This is a sample class on Thermodynamics. It was created by Karo Okobiah (ookobia00@ccny.cuny.edu) as part of a research work. The goal of this sample class is to demonstrate how Wiki can be used as an effective instructional tool.
Sample Class Begins Here
Thermodynamics for Engineers
Goals:
The goal of this class is to introduce the basic concepts and principles of thermodynamics. It will also discuss and establish the 1st and 2nd laws of thermodynamics. The wiki website would also enhance the learning process by providing fundamental examples and applications of the laws of thermodynamics. By the end of the class, you should be able to define explicitly the laws of thermodynamics and apply them in solving basic engineering thermodynamic problems.
Topics include:
1. Concepts and Definitions
2. Work and Heat
3. The First Law of Thermodynamics
4. The Second Law of Thermodynamics
5. Applications of the laws of Thermodynamics
Concepts and Definitions[]
In this class, we will be introduced to the basic principles and fundamentals laws of thermodynamics. To understand these principles we need to define some basic terms that will be used throughout this class
Systems:
A system is a mass of something which is separated by a finite boundary. We have two types of systems; open and closed systems
Open systems:
An open system (system theory) is a system where matter or energy can flow into and/or out of, in contrast to a closed system, where no energy or matter may enter or leave. See also closed system.
Closed Systems
A closed system can exchange heat and work, but not matter, with its surroundings.
To understand and define a system we need to know its properties. These are divided into 2 forms: Extensive and Intensive properties.
Extensive properties include its Mass, volume and density
Intensive properties include its pressure and temperature and are not constant
To study a system we also need to study its equilibrum a state where the system does not change by itself. All thermodynamic problems are related to equilibrum systems.
Work & Heat[]
Heat:
Heat is a form of Energy that travels only when there is a difference in temperature
Work:
Work is the amount of heat transferred from a body.
First Law of Thermodynamics[]
The first law of thermodynamics is the application of the conservation of energy principle to heat and thermodynamic processes:
The change in internal energy of a system is equal to the heat added to the system minus the work done by the system
ΔU=Q+W.
Second Law of Thermodynamics[]
It is impossible to extract an amount of heat QH from a hot reservoir and use it all to do work W . Some amount of heat QC must be exhausted to a cold reservoir. This precludes a perfect heat engine.
This is sometimes called the "first form" of the second law, and is referred to as the Kelvin-Planck statement of the second law.
It is not possible for heat to flow from a colder body to a warmer body without any work having been done to accomplish this flow. Thermal energy will not flow spontaneously from a low temperature object to a higher temperature object. This precludes a perfect refrigerator. The statements about refrigerators apply to air conditioners and heat pumps, which embody the same principles.
Application of the Laws of Thermodynamics[]
Refrigerator A refrigerator is a heat engine in which work is done on a refrigerant substance in order to collect energy from a cold region and exhaust it in a higher temperature region, therby further cooling the cold region.
Refrigerators have made use of fluorinated hydrocarbons with trade names like Freon-12, Freon-22, etc. which can be forced to evaporate and then condense by successively lowering and raising the pressure. They can therefore "pump" energy from a cold region to a hotter region by extracting the heat of vaporization from the cold region and dumping it in the hotter region outside the refrigerator. The statements about refrigerators apply to air conditioners and heat pumps, which embody the same principles. Although this process works very well and has been in place for decades, the bad news about it is that fluorinated hydrocarbons released into the atmosphere are potent agents for the destruction of the ozone in the upper atmosphere. Therefore tighter and tighter restrictions are being placed on their use.