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Laminar Flow Viscometer - Fluid Flow - Lab Manual, Study notes of Fluid Dynamics

National Institute of Industrial EngineeringFluid Dynamics

Topics covered in this course include fluid properties, fluid statics, fluid kinematics, control volume analysis, dimensional analysis, internal flows, differential analysis, external flows CFD, compressible flow and turbomachinery. This is lab manual. Key points are: Laminar Flow Viscometer, Viscometer Reservoir and Capillary Tubes, Coefficient of Viscosity, Kinematic Viscosity

Typology: Study notes

2012/2013

Uploaded on 10/02/2013

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Laminar Flow Viscometer
Nomenclature
A cross-sectional flow area
d inside diameter of a pipe or “device”
f Darcy friction factor: for laminar flow, f = 64/Red
g gravitational constant (9.81 m/s2)
h head, i.e. elevation of a fluid column
hmajor major head loss (height of water column) due to friction in a pipe
hminor minor head loss (height of water column) due to a “device” in the pipe system
hL, total total irreversible head loss, including major and minor losses: , total major minorL
hhh

K nondimensional minor loss coefficient
L length of a pipe or capillary tube
Le entrance length required to establish fully developed flow in a pipe or capillary tube
m mass flow rate through the pipe
P static pressure
Red Reynolds number based on diameter d: Red =
VD/
= Vd/
t time
T temperature
V mean velocity in a pipe
V volume
V
(or Q) volume flow rate
p
ump
W
work done to the control volume by a pump
turbine
W
work done by the control volume on a turbine
viscous
W
viscous work done on the control volume by a moving wall
z elevation in vertical direction
kinetic energy correction factor in energy equation for a control volume
coefficient of dynamic viscosity (also called simply the viscosity)
coefficient of kinematic viscosity (for water, 1.0 10-6 m2/s at room temperature)
density of the fluid (for water,
998 kg/m3 at room temperature)
Educational Objectives
1. Provide an opportunity for students to apply their knowledge
of laminar internal pipe flow to the practical problem of
measuring fluid viscosity.
2. Provide an opportunity for students to plan their own
experiment and to develop a sound experimental procedure,
using the available equipment.
Equipment
1. laminar flow viscometer test stand (see Figure 1)
2. immersion heater (installed in reservoir, as in Figure 1)
3. capillary tubes of various diameters and lengths (diameters are
labeled on each tube)
4. stopwatch
5. graduated cylinders of various capacities
6. hot plate and insulated gloves, Pyrex beakers
7. thermometer and/or thermocouple
8. digital balance scale
1
2
z2
z1
Level
indicator
tube
Ball valve
Capillary tube,
inner diameter = d
Swagelok fitting,
inner diameter =
0.5 in. (12.7 mm)
Rese rvoir
10.3 mm I.D.
Heater
Figure 1. Schematic diagram of laminar flow
viscometer.
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Laminar Flow Viscometer

Nomenclature

A cross-sectional flow area d inside diameter of a pipe or “device” f Darcy friction factor: for laminar flow, f = 64/Re d g gravitational constant (9.81 m/s 2 ) h head, i.e. elevation of a fluid column h (^) major major head loss (height of water column) due to friction in a pipe h minor minor head loss (height of water column) due to a “device” in the pipe system

 h L , total total irreversible head loss, including major and minor losses:^  h^ L^ , total ^  h major^  h minor

K nondimensional minor loss coefficient L length of a pipe or capillary tube L (^) e entrance length required to establish fully developed flow in a pipe or capillary tube m  mass flow rate through the pipe P static pressure

Re d Reynolds number based on diameter d : Re d =  VD /  = Vd/ 

t time T temperature V mean velocity in a pipe V (^) volume V ^ (or Q ) volume flow rate W pump^ work done to the control volume by a pump

W turbine^ work done by the control volume on a turbine

W viscous^ viscous work done on the control volume by a moving wall z elevation in vertical direction

 kinetic energy correction factor in energy equation for a control volume

 coefficient of dynamic viscosity (also called simply the viscosity)

 coefficient of kinematic viscosity (for water,^ ^ ^ 1.0^ ^10 -6^ m^2 /s at room temperature)

 density of the fluid (for water,   998 kg/m 3 at room temperature)

Educational Objectives

  1. Provide an opportunity for students to apply their knowledge of laminar internal pipe flow to the practical problem of measuring fluid viscosity.
  2. Provide an opportunity for students to plan their own experiment and to develop a sound experimental procedure, using the available equipment.

Equipment

  1. laminar flow viscometer test stand (see Figure 1)
  2. immersion heater (installed in reservoir, as in Figure 1)
  3. capillary tubes of various diameters and lengths (diameters are labeled on each tube)
  4. stopwatch
  5. graduated cylinders of various capacities
  6. hot plate and insulated gloves, Pyrex beakers
  7. thermometer and/or thermocouple
  8. digital balance scale

z 2 2

z 1

Level indicator tube

Ball valve

Capillary tube, inner diameter = d

Swagelok fitting, inner diameter = 0.5 in. (12.7 mm)

Reservoir

10.3 mm I.D.

Heater

Figure 1. Schematic diagram of laminar flow viscometer.

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  1. ruler or tape measure
  2. level
  3. shop air supply with nozzle (for blowing out the tubes)
  4. personal computer

Background

Viscosity is a very important fluid property, especially in pipe flow systems where the pressure drop through a pipe (and hence the required pumping power) is strongly affected by viscosity. There are many experimental techniques commonly used to measure the viscosity of a liquid. Examples include the rotating cup viscometer and the falling-ball viscometer.

The viscosity of a liquid, such as water, typically decreases with temperature, while that for a gas typically increases with temperature. A simple way to remember this is to think about starting a car in the winter time. In very cold temperatures, the engine oil is extremely viscous (most people call it “thick”), and the engine is hard to start. However, the oil in a warm engine has a much lower viscosity, and is much easier to start.

One of the simplest viscosity measurement techniques involves forcing the liquid through a very small diameter pipe (capillary tube). Because of the slow speeds and small diameter, the flow is laminar, and an analytical expression for viscosity is obtainable. Namely, viscosity can be calculated as a function of easily measurable parameters, such as tube diameter, tube length, volume flow rate, etc.

In this lab experiment, you will obtain an analytical equation for , the coefficient of dynamic viscosity. You will

design a procedure, using the available equipment, which will enable you to measure the viscosity of water at several temperatures. Your results will then be compared to published data.

References

  1. Çengel, Y. A. and Cimbala, J. M., Fluid Mechanics – Fundamentals and Applications , McGraw-Hill, NY, 2006.
  2. White, F. M., Fluid Mechanics , Ed. 5, McGraw-Hill, NY, 2003.

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