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Stress is force

There are various materials present in the world, like glass, mild steel, bricks and concrete. The mechanical engineering is based upon the material which can sustain the force applied on them for various purposes. The important properties of material such as mechanical properties, thermal properties, chemical properties and physical properties decide whether to use the material or not for engineering purpose. Brittle material such as bricks, wood and glass break by applying the force on them. Therefore, the brittle materials are not used for engineering purpose. For engineering purpose, ductile materials are considered as they sustain the deformation due to applied force. The important thing of the ductile materials is that they show various parameters that are required by the engineers. By mixing the ductile material with various other materials which are having some special properties, the engineers fulfill the various requirements. The example of the ductile materials is iron bar, mild steel, copper and gold. The elastic materials are the materials which can regain their respective dimensions after removing the force applied on them. The example of the elastic material is rubber. The plastic material is material which can not regain their respective dimensions after removing the force applied on them. The example of the plastic material is iron rod.

Important properties of the material-

i) Elasticity -

The important property of the material studied in mechanical engineering is elasticity of material. The property of the material to regain their original dimensions after removing the force, is known as elasticity.

ii) Plasticity -

The property of the material to deform permanently after removing the force applied on the body, is called plasticity.

iii) Strength - The property of the material to withstand the force applied on the material, is called it's strength. The material having more strength, can bear higher load.

iv) Ductility - The property of the material to be drawn into the form of wire, is called its ductility. The ductile material don't rupture and it deforms continuously after applying the force on it. In design and construction work, the ductile materials are used because of their respective property.

v) Malleability -

The material having malleability property can be drawn into the form of sheet. The material having malleability property can bear regular beating. It undergoes for continuous deformation, so it can be drawn into the form of sheet for engineering purpose and construction work.

vi) Brittleness -

The property of the material to break without giving any prior indication, is called brittleness of the material. The material having more brittleness don't bear impact load. It breaks instantaneously without giving prior indication of the breakage.

Stress

The force is the external agent that tries to change the state of the motion or the state of the rest of the body. If the force is applied to the iron bar, it will bend the iron bar. The force that try to resist the deformation of the iron bar against the applied force, that is called stress. When the force is applied to the body, there is some change in their respective dimensions. The chance in external dimensions due the applied force, is called as the deformation.

The body try to conflict with the force. The resistance is against the deformation of the body. There are several types of load - Point load, impact load, Uniformly distributed load and non- uniformly load. Point load is the load which acts on the body at a fixed and specific point. It does not act on the overall length of the body. Uniformly distributing load is the load which is acting on the body along the overall length of the body and it does not act on the only one point of the body. Non uniformly distributed load is the load which is acting on the whole length of the body but in the varying manner.

Stress

Stress = F / A,

Where F= applied force,

A= area where force is applied.

Unit of stress = Pascal

Types of stress

The direction of the applied force decides whether the stress is normal or longitudinal stress.

i) Normal stress-

There are various types of load and forces. The force that acts perpendicular to surface of the body, that is known as the normal force. If the normal force is applied to the iron bar, then the stress generated by the force is called as normal stress.

ii) Longitudinal stress-

Besides the normal force, there are some other forms of forces. They acts in linear direction. If the direction of the applied force is towards the center of the iron bar, it is known as the stress generated by the compressive force. It is called compressive stress. The important thing about this stress is that here the body gets compressed after applying the force.

However, if the direction of the applied force moving away from the center of the iron bar towards the outside of the iron bar, it will be stress due to the tensile force. It is known as tensile stress. The important thing is that here the force tries to elongate the body.

Compressive stress and tensile stress

Hooke's law of stress

There is a relationship between the two factors- stress and strain. It is demonstrated nicely with the help of Hooke's law. It is basically a graph showing the relationship between the two things- Stress and strain. When a body is subjected to a force, then there is some changes in the dimensions. It causes the iron bar to experience the stress as well as the strain. The law states that when a body is subjected to a load under its elastic limit, the stress generated inside the body by the force is directly proportional to the strain produced.

