High thermal conductivity and water heat capacity is explained. Great Oil and Gas Encyclopedia

Who knows the formula of the water since the time of school pore? Of course, everything. It is likely that from the entire course of chemistry, many who later do not study it specialized, only and remains knowledge of what denotes the formula H 2 O. But now we will now and deeply try to figure out what kind of main properties and why it is without her life without it On the planet, the earth is impossible.

Water as a substance

Water molecule, as we know, consists of one oxygen atom and two hydrogen atoms. Its formula is written as follows: H 2 O. This substance may have three states: solid - as ice, gaseous - in the form of steam, and liquid - as a substance without color, taste and odor. By the way, this is the only substance on the planet that can exist in all three states at the same time in natural conditions. For example: on the poles of the Earth - ice, in the oceans - water, and evaporation under sunlight is steam. In this sense, water anomalous.

More water is the most common substance on our planet. It covers the surface of the planet Earth almost seventy percent is both oceans, and numerous rivers with lakes, and glaciers. Most of the water on the planet salty. It is not suitable for drinking and agriculture. Freshwater is only two and a half percent of the total water on the planet.

Water is a very strong and high-quality solvent. Due to this, chemical reactions in water are held at a huge speed. This property affects the metabolism in the human body. The well-known fact that the body of an adult is seventy percent consists of water. The child has this percentage even higher. To the old age, this indicator falls from seventy to sixty percent. By the way, this feature of water clearly demonstrates that she is she who is the basis of a person's life. Than water in the body is more - it is healthier, more active and younger. Therefore, scientists and doctors of all countries tirelessly say that you need to drink a lot. It is water in its pure form, not substitutes in the form of tea, coffee or other drinks.

Water forms climate on the planet, and this is not an exaggeration. Warm flows in the ocean heated entire continents. This happens due to the fact that water absorbs a lot of solar heat, and then gives it when he starts to cool. So it regulates the temperature on the planet. Many scientists say that the earth would have cooled and became a stone if it were not for the presence of such a quantity of water on the green planet.

Properties of water

The water has many very interesting properties.

For example, water is the most rolling matter after air. From the school course, many probably remember such a concept as a cycle of water in nature. For example: the rods evaporate under the influence of direct sunlight, turns into water vapor. Further, this pairs through wind is transferred somewhere, going to the clouds, and even in and falls in the mountains in the form of snow, hail or rain. Further, from the mountains of the rods again runs down, partially evaporated. And so - in a circle - the cycle is repeated millions of times.

Also the water has a very high heat capacity. It is because of this reservoir, especially oceans, very slowly cool when moving from a warm season or time of day to cold. Conversely, with an increase in air temperature, water is very slowly heated. Due to this, as mentioned above, water stabilizes the air temperature throughout our planet.

After mercury, water has the highest value of surface tension. It is impossible not to note that the drop is accidentally spilled on a flat surface sometimes becomes an impressive speck. This manifests the drig of water. Another property manifests itself with it with a decrease in temperature to four degrees. As soon as the water cools up to this mark, it becomes easier. Therefore, the ice always floats on the surface of the water and freezes the crust, covering rivers and lakes. Due to this in the water bodies freezing in winter, the fish does not freeze.

Water like electricity conductor

Initially, it is worth learn what electrical conductivity is (water including). Electrical conductivity is the ability of any substance through itself an electric current. Accordingly, the electrical conductivity of water is the possibility of water to carry out the current. This ability directly depends on the amount of salts and other impurities in the liquid. For example, the conductor of distilled water is almost minimized due to the fact that such water is cleaned from various additives that are so needed for good electrical conductivity. An excellent current conductor is a sea of \u200b\u200bwater, where the salts concentration is very large. Another electrical conductivity depends on the temperature of the water. The temperature value above is the large electrical conductivity of the water. This pattern is detected thanks to the multiple experiments of physician scientists.

Measuring water conductivity water

There is such a term - conductor. This is called one of the methods of electrochemical analysis based on electrical conductivity of solutions. This method is used to determine the concentration in solutions of salts or acids, as well as to control the composition of some industrial solutions. Water has amphoteric properties. That is, depending on the conditions, it is able to exercise both acidic and basic properties - to act as an acid, and as a basis.

