Air flow Definition and 153 Threads

Airflow, or air flow, is the movement of air. The primary cause of airflow is the existence of air. Air behaves in a fluid manner, meaning particles naturally flow from areas of higher pressure to those where the pressure is lower. Atmospheric air pressure is directly related to altitude, temperature, and composition.In engineering, Airflow or air flow is a measurement of the amount of air per unit of time that flows through a particular device.
The flow of air can be induced through mechanical means (such as by operating an electric or manual fan) or can take place passively, as a function of pressure differentials present in the environment.

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  1. M

    Heat Transfer Coefficient -Air Flow onto perpendicular plane

    Hi All, I have a situation were I need to evaluate the heat transfer coefficient of a horizontal surface. The surface has tubes within although I first used "flow across a bank of tubes", this has been untrue due to the air flow coming from above the surface flowing vertically (and...
  2. T

    How do I determine air flow in a duct?

    Picture a Ø160mm duct 10m in length, open at each end. Then I install an in-line fan at one end so that it blows into the duct and just let it run at full power. How can I determine what the air flow will be? I startet thinking about it and was just surprised that I didn't know how to approach...
  3. M

    How to calculate Air flow rate....?

    Sir, Kindly let me know how to calculate flow rate (cfm or Litre/m) of air flowing through a pipe of 12 mm dia from a reservoir at pressure 7 kg/cm2 to atmosphere. i.e ;- how much volume of compressed air could pass within a minute through a "X"mm dia pipe from a constant pressure (7 kg/cm2)...
  4. William89

    Maximizing Efficiency in Passive Cooling: A Thermoelectric Solution

    Hello everybody, I have a computer case project and I need to create a fanless (passive) cooling. I feel excited of the idea to use paltier thermoelectric coolers, but their efficiency is considered very low, because the hot side is usually exhausted via passive radiators. So I came up with...
  5. M

    Air flow through small rectangular opening

    Hello, I have to calculate the air flow through a small rectangular opening with following data: - temperature at one side: 1200°C - temperature at other side: 20°C - pressure at hotter side is 3 mm WC lower than the colder side - the length of the opening is 240 mm - the width of the opening is...
  6. Daren Zomerman

    Airflow on/around quadcopter drone

    Hello, I'm a journalist interested in using an air-quality sensor on a drone, and I'm wondering how the airflow will affect the readings. This would be assuming that I will use a DJ Phantom 2 quadcopter with a GoPro underneath, the drone specs can be found at this link. For the project, we...
  7. R

    How Can Physics Improve Race Car Efficiency and Fuel Consumption?

    Ï had not the slightest idea there was even a cool place to learn about science and physics and...truth! I'd usually just "Google"it and read Wikipedia. One of the main things I would like to learn about would be air pressure or flow, air density and maybe some rotational mass. So let's say in...
  8. P

    Air flow from large to small tube.What happens to pressure?

    I would like to know what happens to air pressure when it flows from large tube to small tube. I would like to know the basic science behind this though I am pursuing my B.E. Moreover, does PV=mRT law apply here or some other principle applies here. What happens to temperature and other...
  9. Devang Marvania

    Mixing of two air flow at different pressure

    Hi Friends! Here is my query : I have two source of air supply with different pressures, temperatures and with different mass flow rates. Input 1: P1,T1,m1. Input 2:P2,T2,m2. Output: P3,T3,m3. P,T and m refers to pressure, temperature and mass flow rate respectively. If the mixing is being done...
  10. P

    Air flow measurement with multiple fans

    Hi, My company builds machinery with multi-zone hot air dryers. Each dryer has 2-3 supply blowers that push air through an electric heater and then through a duct into a plenum (one plenum for each dryer zone) at the top of the dryer. Each plenum is fitted with multiple air nozzles that...
  11. M

    Calculating Air Pipe Flow System Rates & Velocities

    I'm working in an engineering internship after my first year and we haven't covered fluid dynamics in my program yet. I've been assigned to find flow rates and velocities in several branches of a suction (dust collection) system in our factory. The main branch has a diameter of 30" and is...
  12. Artlav

    How to convert air flow into pressure?

