Experiment 1 - Friction Losses in Pipes-report

LABORATORY

REPORT

FLUID

MECHANICS LABORATORY SKPU 1711

EXPERIMENT 1 :24th February 2014

FRICTION LOSSES IN PIPES

MUHAMMAD KHAIRIL IKRAM(A13KP0047) AKMAL FAIZ BIN ABDUL RAHIM (A13KP0008) ABDUL WAHAB (A13KP4006) KSATRIYA ANANTAYUTYA (A13KP4001)

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Report summary: The experiment was undertaken to measure the head lost in the pipe due to shear stress between the fluid and the wall of the pipe. Different flow rates were introduced along with a different diameters and roughness of the pipes. Therefore we measured the friction factor of the pipes using our measurements. Fluid velocity was also studied and related to the diameter, flow rate and roughness of the pipe during the experiment. As the flow rate, Q was changed, the values for the inlet and outlet, H1 and H2 were measured. The Flow rate was changed to a range of different values and hence the respective values of H1 and H2 were recorded. The procedure was repeated for the for the different pipes which include, rough, smooth, sudden contraction and sudden enlargement pipes. Reynolds number was used to understand the variation of the flow between the laminar and the turbulent flows. As the Laminar flow (f) can be known by analysis while the turbulent flow (f) is found experimentally. As the frictional factor increased the Reynolds number decreased, this shows the inverse proportion between the friction factor (f) and the Reynolds number. The head loss was also found to increase with increase in the velocity. As during the sudden enlargement, the minor loss was also increased. To conclude, we chiefly studied the head losses in the pipes as along pipes of different diameters and roughness. There were few improvements required which include the forming of bubble along the inlets which gave inconsistent readings and there were few leaking inlets which affected the value of the flow rate. With these errors taken into consideration, the experimental results would be better.

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THEORY In Bernoulli’s equation as shown below, hf represents the head loss due to the friction between the fluid and the internal surface of the constant diameter pipe as well as the friction between the adjacent fluid layers p1/g + V1²/2g + Z1 = p2/g + V2²/2g + Z2 + hf (1)

This will result in a continuous change of energy from a valuable mechanical form (such as kinetic or potential energies) to a less valuable thermal form that is heat. This change of energy is usually referred to as friction head loss, which represents the amount of energy converted into heat per unit weight of fluid. The head losses (hf) in pipe due to friction can be determined using Darcy-Weisback equation;

Turbulent flow

(2)

Laminar flow (3) Where: f = Friction factor L = Length V = Mean velocity (Q/A) 3

g = Gravity D = Constant diameter

The friction head loss for both laminar and turbulent flows can be expressed by similar formulas although the original derivation of each one is different: (4)

In laminar flow, the friction factor is only a friction of Reynolds number while for turbulent flow it is a function of Reynolds (Re) number and the relative roughness of the pipe. Re = VD / 

(5)

Where : density, V: average velocity, D: Pipe inside diameter, : Viscosity.

Based on the nature of the flow, friction factor (f) can be estimated using the following correlations

Laminar flow

f = 64/Re

(6)

Turbulent Flow

f =0.316 x Re -0.25

(7)

Equation (7) is Blausius Equation and only valid for smooth pipe and 3000 Ksudden contraction Hence, the precautionary steps should be taken to get the best result in order to avoid all the errors come out. Some of the steps are to make the flow rate of the water source consistent and remove the bubble from the tubes in the measurements.

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REFERENCES A)

Rolf H. Sabersky, Allan J Acosta, Edward G. Hauptmann and E.M. Gates, "Fluid Flow-A First Course of Fluid Mechanics" (Fourth Edition), Prentice Hall Inc., 1999.

B)

R.V Giles, “Fluid Mechanics and Hydraulics” (Third Edition), McGrawHill Inc;

1994. C)

Lab Manual University Teknologi Malaysia.

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Appendix Sample Calculation For pipe 1 and 2 (i)

(ii)

(iii)Reynolds Number for Pipe 1A

(iv)Turbulent flow,

(v)

(vi)

(vii) fexp,

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Same method using for data of Pipe 1(B), 2(A) and 2(B) in determine of Reynolds Number:1B: Re = 27.5 x 103 x V 2A: Re = 16.4 x 103 x V 2B: Re = 15.5 x 103 x V Losses in Pipe of Sudden Enlargement Pipe (i)

(ii)h = h1 – h2 = 582-570 mm = 12 mm = 0.012 m (iii)

(iv)

(v)

(vi)

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(vii)

Losses in Pipe of Sudden Contraction Pipe Note: Same method uses to find value of Q, h as shown in calculation of losses in pipe of sudden enlargement pipe. (i)

(ii)

(iii)

(iv)

(v)

Losses in Pipe for 900 Bend Pipe and Elbow Pipe Note: Same method uses to find value of Q, h as shown in calculation of losses in pipe of sudden enlargement pipe.

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(i)

(iii)

(iv)

(v)

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