I am Deepak Kumar Jani, Pursuing PhD in Mechanical- Renewable energy. I have five years of teaching and two-year research experience. My subject area of interest are thermal engineering, automobile engineering, Mechanical measurement, Engineering Drawing, Fluid mechanics etc. I have filed a patent on "Hybridization of green energy for power production". I have published 17 research papers and two books.
I am glad to be part of Lambdageeks and would like to present some of my expertise in a simplistic way with the readers.
Apart from academics and research, I like wandering in nature, capturing nature and creating awareness about nature among people.
Also refer my You-tube Channel regarding “Invitation from Nature”
First of all we try to understand some terms useful in surface tension study. Liquid has properties like Cohesion. Cohesion is a property in which one molecule of liquid attracting another nearer molecule. Adhesion is a property in which the fluid molecules are attracted by solid surface contact with it. In short, we can say that the force between similar molecules is Cohesion and the force between dissimilar molecules is adhesion.
Let’s take an example.
If we drop mercury droplet on any surface, it tries to form in droplet because Cohesion is higher than the adhesion force. You will get a notice that Mercury droplet does not stick on the solid surface. The Mercury will try to stay away from the solid surface; it will not wet solid surface.
Now let’s take another example if we consider water particles fall on the surface. It will spread all over the concrete surface. It happens because of the adhesive force is more significant than Cohesive force in that case. The angle of contact between the liquid and the solid surface can describe wetting and non-wetting of the surface.
Refer the above figure the liquid gas and solid surface interface the liquid will where the solid surface when the angle is less than 90 degree (π/2). The wetting of the surface is increasing with decreasing the angle. If the angle is more than 90 degree, the liquid will not wet solid surface. The angle depends on the nature of the surface, types of liquid, solid surface, and cleanliness.
If we consider pure water comes in contact with the clean glass surface. The angle is 0 (zero) degree in that case. If we add impurities in the water: The angle will increase with the addition of impurities. As we have discussed the Mercury is non-wetting liquid, so the angle is lies from 130 to 150 degree.
Surface Tension
In liquid, the molecules are lying below the free surface. Every molecule of liquid is attracting to the molecule nearby. The molecular Cohesion force is the same in all direction. All the forces are the same in magnitude and opposite in direction. So, it will get cancel in liquid. It can be the reason for equilibrium in liquid. There is no resultant force present in the liquid.
Suppose we considered topmost molecules of liquid lying at a free surface as we know that there are no liquid molecules over them. So here, they are getting attracted by liquid molecules lying below them. This free surface liquid molecules will feel pull force interior of the liquid. This force acts like elastic force. Expended per unit area of the surface is called surface tension.
The Surface tension is denoted by Sigma (σ). Surface tension occurs at liquid-gas interface, liquid-liquid interface. The reason behind surface tension is an intermolecular attraction because of Cohesion.
Let’s understand it in depth by considering some practical examples,
You have seen liquid droplet of a spherical shape. The reason behind its spherical shape is surface tension.
You might be noticed that if we thoroughly pour water inside the glass. Even if the glass is filled, still we can add some water above the glass limit.
Suppose we will experiment with a thin glass tube on the water surface. We can quickly notice a capillary rise and depression inside a thin glass tube.
Birds can drink water from the water body due to surface tension.
Though pressure and the gravity force are higher than surface tension force, the surface tension force plays an important role when there are free surface and small dimensions. The unit of surface tension is N/m. The magnitude of surface tension depends on the following factors:
Type of liquid
Type of surrounding state gas, liquid or solid
The kinetic energy of molecules
Temperature of molecules
If we increase the temperature of substance like liquid, the intermolecular attraction is decreasing because the distance between molecules increases. The surface tension depends on intermolecular attraction (Cohesion). The value of surface tension for liquid is taken for air as a surrounding medium,
The surface tension for the air-water interface is 0.073 N/m.
The value of surface tension decreases with increasing temperature.
Capillary
If a narrow tube is dipped into the water, the water will rise inside the tube at a certain level. This type of tube is called a capillary tube, and this phenomenon is called the capillary effect. Another name of the capillary effect is the meniscus effect.
The capillary effect is due to surface tension force. The capillary rise and depression are happening because of cohesion and adhesion intermolecular attraction. The adhesion force between tube surface and a water molecule is higher than the Cohesion force between water molecules. Because of this, the water molecules can be observed in concave shape on the tube surface.
Weight of liquid rise or depress in small diameter tube
= ( Area of tube * Rise or fall ) * ( specific weight )
= (π/4 *d2*h) w
Verticle component of surface tension force
= σ cosθ * circumference
= σ cosθ * πd
If we consider equilibrium then upward force balances downward force, so the component of force is given as,
( π/4 * d2 *h * w ) = σ cosθ * πd
H = ( 4 σ cosθ/ wd )
Capillary tube
It can be observed from an angle that if the angle is between 0 to 90 degree, the value of h is positive, concave shape formation and capillary rise. If the angle is between 90 and 180 degrees, the h is negative, convex shape formation and capillary depression.
If the liquid is Mercury, then the effect is wholly turned opposite. In the case of Mercury, the Cohesion force is more significant than the adhesion force. Because of these, the Mercury molecules form convex shape on the tube surface.
The capillary effect is inversely proportional to the tube diameter. If you want to avoid the capillary effect, then you should not choose a small diameter tube. The minimum tube diameter is recommended for water, and Mercury is 6 mm. The surface inside the tube should be clean.
Evaporation
Evaporation is defined as a change of state from liquid to gaseous. Operation rate is dependent on the pressure and temperature condition of liquid.
Consider one example,
Suppose, the liquid is inside the closed vessel. In this vessel, the vapour molecules possess some pressure. It is called vapour pressure. If the vapour pressure starts decreasing then the molecule starts leaving from liquid surface very fast, this phenomenon is known as boiling.
In boiling, the bubbles are formed inside the liquid. This bubble travels near to higher pressure zone and collapses due to higher pressure. These collapsing bubbles are exerting significantly higher pressure around 100 atmospheric pressure. This pressure causes mechanical erosion on metal. Commonly, this effect is called Cavitation. It is required to study and design hydrodynamic machinery considering Cavitation.
Cavitation has both sides beneficial and non-beneficial. As we know that Cavitation cause erosion in metal, so it is non-beneficial
Some new research areas recently suggest that hydrodynamic Cavitation is useful for some chemical and wastewater treatment. So here, hydrodynamic Cavitation is a beneficial concept.
The vapour pressure of the liquid firmly depends on temperature: It increases with increase in temperature. At the temperature of 20°C, the vapour pressure of water is 0.235 N/cm2. The vapour pressure of Mercury is 1.72* 10-5 N/cm2.
If we want to avoid Cavitation in hydraulic machinery: We should not allow liquid pressure to fall below vapour pressure at the local temperature.
You might have thought many times that why the Mercury is used inside the thermometer and manometer. Why not other liquid?
Your answer is here; the Mercury has the lowest value of vapour pressure with high density. Its make Mercury suitable for use in thermometer and manometer.
Find the capillary effect in a tube of diameter 4mm. When the liquid is water
Questions & Answers
1) What is the difference between Cohesion and adhesion?
Cohesion is an attraction force of molecules between the same matter whereas adhesion is an attraction between molecules of different matter.
2) The Mercury is tried to stay away from the surface, why?
In Mercury, cohesion force is greater than adhesion force. Because of this, Mercury is called non-wetting liquid.
3) What is condition for wetting and non-wetting of liquid with the surface?
The liquid will wet the solid surface is less than 90 degree. If the angle is greater than 90 degree, then the liquid will not wet the solid surface.
