PETROCHEMICALS & PETROLEUM REFINING TECHNOLOGY
EXPERIMENT 3
1. OBJECTIVES

To study the viscosity of the of lubricant oil.

To determine the dynamic viscosity of lubricant oil at various temperature.
2. SUMMARY
Viscosity can be defined as a measure of a fluid’s resistance to flow. There are 2 different
types of fluid characterizations which are the Newtonian fluid and Non- Newtonian Fluid. The
Newtonian fluid is when the ratio of shear stress to shear rate or viscosity is constant thus shear
stress (t) is a measure of the force of friction from a fluid acting on a body in the path of that fluid.
Meanwhile, for the Non- Newtonian fluid, viscosity of the fluid is not constant thus shear rate is
the rate of change of velocity at which one layer of fluid passes over an adjacent layer. The
experiment was conducted by using the Saybolt Viscometer. The material used was only lube oil
but with different temperature of Saybolt Viscometer Bath which were 40o C, 50o C and 60 o C.
Based on the results, For the first objective, the viscosity decreases as temperature increases where
the temperature of 40°C gives 0.93 cP, 50°C displays 1.19 cP and lastly, 60°C shows 1.46 cP of
viscosity which follow the Newton’s rule. Hence, the greater the internal friction, the greater the
stress (force per unit area) required to promote the movement. Furthermore, as can be seen in table
2, the longest time taken recorded is 47.7s at 40°C while for 50°C, the time taken is 38.1s and the
fastest time taken is 30.5s at 60°C. Thus, as viscosity is decreased then the temperature is increased.
So, the relationship between temperature and viscosity is inversely proportional for all substances
because the increased kinetic motion at higher temperatures promotes the breaking of
intermolecular bonds between adjacent layers. So, the objectives of the experiment are achieved
successfully.
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PETROCHEMICALS & PETROLEUM REFINING TECHNOLOGY
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3. INTRODUCTION AND THEORY
The experiment is about determining the viscosity of the oil. Viscosity can be defined as a
measure of a fluid’s resistance to flow. It is one of the types of bulk property as well knew as
intensive property. It is a physical property that is not dependent on the size or mass of a sample.
The opposite of viscosity is fluidity which measures the ease of flow of a fluid. The internal friction
of a moving fluid is the factor that causes the flow’s resistance. When a fluid has a molecular
makeup with a lot of internal friction, it resists the motion and this condition stated as a fluid with
a large viscosity. For a fluid with a low viscosity value, the molecular makeup has a very little
friction when it is in motion and causes it to flow easier.
After that, the viscosity of liquids and gases are affected by temperature. However, the
effects of temperature are opposite to fluid and gases. This is because that upon heating, the
viscosity of a liquid decreases rapidly, whereas gases flow more sluggishly. This can be explained
through the intermolecular forces inside the fluid and gases. Intermolecular forces can be stated as
the forces which mediate interaction between molecules, including forces of attraction or repulsion
which act between molecules and other types of neighbouring particles such as atoms or ions. As
the temperature increases, the average speed of molecules in a liquid will also increase that causes
the average intermolecular forces decrease between the particles. However, as temperature
increase for gases, it causes the viscosity increase too. This is due to more effective collision
occurred between the gases particles which result in increase of intermolecular forces.
Furthermore, there are 2 different types of fluid characterizations which are the Newtonian
fluid and Non- Newtonian Fluid. The Newtonian fluid is when the ratio of shear stress to shear
rate or viscosity is constant. Meanwhile, for the Non- Newtonian fluid, viscosity of the fluid is
not constant. The examples for Newtonian fluid are water, light and oil while Non-Newtonian fluid
such as drilling mud and colloids. Shear Stress (t) is a measure of the force of friction from a fluid
acting on a body in the path of that fluid. Then, shear rate is the rate of change of velocity at which
one layer of fluid passes over an adjacent layer.
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PETROCHEMICALS & PETROLEUM REFINING TECHNOLOGY
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Figure 1: Shear Stress versus Shear Velocity
The experiment was conducted by using the Saybolt Viscometer. The material used was
only lube oil but with different temperature of Saybolt Viscometer Bath which were 40o C, 50o C
and 60 o C. After that, the time taken for the lube oil to flow out from the Saybolt Viscometer Bath
was recorded for each temperature. Each temperature was conducted 3 times to obtain the average
time taken. Based on the theory that had been explained earlier, the expected result is that the time
taken for the higher temperature of the lube oil is shorter than the lower temperature. This is
because the lube oil with higher temperature will has lower viscosity value rather than the low
temperature one.
Figure 2: Saybolt Viscometer
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PETROCHEMICALS & PETROLEUM REFINING TECHNOLOGY
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4. RESULT AND DISCUSSION
Table 1: Data Collection of Weight at Various Temperature
5.
