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. M

    Compressing Water: What Happens and Is It Possible?

    what happens to the atoms in water when it is compressed so much that all atoms have no space to move? im guessing that it will become thicker, almost soup like. But what happens after that, does it become solid water? also, is it possible to set up such an experiment in the real...
  2. Vorde

    Dispose of Compressed Air Can Safely on Hot Day

    For starters, I have no idea where to post this question but I think this is a good place. Earlier today I bought a compressed can of moisture-less duster to clean my computer fans with. That is all good, but when I was done I wasn't sure where to dispose of the can. Normally it would be...
  3. S

    Reusing lost energy from Compressed air

    Why is Heat not normally trapped when compressing Air, and reused again in the expansion process of the same air?
  4. E

    Can mass be compressed indefinitely?

    Hello, I am really new here and I am not sure if this is in the right secion, i just got a question about something I've thought about for a while. If we assume that there is an infinite amount of energy in the universe, does that mean that there would teoretically be no limit on how much an...
  5. R

    How do you calculate BTU of expanding compressed air

    I would like to know if there is a measure, in BTU's, of the cooling effect from the release of compressed air through a nozzle and how it relates to PSI
  6. N

    Force transfer from compressed spring

    Homework Statement I have a metal spring 50mm in diameter 152 mm long compressed to half its length ie 76mm by using a weight of 50kg. I have used a clip to hold it compressed. When that clip is broken the spring will expand back to its original length of 152mm. How can I work out how far it...
  7. H

    Automotive How can heat management be optimized in compressed air powered bikes?

    hey mechies, i know "compressed air powered bike" is one of the oldest concept of our engineers but still in their developing stage.. i am in my final year of mechanical engineering undergraduate course. And i am about to do final project by end of this year.. when searching for real time...
  8. B

    How Does Heat Transfer Affect Compressed Air Energy Storage in Salt Caverns?

    Hi all, I am trying to model temperature variation with time of compressed air energy storage in a salt cavern. For now I have considered a spherical (hollow) cavern in which air is injected. I have to solve [U]{T}+[M]{T_dot}={Q} (here, Q is the first term and all other entries are zero)...
  9. Y

    What happens to carbon monoxide when compressed or put under high pressure?

    What happens to carbon monoxide when compressed or put under high pressure?
  10. P

    Model airplanes powered by compressed air ? Anyone ?

    Model airplanes powered by compressed air ...?? Anyone ?? Hello, Has anybody explored idea of powering aeroplane models by compressed air? Does this seem to be viable idea? Prima-facie: Let's say a rubber tire tube (old days of car tires - now its all tube less) inflated to say 60...
  11. D

    Compressed air discharge calculation for CFM and volume

    Ok here is my problem. We have a static value that we use for determining the cost of air based on the pipe size and the CFM used. What I have is the size of the pipe openings and what my constant static pressure is. The air is being blown into a vacuum. System details: Lead pipes is 4...
  12. B

    Dart Energy from Compressed Air

    Hi Everyone, I am trying to calculate the exit velocity of a dart which is propelled by compressed air. Please see the attached jpeg for diagram and my work so far. My final formula appears to be incorrect. I'd appreciate any help figuring out what is wrong. A pressure tank of Volume...
  13. Physics Monkey

    What are some recommended resources for an introduction to compressed sensing?

    Not sure if this is best subforum for this ... but what I'm looking for is some recommendations for books/articles containing a nice introduction to compressed sensing. I'm not a mathematician although I would like to think I'm relatively mathematically sophisticated. I appreciate proofs in...
  14. C

    What is the minimum amount that the spring must be compressed

    Homework Statement A 0.25 kg projectile is launched across a frictionless surface by a spring of spring constant k=1200 N/m. The block is then redirected up a 25 degree incline and sent through the air with the intent of clearing a 1.2 m high wall that is 4.0 m away from the end of the...
  15. R

    Find time to evacuate compressed air tank (conceptual verification)

    Homework Statement This is a first-order differential equation problem involving a changing fluid density and changing tank pressure. Tank contents: Nitrogen Tank pressure: 390 psig Temperature of compressed nitrogen: 0 CAtmospheric volume = infinity Atmospheric pressure = 14.7 psi...
  16. S

    Power generation using buoyancy, gravity and compressed air

    Hi all, this is my first post. I was wondering if it would be possible to use a deflatable/inflatable bladder inside a housing with an air valve at the top and bottom of said bladder secured through the housing. The housing material would be heavy, placticised metal or stainless steel. This...
  17. E

    Compressed Sensing: Matching Pursuit

    Hi, I need a geometric explanation for this algorithm: Suppose we have the system Ax=b, where A is and M-by-N matrix, x is N-dimensional s(<<N)-sparse vector, and b is M-dimensional vector. There is an algorithm called Matching Pursuit to solve the above system efficiently: 1- Find the...
  18. B

    In a physics lab experiment, a compressed spring launches

    Homework Statement In a physics lab experiment, a compressed spring launches a 40g metal ball at a 25 degree angle. Compressing the spring 17cm causes the ball to hit the floor 1.6m below the point at which it leaves the spring after traveling 5.3m horizontally. What is the spring constant...
  19. C