4) Explain about surface tension
The liquid molecules on the free surface are getting attracted by liquid molecules lying below them. This free surface liquid molecules will feel pull force interior of the liquid. This force acts like elastic force. Expended per unit area of the surface is called surface tension. The Surface tension is denoted by Sigma (σ). Surface tension occurs at liquid-gas interface, liquid-liquid interface. The reason behind surface tension is an intermolecular attraction because of Cohesion.
5) Give some practical examples of surface tension.
You might be noticed that if we thoroughly pour water inside the glass. Even if the glass is filled, still we can add some water above the glass limit.
Suppose we will experiment with a thin glass tube on the water surface. We can easily notice a capillary rise and depression inside a thin glass tube.
Birds can drink water from the water body due to surface tension.
6) What is the unit of surface tension?
The unit of surface tension is N/m.
7) Give the value of surface tension for air-water and air-Mercury interface at standard pressure and temperature.
The surface tension for the air-water interface is 0.073 N/m.
The surface tension for the air-Mercury interface is 0.480 N/m.
8) What is the capillary effect?
If the narrow tube is dipped into the water, the water will rise inside the tube at a certain level. This type of tube is called a capillary tube, and this phenomenon is called the capillary effect.
9) Is there any relationship between the capillary effect and the surface tension? If yes, what?
Yes. The capillary effect is due to surface tension force. The capillary rise and depression are happening because of cohesion and adhesion intermolecular attraction.
10) Define: Boiling, Cavitation
Boiling: The vapour bubbles form inside the liquid due to temperature and pressure change. The boiling is a change of state) from liquid to vapour.
Cavitation: The formation of a vapour bubble inside machinery due to pressure of the liquid falls below the saturated vapour pressure.
Multiple Choice Questions
1) For wetting liquid, the angle of contact θ should be ________
(a) 0 (b) θ < π/2 (c) θ >π/2 (d) None
2) For non-wetting liquid, the angle of contact θ should be ________
(a) 0 (b) θ < π/2 (c) θ >π/2 (d) None
3) Surface tension value decrease with __________
(a) Constant pressure
(b) Increase in temperature
(c) Increase in pressure
(d) Decrease in temperature
4) If the value angle lies between 0 and 90, then what happens in capillary effect?
(a) h is positive with concave shape formation
(b) h is negative with concave shape formation
(c) h is negative with convex shape formation
(d) h is positive with convex shape formation
5) Why Mercury is used in thermometer and manometer?
(a) High vapour pressure and low density
(b) High vapour pressure and high density
(c) Low vapour pressure and low density
(d) Low vapour pressure and high density
6) What is approx. collapsing pressure of bubbles in cavitation phenomena?
(a) Around 20 atmospheric pressure
(b) Around 50 atmospheric pressure
(c) Around 75 atmospheric pressure
(d) Around 100 atmospheric pressure
7) What is the value of vapour pressure of water at 20° C temperature?
(a) 0.126 N/cm2
(b) 0.513 N/cm2
(c) 0.235 N/cm2
(d) 0.995 N/cm2
8) What is the value of vapour pressure of Mercury at 20° C temperature?
(a) 1.25* 10-5 N/cm2
(b)1.72* 10-5 N/cm2
(c) 1.5* 10-5 N/cm2
(d) 1.25 N/cm2
Conclusion
This article is presented you to understand the concept of surface tension, capillary effect, Cavitation, evaporation and its effects. Some of the practical examples is included in this article to represent it practically. The effort was made to make you correlate fluid mechanics concept with your day to day life.
To learn more on fluid mechanics, please click here.
The properties can describe the physical condition of any fluid. It is essential to understand various properties of fluid before analyzing the fluid flow problem. The properties can be defined as the physical characteristic which indicates its state
Properties of fluid are broadly divided into two parts
Intensive property: it is a property whose magnitude is not dependent on mass. For example, pressure, temperature, mass density, etc.
Extensive property: it is a property whose magnitude is dependent on mass. For example, weight volume, mass, etc.
Specific weight
Specific weight is defined as weight per unit volume
W=w/v
Here w is the weight of the fluid,
V is the volume of fluid.
As we know, the body’s weight is the force of the body to center of the earth.
It is expressed as the multiplication of the mass of the body and gravitational acceleration. The value of g is measured at sea level 9.8 m/s2
Weight is a force, so the unit of weight is Newton (N). The unit of volume is m3
Hence, the unit of specific weight is N/m3
The specific weight of water is 9810 N/m3 at standard pressure 760 mm of Mercury and temperature of 4°C.
Specificc weight of seawater is 10000 -10105 N/m3.
The higher value of specific weight in seawater is due to dissolved salt and solid particulate matter. The specific weight of Mercury is 13 times greater than water. The air has specific weight around 11.9 N/m3 (at temperature 15°C and standard atmospheric pressure).
Since the specific weight is dependent on gravitational acceleration, its value changes with gravity.
Density
Density, the symbol of density, is rho (?). The standard definition of density is mass per unit volume.
In other words, we can say that it is a matter (amount) of fluid storage in the given volume.
ρ=m/V
Here, m is mass of fluid, V indicates the volume of fluid,
We know that the unit of mass is in kg and the unit of volume is in m3
So, The unit of density is taken in kg/m3
The mass density of water 15.5°C is 1000 kg/m3
The mass density of air is 1.24 kg/m3 at standard temperature 20°C and normal atmospheric pressure.
I have one practical question for you. You are frequently visiting the petrol pump filling petrol in your bike or car. You have noticed that the density of petrol or diesel is indicated on display. Now understand my question carefully,
What is the requirement of indicating the density value of petrol and diesel? What happens if the density of petrol or diesel will get change?
Specific gravity is well-defined as the ratio of mass density or specific weight of the fluid to mass density or specific weight of the standard fluid.
Here, the standard fluid (sf) for liquid is water at 4°C and the standard fluid for gases is air at 0 °C.
As we can see, the specific gravity is the ratio of the same property, so the specific gravity is unitless.
There is no dimension of specific gravity..
The specific gravity of Mercury (Hg) is usually 13.6 times higher than water. It means that Mercury is 13.6 times heavier than water.
Specific volume
The specific volume is reciprocal of mass density
It can be defined as the ratio of volume and mass
v=V/m
Practically specific volume is a more useful incompressible fluid study.
The unit of specific volume is m3/kg.
Compressibility and bulk modulus
The study of fluid mechanics includes compressible and incompressible fluid.
Compressible fluid means it will get a contract when pressure is applied, and removal of pressure it will get expand.
Compressibility is the an essential property of the fluid. It is the ability of fluid to get change volume under pressure. The equation of the Coefficient of compressibility is given as,
Here, the dp change in applied pressure and dV is a volume change.
Here, the -ve sign indicates an increase in pressure results reduction in volume.The Coefficient of compressibility is symbolized by Βc.
Generally, In this measurement compressibility of fluid is represented by its bulk modulus of elasticity and the bulk modulus of elasticity is taken as reciprocal of the Coefficient of compressibility.
Viscosity
Viscosity can be defined as it is property of fluid by whic it exerts resistance to flow.
Practically if we take an example, fluid is flowing over any solid surface or planer surface. The velocity of the fluid is considered negligible (zero) at the solid surface boundary, and velocity is found increasing far away from the solid surface boundary. The fluid Layers offers resistance to each other. It is one type of friction between fluid layers.
Suppose we observe the velocity profile in the fluid layers. The velocity is found lesser near to the solid surface. The velocity is found greater at the outer layer, far from the solid surface boundary. This happens because of internal resistance, and it is known as viscous resistance. All real fluid possesses viscosity. As we know, that ideal fluid does not have viscosity. Some examples of highly viscous fluid are glycerine, tar, and molasses, etc.
The fluids with lower viscosity are air, water, petrol, etc.
