How Does a 90-Degree Bend Affect Pressure Drop in Pipes?

[Yogesh Kamble]

I have a centrifugal pump that gives flow of 56 lit/min at 50 psi.
Media: clear water, Temp. ambt
The discharge pipe size: 1 1/2", Material: SS
Total pipe length: 14 feet

At 3 feet from pump discharge there is 90 degree bend and again at 6feet there is 90 degree bend. My question is what would be the pressure drop due to bends.
and how to calculate that...

 

[LowlyPion]

I have a centrifugal pump that gives flow of 56 lit/min at 50 psi.
Media: clear water, Temp. ambt
The discharge pipe size: 1 1/2", Material: SS
Total pipe length: 14 feet

At 3 feet from pump discharge there is 90 degree bend and again at 6feet there is 90 degree bend. My question is what would be the pressure drop due to bends.
and how to calculate that...

Welcome to PF.

It will help if you have the pressure loss coefficient for the bends.

Here is a link that might help point you in the right direction:
http://www.engineeringtoolbox.com/minor-pressure-loss-ducts-pipes-d_624.html

 

[nlightner]

I would approach this question by first understanding the factors that affect pressure drop in a pipe. These include the fluid properties (in this case clear water), the pipe dimensions and material, and the flow rate. Additionally, the geometry of the pipe, such as bends or elbows, can also contribute to pressure drop.

To calculate the pressure drop in a bend pipe, we can use the Bernoulli's equation, which states that the total energy of a fluid remains constant along a streamline. This equation takes into account the fluid velocity, pressure, and elevation at different points in the pipe.

In this scenario, we have a centrifugal pump that is providing a flow of 56 liters per minute at 50 psi. The discharge pipe has a diameter of 1 1/2 inches and is made of stainless steel. The total pipe length is 14 feet, with two 90 degree bends, one at 3 feet from the pump discharge and another at 6 feet.

To calculate the pressure drop at the first bend, we can use the following equation:

ΔP = 0.5 * ρ * (V2^2 - V1^2)

Where:
ΔP = pressure drop
ρ = density of the fluid
V1 = velocity of the fluid before the bend
V2 = velocity of the fluid after the bend

To determine the velocities, we can use the continuity equation, which states that the mass flow rate is constant throughout the pipe.

m_dot = ρ * A * V

Where:
m_dot = mass flow rate
ρ = density of the fluid
A = cross-sectional area of the pipe
V = velocity of the fluid

Since we know the flow rate (56 liters per minute) and the pipe diameter (1 1/2 inches), we can calculate the velocity before and after the bend. Then, using the Bernoulli's equation, we can determine the pressure drop at the first bend.

To calculate the pressure drop at the second bend, we can use the same approach, but this time the velocity before the bend would be the velocity after the first bend, and the velocity after the bend would be the final velocity at the end of the pipe.

It is also important to note that the pressure drop in a bend pipe is dependent on the angle of the bend, with tighter bends resulting in higher pressure drops. Therefore, the pressure drop at the second bend may be slightly higher than