# Cold

## Second Law Of Thermodynamics

According to the first law of thermodynamics, every process that occurs in a given system must satisfy the principle of conservation of energy, including the flow of heat.

Equation:

states, in other words, that any process whose sole purpose is to create or destroy energy, is impossible, that is, it denies the existence of a first-class perpetual motion machine.

However, the first law does not tell us anything about the…

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## Components Of A Solar Thermal Installation

The function of a solar thermal installation is to take advantage of solar energy to generate heat. The solar panels of these facilities capture the heat of the solar radiation that falls on them to heat a fluid. The different ways to take advantage of this hot fluid allows us to use this type of renewable energy in multiple applications.

A solar thermal installation consists of:

• Solar collectors
• Primary and secondary circuits
• Heat exchanger
• Accumulator, pumps
• Glass of expansion
• Pipelines
• Main control panel.

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## Heat

In physics, in particular in thermodynamics, heat is defined as the contribution of transformed energy as a result of a chemical or nuclear reaction and transferred between two systems or between two parts of the same system. This energy is not attributable to a job or a conversion between two different types of energy. Heat is, therefore, a form of transferred energy and not a form of energy contained as internal energy.

As the energy is exchanged, the heat is measured in the International System in joules. In practice, however, it is often still used as the unit of measurement of calories,…

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## Thermodynamics

Thermodynamics is the branch of classical physics that studies and describes the thermodynamic transformations induced by heat and work in a thermodynamic system, as a result of processes that involve changes in the temperature and energy state variables.

Classical thermodynamics is based on the concept of macroscopic system, that is, a portion of physical mass or conceptually separated from the external environment, which is often assumed for convenience that is not disturbed by the exchange of energy with the system. The state of a macroscopic system that is in equilibrium conditions…

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## Entropy

What is entropy? Entropy (S) is a thermodynamic quantity originally defined as a criterion for predicting the evolution of thermodynamic systems.

Entropy is a function of extensive character state. The value of entropy, in an isolated system, grows in the course of a process that occurs naturally. Entropy describes how a thermodynamic system is irreversible.

The meaning of entropy is evolution or transformation. The word entropy comes from the Greek.

Entropy in the world of physics

In physics, entropy is the thermodynamic magnitude that allows us to calculate the…

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## Geothermal Heat Pump

The geothermal heat pump is an air conditioning system for buildings that exploits the heat exchange with the superficial subsoil, by means of a heat pump. Since the heat in the subsoil comes largely from the interior of the Earth, geothermal energy of low enthalpy is classified as a source of renewable energy, although the heat pump itself consumes electricity, generally produced from other sources of energy (for example, fossil fuels).

The heat pump allows the exchange of heat between a "source" at a lower temperature than the "well", or the point where the heat is introduced. In a…

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## Solar Collector

Solar collectors are the elements that capture solar radiation and convert it into thermal energy, into heat. It is a type of solar panel designed for use in solar thermal installations. It is also known as a solar collector.

The function of solar thermal energy is to take advantage of solar energy to obtain heat, to heat a fluid. Unlike photovoltaic solar energy whose function is to generate electricity.

Solar collectors are those with flat plates, evacuated tubes and absorber collectors without protection or isolation. The flat (or flat plate) collection…

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## Temperature

Definition of temperature: The temperature is the thermodynamic magnitude that shows the thermal energy of one body in relation to another.

Although the definition of temperature is simple and concise, you can explain what the temperature is in a more extensive way:

What is the temperature?

Temperature is a physical quantity of matter that quantifies the common notions of heat and cold. The objects of low temperature perceive them cold, while objects of higher temperatures we consider them warm or hot. This physiological sensation of cold and heat is generated…

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## Stirling Engine

The Stirling engine was invented in 1816 by Robert Stirling, a Scottish priest. The 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 helium, hydrogen, nitrogen or air. This gas is forced to cycle cyclically from a cold source where it contracts to a hot source where it expands. It is considered as a thermal engine (thermodynamic engine) due to the presence of a temperature gradient between the two thermal sources.

Originally, the Stirling engine was conceived as an…

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## Zero Law Of Thermodynamics

The zero law of thermodynamics speaks of what we experience every day: two systems that are in thermal equilibrium with a third are in equilibrium with each other. It is said that two bodies are in thermal equilibrium when, on contacting each other, their state variables do not change. Around this simple idea the zero law is established.

Every law of physics has its relevance, as well as the zero law of thermodynamics, which curiously was the last law to be introduced in literature. After the realization that heat is a form of energy that could be transformed into another, thermology…

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## Wind Power

What is wind power?

Wind energy is a renewable energy whose origin is wind. This energy source takes advantage of the kinetic energy generated by the effect of air currents to transform it into other useful forms for human activities. Historically, wind energy has been used since ancient times to move sail-driven boats or operate mill machinery when moving its blades.

The most common use of wind energy is the generation of electricity. Wind turbines are machines that convert the kinetic energy of wind into electrical energy.

Wind energy is an abundant, renewable,…

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## Forced Circulation For Solar Water Heater

A forced circulation for solar water heater is an installation in which the water circulates inside the circuit driven by a pump. With forced circulation system, the movement of water in the closed circuit is forced by a pump. This feature makes a big difference with respect to sanitary hot water installations with thermosyphon. In this way, it artificially moves the hot water not to the highest point of the closed circuit, but it does so from the solar collectors down to where the accumulator is located.

In many occasions it is not viable to install solar thermal equipment…

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## Domestic Hot Water (DHW)

One of the applications of solar thermal energy is the obtaining of sanitary hot water (DHW). Solar collectors capture the energy of solar radiation to increase the temperature of a fluid.

Domestic hot water (DHW) is water intended for human consumption (potable) that has been heated. It is used for sanitary uses (bathrooms, showers, etc.) and for other cleaning uses (washing dishes, washing machine, dishwasher, floor scrubbing). In terms of energy, the DHW is an important component to take into account, since it represents between 25 and 40% of the energy consumption of homes.

As…

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