Which is necessary to change the temperature of the working fluid, in this case, air, by one degree. The heat capacity of air directly depends on temperature and pressure. At the same time, various methods can be used to study different types of heat capacity.

Mathematically, the heat capacity of air is expressed as the ratio of the amount of heat to the increment in its temperature. The heat capacity of a body with a mass of 1 kg is usually called the specific heat. The molar heat capacity of air is the heat capacity of one mole of a substance. Specified heat capacity - J / K. Molar heat capacity, respectively, J / (mol * K).

Heat capacity can be considered a physical characteristic of a substance, in this case air, if the measurement is carried out under constant conditions. Most often, these measurements are carried out at constant pressure. This is how the isobaric heat capacity of air is determined. It increases with increasing temperature and pressure, and is also a linear function of these values. In this case, the temperature change occurs at constant pressure. To calculate the isobaric heat capacity, it is necessary to determine the pseudocritical temperature and pressure. It is determined using reference data.

Heat capacity of air. Features of the

Air is a gas mixture. When considering them in thermodynamics, the following assumptions are made. Each gas in the mixture must be evenly distributed throughout the volume. Thus, the volume of the gas is equal to the volume of the entire mixture. Each gas in the mixture has its own partial pressure, which it exerts on the walls of the vessel. Each of the components of the gas mixture must have a temperature equal to the temperature of the entire mixture. In this case, the sum of the partial pressures of all components is equal to the mixture pressure. The calculation of the heat capacity of air is carried out on the basis of data on the composition of the gas mixture and the heat capacity of individual components.

Specific heat characterizes a substance ambiguously. From the first law of thermodynamics, we can conclude that the internal energy of a body changes not only depending on the amount of heat received, but also on the work done by the body. Under different conditions of the heat transfer process, the work of the body may differ. Thus, the same amount of heat imparted to the body can cause changes in temperature and internal energy of the body that are different in value. This feature is typical only for gaseous substances. Unlike solids and liquids, gaseous substances can greatly change the volume and do work. That is why the heat capacity of air determines the nature of the thermodynamic process itself.

However, at a constant volume, air does not do work. Therefore, the change in internal energy is proportional to the change in its temperature. The ratio of the heat capacity in a constant pressure process to the heat capacity in a constant volume process is part of the adiabatic process formula. It is denoted by the Greek letter gamma.

From the history

The terms "heat capacity" and "amount of heat" do not describe their essence very well. This is due to the fact that they came to modern science from the theory of caloric, which was popular in the eighteenth century. The followers of this theory considered heat as a kind of weightless substance that is contained in bodies. This substance can neither be destroyed nor created. The cooling and heating of bodies was explained by a decrease or an increase in the caloric content, respectively. Over time, this theory was found to be untenable. She could not explain why the same change in the internal energy of any body is obtained when different amounts of heat are transferred to it, and also depends on the work done by the body.

Under specific heat Substances understand the amount of heat that needs to be reported or subtracted from a unit of a substance (1 kg, 1 m 3, 1 mol) in order to change its temperature by one degree.

Depending on the unit of a given substance, the following specific heat capacities are distinguished:

Mass heat capacity FROM, referred to 1 kg of gas, J / (kg ∙ K);

Molar heat capacity µС per 1 kmol of gas, J / (kmol ∙ K);

Volumetric heat capacity FROM', referred to 1 m 3 of gas, J / (m 3 ∙ K).

Specific heat capacities are related to each other by the ratio:

Where υ n- specific volume of gas under normal conditions (n.u.), m 3 / kg; µ - molar mass of gas, kg / kmol.

The heat capacity of an ideal gas depends on the nature of the process of supplying (or removing) heat, on the atomicity of the gas and temperature (the heat capacity of real gases also depends on pressure).

Relationship between mass isobaric C P and isochoric C V heat capacities is set by the Mayer equation:

C P - C V = R, (1.2)

Where R - gas constant, J / (kg ∙ K).

When an ideal gas is heated in a closed vessel of constant volume, heat is spent only on changing the energy of motion of its molecules, and when heated at constant pressure, due to the expansion of the gas, work is simultaneously performed against external forces.

