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ENGINEERING THERMODYNAMICS T H I R D E D I T I O N SI Units Version E N G I N E E R I N G S E R I E S R. K. Rajput. Applied Thermodynamics book. Read 2 reviews from the world's largest community for readers. Applied thermodynamics - Ebook download as PDF File .pdf) or read book online. thermodynamics. Engineering Thermodynamics-R.K Rajput. Uploaded by.
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About R. Books by R. Trivia About Applied Thermodyn No trivia or quizzes yet. Welcome back. Forced draught fans Water treatment plant Control room Switch yard.
Functions of some important parts of a steam power plant: Water is converted into wet steam. It converts wet steam into superheated steam. Steam at high pressure expands in the turbine and drives the generator. It condenses steam used by the steam turbine.
The condensed steam known as condensate is used as a feed water. Cooling tower. It cools the condenser circulating water. Condenser cooling water ab- sorbs heat from steam. This heat is discharged to atmosphere in cooling water. Condenser circulating water pump. It circulates water through the condenser and the cooling tower.
Feed water pump. It pumps water in the water tubes of boiler against boiler steam pressure. In economiser heat in flue gases is partially used to heat incoming feed water. Air preheater. In air preheater heat in flue gases the products of combustion is par- tially used to heat incoming air. The main components of a nuclear power plant are: Nuclear reactor 2.
Heat exchanger steam generator 3. Steam turbine 4. Electric generator. In a nuclear power plant the reactor performs the same function as that of the furnace of steam power plant i. The heat liberated in the reactor as a result of the nuclear fission of the fuel is taken up by the coolants circulating through the reactor core.
Hot coolant leaves the reactor at the top and then flows through the tubes of steam generator and passes on its heat to the feed water. The steam so produced expands in the steam turbine, producing work, and thereafter is condensed in the condenser. The steam turbine in turn runs an electric generator thereby producing electrical energy. In order to maintain the flow of coolant, condensate and feed water pumps are provided as shown in Fig. Heat Engines Any type of engine or machine which derives heat energy from the combustion of fuel or any other source and converts this energy into mechanical work is termed as a heat engine.
Heat engines may be classified into two main classes as follows: External Combustion Engine. Internal Combustion Engine. External Combustion Engines E. Engines In this case, combustion of fuel takes place outside the cylinder as in case of steam engines where the heat of combustion is employed to generate steam which is used to move a piston in a cylinder.
Other examples of external combustion engines are hot air engines, steam turbine and closed cycle gas turbine. These engines are generally needed for driving locomotives, ships, gen- eration of electric power etc. Internal Combustion Engines I.
Engines In this case combustion of the fuel with oxygen of the air occurs within the cylinder of the engine. The internal combustion engines group includes engines employing mixtures of combusti- ble gases and air, known as gas engines, those using lighter liquid fuel or spirit known as petrol engines and those using heavier liquid fuels, known as oil compression ignition or diesel engines.
Engines Many experimental engines were constructed around The first really successful engine did not appear, however until , when a German engineer Dr. Otto built his famous Otto gas engine.
The operating cycle of this engine was based upon principles first laid down in by a French engineer named Bea de Rochas.
The majority of modern I. The development of the well known Diesel engine began about by Rudoff Diesel. Al- though this differs in many important respects from the otto engine, the operating cycle of modern high speed Diesel engines is thermodynamically very similar to the Otto cycle.
Engines A cross-section of an air-cooled I. Parts common to both petrol and diesel engines 1. Cylinder 2. Cylinder head 3. Piston 4. Piston rings 5.
Gudgeon pin 6. Connecting rod 7. Crankshaft 8. Crank 9. Engine bearing Crank case Flywheel Governor Valves and valve operating mechanism.
Parts for petrol engines only 1. Spark plugs 2. Carburettor 3. Fuel pump. Parts for Diesel engine only 1. An air-cooled four-stroke petrol engine.
Spark Ignition S. Engines These engines may work on either four stroke cycle or two stroke cycle, majority of them, of course, operate on four stroke cycle. Four stroke petrol engine: Suction stroke.
During suction stroke a mixture of air and fuel petrol is sucked through the inlet valve I. The exhaust valve remains closed during this operation. Compression stroke. During compression stroke, both the valves remain closed, and the pressure and temperature of the mixture increase. Near the end of compression stroke, the fuel is ignited by means of an electric spark in the spark plug, causing combustion of fuel at the instant of ignition.