Here, the graph shows relationship between the stress and strain produced in the body. From origin to point (A), it shows elastic properties of the material. Point (B) show the proportional limit. Point (C) is showing the upper yield point and Point (D) is showing the lower yield point. Basically yield stress is generated in the body, when the body continue to enlarge without giving any increment in the prior load. Point (E) shows point of the ultimate strength. Ultimate strength of material is the point upto which the material can bear the load. After that limit of the applied force, if the amount of force is increased, then the body will rupture. Point (F) shows rupture point. Rupture stress is that stress that is produced by the force at the time of rupture.

Stress = C * strain,

where C = constant.

By adjusting the equation, Young's modulus is obtained.

Young's modulus = stress / strain,

Unit of Young's modulus is Pascal.

For more details click here,

Hooke's law of stress-

Strain

The strain can be found by dividing change in length by original length. When the force is applied to the iron bar, there must be some change in their respective dimensions. The another parameter is used to demonstrate the effectiveness of the applied force. The strain is the factor to illustrate the results of the force. .

Strain= change in the length/ the original length

Unit of the strain= no unit , it is unit less

For more information click here,

Strain-

Types of strain

i) Tensile strain -

When the two different forces applied to the body tries to elongate the body, then it is called tensile force. Then strain generated by this force is called tensile strain. The increase or decrease in the magnitude of the length causes the body to introduce the tensions in the surface.

i) Compressive strain -

When the two different forces applied to the body tries to decrease the size of the body, then it is called as compressive force. Then strain generated by this force is called compressive strain.

Linear strain-

The external forces applied on the body may change their respective dimensions. Then strain generated by the force in direction of the applied force is called simple strain. Liner strain is the strain generated by the force in direction of the external force.

Lateral strain -

The force applied on the surface of the body tries to increase or decrease the dimensions of the body. The strain in the perpendicular direction is called as the lateral strain.

Here, Length of the body= (l),

Thickness = (t),

Height = (h)

So,

Linear strain = (∆l) / (l),

Lateral strain = (∆t) / (t),

or ( ∆h) / (h)

Here,. ∆ = change in the dimensions

For more details, click here,

Linear strain

Poisson's Ratio -

The ratio of lateral strain and linear strain, is called Poisson's ratio. Generally the body undergoes to change in dimensions in various directions after applying the force on it. Linear strain is caused by the change in the legth. Lateral strain is due to the change in the dimensions in lateral direction.

Poisson's ratio = Lateral strain / Linear strain

For more details click here,

Shear stress-

Generally the force acts perpendicular to the body tries to increase or decrease the dimensions of the body. But there is some other forms of force acting on the surface of the body which is parallel to the surface of the body. This form of force is called shear force. The stress generated inside the body due this shear force is called Shear stress. Here strain generated by this force is called Shear strain. The shear force tries to moves the body parts in direction parallel to the surface of the body.

For more details click here,

shear stress-

Modulus of rigidity or shear modulus-

There are several ways to get information about the effect of the applied force. The most important and popular way to collect the information about the effect of the applied force, is modulus of rigidity.

Modulus of rigidity= shear stress / shear strain

Safe load

In any construction work, the engineers have to fulfill the various parameters of the materials. Every material can bear a load to a specific limit. After that limit, the object can not bear the load. The load below which machine works properly without rupture, that load is called safe load. Therefore, the engineers put the load on the construction materials below the safe load.

Safe load

3D Stress Hooke's law -

The body experiences the force in all directions. The application of the applied force causes the body to change their dimensions in all directions.

Here, the body tries to elongate or decrease in all directions.

Stress is generated in all directions.

When we apply of force on a body, the body get deform in all direction. the body experiences stress and force in all direction. There are mainly Three Types of stress. First stress is in direction of x-axis, second stress is in direction of y axis and third stress is in direction of Z axis.