    Let's say i have an air pump which produce plenty of air flow, but almost no pressure. Is there a simple way to turn this high flow, low pressure into high pressure, low flow? I'm thinking something akin to a gearbox turning fast spin, low torque of a motor into a high torque, slow spin output...
  13. P

    How can I calculate the flow rate created by a fan connected to an engine?

    Hello I am trying to design a vacuum using venturi. I cannot quite get the air flow created by the rotation of the fan, which is connected to the engine. How is the relation between the fan speed and the flow rate created by it? I know the proportionalities between the speed, power and the...
  14. U

    Improve Air Flow with Centrifugal Fan Design

    I am currently trying to use a centrifugal fan to force air through a small tube however i am looking for some information on how to better the design and performance as what i have currently is severely lack-lustre. This is just a prototype for controlling rate of airflow and all i had on...
  15. Nabil

    101 in air flow dynamics please?

    Hi everyone, I've got a newbie question which is probably more complex than I imagine so please bare with me. As a small DIY project I've trying to build a small exhaust filter system (A) for another device that produces undesirable fumes (B). I'm trying to work out if an axial fan (generates...
  16. danielng245

    Please help calculate flowrate frm blower to push water down

    How to calculate how much flowrate from blower i can push water pool 2,75m*1,8m down by 1,25m in 1 sec? Note : Blower Pressure 0.03 bar - 0.035 bar There is an empty room above the water pool with dimension of 2.75m*1.8m*1.7m This process happen in a closed chamber...
  17. Suresh Gadekar

    Air Flow Rate in 1/4" Pipe at 1 Bar Pressure

    is it possible to have a flow rate of 10lit/sec in a 1/4" diameter pipe at 1 bar pressure ?
  18. P

    How to reduce RH of air from evaporative cooler?

    Hi guys! I'm new here and this is my first post! I'm a fresh engineering graduate and I'm facing a dilemma. I'm currently in charge of a project. We intend to use an evaporative air cooler for a carbonated soft drink filling line. The flow of air intake is as follows: evaporative cooler -->...
  19. M

    Air flow over a circular cylinder

    Hi, Could you explain the reason why the velocity varies in the wake region behind the cylinder in "flow over a circular cylinder"? the velocity variation is, minimum at a point parallel to the centre point of the cylinder and increases to free stream velocity as the vertical distance increases...
  20. N

    Caculate air flow using tank pressure

    Dear all ! I am an engineer from Vietnam! I just started to work 4 months ago. Now I got assignments with compressed air system! The compressor is not mentioned here! We have an air vessel of 500 Liters, and pressure is 7 bar. Before air vessel is an air booster with inlet pressure of 6 bar. The...
  21. R

    Performance Test Air Flow Restriction At Work Shed Louvers

    At work we have a shed in full sun. Windows were cut in it to allow airflow. Louvers were installed to keep the rain out. However the sheet metal guys did a HUGE overkill on designing the louvers. I want to propose to my boss to remove half of the louvers so that we can get decent air flow...
  22. K

    Approximating Windshield Shape of a Car: Velocity at Points A & B

    Homework Statement [/B] The shape of a car windshield is approximated in the figure below; its length is 2.0 ft and height is 1.5 ft. Obtain an equation of the windshield shape r as a function of θ, r(θ), in the polar coordinate system shown in the picture. When the car moves at 55 mph...
  23. C

    Help to make the air flow uniform

    I am designing an almond dehydrator as a part of my university project and need some advice regarding air flow in the dehydrator. There is a hollow perforated cylinder with a heating device in the middle. This cylinder is divided into two sections. The lower section has to take in cool air...
  24. gfd43tg

    Why does the outlet pressure in a hair dryer remain constant?

