Unit-1: Fundamentals of Thermodynamics
Unit-1: Fundamentals of Thermodynamics
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Thermal Engineering
Thermal Engineering
- Thermal Engineering is a branch of engineering that deals with the study, conversion, transfer, and utilization of thermal energy (heat) and its relationship with mechanical work.
Application Areas
Application Areas
- Automobile Industry: IC engines, EV thermal management, and cooling systems
- Power Plants: turbines, gas turbines, and other thermal systems
- HVAC Systems & Refrigeration: Refrigerators, air conditioners, heat pumps
- Furnaces, boilers, heat treatment, drying, and industrial heating systems.
- Aerospace Industry
- Renewable Energy
- Chemical & Process Industries – Heat exchangers, boilers, condensers, evaporators, and thermal processing.
Subjects Under Thermal Engineering Domain
Subjects Under Thermal Engineering Domain
1. Thermodynamics2. Heat Transfer3. Fluid Mechanics4. Applied Thermodynamics (IC Engines)5. Power Plant Engineering6. Turbo Machinery7. HVSC & Refrigeration8. Renewable Energy9. Energy Audit and Management10. Computational Fluid Dynamics (CFD)
Thermodynamics
Thermodynamics
- Branch of science which deals with study of conversion of heat into work.
- The study of thermodynamics is concerned with ways energy is stored within a body and how energy transformations may take place, which involve heat and work.
1. Microscopic Approach
1. Microscopic Approach
- It analyzes a system by studying the behavior of its individual constituent particles, such as atoms and molecules.
- also known as Statistical Thermodynamics
2. Macroscopic Approach
2. Macroscopic Approach
- It studies the large-scale, overall behavior of a system using directly observable and measurable properties without analyzing individual molecules.
- also known as Classical Thermodynamics.
Pure Substance
Pure Substance
- A pure substance is a substance that has a fixed chemical composition throughout the system, even if it exists in more than one phase.
- Examples: Water, nitrogen, oxygen, and carbon dioxide, mixture of water and steam.
Thermodynamic System
Thermodynamic System
- A thermodynamic system is a specified quantity of matter or a region in space selected for thermodynamic analysis.
Surrounding
Surrounding
- Everything outside the system is called the surrounding.
Boundary
Boundary
The real or imaginary surface separating the system from its surroundings is called the boundary.
Types of Systems
Types of Systems
- Open System
- Close System
- Isolated System
1. Open System
1. Open System
- In open system both mass and energy can cross the system boundary.
- Example: A turbine, compressor, pump, or boiler with fluid flowing through it.
2. Close System
2. Close System
- In closed system mass cannot cross the system boundary, but energy can cross the boundary in the form of heat and/or work.
- Example: Gas contained in a sealed piston-cylinder arrangement.
3. Isolated System
3. Isolated System
- In isolated system neither mass nor energy can cross the system boundary.
- Example: An ideal thermos flask (perfectly insulated and sealed).
State
State
- The state of a thermodynamic system is the condition of the system at a particular instant, described by its thermodynamic properties such as pressure, temperature, volume, and mass.
- Example: A gas at P = 2 bar, T = 300 K, and V = 0.5 m³ represents a particular state of the system.
Path
Path
- The path is the series of intermediate states through which a thermodynamic system passes during a process from one state to another.
- Example: A gas changing from state 1 to state 2 through a particular sequence of pressure and temperature changes follows a specific path.
Thermodynamic Properties
Thermodynamic Properties
- Thermodynamic properties are the measurable characteristics of a thermodynamic system that define its state.
- Examples: Pressure (P), Temperature (T), Volume (V), Internal Energy (U), Enthalpy (H), and Entropy (S).
- Heat and Work are not properties.
- Thermodynamic properties can be of two types
1. Intensive Property
1. Intensive Property
- Intensive properties are thermodynamic properties that do not depend on the mass or size of the system.
- Examples: Temperature, Pressure, Density, Specific Volume, and Specific Enthalpy.
2. Extensive Property
2. Extensive Property
- Extensive properties are thermodynamic properties that depend on the mass or size of the system.
- Examples: Mass, Volume, Internal Energy, Enthalpy, and Entropy.
Important points regarding Property
Important points regarding Property
- Ratio of two extensive properties always intensive. Example: Density
- Specific quantities are always intensive. Example: Specific Volume
- It is state function.
- It is independent on past history.
- It is exact differential.
Process
Process
- A thermodynamic process is the change of a system from one state to another state.
- Example: Expansion of a gas from an initial state to a final state.
1. Reversible Process
1. Reversible Process
- A reversible process is a process that can be reversed in direction by an infinitesimal change in conditions, so that both the system and surroundings return exactly to their initial states without any net effect.
- Example: Slow, frictionless expansion or compression of a gas.
2. Irreversible Process
2. Irreversible Process
- An irreversible process is a process that cannot be completely reversed to restore both the system and surroundings to their initial states without leaving any net effect.
- Examples: Friction, free expansion of gas, mixing of two fluids, and heat transfer through a finite temperature difference.
Cycle
Cycle
- A thermodynamic cycle is a series of thermodynamic processes in which the system returns to its initial state.
- Example: The processes in a steam power plant form a thermodynamic cycle.
State postulate
State postulate
- The state postulate states that the state of a simple compressible system is completely specified by two independent intensive properties.
- Example: For a gas, if pressure (P) and temperature (T) are known, its state can be determined.
1. Point function
1. Point function
- When two properties locate a point on the graph then those properties are called as point function.
- A point function is a thermodynamic property whose value depends only on the state of the system and is independent of the path followed to reach that state.
- Examples: Pressure, Temperature, Volume, Internal Energy, Enthalpy, and Entropy.
2. Path function
2. Path function
- There are certain quantities which cannot be located on a graph by a point but are given by the area on that graph. In that case, the area on the graph, pertaining to the particular process, is a function of the path of the process. Such quantities are called path functions.
- A path function is a thermodynamic quantity whose value depends on the path followed by the system during a process and not only on the initial and final states.
- Examples: Heat and Work.
Quasi-static process
Quasi-static process
- A quasi-static process is a thermodynamic process that occurs infinitely slowly through a continuous sequence of equilibrium states, so that the system remains nearly in thermodynamic equilibrium at every stage.
- Example: Very slow compression of a gas in a piston-cylinder by gradually adding small weights on the piston.
Thermodynamic equilibrium
Thermodynamic equilibrium
- Equilibrium is a state of balance where no unbalanced forces are present within the system.
- Thermodynamic equilibrium is the state of a system in which the system is simultaneously in thermal, mechanical, and chemical equilibrium.
- Thermal equilibrium: Temperature is uniform throughout the system.
- Mechanical equilibrium: No unbalanced pressure forces exist.
- Chemical equilibrium: No chemical reaction or mass transfer occurs within the system.
Questions
Questions
1. Explain the macroscopic and microscopic approaches to thermodynamic analysis.
2. Define a thermodynamic system, surroundings, boundary, and control volume.
3. Explain the different types of thermodynamic systems with suitable examples.
4. Define state, path, process, and cycle. Explain each with suitable examples.
5. Explain the state postulate. What is its significance in determining the state of a thermodynamic system?
6. Differentiate between point function and path function. Also explain quasi-static process and thermodynamic equilibrium.
2. Define a thermodynamic system, surroundings, boundary, and control volume.
3. Explain the different types of thermodynamic systems with suitable examples.
4. Define state, path, process, and cycle. Explain each with suitable examples.
5. Explain the state postulate. What is its significance in determining the state of a thermodynamic system?
6. Differentiate between point function and path function. Also explain quasi-static process and thermodynamic equilibrium.
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