The stress that is perpendicular to the surface that is known as normal stress. It is also known as direct stress. There are another stress that is known as shear stress. The shear stress is the stress that is parallel to the surface of the body. If we consider the surface of xy plane, the stress that is perpendicular to the plane that is known as direct stress or normal stress. But the stress that is parallel to the surface, and moving in the direction of x axis and y axis, they are called shear stress.

Direct stress and shear stress in 3Dimension Hooke's Law -

The stress generated by the application of force in the direction perpendicular to the surface of the body, that stress is known as the direct stress or normal stress. The stress generated due to the application of the force, in the direction parallel to the surface of the body, is known as the shear stress.

Various Planes and various stress in 3 Dimension Hooke's Law -

Failure -

When a force is working on a object continuosly, the object will get fractured after sometime, that is known as failure. For example, if we apply 10 Newton on a body and it is not a fracture, then we said that there is no failure. But if we apply force more than hundred Newton, then the object will get fractured, then that point is known as the fracture point.

Theory of failure -

There are various theories of the failure that explains how the object get fracture or how they get excessive elastic deformation. There are various modes of failure, first one is the excessive elastic deformation, second is the only sudden fracture. If we apply the excessive force continuously, then it may be possible that the object get excessive elastic deformation or there may be fracture of the object. There are various theories of the failure.

I) Rankine's theory

ii) Saint venant's theory

iii) Guest theory

iv) Haigh's theory

v) Von mises theory

.i )Rankine's Theory of failure -

According to this theory, the fracture takes place, when maximum principal stress reachs its maximum limit of its principal stress.

Limitations of Rankine's Theory of failure

There are various limitations of the Rankine theory. This theory considers only principal stress, it does not consider shear stress.

ii) Saint Venant's Theory of failure

This theory explains that the failure occurs when the maximum principal strain crosses or reaches its maximum principal strain in elastic mode.

Limitations of Saint Venant's Theory of failure

There are some limitations of this theory. According to this theory, the tensile stress is greater than the yield stress, but in experiment, it is found that the yield stress is greater than the tensile stress. And also it over estimates the elastic deformation of the material.

iii) Guest's Theory of failure

According to this theory, failure occurs when the maximum shear stress reaches its limits of maximum shear stress in elastic mode.

The maximum shear stress can be obtained by subtracting minimum stress from maximum stress and dividing them by two.

Limitations of Guest's Theory of failure

It is applicable only for the brittle object like cast iron.

Rankine theory of failure

Principal stress and principal Plane -

When the object experiences the effect of the force applied on the surface of the body, then the body gets deform. It also experiences stress on them. There are several types of stress generated in the object, while the force is applied on the body. Among the several types of stresses, the stress having largest magnitude is known as the Principal stress and the plane containing the Principal stress is known as the Principal plane. The principal stress generated by the force in the body can be calculated by considering the amount of stress and strain produced by the force on the various types of planes. Generally the Principal plane contain the information of the Principal Stress present in the body. There are many different ways to get the value of the Principal Stress.

Beam is a structure that is made up of a Iron and woods that can be used to bear the load. Generally the beam is used to make the most of the construction.

Connecting rod is the only thing that is the basis of the foundation of any types of the construction.

Types of Beam -

There are various types of beam. First one is cantilever beam, second one is fixed beam, third one is simply supported beam, forth one is overhanging beam, fifth one is continuous beam.

Cantilever Beam

The cantilever beam is the beam that is fixed on one side and free at the another side.

Simply supported Beam

The simply supported beam is the beam that is simply placed on the support.

Fixed Beam

Fixed Beam is the beam that is fixed at the both end of the beam.

Overhanging Beam

In case of overhanging beam, the bean is fully supported by the support but the other part of the bean is hanging over on the both side of the beam.

Continuous Beam

Continuous beam is the type of beam where the load is continuously distributed over length and the support.

The beam is a structure that has dimensions in which one dimension is abnormally longer than the other dimension. Generally, the beam has large length and short width.

There are several types of load, which are used in engineering purpose.

1) Point load -

Point load is the load which is acting on the body at a fixed and specific point. It does not act on the overall length of the body. The part of the construction which is experiencing a force on its surface, that force tries to deform the part permanently. The force that is actually acting on any point, that force is called Point load.