The device that is used for this analysis has a very similar name - conductor. With the help of the conductor, the electrical conductivity of electrolytes in the solution is measured, the analysis of which is conducted. Perhaps it is worth explaining another term - electrolyte. This substance that when dissolved or melting disintegrates ions, due to which an electric current is subsequently carried out. Ion is an electrically charged particle. Actually, the conductor, taking the basis of certain units of water conductivity, determines its electrical conductivity. That is, it determines the electrical conductivity of a particular amount of water taken for the initial unit.

Even before the start of the seventies of the last century, a unit of measurement "MO" was used to designate the conductivity of electricity, it was derived from another value - Oma, which is the main unit of resistance. Electrical conductivity is a value inversely proportional to the resistance. Now it is measured in Siemens. This value received its name in honor of the physics scientist from Germany - Verner von Siemens.

Siemens

Siemens (may be referred to as cm and S) - this is a value inverse by yum, which is a unit of measuring electrical conductivity. One cm is equal to any conductor, the resistance of which is 1 ohms. Siemens expressed through the formula:

• 1 cm \u003d 1: Ohm \u003d A: B \u003d kg -1 · m -2 · c³², where
  A - Ampere,
  V - Volt.

Thermal conductivity of water

Now let's talk about whether it is the ability of any substance to carry thermal energy. The essence of the phenomenon is that the kinetic energy of atoms and molecules, which determine the temperature of this body or substance is transmitted to another body or substance when they interact. In other words, thermal conductivity is a heat exchange between the bodies, substances, as well as between the body and the substance.

The thermal conductivity of the water is also very high. People use this property of water every day, without noticing. For example, pouring cold water in container and getting winding drinks or products. Cold water takes heat from a bottle, container, in return to the cold, and reverse reaction is possible.

Now this phenomenon can easily be in the scale of the planet. The ocean is heated during the summer, and then - with the onset of cold weather, slowly cools and gives his heat air, thereby heating the continent. Having cooled over the winter, the ocean begins to warm very slowly compared to the Earth and gives its coolness to the continents weak from the summer sun.

Density of water

Above it described that the fish lives in winter in a reservoir due to the fact that the water freezes the crust over their entire surface. We know that in ice water begins to turn into a temperature in zero degrees. Due to the fact that the density of water is greater than the density pops up and freezes on the surface.

Properties of water

Also, water is also capable of being the oxidizing agent, and the reducing agent. That is, water, giving up its electrons, charges positively and oxidized. Or becomes electrons and charges negatively, it means that it is restored. In the first case, water is oxidized and called the dead. It has very powerful bactericidal properties, but not necessary to drink it. In the second case, water is alive. It is cheery, stimulates the body to restore, carries the energy to the cells. The difference between these two properties of water is expressed in the term "redox potential".

What water is capable of reacting

Water is able to react with almost all substances that exist on Earth. The only thing for the occurrence of these reactions should be provided with a suitable temperature and microclimate.

For example, at room temperature, water reacts perfectly with such metals as sodium, potassium, barium - they are called active. With halogens, this is fluorine, chlorine. When heated, water reacts perfectly with iron, magnesium, coal, methane.

Using various catalysts, water reacts with amides, carboxylic acid esters. The catalyst is a substance, as if pushing components to a mutual reaction, accelerating it.

Are there any water anywhere else except the Earth?

So far, on the same planet of the solar system, except for the Earth, water is not found. Yes, they suggest her presence on satellites of such planets-giants, like Jupiter, Saturn, Neptune and Uranus, but so far there are no accurate data from scientists. There is another hypothesis until tested finally about the groundwater on the Mars planet and on the Earth's satellite - the moon. Regarding Mars, a number of theories are generally nominated for the fact that once on this planet was the ocean, and his possible model was even designed by scientists.

Outside the solar system, there are many large and small planets, where, by guessing scientists, there may be water. But not yet the slightest opportunity to make sure of this.

How to use heat and electrical conductivity of water for practical purposes

Due to the fact that water has a high meaning of heat capacity, it is used in heating centers as a coolant. It provides heat transfer from the manufacturer to the consumer. As an excellent coolant water uses many nuclear power plants.

In medicine, ice is used for cooling, and pairs for disinfection. The ice is used in the system of catering.

In many nuclear reactors, water is used as a moderator, for the successful flow of the chain nuclear reaction.

Pressure water is used for splitting, prolaming and even for cutting rocks. It is actively used in the construction of tunnels, underground rooms, warehouses, metro.

