What is Compressed air: Definition and 145 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.

View More On Wikipedia.org
Recent contents Top users
  1. V

    Looking for a compressed air formula

    I know what the formula for the Volume of a cylinder is. If I had say a 25lbs weight and dropped it from the top into the cylinder and lost no air , where would it stop(in inches from the bottom of the cylinder)? Not carrying about temp of the air or moisture. Is their a some what simple...
  2. S

    Calculating compressed air system leakage

    I am looking to quanitfy our compressed air system leakage and have followed the usual steps of ensuring all air consuming products are off and then measuring load/unload times. I intended to use the following formula as found in relevant articles and webpages: % Leakage = (Tx100) / (T+t)...
  3. J

    The temperature of the compressed air in a diesel engine

    Hi, Could someone tell me the rough temperature the air gets to under compression, just prior to the diesel being injected and auto igniting? thanks in advance
  4. V

    Potential energy of a cylinder inside a tube filled with compressed air

    Let the cross sectional area of the tube be given by A and the position of the cylinder by s, and assume that the gas is ideal so that the pressure times the volume (Ω) is a constant. i.e. pΩ = constant. Show that the potential energy of this compressed gas is given by V =...
  5. S

    Doing a compressed air survey on your plant

    Hello fellow PF-friends. I'm in the works of doing a compressed air survey where we wish to look at the savings potential for our plant. As there's a lack of control and overview we're going back to the basics (which means I have to start from scratch). I'm physically tracking the largest...
  6. M

    Compressed air aftercooler questions

    I am the head electrician at Panorama, a ski-resort in SE BC. It is my job to identify & take action on energy improvement measures… This usually doesn’t involve consulting physicists, but now I have something beyond my experience. Our snow-making plant uses 3 x 800 HP centrifugal...
  7. N

    Compressed Air Car: Feasibility & Analysis

    hi there, i am studying the feasibility of compressed air to power a car as my final year project and i need some guidance. How i proceeded: (1) I derived equations for the driving force and consequently for the road-load power of a car, with speed as the variable. (2) I worked backwards...
  8. M

    Temperature of Compressed Air

    Hello, We all know that if you compress air the pressure and temperature increase together. But how can I calculate the relationship? For example: What pressure (psi) do I need to compress air to so it is 100degC? Many Thanks, Matthew.
  9. N

    Calculating CFM for Compressed Air Venting Down to Atmospheric Pressure

    Hello gentlemen! I'm rather new to this whole complex world we call compressed air. :) Put simply, I have spent the past 4 hours trying to find this answer anywhere and I am just not informed enough about all these numbers to get what I need to find out. I have an air cylinder that is...
  10. V

    Jet Engine Compressed air Pressure for various altitude and velocity

    HI In Jet Engine, i want to know that the compressed air prssure changes before it enters into the combustion chamber from the compressor in various altitude and velocity or it is consatnt for altitude and velocity?
  11. M

    Designing a Small 5W Generator from Compressed Air

    I'm looking to drive a small, 5 watt generator from compressed air (psig>60) and while being fairly frugal with the air (<.25 ft^3/min). I hope to have the base and spindle cut using a common three axis mill. Hears where I need help - I don't know how the control surfaces should be shaped or...
  12. M

    Velocity of compressed air blowoff

    Here's my situation - I have a centrifugal compressor blowoff line that is creating too much noise. I am being told that the velocity through the pipe may be too high. Values as follows - 3" globe valve increasing to 4" diameter sch 40 pipe 17.5 feet long, increase to 8" sch 40 before silencer...
  13. A

    Calculating the force provided by an opened compressed air tank

    Hey. Quick question. If we have a compressed air tank of 550 kPa with a opening area of 0.25 cm^2, would the force provided just be P*A so it'd just be 550 * 0.25 (with appropriate conversions to metres and pascals etc). We are looking for the force that'd be provided to a model car that the...
  14. kandelabr

    Designing a compressed air car

    hello, lately I've been thinking how to roughly design a compressed air powered car. i'd take an existing commercial car, take out its IC engine, fuel tank and all the other stuff and mount my own machine and tanks in. i want it to travel 300 km (185 miles) at speed of 90 km/h (55 mph)...
  15. R