2) Regular load or uniformly distributed load -

Uniformly distributing load is the load which is acting on the body along the overall length of the body and it does not act on the only one point of the body.

3) Irregular load or non uniformly distributed load -

Non uniformly distributed load is the load which is acting on the whole length of the body but in the varying manner. At one point, it is very large and another point, it is very small in the magnitude.

Shear stress in beam -

When a force is applied on the body and if shear force is tried to find out, then the observer has to bisect the body into two parts. First one is right hand portion and first one part will be on right hand and the second one will be left hand part or portion. The right hand portion should be taken as a positive shear force and left hand portion should be taken as the negative shear force, if the direction of the forces try to move the body in clockwise direction. The right-hand portion should be taken as negative shear force and the left-hand portion should be taken as negative shear force, if the force tries to move the observed body in the anticlockwise direction.

Bending moment in various types of beam -

When a load is applied on the body and if the observer wants to find out bending moment generated in the body, then the observer has to bisect the body into two parts. First one is right hand portion and second one will be left hand part or portion.

The right hand portion and the left hand portion should be taken as positive bending moment, if it tries to move the body in upward direction. In language of engineering, it is called sagging.

The right hand portion and the left hand portion should be taken as negative bending moment, if it tries to move the body in downward direction. In language of engineering, it is called hogging.

If there is a beam and several types of forces are applied on that, then firstly , bisect the beam into the two section. The midpoint between the two forces, should be line at which the beam should be cut.

There is a cantilever beam. There is a load of 5 N acting on it.

The beam is bisected into two parts.

The right portion of the beam is trying to move the body in clockwise direction, as well as, the left portion of the beam is trying to move the body in clockwise direction. So, both are taken as positive shear force.

The right portion of the beam is trying to move the body in clockwise direction, in downward direction of the beam, but it is known as hogging. Here the bending moment is negative impact.

The left portion of the beam is trying to move the body in anticlockwise direction, and is known as the sagging. Here the bending moment is positive impact. The main remarkable facts about the bending moment is that the body should be able to make positive response to the body.

Shailendra posted in Technical

Post updated on: Aug 14, 2021 11:38:39 PM

Biodiesel

Today the world needs power from the source that never ends. Biodiesel is the only way to get power without damaging the environment. Biodiesel can be produced by various methods. It can be produced from vegetable oil and animal fats also. Biodiesel is a fuel that can be produced from vegetable waste also. Biodiesel helps in reducing the air pollution.

Biodiesel is a way to reduce the dependancy on diesel and petrol. Now a day, every country wants to get a new source of energy, without hampering the environment. In this regard, many researchers have almost predicted that the biodiesel derived from different sources has potential that it can be used in IC engines without alteration of the previous design parameters.

Needs of Biodiesel - Biodiesel fullfill the crisis of energy. Biodiesel is a fuel that can be easily produced from renewable sources. Emissions from road vehicles are major contributors of air pollution, which is very sensitive issue in Delhi and China. Biodiesel helps to run the engine with less production of air pollutants. It helps to reduce the air pollution. The engine optimization is achieved with biodiesel as it emits less carbon dioxide as compared to the engine running with diesel. The most promising nature of biofuel is that it can be utilised in the existing design of diesel engine without alteration. Biodiesel is very friendly to the diesel engine as it is not easy to remove engine hardware frequently.

Definition of Biodiesel - Biodiesel is basically polymer of ester. It is basically a well-defined long chain of fatty acid. It is better than the previous existing fuels. In the esterification process, firstly the triglycerides changes into di-glycerides, and then from diglycerides the mono-glycerides is obtained. In last step, mono-glycerides comes out with glycerin.

Triglycerides + Alcohol = Esters + Glycerin

Basically Esterification process helps to reduce the viscosity present in the biodiesel that is produced from vegetable oil and renewable resources. If the biodiesel is directly used in the diesel engine, it may damage the internal part of the engine because it has high viscosity. Due to viscosity, the internal parts of the diesel engine may slip or collapse while it is running.

