Fundamentals of Mechanical Engineering PDF

Fundamentals of Mechanical Engineering T2425103 FUNDAMENTALS OF MECHANICAL ENGINEERING UNIT 1 INTRODUCTION TO THERMODYNAMICS Introduction to Thermodynamics...

Fundamentals of Mechanical Engineering T2425103 FUNDAMENTALS OF MECHANICAL ENGINEERING UNIT 1 INTRODUCTION TO THERMODYNAMICS Introduction to Thermodynamics First law, Second law and Zeroth law of Unit Content: thermodynamics Modes of heat transfer CO201.1: Explain Thermodynamics System and Modes of Course Outcome (CO) Covered for this unit: Heat Transfer Number Lectures planned in Teaching Ten Plan:  Basic Mechanical Engineering – M.P. Poonia & S.C. Reference: Sharma, Khanna Publishing House,Delhi P a g e 1 | 18  Fundamentals of Mechanical Engineering T2425103 Lecture Number: 01 Topics to cover: Course Introduction through Concept Map P a g e 2 | 18  Fundamentals of Mechanical Engineering T2425103 Lecture Number: 02 Topics to cover: Role of Thermodynamics in Engineering and Science, Introduction to Thermodynamics Thermodynamics is the branch of physics that deals with the study of the relationships between heat, work, and energy. It is concerned with the macroscopic behaviour of systems and processes, rather than the microscopic behaviour of individual particles. Some key concepts in thermodynamics include temperature, energy, heat, work, entropy, and the laws of thermodynamics. Temperature is a measure of the average kinetic energy of the particles in a system. Energy is the ability to do work, and can exist in various forms such as kinetic energy, potential energy, and internal energy. Heat is the transfer of energy between systems due to a temperature difference. Work is the transfer of energy due to a force acting through a distance. It is used to study the behaviour of systems ranging from individual atoms and molecules to large-scale industrial processes and global climate patterns. Role of Thermodynamics in Engineering and Science Thermodynamics plays a crucial role in both engineering and science. Here are some ways in which it is used in each field: Engineering: Power generation: Thermodynamics is used to design and optimize power generation systems, such as steam turbines and internal combustion engines. Engineers use thermodynamic principles to determine the efficiency and performance of these systems, and to optimize them for maximum power output. Heat transfer: Thermodynamics is used to study heat transfer in various engineering applications, such as in heat exchangers, refrigeration and air conditioning systems, and chemical reactors. Engineers use thermodynamic principles to determine the rate of heat transfer and to design systems that can efficiently transfer heat from one location to another. Materials science: Thermodynamics is used in materials science to study the behaviour of materials at different temperatures and pressures. Engineers use thermodynamic principles to design materials with specific properties, such as high strength or low thermal conductivity. Aerospace engineering: Thermodynamics is used in the design and optimization of aerospace systems, such as jet engines and rocket propulsion systems. Engineers use P a g e 3 | 18  Fundamentals of Mechanical Engineering T2425103 thermodynamic principles to determine the performance and efficiency of these systems, and to optimize them for maximum thrust and fuel efficiency. Science: Chemistry: Thermodynamics plays a crucial role in chemistry, particularly in the study of chemical reactions and phase transitions. Chemists use thermodynamic principles to predict whether a chemical reaction will occur spontaneously or not, and to determine the amount of energy required or released during a reaction. Earth science: Thermodynamics is used in the study of Earth's climate and atmospheric processes. Scientists use thermodynamic principles to understand how energy is transferred and transformed within the Earth's atmosphere and oceans, and to predict how the climate will change in response to human activities. Astrophysics: Thermodynamics is used in astrophysics to study the behaviour of stars, galaxies, and other celestial bodies. Astrophysicists use thermodynamic principles to understand how energy is generated and transferred within these systems, and to predict their behaviour over time. Overall, thermodynamics is a fundamental discipline that has wide-ranging applications in both engineering and science. Its principles and laws are used to understand and optimize a wide range of physical systems, from power generation and heat transfer to chemical reactions and celestial phenomena. Lecture Number: 03 Topics to cover: Types of Thermodynamics Systems Types of Systems In thermodynamics, a system refers to any part of the universe that is under consideration. A system can be divided into two main categories based on the type of interaction it has with its surroundings: P a g e 4 | 18  Fundamentals of Mechanical Engineering T2425103 1. Open Systems: An open system is one that can exchange both mass and energy with its surroundings. For example, a pot of boiling water on a stove is an open system because it can exchange heat and steam with the environment. Examples: Steam turbine, Steam Nozzle etc. 2. Closed Systems: A closed system is one that can exchange energy with its surroundings, but not mass. For example, a sealed container of gas is a closed system because it can exchange heat with the environment, but the gas cannot escape. Ex: Piston and cylinder without valve, Refrigeration system. 