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Contents:
Contents:
Thermodynamics and energy - Applications
Systems and control volume, properties of a system, continuum, state and equilibrium
Zeroth law, First Law of Thermodynamics - Statement and application
Steady flow energy equation & Numerical Problems
Second law of Thermodynamics – Kelvin - Plank statement and Clausius statement
Heat Engine, Refrigerator and Heat Pump
Third law of Thermodynamics - Statement
Lecture 16: ( 22 Sep 2023)
Thermodynamics and Energy, Applications, Systems and control volume, properties of a system, continuum, state and equilibrium
Thermodynamics is a branch of physics that deals with the relations between heat, work, and temperature, and the physical properties of matter that are affected by these quantities.
Energy: Energy is the ability to do work. There are many different forms of energy, including heat, work, and potential energy.
Heat: Heat is the transfer of energy between two bodies due to a difference in temperature.
Work: Work is the transfer of energy between a system and its surroundings by the application of a force.
Temperature: Temperature is a measure of the average kinetic energy of the particles in a system.
Pressure: Pressure is the force per unit area exerted by a system on its surroundings.
Volume: Volume is the amount of space occupied by a system.
Mass: Mass is the amount of matter in a system.
Entropy: Entropy is a measure of the disorder of a system.
Equilibrium is a state in which the properties of a system do not change with time.
Thermodynamics has a wide range of applications, including:
The design of engines and other heat engines.
The study of the atmosphere and climate.
The design of refrigerators and other heat pumps.
The study of chemical reactions.
The study of biological systems.
A system is a collection of matter and energy that is being studied.
A control volume is a portion of a system that is selected for study.
The boundary of a control volume separates the control volume from the rest of the universe.
The boundary is the wall that separates the system and the environment.
Everything outside the boundary is the surroundings.
Work or heat can be transferred across the system boundary.
Properties of a System:
Intensive Properties - The properties that are independent of the size of the system.
Example: Pressure, Temperature, Density, Viscosity
Properties of a System:
Extensive Properties - The properties that are dependent of the size of the system.
Example: Specific Volume. Internal Energy
An open system is one that freely allows both energy and matter to be transferred in an out of a system.
For example, boiling water without a lid.
Heat escaping into the air.
Steam (which is matter) escaping into the air.
A closed system, on the other hand, does not allow the exchange of matter but allows energy to be transferred.
Example of a closed system – a pressure cooker.
Heat is also transferred to the surroundings
Steam is not allowed to escape
An isolated system is completely sealed, Neither matter nor heat can transfer to or from the surroundings.
Example – A thermo flask.
The purpose of a thermo flask is to keep your food warm.
A thermo flask can be considered an isolated system but only for a short period of time.
It prevents both heat and matter from being transferred to the surrounding.
Application Area of Engineering Thermodynamics
Application Area of Engineering Thermodynamics
Lecture 17: ( 27 Sep 2023)
Zeroth law and First Law of Thermodynamics - Statement and applications
Zeroth Law of Thermodynamics:
"The Zeroth Law Sates that if two systems are in thermal equilibrium with a third system, they are also in thermal equilibrium with each other"
Some examples of the applications of the zeroth law of thermodynamics are,
A thermometer can be used to measure the temperature of a system by placing it in thermal equilibrium with the system.
A refrigerator can be used to remove heat from a system by transferring it to another system at a lower temperature.
A heat engine can be used to convert heat into work by transferring heat from a system at a higher temperature to a system at a lower temperature.
First Law of Thermodynamics: Law of Conservation of Energy
"The first law of thermodynamics states that energy can neither be created nor destroyed, but can only be transferred from one form to another"
The first law of thermodynamics can be expressed mathematically as follows:
ΔU = Q + W
where,
ΔU is the change in internal energy of the system,
Q is the heat transferred to the system, and
W is the work done by the system.
Some of the applications of the first law of thermodynamics are,
The design of engines: The first law of thermodynamics is used to design engines that convert heat into work.
The design of refrigerators: The first law of thermodynamics is used to design refrigerators that remove heat from a system and transfer it to its surroundings.
The study of chemical reactions: The first law of thermodynamics is used to study chemical reactions to determine the amount of energy that is released or absorbed during the reaction.
Two thermometers, A and B, are placed in thermal contact with each other. After a while, the temperature of thermometer A is 20 °C and the temperature of thermometer B is 20 °C. What can you say about the initial temperatures of the thermometers?
