MEG 212 Lecture 1 (2024) Engineering Thermodynamics
- 1. INTRODUCTORY CONCEPTS AND DEFINITIONS MEG 212 Week 1 Lecture
- 2. At the end of this lecture, you will be able to, • Discuss the importance of thermodynamics in meeting human needs • Identify application areas of thermodynamics • Discuss the differences between closed and open systems • Define fundamental concepts used in thermodynamic analysis such as property, state and process • Identify the difference between the macroscopic and microscopic views of thermodynamics Lecture Learning Outcomes
- 3. What is Thermodynamics? It is the science concerned with the relations between heat and mechanical energy or work, and the conversion of one into the other From two Greek Words • “Therme” meaning Heat • “Dynamis” meaning Motion or Power
- 4. Importance of Thermodynamics? 21st Century Challenges • Using fossil fuels more effectively • Advancing renewable energy technologies • Developing more energy-efficient transportation systems, buildings and industrial practices • Mitigating global climate change, air pollution and water pollution Engineers use principles drawn from thermodynamics and other engineering sciences which include fluid mechanics, heat & mass transfer to analyze and design devices used to meet human needs
- 5. Application Areas of Engineering Thermodynamics Combustion systems Compressors & Pumps Cooling of electronic equipment Heating, ventilating and air-conditioning systems Steam and gas turbines Aircraft and rocket propulsion Alternative energy systems Automobile engines Bioengineering applications Biomedical applications
- 6. Application Areas of Engineering Thermodynamics
- 7. System, Boundary and Surrounding For example, we may want to study a quantity of matter contained within a closed rigid-walled tank or a pipeline through which natural gas flows The system is whatever we want to study which could be as simple as a free body diagram or as complex as an entire chemical refinery In thermodynamics, the system is used to identify the subject of analysis
- 8. System, Boundary and Surrounding The system is distinct from the surrounding by means of a specified boundary Everything external to the system is considered to be part of the system’s surroundings
- 9. Difference between Closed and Open Systems There are two basic kinds of system – the closed system and the open system (also called the control volume) Closed system: A gas in a piston-cylinder assembly • Fixed quantity of matter. • Also called control mass. • It is defined when a particular quantity of matter is under study • A closed system always contains the same matter • There can be no transfer of mass across its boundary • When a closed system does not interact with its surrounding in any way it is called an isolated system
- 10. Difference between Closed and Open Systems Open system: An automobile engine • A given region of space through which mass flows • Also called control volume
- 11. How to select a System Boundary? • The system boundary needs to be carefully specified before any thermodynamic analysis • The choice of a system boundary is governed by two considerations What is known about a possible system at its boundaries The objective of the analysis
- 12. Macroscopic Versus Microscopic View of Thermodynamics Microscopic view Sometimes called statistical thermodynamics Objective is to characterize by statistical means the average behavior of particles making up the system of interest Macroscopic view Sometimes called classical thermodynamics Concerned with the gross or overall behavior of the system For this course, we are adopting the macroscopic view point
- 13. Property, State and Process State Refers to the condition of a system described by its properties. When any of the properties of the system changes, the state changes and the system is said to undergo a process Property Is a macroscopic characteristic of a system such as mass, volume, energy, pressure, and temperature to which a numerical value can be assigned at a given time without knowledge of the previous behavior of the system To describe a system and predict its behavior requires knowledge of the system properties and how they are related
- 14. Property, State and Process Extensive and Intensive Properties Extensive: depend on the size of the system e.g. mass, volume, energy etc. Intensive: values are independent of the size of the system e.g. specific volume, pressure, temperature etc. Process Is a transformation from one state to another. If a system exhibits the same values of its properties at two different times, it is in the same state at these times. If none of the properties change with time then the system is said to be at steady state A quantity is a property if and only if its change in value between two states is independent of the process.
- 15. Equilibrium To test for thermodynamic equilibrium 1. Isolate the system from its surroundings 2. Watch for changes in its observable properties 3. If there are no changes, it is concluded Several types of equilibrium must exist individually to fulfill the condition of complete equilibrium Mechanical, Thermal, Phase, Chemical
- 16. SUMMARY 1 2 3 4 5 6 Definition Application Areas Importance Macroscopic and Microscopic Views System Boundary Surrounding Property State Process
- 17. Reading assignment: pages 11 to 14, 18/19 to 22 Measuring Mass, Length and Time: S.I Units and British Metric Units Rankine and Kelvin Temperature scales Celcius and Fahrenheit scales Engineering Design Next Lecture