3. Isolated system: In this system it cannot transfer either mass or energy with the surrounding. It is purely theoretical system. Ex: Tea present in a thermos flask. Properties of a System Thermodynamic properties are defined as characteristic features of a system, capable of specifying the system’s state. Thermodynamic properties may be extensive or intensive. 1. Intensive properties: Intensive properties is defined as the property which do not depend upon the mass of the system. Examples of intensive properties include temperature, pressure, density, and specific heat capacity. 2. Extensive properties: Extensive properties is defined as the property which depends on the mass or size of the system. Examples of extensive properties include mass, volume, enthalpy, and entropy. Thermodynamic Process A system undergoes a thermodynamic process when there is some energetic change within the system that is associated with changes in pressure, volume and internal energy. Adiabatic Process – A process where no heat transfer into or out of the system occurs. Isochoric Process – A process where no change in volume occurs and the system does no work. P a g e 5 | 18  Fundamentals of Mechanical Engineering T2425103 Isobaric Process – A process in which no change in pressure occurs. Isothermal Process – A process in which no change in temperature occurs. State It is defined as the exact condition of a substance, to define it at least two properties are known. Even if one property is changing then the state of the substance changes. Cycle It is defined as a process or combination of processes so conducted that the initial and final state of the system are the same. Lecture Number: 04 Specific Volume, enthalpy, pressure, temperature, Topics to cover: thermodynamic work & thermodynamic equilibrium Specific volume It is defined as the ratio of volume per unit mass mass of the substance. Its S.I unit is m3/kg. Formula: v = Specific volume V = volume m = mass Pressure It is defined as the force applied perpendicular to the surface of an object per unit area. The SI unit of pressure is the pascal (Pa). Formula: P = pressure F = force A = area Temperature Temperature is the measure of hotness or coldness of a body. An object temperature is related to the average kinetic energy of its molecules. The SI unit of temperature is Kelvin (k). It is measured in Celsius C and Fahrenheit F. P a g e 6 | 18  Fundamentals of Mechanical Engineering T2425103 Enthalpy Enthalpy is a thermodynamic property that describes the total energy content of a system. It is equal to the sum of the system's internal energy and the product of its pressure and volume. Enthalpy is represented by the symbol ‘H’. Its unit is KJ/Kg. Formula: Enthalpy= H Internal energy= E Pressure= P Volume= V Entropy Entropy is a measure of the disorder of a system or energy unavailable to do work. Entropy is a thermodynamic property of a working substance which increases with the addition of heat and decreases with the removal of heat. Entropy is represented by the symbol ‘S’. Its unit is KJ/kg K. 𝑑𝑑𝑄𝑄 Formula: ∆𝑆𝑆 = 𝑇𝑇 ΔS = change in entropy T = absolute temperature dQ = change in heat Thermodynamics Work In thermodynamics, work is the energy transferred from one system to another without the transfer of mass due to a force causing movement. For example, when gas in a cylinder expands, it pushes against a piston, doing work on it. Thermodynamics equilibrium Thermodynamic Equilibrium refers to a state in which a system is balanced in such a way that there are no net changes in its properties, such as temperature, pressure, or concentration, over time. In this state, the system's macroscopic properties remain constant because all processes occurring within it are balanced. Examples: engines, refrigerators, and air conditioning. P a g e 7 | 18  Fundamentals of Mechanical Engineering T2425103 Lecture Number: 05 Topics to cover: First law, second law and zeroth law of thermodynamics First Law of Thermodynamics The first law of thermodynamics states that energy cannot be created or destroyed, but it can be transferred or converted from one form to another. The first law of thermodynamics is often referred to as the law of conservation of energy. Examples: Heating Water in a Closed Container, Piston-Cylinder Arrangement (Gas Expansion) Formula: ΔU= Q−W Internal energy = ΔU, Heat = Q, Work = W The first law of thermodynamics has many practical applications, such as in the design and operation of heat engines, power plants, and refrigeration systems. The law also plays an important role in understanding the behaviour of gases, liquids, and solids in different states and under different conditions Second law of thermodynamics It states that the total entropy of a system and its surroundings always increases over time. Entropy is a measure of disorder or randomness, and the Second