According to the zeroth law of thermodynamics, if two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other. In this case, both thermometers A and B are in thermal equilibrium with each other, so they must have the same temperature. Therefore, the initial temperatures of the thermometers must have been the same.
2. A cup of hot coffee is placed on a table. After a while, the temperature of the coffee is 25 °C and the temperature of the table is 25 °C. What can you say about the direction of heat flow?
According to the zeroth law of thermodynamics, if two systems are in thermal equilibrium with each other, there is no net heat flow between them. In this case, both the coffee and the table are in thermal equilibrium with each other, so there is no net heat flow between them. This means that the heat flow between the coffee and the table is equal in both directions.
Lecture 18: ( 29 Sep 2023)
Steady flow energy equation & Numerical Problems
The steady flow energy equation (SFEE) is a mathematical equation that describes the conservation of energy in a fluid flow system. It is a simplified form of the first law of thermodynamics applied to steady flow systems.
The SFEE can be used to analyze a wide variety of fluid flow systems, including pipes, channels, and nozzles. It can be used to calculate the pressure drop, flow rate, and temperature changes in a fluid flow system
Some of the assumptions made in the steady flow energy equation:
The flow is steady. This means that the flow conditions do not change with time.
The flow is incompressible. This means that the density of the fluid does not change with the change in pressure or temperature.
The flow is adiabatic. This means that there is no heat transfer between the fluid and its surroundings.
The flow is frictionless. This means that there is no friction between the fluid and the walls of the pipe or channel.
The SFEE can be stated mathematically as follows:
h1 + ke1 + pe1 + Q = h2 + ke2 + pe2 + W
Where
h is the specific enthalpy, which is the sum of the internal energy and the pressure energy of the fluid.
ke is the specific kinetic energy, which is the energy of the fluid due to its motion.
pe is the specific pressure energy, which is the energy of the fluid due to its pressure.
Q is the heat transfer, which is the energy transferred to the fluid from its surroundings.
W is the work done, which is the energy transferred from the fluid to its surroundings.
The subscripts 1 and 2 refer to the inlet and outlet conditions of the system.
1. A water jet enters a nozzle with a velocity of 10 m/s and a pressure of 100 kPa. The nozzle discharges into the atmosphere. Determine the velocity of the water jet at the nozzle exit.
1. A water jet enters a nozzle with a velocity of 10 m/s and a pressure of 100 kPa. The nozzle discharges into the atmosphere. Determine the velocity of the water jet at the nozzle exit.
The velocity of the water jet at the nozzle exit is 14.14 m/s.
2. A pump is used to lift water from a reservoir to a height of 10 m. The water enters the pump at a pressure of 100 kPa and a velocity of 2 m/s. The water exits the pump at a pressure of 200 kPa and a velocity of 5 m/s. Determine the power required to operate the pump.
2. A pump is used to lift water from a reservoir to a height of 10 m. The water enters the pump at a pressure of 100 kPa and a velocity of 2 m/s. The water exits the pump at a pressure of 200 kPa and a velocity of 5 m/s. Determine the power required to operate the pump.
The power required to operate the pump is 9900 W.
Lecture 19: (04 Oct 2023)
Second law of Thermodynamics – Kelvin - Plank statement and Clausius statement, Third law of Thermodynamics
Second law of Thermodynamics
Third law of Thermodynamics
The second law of thermodynamics is a fundamental law of physics that states that the entropy of an isolated system always increases over time.
The third law of thermodynamics states that the entropy of a system approaches a constant value as the temperature approaches absolute zero
Second law of Thermodynamics
Entropy is a measure of disorder, so the second law of thermodynamics is essentially saying that the universe becomes more disordered over time.
There are several different ways to state the second law of thermodynamics, but one of the most common is:
Heat cannot spontaneously flow from a colder body to a hotter body.
This statement means that heat always flows from hot to cold, and it cannot be reversed without doing work. For example, if you put a hot cup of coffee in a cold room, the coffee will cool down over time. The heat from the coffee will flow into the room, making the room warmer and the coffee colder. However, the coffee will never spontaneously heat up again.
Another way to state the second law of thermodynamics is:
It is impossible to construct a device that operates on a continuous cycle and produces no other effect than the transfer of heat from a cooler to a hotter body.
This statement is known as the Kelvin-Planck statement of the second law of thermodynamics. It means that it is impossible to create a perpetual motion machine, which is a machine that would run forever without using any energy.