Newton’s law of viscosity
Let’s, consider two adjacent layers at distance dy,
The top layer is flowing with velocity u+du. The top layer offers resistance to the lower layer with exerting force F. The lower layer also provides resistance to the top layer with equal and opposite force F. These two opposing forces generate shear resistance.
It is denoted by τ shear resistance. It is proportional to the velocity gradient.
If we remove the proportional limit, can we have to put one constant?
Here, the constant of proportionality or proportionality factor is μ
It is acknowledged as the Coefficient of viscosity. The value of Coefficient of viscosity is dependent on the type of surface and surface roughness.
This equation is widely known as Newton’s law of viscosity.
There is some observation based on this law. These observations are useful to study viscosity and velocity distribution.
Shear stress is the maximum velocity gradient is high.
When the velocity gradient is zero, the shear stress is also zero.
The value of shear stress is maximum at the boundary, and it will simultaneously decrease from the boundary.
The unit of viscosity can be formulated from Newton’s law of viscosity..
Here, N/m2 istaken as Pascal (Pa). Sometimes, the Coefficient of dynamic viscosity is taken in poise (P).
1 Poise = 0.1 Pa*s
Dynamic viscosity of water is 1 centipoise (cP)= 10-3 N s/m2
Dynamic viscosity of air is 0.0181 centipoise =0.0181 *10-3 N s/m2
Water is 55 times denser than air.
The given value is at standard temperature 20°C and atmospheric pressure.
Kinematic viscosity
The kinematics viscosity is well-defined as the ratio of dynamic viscosity and density.
The unit of kinematics viscosity is formulated as,
v=μ/ρ
As we know, that metric does not involve any force or energy, so the unit of kinematic viscosity only of length and time.
This unit is commonly known as stokes.
The kinematics viscosity of water is 10 raise to minus 6 meter square per second
The kinematic viscosity of air is 15
The value is at standard temperature of 20°C and atmospheric pressure.
The kinematics viscosity of air is 15 times higher than water.
Effect of temperature on viscosity
The effect of the temp. value of viscosity is different in liquid and gas.
If we consider the fluid is a liquid value of dynamic viscosity is decreasing with an increase in temperature
Suppose the fluid is gas; the value of viscosity is increasing with an increase in temperature.
Let’s see why
In liquid, the molecules are more closer as compare to gases.
Viscosity is act mainly due to molecular cohesion. The molecular cohesion is decreasing with increasing temperature.
Empirical relation is developed to explain the variation in viscosity due to temp.
For liquid:
Here, μ is the viscosity at the desired temperature t°C.
μ0 is the viscosity at 0°C
A, B are the constant, and their value is dependent on the used liquid.
For water μ0= 0.0179 poise, A= 0.03368, B= 0.000221
For gases:
Here, μt is the viscosity at desired temperature t°C.
μ0 is the viscosity at 0°C
α,β are the constant and its value is dependent on used gas
For air. μ0=1.7*10-5 Ns/m2, α=0.56*10-7, β= 0.1189*10-9
Questions & Answers
What is an intensive property?
It is the property of fluid whose magnitude is not dependent on mass or matter.
What is the weight of the body? Is it one type of force?
Yes, Weight is force. The weight of the body is the force of the body to the center of the earth.
Why is specific gravity unitless?
Specific gravity is the ratio of density of the fluid to density of the standard fluid. It means that ratio of the similar types. So there is no unit of specific gravity.
Which type of study requires the use of specific volume?
The study of compressible fluid requires the use of specific volume property.
What is compressibility?
Compressibility is the important property of fluid. It is ability of fluid to get change volume under pressure.
What is meaning of negative sign in the equation of compressibility?
The negative sign indicates increase in pressure results decrease in volume.
Enlist the observation based on newton’s law of viscosity.
Shear stress is maximum velocity gradient is high
When the velocity gradient is zero the shear stress is also zero
Value of shear stress is maximum at the boundary, and it will simultaneously decrease from the boundary.
Define kinematic viscosity. Why is the unit only include length and time dimensions?
The kinematics viscosity is represented as the ration of dynamic viscosity and density. We know that kinematic does not involve any force or energy, so the unit of kinematic viscosity only of length and time.
What is the effect of temp. on gaseous fluid?
If the fluid is gaseous, then the value of viscosity is increasing with an increase in temperature.
Give some examples of highly viscous fluid.
Examples of highly viscous fluid are glycerin, tar, and molasses, etc.
What are the values of constants in correlation for “effect of temperature on viscosity of gases ?
μ0 is the viscosity at 0°C
α,β are the constant and its value is dependent on used gas
For air. μ0=1.7*10-5 Ns/m2, α=0.56*10-7, β= 0.1189*10-9
Multiple Choice Questions
Which one of the following is extensive property?
a) Pressure b) Mass density c) Volume d) Temperature
Give the unit of specific weight.
a) N/m b) N/m2 c) N/m3 d) m/N
What is the value of specific weight of seawater (at standard condition)?
a) 10000 -10105 N/m3 b) 20000 -20105 N/m3 c) 1000 -1105 N/m3 d) None of above
How many times is Mercury heavier than water?
a) 11 b) 12 c) 13 d) 14
What is the density of water at 15.5°C in kg/m3
a) 994 b) 1000 c) 1500 d) 846
The specific gravity is ratio of mass density of fluid to mass density of_______
a) Compressible fluid b) Incompressible fluid c) Standard fluid d) None
The specific volume is reciprocal of__________
a) Specific weight b) Viscosity c) Mass density d) Specific gravity
The bulk modulus of elasticity is reciprocal of___________
a) Coefficient of viscosity b) Coefficient of performance c) Coefficient of compressibility d) None
Viscosity can be defined as resistance to ________
a) Fluid flow b) Current flow c) Temperature flow d) Pressure
What is the unit of kinematic viscosity?
a) N/m b) m/s c) m3/s d) m2/s
If fluid is liquid then the value of dynamic viscosity will ________ with increase in temperature of liquid.
a) Increase b) Decrease c) be constant d) None of this
The molecular cohesion is decreasing with________ temperature.
a) Increase b) Decrease c) Remain constant d) None
Conclusion
This article is the concept of various properties and their relation. The properties like specific weight, mass density, specific gravity and specific volume are defined with the unit. The concept of viscosity and newton’s law of viscosity are described in detail with its equations. The most important phenomenon, the effect of temperature on the fluid’s viscosity, is discussed to make the concept easier to understand.
To learn more on fluid mechanics, please click here
The fluid mechanics can be elaborated as the study of fluid and fluid systems for their physical behaviour, governing laws, actions of different energies and different flow pattern.
The fluid is sub-divided into two types :
Liquid
Gas
The fluid mechanics is the subject of engineering which will be useful in many engineering discipline. The subject of fluid mechanic is important in mechanical engineering, civil engineering, chemical engineering and environment engineering etc.
Even the study of geology, geophysics, ocean and nano science also requires some knowledge of fluid mechanics and fluid dynamics.
It is interesting for you that some basic laws of fluid mechanics is involved in primary and secondary education, so it can be expected that it is familiar subject for you.
What are the fluid mechanics branches?
There are three branches of fluid mechanics based on forces and energy.
Hydrostatic:
The hydrostatics can be defined as fluid mechanics studying when the fluid or fluid element at rest. It means there is no fluid flow. There are no shearing stresses.
We can take an example of fluid at rest like a dam, pond etc.
Hydro static structure dam
The dam is very known example of hydrostatic branch. In holidays you might have visited some famous dam near you.
Kinematics:
The kinematics is the study of fluid mechanics about fluid motions like translation, rotary or deformation. Remember-> There is no consideration of forces and energy acting on fluid (Fluid in motion) in this study.
