How to use Bernoulli's Equation Correctly?

[xian_kgx]

One large pipe is splitted into 2 smaller pipes. Can we use Bernoulli's equation and say that the total head at a point in the large pipe is equal to a point at one of the 2 smaller pipes? Why is energy not conserved?

 

[FredGarvin]

There are 3 main assumptions in the derivation of the Bernoulli equation. What are they?

 

[machinest]

energy not conserved cuase of the losses-
as long as there is a flow then there is a difference in energy-which cuased the flow to occur-
there is the primary losses(friction)and the secondry(valve,bend-)which u don have here--
if u could show ur pipe system-it would be more clear for us-
wish i could help

 

[RainmanAero]

Hi Fred,

Good hints. Check my answers and let me know if I got all of them!

There are 3 main assumptions in the derivation of the Bernoulli equation. What are they?

1) Constant mass flow rate (no surges).
2) Frictionless (no heat transfer).
3) Irrotational (translational velocity only).

How'd I do?
Rainman

 

[FredGarvin]

They are:
- Incompressible
- Inviscous
- Steady State
Since it also is applied along the streamline, so the irrotational part holds too.
A+ for Rainman

As for the main post, energy will not be conserved because of the losses due to friction. Also, you do not state the fluid involved. If it is a liquid, then the incompressibility assumption is pretty much valid. If it is a gas, you need to be concerned with it.