as best I could but could not find a direct answer to my question; I've seen similar questions but without the required data to be able to make the calculation. I thought this would be a simple calculation to find but apparently not. Compressed air source is 4.46cfm @ 93psi -...
  11. S

    What factors determine the energy storage capacity of compressed gases?

    What defines how much energy we could store in some gas by compressing it to a certain volume by applying a certain pressure? The compessability coefficient? Is there some gases which allow to store more energy than air? Which gas has the largest compressibility coefficient?
  12. B

    Help with compressed air thrust

    I'm working on a kinda-sorta confidential device. I would like to know how much psi is required to lift approx. 400 pounds 120m (about 393ft and 8 13/32 inches) into the air. The thing I'm working on is still in the designing stage, so don't worry about the specifics of individual thrusters and...
  13. F

    Solving for Compressed Spring Distance after Collision

    Homework Statement Block 2 with mass 2kg is at rest on a surface an touching the end of relaxed spring with spring constant k=151 N/m . The other end of the spring is attached to a wall. Block 1 with a mass of 1.8kg and traveling with a speed of v=4.5m/s, collides with block 2, and the two...
  14. Warpspeed13

    Can a plasma be compressed more than other forms of matter?

    Can a plasma be compressed to greater densities than other forms of matter?
  15. S

    Compressed gas flow rate calculation

    Folks, I'm new to this thread. I'm a mechanical engineer, but I haven't done much fluids work since I graduated, 20 years ago. I have a question about calculating gas flow rate, so any help would be greatly appreciated. I have a design that I'm working on that will use a compressed gas...
  16. C

    Cooling compressed air from pump

    I have a fairly large (for household use) 7.5HP electric motor driven two-stage air compressor, which charges the receiving 80 gallon tank to a limit of 175PSI. There is a short 3/4" diameter copper pipe that connects the pump to the tank. I have not measured, but guesstimate that the...
  17. D

    Compressed vertical spring bounce

    1. First let me start by saying that there are similar posts about this, but I wasn't able to figure out what I need through those. A 3.45 kg mass vertically compresses a spring 67.0 cm before it starts to rebound. How high will the Mass move above the uncompressed if the mass is left to...
  18. M

    Simulation of Compressed Air Driven Piston

    I am writing a MATLAB script that generates a dynamic simulation of a piston being driven by compressed air. My starting values for pressure and volume are as follows: P0 = 14000000; %nm-2 or 140 Bar V0 = 0.005; %m3 or 500cc The simulation needs to be quite detailed and must take into account...
  19. J

    Compressed air flow rate from pipe to container

    Hello All,I was given a problem today that I could use some guidance on. I have a compressed air pipe flowing into a container. This container has a pressure of 5 psi while the pipe has a pressure of 90 psi. There is a valve that controls when the air is released into the vessel and only...
  20. M

    Alternate shapes for compressed cylinders

    Good Morning everyone.. Has there been discussion on here regarding alternate shapes for compressed air cylinders (+3000 psi) I know why compressed cylinder are the shape they are, but in this day and age of science & technology, why are we still using round cylinders? could one not design a...
  21. M

    Cylinders compressed by pressure

    Hello all, some colleagues and I have run across a problem that we cannot seem to explain, I was hoping to find some guidance here. The problem came about from messing with an air over hydraulic system. I have attached a very rudimentary mspaint picture with our scenario. Using 3 in place of...
  22. M

    Why does releasing compressed gas cause the container to cool down?

    Preface- I am a scum noob who doesn't know much. Why does a compressed gas cool a container down when released? I mean in terms of imaging the actual gas molecules moving around. For instance, I can imagine why water on the skin evaporating could cool a person down. The body transfers...
  23. S

    Can a Gas Remain the Same Temp When Compressed?

    So today I came across this question: 2) CHEMISTRY Multiple Choice Which of the following statements is NOT true: W) an ideal gas cannot undergo condensation X) the less mass a particle has, the faster it will effuse Y) when a gas is compressed, its temperature always increases Z) a...
  24. I

    Calculating the effect of humidity volume and temp of compressed air

    This isn't homework, I'm a hobbyist, not a student. Posting here because questions I've previously posted were moved to this section. My intent is to better understand humidity and it's role in compressed air for an automotive application. All help and direction is greatly appreciated. Thank...
  25. F

    Compressing Water: Can It Be Done?