    Compressed air explosing or fire

    Please every1 put your 2 cents in. I joined this forum as a few of my buddys are arguing about compressed air. here is the situation. We have a car with a air compressor (not an oxygen tank) in the trunk the car is rear ended and catches on fire, during the accident the tank was broken open...
  16. N

    Will Compressed Air Increase the Danger of a Car Fire?

    ok guys here is the scenario: a moving car at an arbitrary speed carrying a cylinder of compressed air on the trunk. A car crashes into the rear of the car causing a fire mixed in with the leaking fuel from the gas tank. The tank ruptures on impact and releases the air..will this air make the...
  17. D

    Future - Innovation in Compressed Air Technology

    Let's talk about the future of compressors and compressed air technology. Of course, the first compressor appeared a long time ago and the technology is developing to provide more efficient and modern models. Do you see any breakthrough innovation for this technology in the future, like a move...
  18. G

    What Is the Density of Compressed Air?

    does anyone happen to know the density of compressed air?
  19. M

    Compressed air storage for energy production

    Hi everyone! This is the first time I post a topic here so forgive me if there are some shortcomings. I have just taken a project about design and implementation of a compressed air storage and then release compressed air to produce electricity. This is not new project and has been installed...
  20. V

    How to calculate compressed air temperature and pressure

    How to calculate compressed air temperature and pressure at combustion chamber inlet? Small Example I want to calculate compressed air temperature and pressure at combustion chamber inlet in single stage centrifugal compressor, RPM = 10 000 Temperature and Pressure of the Air before...
  21. C

    Using Compressed Air to Lift a 400lb Load

    can compressed air be used to lift a load of 400lbs about 30 feet into the air i came up with using an air compressor to route compressed air into 4 small rocket nozzles to lift it off the ground how powerful of an air compressor would i need if i wanted a constant thrust of 500lbs coming...
  22. D

    Heating compressed air to provide lift

    Just a question about heating compressed air.. I know generally how hot air works.. You heat it and particles expand and creates lift. So my question is, Does heating compressed air provide any lift? if so how much in relation to normal air? eg if I had 100m^3 of air heated to 120C...
  23. W

    Compressed air at high pressure can cause frostbite?

    Is it possible to get frostbite from compressed air? How does this happen?
  24. S

    Compressed Air Pressure Drop Across a Restriction

    I would like the formula that describes the reduction in pressure that results when a constant flow (cfm) of compressed air travels from a 3" diameter pipe through a bell reducer that provides a smooth transition to a 1.5" diameter pipe. Also, in the same piping configuration as described...
  25. J

    Soft drink bottle using compressed air for thrust to act like a rocket.

    Hey! This is the first time I have used this forum so I hope it all goes well and I am sorry if I break any rules on my first attempt. I have been given a question which I believe will involve quite a lot of work, so I thought I would get some suggestions as to where I need to start...
  26. A

    Compressed Air Bottle Rocket (Variable Mass)

    Homework Statement I need to find the maximum distance a rocket (which is actually a bottle filled with compressed air to 654kPa) can travel when the exhuast nozzle is 22cm (and can be changed to any smaller size if needed). Neglect air resistance. The bottles original mass is 50g...
  27. A

    Velocity of air in compressed air tube

    This is more like personal homework and I have searched everywhere to find the answer to this with no luck. I was watching mythbusters re-runs the other night and the hurricane episode was on. They were trying to prove that straw could go through a tree in hurricane force winds. What...
  28. K

    Lifting power of Compressed Air

    Hi, Question: Is the Lifting Power of Air in Water solely based on its Volume or does the pressure of the Air factor in? As an example, in Salt water if you have a Bell with 2 Cubic ft of Air in it, at the Oceans Surface it can lift 128 Lbs, because air can lift the amount of Water it...
  29. K

    Energy stored in compressed air?

    Hi, I am trying to figure out how much energy is stored in compressed air. I have figured out that a device I am looking at compresses about 174 cubic feet per minute into 35 cubic feet and that the temperature would rise from 70 F to 550 F. I now want to know how much energy, in the form...
  30. magi

    Wood fire in compressed air chamber?