    Using compressed air to displace water

    Not really sure how to word the title better! Anyway, I'm looking at how I could design and do some basic flow calculations regarding compressed air. The idea is to have a tank of highly compressed air piped to a tank of water. When the valve between them is opened, the compressed air rushes...
  20. B

    A compressed spring has more mass

    My textbook says that a compressed spring has more mass than when it is not compressed. I'm assuming that this is because of E = mc2. A compressed spring has more energy and hence more mass. still, i have a real tough time wrapping my head around that. the spring has the same number of...
  21. F

    Compressed Air - Bernoulli Equation

    I'm trying to ascertain the dynamics of a compressed air system in terms of flow rate, air consumption, pressure drop etc. To keep it simple my system consists of a 5.5 bar supply (550000Pa) supply on 12mm OD Nylon Tubing and is reduced to 6mm OD Nylon through a valve (pressure drop assumed...
  22. S

    A spring is compressed by 90 cm

    Homework Statement A spring is compressed by 90 cm at the bottom of a frictionless hill of height 18m. the spring is realeased and propels a 2 kg block over the hill. At the top of the hill, the block's speed is 6 m/s. Find the force constant (spring constant) of the spring. Homework...
  23. S

    Rocket on a compressed spring

    Homework Statement A 10.1 kg weather rocket generates a thrust of 193.0 N. The rocket, pointing upward, is clamped to the top of a vertical spring. The bottom of the spring, whose spring constant is 415.0 N/m, is anchored to the ground. (a) Initially, before the engine is ignited, the rocket...
  24. S

    Compressed spring, doubling speed of impact

    Homework Statement A 0.211 kg shoe is dropped onto a vertically oriented spring with a spring constant of 102 N/m. The shoe becomes attached to the spring upon contact, and the spring is compressed 0.117 m before coming momentarily to rest. If the speed of the shoe just before impact is...
  25. C

    Spring Constant when compressed

    Homework Statement A 6kg block is released from the top of a 1.0m ramp (frictionless) and slides into a horizontal spring, compressing it 45 cm. Determine the spring constant. Homework Equations PEg = mgh (6*9.8*1) = 58.8 PEs = 1/2kx^2 (1/2*k*.45^2) The Attempt at a...
  26. F

    Compressed Air System Dynamics: Calculating Pressure Drop & Cv

    I want to work out the dynamics of a compressed air system consisting of a filter/regulator unit some spool valves and a rotary actuator with all the associated fittings. Essentially I have a 2" nominal bore compressed air line at roughly 7.5 bar, I have a system which feeds off this air main...
  27. B

    Help with a project - Air speed, compressed?

    1.If you have a wind tunnel, a tubing that goes from a large opening, to a smaller opening, with the larger opening facing the wind, will the wind speed be more out the smaller end since its being compressed? 2.Is there a way to calculate/guesstimate the difference in wind speed by the...
  28. J

    Calculate water pressure in tube end when tube is compressed

    Hello! Background I have a hobby in creating an automated home, controlling lights, reading temperatures, and so on from self build sensors and actuators. For a while I have had force sensing resistors under each leg of my bed so I can messaure my own weight every day, sleeping patterns and...
  29. E

    Total elastic potential energy of a compressed spring?

    Homework Statement A spring with a spring constant of 4 Newtons per meter is compressed by a force of 1.2 Newtons. What is the total elastic potential energy stored in this compressed spring? k = 4 N/m F = 1.2 N PE = ? Homework Equations PE = (1/2)(k)(x)^2 The Attempt at a Solution...
  30. C

    Does Nozzle Orientation Affect Speed in Compressed Air Powered Boats?

    I saw on myth busters where they took compressed air tanks an attached them to a boat and then opened the valve and then the boat started to move. They did 2 trials, one where the exhaust nozzle was pointed above the water and one where it was pointed in the water. Then one that was pointed...
  31. C

    Confused about Compressed Water in Constant Pressure Process?

    Homework Statement In a constant pressure process ant 1 bar determine how much heat must be added to raise the temperature of 2kg of compressed water at a temp of 50C so that it become superheated steam at a temp of 200C? u2=2659KJ/Kg Homework Equations W=-P(V2-V1) Q+W=U2-U1 The...
  32. I

    Under Pressure Finding the height of compressed air

    Homework Statement A 1.0--tall cylinder contains air at a pressure of 1 . A very thin, frictionless piston of negligible mass is placed at the top of the cylinder, to prevent any air from escaping, then mercury is slowly poured into the cylinder until no more can be added without the cylinder...
  33. A

    Young's Modulus: 2 bars placed end to end and compressed from both ends

    Homework Statement Two bars, one composed of aluminum and one of steel are place end to end as shown in Figure P11.60. The bars are both initially of length L = 24 cm, and both have a square cross section with h = 3.9 cm. If a compressive force of F = 8440 N is applied to each end, find the...
  34. A

    How much energy can be extracte from compressed water?

