Fan Definition and 347 Threads

A fan is a powered machine used to create a flow of air. A fan consists of a rotating arrangement of vanes or blades, which act on the air. The rotating assembly of blades and hub is known as an impeller, rotor, or runner. Usually, it is contained within some form of housing, or case. This may direct the airflow, or increase safety by preventing objects from contacting the fan blades. Most fans are powered by electric motors, but other sources of power may be used, including hydraulic motors, handcranks, and internal combustion engines.
Mechanically, a fan can be any revolving vane, or vanes used for producing currents of air. Fans produce air flows with high volume and low pressure (although higher than ambient pressure), as opposed to compressors which produce high pressures at a comparatively low volume. A fan blade will often rotate when exposed to an air-fluid stream, and devices that take advantage of this, such as anemometers and wind turbines, often have designs similar to that of a fan.

Typical applications include climate control and personal thermal comfort (e.g., an electric table or floor fan), vehicle engine cooling systems (e.g., in front of a radiator), machinery cooling systems (e.g., inside computers and audio power amplifiers), ventilation, fume extraction, winnowing (e.g., separating chaff of cereal grains), removing dust (e.g. sucking as in a vacuum cleaner), drying (usually in combination with a heat source) and providing draft for a fire.
While fans are often used to cool people, they do not cool air (electric fans may warm it slightly due to the warming of their motors), but work by evaporative cooling of sweat and increased heat convection into the surrounding air, due to the airflow from the fans. Thus, fans may become ineffective at cooling the body if the surrounding air is near body temperature and contains high humidity. A fan blade is generally made of wood, plastic, or metal.
Fans have several applications in the industries. Some fans directly cool the machine and process, and may be indirectly used for cooling in the case of industrial heat exchangers.
These are critical machines and responsible for operating the entire plant, which may shut down without the proper fan. In mine and tunnel, it also used as safety equipment.

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  1. Nantes

    If the air temperature were the same as the human body's....

    Damn title character limits. I just had the weirdest thought while rearranging my computer's case fans. I put my hand in front of one of them and felt a light breeze of air, telling me it was working. This is due to the local cooling produced where the fan's airstream comes in contact with the...
  2. G

    Blocking Back Of Fan Creates Vacuum In Front?

    Hi there, I have recently observed a strange effect regarding a fan and was wondering if someone could explain what's going on. I have a 22cm computer case fan which I am using in a project. For my purposes, I had to partially tape over the back of the fan. I also put a large plastic jar lid...
  3. sophiecentaur

    Which is the best fan for my wood burning stove: Peltier or Stirling?

    I am having a wood burning stove installed soon. I am wondering which would be better, to put on the top and aid room circulation, an electric fan, powered from a Peltier junction or one using a Stirling Engine. Does anyone have any ideas or experience about this? I wouldn't expect 'efficiency'...
  4. K

    Electrical Designing Your Own CPU Cooler Fan: Fundamental Tips

    Hi folks.I'm 3rd grade mechanical engineering student.I want to make cpu cooler.I will make pid controlled fan with an arduino. PID path is easy but I could not find anything about fan dynamics. I want to design my own fan.I need something like "fundamentals of fans" that should answer my...
  5. Kyle Burris

    Mechanical noise - A/C and radon fan standing wave hum

    Hello, I am moving into a new house, remodeling, etc. & am installing a new A/C compressor and radon fan. Being that low frequency noise highly bothers me & affects my insomnia quite a bit, I am trying to look at all considerations regarding acoustics, mechanical sound propagation properties...
  6. R

    How Can I Lift and Move a 400-Pound Load Without Wheels?

    Hi I'm working on a project where I would need to lift about 400 pounds about 1 inch off the ground and keep the momentum in order to manually move it. I thought about using four fans with a skit on each corner facing downward to allow for upward movement, but I'm not sure how much power I would...
  7. 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...
  8. E

    How Is Pressure Generated by a Centrifugal Blower Calculated?

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  9. B

    Ducted Fan Pressure Differential: Questions Answered

    Hi guys, I recently completed a fluid dynamics practical at Uni and submitted a report on it, however, I still have some burning questions which I need to be answered. Firstly, the data that we collected shows that as the flow rate in the duct increases, the pressure differential of the fan...
  10. C

    Is overall bill reduced by using fan regulators

    actually i searched a lot regarding this question but didnt find exact answer anywhere.some say electricity bill reduces some vice versa.do all extra voltage is dissipated as heat? in the regulator,or current drawn remains same or only partially dissipated as heat.Thanks.
  11. K

    Which pump is suitable for a mist fan?

