need information

[rakesh v]

Hi Guys,
hw ru. hope things are going great with you. i need a small
information form you.
can any tell me
1. how to calculate flowrate in a pipe if pipe dia and pressure is known

its urgent for me.

Regards,
Rakesh

[Arun Kumar]

Hi Rakesh,

 

I think, you can use Bernoullis equation in simple by assuming that friction is zero

 

(Velocity-1)/2g +g (z-1)+ (p-1)/Density=(Velocity-2)2/2g +gz +(p-1)/Density

 

You can consider V1=0 and same elevation z1=z2

 

Velocity= ( Q/A)

 

Delta P/ Density= (velocity-2)2/2g

                        = (Q/A)2/2g

                    Q2=(Delta P * Density *2g* A2)/density)

                       =(Delta P* Density*2g*Pi*D2/4)/Density

                   Q=Sqrt( (Delta P* Density*2g*Pi*D2/4)/Density))

 

Thanks and Regards,

Arun

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[Arun Kumar]

---------- Forwarded message ----------
From: Arun Kumar <arun...@gmail.com>
Date: Tue, Mar 13, 2012 at 12:19 PM
Subject: Re: need information
To: petror...@googlegroups.com

Hi Rakesh,

 

some mistakes in typing formulae in my last mail,

 

I think, you can use Bernoullis equation in simple by assuming that friction is zero

 

(Velocity-1)/2g +g (z-1)+ (p-1)/Density=(Velocity-2)2/2g +gz +(p-1)/Density

 

You can consider V1=0 and same elevation z1=z2

 

Velocity= ( Q/A)

 

Delta P/ Density= (velocity-2)2/2g

                        = (Q/A)2/2g

                    Q2=(Delta P *2g* A2)/density)

                       =(Delta P*2g*Pi*D2/4)/Density

                   Q=Sqrt( (Delta P*2g*Pi*D2/4)/Density))

[rakesh v]

Thanks Arun,
but the issue is that i'm having conditions only at one point. so
bernoulis theorem cannot be used i tried using it.
even hagen poisullie equation gives differential pressure so it also
cannot be used.....

let me tell you the case.
we are having service water pump which pump service water through out
the plant. but in each unit it has its own specific pressure
requirements which are attained by using expanders etc., so my supply
header is at 7.5 Kg/cm2 pressure. where as in my unit it is at 3
kg/cm2 pressure. so i need to calculate flow rate.
as the plant is still under construction we are evaluating the design
data so no flow meters / pitot tubes can be used.

if we look at the question in other way it looks more practical. for
suppose if we have flowrate and pipe size then it is more realistic if
we need to calculate pressure and looks like we can. but now the same
question is in reverse condition which leads to 2 unknowns flowrate
and velocity.

let me know if any one can solve it. its a 4" pipe and 3 kg/cm2 pressure.

Arun where ru now. what ru doing and hws amrutha

Regards,
Rakesh

On 13/03/2012, Arun Kumar <arun...@gmail.com> wrote:
> ---------- Forwarded message ----------
> From: Arun Kumar <arun...@gmail.com>
> Date: Tue, Mar 13, 2012 at 12:19 PM
> Subject: Re: need information
> To: petror...@googlegroups.com
>
>
> Hi Rakesh,
>
>
> some mistakes in typing formulae in my last mail,
>

> *I think, you can use Bernoullis equation in simple by assuming that
> friction is zero*

[Arun Kumar]

Hi rakesh,

 

Your Delta P = 7.5-3 =4.5 Kg/cm2 & density of water is 1000Kg/cm3 & Diameter is 4"

 

Q=Sqrt( (Delta P*2g*Pi*D2/4)/Density))

Everything is known for solving this for the above equation. So whats the concern..?

 

Regards,

Arun

[rakesh v]

arun,
the pressure is reduced using a reducer so velocity changes this 4"
line is a tapping from 10" line.

in 10" line pipe pressure is 7.5 kg/cm2. which is having many branches
/ tappings of 4", 6", 2" etc.,

so i'm concerned with the flow in a 4" pipe only but the flow and
pressures in other pipes will also effect here.

as of now i submitted in this way
i back calculated the velocity in the header and used the same
velocity in the 4" pipe (in which i need to calculate the flowrate).
but as pressures are different i'm not sure how far this is correct.
PV = Const cannot be used here as its for static conditions like
in a storage tank etc., but not in pipe flow.

now the only way left is now to recheck by calculate the pressure
exerted by liquid using velocity and flowrate and cross sectional
areas. but i'm not getting this formula also......

On 13/03/2012, Arun Kumar <arun...@gmail.com> wrote:

> *Hi rakesh,*
>
> *Your Delta P = 7.5-3 =4.5 Kg/cm2 & density of water is 1000Kg/cm3 &
> Diameter is 4"*
> **
> *Q=Sqrt( (Delta P*2g*Pi*D2/4)/Density))
> *
> *Everything is known for solving this for the above equation. So whats the
> concern..?*
> **
> *Regards,*
> *Arun*
> **

[Arun Kumar]

If you have multiple branches, you can use Hysis/aspen to solve this

[rakesh v]

yupppppppppppp

Hysys should checkout. any way thanks dude...... let me try.......

so hw r things going. where ru working now yar...... every time i ask
you this question and ur not answering this....