Energy Loss in Pipe and Fittings

MEC 454 MECHANICAL ENGINEERING LAB FLUID ENERGY LOSS IN PIPE AND FITTINGS LECTURE : PN. UMI KALSOM

NAME Farah Amanina Bt Mustafa Siti Aishah Bt Abu Bakar Muhammad Amirul Shafiq Bin Mohd Shah (K) Muhammad Fadhil Bin Mohd Nazer Muhammad Firdaus Bin Abdul Razak

STUDENT’S ID 2012438514 2012442398 2012613518

2012876378 2012872676

Contents 1.0 INTRODUCTION ................................................................................................................................. 3 2.0 OBJECTIVES ....................................................................................................................................... 3 3.0 THEORATICAL BACKGROUND ........................................................................................................... 4 4.0 APPARATUS ....................................................................................................................................... 6 5.0 PROCEDURES ..................................................................................................................................... 7

1.0 INTRODUCTION In this experiment, it’s all about head losses in pipe flow. Energy head losses will always occur in pipe flow due to the skin friction on the pipe wall. Additional energy head losses occur in pipe flow due to the disturbances to pipe flow streamlines triggered by valves and such pipe fittings as bends, sudden expansions and contractions.

2.0 OBJECTIVES 1. To determine the loss of head due to friction in incompressible flow in a horizontal pipe. 2. To determine the friction factor of a pipe. 3. To determine the loss of head in sudden expansion and sudden contraction of pipes. 4. To determine the loss coefficients in sudden expansion and sudden contraction pipes. 5. To compare the losses of energy (head losses) i n different configuration of pipes.

3.0 THEORATICAL BACKGROUND Losses due to friction

Bernoulli’s equation: 

 +



  

 +   =



 +



  

 +  +  

  =   = v (constant pipe diameter) 

 = 





 = 



  = 

(pressure head at 1) (pressure head at 1) (horizontal pipe)

=>    =   -   

(1)

Equation (1) shows that the loss of head due to friction in a horizontal pipe can be determined  by measuring the differences of pressure heads between upstream and downstream ends of the pipe in which we want to measure the loss.

Friction loss (Darcy’s equation):

   =

  

 =    

where

 f  is the friction factor,  L is the length of the pipe, v is the velocity of the flow in the pipe,

(2)

d is the inside diameter of the pipe,  g is the gravitational acceleration, and  K =



 

(3)



Losses in sudden expansion and sudden contaraction of pipe

Bernoulli’s equation: 

 +



  

 +   =



 +



  

 +  + 

 = 

(pressure head at 1)

 = 

(pressure head at 1)

 





  = 

(horizontal pipe)

=>   = (  -  ) + (

  

 -

  

)

(4)

Equation (4) shows that the loss of head in sudden expansion and sudden contraction can be determined by measuring the difference of pressure heads and by measuring the velocity of flow before and after the expanded (or contraction) area of the pipe. Continuity equation:

Q =    =      =

 

  

where

  is the cross-sectional area of the pipe at section 1, and    is the cross-sectional area of the pipe at section 2.

(5)

Loss coefficient:  

  = K  

(6)



4.0 APPARATUS 4 2

3

1

2 3

4

6 1 6

8

5

Figure 1

1- Tubular steel frame with suction pads 2- Black wall 3- Ball cocks for shutting off part sections 4- Annular chambers with pressure tapping nipple 5- Double pressure gauge 6- Adjustable measurement system 7- Inlet(concealed) 8- Drain 1

to

6

measurement systems

5.0 PROCEDURES

Pipe Specifications

1. PVC 20 x 1.5 pipe: -pipe inside diameter, d = 17 mm -wall roughness, k = 0.001 mm 2. PVC 32 x 1.5 pipe: -pipe inside diameter, d = 28.4 mm -wall roughness, k = 0.001 mm 3. Measurement length of the pipe for part A, L = 800 mm.

Part A : Loss of head due to friction in PVC 20 x 1.5 pipe

1. The temperature of the room was recorded. 2. The length and inside diameter of pipe was recorded. 3. All valves were closed except those that will let the water flows from the tank to pipe 2 (see Figure 1) and return back to the tank. 4. The manometer hoses was connected to the pressure tapping points of the pipe. 5. The pump was switched on. Try to remove air bubbles from the apparatus. 6. The valve on the left side of the pipe was adjusted in order to have the difference of the manometer level (  =   -  ) of 10 mm. The value of   and   was recorded. 7. The volume flow rate (Q) was recorded and measured. 8. Steps 6 and 7 was repeated for the differ ence of manometer level (  ) of 20 mm, 40 mm, 80 mm, 120 mm, 160 mm, and 250 mm.

Part B : Loss of head due to sudden expansion from PVC 20 x 1.5 to 32 x 1.8 pipes and Part C : Loss of head due to sudden contraction from PVC 32 x 1.8 to PVC 20 x 1.5 pipes

1. Diameter inside of pipes was recorded. 2. All valves except those tht will let the water flows from the tank to pipe 1 (see figure 1) and return back to the tank was closed. The direction of flow in the pipe was verified. 3. The pressure tapping points of the sudden expansion pipe to the left manometer and the  pressure tapping points of the sudden contraction pipe was connected to the right manometer.

4. The pump was switched on. The air bubbles from the apparatus was tried to remove. 5. The valve on the left side of the sudden expansion pipe was adjusted to a certain position. 6. The value of   and   was measured and recorded. 7. The volume flow rate (Q) was measured and recorded. 8. Steps 5 to 7 for 5 values of Q was repeate d.

7.0 REFERENCES

1. Fluid Mechanics Fundamentals and Applications, Yunus A. Cengel and John M. Cimbala. 2. http://www.engineeringtoolbox.com/orifice-nozzle-venturi-d_590.html 3. http://www.maxmachinery.com/what-is-a-flow-meter/differential-pressure-flow-meters