First trial
Second trial
Third trial
Weight (g)
A
B
C
A
B
C
A
B
C
Temperatu
re
(°C)
40°C
58.02
101.99
101.36
58.81
103.71
103.53
58.84
103.80
103.65
50°C
58.83
105.06
104.92
58.88
104.51
104.24
58.86
104.06
103.99
60°C
58.84
103.96
103.71
58.82
103.42
103.45
58.81
103.37
103.18
A – Weight of empty flask.
B – Weight of flask with fluid, before pour into Saybolt Viscometer Bath.
C - Weight of flask with fluid, after pour into Saybolt Viscometer Bath.
Table 2: Time Responding Towards Different Temperature
Time (s)
Temperature
(°C)
First trial
Second trial
Third trial
Average
40°C
46.0
48.0
49.0
47.7
50°C
39.5
38.3
36.5
38.1
60°C
31.6
30.0
29.8
30.5
Determination of viscosity of oil is about an experiment that has objectives which are to
study the viscosity of fluid which is lubricant oil and to determine the dynamic viscosity of
lubricant oil at various temperatures. In the first place, there are two types of fluid characterizations
which are Newtonian and Non-Newtonian. Newtonian fluids follow Newton’s law of viscous
resistance and possess a constant viscosity while non-Newtonian fluids deviate from Newton’s
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PETROCHEMICALS & PETROLEUM REFINING TECHNOLOGY
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law of viscosity and exhibit variable viscosity. For the Newtonian fluid, the shear stress τ is linearly
related to the shear rate by Newton’s law of viscosity (Bird et al., 1960) as τ = μ
𝒅𝒖
𝒅𝒚
where the
coefficient μ is defined as dynamic viscosity of the fluid. In contrast with classical fluid mechanics
developed for Newtonian fluids, the theory of non-Newtonian fluid dynamics whose flow behavior
of stress and shear rate cannot be characterized by Newton’s law of viscosity (Skelland, 1967;
Bohme, 1987; Astarita and Marmcci, 1974; and Crochet et al., 1984). The non-Newtonian fluid is
characterized by not having a unique value for viscosity. That is, the relationship stress rate / shear
rate is not constant. The viscosity of these fluids will depend on the shear rate applied. To highlight,
there are several types of non-Newtonian fluid behavior that we can observe. The most common
one is pseudo plastic fluids. These are fluids like paints and emulsions where’s decrease in
viscosity as the shear rate increases. Next, dilatant fluids. These fluids are increase in viscosity as
the shear rate increases. The last one is plastic fluids. These fluids will behave like solids under
static conditions which will start to flow only when certain amount of pressure is applied.
Figure 1: Newtonian fluid graph
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PETROCHEMICALS & PETROLEUM REFINING TECHNOLOGY
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Figure 2: Non-Newtonian fluid graph
As a matter of fact, viscosity is a quantity that describes a fluid’s resistance to flow. A fluid
with high viscosity resists motion while fluid with low viscosity flows easily. For instance, more
viscous substances such as syrup and honey, take longer to pour than less viscous substances, such
as water. In the oil industry, viscosity is measured most commonly by dynamic viscosity and
reported in a unit called centipoise (cP). Dynamic viscosity or absolute viscosity is obtained by
dividing the shear stress by the rate of shear strain. To be added, the viscosity of most fluids is
only affected by temperature where it decreases with increasing temperature and increases with
decreased temperature, as revealed by Isaac Newton. This can be seen from result obtained which
viscosity decreases as temperature increases where the temperature of 40°C gives 0.93 cP, 50°C
displays 1.19 cP and lastly, 60°C shows 1.46 cP of viscosity. All these values are exactly followed
Newton’s formula, thus, this experiment is succeeded. In short, the higher the temperature is, the
lower a substance's viscosity is. Similarly, this theory explains conditions why an oil will flow
much more easily in summer at a temperature of 25°C than it will flow in winter at -25°C. In
addition to this, the viscosity concept arises when a layer of fluid is made to move in relation to
another layer. Hence, the greater the internal friction, the greater the stress (force per unit area)
required to promote the movement.
Subsequently, viscosity varies with temperature, generally decreased as temperature is
increased. Therefore, the relationship between temperature and viscosity is inversely proportional
for all substances. This condition occurs because the increased kinetic motion at higher
temperatures promotes the breaking of intermolecular bonds between adjacent layers. When a
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PETROCHEMICALS & PETROLEUM REFINING TECHNOLOGY
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liquid heat up, the molecules become excited and begin to move. The energy of this movement is
enough to overcome the forces that bind the molecules together, allowing the liquid to become
more fluid thus decreasing its viscosity. Based on this point, the changes in temperature always
affects the viscosity which it depends on the substance just how much it is influenced by a
temperature change.
