Thermodynamic system and its classification

A thermodynamic system is defined as a fixed mass in space under thermodynamic consideration to analyse a problem.

The system is identified by a boundary drawn around the system which may be real or imaginary. Across the boundary, the energy transfer in the form of heat and work takes place.

Shape, volume, position of boundary may change during energy exchange with the surroundings.

Everything external to the system is called surroundings or environment. 

Thermodynamic System

A system and its surroundings together is called the universe.

Classification of Thermodynamic Systems :

Based on the mass and energy transfer between the system and the surrounding, the system can be classified as - Open system, Closed system and Isolated system.

1. Open system:

A system with mass transfer along with energy transfer across its boundaries is called an open system.

Fig a. shows open system which consists of turbine. It should be noted that the matter across the boundary of the system as the high pressure gases enter into the turbine and low pressure gases enter into the turbine and low pressure gases leave the turbine.

Also, it is not necessary that the quantity if matter within the boundaries of an open system to remain fixed.

Open System

2. Closed system:

A system without mass transfer across its boundaries is called a closed system.

Such systems have only the energy transfer in the form of heat and work with its surroundings across the system boundary.

Closed System

3. Isolated system:

If there is no mass and energy transfer between the system and surroundings, the system is said to be an isolated system.

Hence, according to the definition, universe is an isolated system. 

Handy example of isolated system is themos flask.

Isolated System

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First Angle and Third Angle Projection Methods | Engineering Drawing

To provide details of 2D drawing of any 3D object, two main types of projections are used and they are First Angle projection and Third Angle projection.
A collection of 2D drawings of any 3D object is represented with the help of orthographic projection. Orthographic projection consist of 6 views (Front, Back, Top, Bottom, Right, Left) called as principle views. Among these six orthographic views front view, right view and top view are the most commonly used to represent the orthographic projection of any object.

Method of Projection

Now, we know there are basically four quadrants. Hence to get the projections, we divide the object into four quadrants. First quadrant represents the First Angle projection of the object while third quadrant represents the Third Angle projection of the object. The principle projection planes and quadrants used to create 2D drawings can be seen in fig. 1.

Fig. 1. Principle Projection Planes and Quadrants

Now, let us see first angle and third angle projection in details.

First Angle Projection

In first angle projection, the object is placed in between the plane of projection and the observer as shown in fig.2.

Fig.2. Object in between Plane of projection and observer

 As explained above, in first angle projection, object is placed in first quadrant. The views are obtained by projecting the image of object in respective plane. Here you have to note down that the right hand side view is projected on the plane placed at the left of the object. After projecting the images on the respective planes, the bottom plane and the left plane is unfolded onto the front view i.e. left plane is unfolded towards left side to get Right Hand Side view on the left side of the front view. Similarly, bottom plane is unfolded towards the bottom to obtain the Top view placed below front view as shown in fig. 3.

Fig.3. First Angle Method

Third Angle Projection

In third angle projection, the plane of projection is placed in between the object and the observer as shown in fig.4.

Fig.4. Plane of projection in between object and observer

In this type of projection, the object is placed in third quadrant. The views are obtained by projecting the image on the respective plane as shown in fig.5.

Fig.5. Third Angle Projection

Symbols

As per BIS standard, drawing symbol for first angle projection and third angle projection are shown in fig.6.

Fig.6. Projection Symbol

Difference in between First Angle projection and Third Angle Projection

Due to increase in complication in drawings, second angle projection and fourth angle projection are not used. The difference between first angle projection and third angle projection is given below.

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Bourdon Presssure Guage - Pressure Measuring Device

A Bourdon pressure gauge consists of a bent tube of an elliptical cross section, a calibrated scale, gear and pinion arrangement. A typical sketch of Bourdon pressure gauge is shown in figure.
One end 'A' of the tube is sealed and its motion is transmitted to the pinion through the link E and gear.

Bourdon Pressure Gauge

The other end 'B' of the tube is open through which the fluid pressure is transmitted to the tube. The Bourdon pressure gauge measures the pressure difference inside the tube and the atmospheric pressure.
The bent tube tends to unbend when subjected to the fluid pressure. The deformation of thee tube is transmitted from end 'A' to the pinion and the needle will show the gauge pressure of the fluid on the calibrated scale.

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Design and Analysis of Rocket Nozzle

The functional part of rocket viz. rocket nozzle is used to channelize and accelerate the combustion products produced by the burning propellant inside rocket, in such a way that it maximizes the velocity of the exhaust at the exit. to the supersonic velocity. The nozzle converts chemical energy of propellant to kinetic energy without any moving parts. It is basically a tube with variable cross-sectional area.
Generally, nozzles are used to control the flow rate, direction, mass, speed, shape and the pressure of the exhaust stream that emerges from them. The nozzle converts high pressure, low velocity and high temperature gas in the combustion chamber into high velocity of gas of low pressure and temperature thus producing the required thrust for the rocket to propel.

