-bernoulli principle in fan-

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----bernoulli principle in fan----

when a fan is started, why is there more air flow at the bottom of the fan and not at the upper region of fan...:confused:

>>Also explain if bernoulli principle is involved in this


thx an regards

arun
 

Answers and Replies

  • #2
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When a fan is started?Explain what time interval do you think of.
Probably,the effect has something to do with low rotating speeds of various
parts of a fan during the start-up phase.
 
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  • #3
russ_watters
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And what kind of fan?
 
  • #4
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when a fan is started, why is there more air flow at the bottom of the fan and not at the upper region of fan...:confused:

>>Also explain if bernoulli principle is involved in this


thx an regards

arun
Arun,
tell me bottom refers to center? and upper refers to tip of the blades? the fan axis is verticle or horizontal?
I ll get you correct answer.
 
  • #5
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i mean a ceiling fan.....by bottom i mean the region below the blades (may be the the entire area where we feel cool air ) and by upper region, i mean the area above the blades...

thx
 
  • #6
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because when the air passes blades, air gets kinetic energy added from blades to it and moves faster than the suction side air.

Faster moving air makes you feel cool.

I hope, now you yourself can apply bernoulis eqn.

U R FROM TAMILNADU?
 
  • #7
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@ ramesh
thx for ur reply ....ok i agree that the surroundin air gains kinetic energy ....we also know from bernoulli that as velocity increases,pressure decreases.
Now my question is how do we relate this ....in which region is there higher and lower pressure?? and y don we feel the cool air at the upper region of the ceilin fan?

yes sir, i am from Tamil Nadu ....nice seein u . BTW whr r u from in TN

regards,

arun
 
  • #8
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@ ramesh
thx for ur reply ....ok i agree that the surroundin air gains kinetic energy ....we also know from bernoulli that as velocity increases,pressure decreases.
Now my question is how do we relate this ....in which region is there higher and lower pressure?? and y don we feel the cool air at the upper region of the ceilin fan?

yes sir, i am from Tamil Nadu ....nice seein u . BTW whr r u from in TN

regards,

arun
Replied in your PM.
 
  • #9
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I presume fan is a room cooling fan with no duct or cowl. If it is close to a table top or floor then that surface will have a partial ducting effect for airflow from bottom part of fan where that restriction will reduce the dispersion, mixing, and thus slowing of volumes of air in that region. The moving air will tend to follow close to a surface (see Coanda Effect). Bernoulli effect can be demonstrated at that surface eg by an open book or small pile of paper sheets just as wind from an open window will scatter papers from a desk.

From Darmog
 

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