flow rate in pipe from a storage tank

[bdp6632]

I have a storage tank with oil elevation as 20m.A pipeline flows from the bottom about 500 m long and I want to know the discharge rate at the exit of that pipe.This can only be done if I know the discharge velocity.I am applying Bernoulli equation on the pipe exit point and tank top. Can I assume that the pressure at the exit of the pipe would be atm.If I don't do this then there are lot of unknown variables in the equation. In my opinion it might not be atmospheric because there will be some pressure inside the pipe on top of the atm pressure even though I am taking into account the losses due to friction and velocity head etc.

 

[JohnGP]

At the outlet, the pressure is atmospheric. There is an exit loss that needs to be included, but after that it's atmospheric.

Cheers,
John

 

[MJCronin]

Crane 410.....

 

[iken]

Dont forget the pressure on fluid in pipe (head) changes with the level of fluid in the tank. As fluid exits, the head decreases. The velocity would also decrease as the tank empties, from max to a dribble.

 

[moswitch]

I think you'll find what your looking for at the following link:

http://www.air-dispersion.com/feature2.html

 

[Cniper]

You could use the formula - Head = Lambda LV squared over 2 gd

Or dig deeper and determine the dynamic and kinemtic viscosity to calculate the Reynolds number enabling you to determine the type of flow either lminar or turbulant which will lead to your flow rate.

I agree their are always so many variables, the inside roughness of the pipe, but viscosity in centistokes is important

 

[KernOily]

This is a Fluid Mechanics 101 problem. Suggest you crack open your fluids textbook from college, Mark's, or Crane TP 410. In fact this exact problem is in the Crane 410.

Always best to check your basic references first. This way you become educated on the problem, you have learned something, and you have learned your references better. All of these benefit you in the future. It's a win-win for you.