Ancient history of heating
Even at the early stages of evolution, it was easier for a person to live in regions with
One of the factors that allowed humanity to becomethe prevailing view on Earth has become the understanding that bodies, liquids and gas around us can be heated, and heat allows us to make life more comfortable, fulfilling and easier. Of course, primitive man did not immediately master the technique of using fire (all the more not from the point of view of burning, but precisely heating). The first evidence of human use of fire for cooking and heating was found in East Africa: in Chesowanyi near Lake Baringo, Koobi Fora and Ologesalirie in Kenya.
So, the evidence in Chesovagni presentsare fragments of red clay, whose age is 1.42 million years. Judging by their hardness, they were heated to 400 ° C. In Kenya, evidence has been found for the use of Homo erectus fire, approximately 1.5 million years old, with red deposits that can only form at temperatures of 200-400 ° C.
What is heating?
Heating is natural or artificialthe physical process of temperature rise. This can be due to internal energy or the supply of energy from the outside. For the latter, a heating element is used. Designs can be very different: from a fire to a nuclear reactor.
In addition to differences in energy sources, the process itselfheating can occur both externally and internally. The latter examples include: the heat generated in the Earth's core due to the energy carried by magma flows; solutions during electrolysis, or, by the way, modern tobacco heating systems. With heating outside, everything is simple - it is a classic fire, heating, microwave.
Heating occurs by increasing the speedmovement or vibration of molecules and atoms that make up the body. In different bodies, this process takes place in different ways. If we are talking about gases, then their molecules chaotically move at high speeds (it can be hundreds of meters per second) throughout the entire volume filled with gas. During their movement, the molecules collide and bounce from each other, changing the speed and direction of movement. In the case of liquids, the molecules in them vibrate about equilibrium positions, since they are located very close to each other, and relatively rarely can jump from one position to another. In solids, particles vibrate about an equilibrium position. Heating in all these cases leads to the fact that the speed of the particles increases. Therefore, the chaotic motion of particles is usually called thermal in physics. And the heating of the body itself depends on its heat capacity and thermal conductivity.
Heat capacity - the amount of heat absorbed or released by the body during heating (cooling) by 1 K (Kelvin).
Thermal conductivity - the ability of bodies to conduct heat from moreheated parts of the body to less heated parts by the chaotic movement of particles (atoms, molecules, electrons). Such heat exchange can occur in any bodies with a non-uniform temperature distribution, but the mechanism of heat transfer will depend on the state of aggregation of matter.
Heating is used today in a wide variety ofareas of human life: from domestic use in cooking and heating to scientific experimentation and transportation. And nature itself uses this process: ice melts, the climate changes, the water temperature in the World Ocean rises, flora and fauna change, chemicals and rocks are formed.
Boiling is the most common heating methodwater used exclusively by humans. It's not just about cooking food, which requires boiling water. Boiling also allows you to destroy most of the parasites that live in the water, to decontaminate products, and also to clean things, objects from fatty contamination.
The boiling process consists of three stages:on the first, air bubbles appear in the water, which slip from the bottom of the container, on the second - the bubbles begin to rise rapidly to the surface, turbidity occurs, resembling water running from a spring. In the third stage, water begins to boil, large bubbles reach the surface, and water may spray.
The boiling process is accompanied by the release of steam.In addition, during boiling, colloidal particles of dirt settle, and the water softens, since salts precipitate, and the concentration of volatile components and free chlorine decreases.
But with prolonged boiling, it increasesconcentration of non-volatile substances. Heating water to boiling water cannot destroy heavy metals, pesticides, herbicides, nitrates, phenols, and oil products. There are microbes that can survive in boiling water for quite a long time - minutes or even hours. Prions are not deactivated even when boiled for 18 minutes at 134 ° C in a sealed steam autoclave.
Heat treatment of food
Heat treatment is used in the cooking of variouspeoples and cultures for a large number of products. Typically, such processing has three purposes: softening, improving the taste or appearance, and decontamination, especially when it comes to meat products.
In addition to cooking, which can take place not only withboiling process, but also for steam, as well as at low temperatures, this type of processing includes cooking in a vacuum - sous-vide, when products are cooked in a vacuum package. In addition, there is a method of cooking in an autoclave, where cooking takes place under overpressure at a temperature of 110–130 ° C.
Another type of heat treatment is frying,the second most common cooking method. The product adheres to dishes whose surface is smeared with a thin layer of hot fat. If we are talking about flour products and a special category of dishes, then baking in a hob or oven is used. And meat and fish products are often smoked using hot and cold smoke.
To maintain the temperature before dispensing or duringduring transportation, a special type of treatment is used - temperature control. And for an effective serving, short-term ignition of the finished dish is used, this is called flaming.
