Fluid Friction Measurements

FLUID FRICTION MEASUREMENTS
YEDITEPE UNIVERSITY DEPARTMENT OF MECHANICAL ENGINEERING

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YEDITEPE UNIVERSITY ENGINEERING FACULTY MECHANICAL ENGINEERING LABORATORY

Fluid Friction Measurements
1. Objective: Ø To determine the head loss. Ø To determine the head loss associated with flow of water through standard fittings used in plumbing installations. Ø To determine the relationship between friction coefficient and Reynolds’ number for flow of water through a pipe having a roughened bore. Ø To determine the water velocity by using flow measurement devices. 2. Equipment:

The test pipes and fittings are mounted on a tubular frame carried castors. Water is fed in from the hydraulics bench via the barbed connector (1), and is fed back into the volumetric tank via the exit tube (23). · · · · · · · · · · · · · · An in-line strainer (2) An artificially roughened pipe (7) Smooth bore pipes of 4 different diameter (8), (9), (10) and (11) A long radius 90° bend (6) A short radius 90° bend (15) A 45° “Y” (4) A 45° elbow (5) A 90° “T” (13) A 90° mitre (14) A 90° elbow (22) A sudden contraction (3) A sudden enlargement (16) A pipe section made of clear acrylic with a Pitot static tube (17) A Venturi made of clear acrylic (18)
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An orifice meter made of clear acrylic (19) A ball valve (12) A globe valve (20) A gate valve (21)

3. Theory: 3.1 Fluid Friction in a Smooth Bore Pipe Two types of flow may exist in a pipe: 1) Laminar flow at low velocities where h ∝ V 2) Turbulent flow at higher velocities where h ∝ V n where h the head loss due to friction, V the fluid velocity, and 1.7 < n < 2.0. These two types of flow are separated by a transition phase where no definite relationship between h and V exists. Laminar

Transient

Turbulent

The friction factor, λ , is defined as,

∆h = where ∆h L D V

λ⋅L V2 ⋅ D 2⋅ g

the head loss [m] the length between the tapping [m] the diameter of the pipe [m] the mean velocity [m/s]

The Reynolds’