Calculating Flow Rate and Loss Coefficients in a Complex Fluid Tank System

In summary, the two tanks are connected by a cast iron pipe. The inlet to and the exit from the pipe are abrupt and the rate of flow of water through the pipe is 6 litres/second. The loss coefficients for the given bends, entrances, and expansions are 0.5, 1.0, and 0.45, respectively. The pressure at both surfaces is the same and that term cancels out. The difference in height is equal to the head loss in the system. Reynolds number is 1.43 x 10-4, and f equals 0.0275. The delta P for water is about 27 psi.
  • #1
kris
8
0
I'm stuck with this problem, can anyone help me please?

Two large tanks are connected by a cast iron pipe 50mm in diameter and 50m long. There are eight 60 degree and four 90 degree bends along the length of the pipe. The inlet to and the exit from the pipe are abrupt and the rate of flow of water through the pipe is 6 litres/second. Determine the difference between the supplying and receiving tank.

The following values may be assumed for the loss coefficients k:

abrupt entrance k=0.5 abrupt exit k=1.0
60 degree bend k=0.45 90 degree bend k=1.15

I would appreciate any help anyone can give me. Thanks :rolleyes:
 
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  • #2
Basically you are working backwards to determine the difference in height of fluid in the two tanks. That difference creates the flow from one tank to the other. You have to take into account the head losses due to the minor losses mentioned, i.e. entrance and exit, bends, etc...
 
  • #3
kris said:
I'm stuck with this problem, can anyone help me please?

Two large tanks are connected by a cast iron pipe 50mm in diameter and 50m long. There are eight 60 degree and four 90 degree bends along the length of the pipe. The inlet to and the exit from the pipe are abrupt and the rate of flow of water through the pipe is 6 litres/second. Determine the difference between the supplying and receiving tank.

The following values may be assumed for the loss coefficients k:

abrupt entrance k=0.5 abrupt exit k=1.0
60 degree bend k=0.45 90 degree bend k=1.15

I would appreciate any help anyone can give me. Thanks :rolleyes:


use the energy equation. Take point one to be the surface of tank one and take point two to be the surface of tank two.
I don't know how to type all the symbols, but basically, the pressure at both surfaces is the same and that term cancels out. The same goes for the velocity term because the tanks are sufficiently large such that the surface is not descending.

What's left is the difference in height, which is equal to the head loss in the system. The head loss is equal to:

(Ke + 8Kb + 4KB + KE + fL/D)*(V^2/2g)

Ke, Kb, KB, and KE are the loss coefficients for the given bends, entrances, and expansions.

fL/D is the frictive loss coefficient, where
f is the resistance coefficent obtained from moody's diagram, L is the length of the pipe, and D is the diameter

V is the velocity in the pipe, which is constant because the pipe is of constant diameter and g is the gravitational acceleration

use the discharge value you were given to find the velocity and reynolds number for the moodys diagram
 
  • #4
Thank you very much
 
  • #5
Just checking

So I wondered if you could tell me what I worked out now is correct...

I got that Reynolds number is 1.43 x 10-4, and that therefore f equals 0.0275

This then gave me a value of 18.79m approx. for the difference in height.

Does this look rounghly right?
 
  • #6
I haven't had a chance to look over the numbers, but your Reynolds number looks way too low. I would double check your units on the numbers that went into that calculation.

The value for the delta P doesn't look too bad. That equates to about 27 psi for water.
 
  • #7
I re-worked it out and found that i had used of the length of the pipe in Reynolds EQn rather than the diameter. So i now get Reynolds to be about 2.8 x 10 to the 4. Which gave me a more realisistic head of 4.95m. So thanks again for your help.

PS i like you quote, its so true!
 

1. What is the purpose of a fluid tank?

A fluid tank is designed to store and contain a specific amount of liquid, such as water, oil, or gas, for various purposes. This can include providing a steady supply of liquid to a system or process, storing excess fluid for future use, or transporting liquid from one location to another.

2. How does a fluid tank work?

A fluid tank works by utilizing the principles of fluid mechanics, specifically the laws of pressure and displacement. The liquid is stored inside the tank, and the pressure exerted by the weight of the liquid causes it to flow out of the tank through an outlet. The rate of flow can be controlled by various mechanisms, such as valves or pumps.

3. What are some common problems with fluid tanks?

Some common problems with fluid tanks include leaks, corrosion, and contamination. Leaks can occur due to cracks or faulty seals, leading to loss of liquid and potential environmental hazards. Corrosion can weaken the tank and cause it to fail, while contamination can affect the quality of the stored liquid and cause damage to the tank and surrounding equipment.

4. How do you calculate the volume of a fluid tank?

The volume of a fluid tank can be calculated by multiplying the cross-sectional area of the tank by its height. This calculation assumes that the tank is a cylinder or rectangular prism shape. For irregularly shaped tanks, the volume can be determined by filling the tank with a known quantity of liquid and then measuring the depth of the liquid.

5. How do you maintain a fluid tank?

Maintaining a fluid tank involves regular inspections, cleaning, and repairs. Inspections should be done to check for any signs of damage or wear, such as leaks or corrosion. Cleaning the tank and its components can help prevent contamination and ensure the tank remains in good condition. Any necessary repairs should be done promptly to prevent larger issues and ensure the tank operates effectively.

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