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. S

    Compressed air help (adiabatic processes)

    Homework Statement i'm trying to work out how much energy can be extracted from a compressed air system using an adiabatic process. given how small scale the system is(an most likely unrealistic), the values for the energy that can be extracted seem very high from my calculations. Homework...
  2. B

    Calculating Air Velocity in a Duct with a Consistent Cross-Sectional Area

    Suppose I have a straight, frictionless duct, with consistent cross-sectional area, and air is flowing straight through and exiting into a free stream. A fan at the beginning of the duct draws stagnant air at atmospheric pressure, and then the air exits the end of the duct into another room also...
  3. R

    Calculating Compressed air leaks within a system

    Hi all, new to the forum, but I was wondering if anyone could help me as I'm going round in circles. After completeing an air leak survey and noting the hole diameter, dB reading of the leak and knowing the pressure of the system (bar) how can I calculate the leak rate CFM and the Energy wasted...
  4. A

    Compressed air cylinder temperature during rapid depressurisation

    Hi guys, Here's an interesting problem for you. I'm trying to understand what happens to the temperature of air cylinders as the compressed air within is rapidly expanded to see if the surface in contact with the expanding air gets so cold it passes through the ductile to brittle transition...
  5. H

    Vertical distance of mass shot from a compressed spring.

    Homework Statement A 0.110 kg dart is fired straight up. Find the vertical distance the dart travels from its position when the spring is compressed to its highest position. This is the second part of a question. The first part was to calculate the maximum compression... I calculated 0.1558...
  6. O

    How much must the spring be compressed? helppp

    how much must the spring be compressed?!? helppp A package of mass 9 kg sits at the equator of an airless asteroid of mass 3.0x10^20 kg and radius 2.1x 10^5 m. We want to launch the package in such a way that it will never come back, and when it is very far from the asteroid it will be...
  7. C

    Find launch speed given spring constant and compressed distance

    Homework Statement A potato gun contains a spring which is compressed a distance of 7.30cm (0.073m) when it is loaded. If the spring's constant is 41N/m, what is the launch speed of a .00321kg piece of potato when the gun is fired? Give the answer in m/s. Homework Equations Power = W/T...
  8. G

    Why air is compressed in Gas turbine engine ?

    i understood brayton cycle etc.. but why is air compressed in the GT engine ? iS is anything related related to following reasons ? 1. FOr better combustion of fuel, if so why ? 2 IS it to increase the temperature of air, if so why ? 3 any other reason
  9. B

    Buoyancy in Compressed Air: Can Objects Float or Will They Fall Due to Gravity?

    If air would be compressed to have equal pressure to that of water would objects which are buoyant in water be buoyant in such compressed air too or would they still fall down due to Earth gravity? Or asking differently, what would have to be the pressure of air (lower, equal or higher than...
  10. J

    Finding the pressure and temperature of a compressed monatomic gas

    Homework Statement A monatomic ideal gas initially has a volume of 3 m^3, a temperature of 300 K and is at a pressure of 1x 10^5 Pa. It is compressed adiabatically and quasi-statically to a volume of 2 m^3. Calculate its final pressure and temperature. Homework Equations Po(Vo...
  11. 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...
  12. 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)...
  13. 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
  14. K

    Spring Compressed and released

    Homework Statement A spring with a spring constant 3.2N/cm is compressed 33cm and released. The 3kg mass skids down the frictionless incline of height 24cm and inclined at a 23 degree angle. The acceleration of gravity is 9.8m/s^2. The path is frictionless except for a distance of .8m along...
  15. 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 =...
  16. D

    How can I implement BCRS 2x2 format for sparse matrices in C++?

    Hello All, I am trying to learn matrix compression algorithms for sparse matrices. I understand the Compressed Row Storage (CRS) format but I am having difficulty with the Block Compressed Row Storage (BCRS) format - where the size of the sub-block(s) are 2x2. Can anyone please point me to...
  17. A

    Finding the Minimum Mass for Plunger-Spring Contact

    Homework Statement A plunger of mass m rests on a spring with constant k. The spring is pressed down a distance x and released from rest. How large does the the mass need to be in order to keep the plunger in contact with the spring? Homework Equations PEf+KEf=PEi kx-mg+N=0 The...
  18. B

    Compressed Hydrogen tank mass estimation

    Does anyone know how to calculate the mass of compressed hydrogen tank at certain pressure. The tank is cylindrical with hemispherical ends. I have pressure,radius,wall thickness and length,internal volume and density of the material. The tank is a Type IV tank.(Composite tank with...
  19. 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...
  20. R

    A block dropped on a spring, distance compressed unknown.

    [b]1. A block of mass m = 1.6 kg is dropped from height h = 61 cm (height above the spring, not total height) onto a spring of spring constant k = 1820 N/m (Fig. 8-38). Find the maximum distance the spring is compressed. Homework Equations K=-U, since all energy is conserved, work would...
  21. S

    Mass on incline sliding into spring, how compressed?

    Homework Statement A 14 kg box slides 4.0 {\rm m} down the frictionless ramp shown in the figure , then collides with a spring whose spring constant is 210 N/m. a)What is the maximum compression of the spring? b)At what compression of the spring does the box have its maximum...
  22. G

    Why do clocks tick slower and faster in different depths of gravity?

    Something just occurred to me today. I've puzzled for some time why it is that normal clocks tick slower when in a deeper depth of gravity but that pendulum clocks do the opposite and actually tick faster when in a deeper depth of gravity. Can time tick slower and faster? I believe I now...
  23. T

    What is the Enthalpy of Water at 45 Degrees and 1.2 Bar Pressure?