Residents know about this method of heating the airmany countries - it is almost impossible to survive the long winter season without heating. On the territory of Russia, the average air temperature during this period is -19.7 ° C. Water heating is the most popular and cheapest method, but today there are other options that allow you to heat the home of a modern person. Moreover, their task includes not only heating the room to compensate for heat loss, but also maintaining the temperature.
Depending on the predominant methodHeat transfer space heating can be convective and radiant. Convective heating means a type of heating in which heat is distributed by mixing volumes of hot and cold air. The disadvantages of convective heating include a large temperature difference in the room (high air temperature at the top and low at the bottom) and the impossibility of ventilating the room without loss of thermal energy. The radiant method implies the presence of special devices that are installed under the floor or above the heated area, or mounted directly into the walls.
According to the heat source, heating can be very diverse: from stove and steam to liquid fuel and infrared.
Heating systems have been around for many hundreds of years.The first means of heating is a fire. And the heating device is hypocaust, the ancient "warm floor" used by the Romans. The surface of the stone floor was heated with the help of gas that came out of the furnaces and accumulated in the cavities under the floor.
Core of the earth
The world's largest "heater" is located inthe very heart of our planet is in the core of the Earth. The central and deepest part of the planet is located under the mantle and, presumably, consists of an iron-nickel alloy with an admixture of other siderophilic elements. The depth is 2,900 km. The core is divided into a solid inner core with a radius of about 1,300 km and a liquid outer core about 2,200 km thick. The temperature on the surface of the Earth's solid core reaches 6,230 ± 500 K (5,960 ± 500 ° C).
From the earth's core, colossalascending heat fluxes of magma - plumes. At the surface of the mantle, they spread to the sides, causing continental drift, and when cooled down, they sink into the depths. But the core has its own sources of heating: the decay of long-lived radioactive elements and the friction between the core and the outer layers of the Earth, the rotation of which is gradually slowed down by the tides. Nevertheless, the core cools down and gradually crystallizes from this: the diameter of the inner solid core increases by several centimeters per century.
Heating in chemistry
Temperature increase is used in chemicalindustries to accelerate mass transfer and chemical processes, the temperature conditions of which depend on the coolant and the heating method: water vapor, hot liquids, point gases, electric current and radiation.
The most common method in organicsynthesis is boiling and heating. According to Van't Hoff's rule, when heated to 10 ° C, the rate of chemical reactions increases by 2–4 times. Chemical reactions in organic chemistry (as opposed to inorganic) are rather slow. Therefore, heating significantly speeds up the work of chemists.
But organic compounds are rather unstable and under strong influence they will tar. Therefore, in some cases, the reactions are carried out not with heating, but with cooling.
Water baths are used only in cases wherewhen heating is required to a temperature not exceeding 100 ° С. Sand baths are used for gentle exposure to high temperatures or for gentle ignition. The temperature of the sand bath is 200–300 ° С. Heating to high temperatures is carried out in muffle furnaces. Calcination is carried out in crucibles, which are usually covered with lids.
Electric heating is also used inthe chemical industry, first of all, to save money. Direct heating of water and aqueous solutions with an alternating electric current at an electric voltage lower than the decomposition voltage of liquids shows that at low specific powers the generated thermal energy exceeds the consumed electrical energy introduced into the heated liquid.
Induction heating is heating materialselectric currents that are induced by an alternating magnetic field. Such heating of products made of conductive materials - conductors - occurs using the magnetic field of inductors. The inductor-workpiece system is a coreless transformer in which the inductor is the primary winding. The workpiece is a short-circuited secondary winding. And the magnetic flux between the windings is closed in the air.
At high frequency, eddy currents are displacedthe magnetic field formed by them into the thin surface layers of the workpiece (skin effect), as a result of which their density increases sharply, and the workpiece heats up. The inductor itself gets very hot during operation, as it absorbs its own radiation. In addition, it absorbs heat radiation from a hot workpiece. Inductors are made from copper tubes cooled by water. Water is supplied by suction - this ensures safety in case of burn-through or other depressurization of the inductor.
This method is used in a wide variety of industrial areas: from ultrapure non-contact smelting to jewelry and disinfection of medical instruments.
Dielectric heating (microwave)
For heating dielectric materialsan alternating electric field or electromagnetic wave is used - we are talking about popular microwave ovens, or microwave ovens. HFC heating (with high frequency currents) is created in capacitors, and microwave (microwave radiation) - in waveguides and resonant cavities. With this method, the heating of bodies is caused by losses due to the dipole polarization of dielectrics.
The disadvantage of this method is its heterogeneity. With the microwave method, only surface heating occurs, which depends on the thermal conductivity of the material.
When using electromagnetic microwave wavesheating is caused by molecular dipole rotation in a dielectric - a typical dipole molecule is a water molecule. The method is most commonly used for defrosting and heating food. Since water in food contains a large amount of salts that dissociate into ions, which serve as carriers of electric charges and also react to an alternating electromagnetic field, the heating of food is caused by both the reorientation of polar dipole molecules and the displacement of ions.