Here, the fluid is flowing so we can take example of flowing fluid in river, canal etc.
Dynamics:
The fluid dynamics is a complete study of flowing fluid. It studies velocity, acceleration, forces and energies acts on the fluid in motion.
Here, the study of flowing fluid (Fluid in motion) is carried out by considering forces and energy acts on it. The example of fluid dynamic are fuel flow inside diesel fuel injector, liquid flow inside pump, fluid flow inside turbine etc.
Fluid flow | What is fluid flow?
When gas or liquid is travelling or moving fluid from one point (destination) to another point, we can call it fluid flow.
Let’s understand in another word, the trend of continuous deformation of fluid is known as fluidity. The action of this continuous deformation is known as fluid flow.
For example flow of wind, flow in the river, waves in the sea, liquid flow in pipelines etc.
Classification of fluid
In common term, there are two types of fluid as given below,
Ideal fluid
Real fluid
What is the ideal fluid?
First, keep it in mind “there is no existence of ideal fluid in nature and it is imaginary fluid”. In practical purpose, we are considering water and air as an ideal fluid for many studies because of its lower viscosity.
The water is incompressible, so it is closer to an ideal fluid as compared to air.
Ideal fluid possess the following characteristics,
The ideal fluid possesses no viscosity. It means that the friction does not exist in the fluid. The ideal fluid is our imagination of standard fluid with superior characteristics. In nature, there is always frictional resistance whenever any motion exists.
What is real fluid?
The all fluid in nature can be considered as real. Let’s see why?
It possesses most of the practical characteristics,
Viscous
Compressible
Friction
Surface tension
Principles of fluid dynamics
Some of the basics principles of fluid dynamics are enlisted below for your information. The study of each principle in detail with our next articles will take you in-depth of fluid dynamics.
These principles are helpful since many of the approaches and techniques of analysis used in fluid mechanics problems. It will be well understood when you come across real problems on fluid mechanics.
Fluid Mechanic applications
The fluid mechanics subject encircles numerous applications in domestic as well as industrial. Some of the applications are enlisted below,
The water distribution channel network and pipelines in domestic and industrial.
The hydraulics machinery and hydraulic structures are designed based on fluid mechanics. Hydraulics Machinery: Turbines, pumps, valves, fluid couplings, actuators etc.
Cross sectional view of Centrifugal Pump [Image Credit]
Hydraulic structures: Canal, dams, weirs, overhead tanks etc.
The fundamental of fluid dynamics can be used to design supersonic aircraft, missiles, gas turbine, rocket engines, torpedo, submarine etc.
The power plants like hydroelectric power, thermal (steam) power, gas turbine power uses fluid mechanics.
Some of the scientific subjects like oceanography, meteorology, geology etc. also require fluid dynamics.
The pneumatics and hydraulic various fluid control devices
Even if we consider blood flowing inside the human vein possess fluid dynamics
In nature, there are so many processes governed by fluid mechanics and fluid dynamics laws. Example: Rise of groundwater to top of the tree, rainwater cycle, wind flow and waves, ocean waves, weather patterns etc.
Let’s understand some practical applications of fluid dynamics, which will become very familiar with you.
You might have your automobile vehicle bike or car. You know that air is infiltrated inside vehicle tyres with pressure, so it possesses pressure laws.
Secondly, the shock absorber is filled with oil which absorbs jerk or shock. The oil will get pressurized and provide cushioning to your vehicle. There numerous day to day applications in your life that is totally or partially governed by fluid mechanics or dynamics.
Units and Dimensions
Since our subject is fluid mechanics, we will study a variety of fluid characteristics; it is a requirement to follow a system for indicating these attributes, both qualitatively and quantitatively.
The qualitative aspect describes to find the nature, or type, of the characteristics like length, time, stress, temperature, velocity and pressure on the next side the quantitative aspect indicates a value measure of the attributes.
A dimension can be defined as a description of measurable quantities or attributes of an object such as mass, length, temperature, pressure, time etc.
The understanding of unit can be considered as the standard for measuring the dimension or quality.
To understand the difference between units and dimensions, let’s take an example of the distance between Mumbai and Goa.
The term length is used to describe the qualitative concept of physical quantity.
The term unit indicates the magnitude of the distance between Mumbai and Goa in our example. This distance can be expressed in meter, kilometre or miles.
There are four fundamentals dimensions used in the physical dimensioning system. In the SI (standard international) system, the dimensions are mass, length, time and temperature. Let’s understand how it works?
International System (SI). In 1960, the 11th General Conference organised on Weights and Measures, the international organization responsible for managing precise, systematic standards of measurements, properly accepted the International System of Units as the international standard. This system, generally termed SI, has been broadly accepted worldwide and is broadly used.
Mass (M)
Kilogram
kg
Length (L)
Meter
m
Time (T)
Second
s
Temperature (K)
Kelvin
K
These are the fundamental units of the SI system. Other all the units of any physical properties can be derived based on these four units. Let’s take some example to understand it better way.
Work
You have heard about work. The unit of work is Joule. Now we expand its unit.
In other words, it is an energy transfer of any object when it moved from one place to another place. The force can be positive or negative.
Work = Force * Distance
The newton (N) is a unit of force, and the unit meter is a unit of distance. So the unit of work,
Unit of work = Newton* meter =N*m =Joule (J)
Density
The formula of density is given as below.
Density = mass per unit volume
Here, the unit of mass is kg, the unit of volume is m3.
The unit of density is kg/m3
The density of water is considered 1000 or 997 kg/m3. The density of air is 1.225 kg/m3
Its means that water is considered standard dense and it is heavier than much other liquid. The air is significantly lighter, and it is a highly compressible fluid.
Power
The definition of power is given as the ability of doing work in unit time. Or we can say work done per unit time.
Power = Work done per unit time.
The unit of work is Joule (J) and the unit of time is second (s).
The unit of power is derived as J/s (Joule/second). The unit Joule/second is in general known as watt (w).
Questions and Answers
What are types of fluid according to state?
According to the state, there are two types of fluid.
Liquid
Gas
Give the name of fluid mechanics branches.
Hydrostatics
Fluid kinematics
Fluid dynamics
What is real fluid?
It possesses most of the practical characteristics,
Viscous
Compressible
Friction
Surface tension
Define: Dimension and unit
A dimension can be defined as a description of measurable quantities or attributes of an object such as mass, length, temperature, pressure, time etc.
The understanding of unit can be considered as the standard for measuring the dimension or quality.
Give four fundamental dimensions of SI (Standard International).
Mass (M)
Length (L)
Time (T)
Temperature (K)
What is SI (Standard International) System?
International System (SI). In 1960 the 11th General Conference organized on Weights and Measures, the international organization responsible for managing precise, systematic standards of measurements, properly accepted the International System of Units as the international standard.
Enlist three applications of fluid mechanics.
Design supersonic aircrafts
The water distribution channel network
The pneumatics and hydraulic various fluid control devices
What are the pressure measuring instruments?
Bourdon tube pressure gauge
Vacuum gauge
Manometer
Give any three names of fluid mechanic principles.
Bernoulli’s theorem
Rayleigh’s method and Buckingham pi-theorem
Archimede’s principle
MCQ on Articles
Choose the fluid mechanics branch; the study includes force and energy acts on moving fluid?
This article is helpful to get the basic knowledge about fluid mechanics fundamental. The article includes an understanding of some basics terms like hydrostatics, fluid kinematics and fluid dynamics. The list of various fluid mechanics principle and applications are provided to get an idea about subject and future learning topics. In last, the dimension and unit definitions are given with detailed examples.
This article teaches you to visualize and remember applications of fluid mechanics in your day to day life. You have to collaborate with applications with fluid mechanic’s principles.