    Say I have 1 ton of compressed water at 40 mega pascals, IE its volume is only 982 liters. At standard temperature and pressure, how much kinetic energy will flow out of this system if a valve is opened?
  35. B

    In replacing a compressed air motor with a nozzle where does the energy go?

    Assume a compressed air motor, whose input power 1 cubic metre/minute at 200 psi. The motor exhaust is say, 20 psi at the appropriate volume say 10 - 11 cubic metre/minute. The motor produces 1KW due to its inefficiencies. Suppose the motor is replaced with a nozzle whose flow rate is the...
  36. M

    Sample of gas is compressed at a constant temperature

    Problem: When a sample of gas is compressed at a constant temperature, the product of the pressure and the volume remains constant: PV = C Q: A sample of gas is in a container at low pressure and its steadily compressed at constant temperature for 10 minutes. Is the volume decreasing more...
  37. F

    Solving PV/nRT for T: Temp Needed to Reduce Gas Volume to 2.50L

    A sample of sulfur hexafluoride gas occupies a volume of 5.10 L at 198 C. Assuming that the pressure remains constant, what temperature (in C) is needed to reduce the volume to 2.50 L? I used PV/nRT = PV/nRT and got -42 C. Do I have to convert to Kevlin first and then back to Celsius?
  38. D

    Work: an object falls onto a spring. Find max. dist. the spring is compressed.

    Until I learn to walk my name might pop up a lot in this thread... A block of mass m = 2.4 kg is dropped from height h = 59 cm onto a spring of spring constant k = 1240 N/m. Find the maximum distance the spring is compressed. Answer: 0.170m The first thing I did was convert the height from...
  39. J

    How far will the spring be compressed before the masses come to rest?

    A block of mass 5kg slides without friction at a speed of 8m/s on a horizontal table surface until it strikes and sticks to a mass of 4kg attached to a horzontal spring. The spring has a constant of k= 2000 n/m. The spring is in turn attached to a wall. How far will the spring be compressed...
  40. S

    Masses placed on platforms, with compressed spring under them.

    Homework Statement Two balls of masses m1& m2 are placed on different platforms, which are subjected to springs of same force constant and same compression. (springs are under platforms, basically like launch pads to fire the balls into the air). When the platform of first ball is...
  41. chaszz

    What exactly is compressed at very fast speeds?

    If a spaceship has enough power sometime in the future to achieve an appreciable fraction of the speed of light, what exactly will be compressed along the direction of its travel, relative to our slower frame of reference? Are the atoms (or the particles making up the atoms) which make up the...
  42. F

    Volume of compressed air question.

    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...
  43. L

    Speed or Compressed Time/Space

    I admit upfront, I'm a little insane, but since I love this subject, I hope those in the know can help educate me when they feel the urge. Anyway, I was wondering about a question. When an object is traveling through space, say a comet, does it speed up at it approaches the sun, or does time...
  44. T

    Compressed Air Engine for a cycle

    A friend and I are working on this idea which is fairly common, but I'm having trouble starting out. The idea is that of a compressed air engine. Where we take a normal, small capacity engine and modify it such that only compressed air, stored in tanks is sufficient to move the piston. Now...
  45. MattRob

    Speed of Sound in Compressed C02 Tank

    Hey, I've built a Cold Gas Rocket using a Co2 tank that stores liquid C02 at room temperature around 850 psi. (A Cold Gas Rocket is a rocket that uses a pressurized tank to propel the reaction mass instead of combustion, essentially just open a scuba tank and that's a very dangerous (not the...
  46. M

    Using Shipping containers as compressed air 'Batteries

    Using Shipping containers as compressed air 'Batteries" Just joined the site, you have a much more practical captcha system, I am surprised its not more widely implemented. Anyway! Obviously if you have seen a peak energy demand graph you will notice that the peak energy requirement is from...
  47. M

    Compressed spring on the ceiling.

    Homework Statement A box of mass M = 1.0 kg is attached to the ceiling by a spring with spring constant k = 112.0 N/m. The spring has a relaxed length L = 28.0 cm. Initially the spring is compressed to a length L/2. If the box is released, at what distance below the ceiling will the box first...
  48. E

    Solve (a-d): Spring Compressed on Dish Mass M, m + Answers

    Spring compressed :) 1. A block of mass M resting on a dish of mass m, subject to a spring vertical with constant k and natural length l_0. By placing the dish with the mass M, the spring is compressed taking, in equilibrium, a large l' Now compress the spring a little, for that inicially is...
  49. D

    Spring compressed, find velocity.

    Homework Statement A block of mass 0.3 kg and spring constant 24 N/m is on a frictionless surface. If the block is set into motion when compressed 3.5 cm, what is the maximum velocity of the block? How much is the spring compressed when the block has a velocity of 0.19 m/s? Homework...
  50. M

    Spring compressed by two boxes

    Homework Statement there is a problem in my final that I can't actually remember the values of the variables but I got 1 out of 4 grade in it and I was wondering what's wrong with my solution I am just going to write the variables because I don't know the numbers: a spring compressed equal...
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