    Okey I know that this title is somewhat misleading. Here we go Me and a friend started to discuss what would happen if someone took one unit of water and turn it into a gas and then rapidly compressed the gas before then cooling it down to room temperature. I know that one can not...
  26. Astrum

    Blocks and Compressed Spring

    Homework Statement Two blocks of equal mass, connected by a masslless spring of constant ##k## are on an air track. her unstreched length of the spring is ##L##. at ##t=0## block ##b## is compressed to distance from block ##a## at ##l/2## (block ##a## is pressed against a wall). Find the motion...
  27. W

    Compressed oxygen for jet engine (?)

    as jet engines lose there productivity at altitude due to thining air/oxygen , why isn't injecting compressed air directly along side the fuel a good idea ? , is this already being done ? would /does this not increase ceiling height and allow sub orbit levels or possible leave atmosphere...
  28. C

    Pressure to volume relationship in compressed air

    Hi guys need help. We've been encountering compressed dry-air related problems here in our plant. Most machines pressures were fluctuating when their equipments are running. As I've checked, the problem is not regarding the pressure since the line pressure is 10psi higher than machine...
  29. M

    Calculating compressed air expansion when heated

    Can anyone help me with this calculation? I'm trying to figure out how much compressed air (generated from screw compressor) will expand by a ratio of what when fed into a wood furnace. 1) Wood Furnace Fuel Input: 30kg dry wood fuel/hr 2) Compressed Air Pressure: 8 bar 3) Compressed Air Flow...
  30. S

    Calculating the volume that a compressed mass of air will occupy.

    Homework Statement This question is to due with a compressor experiment. I've actually posted 2/3 questions on this write up in the past 2 days. Anyway, a compressor takes air from the atmosphere and compresses it before forcing it into a receiver volume. You are asked to calculate the mass of...
  31. H

    Compressed Air Tank: Temp & Condensation

    If I allow a tank that's pressurized(3000 psi) and initial temp (121) to cool to room temperature (25 C), will that increase the rate of condensation or is there a fixed amount of condensation that occurs while at that pressure? Having a tough time understanding that phenomenon. If no change in...
  32. J

    Compressed air car problem FUN

    Background: This is my first post here on physics forums. I have perused for quite a while. I am a Chem Eng. student at University of Houston and this question is from my Thermodynamics class. I have enjoyed working on this problem (for hours) but am certain i have made a mistake...
  33. cyberdiver

    What if the moon was compressed to palm size?

    In the recent hubbub centring on Despicable Me 2 (bear with me), I recall the first film when the protagonist stole the moon by using a shrink ray to shrink it to fit in his palm. My question is, what would happen in real life if such an absurdity was committed? For one, shrinking the moon would...
  34. Q

    Please HELP: A block of mass 2.5 kg is placed against a compressed spring

    Homework Statement A block of mass 2.5 kg is placed against a compressed spring (k = 2900 N/m) at the bottom of an inclined plane. When the spring is released the block is projected up the incline and the spring expands by 14 cm to its normal length. Calculate the maximum distance traveled by...
  35. B

    Heat energy change when gas compressed

    Homework Statement One mole of an ideal gas is in a container with a moveable piston. A 100 N force moves the piston down 1 m; the compression is isothermal. Does 100 J of energy leave the gas or enter the gas? Homework Equations W=Fd U=Q-W=Q-P(Vf-Vi) The Attempt at a Solution...
  36. G

    Does Mass Occupying Volume in a Compressed Air System Transfer Energy

    In a compressed air space there is a suspended mass with 10 cubic meters volume. The pressure vessel is 20 atm. The suspended mass is suspended 100 meters over water that is kept at bay by the air pressure inside the vessel. The moment the mass is released its potential energy converts to...
  37. Ackbach