For molar heat capacities, Mayer's equation has the form:

μС р - μС v = μR, (1.3)

Where µR= 8314J / (kmol ∙ K) - universal gas constant.

Ideal gas volume V n reduced to normal conditions is determined from the following relation:

(1.4)

Where R n- pressure under normal conditions, R n= 101325 Pa = 760 mm Hg; T n- temperature under normal conditions, T n= 273.15 K; P t, V t, T t- working pressure, volume and gas temperature.

The ratio of isobaric heat capacity to isochoric heat is denoted k and called the adiabatic exponent:

(1.5)

From (1.2) and taking into account (1.5), we obtain:

For accurate calculations, the average heat capacity is determined by the formula:

(1.7)

In thermal calculations of various equipment, the amount of heat that is required to heat or cool gases is often determined:

Q = C ∙ m∙(t 2 - t 1), (1.8)

Q = C ′ ∙ V n∙(t 2 - t 1), (1.9)

Where V n- gas volume at normal level, m 3.

Q = µC ∙ ν∙(t 2 - t 1), (1.10)

Where ν - amount of gas, kmol.

Heat capacity. Using heat capacity to describe processes in closed systems

In accordance with equation (4.56), the heat can be determined if the change in the entropy S of the system is known. However, the fact that entropy cannot be measured directly creates some complications, especially when describing isochoric and isobaric processes. There is a need to determine the amount of heat using an experimentally measured quantity.

The heat capacity of the system can serve as such a quantity. The most general definition of heat capacity follows from the expression of the first law of thermodynamics (5.2), (5.3). Based on it, any capacity of the system C with respect to work of the form m is determined by the equation

C m = dA m / dP m = P m d e g m / dP m, (5.42)

where C m is the capacity of the system;

P m and g m are the generalized potential and state coordinate of the form m, respectively.

The value of C m shows how much work of the type m must be done under given conditions in order to change the m-th generalized potential of the system per unit of its measurement.

The concept of the capacity of a system in relation to a particular work in thermodynamics is widely used only when describing the thermal interaction between the system and the environment.

The capacity of the system in relation to heat is called the heat capacity and is given by the equality

С = d e Q / dT = Td e S heat / dT. (5.43)

In this way, Specific heat can be defined as the amount of heat that must be supplied to the system in order to change its temperature by one Kelvin.

Heat capacity, like internal energy and enthalpy, is an extensive quantity proportional to the amount of matter. In practice, use is made of the heat capacity per unit mass of the substance - specific heat, and the heat capacity, referred to one mole of a substance, is molar heat capacity... Specific heat in SI is expressed in J / (kg K), and molar in J / (mol K).

Specific and molar heat capacities are related by the ratio:

С mol = С beats М, (5.44)

where M is the molecular weight of the substance.

Distinguish true (differential) heat capacity, determined from equation (5.43) and representing an elementary increase in heat with an infinitesimal change in temperature, and average heat capacity, which is the ratio of the total amount of heat to the total temperature change in this process:

Q / DT. (5.45)

The relationship between the true and average specific heat is established by the ratio

At constant pressure or volume, heat and, accordingly, heat capacity acquire the properties of a function of state, i.e. become characteristics of the system. It is these heat capacities - isobaric С Р (at constant pressure) and isochoric С V (at constant volume) that are most widely used in thermodynamics.

If the system is heated at a constant volume, then, in accordance with expression (5.27), the isochoric heat capacity C V is written in the form

C V = . (5.48)

If the system is heated at constant pressure, then, in accordance with equation (5.32), the isobaric heat capacity С Р appears in the form

C P = . (5.49)

To find the relationship between С Р and С V, it is necessary to differentiate the expression (5.31) by temperature. For one mole of an ideal gas, this expression, taking into account equation (5.18), can be represented in the form

H = U + pV = U + RT. (5.50)

dH / dT = dU / dT + R, (5.51)

and the difference between the isobaric and isochoric heat capacities for one mole of an ideal gas is numerically equal to the universal gas constant R:

C P - C V = R. (5.52)

The heat capacity at constant pressure is always greater than the heat capacity at constant volume, since the heating of a substance at constant pressure is accompanied by the work of gas expansion.

