Definition of Thermodynamic Terms


Energy:
Energy is an inherent property of a system. Any system at a given set of conditions (eg. Pressure and Temperature) has a certain energy content. The concept of energy was invented to describe a number of processes such as conversion of work to heat. The SI unit of energy is the joule (J). It can also be expressed as 1 kcal = 4186.8 J

Sensible Heat:
Sensible heat is defined as the heat energy stored in a substance as a result of an increase in its temperature. The SI units are expressed as kJ/kg.

Latent Heat:
Latent heat is defined as the heat which flows to or from a material without a change in temperature. The heat will only change the structure or phase of the material. e.g. melting or boiling of pure water. The SI units are expressed as kJ/kg.

Internal Energy:
The internal energy of the system is the energy of the system due to its thermodynamic properties such as pressure and temperature. The change of internal energy of a system depends only on the initial and final stages of the system and not in any way by the path or manner of the change. This concept is used to define the first law of thermodynamics.

Spesific Volume:
The spesific volume, v, of a system is the volume occupied by the unit mass of the system. The relationship between the spesific volume and density is v=1/p
The SI unit of spesific volume is m3/kg

Entropy:
Entropy of a system is a measure of the availability of its energy. A system with high entropy can do less usefull work. This concept was formally used to define the second law of thermodynamics. The SI unit of entropy is kJ/kg.K.

Enthalpy:
Enthalpy of a system is a measure of the total energy of a thermodynamic the system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure. The SI unit of enthalpy is kJ/kg.

Temperature:
Temperature is a measure of hotness and can be related to the kinetic energy of the molecules of a substance. A number of physical phenomena can be used for measuring the temperature of an object.

Pressure:
The pressure of a system is defined as the force exerted by the system on a unit area of its boundaries. This is the definition of absolute pressure. Often in pressure measurements a gauge is used to record the pressure difference between the system and the atmospheric pressure this is called gauge pressure.

State of Working Fluid
The working fluid is the matter contained within the boundaries of a system. Matter can be solid, liquid, vapour, or gasseous phase. The working fluid in applied thermodynamic problems is either approximated by perfect gas or a substance which exists as liquid and vapour. The state of working fluid is defined by certain characteristics known as properties. Some of properties which are important in thermodynamic problems are pressure, temperature, spesific enthalpy, spesific entropy, spesific volume, spesific internal energy.

Rankine Cycle:
The Rankine cycle is a heat with a vapour power cycle. The common working fluid is water. The cycle consist of four processes: isentropic expansion (Steam Turbine), isobaric heat rejection (Condenser), isentropic compression (Feed Pump), isobaric heat supply (Boiler).

Turbines:
Turbines are devices that convert mechanical energy stored in a fluid into rotational mechanical energy. These machines are widely used for the generation of electricity.

Steam Turbines:
Steam turbines are devices which convert the energy in steam into rotational mechanical energy. The steam turbine may consist of several stage. Each stage can be describes by analysing the expansion of the steam from the higher pressure section of the turbine to the lower section. The condition of the steam may be wet, dry saturated or superheated.

Related Books:

Now in its seventh edition, Fundamentals of Thermodynamics continues to offer a comprehensive and rigorous treatment of classical thermodynamics, while retaining an engineering perspective. With concise, applications-oriented discussion of topics and self-test problems the text encourages students to monitor their own comprehension. The seventh edition is updated with additional examples, homework problems, and illustrations to increase student understanding.


A focused look at the principles and applications of thermodynamics

Offering a concise, highly focused approach, Sonntag and Borgnakke's Introduction to Engineering Thermodynamics, 2nd Edition is ideally suited for a one-semester course or the first course in a thermal-fluid sciences sequence.

Based on their highly successful text, Fundamentals of Thermodynamics, Introduction to Engineering Thermodynamics, 2nd Edition covers both fundamental principles and practical applications in a more student-friendly format. The authors guide students, from readily measured thermodynamic properties through basic concepts like internal energy, entropy, and the first and second laws, up through brief coverage of psychrometrics, power cycles, and an introduction to combustion and heat transfer.

Back to Top

What is Thermodynamics?


What is thermodynamics? In briefly, thermodynamics is the study of energi and its transformation. It studies and interrelates the macroscopic variables, such as temperature, volume and pressure.

There are 4 laws of thermodynamics, zeroth, first, second, and third law of thermodynamics.

Zeroth law of thermodynamics: If two systems are each in thermal equilibrium with a third, they are also in thermal equilibrium with each other.

First law of thermodynamics: A change in the internal energy of a closed thermodynamic system is equal to the difference between the heat supplied to the system and the amount of work done by the system on its surroundings.

Second law of thermodynamics: Heat cannot spontaneously flow from a colder location to a hotter location.

Third law of thermodynamics: As a system approaches absolute zero, all processes cease and the entropy of the system approaches a minimum value.

Actually, to understand more simple about thermodynamics lets focus on the first and the second law of thermodynamics. If you have already read above about this law, you know that they have to do with energy, the first explicity, and the second emplicity.

The first law says that energy is conserved. That's all; you don't get something for nothing. The second law says that even within the framework of conservation, you can't have it just any way you might like it.

Related book:

If you want to understand thermodynamics with simply way, this book is the answer. Language is informal, examples are vivid and lively, and the perspectivie is fresh. Based on lectures delivered to engineering students, this work will also be valued by scientists, engineers, technicians, businessmen, and anyone else. But if you want to understand thermodynamics deeper, better if you use this book: Fundamentals of Engineering Thermodynamics. Even it's more expensive, this book maintains its engaging, readable style while presenting a broader range of applications that motivate student understanding of core thermodynamics concepts.

Back to Top

Applied Thermodynamics

Applied thermodynamics is the science of the relationship between heat, work, and system that analyse energy process. The process is to convert heat energy from available source such as chemical fuels into mechanical work.

This fundamental science is the basic thermodynamics process that is used in the steam power plant. The related topics are:

1. Laws of thermodynamics (zeroth, first, and second law)
2. Definition of: energy, power, enthalpy, entropy, temperature, pressure, specific volume, density, sensible heat, latent heat, thermal conductivity, mass flow, heat engines, turbines, steam turbine, gas turbine, compressor, thermodynamic cycle, working fluid, ideal gas, system.
3. Definition of processes: isobaric, isothermal, isentropic, isometric, adiabatic.
4. Heat transfer: heat exchanger, condenser, heat flow through a pipe.

I'll explain each topics next, but if you want to know further detail of it, you may read this books:
Or this one:

Both book have advantage and disadvantage of each. The first book Dictionary of Engineering (Second Edition) is general for all engineering science include mechanical, civil, architech, ect. It has pronounciation guide for every term; acronyms, cross-references, and abbreviations; appendices with conversion tables; listings of scientific, technical, and mathematical notation; tables of relevant data; and more.

The other one, Dictionary of Mechanical Engineering, focuss only on mechanical engineering term. It is powerfull with the newest terms of mechanical engineering, include the rapidly advancing areas of 'small size' mechanical engineering: micromachining and nanotechnology.

Back to Top