Conclusion

It follows from the article that water in its properties and functions is the most indispensable and striking substance on Earth. Does the life of a person or any other living creature on the ground dependent on the ground? Of course, yes. Does this affect the substance of scientific activities by a person? Yes. Does water with electrical conductivity, thermal conductivity and other useful properties? The answer is also "yes." The other thing is that water on earth, and even more waters clean, less and less. And our task is to save and secure it (and therefore all of us) from the disappearance.

Contents section

The thermal conductivity is due to local temperature by the movements of microstructural elements. In liquids and gases, microstructural movements are random molecular movements, the intensity of which increases with increasing temperature. In solid metal at average temperatures, heat transmission occurs due to the movement of free electrons. In non-metallic solids, thermal conductivity is carried out by elastic acoustic waves resulting from displacements of all molecules and all atoms from their equilibrium positions. The leveling of temperature due to thermal conductivity is understood as the transition to the disorderly distribution of the waves superimposed on each other, in which the distribution of the oscillation energy is uniform in the whole body. In practical conditions, thermal conductivity is in its purest form in solids.

The thermal conductivity theory is based on the Fourier law, binding heat transfer inside the body with a temperature state in close proximity to the place under consideration - is expressed as follows:

dQ / Dτ \u003d - λF * dt / dl,

where: DQ / Dτ is the heat transition rate (the amount of heat per unit of time); F is the cross-sectional area, normal to the direction of heat flux; DT / DL - change in temperature in the direction of the heat flux, i.e. Temperature gradient.

The coefficient λ is expressed in W / M⋅K (Kcal / M⋅hagrad), called the thermal conductivity coefficient, it depends on the physicochemical properties of the material and temperature of the material. The coefficient λ shows how much heat will go per hour through the material with a surface of 1 m 2, a thickness of 1 m with a temperature difference of 1 °. In tab. 7.15; 7.16 shows the values \u200b\u200bof the coefficients of thermal conductivity of metals, air, water vapor, water at different temperatures. Thermal conductivity of refractories and thermal insulation materials, see section 10.

Air performs heat about 100 times less than solid bodies. Water carries out of about 25 times more than air. Wet materials are warm better than dry. The presence of impurities, especially in metals, can cause a change in thermal conductivity by 50-75%.

Stationary thermal conductivity. The thermal conductivity is called stationary, if the temperature difference caused Δt is stored unchanged.

The amount of heat q, which passed through the material (wall) by thermal conductivity, depends on the thickness of the material (wall) - s, m; temperature difference Δt, ° C; Surfaces - F, M 2 and is determined by the equation:

Q \u003d λ (T 1 - T 2) / S, W (kcal / hour).

The coefficient of heat transfer here will be equal to λ / s, i.e. It is directly proportional to the coefficient of thermal conductivity λ and inversely proportional to the wall thickness - S.

Nonstationary thermal conductivity. The thermal conductivity is called nonstationary if the temperature difference Δt is the value of the variable.

The heating rate of solid bodies is directly proportional to the thermal conductivity coefficient of the material ë and inversely proportional to the volumetric heat capacity of Cρ, which characterizes the accumulating ability, whose ratio is called the temperature coefficient:

a \u003d λ / cρ, m 2 / hour.

For the processes of non-stationary thermal conductivity, the temperature coefficient "A" has the same value as the thermal conductivity coefficient "λ" with stationary heat transfer mode.

The duration of the heating of the wall with sufficient accuracy for technical calculations can be determined by the Gruce-Mermallo formula:

τ ≈ 0.35 s 2 / a, an hour, where: s is the wall thickness; a - temperature coefficient (for shamot 0.0015-0.0025 m 2 / h).

Duration of heating masonry from chamoite refractory brick: τ ≈ 175 ⋅ s 2, hour.

The depth of heating the wall of any thickness and with any change in surface temperature can be determined by the formula:

S PR \u003d 0.17 ⋅ 10 -3 T P.Sr ⋅ √τ, m,

where: T P.SR is the average surface temperature over the heating period in ° C.

If S is more than the thickness of the material (wall) s, the stationary process comes. If s Pr.< S, то количество тепла, аккумулированное стенкой Q АКК. можно определить по формуле Грум-Гржимайло:

Q acc. \u003d 0.56 ⋅ T. √T P.Sr ⋅ τ, kcal / m 2 ⋅ period.