    Homework Statement A hair dryer is basically a duct in which a few layers of electric resistors are placed. A small fan pulls the air in and forces it to flow over the resistors where it is heated. Air enters a 900-W hair dryer at 100 kPa and 25° C, and leaves at 50° C. The cross-sectional area...
  25. B

    How would air flow be effected in these scenarios with a fan

    I created a diagram of 5 scenarios in which I would like to understand how their variations would affect air flow and suction. Examples attached to post or link to examples: http://s29.postimg.org/kua3svg2f/understanding_airflow.png So onto the actual question, how will air flow and suction...
  26. 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...
  27. N

    Thermofluids: Air Flow Measurement (Pitot & Venturi)

    Homework Statement I did an experiment to measure air flow using a pitot static tube and a venturi meter. First attempt: I connected both long and short manometers to the pitot static tube. Then I switch on the fan. The difference in manometer reading is 0.59kPa, which is the pressure. Then I...
  28. K

    Pressure differential and air flow

    I'm having a hard time understanding air flow caused by pressure differentials. Given the following contextual image, crafted by myself: Bare with me here, these are two interconnected boxes open to the Earth's atmosphere. The orange arrow represents an air pump, such as a vacuum...
  29. K

    How does an air flow bench work

    Hello, I'm new to these forums and they seemed like an excellent way to have my questions answered. I'll start by saying that I've never had any course that dealt with fluid mechanics (mechanical engineering freshman), so I'm having quite some trouble grasping how readings on an air flow...
  30. K

    Understanding how an air flow bench works

    Hello, I'm new to these forums and they seemed like an excellent way to have my questions answered. I'll start by saying that I've never had any course that dealt with fluid mechanics (mechanical engineering freshman), so I'm having quite some trouble grasping how readings on an air flow...
  31. I

    Mass air flow through a nozzle at different upstream pressures

    I'm interested in identifying mass airflow through a choked convergent or conical nozzle. I've found some web info claiming that mass airflow through a nozzle becomes primarily a linear function of the inlet pressure, and doubling the inlet pressure doubles the flowrate. Further research...
  32. R

    Air Flow through cooling tower- fluid mechanics problem

    Hey everyone! I am working on improving natural draft counter flow cooling tower efficiency as my final year B.E. project. I came across a research paper that said that at transverse cross section of the tower, above drift eliminators, the air velocity decreases from the periphery to the...
  33. A

    Help with measure air flow rate with pressure difference in a cylinder

    Hi, I've got a horizontally moving piston in a pneumatic cylinder, the piston is moving backward to suck the air into the cylinder from a hole at one end, this will lead to an air flow rate. I would like to measure the air flow rate at that instant. I was thinking of with a pressure sensor...
  34. M

    Amperage draw versus Air flow VFD Fan

    I have a VFD fan that pushes air through a filter. Over time, downstream resistance gets higher due to the filter. Fan speed remains constant. We have looked at amperage draw and it has remained stable even with this added resistance. Does that mean that air flow remains constant? Kind of...
  35. S

    Heat Transfer Coefficient to Air Flow Rate

    Hey all, I'm trying to simulate a simple chip-heatsink situation in SolidWorks using their thermal modeling suite. I have found an ideal set of parametric values for the chip to work at a reasonable temperature, but I need to figure out what the convection coefficient means in terms of air flow...
  36. S

    Sound Power Reduction When Halving Air Flow Velocity and Doubling Grill Area

    If the velocity of air flow through a grill is halved but the area of the grill is doubled, By what factor will the sound power be reduced? air flow through a grill represents a dipole sound source, so it depends on the 6th power of velocity, but how does it depend on the area? If I take sound...
  37. B

    Continuity equation and air flow

    Although continuity equation is often part of fluid mechanics, does it have an application in air flow? For example, let's assume we have a frictionless air duct where air is introduced at a constant velocity and temperature. If the air duct varies in dimensions will the flow rate at the end...
  38. D

    Air flow pipe size reduction|Incompressible&Lossless COMPLETED ANSWER

    Homework Statement Q4. A horizontal air duct reduces from 0.75 m2 to 0.20 m2 . a) Assuming no losses and an incompressible fluid, what pressure change will occur when 6 kg/s of air flows through the duct? Use a density of 3.2 kg/m3 for these conditions. b) Is the incompressible...
  39. D

    Why air flow created by ceiling fan goes downward?

