Thermofluids Lab – Mec454 / Ls1/ Rev. 02-2016

Thermofluids Lab – MEC454 / LS1/ Rev. 02-2016

UNIVERSITI TEKNOLOGI MARA FAKULTI KEJURUTERAAN MEKANIKAL Program

: Bachelor of Engineering (Hons) Mechanical (EM220) Bachelor of Mechanical Engineering (Manufacturing) (Hons) (EM221)

Course

: THERMOFLUIDS LAB

Course Code : MEC454

Course Outcome: CO1 CO2 CO3 CO4

Conduct each experiment correctly through established procedures and good record keeping. [PO1, LO1, SS1]{C2}. Analyze the basic experimental data accordingly as required by each experiment [PO2, LO3, SS1]{C4}. Produce a basic technical report for each experiment in a structured format and professional manner [PO9, LO4, SS2]{A2}. Work in a group as a leader or as a member [PO10, LO9, SS3]{A4}.

LAB SHEET NO: 3 TITLE: ENERGY LOSSES IN PIPES AND FITTINGS 1.0 OBJECTIVES The objectives of this experiment are: 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, and 5. to compare the losses of energy (head losses) in different configuration of pipes.

Thermofluids Lab – MEC454 / LS1/ Rev. 02-2016

2.0 APPARATUS

Figure 1 3.0 THEORETICAL BACKGROUND Losses due to friction

Pipe diameter d h1

h2

1 v

L

Figure 2 Bernoulli’s equation:

p1 v12 p v 2   z1  2  2  z2  h f g 2 g g 2 g

2

Thermofluids Lab – MEC454 / LS1/ Rev. 02-2016

v1  v2  v p1  h1 g p2  h2 g z1  z2 

(constant diameter pipe) (pressure head at 1) (pressure head at 2) (horizontal pipe)

h f  h1  h2

(1)

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

fLv 2 hf   Kv 2 d 2g

(2)

where f is the friction factor, L is the length of the pipe, v is the velocity of the flow in the pipe, d is the inside diameter of the pipe, g is the gravitational acceleration, and

K

fL d 2g

(3)

Losses in sudden expansion and sudden contraction of pipe

h1

h2

h1

2

1

h2

1

2

v1

v2

v1

Pipe diameter d1

Pipe diameter d2

Pipe diameter d1

Figure 3

v2

Pipe diameter d2

Thermofluids Lab – MEC454 / LS1/ Rev. 02-2016

Bernoulli’s equation:

p1 v12 p v 2   z1  2  2  z2  h g 2 g g 2 g p1  h1 g p2  h2 g z1  z2 

(pressure head at 1) (pressure head at 2) (horizontal pipe)

v 2 v 2  h   h1  h2    1  2   2g 2g   

(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 contracted) area of the pipe. Continuity equation:

Q  A1v1  A2v2

A  v1  2 v2 A1

(5)

where A1 is the cross-sectional area of the pipe at section 1, and A2 is the cross-sectional area of the pipe at section 2. Loss coefficient:

v 2 h  K 2 2g

(6)

Thermofluids Lab – MEC454 / LS1/ Rev. 02-2016

4.0 METHOD OF APPROACH Pipe Specifications

1. 2. 3.

PVC 20 x 1.5 pipe: - pipe inside diameter, d = 17 mm - wall roughness, k = 0.001 mm PVC 32 x 1.8 pipe: - pipe inside diameter, d = 28.4 mm - wall roughness, k = 0.001 mm 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. 2. 3. 4. 5.

6. 7. 8.

Record temperature of the room. Record the length and inside diameter of the pipe. Close all valves except those that will let the water flows from the tank to pipe 2 (see figure 1) and return back to the tank. Verify the direction of flow in the pipe. Connect the manometer hoses to the pressure tapping points of the pipe. Switch on the pump. Try to remove air bubbles from the apparatus. Adjust the valve on the left side of the pipe in order to have the difference of manometer level (hf = h1 – h2) of 10 mm. Record the value of h1 and h2. Measure and record the volume flow rate (Q). Repeat steps 6 and 7 for difference of manometer level (hf) 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 PVC 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. 2. 3. 4. 5.

6. 7. 8.

Record inside diameter of the pipes. Close all valves except those that will let the water flows from the tank to pipe 1 (see figure 1) and return back to the tank. Verify the direction of flow in the pipe. Connect the pressure tapping points of the sudden expansion pipe to the left manometer and the pressure tapping points of the sudden contraction pipe to the right manometer. Switch on the pump. Try to remove air bubbles from the apparatus. Adjust the valve on the left side of the sudden expansion pipe to a certain position. Measure and record the value of h1 and h2. Measure and record the volume flow rate (Q). Repeat steps 5 to 7 for 5 values of Q.