Q acc. \u003d 2.345 ⋅ T. √T P.Sr ⋅ τ, kj / m 2 ⋅ period.

Here T is. - the temperature of the wall surface in ° C by the end of the heating period; τ - hour.

Table 7.15.Thermal conductivity of metals, values \u200b\u200bof ë are given in W / m ⋅ K (kcal / m ⋅ h ⋅ hail)

Metals and alloys	Temperature melting, ° С	Temperature, ° С
0	100	200	300	400	500
1	2	3	4	5	6	7	8
Aluminum	659	202,4 (174)	204,7 (176)	214,6 (184,5)	230,3 (198)	248,9 (214)	-
Iron	1535	60,5 (52,0)	55,2 (47,5)	51,8 (44,5)	48,4 (41,6)	45,0 (38,7)	39,8 (34,2)
Brass	940	96,8 (83,2)	103,8 (89,2)	108,9 (93,6)	114,0 (98,0)	115,5 (99,3)	-
Copper	1080	387,3 (333)	376,8 (324)	372,2 (320)	366,4 (315)	508,6 (312)	358,2 (308)
Nickel	1450	62,2 (53,5)	58,5 (50,3)	57,0 (49)	55,2 (47,5)	-	-
Tin	231	62,2 (53,5)	58,5 (50,3)	57,0 (49)	-	-	-
Lead	327	34,5 (29,7)	34,5 (29,7)	32,9 (28,3)	31,2 (26,8)	-	-
Silver	960	418,7 (360)	411,7 (354)	-	-	-	-
1	2	3	4	5	6	7	8
Steel (1% C)	1500	-	44,9 (38,6)	44,9 (38,6)	43,3 (37,2)	39,8 (34,2)	38,0 (32,7)
Tantalum	2900	55,2 (47,5)	-	-	-	-	-
Zinc	419	112,2 (96,5)	110,5 (95,0)	107,1 (92,1)	101,9 (87,6)	93,4 (80,3)	-
Cast iron	1200	50,1 (43,1)	48,4 (41,6)	-	-	-	-
Cast iron Highcast	1260	51,9 (44,6)	-	-	-	-	-
Bismuth	271,3	8,1 (7,0)	6,7 (5,8)	-	-	-	-
Gold	1063	291,9 (251,0)	294,2 (253,0)	-	-	-	-
Cadmium	320,9	93,0 (80,0)	90,5 (77,8)	-	-	-	-
Magnesium	651	159,3 (137)	-	-	-	-	-
Platinum	1769,3	69,5 (59,8)	72,4 (62,3)	-	-	-	-
Mercury	- 38,87	6,2 (5,35)	9,87 (8,33)	-	-	-	-
Antimony	630,5	18,4 (15,8)	16,7 (14,4)	-	-	-	-
Konstanta (60% Cu + 40% Ni)		22,7 (19,5)	26,7 (23,0)	-	-	-	-
Manganine (84% Cu + 4% Ni + + 12% Mn)		22,1 (19,0)	26,3 (22,6)	-	-	-	-
Nickel silver		29,1 (25,0)	37,2 (32,0)	-	-	-	-

Table 7.16. Coefficients of thermal conductivity of air, water vapor and water, W / m ⋅ K (kcal / m ⋅ h ⋅ hail)

Wednesday	Temperature ° S.
0	100	200	300	500
Air	0,0237 (0,0204)	0,03 (0,0259)	0,0365 (0,0314)	0,0420 (0,0361)	0,0526 (0,0452)
Water par	-	0,0234 (0,0201)	0,03 (0,0258)	0,0366 (0,0315)	-
	0	20	30	70	100
Water	0,558 (0,48)	0,597 (0,513)	0,644 (0,554)	0,663 (0,57)	0,682 (0,586)

To determine the heat loss through the walls of the furnace, through the unshielded walls of the boiler and, for the determination of the outer surface temperatures, graphs and diagrams see applications.

The norms of thermal losses and the limiting thickness of thermal insulation are shown in Table 7.17; 7.18; 7.19.