More topic related to fluid mechanics, please click here.
Nanofluids have emerged as a promising solution for enhancing heat transfer in various applications. By incorporating nanoparticles into conventional heat transfer fluids, nanofluids exhibit improved thermal properties that can significantly enhance heat transfer efficiency. In this section, we will explore the definition and composition of nanofluids, as well as their application in heat transfer enhancement.
Definition and Composition of Nanofluids
Nanofluids can be defined as suspensions of nanoscale particles in a base fluid, typically water or oil. These nanoparticles, which are usually metallic or non-metallic, are dispersed uniformly in the base fluid, creating a stable colloidal mixture. The size of the nanoparticles used in nanofluids typically ranges from 1 to 100 nanometers.
The composition of nanofluids plays a crucial role in determining their heat transfer properties. The choice of nanoparticles and base fluid depends on the specific application requirements. Metallic nanoparticles, such as copper, aluminum, and silver, are commonly used due to their high thermal conductivity. Non-metallic nanoparticles, such as carbon nanotubes and graphene, are also gaining attention for their unique properties.
To ensure the stability of nanofluids, various techniques are employed to prevent particle agglomeration. Surface modification of nanoparticles, such as coating them with surfactants or polymers, helps to maintain the stability and prevent sedimentation. Additionally, ultrasonication and magnetic stirring are used during the synthesis process to disperse the nanoparticles evenly in the base fluid.
Application of Nanofluids in Heat Transfer Enhancement
The use of nanofluids in heat transfer applications has gained significant interest due to their ability to enhance thermal conductivity and convective heat transfer. The incorporation of nanoparticles into the base fluid increases the effective thermal conductivity of the nanofluid, resulting in improved heat transfer rates.
Nanofluids find applications in various heat transfer systems, including heat exchangers, electronics cooling, and solar thermal systems. In heat exchangers, nanofluids can enhance the overall heat transfer coefficient, leading to improved system performance. The increased heat transfer efficiency of nanofluids allows for smaller heat exchanger designs, reducing space and cost requirements.
In electronics cooling, nanofluids offer a solution to dissipate heat generated by electronic devices more effectively. By using nanofluids as coolants, the heat transfer rate from the electronic components to the cooling system can be significantly improved, ensuring optimal device performance and reliability.
Furthermore, nanofluids have shown promise in solar thermal systems, where they can enhance the absorption and transfer of solar energy. The improved heat transfer properties of nanofluids enable more efficient conversion of solar radiation into usable heat, making them a potential solution for sustainable energy applications.
Heat Transfer Enhancement in Nanofluids
Overview of Heat Transfer Enhancement in Nanofluids
Nanofluids, a combination of base fluids and nanoparticles, have gained significant attention in recent years due to their ability to enhance heat transfer. These nanofluids exhibit improved thermal properties compared to traditional fluids, making them a promising solution for various heat transfer applications. In this section, we will explore the concept of heat transfer enhancement in nanofluids and delve into the underlying mechanisms that contribute to their superior performance.
Nanofluids are engineered by dispersing metallic or non-metallic nanoparticles, typically in the range of 1-100 nanometers, into a base fluid such as water, oil, or ethylene glycol. The addition of nanoparticles alters the thermal conductivity, viscosity, and convective heat transfer characteristics of the base fluid, leading to enhanced heat transfer rates.
One of the key factors that contribute to the improved heat transfer in nanofluids is the significantly higher thermal conductivity of nanoparticles compared to the base fluid. The presence of nanoparticles in the fluid creates a conductive network that facilitates the transfer of heat. This increased thermal conductivity allows for more efficient heat dissipation, resulting in enhanced heat transfer rates.
Importance of Thermal Conductivity in Nanofluids
Thermal conductivity plays a crucial role in determining the heat transfer performance of nanofluids. The ability of a material to conduct heat is quantified by its thermal conductivity coefficient. In the case of nanofluids, the thermal conductivity is significantly enhanced due to the presence of nanoparticles.
The high thermal conductivity of nanoparticles allows for better heat conduction within the nanofluid, enabling faster heat transfer. This property is particularly beneficial in applications where heat dissipation is critical, such as heat exchangers or electronic cooling systems. By utilizing nanofluids with enhanced thermal conductivity, the overall efficiency of these systems can be greatly improved.
Moreover, the increased thermal conductivity of nanofluids also leads to a higher heat transfer coefficient. The heat transfer coefficient represents the rate at which heat is transferred between a solid surface and a fluid. In the case of nanofluids, the higher thermal conductivity results in a larger heat transfer coefficient, indicating a more efficient heat transfer process.
In addition to thermal conductivity, the convective heat transfer characteristics of nanofluids are also influenced by the presence of nanoparticles. The nanoparticles alter the fluid dynamics within the nanofluid, promoting better heat transfer through convection. This enhanced convective heat transfer further contributes to the overall heat transfer enhancement in nanofluids.
Methods to Increase Heat Transfer
Heat transfer is a crucial process in various industrial applications, ranging from cooling electronic devices to optimizing the efficiency of power plants. Enhancing heat transfer is essential to improve the overall performance and effectiveness of these systems. In recent years, researchers have been exploring innovative methods to increase heat transfer, including the use of nanofluids. Nanofluids, which are a combination of nanoparticles and base fluids, have shown great potential in enhancing heat transfer due to their unique thermal properties. In this section, we will explore different ways to enhance heat transfer and delve into the fascinating world of nanofluid technology.
Before we delve into the ways to enhance heat transfer, let’s first understand the fundamental equation that governs heat transfer. The heat transfer equation, also known as Fourier’s law, describes the rate at which heat is transferred through a material. It states that the heat transfer rate is directly proportional to the temperature gradient and the thermal conductivity of the material, and inversely proportional to the thickness of the material. Mathematically, it can be represented as:
q = -k * A * (dT/dx)
Where:
– q is the heat transfer rate
– k is the thermal conductivity of the material
– A is the cross-sectional area through which heat is transferred
– dT/dx is the temperature gradient across the material
Understanding this equation is crucial as it forms the basis for exploring methods to enhance heat transfer.
Ways to Enhance Heat Transfer
Now that we have a basic understanding of the heat transfer equation, let’s explore some ways to enhance heat transfer. These methods can be broadly categorized into two main approaches: improving thermal conductivity and optimizing convective heat transfer.
Improving Thermal Conductivity
One way to enhance heat transfer is by improving the thermal conductivity of the working fluid. Thermal conductivity refers to the ability of a material to conduct heat. By incorporating high thermal conductivity nanomaterials, such as metallic or carbon-based nanoparticles, into the base fluid, the overall thermal conductivity of the nanofluid can be significantly enhanced. These nanoparticles, due to their small size and large surface area, facilitate efficient heat transfer by increasing the number of heat transfer pathways within the fluid.
Optimizing Convective Heat Transfer
Convective heat transfer, which occurs when a fluid flows over a solid surface, is another area where heat transfer enhancement can be achieved. By using nanofluids, researchers have observed improvements in convective heat transfer due to the unique properties of nanoparticles. The presence of nanoparticles in the fluid alters its flow behavior, leading to enhanced heat transfer. The nanoparticles act as disruptors, breaking up the thermal boundary layer near the solid surface and promoting better heat transfer between the fluid and the surface.
To optimize convective heat transfer, researchers have explored various parameters, such as nanoparticle concentration, particle size, and flow velocity. By carefully tuning these parameters, it is possible to achieve significant improvements in heat transfer performance. Additionally, the use of advanced heat exchangers and fluid dynamics techniques can further enhance convective heat transfer in nanofluids.
