Definition of Thermodynamic Terms
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 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 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.
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.
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 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 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 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.
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.
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 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 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.
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.