# Heat

## Stirling engine applications

The Stirling engine applications can be divided into three main categories:

• Mechanical propulsion
• Heating and cooling
• Power generation systems

A Stirling engine is a thermal engine that works by cyclic compression and expansion of air or other gas, the working fluid. During the Stirling cycle there is a net conversion of heat to mechanical work. The Stirling cycle engine also operates in reverse, using a mechanical energy input to drive the heat transfer in a reverse direction (ie, a heat pump or refrigerator).

Generation of electrical energy…

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## Joule effect

The Joule effect, also called Joule's law, is the thermal manifestation of electrical resistance. If electricity circulates in an electric conductor, a part of the kinetic energy of the electrons is transformed into heat due to the shock that the electrons experience with the molecules of the conductor through which they circulate, which increases the temperature of the conductor. It is named in honor of the English physicist James Prescott Joule.

Definition of the Joule effect:

The amount of heat energy produced by an electric current is directly proportional to the square of…

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## Difference between real and theoretical Otto cycles

Between the Otto real cycle and the corresponding theoretical Otto there are substantial differences. Some of these differences can be observed when comparing the diagram of the real cycle with the theoretical cycle diagram. The other differences that we are going to analyze refer to the differences between the temperature and pressure values of the two Otto engine cycles.

Differences in the form of the diagram

The difference in shape of the diagram between a real Otto cycle and a theoretical Otto cycle consists of a different profile in the expansion and compression curves, in…

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## Theoretical and real cycles Cycles

Cycles theoretical endothermic engines

For theoretical cycles, commonly used approaches aproximacióna by the real conditions are three:

• real cycle
• air cycle
• air-fuel cycle.

A theoretical these cycles are compared in practice the actual cycles, which are obtained experimentally by means of the indicators, for this reason, the actual cycle also indicated cycle is called.

Although the theoretical cycles do not correspond to actual cycles, provide a useful reference for the thermodynamic study of internal combustion engines,…

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## Theoretical diesel cycle

The theoretical diesel cycle is the theoretical cycle of a diesel engine, also known as a compression ignition engine.

The theoretical cycle of a thermal engine is a theoretical approximation of its operation to calculate its performance.

The cycle of an internal combustion engine is constituted by the physical and chemical transformations suffered by the fuel during its passage inside the engine.

The study of a real cycle taking into account all the numerous variables, represents a very complex problem. For this reason, it is usually simplified by resorting to theoretical…

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## Boiler. What is it and how it works?

A boiler is a container, or a set of tubes, used to heat water or other fluid. To heat the liquid can be used various fuels such as diesel, coal, biomass, etc. The most common are fossil fuels.

Operation and applications of a boiler

The boiler is a machine or apparatus is designed to heat water or other fluid, usually by combustion of a fuel such as gas, diesel, coal, biomass, etc. The hot or vaporized fluid leaves the boiler for use in different heating processes or applications, generation of motive power from steam, cooking or cleaning. The two most common boiler types are:

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## Stirling Cycle

The Stirling cycle is a thermodynamic cycle that describes the operation of a class of equipment (generating or operating machines). The cycle describes the original Stirling engine that was invented and patented in 1816 by the Reverend Robert Stirling, helped substantially by his brother engineer.

The Stirling engine is an external combustion engine. This characteristic differentiates it from other types of engines such as the otto engine or the diesel engine which are internal combustion engines. Both engines operate according to the otto cycle and the diesel cycle respectively.

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## Otto cycle

The theoretical Otto cycle is the ideal cycle of the Otto engine. The Otto engine is also known as a spark ignition engine because the ignition of the fuel is done through a spark caused by a spark plug. It is also known as a gasoline engine because of the type of fuel it uses.

One way to study the performance of this engine is by analyzing its theoretical cycle. The theoretical cycle is an approximation to the real cycle with many simplifications. In practice, there are so many variables that affect the performance of the engine that calculating the actual cycle is practically impossible.…

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## Comparison between the three theoretical cycles

To compare cycle just discussed, it is necessary to refer some of the factors whose value depends on the shape and surface, such as: the compression ratio, the maximum pressure, the amount of heat supplied and the heat subtracted useful work.

The following figure are plotted the curves of the ideal thermal performance variations by varying the ratio of co

RINTING for three cycles: Otto, Diesel and Sabathé. For Diesel cycles and Sabathé has chosen a constant pressure…

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## Types of engines

A motor or motor is a machine designed to convert a form of energy into mechanical energy . An engine can be classified into a category according to two criteria: the form of energy it accepts to create movement and the type of movement it produces.