Using the expression for the internal energy of an ideal monatomic gas (5.21), we obtain the value of its heat capacity for one mole of an ideal monatomic gas:

C V = dU / dT = d (3/2 RT) dT = 3/2 R "12.5 J / (mol · K); (5.53)

C P = 3 / 2R + R = 5/2 R "20.8 J / (mol · K). (5.54)

Thus, for monoatomic ideal gases C V and C p does not depend on temperature, since all supplied thermal energy is spent only on acceleration of translational motion. For polyatomic molecules, along with a change in the translational motion, a change in the rotational and vibrational intramolecular motion can also occur. For diatomic molecules, additional rotational motion is usually taken into account, as a result of which the numerical values ​​of their heat capacities are:

C V = 5/2 R "20.8 J / (mol · K); (5.55)

C p = 5/2 R + R = 7/2 R "29.1 J / (mol · K). (5.56)

Along the way, let us touch on the heat capacities of substances in other (except for gaseous) states of aggregation. To estimate the heat capacities of solid chemical compounds, the approximate additivity rule of Neumann and Kopp is often used, according to which the molar heat capacity of chemical compounds in the solid state is equal to the sum of the atomic heat capacities of the elements included in this compound. So, the heat capacity of a complex chemical compound, taking into account the Dulong and Petit rule, can be estimated as follows:

C V = 25n J / (mol K), (5.57)

where n is the number of atoms in the molecules of the compounds.

The heat capacities of liquids and solids near the melting (crystallization) temperature are almost equal. Near the normal boiling point, most organic liquids have a specific heat capacity of 1700 - 2100 J / kg · K. In the intervals between these temperatures of phase transitions, the heat capacity of the liquid can differ significantly (depending on the temperature). In general, the dependence of the heat capacity of solids on temperature in the range 0 - 290K in most cases is well reproduced by the semiempirical Debye equation (for a crystal lattice) in the low-temperature region

C P "C V = eT 3, (5.58)

in which the proportionality coefficient (e) depends on the nature of the substance (empirical constant).

The temperature dependence of the heat capacity of gases, liquids and solids at normal and high temperatures is usually expressed using empirical equations in the form of power series:

C P = a + bT + cT 2 (5.59)

C P = a + bT + c "T -2, (5.60)

where a, b, c and c "are empirical temperature coefficients.

Returning to the description of processes in closed systems using the method of heat capacities, we write down some of the equations given in Section 5.1 in a slightly different form.

Isochoric process. Expressing the internal energy (5.27) in terms of the heat capacity, we obtain

dU V = dQ V = U 2 - U 1 = C V dT = C V dT. (5.61)

Taking into account that the heat capacity of an ideal gas does not depend on temperature, equation (5.61) can be written as follows:

DU V = Q V = U 2 - U 1 = C V DT. (5.62)

To calculate the value of the integral (5.61) for real mono- and polyatomic gases, it is necessary to know the specific form of the functional dependence C V = f (T) of the type (5.59) or (5.60).

Isobaric process. For the gaseous state of matter, the first law of thermodynamics (5.29) for this process, taking into account the recording of the work of expansion (5.35) and using the method of heat capacities, is written as follows:

Q P = C V DT + RDT = C P DT = DH (5.63)

Q P = DH P = H 2 - H 1 = C P dT. (5.64)

If the system is an ideal gas and the heat capacity С Р does not depend on temperature, the relation (5.64) turns into (5.63). To solve equation (5.64), which describes a real gas, it is necessary to know the specific form of the dependence C p = f (T).

Isothermal process. Change in the internal energy of an ideal gas in a process running at a constant temperature

dU T = C V dT = 0. (5.65)

Adiabatic process. Since dU = C V dT, then for one mole of an ideal gas, the change in internal energy and the work performed are equal, respectively:

DU = C V dT = C V (T 2 - T 1); (5.66)

And fur = -DU = C V (T 1 - T 2). (5.67)

Analysis of equations characterizing various thermodynamic processes under the following conditions: 1) p = сonst; 2) V = const; 3) T = сonst and 4) dQ = 0 shows that they can all be represented by the general equation:

pV n = const. (5.68)

In this equation, the exponent "n" can take values ​​from 0 to ¥ for different processes:

1.isobaric (n = 0);

2.isothermal (n = 1);

3.isochoric (n = ¥);

4.adiabatic (n = g; where g = C P / C V - adiabatic coefficient).