Table 7.17. Limit thickness of thermal insulation for pipelines laid in rooms and outdoors Table 7.18. Limit thickness of thermal insulation for water heat pipes laid in disadvantaged channels Table 7.19. Norms of thermal losses isolated surfaces indoors of power plants with a calculated air temperature of 25 ° C, W / m

Outer diameter of the pipe, mm	Coolant temperature, ° С														Outer diameter of the pipe, mm
50	75	100	125	150	200	250	300	350	400	450	500	550	600
1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16
	12 14 15 16 17 19 26 31	19 23 26 28 30 32 38 47	27 33 36 38 43 45 52 62	35 41 46 50 57 61 68 76	43 50 57 62 68 72 79 88	58 68 76 84 91 95 105 117	74 86 98 105 115 122 130 146	90 105 119 126 140 147 159 177	105 122 138 149 164 173 186 205	121 139 158 169 188 198 212 234	136 158 170 192 218 225 238 263	152 175 199 213 236 250 264 291	168 194 221 235 262 275 291 331	183 213 242 255 285 300 318 349	20 32 48 57 76 89 108 133
1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16
	36 40 44 49 52 58 62 70 77 95 110 128 157 174 244 308 337 58	52 58 60 69 76 81 87 96 105 128 145 168 192 221 303 372 425 68	70 77 81 91 99 107 114 127 139 163 186 209 238 262 349 431 447 76	84 93 99 110 121 130 139 155 169 198 221 256 279 308 407 500 570 85	98 108 116 129 142 152 163 180 198 227 256 279 320 349 465 580 630 93	130 144 154 166 186 204 221 238 256 294 325 366 400 430 582 700 768 110	163 178 192 213 233 254 273 294 314 360 395 448 483 523 680 837 907 127	193 212 228 254 279 303 326 353 379 430 470 518 558 610 790 965 1045 144	213 247 264 295 324 349 374 406 435 495 547 600 645 700 910 1090 1190 160	256 282 302 336 369 400 430 465 500 565 616 675 727 780 998 1230 1340 178	287 318 337 375 413 448 482 520 558 628 686 750 808 866 1130 1245 1475 195	318 350 371 416 460 498 536 577 618 700 762 825 885 948 1235 1485 1630 210	349 384 410 458 505 547 586 633 680 767 830 900 970 1035 1340 1625 1750 228	378 416 445 498 550 598 645 693 738 825 900 975 1045 1115 1450 1740 1910 244	159 194 219 273 325 377 426 478 529 630 720 820 920 1020 1420 1820 2000 Flat wall, m 2

Note:

For equipment and pipelines operating on steam and drainage selection, the values \u200b\u200bobtained by the table are multiplier to the following coefficients:

Diameter, mm 32 108 273 720 1020 2000 (and flat wall)

The coefficient of 1.01 1.06 1.09 1,12 1,16 1,22

In the direction of the decline, it is started to be found at the thickness of the aqueous layer between the spherical (with a radius of curvature about 1 m) and flat

As a result of heat exchange between the steam and liquid, only the top layer of the fluid takes the saturation temperature corresponding to the average pressure of the drain. The temperature of the bulk of the fluid will remain below the saturation temperature. The heating of the fluid proceeds slowly due to the low value of the coefficient of the temperature of the liquid propane or butane. For example, liquid propane on the saturation line at a temperature of TS - 20 ° C A \u003d 0.00025 M- / h, whereas for water, which is one of the most inert in thermal ratio of substances, the value of the coefficient of thermal conductivity at the same temperature will be a \u003d 0.00052 m / h.

The thermal conductivity and temperature of wood depends on its density, since, in contrast to heat capacity, these properties affect the presence of wheels of the cavities of the cells filled with air. The thermal conductivity coefficient of absolutely dry wood increases with increasing density, and the temperature coefficient falls. When the cell cavities are filling with water, heat thermal conductivity increases, and the temperature is reduced. Thermal conductivity of wood along the fibers is greater than across.

Which depends on the sharply differing values \u200b\u200bof these coefficients for substances of coal, air and water. Thus, the specific heat capacity of water is three times, and the coefficient of thermal conductivity is 25 times more than air, therefore the coefficients of heat and temperature increases with increasing moisture in coals (Fig. 13).

The device shown in fig. 16 on the left, serves to measure the heat and the temperature of bulk materials. In this case, the test material is placed in the space formed by the inner surface of the cylinder 6 and the cylindrical heater 9 placed along the axis of the instrument. To reduce the axial streams, the measuring unit is equipped with covers 7, 8 from the heat insulation material. In a shirt formed by internal and outer cylinders, the water of constant temperature circulates. As in the previous case, the temperature difference is measured by a differential thermocouple, one paw 1 is reinforced near the cylindrical heater, and the other 2 is on the inner surface of the cylinder with the test material.