Working stroke. Next is the working also called power or expansion stroke. During this stroke, both the valves remain closed. Near the end of the expansion stroke, only the exhaust valve opens and the pressure in the cylinder at this stage forces most of the gases to leave the cylinder.
Exhaust stroke. Next follows the exhaust stroke, when all the remaining gases are driven away from the cylinder, while the inlet valve remains closed and the piston returns to the top dead centre. The cycle is then repeated. Air-fuel mixture S.
Gases Fig. Four stroke otto cycle engine. Two stroke petrol engine: In , Dugald-clerk, a British engineer introduced a cycle which could be completed in two strokes of piston rather than four strokes as is the case with the four stroke cycle engines. The engines using this cycle were called two stroke cycle engines.
In this engine suction and exhaust strokes are eliminated.
Here instead of valves, ports are used. The exhaust gases are driven out from engine cylinder by the fresh change of fuel entering the cylinder nearly at the end of the working stroke. The cylinder L is connected to a closed crank chamber C. During the upward stroke of the piston M, the gases in L are compressed and at the same time fresh air and fuel petrol mixture enters the crank chamber through the valve V. When the piston moves downwards, V closes and the mixture in the crank chamber is compressed.
Refer Fig. Ignition takes place at the end of the stroke. The piston then travels downwards due to expansion of the gases [Fig. The transfer port T. It may be noted that the incoming air petrol mixture helps the removal of gases from the engine-cylinder ; if, in case these exhaust gases do not leave the cylinder, the fresh charge gets diluted and efficiency of the engine will decrease.
The piston then again starts moving from bottom dead centre B. Two-stroke petrol engine. The power obtained from a two-stroke cycle engine is theoretically twice the power obtain- able from a four-stroke cycle engine.
Compression Ignition C. Engines The operation of C. The cycle in both the types, consists of suction, compression, ignition, expansion and exhaust. However, the combustion process in a C.
Since the compression ratio is very high between So when fuel is injected in the form of a spray at this stage, it ignites and burns almost as soon as it is introduced. The burnt gases are expanded and exhausted in the same way as is done in a S. General Aspects Probably a wind-mill was the first turbine to produce useful work, wherein there is no precompression and no combustion. The characteristic features of a gas turbine as we think of the name today include a compression process and an heat addition or combustion process.
The gas The gas turbine may have a future use in conjunction with the oil engine.
For smaller gas turbine units, the inefficiencies in compression and expansion processes become greater and to improve the thermal efficiency it is necessary to use a heat exchanger. In order that a small gas turbine may compete for economy with the small oil engine or petrol engine it is necessary that a compact effective heat exchanger be used in the gas turbine cycle.
Higher efficiencies might be attained in future. The following are the major fields of application of gas turbines: Aviation 2. Power generation 3. Oil and gas industry 4. Marine propulsion. The efficiency of a gas turbine is not the criteria for the choice of this plant.
A gas turbine is used in aviation and marine fields because it is self-contained, light weight, not requiring cooling water and generally fits into the overall shape of the structure. It is selected for power generation because of its simplicity, lack of cooling water, needs quick installation and quick starting.
It is used in oil and gas industry because of cheaper supply of fuel and low installation cost. The gas turbines have the following limitations: Classification of Gas Turbines The gas turbines are mainly divided into two groups: Constant pressure combustion gas turbine: Constant volume combustion gas turbine.
In almost all the fields open cycle gas turbine plants are used. Closed cycle plants were introduced at one stage because of their ability to burn cheap fuel. In between their progress remained slow because of availability of cheap oil and natural gas. Because of rising oil prices, now again, the attention is being paid to closed cycle plants.
A gas turbine does not require a flywheel as the torque on the shaft is continuous and uniform. Whereas a flywheel is a must in case of an I. The weight of gas turbine per H. The gas turbine can be driven at a very high speeds 40, r. The work developed by a gas turbine per kg of air is more as compared to an I.
This is due to the fact that gases can be expanded upto atmospheric pressure in case of a gas turbine whereas in an I. The components of the gas turbine can be made lighter since the pressures used in it are very low, say 5 bar compared with I. In the gas turbine the ignition and lubrication systems are much simpler as compared with I.
Cheaper fuels such as paraffine type, residue oils or powdered coal can be used whereas special grade fuels are employed in petrol engine to check knocking or pinking. The exhaust from gas turbine is less polluting comparatively since excess air is used for combustion.
Because of low specific weight the gas turbines are particularly suitable for use in aircrafts. Demerits of gas turbines 1. With wide operating speeds the fuel control is comparatively difficult. Due to higher operating speeds of the turbine, it is imperative to have a speed reduction device. It is difficult to start a gas turbine as compared to an I.