The relations obtained are valid for an ideal gas and are a consequence of its equation of state, and the processes considered are particular and limiting manifestations of real processes. Real processes, as a rule, are intermediate, proceed at arbitrary values ​​of "n" and are called polytropic processes.

If we compare the work of expansion of an ideal gas, produced in the considered thermodynamic processes, with a change in volume from V 1 to V 2, then, as can be seen from Fig. 5.2, the greatest work of expansion is performed in the isobaric process, less in the isothermal process and even less in the adiabatic process. For an isochoric process, work is zero.

Fig. 5.2. P = f (V) - dependence for various thermodynamic processes (shaded areas characterize the work of expansion in the corresponding process)

Transport energy (refrigerated transport) Air humidity. Heat capacity and enthalpy of air

Air humidity. Heat capacity and enthalpy of air

Atmospheric air is a mixture of dry air and water vapor (0.2% to 2.6%). Thus, the air can almost always be considered humid.

A mechanical mixture of dry air with water vapor is called moist air or an air-steam mixture. The maximum possible content of vaporous moisture in the air m bp depends on temperature t and pressure P mixtures. When it changes t and P air can go from initially unsaturated to saturation with water vapor, and then excess moisture will begin to fall out in the gas volume and on the enclosing surfaces in the form of fog, frost or snow.

The main parameters characterizing the state of humid air are: temperature, pressure, specific volume, moisture content, absolute and relative humidity, molecular weight, gas constant, heat capacity and enthalpy.

According to Dalton's law for gas mixtures total pressure of humid air (P) is the sum of the partial pressures of dry air P c and water vapor P p: P = P c + P p.

Similarly, the volume V and mass m of humid air will be determined by the ratios:

V = V c + V p, m = m c + m p.

Density and specific volume of humid air (v) is determined by:

Molecular weight of humid air:

where B is barometric pressure.

Since the air humidity increases continuously during the drying process, and the amount of dry air in the vapor-air mixture remains constant, the drying process is judged by how the amount of water vapor per 1 kg of dry air changes, and all indicators of the vapor-air mixture (heat capacity, moisture content, enthalpy, etc.) etc.) refers to 1 kg of dry air in humid air.

d = m p / m c, g / kg, or, X = m p / m c.

Absolute air humidity- mass of steam in 1 m 3 of moist air. This value is numerically equal to.

Relative humidity - is the ratio of the absolute humidity of unsaturated air to the absolute humidity of saturated air under given conditions:

here, but more often the relative humidity is given as a percentage.

For the density of humid air, the ratio is valid:

Specific heat humid air:

c = s c + s n × d / 1000 = s c + s n × X, kJ / (kg × ° C),

where c c is the specific heat capacity of dry air, c c = 1.0;

c p - specific heat capacity of steam; with n = 1.8.

The heat capacity of dry air at constant pressure and small temperature ranges (up to 100 о С) for approximate calculations can be considered constant, equal to 1.0048 kJ / (kg × ° С). For superheated steam, the average isobaric heat capacity at atmospheric pressure and low degrees of superheat can also be assumed constant and equal to 1.96 kJ / (kg × K).

Enthalpy (i) of humid air- this is one of its main parameters, which is widely used in the calculations of drying plants, mainly to determine the heat consumed for the evaporation of moisture from the materials to be dried. The enthalpy of humid air is related to one kilogram of dry air in a vapor-air mixture and is defined as the sum of the enthalpies of dry air and water vapor, that is

i = i c + i n × X, kJ / kg.