Methods used for Production of Biodiesel -

1. Conventional Mechanical Stirring Method - The mechanical stirring method is used to mix the methanol and catalyst properly. This method is the cheapest way to get biodiesel.

The mechanical stirring machine consists of three major components : temperature controller, speed controller and magnetic stirrer. The temperature controller is used for maintaining the suitable temperature inside the beaker. The speed controller is used to control the speed of rotation of solution inside the beaker. The magnetic stirrer is the component which helps to mix the methanol and oil nicely by stirring the solution inside the beaker. The one should use induction heater to heat the solution inside the beaker.

Steps involed in production of the biodiesel-

1) Take sesame oil in beaker.

2) Take methanol and add catalyst in it.

3) Then mix it properly.

4) Put the solution on mechanical stirring machine.

5) Collect the biodiesel after stirring and settling process.

2 . Ultrasonic Cavitation Method- It is used nowadays as it produces more biodiesel from the oil. This method is costly method for biodiesel production, but less time consuming method.

There are many important parts of Ultrasonic horn type processor, such as start button, transducer horn and supporting tray. The start button is used for starting the machine. Supporting tray with sliding motion is used to support the beaker for stirring process. The main part of horn type processor is transducer horn. It helps to mix the solution of methanol and oil properly for extracting the biodiesel.

Steps involved in the production of the biodiesel -

1) The first step to produce the biodiesel is to mix oil with alcohol.

2) Mix the catalyst with the solution.

3) Put the solution in beaker.

4) Start the horn type ultrasonic machine.

5) Collect the biodiesel after the process of stirring and settling.

3. Soxhlet Extractor Method- It is very expensive method to produce the biodiesel from the vegetable waste. This method is very costly method for biodiesel manufacturing and is time consuming method also. Precautions should be taken while handling the apparatus. Soxhlet Extractor of mainly three components which are as follows; boiling flask, extraction chamber and last condenser. For heating purpose, the heating mantle is used.

Diagram of Soxhlet Extractor

The application of the apparatus with Hexane should be handled properly, otherwise it will cause accident.

Experimental procedure required for biodiesel production -

1) Firstly arrange the sesame seeds or any other plant seeds from market.

2) Then grind the seed properly by grinder.

3) Take a white cloth.

4) Put the grinded seed properly on the cloth, tie it.

5) Place the cloth containing seed above the boiling flask.

6) Start the heating mantle. The heating should be able to get biodiesel.

7) The biodiesel is collected by extractor chamber.

Biodiesel can be used as the fuel in vehicle, if it has following properties -

Biodiesel are used as fuel in vehicle nowadays. Fuel in vehicle must have some qualities. It should fulfill some parameters.

1) Availability of the fuel.

2) Cost of the fuel.

3) Exhaust gas should release less harmful gases.

4) It should run with the engine nicely.

Today the world needs the fuel that will not end. The biodiesel is the appropriate option because it can be produced by the plants. Biodiesel can be blended with the diesel and can be used as a fuel in engine. The engine running with the blended biodiesel gives the required result. B20 is the mixture of 20% biodiesel and 80% diesel. This B20 blend gives the appropriate result similar to the result of the diesel. The engine running with the biodiesel fulfill the requirement.

Description of the different types of blends of biodiesel-

Types of blends	amount of biodiesel	diesel
Diesel	0	1000
B20	200	800
B40	400	600
B60	600	400
B80	800	200
B100	1000	0

There are the various changes that are required for the biodiesel performance test. There should be a engine that is consist of the one cylinder and four stroke diesel engine. They should be connected to the Eddy current type dynamometer for loading and water cooling jacket also should be there. The setup should also consists of the stand-alone panel box and air box, fuel and oil tank, manometer, fuel measuring unit, transmitter for air and the fuel flow measurement.

There should be Piezo sensor and there should be crank angle sensor also. The load sensor, load indicator and temperature sensor should be there in the setup. The enginesoft is the software that is used for analysing the performance of the engine.