The gas turbine blades need a special cooling system. Refer to Fig. A simple gas turbine plant consists of the following: A compressor mounted on the same shaft or coupled to the turbine.
The combustor. Auxiliaries such as starting device, auxiliary lubrication pump, fuel system, oil system and the duct system etc. Simple gas turbine plant. A modified plant may have in addition to above an intercooler, regenerator, a reheater etc.
The working fluid is compressed in a compressor which is generally rotary, multistage type. Heat energy is added to the compressed fluid in the combustion chamber. This high energy fluid, at high temperature and pressure, then expands in the turbine unit thereby generating power. Part of the power generated is consumed in driving the generating compressor and accessories The gas turbines work on open cycle, semiclosed cycle or closed cycle.
In order to improve efficiency, compression and expansion of working fluid is carried out in multistages. Energy flow diagram for gas-turbine unit. Shaft energy to drive compressor is about twice as much as the useful shaft output.
Actually the shaft energy keeps circulating in the cycle as long as the turbine runs. The important comparison is the size of the output with the fuel input. Refrigerators work mainly on two processes: Vapour compression, and 2. Vapour absorption. Simple Vapour Compression System: In a simple vapour compression system the following fundamental processes are completed in one cycle: Expansion 2.
Vapourisation 3. Compression 4. Simple vapour compression cycle. Domestic Refrigerator: They are manufactured in different size to meet the needs of various groups of people. They are usually rated with internal gross volume and the freezer volume. The refrigerators in India are available in different sizes of various makes, i. The freezers are usually provided at top portion of the refrigerator space occupying around one-tenth to one-third of the refrigerator volume. In some refrigerators, freezers are provided at the bottom.
A domestic refrigerator consists of the following two main parts: The refrigeration system.
The insulated cabinet. A simple domestic refrigerator consists of a hermetic compressor placed in the cabinet base. The condenser is installed at the back and the evaporator is placed inside the cabinet at the top.
The working of the refrigerator is as follows: The accumulator provided between the suction line and the evaporator collects liquid refrigerant coming out of the evaporator due to incom- plete evaporation, if any, prevents it from entering the compressor.
The compressor then compresses the refrigerant vapour to a high pressure and high temperature. The compressed vapour flows through the discharge line into condenser vertical natural draft, wire-tube type.
Domestic refrigerator. The capillary tube is attached to the suction line as shown in Fig. The warm refrigerant passing through the capillary tube gives some of its heat to cold suction line vapour. This increases the heat absorbing quality of the liquid refrigerant slightly and increases the superheat of vapour entering the compressor.
The capillary tube expands the liquid refrigerant at high pressure to the liquid refrigerant at low pressure so that a measured quantity of liquid refrigerant is passed into the evaporator. Any type of engine or machine which derives heat energy from the combustion of fuel or any other source and converts this energy into mechanical work is termed as a heat engine.
The major fields of application of gas turbines are: Refrigeration means the cooling or removal of heat from a system. Refrigerators work mainly on two processes i Vapour compression and ii Vapour absorption.
Give the layout of a modern steam power plant and explain its various circuits. List the components of a nuclear power plant. Draw the cross-section of an air cooled I. Explain with neat sketches the working of a four stroke petrol engine. How are gas turbines classified? What are the major fields of application of gas turbines? With the help of a neat diagram explain the working of a simple gas turbine plant. Draw the energy cycle for a simple-cycle gas turbine. Explain with a neat sketch the working of a simple vapour compression system.
Draw the neat diagram of a domestic refrigerator, showing its various parts. Explain its working also. Introduction to kinetic theory of gases.
Definition of thermodynamics. Thermodynamic systems—system, boundary and surroundings—closed system—open system—isolated system—adiabatic system—homogeneous system—heterogeneous system.
Macroscopic and microscopic points of view. Pure substance. Thermodynamic equilibrium. Properties of systems. Point function. Path function. Zeroth law of thermodynamics. The thermometer and thermometric property—introduction— measurement of temperature—the international practical temperature scale—ideal gas. Pressure—definition of pressure—unit for pressure—types of pressure measurement devices—mechanical-type instruments—liquid manometers—important types of pressure gauges. Specific volume.
Reversible and irreversible processes. Energy, work and heat—energy—work and heat. According to this theory, the molecules of all gases are in continuous motion. As a result of this they possess kinetic energy which is transferred from molecule to molecule during their collision. The energy so transferred produces a change in the velocity of individual molecules. The complete phenomenon of molecular behaviour is quite complex.
