# The Naked Scientists Forum

### Author Topic: Bernoulli and Derivation  (Read 1327 times)

#### jasoturner

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##### Bernoulli and Derivation
« on: 30/05/2013 16:59:11 »
Hi, I am getting rusty.  We know that for air flow through a fan, in English units under typical conditions, the Bhp required is calculated as:

BHP =  (CFM * Pressure) / 6356 * Eff), where pressure is in inches of water and Eff is the fan efficiency.

We also know from Bernoulli's equation that, if we ignore changes in elevation:

P1 + KE1 + Energy Input = P2 + KE2

My understanding is that we can assume the air out in the room somewhere is essentially not moving, so we have Energy Input = (P2-P1) + KE2.

Here's what's driving me batty.  I am trying to derive the 6356 constant and can't seem to do it.  Am I missing something?  Wrong approach?  The units get scrambled on me.

#### yor_on

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##### Re: Bernoulli and Derivation
« Reply #1 on: 30/05/2013 19:36:39 »
http://www.scribd.com/doc/13839504/HVAC-Constants

#### The Naked Scientists Forum

##### Re: Bernoulli and Derivation
« Reply #1 on: 30/05/2013 19:36:39 »