Here are some examples of the second law of thermodynamics in action:
A car engine converts some of the chemical energy in gasoline into mechanical energy, but it also produces heat as a byproduct. The heat energy is lost to the environment, and it cannot be fully converted back into mechanical energy.
A refrigerator uses electricity to move heat from the inside of the refrigerator to the outside. The heat energy is transferred to the outside environment, and it cannot be fully recovered.
Living organisms must constantly use energy to maintain their complex structures. Over time, all living organisms eventually die and decay, and their complex structures are lost.
Third law of Thermodynamics
The third law of thermodynamics is important because it helps us to understand the behavior of matter at very low temperatures. For example, it can be used to explain why some materials, such as superconductors, exhibit unusual properties at very low temperatures.
The third law of thermodynamics also has implications for the universe as a whole. It tells us that the universe is constantly becoming more disordered, and that it is impossible to reach a state of perfect order.
Here are some examples of the third law of thermodynamics in action:
A superconductor is a material that loses all electrical resistance at very low temperatures. This is because the electrons in a superconductor are able to move freely without any resistance. The third law of thermodynamics helps us to understand why superconductivity only occurs at very low temperatures.
A Bose-Einstein condensate is a state of matter that occurs when a gas of bosons is cooled to very low temperatures. In a Bose-Einstein condensate, the bosons all occupy the same quantum state. The third law of thermodynamics helps us to understand why Bose-Einstein condensates only occur at very low temperatures.
The third law of thermodynamics is a fundamental law of physics, and it has a profound impact on our understanding of matter and the universe.
It is important to note that the third law of thermodynamics only applies to perfect crystals. In real materials, there are always defects and impurities, which means that the entropy of a real material at absolute zero will not be zero. However, the third law of thermodynamics still provides a useful framework for understanding the behavior of matter at very low temperatures.
Lecture 20: (06 Oct 2023)
Heat Engine, Refrigerator and Heat Pump
Heat Engine
Refrigerator
Heat Pump
A heat engine is a device that converts heat into work. It does this by transferring heat from a hot reservoir to a cold reservoir. The amount of work that can be done by a heat engine is limited by the difference in temperature between the hot and cold reservoirs.
A refrigerator is a device that transfers heat from a cold space to a hot space. It does this by using mechanical work to move the heat. The amount of work that must be done by a refrigerator is greater than the amount of heat that is transferred to the hot space.
A heat pump is a device that can transfer heat from a cold space to a hot space, or vice versa. It can do this by using mechanical work to move the heat. The amount of work that must be done by a heat pump is less than the amount of heat that is transferred to the hot space.
The main difference between a heat engine, refrigerator, and heat pump is the direction of heat transfer. A heat engine transfers heat from a hot reservoir to a cold reservoir, while a refrigerator transfers heat from a cold space to a hot space, and a heat pump can transfer heat in either direction.
Heat Engine
A heat engine is a device that converts heat energy into mechanical energy, which can then be used to do work. All heat engines operate on a basic cycle, which consists of four steps:
Compression: A working fluid is compressed, which increases its temperature.
Heat addition: Heat is added to the working fluid, which further increases its temperature and pressure.
Expansion: The working fluid expands, which does work on the engine's components.
Heat rejection: Heat is rejected from the working fluid, which reduces its temperature and pressure.
The efficiency of a heat engine is defined as the ratio of the work output to the heat input. The efficiency of a heat engine is limited by the second law of thermodynamics, which states that no heat engine can be perfectly efficient.
Types of heat engines
There are many different types of heat engines, each with its own advantages and disadvantages. Some common types of heat engines include:
Internal combustion engines: Internal combustion engines are used in cars, trucks, and other vehicles. They burn fuel to heat a working fluid, which then drives the engine's pistons.
Steam engines: Steam engines were once widely used in power plants and locomotives. They use heat to boil water into steam, which then drives the engine's pistons.
Gas turbines: Gas turbines are used in jet engines and power plants. They use a compressor to compress air, which is then heated and used to drive the engine's turbines.
Lecture 21: ( 09 Oct 2023)
Tutorial on Second and Third Law of Thermodynamics
In-Semester Evaluation : Activity Based Assessment
In-Semester Evaluation : Activity Based Assessment
Activity 6: "Exhibition for School Children on Demonstration of Zeroth, First, Second and Third Law of Thermodynamics"
Due Date: 20 Oct 2023 (Friday)
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