The assumptions are therefore made to simplify the application of theory of an ideal gas. The molecules of gases are assumed to be rigid, perfectly elastic solid spheres, identical in all respects such as mass, form etc.
The mean distance between molecules is very large compared to their own dimensions. The molecules are in state of random motion moving in all directions with all possible velocities and gas is said to be in state of molecular chaos.
The collisions between the molecules are perfectly elastic and there are no intermolecu- lar forces of attraction or repulsion.
This means that energy of gas is all kinetic. The number of molecules in a small volume is very large. The time spent in collision is negligible, compared to the time during which the mol- ecules are moving independently. Between collisions, the molecules move in a straight line with uniform velocity because of frictionless motion between molecules.
The volume of molecule is so small that it is negligible compared to total volume of the gas. Let us consider a quantity of gas to be contained in a cubical vessel of side l with perfectly elastic wall and N represent the very large number of molecules in the vessel. Now let us consider a molecule which may be assumed to have a velocity C1 in a certain direction.
The velocity can be resolved into three components u1, v1, w1 parallel to three co-ordinate axes X, Y and Z which are again assumed parallel to the sides of the cube as shown in Fig. Let this molecule having mass m strike wall surface ABCD of the cube with velocity u1. Since the collision is perfectly elastic, the molecule will rebound from this surface with the same velocity u1.
This means molecule covers 2l distance to hit the same face again. Hence the time taken by the same molecule to strike the same face ABCD again is 2 1 l u. Since pressure exerted by the gas is the same in all directions, i.
Equation 2. From equations 2. Molar gas equation From equation 2. It is known as the kinetic interpretation of temperature. Hence, the absolute temperature of a gas is proportional to the mean translational kinetic energy of the molecules it consists. If the temperature is fixed, then the average K.
It describes state and changes in state of physical systems. Or Thermodynamics is the science of the regularities governing processes of energy conversion.
Or Thermodynamics is the science that deals with the interaction between energy and material systems. Thermodynamics, basically entails four laws or axioms known as Zeroth, First, Second and Third law of thermodynamics. These laws are based on experimental observations and have no mathematical proof.
Like all physical laws, these laws are based on logical reasoning. System, Boundary and Surroundings System. A system is a finite quantity of matter or a prescribed region of space Refer Fig. The actual or hypothetical envelope enclosing the system is the boundary of the system. The boundary may be fixed or it may move, as and when a system containing a gas is compressed or expanded.
The boundary may be real or imaginary. It is not difficult to envisage a real boundary but an example of imaginary boundary would be one drawn around a system con- sisting of the fresh mixture about to enter the cylinder of an I. The system. The real and imaginary boundaries.
Closed System Refer to Fig. If the boundary of the system is impervious to the flow of matter, it is called a closed system. An example of this system is mass of gas or vapour contained in an engine cylinder, the boundary of which is drawn by the cylinder walls, the cylinder head and piston crown. Here the boundary is continuous and no matter may enter or leave.
Closed system. Open system. Open System Refer to Fig. An open system is one in which matter flows into or out of the system. Most of the engineering systems are open. Isolated System An isolated system is that system which exchanges neither energy nor matter with any other system or with environment. Adiabatic System An adiabatic system is one which is thermally insulated from its surroundings. It can, however, exchange work with its surroundings. If it does not, it becomes an isolated system.
A phase is a quantity of matter which is homogeneous throughout in chemical composition and physical structure. Homogeneous System A system which consists of a single phase is termed as homogeneous system. Mixture of air and water vapour, water plus nitric acid and octane plus heptane. Heterogeneous System A system which consists of two or more phases is called a heterogeneous system. Water plus steam, ice plus water and water plus oil.
Macroscopic approach— Macro mean big or total 2. Microscopic approach— Micro means small Macroscopic approach Microscopic approach 1. In this approach a certain quantity of matter is consideredwithout taking into account the events occurring at molecular level. In other words this approach to thermodynamics is concerned with gross or overall behaviour.
This is known as classical thermodynamics. The approach considers that the system is made up of a very large number of discrete particles known as molecules. These molecules have different velocities and energies.
The values of these energies are constantly changing with time. Basic Steam Power Cycles 3. Reciprocating Steam Engine 4. Compound Steam Engines 5. Steam Nozzles 6. Steam Turbines 7. Steam Condensers 8. Gas Power Cycles 9. Internal Combustion Engines Air Compressors Building Construction.
Surveying Vol. How to Become a Human Calculator.