To the similar formula, we will come if we consider the time required to evaporate a separate drop of liquid. The temperature of the liquids of water type is usually small. In this regard, the heating of the drop occurs relatively slowly during the time of O / chin, it suggests that the evaporation of the liquid occurs only from the surface of the drop without significant warm-up

In shallow water, water heating is carried out not only from above due to the processes of heat exchange with the atmosphere, but also from the bottom, from the bottom side, which due to low temperature and relatively low heat capacity is quickly heated. At night, the bottom transmits the heat of water layer accumulated over the day, and a kind of greenhouse effect occurs.

In these expressions of the poison and H (in the steels) - heat of absorption and reaction (positive at exothermic of reaction), and the remaining designations are indicated above. The coefficient of thermal conductivity for water is about 1.5 10 "cm 1sek. Functions and

The thermal conductivity and temperature of drilling fluids are significantly less studied. In thermal calculations, the coefficient of thermal conductivity, according to V. N. Dakhnov and D. I. Dyakonov, as well as B. I. Esman, and others, take the same as the water - 0.5 kcal / Mr.-C. According to reference data, the thermal conductivity coefficient of drilling fluids is 1.29 kcal / m-h. S. M. Kuliev and others offered to calculate the coefficient of thermal conductivity equation

For approximate calculations of the processes of water evaporation in the air and condensation of water from wet air, the ratio of Lewis can be used, since the ratio of the coefficient of thermal conductivity to the diffusion coefficient at 20 ° C is 0.835, which is not very different from the unit. In the G5-2 section, the processes occurring in wet air were studied using the characteristic of the specific moisture content of enthalpy. Therefore, it would be useful to convert equation (16-36) so that in its right part instead of partial

In equations (VII.3) and (VII.4) and boundary conditions (VII.5), the following notation Ti and T - respectively, the temperature of the concealed and unexwithing layers - the temperature of the medium T p is the cryoscopic temperature A and U2 - respectively, the temperature of these layers, respectively A \u003d KIL IFI), MV A.1 is the coefficient of thermal conductivity for frozen meat, W / (M-) A.2 - the same for chilled meat, W / (M-) Q and SG - the specific heat capacity of frozen and cooled Meat, J / (kg-k) PI IR2 - the density of frozen and chilled meat p1 \u003d pj \u003d 1020 kg / m - the thickness of the frozen layer, counted from

Page 1.

The thermal conductivity of water is approximately 5 times higher than the thermal conductivity of the oil. It increases with an increase in pressure, but at pressures that occur in hydrodynamic transmissions, it can be accepted constant.

The thermal conductivity of water is approximately 28 times the thermal conductivity of the air. In accordance with this, the heat loss is increasing when the body is immersed in water or contact with it, and this largely determines the thermal capacity of a person in air and in water. For example, when - (- 33, air seems warm to us, and the same temperature of the water is indifferent. The air temperature 23 seems to us indifferent, and the water of the same temperature is cool. When - (- 12 air seems cool, and water is cold .

The thermal conductivity of water and water vapor g is undoubtedly studied better than all other substances.

Dynamic viscosity (x (pa-s of some aqueous solutions. | Change in the mass heat capacity of aqueous solutions of some salts, depending on the concentration of the solution. | Thermal conductivity of some solutions depending on the concentration at 20 s.

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 with increasing temperature increases.

The thermal conductivity of water is much larger than other liquids (except metals) and varies abnormally: up to 150 ° C and only then starting to decrease. Water electrical conductivity is very small, but increases markedly with rising and temperature, and pressure. Critical water temperature is 374 s, critical pressure 218 atm.

The thermal conductivity of water is much larger than other liquids (except metals), and it also changes abnormally: up to 150 s increases and only then begins to decrease. Water electrical conductivity is very small, but increases markedly with rising and temperature, and pressure. Critical water temperature is 374 s, critical pressure 218 atm.

Dynamic viscosity C (pa-s of some aqueous solutions. | Change the mass heat capacity of aqueous solutions of some salts, depending on the concentration of the solution. | Thermal conductivity of some solutions depending on the concentration at 20 s.