Comparison of Various Nanofluids
Overview of Nanofluid Thermal Conductivity Dependence on Metallic Particle Properties
Nanofluids, which are colloidal suspensions of nanoparticles in a base fluid, have gained significant attention in recent years due to their potential for enhancing heat transfer in various applications. Metallic nanoparticles, such as copper, silver, and aluminum, are commonly used in nanofluids due to their high thermal conductivity and stability.
The thermal conductivity of nanofluids is influenced by several factors, including the properties of the metallic nanoparticles. The size, shape, and concentration of the nanoparticles play a crucial role in determining the thermal conductivity enhancement of the nanofluid.
Size: The size of the nanoparticles affects the thermal conductivity enhancement of the nanofluid. Smaller nanoparticles have a larger surface area-to-volume ratio, which promotes better heat transfer. As the particle size decreases, the phonon scattering at the nanoparticle-fluid interface increases, leading to enhanced thermal conductivity.
Shape: The shape of the nanoparticles also impacts the thermal conductivity of the nanofluid. Nanoparticles with a higher aspect ratio, such as nanorods or nanowires, exhibit better thermal conductivity enhancement compared to spherical nanoparticles. The elongated shape provides a larger contact area, facilitating efficient heat transfer.
Concentration: The concentration of metallic nanoparticles in the nanofluid affects the thermal conductivity enhancement. As the nanoparticle concentration increases, the interparticle interactions and clustering can occur, leading to a decrease in thermal conductivity. However, at lower concentrations, the nanoparticles disperse more uniformly, resulting in enhanced thermal conductivity.
Comparison of Different Nanofluids for Heat Transfer Enhancement
Numerous studies have been conducted to compare the heat transfer enhancement capabilities of different nanofluids. These studies have focused on various factors, including the type of nanoparticles, base fluid, and experimental conditions. Let’s take a look at some of the key findings:
Metallic Nanoparticles: Nanofluids containing metallic nanoparticles, such as copper, silver, and aluminum, have shown significant heat transfer enhancement compared to pure base fluids. The high thermal conductivity of these metallic nanoparticles facilitates efficient heat transfer, making them suitable for applications in heat exchangers and cooling systems.
Carbon-Based Nanoparticles: Carbon-based nanoparticles, such as graphene and carbon nanotubes, have also demonstrated excellent heat transfer enhancement properties. These nanoparticles have high thermal conductivity and unique structural properties, enabling efficient heat dissipation. However, challenges related to dispersion and stability need to be addressed for practical applications.
Oxide Nanoparticles: Nanofluids containing oxide nanoparticles, such as alumina and titania, have been extensively studied for heat transfer enhancement. These nanoparticles offer good stability and have the potential to enhance convective heat transfer. However, their lower thermal conductivity compared to metallic nanoparticles limits their overall heat transfer enhancement capabilities.
Hybrid Nanofluids: Hybrid nanofluids, which combine different types of nanoparticles, have also been investigated for heat transfer enhancement. These nanofluids aim to leverage the unique properties of multiple nanoparticles to achieve enhanced heat transfer performance. However, further research is needed to optimize the nanoparticle combination and concentration for maximum heat transfer enhancement.
Applications of Nanofluids in Heat Transfer
Nanofluids, which are suspensions of nanoparticles in a base fluid, have gained significant attention in recent years due to their remarkable thermal properties. These unique fluids have found numerous applications in various heat transfer systems, ranging from electronic cooling to solar thermal devices. Let’s explore some of the key applications of nanofluids in heat transfer.
Use of Nanofluids in Electronic Cooling
Electronic devices generate a substantial amount of heat during operation, which can lead to performance degradation and even failure if not properly managed. Nanofluids offer a promising solution for efficient electronic cooling. Two commonly used techniques for electronic cooling are the vapor chamber and jet impingement methods.
Vapor Chamber
Vapor chambers are heat pipes that utilize the evaporation and condensation of a working fluid to transfer heat. By incorporating nanofluids as the working fluid, the heat transfer performance can be significantly enhanced. The high thermal conductivity of nanoparticles improves the overall heat transfer rate, allowing for more efficient cooling of electronic components.
Jet Impingement
Jet impingement cooling involves directing a high-velocity fluid jet onto the surface of a heated object. Nanofluids can be employed in this process to enhance convective heat transfer. The presence of nanoparticles in the fluid increases the heat transfer coefficient, resulting in improved cooling efficiency. This makes nanofluids an excellent choice for cooling high-power electronic devices.
Application of Nanofluids in Radiators for Engine Cooling
Efficient cooling is crucial for the proper functioning of internal combustion engines. Traditional coolants, such as water or ethylene glycol, can be enhanced by adding nanoparticles to form nanofluids. These nanofluids exhibit superior thermal conductivity compared to conventional coolants, leading to improved heat dissipation from the engine.
By utilizing nanofluids in radiators, the heat transfer rate can be significantly increased. This translates to better engine performance, reduced fuel consumption, and lower emissions. Moreover, nanofluids offer enhanced stability and reduced corrosion, making them an attractive option for engine cooling applications.
Utilization of Nanofluids in Solar Thermal Devices
Solar thermal devices, such as parabolic solar collectors, harness the energy from the sun to generate heat. Nanofluids can play a vital role in enhancing the efficiency of these devices. By incorporating nanoparticles into the heat transfer fluid, the thermal conductivity is improved, resulting in more effective heat absorption and transfer.
The use of nanofluids in solar thermal devices allows for higher operating temperatures and increased energy conversion efficiency. This, in turn, leads to improved performance and reduced costs in solar power generation. Nanofluids have the potential to revolutionize the field of solar energy by maximizing the utilization of available sunlight.
Nanofluid Application in Transformer Cooling
Transformers are essential components in electrical power systems, and efficient cooling is crucial to ensure their reliable operation. Nanofluids offer a promising solution for transformer cooling due to their excellent thermal properties. By using nanofluids as the cooling medium, the heat transfer rate can be significantly enhanced.
Nanofluids provide improved thermal conductivity and heat transfer coefficients compared to traditional cooling fluids. This allows for more efficient heat dissipation from the transformer, reducing the risk of overheating and extending its lifespan. The application of nanofluids in transformer cooling systems can lead to enhanced reliability and reduced maintenance costs.
Other Applications of Nanofluids in Cooling and Heat Transfer Systems
In addition to the aforementioned applications, nanofluids have found use in various other cooling and heat transfer systems. Some notable examples include:
Heat exchangers: Nanofluids can be employed in heat exchangers to enhance heat transfer efficiency and reduce energy consumption.
Fluid dynamics: Nanofluids have been studied extensively to understand their flow behavior and optimize their performance in different applications.
Nanotechnology: The field of nanotechnology has benefited greatly from the development of nanofluids, as they offer unique opportunities for heat transfer enhancement at the nanoscale.
Nanofluid synthesis: Researchers continue to explore new methods for synthesizing nanofluids with improved stability and enhanced thermal properties.
Nanofluid properties: The study of nanofluid properties, such as viscosity, density, and thermal conductivity, plays a crucial role in optimizing their performance in various heat transfer systems.
Feasibility and Future Scope of Nanofluids
Nanofluids, a suspension of nanoparticles in a base fluid, have gained significant attention in recent years due to their potential for enhancing heat transfer in various applications. In this section, we will explore the feasibility of nanofluids as thermal fluids, discuss their importance in increasing equipment efficiency, and highlight the future prospects and research opportunities in this exciting field.
Feasibility of Nanofluids as Thermal Fluids
Nanofluids offer several advantages over traditional heat transfer fluids. The addition of nanoparticles to the base fluid enhances its thermal conductivity, which is crucial for efficient heat transfer. The high surface area-to-volume ratio of nanoparticles allows for better heat dissipation, leading to improved thermal performance.
