The coefficient of thermal conductivity of water at different temperatures. Big encyclopedia of oil and gas

Water has a high heat capacity. The high heat capacity of water plays a significant role in the process of cooling and heating of water bodies, as well as in shaping the climatic conditions of the adjacent regions. Water slowly cools and heats up both during the day and during the change of seasons. The maximum temperature fluctuation in the World Ocean does not exceed 40°C, while in the air these fluctuations can reach 100-120°C. The thermal conductivity (or transfer of thermal energy) of water is negligible. Therefore, water, snow and ice do not conduct heat well. In water bodies, heat transfer to depths is very slow.

Viscosity of water. Surface tension

As salinity increases, the viscosity of water increases slightly. Viscosity or internal friction is the property of fluid (liquid or gaseous) substances to resist their own flow. The viscosity of liquids depends on temperature and pressure. It decreases both with increasing temperature and with increasing pressure. The surface tension of water determines the strength of adhesion between molecules, as well as the shape of the surface of the liquid. Of all liquids except mercury, water has the highest surface tension. As the temperature rises, it decreases.

Laminar and turbulent, steady and unsteady, uniform and non-uniform movement of water

Laminar motion is a parallel jet flow, with a constant flow of water, the speed of each point of the flow does not change in time, neither in magnitude nor in direction. Turbulent - a form of flow in which the elements of the flow make disorderly movements along complex trajectories. With uniform motion, the surface is parallel to the leveled bottom surface. with uneven movement, the slope of the flow velocity of the living section is constant in the length of the section, but varies along the length of the flow. Unsteady motion is characterized by the fact that all hydraulic elements of the flow in the considered section change in length and in time. Established - on the contrary.

The water cycle, its continental and oceanic links, the intracontinental cycle

Three links are distinguished in the cycle - oceanic, atmospheric and continental. Continental includes lithogenic, soil, river, lake, glacial, biological and economic links. The atmospheric link is characterized by the transfer of moisture in the air circulation and the formation of precipitation. The oceanic link is characterized by the evaporation of water, during which the content of water vapor in the atmosphere is continuously restored. Intracontinental circulation is typical for areas of internal runoff.

Water balance of the world's oceans, the globe, land

The Earth's global moisture cycle finds its expression in the Earth's water balance, which is mathematically expressed by the water balance equation (for the Earth as a whole and for its individual parts). All components (components) of the water balance can be divided into 2 parts: incoming and outgoing. Balance is a quantitative characteristic of the water cycle. The method of calculating the water balance is used to study the incoming and outgoing elements of large parts of the globe - land, the Ocean and the Earth as a whole, individual continents, large and small river basins and lakes, and finally, large areas of fields and forests. This method allows hydrologists to solve many theoretical and practical problems. The study of the water balance is based on a comparison of its incoming and outgoing parts. For example, for land, precipitation is the incoming part of the balance, and evaporation is the outgoing part. The replenishment of the Ocean with water occurs due to the runoff of river waters from land, and the flow is due to evaporation.

Related information:

1. How can you buy the sky or the warmth of the earth? This idea is incomprehensible to us. If we don't own fresh air and splashes of water, how can you buy them from us?

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The thermal conductivity of water is about 5 times higher than that of oil. It increases with increasing pressure, but at pressures that occur in hydrodynamic transmissions, it can be taken constant.

The thermal conductivity of water is approximately 28 times higher than that of air. In accordance with this, the rate of heat loss increases when the body is immersed in water or in contact with it, and this largely determines the heat sensation of a person in air and in water. So, for example, at - (- 33, the air seems warm to us, and the same water temperature seems indifferent. The air temperature 23 seems to us indifferent, and the water of the same temperature seems cool. At - (- 12, the air seems cool, and the water seems cold .

The thermal conductivity of water and water vapor is undoubtedly the best studied of all other substances.

The thermal conductivity of water has a positive temperature course, therefore, at low concentrations, the thermal conductivity of aqueous solutions of many salts, acids and alkalis increases with increasing temperature.

The thermal conductivity of water is much greater than that of other liquids (except metals) and also changes anomalously: it increases up to 150 C and only then begins to decrease. The electrical conductivity of water is very small, but increases markedly with an increase in both temperature and pressure. The critical temperature of water is 374 C, the critical pressure is 218 atm.

The thermal conductivity of water is much greater than that of other liquids (except metals), and it also changes anomalously: it increases up to 150 C and only then begins to decrease. The electrical conductivity of water is very small, but increases markedly with an increase in both temperature and pressure. The critical temperature of water is 374 C, the critical pressure is 218 atm.

The thermal conductivity of water has a positive temperature course, therefore, at low concentrations, the thermal conductivity of aqueous solutions of many salts, acids and alkalis increases with increasing temperature.

The thermal conductivity of water, aqueous solutions of salts, alcohol-water solutions and some other liquids (for example, glycols) increases with increasing temperature.