    MHB Solving Holt Physics Prob. 49 Concerning Comp. Spring w/Friction

    Problem: A light horizontal spring has a spring constant of $105 \; \text{N/m}$. A $2.00\; \text{kg}$ block is pressed against one end of the spring, compressing the spring $0.100 \; \text{m}$. After the block is released, the block moves $0.250 \; \text{m}$ to the right before coming to rest...
  38. L

    Calculating the distance the spring was compressed

    A 1300 g mass is on a horizontal surface with μk = 0.380, and is in contact with a compressed massless spring with a spring constant of 600 N/m. When the spring is released, it does 8.61 J of work on the mass while returning to its equilibrium position. Calculate the distance the spring was...
  39. B

    Entropy Change of a Monatomic Ideal Gas Compressed Adiabatically

    Homework Statement A monatomic ideal gas is compressed adiabatically. What is ΔS of the gas? n = 1.00 vi = 10.00 L vf = 4.00 L Constant External Pressure = 50.00 atm Homework Equations ΔU = q + w = 0 + (-PextΔV) ΔS = ∫[(qrev)/T]dQ The Attempt at a Solution In order to...
  40. Y

    Adding pipes for compressed air delivery

    Hi all! I have a problem here, anyone here knows what will be the effect on pressure and flow rate of compressed air by adding additional pipes leading out from my compressor? For eg. if i were to increase the number of delivery pipes from 1 to 2, will the flow be slpit evenly between the two...
  41. T

    Friction of a pipe and the effects on compressed air?

    Let's say a receiving device that requires compressed air is 1.5 miles away from the source and demands 600 cubic feet per minute. Let's say the pipes have a diameter of four inches and already contain air at 90psi. If friction in the pipes would be ignored, it would require the same amount...
  42. C

    Force / Thrust from Compressed Air Container 90ci/4500psi

    Hello All, I was wondering that what is the force/thrust we can get from 90ci/4500psi compressed air container, which are available in market for Air guns. Also how long that force will last continuously (2 min or 5 min or more) ? For more info about the container ...
  43. N

    Positive/Negative Pressure Control of Syringe using Compressed Air and Vacuum Pump

    I would like to try and set up a pressure control system in my lab using house vacuum and compressed air. Or otherwise using a compressed air source and vacuum pump. I want to be able to control the pressure in a reservoir (a syringe) within the range of -15 to +15psi. I was thinking...
  44. I

    Temperature drop when expanding heated compressed air

    Homework Statement I need to know how much the temperature drops after an inline heater which heats an airflow of 5 lbs/min up to 88 °C with an pressure of 54 PSI. When the air exits the heater it is released into the free air where it is 20 °C. I know that the air will expand to a...
  45. P

    Why do compressed materials fail in shear?

    Why when you compress materials like concrete do they fail in shear? Can the thing you're compressing be too small to fail in this way?
  46. S

    Conservation of energy, how far must a spring be compressed

    Two children are playing a game in which the try to hit a small box on the floor with a marble fired from a spring loaded gun mounted on a table. The target box is horizontal distance D=2.20 m from the edge of the table. Bobby compresses the spring 0.011m but the center of the marble falls 0.27...
  47. S

    (?) on fixing bootmgr is compressed

    I accidentally somehow compressed something on my computer and am getting this message "bootmgr is compressed". I think I did it when i was compressing stuff on my hard to conserve space. How do i fix it?
  48. H

    Compressed air lift question (thermodynamics)

    Homework Statement A platform is supported on a piston by compressed air in a cylinder. The mass of the platform and equipment being lifted is 1100kg. The pressure needed to support this mass is 800kPa, and it rests initially at a height of 0.5m. The pressure supply is closed so that no gas...
  49. N

    Work done on compressed gas

    Homework Statement Pt. A) A gas is compressed at a constant pressure of 0.632 atm from 7.11 L to 5 L. In the process, 440 J of energy leaves the gas by heat. What is the work done on the gas? Answer in units of J Pt. B) What is the change in its internal energy? Answer in units of J...
  50. C

    Initial Compressed Spring Force

    Homework Statement A spring has a relaxed length of 0.17 m, and its stiffness is 15 N/m. The spring sits vertically on a table. You place a block of mass 0.058 kg on the spring and push down on the block until the spring is only 0.11 m long. You hold the block motionless on the compressed...
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