When calculating the enthalpy of mixtures, the starting point of reference for the enthalpies of each of the components must be the same. For calculations of moist air, it can be assumed that the enthalpy of water is zero at 0 ° C, then the enthalpy of dry air is also counted from 0 ° C, that is, i in = with in * t = 1.0048t.

the Russian Federation USSR State Standard Protocol

ГСССД 8-79 Liquid and gaseous air. Density, enthalpy, entropy and isobaric heat capacity at temperatures of 70-1500 K and pressures of 0.1-100 MPa

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STATE SERVICE OF STANDARD REFERENCE DATA

Standard reference tables

AIR LIQUID AND GASEOUS. DENSITY, ENTHALPY, ENTHROPY AND ISOBAR CAPACITY AT TEMPERATURES 70-1500 K AND PRESSURES 0.1-100 MPa

Tables of Standard Reference Data
Liquid and gaseous air Density, enthalpy, entropy and isobaric heat capacity at temperatures from 70 to 1500 K and pressures from 0.1 to 100 MPa

DEVELOPED by the All-Union Scientific Research Institute of the Metrological Service, the Odessa Institute of Marine Engineers, the Moscow Order of Lenin Power Engineering Institute

RECOMMENDED FOR APPROVAL by the Soviet National Committee for the Collection and Evaluation of Numerical Data in the Field of Science and Technology of the Presidium of the USSR Academy of Sciences; All-Union Research Center of the State Service of Standard Reference Data

APPROVED by the GSSSD expert commission consisting of:

Cand. tech. sciences N.E. Gnezdilova, Dr. Sciences IF Golubeva, Dr. of chem. Sci. L.V. Gurvich, Dr. Sci. V.A. Rabinovich, Doctor of Technical Sciences Sciences A.M. Sirota

PREPARED FOR APPROVAL by the All-Union Scientific Research Center of the State Service of Standard Reference Data

The use of standard reference data is mandatory in all sectors of the national economy

These tables contain the most important for practice values ​​of density, enthalpy, entropy and isobaric heat capacity of liquid and gaseous air.

The calculation of the tables is based on the following principles:

1. The equation of state, displaying with high accuracy reliable experimental data on the,, -dependence, can provide a reliable calculation of the caloric and acoustic properties by the known thermodynamic relations.

2. Averaging the coefficients of a large number of equations of state, equivalent from the point of view of the accuracy of describing the initial information, makes it possible to obtain an equation that reflects the entire thermodynamic surface (for a selected set of experimental data among equations of the accepted type). Such averaging makes it possible to estimate the possible random error of the calculated values ​​of thermal, caloric and acoustic quantities, without taking into account the influence of the systematic error of experimental data and the error caused by the choice of the form of the equation of state.

The averaged equation of state for liquid and gaseous air has the form

Where; ; ...

The equation is based on the most reliable experimental density values ​​obtained in the works and covering the temperature range 65-873 K and pressures 0.01-228 MPa. The experimental data are described by an equation with a mean square error of 0.11%. The coefficients of the averaged equation of state were obtained as a result of processing a system of 53 equations, which are equivalent in terms of the accuracy of describing the experimental data. In the calculations, the following values ​​of the gas constant and critical parameters were taken: 287.1 J / (kg · K); 132.5K; 0.00316 m / kg.

Coefficients of the averaged air state equation:

Enthalpy, entropy and isobaric heat capacity were determined by the formulas

Where,, - enthalpy, entropy and isochoric heat capacity in the ideal gas state. The values ​​and are determined from the relations

Where and - enthalpy and entropy at temperature; - heat of sublimation at 0 K; - constant (in this work 0).

The value of the heat of sublimation of air is calculated on the basis of data on the heats of sublimation of its components and is equal to 253.4 kJ / kg (in the calculations it is assumed that the air does not contain CO and consists of 78.11% N, 20.96% O and 0.93% Ar by volume). The values ​​of enthalpy and entropy at a temperature of 100 K, which is an auxiliary starting point when integrating the equation for, are 3.48115 kJ / kg and 20.0824 kJ / (kg K), respectively.

The isobaric heat capacity in the ideal gas state is borrowed from the work and approximated by the polynomial

The root mean square error of approximation of the initial data in the temperature range 50-2000 K is 0.009%, the maximum is about 0.02%.

The random errors of the calculated values ​​were calculated with a confidence level of 0.997 using the formula

Where is the average value of the thermodynamic function; - the value of the same function, obtained by the th equation from a system containing equations.