The thermal conductivity of water is very small compared to the thermal conductivity of other substances; so, the thermal conductivity of the cork is 0 1; asbestos - 0 3 - 0 6; concrete - 2 - 3; tree - 0 3 - 1 0; brick-1 5 - 2 0; ice - 5 5 cal / cm sec deg.

The thermal conductivity of water X at 24 is 0 511, its heat capacity with 1 kcal kg C.

The thermal conductivity of water prn 25 is 1 43 - 10 - 3 cal / cm-sec.

Since the thermal conductivity of water (R 0 5 kcal / m - h - deg) is approximately 25 times greater than that of still air, the displacement of air by water increases the thermal conductivity of the porous material. With rapid freezing and the formation in the pores of building materials, it is no longer ice, but snow (R 0 3 - 0 4), as our observations have shown, the thermal conductivity of the material, on the contrary, decreases somewhat. Correct accounting for the moisture content of materials is of great importance for thermal engineering calculations of structures, both aboveground and underground, for example, water and sewage.

Theories of transport phenomena, based on the statistical method of Gibbs, set themselves the task of obtaining kinetic equations from which one can find a specific form of nonequilibrium distribution functions. It is assumed that the nonequilibrium distribution function of the system has a quasi-equilibrium form, and the temperature, particle number density, and their average velocity depend on

space-time coordinates. The correlation of successive collisions is achieved by taking into account not only hard collisions (due to repulsion), but also so-called soft collisions (due to attraction), as a result of which the particles move along curved trajectories.

The most famous is the Kirkwood method, in which soft impacts determine the coefficient of friction. According to Einstein-Smoluchowski the coefficient of friction

where is the Boltzmann constant, T is the absolute temperature and the self-diffusion coefficient.

According to Kirkwood, the correlation of the interaction of the surrounding particles with a given particle is carried out over the characteristic time, after which the forces acting on the given particle from other particles are considered as uncorrelated. Moreover, the interaction correlation time should be less than the characteristic relaxation time of the macroscopic characteristics of the substance.

For the thermal conductivity coefficient, Kirkwood obtains the following expression

where is the number of particles per unit volume, is the radial equilibrium distribution function of particles, is the potential of pair forces.

In addition to the fact that in order to calculate N using this formula, it is necessary to know with great accuracy not only but also its derivatives, as well as (which in itself is a practically unsolvable problem at the moment) It has recently been shown that the kinetic coefficients cannot be directly expanded into a series in terms of degrees of density, as Kirkwood kisses, but a more complex expansion must be used. This is due to the need to take into account the repeated collisions of particles already correlated in

the result of previous collisions with other particles. In connection with the above difficulties, it is necessary to resort to model research methods.

Among modeling works, of interest are works based on the concept of the nature of thermal motion in liquids, in which heat transfer is determined by means of hyperacoustic oscillations of the medium (phonons). This approach takes into account the collective nature of the motion of molecules in a liquid. In this case, the thermal conductivity K is determined, for example, as follows (Sakiadis and Cotes formula)

where is the speed of hypersound; heat capacity at constant pressure, average distance between molecules, density.

In addition to the model approach, there are also semi-empirical relations for thermal conductivity (Filippov,

Thermal conductivity is approximately 5 times less than thermal conductivity (Table 43). Carbon tetrachloride is an ordinary liquid, for which, like for all other liquids, there is a decrease in the speed of sound with increasing temperature, a decrease in thermal conductivity and an increase in heat capacity. In water at low temperatures, the opposite is true. The nature of the change of all these properties in water resembles the nature of their change for ordinary substances in the gaseous state. Indeed, the thermal conductivity of a gas increases with increasing temperature.

Mean velocity of molecules, heat capacity and mean free path).

For example, below is the dependence of the thermal conductivity of air at atmospheric pressure for a number of temperatures.

The change in thermal conductivity during the melting of ice I and the further change in T with an increase in the temperature of liquid water are shown in fig. 57, which shows that the thermal conductivity during the melting of ice I decreases by approximately

Table 43 (see scan) Temperature dependences of thermal conductivity of water and carbon tetrachloride

4 times. A study of the change in the thermal conductivity of supercooled water down to -40°C shows that supercooled water does not have any features at 0°C (Table 43). To illustrate the normal temperature course of thermal conductivity, the dependence of thermal conductivity on temperature is presented. The thermal conductivity decreases monotonically with increasing temperature.

All normal liquids change the sign of the change in thermal conductivity with temperature with increasing pressure. For a large class of liquids, this change occurs at pressure. The thermal conductivity of water does not change the nature of the temperature dependence under pressure. The relative value of the increase in the thermal conductivity of water at pressure is -50%, while for

other normal liquids this increase at the same pressure is (Fig. 58).

The pressure dependence of K for water is shown in fig. 58. Such a small relative increase in the thermal conductivity of water with increasing pressure is due to the low compressibility of water compared to other liquids, which is determined by the nature of the forces of intermolecular interaction.