The diesel can be used as the fuel. There are two types of emission measuring equipment. First one is the smoke metre and second one is the exhaust gas analyser. Both can be used for measuring, calculating and analysing the information of exhaust products of the engine.

For more details about the biodiesel, please click here on the link,

Topic - Biodiesel used as fuel in vehicle

: https://www.connectclue.com/article/details/BLUR0071622208458675/data

Advantages of biodiesel -

1) The biodiesel is collected from various types of plant seeds.

2) When vehicle uses the biodiesel as fuel, it generates less carbon dioxide and carbon monoxide.

3) It is argued that biodiesel can be produced by renewable resources, therefore Biodiesel is easily accessible and available.

Disadvantages of biodiesel -

1) The biodiesel produces more nitrogen dioxide than diesel.

2) The work efficiency of the engine is lesser than the engine working with diesel.

The parts of the engine gets lubricated due to the use of the biodiesel.

The main remarkable facts about the biodiesel is that it can be used in engine without any modifications of internal parts of the engine. The decrease in the magnitude of efficiency of the engine working with the biodiesel, causes the research to pay attention on the engine optimization. The optimization of engine is determined by considering the load provided to vichecle and the efficiency of the engine.

Shailendra posted in Technical

Post updated on: Aug 6, 2021 1:27:33 AM

Beam and Stress in beam

Beam is made up of a steel, Iron and woods that can be withstand the load. The beam has dimensions in such a way that one dimension is abnormally shorter than the other dimension.

Types of Beam -

There are various types of beam.

Cantilever Beam

The cantilever beam is the beam in which the beam is supported by the fixed end on one side , and it is free at one end.

The cantilever beam is the beam that is fixed on one side and free at the another side.

Simply supported Beam

The simply supported beam is the beam in which the beam is supported by the point.

The simply supported beam is the beam that is simply placed on the support.

Fixed Beam

Fixed Beam is the beam in which the both ends of the beam is fixed. Fixed Beam is the beam that is fixed at the both end of the beam.

Overhanging Beam

In case of overhanging beam, the bean is fully supported by the support but the other part of the bean is hanging over on the both side of the beam.

Continuous Beam

Continuous beam is the type of beam which is giving regular load on the whole surface.

Continuous beam is the type of beam where the load is continuously distributed over length and the support.

There are several types of load, which is used in engineering purpose. Some of them are described below -

1) Point load

It is the load which acts on the body at a fixed and specific point. It does not consider or include the overall length of the body.

2) Regular load or uniformly distributed load -

It is the load which is acting on the body along the overall length of the body and it does not act on the only one point of the body.

3) Irregular load or non uniformly distributed load -

It is the load which is acting on the whole length of the body, but in the varying style. At one point, it is very high in magnitude and another point, it is very small in the magnitude.

Shear stress and bending moment in various types of beams -

When a load is supplied on the body, then the observer has to divide the body into two parts. First one is right hand portion and the second one will be left hand partion. The right hand portion should be taken as a positive shear force and left hand portion should be taken as the negative shear force, if the direction of the forces try to move the body in clockwise direction. The right-hand portion should be taken as negative shear force and the left-hand portion should be taken as negative shear force, if the force tries to move the observed body in the anticlockwise direction.

There is a cantilever beam. There is a load of 5 N acting on it.

The beam is bisected into two parts.

The right portion of the beam is trying to move the body in clockwise direction, in downward direction of the beam, but it is known as hogging. Here the bending moment is negative impact.

The left portion of the beam is trying to move the body in anticlockwise direction, and is known as the sagging. Here the bending moment is positive impact.

Shailendra posted in Strength of material

Post updated on: Aug 4, 2021 2:48:20 PM

Shear force and bending moment in various types of beam

Shear force in beam -

Bending moment in various types of beam -

The right hand portion and the left hand portion should be taken as positive bending moment, if it tries to move the body in upward direction. In language of engineering, it is called sagging.