To add to that, increases in temperature also resulted in time taken for lubricant oil to flow
out from the viscometer bath. Obviously, the lower temperature takes much longer time to flow as
can be seen in table 2 which time taken for 40°C gives 47.7 seconds, 50°C shows 38.1 seconds
and last one is 60°C displays 30.5 seconds. These outcomes can be related with fluid behavior
when temperature is changed. Above all, the experiment has been carried out is successfully
follows the theory and formula, invented by Isaac Newton.
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PETROCHEMICALS & PETROLEUM REFINING TECHNOLOGY
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6. CONCLUSION AND RECOMMENDATION
The experiment was conducted to study the viscosity of lubricant oil and determine its viscosity at
different temperature using Saybolt Viscometer Bath. The results obtained show that the viscosity
of lubricant oil vary at different temperature and behave like non-Newtonian fluids characteristics.
The temperature were set at range of 40°C to 60°C and volume of samples used were measured at
60ml each where the weight of fluid with flask before pour into Saybolt Viscometer Bath ranging
from 101.99g to 105.06g. The experiment were triplicate for each temperature and the average
time taken from first drop till last drop of lube oil came out after the stopper was plug out were
recorded. The longest time taken recorded is 47.7s at 40°C and the fastest time taken is 30.5s at
60°C while at 50°C, the time taken is 38.1s. From the data obtained, Dynamic Viscosity, µ is
calculated to see the viscosity of lube oil changing at different temperature. The value of dynamic
viscosity is within 2.138cP (high viscosity) to 3.377cP (low viscosity). This phenomenal is
explained base on Newton’s law of viscosity where the viscosity having no unique value, then the
relationship of stress rate / shear rate is not constant. Therefore, the lube oil is confirmed to be one
of non-Newtonian fluid which its viscosity change under applied force.
In recommendation part, the way to improve the experiment is by using the lubricant oil
that is stored inside air-tight container. This is to prevent the lube oil from contaminated by water
vapour in air. Contamination on lube oil can effect the its viscosity value. Besides that, controlling
the ambient temperature can greatly help in getting more accurate result of lube oil temperature in
which the temperature will effect the viscosity of oil. Last but not least, use graduated cylinder
instead of beaker or conical flask to measure the volume of lube oil used.
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PETROCHEMICALS & PETROLEUM REFINING TECHNOLOGY
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7. REFERENCES
1. Afrand, M., Najafabadi, K. N., & Akbari, M. (2016). Effects of temperature and solid
volume fraction on viscosity of SiO2-MWCNTs/SAE40 hybrid nanofluid as a coolant and
lubricant in heat engines. Applied Thermal Engineering, 102, 45-54.
2. Astarita, G. and Marmcci, G. (1974) : Principles of Non-Newtonian Fluid Mechanics
3. Barenblatt, G. E., Entov, B. M. and Rizhik, B. M. (1984) : Flow of Liquids and Gases in
Natural Formations, Nedra, Moscow.
4. J. Briant, J. Denis, G. Parc, Rheological Properties of Lubricants (Editions Technip, Paris,
1989)
5. Viscosity
of
liquids
and
astr.gsu.edu/Hbase/tables/viscosity.html)
9
gases
(http://hyperphysics.phy-
PETROCHEMICALS & PETROLEUM REFINING TECHNOLOGY
EXPERIMENT 3
8. APPENDIX
Calculation:
Assume: The fluid is been placed between 2 plates with distance 1 meter.
1Pa.s = 1 kg/m.s = 10 Poise = 1000 Centipoise
At 40°C:
The weight of flask with fluid after pour into Saybolt Viscometer Bath (C) is minus with Weight
of empty flask (A) to obtain the net weight.
The net weight for the first trial is 43.34g, second trial is 44.72g and third trial is 44.81g. Thus, the
average of net weight is 44.29 grams.
Dynamic viscosity, μ = 0.0443 kg/(1m)(47.7s)
= 9.287 x 10-4 kg/m.s
= 0.929 cP
At 50°C:
The weight of flask with fluid after pour into Saybolt Viscometer Bath (C) is minus with Weight
of empty flask (A) to obtain the net weight.
The net weight for the first trial is 46.09g, second trial is 45.36g and third trial is 45.13g. Thus, the
average of net weight is 45.53 grams.
Dynamic viscosity, μ = 0.0455 kg/(1m)(38.1s)
= 1.194 x 10-3 kg/m.s
= 1.194 cP
At 60°C:
The weight of flask with fluid after pour into Saybolt Viscometer Bath (C) is minus with Weight
of empty flask (A) to obtain the net weight.
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The net weight for the first trial is 44.87g, second trial is 44.63g and third trial is 44.37g. Thus, the
average of net weight is 44.62 grams.
Dynamic viscosity, μ = 0.0446 kg/(1m)(30.5s)
= 1.462 x 10-3 kg/m.s
= 1.462 cP
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