Moreover, nanofluids exhibit unique properties at the nanoscale, such as enhanced convective heat transfer and altered fluid dynamics. These properties make them suitable for a wide range of applications, including heat exchangers, cooling systems, and thermal management in electronic devices.
To ensure the feasibility of nanofluids, researchers have focused on studying their stability, flow characteristics, and thermal properties. Stability is a critical factor as nanoparticles tend to agglomerate, affecting the overall performance of the nanofluid. By employing suitable surfactants and dispersants, scientists have made significant progress in stabilizing nanofluids and preventing particle aggregation.
Importance of Nanofluids in Increasing Equipment Efficiency
The use of nanofluids can significantly enhance the efficiency of various equipment and systems. By improving heat transfer, nanofluids can reduce the energy consumption of heat exchangers, leading to cost savings and environmental benefits. The enhanced heat transfer coefficient and heat transfer rate of nanofluids ensure that heat is efficiently transferred between the solid surface and the fluid.
Additionally, the unique properties of nanofluids, such as their ability to alter fluid dynamics, enable the design of more compact and efficient heat exchangers. This, in turn, leads to space savings and increased performance in a wide range of applications, including automotive cooling systems, power plants, and electronic devices.
Future Prospects and Research Opportunities in Nanofluids
The field of nanofluids holds immense potential for future advancements and research opportunities. As nanotechnology continues to evolve, researchers are exploring novel nanomaterials and nanoparticles that can further enhance the thermal properties of nanofluids. By tailoring the size, shape, and composition of nanoparticles, scientists can optimize their heat transfer capabilities for specific applications.
Moreover, understanding the underlying heat transfer mechanisms in nanofluids is crucial for their successful implementation. Ongoing research aims to elucidate the fundamental mechanisms responsible for the enhanced heat transfer observed in nanofluids. This knowledge will enable the development of predictive models and simulations, facilitating the design and optimization of nanofluid-based systems.
Furthermore, the application of nanofluids extends beyond heat transfer enhancement. Researchers are exploring the use of nanofluids in areas such as energy storage, solar thermal systems, and biomedical applications. The versatility of nanofluids opens up new avenues for innovation and cross-disciplinary collaborations.
Frequently Asked Questions
1. How does nano heat transfer differ from traditional heat transfer?
Nano heat transfer refers to the study and application of heat transfer at the nanoscale, involving the transfer of heat between objects or systems at the nanometer level. Traditional heat transfer, on the other hand, deals with heat transfer at macroscopic scales. Nano heat transfer takes into account unique phenomena and properties that arise at the nanoscale, such as quantum effects and surface interactions.
2. What is heat transfer enhancement using nanofluids?
Heat transfer enhancement using nanofluids involves the incorporation of nanoparticles into conventional heat transfer fluids to improve their thermal properties. By adding nanoparticles, such as metal or oxide particles, to the base fluid, the thermal conductivity and convective heat transfer characteristics of the fluid can be enhanced, leading to improved heat transfer rates in various applications.
3. How can heat transfer be increased using nanofluids?
Heat transfer can be increased using nanofluids by exploiting the enhanced thermal conductivity and convective heat transfer properties of the nanoparticles suspended in the fluid. The nanoparticles facilitate better heat transfer by increasing the effective thermal conductivity of the fluid and promoting convective heat transfer through improved fluid dynamics. This results in higher heat transfer rates compared to conventional fluids.
4. What are the techniques for heat transfer enhancement using nanofluids?
There are several techniques for heat transfer enhancement using nanofluids, including altering the nanoparticle concentration, controlling the particle size and shape, optimizing the fluid flow conditions, and utilizing surface modifications to enhance the interaction between the nanoparticles and the fluid. These techniques aim to maximize the thermal properties and convective heat transfer characteristics of the nanofluid, leading to improved heat transfer rates.
5. How does nanotechnology contribute to heat transfer enhancement?
Nanotechnology plays a crucial role in heat transfer enhancement by enabling the synthesis and manipulation of nanomaterials and nanoparticles with unique thermal properties. Through nanotechnology, researchers can design and engineer nanofluids with enhanced thermal conductivity and convective heat transfer characteristics, thereby improving heat transfer rates in various applications, such as heat exchangers and thermal management systems.
6. What is the role of nanofluid flow in heat transfer enhancement?
Nanofluid flow plays a significant role in heat transfer enhancement as it affects the convective heat transfer characteristics of the fluid. By optimizing the flow conditions, such as flow rate, velocity, and turbulence, the interaction between the nanoparticles and the fluid can be maximized, leading to improved heat transfer rates. Proper understanding and control of nanofluid flow dynamics are essential for effective heat transfer enhancement.
7. How does nanofluid stability impact heat transfer enhancement?
Nanofluid stability is crucial for heat transfer enhancement as it ensures the uniform dispersion and suspension of nanoparticles in the base fluid. Stable nanofluids prevent particle agglomeration and sedimentation, which can hinder the convective heat transfer process. By maintaining nanofluid stability, the nanoparticles can effectively enhance the thermal conductivity and convective heat transfer properties of the fluid, leading to improved heat transfer rates.
8. What are the heat transfer mechanisms in nanofluids?
The heat transfer mechanisms in nanofluids involve three main processes: conduction, convection, and radiation. Conduction refers to the transfer of heat through direct particle-to-particle contact, while convection involves the transfer of heat through the movement of the nanofluid. Radiation, on the other hand, occurs when heat is transferred through electromagnetic waves. The combination of these mechanisms contributes to the overall heat transfer enhancement in nanofluids.
9. What are the applications of nanofluids in heat transfer?
Nanofluids find various applications in heat transfer, including heat exchangers, electronics cooling, solar thermal systems, and automotive cooling systems. The enhanced thermal properties and convective heat transfer characteristics of nanofluids make them suitable for improving heat transfer rates in these applications. Nanofluids offer potential benefits in terms of increased energy efficiency and improved thermal management.
10. How are nanofluids synthesized for heat transfer enhancement?
Nanofluids can be synthesized through various methods, including one-step and two-step processes. One-step synthesis involves directly dispersing nanoparticles into the base fluid, while two-step synthesis involves the separate synthesis of nanoparticles followed by their dispersion into the fluid. The choice of synthesis method depends on factors such as nanoparticle material, desired concentration, and stability requirements.
Following contents are explained in this articles:
Nanofluid definition | what is nanofluid?
What is base fluid?
How do you make a Nanofluid?
What is hybrid nanofluid?
Uses of nanofluid | applications of nanofluid
Types of nanofluid & Its Poperties
Nanofluid definition | What is nanofluid?
Nanofluid is fluid that consists of a base fluid with nanosized particles (1–100nm) suspended in it. Nano particles used in this type of studies are made of a metal or metal oxide, increase conduction and convection, allowing for more heat transfer. In the past few years, high-speed advancement in nanotechnology has made emerging of new generation coolants called nanofluid.
Let’s take example, check figure below. The CuO (metal oxide) nanoparticles are added to make nanofluid with a volume fraction of 0.25% CuO. The nanoparticle is dispersed in distilled water (base fluid). The surfactant sodium dodecyl sulfate (SDS) is added to the nanofluid for the stability of nanoparticles.
CuO Nanofluid
What is base fluid?
The nanoparticles are suspended in some ordinary liquid coolant like distilled water, ethylene glycol, oil, refrigerants, etc. This widely used ordinary coolant is known as base fluid.
You might have noticed while mechanic changing or pouring coolant in your car radiator. Do you remember its color? Yes, it’s green. That green colored fluid (coolant) is ethylene glycol.
Let’s know about base fluid oil. You might have noticed mechanic changing oil from your car or bike. It is lubrication and transmission system oil. This type of oil can be base fluid for nanofluid preparation.
How do you make a Nanofluid?
