# How is thermodynamics used in practical applications

## Technical thermodynamics

### 1. Introduction and definitions

The word thermodynamics is made up of the Greek terms therme (heat) and dynamis (force). Thermodynamics is a branch of thermodynamics and deals with the conversion of various forms of energy, in which the energy form heat is included.
Peter von Böckh, Matthias Stripf

### 2. Properties of the substances

The transfers of energies and masses to or from a system can be described by the property of its limits, but not indicate the change in its properties. In technical thermodynamics, we can limit ourselves to defining the state on macroscopically detectable properties and thus describe the properties of a system with a few parameters. These parameters, which macroscopically define the behavior of the system, are the state variables.
Peter von Böckh, Matthias Stripf

### 3. First law of thermodynamics

The first law of thermodynamics is a general law of conservation of energy. In order to be able to formulate the energy conservation laws for closed and open systems, one must first list and discuss the required types of energy.
Peter von Böckh, Matthias Stripf

### 4. Second law of thermodynamics

With the first law, energy conversions can only be partially analyzed. An example of this is that, according to the energy balance, heat could be transferred from a colder to a warmer body without any aid. However, such behavior is contrary to experience; that is, it has never been observed. According to the first law, one could convert heat completely into mechanical work, which, as experience shows, is again impossible. In order to determine the direction of thermodynamic processes and the quantity of convertible parts of energies, one needs the second law. In addition to the generally valid formulations of the second main clause, the state variable entropy is introduced for the mathematical description.
Peter von Böckh, Matthias Stripf

### 5. Energy, exergy and anergy

In view of today's environmental problems, the importance of optimal use of existing, non-renewable energy sources (oil, natural gas, coal and uranium) need not be explicitly emphasized. The exergy analysis, like the one in Chap. 4 presented entropy balancing, an excellent tool in the development of systems with more efficient use of energy resources, as it can show exactly the reasons and also the real size of thermodynamic losses. With the results of the analysis, thermodynamic systems with better efficiencies are realized and possibilities are shown how the efficiencies of inefficient systems can be improved. The exergy analysis provides the same thermodynamic results as the entropy balance, but in a more clear representation.
Peter von Böckh, Matthias Stripf

### 6. Use in technical processes

In the case of technical problems, the actual changes in state are usually so complex that an exact thermodynamic analysis is only possible with complex computer programs. The description of such programs would go beyond the scope of this textbook. In order to be able to make basic statements about influencing variables, simplified analyzes are often sufficient. Some simple, idealized state changes that are applicable to the analysis of technical processes are discussed here. In the chap. 7 to 10 then follows a more detailed treatment of the most important technical processes.
Peter von Böckh, Matthias Stripf

### 7. Steam turbine processes

A steam turbine system converts primary energy into usable mechanical work or electrical energy. Over 80% of electrical energy worldwide is generated with steam turbine systems. The heat supplied to the process comes from various sources: from the energy of solid, liquid or gaseous fuels, nuclear reactor heat, waste incineration, waste heat from industrial processes or gas turbines, geothermal and solar heat.
Peter von Böckh, Matthias Stripf

### 8. Gas turbine and gas engine processes

The power machines in which the working fluid remains gaseous during the entire process are summarized in gas processes. Refrigeration machine and heat pump gas processes are discussed in Chap. 9 discussed.
Peter von Böckh, Matthias Stripf

### 9. Chiller and heat pump processes

Chillers are used in households, in breweries, in the food industry, in refrigerated transport and in air conditioning systems. Another application is the low-temperature technology for air separation and the extraction of liquefied gases.
As an environmentally friendly heating alternative, heat pumps are enjoying increasing popularity. The use of a combined refrigeration system / heat pump is an energetically sensible solution, particularly where there is a need for cooling and heating at low temperatures.
Peter von Böckh, Matthias Stripf

### 10. Humid air

The air practically always contains a certain amount of water, either as a gas (water vapor) or in the form of mist droplets or ice crystals. Because of possible phase changes, humid air with or without droplets of mist or ice crystals is a mixture of special properties. If all components are gaseous, the mixture is treated as an ideal gas.
Peter von Böckh, Matthias Stripf

### 11. Combustion processes

We receive most of the primary energies used today in the form of fuels, of which fossil fuels make up the largest share. The heat generated during combustion was previously treated as supplied heat. This chapter deals with the chemical balance equations of combustion, the calculation of the composition of the combustion products and their thermodynamic properties.
Peter von Böckh, Matthias Stripf

### 12. Calculation of material properties

For the calculation of examples or processes, you need the physical properties that can change during a process. Many physical properties are given in the book. In chap. 2.6.2, references to material value programs and tables are listed.
Peter von Böckh, Matthias Stripf