The right hand portion and the left hand portion should be taken as negative bending moment, if it tries to move the body in downward direction. In language of engineering, it is called hogging.

There is a cantilever beam. There is a load of 5 N acting on it.

The beam is bisected into two parts.

The right portion of the beam is trying to move the body in clockwise direction, in downward direction of the beam, but it is known as hogging. Here the bending moment is negative impact.

The left portion of the beam is trying to move the body in anticlockwise direction, and is known as the sagging. Here the bending moment is positive impact.

Shailendra posted in Others

Post updated on: Aug 4, 2021 2:38:41 PM

Theory of failure

Failure -

Theory of failure -

There are various types of theories of the failure.

I) Rankine's theory

ii) Saint venant's theory

iii) Guest theory

iv) Haigh's theory

v) Von mises theory

.i )Rankine's Theory of failure -

According to this theory, the fracture takes place, when maximum principal stress reachs its maximum limit of its principal stress.

Rankine theory of failure

Disadvantages of Rankine's Theory of failure

There are various disadvantages of the Rankine theory. This theory illustrates only principal stress. It does not consider shear stress.

ii) Guest's Theory of failure

According to this theory, failure occurs when the maximum shear stress reaches its limits of maximum shear stress in elastic mode.

The maximum shear stress can be obtained by subtracting minimum stress from maximum stress and dividing them by two.

Disadvantages of Guest's Theory of failure

It is applicable only for the brittle object like cast iron.

iii) Saint Venant's Theory of failure

This theory explains that the failure occurs when the maximum principal strain crosses or reaches its maximum principal strain in elastic mode.

Disadvantages of Saint Venant's Theory of failure

For more information about Stress,

please click on this link.

Topic name - Stress is force

: https://www.connectclue.com/article/details/TTUR0071617635846094/data

Shailendra posted in Technical

Post updated on: Jun 14, 2021 9:05:02 AM

Thermodynamics

Thermodynamics -

Thermodynamics is the branch of science that deals with the study of thermal properties of the material present around us.

Thermodynamics is the branch of the science that deals with the relationship between the energy and the materials. There are various laws that govern the transformation of energy. Zeroth law is one of them. Thermodynamics is the study of the laws that causes the change in the state of physical system of the material.

The part of the space that we are going to investigate that is known a system. The part of the space beyond the system that is not under the investigation that is known as the surrounding. The line that separates the system and the surrounding that is known as boundary. .

Types of System -

I) Closed System

A system that is enclosed by a boundary and we cannot exchange the mass between the system and the surrounding, then the system is known as closed system.

ii) Open System

The system that is not inclosed by the boundary and we can exchange the mass and the energy between the system and the surrounding, then it is known as open system. The open system is a system that can lose its energy. A glass full of hot tea and hot water gets colder after sometime. This is the example of the open system.

iii) Isolated System

A system that is fully closed by boundary and there is no exchange of mass between the system and the boundary, then it is known as isolated system.

Zeroth Law of thermodynamics -

Zeroth Law explains that how system can get the thermal equilibrium. When one system is under thermal equilibrium with second system, and second system is under thermal equilibrium with the third system, then according to this law first system is under thermal equilibrium with the third system.

First law of Thermodynamics -

First law of thermodynamics states that the heat transfer is equal to the net work done, in case of a closed system, while going under through the Thermodynamics cycle.

It also illustrates that when we are in Thermodynamics cycle, then the work transfer is equal to the heat transfer. The most important condition for this is that the system must be the closed system. it can be taken as in other words such as the system cannot create and cannot not destroye the heat energy.

The energy cannot be created neither can be destroyed, while changing the state of the system in Thermodynamics cycle. There are various limitations of the first law of thermodynamics . Heat energy cannot be fully transformed into the mechanical energy. There are various applications of the first law of thermodynamics. The steady flow of the nozzle and diffuser can be explained using the first law of the thermodynamics. In case of steady flow process, the heat transfer and the work done are constant or they are stable.

Second law of Thermodynamics -

The second law of thermodynamics illustrates that the heat cannot transfer by itself from the lower temperature region to the higher temperature region.