Heating the tobacco, not burning it, has becomea fundamental difference between alternative smokeless products being developed at the Philip Morris International (PMI) R&D center. The company relied on disruptive technologies, science and innovation. The Center employs more than 430 scientists and engineers of various specialties, who have been applying all their experience and knowledge for more than 10 years to create a future without cigarette smoke. The company conducts a phased and comprehensive scientific assessment of its innovative smokeless products, based on the practices applied in the pharmaceutical industry, following international quality standards, the principles of good laboratory practice (GLP) and good clinical practice (GCP). IQOS has passed all stages of rigorous scientific evaluation, including 18 preclinical and 10 clinical studies, during which it was confirmed that when using IQOS, 95% less harmful substances are emitted compared to cigarettes. *
Important: this does not mean a 95% risk reduction. Using IQOS does not eliminate health risks.
* “95% less hazardous substances” refers to the average reduction in hazardous substances (excluding nicotine) in the IQOS aerosol compared to the smoke of the reference cigarette used in the study (3R4F).
IQOS uses HeatControl ™ technology,which is designed as follows: a ceramic blade-shaped element heats the tobacco from the inside to a temperature not exceeding 350 ° C. Such a temperature regime excludes combustion, which means that smoke and ash are not formed, there is no risk of burning clothes, upholstery in the car, furniture or burning someone.
The uniqueness of the technology lies in the fact thatheating occurs from the inside, not outside, and the element comes into direct contact with the tobacco, not igniting it, but heating it gently. In addition, thanks to innovative technologies, the heating temperature during the operation of the IQOS device is automatically controlled and maintained at the required level. Traces of gold and platinum, applied to the heating element, together form a thermocouple that measures and transmits temperature data to a control unit located in the device holder.
All IQOS models without disconnection - fromclassic 2.4 Plus to the newest and most elegant IQOS 3 DUOS - uses a patented technology developed in Switzerland. When creating IQOS, scientists and technology experts managed to eliminate the combustion process, replacing it with heating, so IQOS has a number of advantages compared to continuing to smoke cigarettes. Today, over 11 million adult users worldwide have chosen IQOS *.
* Data based on internal financialPMI reporting, IQOS adult surveys and market analysis as of [October 2020]. We took into account adult IQOS users who completely stopped smoking cigarettes, and for whom the consumption of PMI tobacco sticks was at least 70% of all heated tobacco during the last 7 days at the time of the survey.
If we combine thermophysical andelectrochemical processes on the surface of the anode associated with local boiling of the liquid, then a phenomenon called electrolyte-plasma treatment will result. Another name is anodic electrolyte heating.
For the first time the phenomenon of glow and heating of electrodesnoticed at once by several scientists in the XIX century - Arthur Venelt, Alexander Walter and Georg Simon Ohm. They proved that as a result of the thermal effect of a current on an electrode with a relatively small surface around it, a local boiling-up of the solution occurs with the formation of a vapor layer and the opening of the electrical circuit. The inductance in the circuit contributes to the appearance of the emf. and breakdown of the vapor-gas layer with light phenomena.
This heating method is widely used today.for high-speed hardening of parts surfaces - for example, carburizing, nitriding, boriding, nitrocarburizing and / or quenching in a working electrolyte. And the electrolytic-plasma treatment of steel increases its surface hardness, wear resistance, and corrosion resistance.
Laser material processing is usedeverywhere, including for the production of nanotubes from graphene. Depending on the intensity and duration of exposure to laser radiation, it is possible to heat the material without visible destruction, melt it, evaporate and even wash out the products of destruction.
Calculations show that the heating rate atlaser irradiation of materials is very high - up to 10–10 ° C / s. In a short time, the surface layers have time to heat up to high temperatures, melt and overheat. In the superheated metal, impurities have time to dissolve.
Laser heating is the same as gas-discharge heating,used to concentrate energy on the surface of graphite. This energy is used to thermally spray graphite. In laser sputtering, practically only multilayer nanotubes are obtained - with the number of layers from 4 to 24 and lengths up to 300 nm. In this case, the graphite sample - the target on which the laser radiation is focused - is placed in an oven for additional heating.
And a group of theoretical physicists from one of the Londoncolleges have even come up with a new method that could allow lasers to heat certain materials to temperatures of the solar core and above, albeit in as little as 20 quadrillion seconds.
Man in his technological achievementsalways inspired by nature: from the use of fire for cooking and ending with modern nuclear reactors, which are based on the same processes as in generating heat from the core of the Earth. The ability to heat has allowed humanity to become the dominant species on the planet, expand its habitat even to the most severe climatic zones, accelerate chemical reactions, create super-durable materials and, finally, make life more comfortable and technologically advanced.
Doesn't exclude risks.
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