    Dear All, Would you please guide me regarding I want to make a mist fan. A low level mist is required almost 4 to 5 feet. I need all information regarding tube dia, nozzal specification specially pump specification. Thanks in advance. Regards, Kashif Usman
  12. grandpa2390

    Popping noise from speakers when I turn the fan off

    I just noticed this and it is crazy. I have a little speaker that I plug into my computer. it is being charged by the usb port. I got up and turned off the fan in my room and I heard a popping noise. It worried me a bit, so I turned the fan back on (no noise), then I turned it off and I heard...
  13. C

    Moment of Inertia of ceiling fan

    Homework Statement A ceiling fan consists of a small cylindrical disk with 5 thin rods coming from the center. The disk has mass md = 2.9 kg and radius R = 0.22 m. The rods each have mass mr = 1.4 kg and length L = 0.83 m. 1) What is the moment of inertia of each rod about the axis of rotation...
  14. M

    Anyone here understands how a [overhead fan works?]

    Ello, does anyone here understand how a standard overhead fan and air flow works? If so, what would happen if you're just chilling in your room with the door closed,windows shut and fan off, then the fan just speeds up to around90% thespeed of light for a second. Would that kill me, suck me...
  15. A

    Calculating Fan Size: Not Driven by Motor

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  16. Kyle Coulthard

    Does the fan I need for a sidepanel on my PC differ?

    Okay so I've had my PC for 5 years and my sidepanel intake fan is shot and I was wondering how to know what fan I need to replace it or if any standard intake fan would work?
  17. Z

    What gears to use to reduce fan speed from fast moving motor

    hey, I am building a fan, but I need the fan blade to move relatively slow, slow enough to see each panel on the blade. I am expecting to use a gear system with a belt. What gears should I use to active this?
  18. N

    On what does the cfm of fan depend?

    On what does the cfm of fan depend ? how to gain maximum cfm from a 1800 rpm fan ?
  19. D

    How to design a rpm and torque indicator from a fan?

    how to design a circuit to determine the rpm and torque from a fan?
  20. A

    How Does Fan Descender Mechanics Work for Construction Sites?

    I have been tasked to design a controlled descender to be used on a building site to lower tools/rubble to the ground. I'm trying to design a product like a fan descender like that seen at powerfan.co.uk Could anyone help me with the theory side of its operation. Obviously it uses the fans...
  21. M

    Optimum positioning of fan inside an enclosure

    Hello! I am an electronics engineer and the only time I came across Fluid mechanics was in class 12. I have been stuck for a long time in the finalization of a product. The difficulty is that I need to design a heat-sink, place a fan over it and perform a thermo-fluid simulation of the system...
  22. Z

    Speed of sound in turbulent air?

    If I turn on a standing fan in my room how does the speed of sound change in the fast moving air compared to the still air around it? Would it be relatively faster, slower, or does it depend on the direction in which the fan is blowing?
  23. T

    Fan Manufacturer: 145W to Move 1kg of Air 1m

    Homework Statement Hi, I am trying to work out the energy needed to move a certain quantity of (ideal) gas using a fan but am finding a great discrepancy between my calculations and those supplied by the fan manufacturers. let's say i'd like to move 1kg of air (1kg/m3) a distance of 1m. I get...
  24. L

    Can fan RPM affect power consumption in heat exchangers?

    Hi Guys, I just want to ask if there is a relation between fan RPM and the fan power consumption. Because in some specifications I see, Power consumption is not consistently increasing as you increase the Fan RPM. If we lower the RPM , will we still achieve the same airflow? if we always set at...
  25. quantumlover

    How does the Clair air purifier's e2f filter affect fan sizing?

    I recently shifted to South Korea to pursue higher studies and stay with my sister and niece . My niece is working on a high school project on air pollution and indoor air quality studies . Starting with a write up on air pollution and then indoor air quality and effects on health and the...
  26. A

    Why Do Ceiling Fans Start at the Highest Speed?

    My husband asked a question earlier this evening, which has given me pause. I've looked everywhere I can think of and came across this forum. Maybe someone here knows the answer. Why do ceiling fans (and similar residential/box style fans) go from the off position to the highest possible speed...
  27. P

    Understanding Airfoil Ceiling Fan Blade Velocity Diagrams

    Anyone can show me how the velocity diagram at the inlet and outlet of a airfoil section ceiling fan blade?
  28. P

    What is the optimum pitch angle for ceiling fan blade design?

    For the final year project that i am doing, I need to design a high efficiency ceiling fan blade with airfoil section, tapered and also twisting. Can anyone tell me how can i obtain the optimum pitch angle for different section of my ceiling fan blade?
  29. M

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    Hello, I was hoping someone on here could suggest some affordable software to model the flow produced by a ducted fan. I saw someone using Solidworks flow simulation, which is convenient because I can use SW to model the fan AND get a rough estimate of the thrust produced. I'm not looking for...
  30. Y

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  31. M

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    In particular I am wondering about compressor blades, but it's an interesting question to pose for household type fans as well. We can imagine "waterwheel" type schemes, and also the more traditional schemes where the axis of rotation is parallel to the flow. Which produces more noise per...
  32. T

    Parking garage jet fan - too much noise?

    I am to choose a certain type of jet fan in a parking garage. Looking at a spesific one, what I'm having a hard time considering is the noise it generates - 78 dB (A) at 3 m - and whether it would within acceptable limits? This is a fan that you would pass underneath walking to or from your car...
  33. K

    Trying to stall an axial fan (cooling fan)Would it work?