Law essentially states that energy transformations are not 100% efficient; some energy is always lost as waste heat, increasing the disorder in the universe. Heat cannot flow from a colder body to a hotter body without the input of external work. The efficiency of a heat engine cannot be 100%. The second law of thermodynamics has many practical applications in engineering, such as in the design of refrigeration systems, power plants, and engines. It is also important in chemistry and materials science, where it governs the behaviour of chemical reactions, phase transitions, and the formation of crystals. The Second Law of thermodynamics can be stated by two well-known statements as follows: Kelvin Planck statement: It is impossible to construct an engine whose sole purpose is to convert all the heat energy to work. The Kelvin-Planck statement is based on the concept of a heat engine, which is a device that converts thermal energy into mechanical work. P a g e 8 | 18  Fundamentals of Mechanical Engineering T2425103 Clausius statement: It is impossible for the heat to flow from a body at lower temperature to another body at higher temperature without any external work. The Clausius statement is based on the concept of a heat pump, which is a device that transfers heat from a low-temperature source to a high-temperature sink. Elementary Introduction to Zeroth law The zeroth law of thermodynamics is a fundamental principle that governs the behavior of thermodynamic systems. The law states that if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. The law also provides a way to establish the direction of heat flow between two systems that are not in thermal equilibrium. To understand the zeroth law, imagine three systems A, B, and C. If system A is in thermal equilibrium with system B, and system B is in thermal equilibrium with system C, then we can conclude that system A is also in thermal equilibrium with system C. This is because if there were a temperature difference between system A and system C, then heat would flow from the hotter system to the colder system until they reached thermal equilibrium. P a g e 9 | 18  Fundamentals of Mechanical Engineering T2425103 Lecture Number: 06 Topics to cover: Enthalpy of wet steam, Superheated steam Wet Steam When steam contains some water particles in suspended form, it is known as wet steam. The suspended water particles are known as moisture. The wet steam is a mixture of two phase i.e. liquid and vapour. The temperature of wet steam is the saturation temperature at given pressure of steam The dryness fraction is less than one Equation of Enthalpy : hwet = hf + x hfg Equation of Entropy : Swet = Sf + x (Sg - Sf) Dry steam or saturated steam When steam contains no moisture is known as dry steam or dry saturated steam. The temperature of dry steam is the saturation temperature (Tsat). The dryness fraction is one. Superheated steam If dry saturated steam is at saturation temperature (Tat) is heated, its temperature will start increasing, this higher temperature of steam is known as f superheated temperature (Tsup). And the steam is known as superheated steam. The dryness fraction is greater than one hence it is superheated. The superheated steam have no moisture content. Equation of Enthalpy : hsup = hf + hfg Equation of Entropy: Ssup = Sf + (Sg - Sf) Dryness Fraction: Wet steam contains some moisture thus a term dryness fraction is defined which gives indication regarding the dryness of steam. Amount of dry steam in one kg of wet steam. It is denoted by 'x' ms = mass of dry steam mw = mass of moisture x = ms / m s + m w P a g e 10 | 18  Fundamentals of Mechanical Engineering T2425103 If 1 kg of wet steam contain 0.8 kg of dry steam. Then dryness fraction x = 0.8 If steam is 30% wet then dryness fraction is, x= 0.7 For saturated steam, dryness fraction, x = 1 For saturated liquid, dryness fraction, x = 0 The region from saturated liquid to saturated steam dryness fraction varies from 0 to 1. Superheated steam does not exit dryness fraction. Latent Heat: It is defined as the amount of heat required for the change of phase of 1kg of water at saturated temperature to dry saturated steam at constant temperature and pressure. It is denoted by L. It's value can be directly obtained from steam table. Sensible Heat: Sensible Heat is defined as the heat which can be sensed by thermometer i.e. change in temperature can be observed but there is no change of phase take place. Sensible heat = m Cp (T2 - T1) m = mass Cp = specific heat at constant pressure T1 = Initial temperature T2 = Final temperature Enthalpy of Steam It is the amount of heat added to 1 kg of water during heating from freezing point 0 ° C to the boiling point is known as Enthalpy of saturated water (Sensible heat of water). hf = mCp (ts - to) ts = Saturation temperature of water = 100°C to Initial temperature of water = 0°C Cp = 4.187 kJ/kgoK Let mass = m = 1 kg hf = 1 x 4.187 (100-0) = 4.187 kJ/kg Enthalpy of dry saturated steam (Evaporation enthalpy of water) : Definition : It is the amount of heat required to convert 1 kg of water form saturation temperature (ts) into dry saturated steam at same temperature and pressure. It is also