The preparation of nanofluid can be possible by following two widely used methods. It is prepared by dispersing nanoparticles in base fluid with a magnetic stirrer and sonicator, as shown in figure “Preparation of nanofluid : Sonicator”.
There are two types of stirrer used to disperse particles into basefluid, one is the magnetic and another is mechanical. The another lab instrument called ultrasonic sonicator is also required for proper dispersion.
Preparation of nanofluid : magnetic stirrerPreparation of nanofluid : Sonicator
Two-step method
The two-step procedure is the most widely used method for preparing nanofluid. The chemical and physical peocesses are used to produce dry powder of nanoparticles.
The powder of particles is added into the base fluid. The second step could be intensive magnetic force agitation or ultrasonic agitation. The two-step procedure is the economic procedure to produce nanofluid on bulk because the nano fluid requirements are raising with new applications.
Use of surfactant in nanofluid
The nanoparticles have large surface area and surface activity which lead to aggregate. The use of surfactant is convenient method to get good stability. However, the surfactants’ functionality under high temperatures is also a big issue, especially for high-temperature applications.
One-step method
Eastman suggested a one-step method of vapor condensation. It is used prepare Cu/ethylene glycol (EG) nanofluid to limit the agglomeration of nanoparticles.
The use of one-step preparation method avoid spreading the particles in the fluid. There are some function not needed in this method. This method eliminates drying of particles, storage of material, and spreading. Agglomeration is limited in one -step method. it also increases stability of nanofluid.
Vacuum method – SANSS
(full form Submerged -arc -nanoparticle -synthesis- system)
It is one of the preparation method of nanofluid with good efficiency. Different dielectric fluid are used in this method
The shape of nanoparticles are like different different type. The procedure avoids the undesired particle aggregation reasonably well. There are some disadvantages of this method. There is some reactant remain present in nanofluid.
What is a hybrid nanofluid?
A hybrid material is a combination of physical and chemical properties of two or more materials. The two or more nanoparticles are dispersed in a base fluid to achieve desired properties for individual applications. The making of nanofluid with two or more similar or different nanoparticles is popular as hybrid nanofluid. The work on hybrid nanofluid is not extensively done.
There are many experimental studies on hybrid nanofluid is still left to be done. The generally used hybrid nanofluids are Al2O3/Cu, Al2O3/CNT, Cu/TiO2, CNT/Fe3O4, etc.
The hybrid nanofluid is a new research area for thermal engineering researcher to obtain enhanced cooling system.
Usage of nanofluid
Nanofluid can be utilized for various different applications. These uses not affecting energy transfer thoroughly, they may be reduce the basic need for conventional fuel, electrical energy, or gas. Let’s read some important application of nanofluids
Electronic devices cooling
The research going on the electronics suggests that the use of nanofluid can perform superior heat transfer. The vapour chamber is utilizing nanofluid in it for better heat transfer.
Jacket-water fluid in electricity generator
The management of machinery space is main problem in all automobile vehicle. The size of component (cooling) can be reduced only if we improve heat transfer performance of parts. The nanofluid is the one of the option to improve performance of part and develop compactness.
Solar energy – thermal energy system
To absorb solar radiation, the working fluid is passes through solar thermal energy system. The energy absorbed by fluid is sent to heat exchanger for other purposes.The solar energy absorbed by working fluid is generally transferred to the heat exchanger for other applications.
Cooling oil in Transformer
The transformer is power transmission electrical equipment. The generated heat in transformer is absorbed by oil. If we add nanoparticle in cooling oil. The performance of transformer can be improved.
Other usage of nanofluid in the field of heat transfer enhancement:
Refrigeration process
The refrigeration process is working on different thermodynamic cycles. The working fluid in this process is refrigerant. The thermal properties of some refrigerant can be improved by use of nanoparticle.
Cooling system of nuclear energy
The huge amount of heat is produced in the nuclear fission. It is required to arrange proper cooling to system. The nano fluid is advance fluid which can be utilized in nuclear cooling system.
Types of nanofluid
The types of nanofluid are dependent on the use of different types of nanoparticles and base fluids. There are three types of nanoparticles, like pure metal, metal oxide, and carbide-based nanoparticles. These particles are dispersed in various choices of base fluids like water, water/ethylene glycol, oil, ethylene glycol, etc.
Pure Metal
Metal oxides
Carbide
Al
Al2O3
Diamond
Cu
CuO
Graphite
Fe
Fe2O3, Fe3O4
Single wall nanotube
Ag
Ag2O
Multiwall nanotubes
Zn
ZnO
Ti
TiO2
Properties of nanofluid
Thermal conductivity is one of the vital property related to heat transfer for nanofluid. It is high thermal conductivity compared to standard cooling liquid, it is an essential characteristic for many applications. Use of copper nanoparticles with ethylene glycol results in an increase in thermal conductivity by 40% compared to the base fluid.
All processes indicates that thermal conductivity basic for proper cooling system in any devices. In the cooling system, a large surface area and high thermal conductivity are attributed to this heat transfer improvement.
The ratio of surface area and volume is main criteria for thermal conductivity improvement. This ration can be increased by using small size nanoparticles. The thermal conductivity is raised by using higher concentration of the particles.
The properties like density, viscosity, specific heat, thermal conductivity are well known for base fluid. The properties of nanofluid can be calculated theoretically by correlations suggested by various researchers. These properties also can be measured with multiple instruments experimentally in the lab.
The density of nanofluid can be calculated using correlation as
Where ρpand ρbfare the nanoparticles’ densities and base fluid, respectively, and фis the volume concentration (% w/w) of nanoparticles dispersed in the base fluid. As per the idea of the strong fluid combination, the specific heat of nanofluid is given by the accompanying:
Where cppand cpbf, are the specific heat of the nanoparticles and base fluid, respectively. The viscosity of nanofluid can be obtained from the following equation:
Credit Einstein 1906
a is constant in viscosity equation and its value is 14.4150 to calculate viscosity. This formula is basically given for Brownian motion of particle in fluid. One well-known formula for computing the thermal conductivity of nanofluid is the Kang model which is expressed in the following form :
Credit Hamilton and Crosser (1962)
Question and Answers
What is nanofluid?
It is an advance fluid. It is prepared by dispersing nanoparticles in the base fluid.
What is base fluid?
The base fluid is conventional coolant liquid. It is used to prepare nanofluid.
Give the examples of some commonly used nanoparticles to prepare nanofluid.
The commonly used nanoparticles are Copper (Cu), Aluminium (Al), Iron (Fe), Aluminium Oxide (Al2O3), Copper Oxide (CuO), Titanium Oxide (TiO2 ) etc.
What are widely used preparation methods of nanofluid?
There are two methods widely used mentioned as below:
Two-step method
One-step method
What is the stability of nanofluid?
The stability can be stated as how long the particle keep dispersed in the base fluid. Technically, The higher stable nanofluid is one who has less sedimentation.
What is the use of surfactant in preparation of nanofluid?
The surfactant is used in nanofluid to increase its stability. The commonly used surfactant is sodium dodecyl sulfate (SDS).
Why hybrid nanofluid became a new research topic?
The individual application needs the desired properties of the material. To get likely properties in nanofluid, more than one nanoparticles are added in the base fluid.
Why the use of nanofluid results enhanced heat transfer?
The nanofluid is an advanced fluid with a higher thermal conductivity as the nanosized particles provide more surface area to conduct heat transfer.
How can nanofluid reduce the size of the heat exchanger?
This article is about basic introduction of nanofluid, preparation of nanofluid, application of nanofluid and properties of nanofluid. Recently, it is advance coolant in heat transfer applications. The scope of nanofluid is vast in present nanotechnology world. The nanofluid and its applications can be a good topic for students and researcher for project work.
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