As a general rule, engines have an axle, which in rotary offset and through mechanical devices such as drive gears. The exceptions are rocket motors and linear motors . Nowadays, combustion engines…

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## Analysis of a cycle and its thermal performance

Second law of thermodynamics

No real or ideal engine can turn all the heat introduced into mechanical work.

Therefore, only a fraction of the heat supplied by the combustion will be converted into work; This fraction represents the thermal performance of the engine. Then we define,

Ideal thermal performance

.

Relation between the amount of heat transformed into useful work and the amount of heat supplied to the fluid.

As useful work equals the difference between the supplied…

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## Refinery

An oil refinery is an industrial plant, of the oil raw material by purification and distillation under normal pressure and under vacuum in fractions with a defined boiling range transferred. The additional refinement of the boiling cuts is done by methods such as extraction or chemical cleaning methods. To increase the quality of products, such as their octane number, conversion processes such as isomerization or catalytic reforming are used. In addition, additives are added to products that improve or suppress certain properties.

Higher value products are obtained, such as gasoline,…

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## Types of heat engines

The heat engines can be classified in many different ways. Then classify heat engines, taking into account six different aspects:

• They Depending on where is combustion.
• Depending on the fuel used and the type of lighting.
• Depending on the movement of moving parts.
• Depending on how realizes the cycle.
• Depending on the number of cylinders
• Depending on the arrangement of the cylinders
Types of heat engines depending on where combustion takes place

Depending on where combustion takes place two types:

## Second law of thermodynamics

The second law of thermodynamics is a principle of classical thermodynamics that establishes the irreversibility of many thermodynamic events, such as the passage of heat from a hot body to a cold one. Unlike other laws of physics such as the law of universal gravitation or Maxwell's equations, the second principle is fundamentally linked to the arrow of time.

The second principle of thermodynamics has several equivalent formulations, one of which is based on the introduction of a state function, entropy: in this case the second principle states that the 'entropy of a system isolated…

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## Heat engine

Heat engines are a type of alternative engines. Actually, they are the most popular alternative engines.

This type of engine uses the thermal energy caused by the combustion of a fuel (usually gasoil or gasoline) to convert it into mechanical energy.

Heat Machines

The concept of a thermal engine is often confused with that of a thermal engine. These terms are related but not exactly the same. A thermal machine is a device or system that works by establishing exchanges of heat and work with its environment. To achieve this, the machine transforms a substance through a cyclic…

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## First law of thermodynamics

The first law of thermodynamics, also called by extension, the law of conservation of energy, is a fundamental assumption of the theory of thermodynamics.

The first law of thermodynamics is a formulation of the principle of conservation of energy and states that:

"The internal energy of an isolated thermodynamic system is constant."

A thermodynamic universe, which consists of the system and its environment, is an isolated system. Energy is not created or destroyed, but is transformed from one form to another: energy can be transferred through the exchange of heat (heat…

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## Sabathé mixed cycle

The actual operating conditions of diesel engines differ markedly from those that are represented in the ideal Otto and Diesel cycles. For diesel engines, the combustion process transformational approaches a constant pressure only in case of unusually large motors and slow.

The actual plot shows that, under normal conditions, the combustion takes place, in Diesel engines, according to a process that approximates a transformational combustion and a constant volume at pressures n…

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## Entropy

In classical thermodynamics, the first field in which entropy was introduced, S is a state function of a system in thermodynamic equilibrium, which, by quantifying the lack of availability of a system to produce work, is introduced together with the second principle of thermodynamics. On the basis of this definition, we can say, in an explanatory but not strict way, that when a system moves from a state of equilibrium it ordered a disordered one to increase its entropy; this fact provides indications about the direction in which a system evolves spontaneously.

Entropy and disorder

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## Parts and components of a heat engine

In this section we describe the different parts of a thermal engine. Of thermal engines have many types, however we will focus on the diesel engine and the gasoline engine (otto cycle).

Despite being different engines share many parts in common, so the scheme presented will serve to indicate the nomenclature of each element.

The most important elements of internal combustion engines, common to diesel and explosion engines, we classify them in two large groups:

• Fixed elements of a heat engine: block, cylinder head, crankcase.
• Moving parts of a heat engine:…

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## Currents of Foucault

Foucault currents are the currents induced in masses of conducting metal that are immersed in a variable magnetic field or that, in motion, through a constant or variable magnetic field. In any case, it is the variation of the magnetic flux that generates these currents. The phenomenon was discovered by the French physicist Jean Bernard Léon Foucault in 1851.

In high frequency: using cores with magnetic materials that have low electrical conductivity (such as ferrite).

Foucault currents create energy losses through the Joule effect. More specifically, these currents transform…

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The development of the Stirling engine started with the aim of being an alternative to the machine of value due to certain advantages that it had with respect to the then popular steam engine.

