Questions tagged [fan]

The fan is an electrical appliance using the principles of a motor.

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0answers
31 views

Why does this ducted fan have 10 blades (instead of some odd number of blades)? [closed]

I've searched online and learnt that odd number of blades reduce turbulence and noise. I counted my home's ceiling fan, it has 3 blades, then I counted my laptop's fan, 13 blades! Amazing! But later, ...
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7 views

How to calculate CFM of cooling fan using anemometer and duct?

I have quite a few 4010 (40x40x10mm) fans and would like to measure the air flow of each one. I have designed this 3D Printed duct that fits on a handheld anemometer, and the fan mounts on the other ...
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2answers
39 views

Could an electric centrifugal fan in space be used to propel a substance to create force?

Would an electric centrifugal-force fan (like that found in a blower motor) work in space to create force, by putting a substance (like silica sand or something slippery) through the centrifugal fan ...
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4answers
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Is this cheap “air conditioner” able to cool a room?

My parents bought this "air conditioner", but I am very skeptical that this can cool a room, or even cool anything. I doubt that it even has a cooling element, I suspect that it is just a fan + ...
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3answers
207 views

Conversion between Power and Flow rate of Fan taking into consideration the geometry of the fan

I need to find the relation between two properties of a fan, that is between power and flow-rate. I expect such a formula to depend on the pressure and on the geometry of the fan. I have found in ...
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53 views

calculate CFM of a ceiling fan

I'm trying to calculate, or even understand what data do i need to calculate the CFM of a ceiling fan. in many countries this is a given data in the product details but not where I'm from. I have the ...
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32 views

At what wind speed will a ceiling fan 10 feet above my desk move a sheet of paper? [closed]

We sell fans. An engineer asked this question. He wants to buy a fan large enough to cool without being so large it blows paperwork off his desk. Q: At what wind speed will a ceiling fan 10 feet ...
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28 views

Aligning fans in a tube

So, I have a lot of old PC fans and got thinking, what would the airflow look like if I lined them all up in a straight tube and powered them all? Would the speed of the airflow increase a steady ...
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2answers
163 views

Thermodynamics - best fan speed to heat a room (for the same heating power)

Let's assume we have a cold empty room (with no person in it, therefore - barely little air movement) and we want to heat it up. In the room, we have a hot-air blower that has two fan speed-settings, ...
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40 views

Air pressure drop off rate

I’ve been thinking about this for a while, and at first, I assumed that the inverse square law applied, but seeing as how air isn’t a form of radiation, I’m not sure that it still applies. So if we ...
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2answers
1k views

How to calculate the force of a fan

Let's say that we want to build a helicopter, if we want it to hover in the air then the pushing force of it's fan must equal the force of gravity but in the opposite direction, so how do we calculate ...
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1answer
134 views

Will a room heat quicker with a fan blowing on a hot surface? Why?

I got into an argument with someone who thinks that blowing air across a fireplace will make the room heat more slowly, but based upon the principles computer heat sinks use to get heat away the room ...
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1answer
84 views

Angle of Attack of a propeller blade

What will be the best angle of Attack for a propeller blade that is in the airfoil shape?
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1answer
74 views

Propeller blades flat vs wing shape

Does a propeller blade with the shape of a wing produce more lift than a flat blade and will a blade with a wing shape produce lift in a ducted fan situation?
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1answer
22 views

How is steam affected by a fan?

Scenario Consider a humidifier with a fan behind it. Assume same room, moderate temperature, low fan speed. ...
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2answers
37 views

why shadow of a glass oscillates under the rotating fan behind which there is a lightsource

So today I was sitting in mess, and light coming to me was fluctuating mainly because of rotating fan which was cutting the light source just right above it. But then i observed that the shadow of the ...
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38 views

Cool a room with a fan, what sens orientation? [duplicate]

It is really hot these days, and at night, I try to cool my room before going to sleep but I'm wondering in which sens I should orient my Fan Answer A : Push the hotter air with my fan outside. ...
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2answers
77 views

Room not getting cooled

I am in a room which is heated up duringg day, in night outside temp is quite low, but my room with a ceiling fan running still feels hot as it was in day if I step outside door its cold. There is ...
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51 views

How would the Stroboscopic Effect appear if the blades were reflective?

The Stroboscopic Effect is an optical illusion in which rotating spokes can appear to rotate differently than the true rotation. What will the observation be like if fan blades are coated ...
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3answers
2k views

Why do we feel cold when we switch on the fan? [duplicate]

We know that on increasing the kinetic energy of a gas its temperature increases: $$\text{Kinetic Energy} = \frac32 kT$$ where $k$ is the Boltzmann constant. This equation is derived from the kinetic ...
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1answer
32 views

How to have high agitation caused by high air flow while heating the same air?

It may not be possible but I am trying to create an environment that has decent air flow for agitation. I want that environment to receive heat though through convection so increasing temperature over ...
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2answers
169 views

Fan vs. Air-conditioning

At the office, we have the air-conditioning turned on like crazy, and we are therefore freezing... The air-conditioning is coming from the roof. My question is: Does putting a fan blowing in the ...
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2answers
109 views

Does a fan's orientation with respect to gravity affect its flow rate or static pressure?

I just recently got a blower/centrifugal fan to use for layer cooling on my 3D printer and I'm thinking about how I want to mount it. My primary question is exactly as the question title says: does a ...
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2answers
790 views

Why are ceiling fans so much quieter than others?

I used to live in a house that had ceiling fans, which were great for the summer and so wonderfully silent when running. Now however I've moved to a house that has no ceiling fans so I've bought a ...
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2answers
602 views

How does the air flow behave when one puts fans in front of/beside each other?