called as Latent enthalpy It is denoted by hfg hg = hf + hfg P a g e 11 | 18  Fundamentals of Mechanical Engineering T2425103 The quantity of heat required to convert 1 kg of water 0°C into dry saturated steam at constant pressure is known as enthalpy of dry saturated steam. Enthalpy of superheated steam Definition : An amount of heat required to one kg of water from freezing temperature into super heated steam is called enthalpy of super heated steam Equation of Enthalpy : hsup = hg + Cp (Tsup - Tsat) Equation of Entropy: Ssup =Sg + Cp ln (TSup / Tsat ) The quantity of heat required to convert 1 kg of water at 0°C into superheated steam at constant pressure is known as enthalpy of superheated steam. Steam Table The properties like specific enthalpy, specific entropy, specific volume are tabulated in the form of steam table with reference to 0.C water. The steam table gives the properties of steam at various pressure and temperature. Lecture Number: 07 Modes of heat transfer: Conduction, Convection & Topics to cover: Radiation Heat transfer Heat transfer refers to the movement of thermal energy from one object or system to another due to a temperature difference between them. Heat can be transferred by three main mechanisms: conduction, convection, and radiation. Modes of Heat Transfer The three main modes of heat transfer are: P a g e 12 | 18  Fundamentals of Mechanical Engineering T2425103 1. Conduction: Conduction is the transfer of heat through a material without any net motion of the material itself. It occurs due to the molecular collisions and interactions within the material. Heat always flows from a region of higher temperature to a region of lower temperature. Metals are good conductors of heat. 2. Convection: Convection is the transfer of heat by the motion of a fluid, such as a liquid or gas. In natural convection, the motion of the fluid is driven by temperature differences, while in forced convection, external forces such as pumps or fans are used to drive the fluid. Convection is a more efficient mode of heat transfer than conduction since it involves the motion of matter. 3. Radiation: Radiation is the transfer of heat through electromagnetic waves, without the need for a medium. All objects emit and absorb radiation, and the amount of radiation emitted depends on the temperature and the surface properties of the object. Radiation is important in the transfer of heat from the sun to the Earth, and it is also used in applications such as heating and cooling systems, power generation, and materials processing. Composite walls and cylinders Composite walls and cylinders refer to structures made up of different materials with distinct thermal conductivities. Such structures are designed to optimize the thermal performance of the system, while also taking into consideration other factors such as mechanical strength, cost, and durability. In the case of composite walls, the aim is to reduce the rate of heat transfer from one side of the wall to the other. The thermal resistance of a composite wall depends on the thermal conductivity of each layer and the thickness of each layer. The layers can be arranged in different configurations, such as in series or in parallel, to achieve the desired thermal performance. For example, a typical composite wall might consist of an outer layer of brick, an inner layer of insulation, and a layer of concrete in between. Similarly, composite cylinders are designed to minimize the rate of heat transfer through the cylinder wall. The thermal performance of a composite cylinder depends on the thermal conductivity of each layer and the thickness of each layer. The layers can be arranged in different configurations, such as in series or in parallel, to achieve the desired thermal P a g e 13 | 18  Fundamentals of Mechanical Engineering T2425103 performance. For example, a typical composite cylinder might consist of an outer layer of metal, an inner layer of insulation, and a layer of plastic in between. Overall, composite walls and cylinders are used in a wide range of applications, including in the construction of buildings, in the design of industrial equipment, and in the production of energy storage systems. By optimizing the thermal performance of these structures, it is possible to achieve significant energy savings and to improve the overall efficiency of the system. Lecture Number: 08 Combined conduction Topics to cover: Combined conduction Combined conduction refers to the heat transfer process that occurs when multiple modes of conduction are present in a system. For example, in a composite wall made up of several layers of materials with different thermal conductivities, heat transfer occurs by conduction through each layer. The total heat transfer rate through the composite wall is the sum of the heat transfer rates through each layer. In cases where there is a combination of conductive, convective, and radiative heat transfer, the total heat transfer rate can be calculated using the overall heat transfer coefficient (U-value). The U-value is a measure of the overall heat transfer rate across the system and takes into account the thermal conductivities of the materials, the surface