Design and analysis of Rocket Nozzle

Rocket engine nozzle is propelling nozzle (usually of the de Laval type) used in rocket engine to expand and accelerate the combustion gases produced by burning propellant so that the exhaust gases exit the nozzle at hypersonic velocities. The convergent and divergent type of nozzle is called as de Laval nozzle. Throat is the area with minimum area in convergent divergent nozzle. The divergent part of the nozzle is known as nozzle exit. In the convergent section, the pressure of the exhaust gases will increase and as the hot gases expand through the diverging section attaining high velocities from continuity equation.
The analysis of rocket nozzle involves the concept of steady, one dimensional compressible fluid flow of an ideal gas. The goal of the rocket nozzle design is to accelerate the combustion products to as high exit velocity as possible. This is achieved by designing the necessary geometric nozzle profile with the condition that isentropic flow is considered to be flow that is dependent only upon cross sectional area. Therefore, in actual nozzle it is necessary to minimize the frictional effect, flow disturbances and conditions that can lead to shock losses. In addition, heat transfer losses should be minimize. That means it should be thermal resistant.
In this way, the properties of the flow are near isentropic and are simply affected only by the changing cross sectional area as the fluid flows through the nozzle. Space shuttle uses some of the largest de Laval nozzles in the solid rocket boosters. They are designed so as to optimize the weight and the performance.
In this project study is conducted to study the various configurations and geometries of de Laval nozzle with respect to the available technologies been used in the world. Further an effort is made to analyse the flow of the gases through a space shuttle nozzle using commercially available softwares.

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Design and Development of Coconut Grating Machine | Mechanical Engineering Project

At present about 4000 tonnes of desiccated coconut is manufactured annually and used mainly by confectionery, biscuit and food processing industries. Coconut grating machine grinds or grate the deshelled coconut flesh into desiccated coconut. The machine works on the speed reduction technique by using pulley belt arrangement. The overall size of the machine should be maintained as it helps to easily operate and smooth handling for workers. In less time, we can produce the maximum amount of coconut grate by using this machine. We can also make use of well sealed gearbox speed reduction. Depending upon the shape and quantity of shreds of the coconut, the grating disc changes respectively. Being highly efficient at shorter distance, V- belt is used in this mechanism.

Grating machine is useful for large scale production industries for coconut in large scale; it helps to satisfy the requirement of customer on time. Coconut dehusking and grating is the most fundamental issue in terms of finding labor and improving productivity. In food industries, we need large manpower because in every part of section we cannot use automatically operated machine. So to overcome this advantages coconut dehiscing and grating machine is good solution.

Final assembled machine

Components of Machine :

1. Main frame
2. Grating Disc
3. Electric motor
4. Shaft
5. V groove pulley
6. Belt
7. Bearing
8. Key

Components:

1. Main frame:

Main frame is constructed with rectangular shape. Material used for main frame is steel. The side edges/plates are welded together to form the frame. The welding of plates provides very rigid joints. Main frame is sealed properly and passages are provided in case of maintenance.

2. Grating disc:

It is the important part of the machine as it grates the coconut. Grating disc arrangement is designed for efficient grating of coconut. Grating disc is manufactured depending upon the application. Grating discs are made with different types of impressions on it.

3. Electric Motor:

For the rotation of grating disc an electric motor is used. Electric motor converts the electrical power into mechanical power required to drive the mechanism.

4. Shaft:

A shaft is a rotating machine element which is used to transmit power from one element to another element. In order to transmit power from shaft to other, various mechanical elements are used such as gears, couplings, belt drives, chain drives, etc. This machine uses two stage speed reduction and hence the shafts used are two.

5. Pulley:

Power transmission through belt pulley arrangement is the simplest method than other elements. There are different types of pulleys according to the type of belt selected. As we have selected V-belt, v groove pulley is used.

6. Belt:

Belts are the flexible links used to transmit the power over considerable distance. The belt should have high flexibility to easily bend while passing over other pulley. Belts are manufactured in the form of long bands and rolled as coils. V-belts are used due to its high efficiency over short distance and slip factor of v-belt is small as compared to other types of belts.

7. Bearing:

Bearing is a machine element that supports another rotating machine element. It permits relative motion between the contact surface of the members while carrying loads. The bearings used are single row deep groove ball bearings.

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What is Mechanical Engineering ? Is it hard ?

There are many of rumors about engineering and its different branches, and every student who is willing to take admission to Mechanical Engineering has a question in mind .... Is Mechanical Engineering really hard ?
Before going to the answer, we will discuss about what is engineering ?

What is Engineering ?

What is Engineering ?

Engineering, science and technology are three interlinked streams of scientific studies which differ in approaches based on attitudes of students,

Science is concerned with basic theories and exact calculations, while engineering aspires to serve humanity with creations, based on simplified scientific foundations.

What is Mechanical Engineering ?

What is Mechanical Engineering ?

Mechanical Engineering is one of the most exciting and fascinating disciplines. It possesses the evergreen charm of career making because of its importance in all fields of engineering applications.

The discipline explorers engineers to the conception, design, implementation and operation of mechanical systems in various aspects of life. In other words, it ranges from a small bicycle to the space shuttles.

Mechanical engineers work in the design, manufacturing, operation and marketing of innumerable industries, including aerospace, automotive, energy and power conversion, manufacturing, bio-mechanics, robotics, food processing, heavy machinery and household appliances.

Now, let us see is Mechanical Engineering that hard ?

Is Mechanical Engineering Hard ?

If you are thinking that Mechanical Engineering is hard then you are wrong. Here we are giving some points that show Mechanical Engineering is not that hard, what you are thinking.

1. Unlike science students, Mechanical Engineering students don't have to derive theorems. They are already derived, proved and verified. What you have to do is to apply those theorems, concepts on real life situations.

2. The subjects or the topics are very much repetitive in nature. Hence, once you grasp the basics, you will be able to apply them again and again.

3. Unlike electrical or electronics where you have to imagine, mechanical is very much visual subject.

4. You don't have to write any coding like Computer Science branch. Here you just have to follow the particular steps all the time.

5. At least you don't have to learn thoroughly LAPLACE or Z-transformations unlikely in Electrical Engineering.

6. Only Mechanics and Thermodynamics is the base of almost all other subjects.

Though all the points discussed above are right, any subject or topic that seems hard or easy depends upon your skills and interest. But I must say, it is always fascinating to learn Mechanical Engineering.

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