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

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

The thermal conductivity of water is very insignificant compared to the thermal conductivity of other substances; So, the thermal conductivity of the plug - 0 1; Asbestos - 0 3 - 0 6; concrete - 2 - 3; wood - 0 3 - 1 0; Brick-1 5 - 2 0; Ice - 5 5 cal / cm s degrees.

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

The thermal conductivity of Water PRN 25 is 1 43 - 10 - 3 kal / cm-s.

Since the thermal conductivity of water (I 0 5 kcal / m - h - hail) is approximately 25 times greater than that of immobally air, air displacement with water increases the thermal conductivity of the porous material. With quick freezing and formation in the pores of building materials, no ice, but snow (I 0 3 - 0 4), as we showed our observations, the thermal conductivity of the material, on the contrary, is somewhat reduced. The correct accounting of the moisture content of materials is of great importance for the heat engineering calculations of structures both overhead and underground, such as water-channel.

Water is a unique substance that has a complex molecular structure, to the end not yet studied. Regardless of the aggregate state, the H2O molecules are firmly related, which determines the many physical properties of water and its solutions. Let's find out whether the usual water has heat and electrical conductivity.

The main physical properties of H2O include:

• density;
• transparency;
• color;
• smell;
• taste;
• temperature;
• compressibility;
• radioactivity;
• heat and electrical conductivity.

The latest characteristics of the thermal conductivity and water conductivity are very unstable and depend on many factors. Consider them in more detail.

Electrical conductivity

Electric current is a one-sided movement of negatively charged particles - electrons. Some substances can carry these particles, and some are not. This ability is expressed in a numeric form and is the value of electrical conductivity.

Until now, there are discussions about whether the electrical conductivity has clean water. It is capable of conducting a current, but very bad. The electrical conductivity of the distillate is explained by the fact that H2 O molecules are partially disintegrated by H + and OH- ions. Electrochemicals move with positively charged hydrogen ions, which are capable of moving into the thickness of water.

From which the fluid conductivity depends

The electrical conductivity of H2 O depends on factors such as:

• the presence and concentration of ion impurities (mineralization);
• nature of ions;
• fluid temperature;
• water viscosity.

The first two factors are defining. Therefore, the value of the fluid electrical conductivity is calculated, we can judge the degree of mineralization.

In nature there is no clean water. Even spring is a solution of salts, metals and other electrolyte impurities. These are primarily Na +, K +, Ca2 +, Cl-, SO4 2-, HCO3 ions. It also may include weak electrolytes, which are unable to change the property strongly. These include Fe3 +, Fe2 +, Mn2 +, Al3 +, NO3 -, HPO4 - and others. It is capable of a strong effect on the electrical conductivity only in the case of a high concentration, such as, for example, it happens in wastewater with waste production. Interestingly, the presence of impurities in water, which is in the state of ice, does not affect its ability to carry out electricity.

Electricity waters

Sea water is capable of carrying out electrical current than fresh. This is explained by the presence of a dissolved NaCl salt in it, which is a good electrolyte. The mechanism for increasing the conductivity can be described as follows:

1. Sodium chloride when dissolved in water disintegrates on Na + and Cl- ions that have different charges.
2. Na + ions attract electrons, as they have the opposite charge.
3. The movement of sodium ions in the thickness of water leads to the movement of electrons, which, in turn, leads to the occurrence of electric current.

Thus, the electrical conductivity of water is determined by the presence of salts and other impurities in it. What are them less, the lower the ability to carry out an electric current. Distilled water has almost zero.

Measuring electrical conductivity

Measurement of electrical conductivity of solutions is carried out using conductometers. These are special devices whose principle is based on the analysis of the ratio of electrical conductivity and concentration of electrolyte impurities. To date, there are many models that are capable of measuring the electrical conductivity of not only high-concentrated solutions, but also pure distilled water.

Thermal conductivity

The thermal conductivity is the ability of a physical substance to heat from heated parts to a colder. Water, like other substances, has such a property. Heat transmission occurs either from the molecule to the H2 O molecule, which is a molecular type of thermal conductivity, or when moving fluid flows - turbulent type.

The thermal conductivity of water is several times higher than that of other liquid substances, with the exception of molten metals - they have even higher this indicator.

The ability of water to conduct heat depends on two factors: pressure and temperature. With increasing pressure, the conduction indicator grows, with an increase in temperature to 150 ° C grows, then begins to decrease.