area of contact, and the temperature difference between the two sides of the system. P a g e 14 | 18  Fundamentals of Mechanical Engineering T2425103 Fig. Conducting wall with convective heat transfer Combined conduction can also occur in more complex systems, such as heat exchangers or electronic devices, where there are multiple layers or components through which heat transfer occurs. In such cases, the overall heat transfer rate can be determined by combining the individual heat transfer rates through each component using appropriate mathematical models. Overall, understanding combined conduction is important for the design and optimization of thermal systems, as it allows engineers to predict the heat transfer rates and to optimize the design for maximum efficiency. Lecture Number: 09 Topics to cover: Convection Convection Convection is a mode of heat transfer that occurs when a fluid, such as a gas or liquid, is in motion. In this the physical circulation of molecules takes place. The motion of the fluid can be caused by external forces, such as pumps or fans, or by natural convection due to temperature differences within the fluid. Convection can occur in a variety of forms, such as natural convection, forced convection, and mixed convection. The process of heat convection is due to ability of moving matter to carry heat energy. The transfer of heat by convection takes place between a solid surface and adjacent liquid or gas , which is in motion. The basic heat transfer equation is give by Newton’s Law of cooling: Q = h A ΔT in ‘Watts’ h = Convection heat transfer coefficient in ‘W/m2K’ A = Surface area in ‘m2’ P a g e 15 | 18  Fundamentals of Mechanical Engineering T2425103 ΔT = Temperature difference in ‘°C’ or ‘K’ Examples of Convection Heat transferred from hot flue gases to water for generating steam in boiler through boiler tubes. Heat lost from steam, while passing througl condenser. Due to heat rejected by steam to cooling water, steam gets cooled, condensed and converted into water Type of Convection Convection is classified into two types: (a) Free convection or Natural convection: Here, physical circulation takes place due to density difference. Examples of free convection: Flow of hot exhaust gases through a chimney of boiler (natural draught), Flow of hot air movement along the road in summer season. (b) Forced convection: Here physical circulation takes place with the use of mechanical devices such as pump, fan, blower etc As the velocity of circulation increases, rate of heat trasfer due to convection also in- creases. Therefore, rate of heat transfer in case of forced convection is more than free convection. Examples for forced convection: Condenser in steam power plant. Evaporator in refrigerating unit. Lecture Number: 10 Topics to cover: Radiation, application of heat transfer modes Radiation Radiation is the mode of transfer of heat through space by means of thermal radiations or electromagnetic waves. Radiation is due to the ability of matter either to emit or to absorb different kinds of electromagnetic radiation. Heat transfer by radiation between two bodies takes place without any carrying medium. P a g e 16 | 18  Fundamentals of Mechanical Engineering T2425103 This process is completed in following steps: Conversion of heat energy of hot body into electromagnetic waves in the form of succes- sive and separated pockets, is known as photons. These electromagnetic waves travel through the intervening medium like water, air or vacuum etc Conversion of electromagnetic waves again into heat energy, when waves strike the next body. Some part of heat energy will get absorbed by the body, few get reflected and remaining is transmitted through the body. Examples of radiation: Radiated energy from sun (hot body) to earth's surface (cold body). Dissipation of energy from a filament of a vacuum tube. Heat leakage through the walls of a thermos. Application of heat transfer modes Conduction Cooking Utensils: Metal pots and pans efficiently conduct heat from the stove to the food. Building Insulation: Materials with low thermal conductivity are used to reduce heat loss. Heat Sinks: Used in electronic devices to dissipate heat from components. Industrial Furnaces: High-conductivity materials are used for efficient heat transfer. Convection Heating Systems: Radiators and forced-air systems use convection to distribute heat in buildings. Cooling Systems: Air conditioners and refrigerators use convection to remove heat. Weather Patterns: Convection currents in the atmosphere drive wind and weather systems. Ovens: Convection ovens circulate hot air to cook food evenly. Radiation Solar Panels: Capture solar radiation and convert it into electricity. Infrared Heaters: Emit thermal radiation to heat objects and spaces. Thermal Imaging: Detects radiation to create images based on temperature differences. Spacecraft Thermal Control: Radiative cooling is used to manage heat in the vacuum of space. Each of these applications leverages the specific characteristics of conduction, convection, or radiation to transfer heat effectively in various contexts. P a g e 17 | 18 Fundamentals of Mechanical Engineering T2425103 P a g e 18 | 18