Over time, certain disadvantages compared to internal combustion engines have left the Stirling engine in the background.

Advantages of the Stirling engine compared to internal combustion engines

The main advantages of a Stirling engine compared to an otto engine, a diesel engine or a steam engine are:

• The maintenance facility
• They are quieter engines
• Stirling…

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## Stirling engine

The Stirling engine is an external combustion thermal engine. Originally it was conceived as an industrial main engine to compete with the steam engine, but in practice, for more than a century it was only used for domestic applications and for low power engines.

The Stirling engine was invented in 1816 by Robert Stirling, a Scottish priest. One of the concerns of the time was the safety of steam engines. Stirling's goal was to get a less dangerous engine than the steam engine.

The operation of the Stirling engine is based on the expansion and contraction of a gas that can be…

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## History of the diesel engine

The diesel engine was invented by Rudolf Diesel, in the year 1893. Rudolf Diese was a German engineer, employed by the firm MAN.

Rudolf Diesel studied high thermal efficiency engines, with the use of alternative fuels in internal combustion engines. Diese's goal was to replace the old steam engines that were inefficient, very heavy and expensive.

First steps before reaching the diesel engine

In 1806, brothers Claude and Nicéphore Niépce developed the first known internal combustion engine and the first fuel injection system. The two brothers tested systems…

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## Types of steam engines

Steam engines are mechanical devices capable of transforming heat energy into mechanical energy in a rotating axis. This heat energy takes advantage of the energy contained in water vapor at high pressure and temperature.

We consider steam engines all those machines that transform the thermal energy of a fluid into mechanical energy. In general, the fluid must be pre-heated and at the outlet of the steam machine it must be cooled to repeat the process.

Steam machines can be classified into these two types:

• Plunger steam engine
• Turbine steam engine

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## Thermodynamics

Thermodynamics is the part of physics that deals with the relationship between heat and work. It studies the effects of the variation of pressure, temperature and volume of a physical system (we understand by physical system a liquid, a material, a set of bodies, etc.), at a macroscopic level, that is to say, that can be observed.

The term thermodynamics comes from the stem therm, which means heat and dynamics that refers to movement. The movement of heat in a body.

Matter is composed of different particles that move in a disordered way (what is called entropy). Thermodynamics…

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## Chemical thermodynamics

Chemical thermodynamics is the study of the interrelation of heat and work with chemical reactions or with physical changes of state within the limits of the laws of thermodynamics. Chemical thermodynamics involves not only laboratory measurements of various thermodynamic properties, but also the application of mathematical methods to the study of chemical issues and the spontaneity of processes.

The structure of chemical thermodynamics is based on the first two laws of thermodynamics. From the first and second laws of thermodynamics, four equations called "fundamental Gibbs equations"…

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## Crankshaft definition

The crank shaft is the force that makes the whole rod-crank crank. Its function is to transform rotational movements in alternative movements (combustion engines, for example) or vice versa (Eccentric mechanical presses).

In the heat engine crankshaft collects forces originated during the explosion and turns through the rod, linear motion into rotary motion of the piston alternative. Transmits the movement and the driving force transmission elements that are coupled. Is subjected to bending and torsion efforts, and has a strong structure and very resistant. The crankshafts, which can…

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## Thermodynamic transformations

Thermodynamic transformation is a process by which a thermodynamic system passes from a state of thermodynamic equilibrium to another.

A thermodynamic system is in principle in a state of thermodynamic equilibrium when the main variables of the system (ie pressure, volume and temperature) do not experience any additional variation over time.

In the event that two or all of the above variables change (the variation of only one of them is impossible because they are all interconnected by an inverse or direct proportion ratio) we are in the presence of a thermodynamic transformation,…

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## Zeroth law of thermodynamics

The zeroth law of thermodynamics states that "if two bodies A and B are separately in thermal equilibrium with a third body C, then A and B are in thermal equilibrium with each other.

This law allows the definition of a temperature range, such as temperature scales Celsius, Fahrenheit, Kelvin, Réaumur, Rankine, Newton and Leiden.

Statement of the zeroth law of thermodynamics

The enunciation of the zeroth law of thermodynamics is defined as: Two systems in thermal equilibrium with a third are in equilibrium with each other.

The zeroth law of thermodynamics…

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## Cycles of the thermal engines

The operating system of the thermal engines is based on a cycle that is constantly repeated. In the case of internal combustion engines this cycle consists of the fuel input (admission), combustion of the fuel, expansion of the cylinder and expulsion of the gases produced. This cycle generates a mechanical movement, if the cycle repeats we will have a constant mechanical movement.

A thermal engine can work through many different cycles. In this section we will explain the different operating cycles that an internal combustion engine can have, the real cycles and the theoretical cycles.

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