5.0 DATA AND CALCULATION 1. 2. 3.

For part A, put the data obtained in Table 1 (See end of this manual). Calculate the remaining parameters using formula given in the theoretical part. For part B, put the data obtained in Table 2 (See end of this manual). Calculate the remaining parameters using formula given in the theoretical part. For part C, put the data obtained in Table 3 (See end of this manual). Calculate the remaining parameters using formula given in the theoretical part.

Thermofluids Lab – MEC454 / LS1/ Rev. 02-2016

6.0 RESULTS AND DISCUSSION Part A: Loss of head due to friction in PVC 20 x 1.5 pipe

1. 2.

Plot the curve hf against v2 in a graph paper. Obtain the slope that indicates the value of K (eq. 2). Calculate the friction factor (eq. 3). Discuss the curve obtained. Part B: Loss of head due to sudden expansion from PVC 20 x 1.5 to PVC 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. 2.

Plot the curves h against v22/(2g) in one graph paper (superimpose the two curves). For each curve, obtain the slope that represents the loss coefficient, K (eq. 6). Discuss the curves obtained. Overall loss of head

1. 2.

For all parts A to C, plot the curves of head loss against flow rate Q in one graph paper (superimpose all curves). Discuss the curves obtained; which ones produce more loss, which ones produce less loss.

7.0 REPORT Each group must submit a report no later than one week after the experiment. The report must contain at least: 1. Cover page 2. Typed introduction, theoretical background, procedures, data and tables (to be done by the group) 3. Discussion, conclusion and references (to be done individually in the same report) 4. Appendix: Hand written raw data taken during the experiment and signed by the lecturer (or lab. technician) after the experiment.

NEW EDITION: 21 JULY 2006 BY PROF. MADYA DR. WIRACHMAN WISNOE REVISION 1: 2014 REVISION 2: 3 MARCH 2016 BY PROF. DR. WIRACHMAN WISNOE

Thermofluids Lab – MEC454 / LS1/ Rev. 02-2016

Part A: Loss of head due to friction in PVC 20 x 1.5 pipe Pipe length, L= mm = Pipe inside diameter, d= mm = Pipe cross-sectional area,

Measurement No. 1 2 3 4 5 6 7

A= (b) Time observed

(litres)

(s)              

m2

 

(a) Volume measured              

m m

(a) / (b)

eq. 5

(c)

(d)

eq. 1

(e)

Q

v

h1

h2

hf

v2

(m/s)

(mm)

(mm)

(litres/s)              

(m3/s)               Table 1

Signature of Lecturer or Lab. Technician: Date:

             

             

             

(mm)              

(m2/s2)

(m)              

             

Thermofluids Lab – MEC454 / LS1/ Rev. 02-2016

Part B: Loss of head due to sudden expansion from PVC 20 x 1.5 to PVC 32 x 1.8 pipes Upstream pipe inside diameter,

 

d1 =

Upstream pipe cross-sectional area, Downstream pipe inside diameter,

mm =

A1 =

m m2

 

 

 

d2 =

Downstream pipe cross-sectional area,

A2 =

 

 

m2

Gravitational acceleration,

g=

 

 

m/s2

 

mm =

m

(a)

(b)

(a) / (b)

eq. 5

eq. 5

(c)

(d)

(e)

(f)

eq. 4

Measurement

Volume measured

Time observed

Q

v1

v2

v12/(2g)

v22/(2g)

h1

h2

hl

No. 1 2 3 4 5

(litres)

(s)

(m/s)          

(m/s)

(m)

(m)

(mm)

(mm)

         

         

(litres/s)          

(m3/s)           Table 2

Signature of Lecturer or Lab. Technician: Date:

         

         

         

         

         

(mm)          

(m)          

Thermofluids Lab – MEC454 / LS1/ Rev. 02-2016

Part C: Loss of head due to sudden contraction from PVC 32 x 1.8 to PVC 20 x 1.5 pipes Upstream pipe inside diameter,

 

d1 =

Upstream pipe cross-sectional area, Downstream pipe inside diameter,

mm =

A1 =

m m2

 

 

 

d2 =

Downstream pipe cross-sectional area,

A2 =

 

 

m2

Gravitational acceleration,

g=

 

 

m/s2

 

mm =

m

(a)

(b)

(a)/(b)

eq. 5

eq. 5

(c)

(d)

(e)

(f)

eq. 4

Measurement

Volume measured

Time observed

Q

v1

v2

v12/(2g)

v22/(2g)

h1

h2

hl

No. 1 2 3 4 5

(litres)

(s)

(m/s)          

(m/s)

(m)

(m)

(mm)

(mm)

         

         

(litres/s)          

(m3/s)          

Table 3

Signature of Lecturer or Lab. Technician: Date:

         

         

         

         

         

(mm)          

(m)