The heat can transfer from the high-temperature region to the lower temperature region easily, but in case of lower temperature region, there should be some external force to help it. This law is also known as Clausius statement, in which the work is done by only when the heat transfer from the lower temperature region to the higher temperature region. The work is done, when the heat is transferred from the lower temperature region to the higher temperature region. Second law of the thermodynamics enables us to divide the process in the two parts, first one is the reversible process and the second one is the Irreversible process. In case of reversible process, the process can automatically reverse itself to its original shape or the original condition. In case of Irreversible process, the process cannot repeat itself or reverse itself automatically.

Quasi - static process -

Quasi- static process is the example of the reversible process. It is also known as the reversible process because there is very less deviation of its equilibrium position. All the states of the system may go through the change. The change in the state of equilibrium, is very negligible here, so it may be known as the reversible process.

Thermodynamics deals with the study of the initial and the final state of the system while undergoing to the various changes. Law of thermodynamics can be applied only when the system undergoes from one equilibrium to the another equilibrium or the system is already present in the state of equilibrium. In case of study of thermodynamics, the function or the variable that can affect the state of the equilibrium of the system, are known as the state variable. The example of these state variables are pressure, energy, heat, mass and work.

It is known to all that the heat is the energy transferred through the system at some temperature difference. The internal energy is the sum of potential energy well as kinetic energy. It is the state function because it depends on the state, it does not depend on the path through which it passes. The internal energy is the example of state function. The work done is generally calculated by the integration of product of pressure and a change of volume. The work done is the example of the path function because it depends on the path of the process.

The heat is the combination of the internal energy and the work done by the system. When the heat is added to the system, then it is taken as the positive heat. If it is taken out from the system, then it is known as the negative heat. If the internal energy increases in the system then it is taken as the positive energy. If energy is expelled from system, then it is taken as the negative internal energy.

Numerical -. A cylinder of oxygen is having internal pressure of 100 atm. At 30 degree Celsius, oxygen is stored in the cylinder which exerts pressure of 22 atm. At which temperature does the danger of explosion will sets in ?

Solution

Pressure of cylinder at the first state = P1

P1. = 100 atm

temperature = T1

Volume = V (volume is contant)

Pressure of cylinder at the second state = P2 = 22 atm

temperature = T2 = 303 Kelvin

Volume = V (volume is contant)

PV =n RT

For first state,

( P1) (V )=n R (T1) _____________________(1)

For second state,

(P2)(V )=n R (T2) ______________________(2)

Dividing equation (1) by equation (2)

( P1) (V ) / (P2)(V ). = n R (T1) / n R (T2)

(P1) / (P2) =. (T1) / (T2)

100/22 = (T1) / 303

(T1) = 1377 Kelvin (ans)

State variable -

The state variables are the variables which can explain or illustrate very clearly about the Thermodynamics system undergoing to the various changes of the states.

Examples of state variable are pressure, temperature and the volume. There are two types of variables - intensive and extensive variables.

Intensive variables

Intensive variables are the variables which are independent of the size of the system. The example of the intensive properties or intensive variables are pressure, temperature and density.

Extensive variables -

The extensive property or the variable are the variables which are dependent of the size of the system. The example of the extensive variables are mass, volume and number of moles. If we multiply the extensive and intensive variables, then the product will be the extensive variable. For example, if we multiply temperature with the volume, the product will be having the extensive properties. So, here the product is the extensive variable.

Thermodynamics process -

The process by which thermodynamic cycle or thermodynamics system is taken from one state to another state, is called thermodynamic process.

Isothermal process -

If thermodynamics system undergoes through the various changes and it change its state from one state to another state, then there will be some changes in their temperature or their pressure. If the temperature of both states remains constant, then the process is known as the isothermal process.

Isobaric process -

If the pressure of both, the first state and the second states remains constant, then the process is known as isobaric process.

Isochoric process -

If the volume of the first state and the second stage remains constant or unchanged, then the process is known as Isochoric process.