If I have a single 120mm PC case fan which pushes X cubic feet per minute, will stacking several together proportionally multiply the CFM, velocity, and/or the pressure? If I put them in parallel, i.e....
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1answer
70 views

Blue light enables you to see blades of fan on high

My son has a ceiling fan in his room and one Christmas, while he had blue snowflake lights strung up, we noticed that if we turned the fan on high with the blue lights on, we could see every blade. ...
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1answer
75 views

Is there any way to increase the speed of the blades (air coming out) of my fan? [duplicate]

Don't worry, my ceiling fan do not have any mechanical problem(if i will not mention it most of you will say repair your fan) it's just a part of home experiment. Once looking at the blades of my fan ...
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1answer
210 views

Why do we feel cool when we turn our fans on?

It is a question that came to me, but evaporation doesn't seem a nice answer. Please help.
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1answer
303 views

How does an induced draft fan work in a coal power plant?

I have been studying a coal-fired power plant, and the power plant cycle has an induced draft fan that is used to create negative pressure to help get the flue gas travel to the stack. I am confused ...
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1answer
869 views

Does adding mass to the fan blades affect its max velocity?

If I replaced fan blades with congruent blades, the only difference being the second set has a higher density, would that affect the speed cap on the spin? I know it would affect acceleration, but I ...
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2answers
3k views

How do ceiling fans cool or heat?

Why does a ceiling fan blowing air downward cool in the summertime: whereas a ceiling fan sucking air upwards heats in the wintertime: ? Why isn't it the other way around?
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5answers
8k views

Why does a ceiling fan start up slowly? [closed]

I think it probably has something to do with the capacitor inside but I don't get it why doesn't it just Start spinning instantly when we push the button why does it slowly start to spin and gradually ...
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0answers
34 views

Thrust to weight [closed]

Want to put a ducted fan or shrouded propeller motor on a snowboard. How much thrust would be needed to propel 275 on a snowboard? I'm aiming for a speed between 15-25 mph. The board would be 169 cm ...
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3answers
295 views

Air flow speed and penetration abilities

As I understand, two fans with the same diameter and with the same rotor speed(usually measured in RPM) can have different air pressure(usually measured in mmH2O) and air speed(usually measured in CFM)...
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Lining up fans in a row

Im new to this website, and not extremely educated in the world of physics. I have a very basic (mostly high school, some college) understanding of physics. That being said, I work for the fire ...
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1answer
1k views

How does a ceiling fan blades redirect air throughout a room to cool you off?

I already know how a table fan works because of how the blades are angled. For a ceiling fan I am confused about how the blades cut through air to cool off things in a room?
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4answers
11k views

Why does a moving fan seem transparent?

We all know when fan starts moving faster, we cannot see its blades. Why is this? First I assumed persistence of vision may be the reason. But that can happen with blade also right? Image of blade ...
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3answers
253 views

Will computer fan rotate slower if one makes impeller heavier?

Imagine that we replace plastic fan impeller with identical metal impeller (same form, heavier weight). Would maximum fan speed decrease? Common sense suggests that air resistance and bearing ...
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2answers
221 views

Why things wobble when submitted to wind?

If I place a little piece of paper in front of a fan, it is going to wobble/oscillate. Is it because the wind flow isn't constant ? Or because the air movement makes the piece of paper move away, so ...
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2answers
4k views

Determine fan sound (dB) based on its rotational speed (RPM)

I am trying to find the sound amplitude or level produced by a fan, knowing its RPM. Is there a simple formula for it? What other parameters does it depend on? Assume I have all the fan properties, ...
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1answer
744 views

Speed to power conversion

Here it is stated that there is a cubic relationship between fan speed and power consumption (Pfan ∝ FanSpeed^3). I have the fan speed (m/s), but I need to convert it into power (W). How can I compute ...
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58 views

What will happen to this fan in this situation?

Lets say I have a pipe with a fan at the end of it and it is drawing ambient air from the other end of the pipe. Once I account for some blockages and looking at the fan curve, it was found the ...
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1answer
68 views

What is the optimum elevation angle for my 3000W heater? [closed]

In an empty room shaped like a cube with verticies of length a and at 20C starting temperature (homogeneously distributed), what is the optimum elevation angle, X, of my 3000W heater fan if it is ...
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2answers
237 views

Hydrodynamics: Conservation of momentum violated by a fan in a cylinder?

Consider the following situation: there is a hollow cylinder with both caps removed. The cylinder is submerged into water. Inside the cylinder, we place a fan (or pump) that pumps the water through ...
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1answer
2k views

Why Do My Fan Blades Produce Color When They Spin?

I've posted a short video here as a visual aid. Whenever I put my fan on Medium speed during the night time, it produces a rotating Blue and Orange color design, despite both fan blades being a white ...
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3answers
22k views

What is going on in front of and behind a fan?

Why is it that when you drop paper behind a fan, it drops, and is not blown/sucked into the fan, whereas if you drop paper in front of a fan, it is blown away?
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Efficiency increase via ducting a fan - why is this more in viscous media?

I am looking at mixers for liquids like water or slurries. This brochure claims the following: With the optional jet ring, it is possible to increase efficiency by up 15% in water - even higher in ...
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4answers
15k views

Dyson Air Blade as a propulsion system?

I've read from many sources that Dyson Air Multipliers are more efficient and quieter than normal fans. Now, with the proof of concept, is it possible to use its principles as a propulsion system for, ...
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2answers
1k views

Fan blade physics

Why does a table fan eventually stop circulating air? I noticed this with every fan I ever used. The fan will work great for about 2 hours blowing air at full speed, then I notice that, even though ...
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2answers
3k views

Paper plane between two fans - is this possible?

The setup: two fans facing each other, distance around 1m. Both are turned on. In between them, place a simple paper plane and according to this video, it will fly. https://www.youtube.com/watch?v=...