    Hi. What happends when i put fire to wood that I have in a chamber with a pressure of about 15 kg/cm2 = 14.710 Bar = 213,3 Psi. Will it burn as usuall or much faster? Will I get a very high pressure? How High pressure can I get? Magi
  31. K

    Filling small compressed air bottle with a big one

    How can I figure the pressure in a 80 cubic inch tank at 0 psi being refilled with a 8000 cubic inch tank with a pressure of 3600 psi?
  32. S

    Heating Time of Compressed Air

    HI, If you compressed 300 litres (about 12 moles) into a 3 litre cylinder which was already at 3,000 degrees C. Would the air reach this temperature in an instant? Im trying to get my head around this stuff about heat capacities and amounts of energy needed to heat materials. Please...
  33. D

    Can Electric Cars Be the Solution to Efficient and Non-Polluting Transportation?

    The compressed air car is a much desired development in the search for an alternative cleaner, non-polluting form of motivating power that can be used in transportation. For the past 150 years the IC Piston engine, working on the Otto cycle and first invented in 1866 by Nicholaus Otto, has been...
  34. H

    Compressed Air Cars: Benefits & Concept

    hey guys can any1 tell me wats the concept behind cars using compreesed air as fuel...
  35. G

    Calculating Compressed Air Propulsion: Methods and Formulas for Model Torpedoes

    Hi, I'm currently designing a model torpedo and plan to use compressed air for it's propulsion and am working out if it's feasible. At the moment I'm trying to calculate how long it takes for X volume of compressed air at Y pressure to leave (IE return to atmospheric pressure) through a...
  36. U

    How Many Air Molecules Were Released from the Compressed Tank?

    A tank of compressed air of volume 1.0 m^3 is pressurized to 50 atm at T = 273 K. A valve is opened and air is released until the pressure in the tank is 17 atm. How many air molecules were released? I tried this problem using PV = NkT and PV = nRT. I realize the difference in these...
  37. M

    Removing oil aerosols(mist) from compressed air

    Hello! My process looks like this: i've oil container with constant vacuum of 3-10 mbar for removing oil aerosols from container.that vacuum is produced by ejector(vacuum pump) down the line in which goes air at 6 bar.oil aerosols then together with air goes to atmosphere. what I'm trying to...
  38. S

    Calculating Electric Power Output of Compressed Air System

    Hello, I am interested in finding out the electric power output from a compressed air system. i see that there is a formula for calc. it with the amount of compressed air required to generate about 1 W with a pressure of 1 bar is given by Compressed air(cu.mm/s) = (1000 N-mm/s) / (0.1...
  39. Pengwuino

    Compressed Air Can Mystery: What's Going On?

    I was wondering something. I have this can of compressed air and when its upright and used, it fires out a bunch of air. If i turn it onto its side where the nozzle points up however, half the time the air is actually visible! (or too cold?). What is causing this? It also does it when you turn...
  40. U

    Compressed Air Car: Moving 70kg Person w/ 135 PSI Tank

    I'm building a compressed air car that will move a 70 kg person and I'm wondering how far it can go off a 135 PSI tank with 10 gallons. The vehicle should have a mass of at most 80 kg and I'm trying to figure out how to do calculations with a coefficent of friction of 0.5. Can anyone help me...
  41. J

    Water content in compressed air

    Hi- A recently installed natural gas main is showing evidence of water infiltration. Water is getting into the customers regulator and meter and freezing. The gas main was cleaned and "pigged" after the installation. The system is currently operating at an MAOP of 60 PSIG natural gas. When...
  42. P

    Interesting new concept car-runs on compressed air

    Interesting new concept car-runs on compressed "air" link here : http://www.theaircar.com/ thoughts ?
  43. D

    Compressed Air n' Pressure Question

    Does anyone know of an internet site that discusses the properties of compressed air in a tank, and how the air behaves when it is released from the tank. Also, is there an equation which describes the rate at which air leaves through a valve of a tank? Thanks much
  44. Ivan Seeking

    MDI's Compressed Air Technology Systems: C.A.T's ©(*).

    http://www.theaircar.com/howitworks.html also: http://auto.howstuffworks.com/air-car1.htm I haven't studied this yet but to me this seems an unlikely technology. This must be terribly inefficient. It even strikes me a bit as a scam - clean technology? Comments?
  45. brum

    Cars powered by compressed air

    http://auto.howstuffworks.com/air-car.htm
Back
Top