Rice. 57. The dependence of the thermal conductivity of water and temperature

Rice. 58. Temperature dependence of thermal conductivity and silicone oil for a number of pressures

In the section on the question what is the coefficient of thermal conductivity (for example, water) ?? (what is equal to water?) given by the author Caucasian the best answer is Thermal conductivity coefficient - a numerical characteristic of the thermal conductivity of a material, equal to the amount of heat (in kilocalories) passing through a material 1 m thick and 1 sq. m per hour with a temperature difference on two opposite surfaces of 1 deg. C. Metals have the highest thermal conductivity, while gases have the lowest.
As for the water...
"The thermal conductivity of most liquids decreases with increasing temperature. Water is an exception in this regard. With an increase in temperature from 0 to 127 ° C, the thermal conductivity of water increases, and with a further increase in temperature, it decreases (Fig. 3.2). At 0 ° C, the thermal conductivity water is 0.569 W / (m ° C). With an increase in the mineralization of water, its thermal conductivity decreases, but very slightly "... See.
Source: Dictionary of Natural Sciences. Glossary. RU

Answer from Alexander Tyukin[guru]
What Fess XX said is not the thermal conductivity, but the volumetric heat capacity.
The thermal conductivity coefficient of a substance is a value that shows how much heat is required to be applied to one end of an infinitely thin wire of this substance so that a point of this wire at a distance of 1 m from this end increases by 1 degree in one second (assuming zero heat transfer to space). Mike wrote everything well.

Answer from Mike[guru]
Thermal conductivity is the ability of a substance to transfer thermal energy, as well as a quantitative assessment of this ability (also called the thermal conductivity coefficient).
The phenomenon of thermal conductivity lies in the fact that the kinetic energy of atoms and molecules, which determines the temperature of a body, is transferred to another body during their interaction or is transferred from more heated areas of the body to less heated areas
Substance Thermal conductivity
W/(m*deg)
Aluminum 209.3
Iron 74.4
Gold 312.8
Brass 85.5
Copper 389.6
Mercury 29.1
Silver 418.7
Steel 45.4
Cast iron 62.8
water, 2.1

The thermal conductivity of water is a property that we all, without suspecting it, very often use in everyday life.

Briefly about this property, we already wrote in our article. CHEMICAL AND PHYSICAL PROPERTIES OF WATER IN THE LIQUID STATE →, in this material we will give a more detailed definition.

First, consider the meaning of the term thermal conductivity in general.

Thermal conductivity is...

Technical Translator's Handbook

Thermal conductivity - heat transfer, in which the transfer of heat in an unevenly heated medium has an atomic-molecular character

[Terminological dictionary for construction in 12 languages ​​(VNIIIS Gosstroy of the USSR)]

Thermal conductivity - the ability of a material to transmit heat flow

[ST SEV 5063-85]

Technical Translator's Handbook

Explanatory Dictionary of Ushakov

Thermal conductivity, thermal conductivity, pl. no, female (physical) - the property of bodies to distribute heat from more heated parts to less heated ones.

Explanatory Dictionary of Ushakov. D.N. Ushakov. 1935-1940

Big Encyclopedic Dictionary

Thermal conductivity is the transfer of energy from more heated parts of the body to less heated ones as a result of thermal motion and the interaction of its constituent particles. It leads to equalization of body temperature. Usually, the amount of energy transferred, defined as the heat flux density, is proportional to the temperature gradient (Fourier's law). The coefficient of proportionality is called the coefficient of thermal conductivity.

Big Encyclopedic Dictionary. 2000

Thermal conductivity of water

For a more voluminous understanding of the overall picture, we note a few facts:

• The thermal conductivity of air is approximately 28 times less than the thermal conductivity of water;
• The thermal conductivity of oil is approximately 5 times less than that of water;
• As the pressure increases, the thermal conductivity increases;
• In most cases, with an increase in temperature, the thermal conductivity of weakly concentrated solutions of salts, alkalis and acids also increases.

As an example, we present the dynamics of changes in the values ​​of thermal conductivity of water depending on temperature, at a pressure of 1 bar:

0°С - 0.569 W/(m deg);
10°С - 0.588 W/(m deg);
20°С - 0.603 W/(m deg);
30°C - 0.617 W/(m deg);
40°C - 0.630 W/(m deg);
50°С - 0.643 W/(m deg);
60°С - 0.653 W/(m deg);
70°С - 0.662 W/(m deg);
80°С - 0.669 W/(m deg);
90°С - 0.675 W/(m deg);

100°С – 0.0245 W/(m deg);
110°С – 0.0252 W/(m deg);
120°С - 0.026 W/(m deg);
130°С - 0.0269 W/(m deg);
140°С - 0.0277 W/(m deg);
150°С - 0.0286 W/(m deg);
160°С - 0.0295 W/(m deg);
170°С - 0.0304 W/(m deg);
180°С - 0.0313 W/(m deg).

Thermal conductivity, however, like all the others, is a very important property of water for all of us. For example, we very often, without knowing it, use it in everyday life - we use water to quickly cool heated objects, and a heating pad to accumulate heat and store it.