    Why air flow created by ceiling fan (which rotates counter clockwise (seen from beneath ceilling) ) goes downward?
  40. A

    Laminar air flow in a 2D channel - how to ensure that a flow is fully developed?

    Hello everyone, I am studying laminar airflow in a channel (2D) and trying to simulate it with FLUENT software but I need to know about the entrance length, and I want to know how I can be sure that a flow is fully developed? is it just by looking at the velocity profile? or looking at the...
  41. 0

    Why does the air flow faster over the top of the aerofoil than underneath?

    Because it is curved? -------------> why because it is curved will it flow faster over it?! What other reasons!? pressure is lower ontop, therefore faster?? why is the pressure on top lower... is it because of the shape of the aerofoil? I just find it hard to put this into a sentence...
  42. C

    Calculating Air Flow in 8mm Pipe at 15psi

    Hi, i need to calculate air flow true a pipe of 8mm in diameter @ 15 psi pressure, any help? I have a main pipe of 50mm with 7 outlets of 8mm every 300mm and i need to find the air flow to buy the correct blower.
  43. R

    Air flow rate thru mesh/net/screen

    I am looking for theoretical and/or empirical information about the extent in which a mesh/screen/net made of some kind of wires is slowing down airflow thru it, comparing to air flowing around it. At this point I am interested in meshes starting at a scale of insects screens (about 1mm) and...
  44. A

    Air Flow in a 10m. pipe - generating electricity ?

    I have this idea about creating a 10 meter plastic/metal pipe that would go from a house roof to the ground and having a "U' shape close to the ground so that both holes are directed at the sky. Does anyone have a clue if the difference in atmospheirc pressure between both holes (10 meters...
  45. G

    How Far Should Flow Straighteners Be Placed from Fan Outlets in HVAC Systems?

    Any HVAC experts in the house? Does anyone know of any engineering standards concerning the placement of flow straighteners downstream of a fan in a duct? I'd hate to just choose an arbitrary distance without any justification other than "well, it just seemed like it was good enough." So...
  46. E

    Rate of air flow between containers of different pressures

    Homework Statement I am given a container of volume V of pressure p filled with hydrogen gas. Outside the container, the volume can be taken as infinity and pressure can be taken as 0 (eg: in space). The temperature T is fixed throughout (there is a heat generator in the container that will...
  47. X

    How can we accurately compare air flow data in an open system?

    Hi, I have a question relating to normalizing air flow data in an open system… The system comprises of a regulator feeding 2barg line pressure to a valve (controlling the downstream flow), a variable restriction, a second valve (normally open) and a flow meter. Pressure readings are taken...
  48. V

    Air flow requirement of electrical enclosure

    I am putting one inverter in enclosure made out of CRCA sheet of 2mm thick. Enclosure has fins at the bottom side and at top hood. Inverter heat loss as per datasheet is 3000W. Can somebody help to calculate CFM requirement of fan for given allowed temperature-rise and heat transfer by...
  49. L

    Simple Bernoulli's exercise to find air flow rate

    I'm having problems with what seems like a simple Bernoulli exercise where I can plug in all known variables but not get an answer (using Excel). If I reduce my system down, it would be exactly like a venturi/pipe flow problem except that flow is in the direction of small pipe to large pipe...
  50. M

    Air flow in inlet manifold affecting engine performance

    i want to model air flow in the inlet manifold using CFD ,how do i predict how flow variations and other parameters affect engine performance ? i know how it affects but how do i show it virtually
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