EXP 1.pdf Fluid
EXP 1.pdf Fluid
EXP 1.pdf Fluid
Experiment 1
Measurement of viscosity of different types of fluid
Objectives
Overview
Measuring viscosity is an effective way to know the state (properties of matter) or
fluidity of a liquid or gas. It plays an important role in the quality control and in
various research and development stages of a wide range of industries.
Viscosity, which is also called a viscosity coefficient, is a measure of a fluids
resistance to flow. It is the substance constant indicating the magnitude of the
fluidity of a fluid. Viscous fluid is divided into two broad categories:
Brookfield Viscometer
The Brookfield Viscometer is of the rotational variety. It measures the torque
required to rotate an immersed element (the spindle) in a fluid. The spindle is driven
by a motor through a calibrated spring; deflection of the spring is indicated by a
pointer and dial (or a digital display). The viscous drag or resistance to flow is
indicated by the degree to which the spring winds up. By utilizing a multiple speed
transmission and interchangeable spindles, a variety ofviscosity ranges can be
measured. Measurements made by using the same spindle at different speeds are
used to detect and evaluate rheological properties of the test fluid.
Experimental Procedure
1. Pour the first sample into the beaker.
2. Assemble the LV spindle no. 1 onto the viscometer.
3. Level the viscometer and lower the spindle into the sample until the surface of
sample level with the groove marked on the spindle. The spindle should be
placed at the centre of the beaker. Check the level of viscometer again.
4. Select the desired speed. (Please refer to Table 1)
5. Switch on the viscometer motor.
6. Allow time for indicated reading to stabilize. A minimum of 5 revolutionsis
recommended before taking any reading.
7. To take a reading, depress the clutch lever and hold it in the down position. With
the lever still depressed, switch off the motor. Record the dial reading, indicated
by the red pointer on dial (% torque). For maximum accuracy do not take
readings below 10% torque. Repeat the measurements at least two times and
obtain an average reading.
8. Repeat step 4 to 9 with three other different speed. (12, 30 and 60 rpm).
9. Repeat step 1 to 8 for LV spindle no. 2, 3 and 4.
10. Calculate the viscosity in centipoise (cP) by multiplying the dial reading by the
factor for various spindle as shown in the Table 1 and record it in table in Results
section .
Table 1: Factor for various spindle based on the speed.
Spindle
No.
1
2
3
4
6
10
50
200
1000
Speed (rpm)
12
30
5
2
25
10
100
40
500
200
60
1
5
20
100
Results
Type of fluid = _____________________
Speed (rpm)
Spindle
No.
1
12
30
60
Dial reading
Dial reading
Dial reading
Dial reading
Average
Average
Average
Average
Viscosity (cP)
6 rpm
12 rpm
30 rpm
60 rpm
1
2
3
4
12
30
60
Dial reading
Dial reading
Dial reading
Dial reading
Average
Average
1
2
3
4
Average
Average
Viscosity (cP)
6 rpm
12 rpm
30 rpm
60 rpm
Discussion
1. Determine the difference between four calculated viscosities for different speed.
Discuss how the spindles speed of rotation and the spindle size andshape affect
the viscosity reading.
2. Plot a graph of viscosity along Y-axis versus spindle speed (rpm) along the x-axis.
3. (You can use data of spindle 1). Determine the categories of the test fluid
(Newtonian or Non-newtonian).
Tutorial
1. Define Newtonian and Non-newtonian fluid.
2. How does the viscosity of liquid vary with temperature?
3. What is the cause of viscosity in liquids?
References
1. Joseph B. Franzini. Fluid Mechanics. 10th Ed. McGrawHill (2002).
2. John F. Douglas. Fluid Mechanics with Engineering Applications. 4th Ed.Prentice Hall
(2001).
3. Noel de Nevers. Fluid Mechanics for Chemical Engineers. 2nd Ed. McGrawHill (1991).