    Homework Statement Finding the enthalpy of water with the following known data: Water, temperature 45 degrees, pressure 1.2 bar Homework Equations Q' = m'(steam) * h(gas) - m'(steam) - h(fluid) The Attempt at a Solution I need to find the enthalpy of water under the circumstances...
  24. I

    Compressed non-bonded magnet - possible?

    Compressed "non-bonded" magnet - possible? Dear everyone As opposed to a bonded magnet being magnet powder "glued" together with e.g. epoxy and which is incapsulated as to prevent corrosion - does anyone know if one can instead compress magnet powder without a binder directly in a can-like...
  25. 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...
  26. G

    Self-torque of a compressed rod?

    Two charges, q1=q2=q>0, are held apart by a dielectric rod of length L. Everything is at rest in the xy-plane of IRF K, with x1=y1=0 and x2=L cos(theta), y2=L sin(theta), 0<theta<pi/2. Viewed from frame K’, moving in the positive x-direction of K at speed v, the Lorentz forces on the two...
  27. H

    Calculating Friction Coefficient of a Compressed Spring

    A light horizontal spring has a spring constant of 108 N/m. A 3.05 kg block is pressed against one end of the spring, compressing the spring 0.111 m. After the block is released, the block moves 0.204 m to the right before coming to rest. The acceleration of gravity is 9.81 m/s2 . What is...
  28. 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...
  29. G

    Eccentricity of a compressed circular ring

    If an initially circular ring is made out of round by cutting out a section of the ring (delta g) and compressing the ring till the gap is approx zero is there an equation to describe the eccentricity of the circle? Cheers Gordon
  30. O

    Compressed spring with frictional forces problem

    Homework Statement A book (mass 2.50 kg) is forced against horizontal spring (negligible mass) with force constant 250 N/m, the spring is compressed 0.250m. When it's released the textbook slides horizontally across a surface with kinetic friction coeff = 0.30. How far does the book move from...
  31. S

    Calculate CM Speed of Rod on Compressed Spring

    Homework Statement A thin uniform rod has mass M = 0.31 kg and length L= 0.45 m. It has a pivot at one end and is at rest on a compressed spring as shown in (A). The rod is released from an angle θ1= 57o, and moves through its horizontal position at (B) and up to (C) where it stops with θ2 =...
  32. 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.
  33. 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...
  34. maverick_starstrider

    C/C++ Outputting to file in the most compressed form (c++)

    Hi, I'm just wondering, usually when I output to file in C++ I just do like: fout.open("output.txt",ios::out); fout.precision(13); fout << data1 << " " << data2 << " " << data3 << endl; or something to that effect. i.e. I use c++'s file streams. However, for my current application...
  35. 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?
  36. 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...
  37. 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...
  38. K

    Bathroom scale being compressed but jumping on it

    Homework Statement If you stand on a bathroom scale, the spring inside the scale compresses 0.55mm, and it tells you your weight is 760N. Now if you jump on the scale from a height of 1.3 m, what does the scale read at its peak?
  39. 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...
  40. B

    How Fast Does a Ball Move When Pushed by Compressed Air?

    final velocity of a ball pushed by compressed air..pls. help! Homework Statement Compressed air is used to fire a 1.72 kg ball vertically upward from a 1.50 m long tube. The air exerts a upward force of 28.7 N on the ball as long as it is in the tube. With what velocity does the ball leave...
  41. V

    A monatomic gas is adiabatically compressed

    http://img198.imageshack.us/img198/1122/masteringphysicsscreens.jpg p = ((1/3)*(N/V))*mv^2 vrms = squareroot ((3p)/(N/v)) i tried substituting .125 into the equation to get some numbers, didn't get anything useful can someone show me the formulas that i have to use, and how to use...
  42. 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)...
  43. F

    Compressed Gas Expansion: Energy Transfer and Work Done

    compressed temperature ? Homework Statement One mole of nitrogen is compressed (by piling lots of sand on the piston) to a volume of 14 liters at room temperature (293 K). The cylinder is placed on an electric heating element whose temperature is maintained at 293.001 K. A quasistatic...
  44. E

    Can water be compressed so much that it freezes?

    Intuitively, it makes sense to me that it would. But then again, weird stuff can happen under extreme circumstances... What would actually happen? Would the temperature of the substance actually increase or decrease under ENORMOUS pressure (i.e., that the molecules could barely move, if...
  45. R

    How far has the spring been compressed?

    A block of mass 9.0 kg slides from rest down a frictionless incline and is stopped by a strong spring with spring constant 3.50 x 10^4 The block slides 5.00 m from the point of release to the point where it comes to rest against the spring. When the block comes to rest, how far has the spring...
  46. J

    Distance a spring has been compressed

    Homework Statement . A 20 kg mass, released from rest, slides 12 meters down a frictionless plane inclined at an angle of 30º with the horizontal and strikes a spring of spring constant K = 200 Newtons/meter as shown in the diagram above. Assume that the spring is...
  47. Y

    Finding new Pressure in cylinder when compressed

    http://img15.imageshack.us/img15/9746/21478397.png I know how to setup the entire problem i just don't know how to calculate the new pressure after the piston is compressed.
  48. 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...
  49. 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...
  50. S

    Designing the Best Potato Launcher: Catapults, Compressed Gas, and Combustion

    hello, i was wondering what people here would think the best design type for a potato launcher would be. I looked at catapults, ones that use compressed gas, and combustion. firstly, which would be the easiest to make?
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