    Hi all, I was thinking of doing an experiment with axial fan for determining it's stall condition. By stall, here, I mean airfoil stall. I want to do this experiment in order to gain a firm grasp on the concept of stall. I have read the theory but an experiment would definitely give me an...
  34. P

    Moment of inertia about a ceiling fan?

    Homework Statement A ceiling fan consists of a small cylindrical disk with 5 thin rods coming from the center. The disk has mass md = 3.3 kg and radius R = 0.26 m. The rods each have mass mr = 1.2 kg and length L = 0.72 m. What is the moment of inertia of each rod about the axis of rotation...
  35. T

    Does Turning on a Fan Affect Room Temperature?

    Homework Statement A person living in a 4m x 5m x 5m room turns on a 100-W fan before he leaves a warm room at 100kPa, 30 degrees Celsius, hoping that when he returned in 5 hours, the room would be cooler. Disregarding any heat transfer determine the temperature of the room when he comes back...
  36. B

    How Fans Move Air: Propeller vs. Blade Shape

    If fan blades move in a circular way how is the air moving towards you (in front of fan) ? Also propeller and fan have different shapes, does it mean they work different?
  37. S

    Fan total pressure enough or not?

    Dear all I'm designing an exhaust system for a wood working facility. Please correct me if I'm wrong as I'm new to this industry: The system needs about 4.8 m^3/s airflow (with main duct velocity of 20m/s and branch velocity of 23 m/s). The total pressure drop due to the ducts and...
  38. 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...
  39. S

    How to determine torque required to spin a fan?

    So I want to design a propeller that will slow down a motor and I want to know what formulas or equations I would use to calculate that torque. Also, if I decided I wanted to run it in a fluid, what it just be a matter of density change? I have attached a picture of what I want to do. Thanks
  40. H

    Why does static pressure decrease as CFM increases on blower fan charts?

    Hi, Looking at blower fan charts, why does the static pressure drop with increased CFM, what makes sense to me should be a pressure difference rise with increasing CFM.
  41. B

    I need your help for my solar power greenhouse fan project

    Hello everyone, Firstly thank you for taking the time to read this! I am a complete electrics beginner, so forgive anything stupid I say. I'm also typing this on a phone, so sorry for the odd nonsensical word! So here is what I am trying to do: I have a small greenhouse, the plastic kind...
  42. Manraj singh

    Can a Rotating Fan Be Used to Power a House?

    Other people must have come up with this before, but what if we attach a lever to a rotating fan. The lever can be attached to a bulb to run it, or maybe something like a Leyden jar or a KERS, (mind me if its the wrong device, i am just a rookie) to store it. So won't the house be self sufficient?
  43. P

    Calculating Loads for Static Fan of 6,060kg: Help Needed

    The attachment provided shows a frame in which a large fan is to be rested on. The fan is to remain static and has a weight of 6,060 kg and the location of the centre of gravity is shown in the attachment. Each frame member has a cross-section of 200h x 90w. I would like to know HOW to calculate...
  44. G

    Calculating the effectiveness of a Radiator and Fan Combination

    Hello, I am trying to compare different combinations of Radiators and fans on their ability to cool water(or any liquid for that matter) Now I've been showen some Bernoulli's equation things and been pointed at Reynolds number but To be honest I haven't looked at any physics outside rigid...
  45. T

    Does a Fan On a Wood/Coal Stove Produce More Heat or Just Dispurse It?

    I posted this question in a wood/coal stove forum and after 100 responses, we do not have a convincing answer: Will MORE heat be extracted from a heated metal object if you put a fan on it? If we have a simple electric resistance heater (a glorified toaster) making 10,000 BTU's, it seems...
  46. M

    Sailboat on a Flat Lake: Fan On - What Happens?

    Here's a random question from the depths of my brain. :) Say that there's a sailboat on a flat, empty lake. Now imagine that on the boat, behind the sail there's a big electric fan. If the fan were to be switched on(blowing towards the sail), would the boat move forwards, backwards, or...
  47. 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...
  48. B

    Modding an LED Fan: Easy Steps to Control Colors

    I was wondering if anyone could help me with this. I have a 200mm LED fan that currently has blue LEDs in it. I would like to swap them out for tri-color LEDs and run a switch through the LED loop to control which LED would turn on. I want to mount the switch into a PCI slot in the back of...
  49. S

    What creates a partial vacuum when a fan is in motion?

    My understanding is that when a fan begins spinning, a partial vacuum is created. Physically, what creates this partial vacuum? Does the motion of the blades create a void in which there are fewer air molecules than in the ambient air and thus the pressure is lower than the ambient pressure?
  50. S

    Electricity consumption of a fan in a cooling tower

    Hi everybody! I'm currently working on a project where a wet cooling tower is involved. The wet cooling tower is an induced draft system. I know the volume of air handled and also the properties of the air entering and leaving the system. I want to determine the electricity consumption of...
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