Tables 1-4 show the values ​​of the thermodynamic functions of air, and Tables 5-8 show the corresponding random errors. The error values ​​in Tables 5-8 are presented on a part of the isobars, and the values ​​on the intermediate isobars can be obtained with acceptable accuracy by linear interpolation. The random errors of the calculated values ​​reflect the spread of the latter relative to the averaged equation of state; for density, they are significantly less than the root-mean-square error of describing the initial array of experimental data, which serves as an integral estimate and includes large deviations for some data characterized by scatter.

Table 1

Air density

Continuation

	Kg / m, at, MPa,

table 2

Enthalpy of air

Continuation

	KJ / kg, at, MPa,

Table 3

Air entropy

Continuation

	KJ / (kg, K), at, MPa,

Table 4

Isobaric heat capacity of air

________________

* The text of the document corresponds to the original. - Note from the manufacturer of the database.

Continuation

	KJ / (kg, K), at, MPa,

Table 5. RMS random errors of the calculated density values

,%, at, MPa

Table 6. RMS random errors of the calculated values ​​of enthalpy

KJ / kg, at, MPa

In connection with the use of the virial form, the equations of state of the tables do not pretend to accurately describe the thermodynamic properties in the vicinity of the critical point (126-139 K, 190-440 kg / m).

Information about experimental studies of the thermodynamic properties of air, the method of drawing up the equation of state and calculating tables, the consistency of the calculated values ​​with experimental data, as well as more detailed tables containing additional information about the isochoric heat capacity, the speed of sound, the heat of vaporization, the throttle effect, some derivatives and about properties on the curves of boiling and condensation are given in the work.

BIBLIOGRAPHY

1. Holborn L., Schultre H. die Druckwage und die Isothermen von Luft, Argon und Helium Zwischen 0 und 200 ° C. - Ann. Phys. 1915 m, Bd 47, N 16, S. 1089-1111.

2. Michels A., Wassenaar T., Van Seventer W. Isotherms of air between 0 ° C and 75 ° C and at pressures up to 2200 atm. - Appl. Sci. Res., 1953, vol. 4, No. 1, p. 52-56.

3. Compressibility isotherms of air at temperatures between -25 ° C and -155 ° C and at densities up to 560 Amagats (Pressures up to 1000 atmospheres) / Michels A .. Wassenaar T., Levelt JM, De Graaff W. - Appl ... Sci. Res., 1954, vol. A 4, N 5-6, p. 381-392.

4. Experimental study of specific air volumes / Vukalovich MP, Zubarev VN, Aleksandrov AA, Kozlov AD. - Heat power engineering, 1968, N 1, p. 70-73.

5. Romberg H. Neue Messungen der thermischen ler Luft bei tiefen Temperaturen and die Berechnung der kalorischen mit Hilfe des Kihara-Potentials. - VDl-Vorschungsheft, 1971, - N 543, S. 1-35.

6. Blanke W. Messung der thermischen von Luft im Zweiphasengebiet und Seiner Umgebung. Dissertation zur Erlangung des Grades eines Doctor-Ingenieurs /. Bohum., 1973.

7. Measurement of air density at temperatures of 78-190 K up to a pressure of 600 bar / Wasserman A.A., Golovsky E.A., Mitsevich E.P., Tsymarny V.A., M., 1975. (Dep. In VINITI 28.07 .76 N 2953-76).

8. Landolt H., R. Zahlenwerte und Funktionen aus Physik, Chemie, Astronomic, Geophysik und Technik. Berlin., Springer Verlag, 1961, Bd. 2.

9. Tables of thermal properties of gases. Wachington., Gov. print, off., 1955, XI. (U. S. Dep. Of commerce. NBS. Girc. 564).

10. Thermodynamic properties of air / Sychev V.V., Wasserman A.A., Kozlov A.D. et al. M., Publishing house of standards, 1978.

TEMPERATURE... It is measured in both Kelvin (K) and degrees Celsius (° C). The size of the Celsius degree and the size of the Kelvin are the same for the temperature difference. The relationship between temperatures:

t = T - 273.15 K,

Where t- temperature, ° С, T- temperature, K.

PRESSURE... Wet air pressure p and its components are measured in Pa (Pascal) and multiple units (kPa, GPa, MPa).
Barometric pressure of humid air p b equal to the sum of the partial pressures of dry air p in and water vapor p p :

p b = p b + p p

DENSITY... Density of humid air ρ , kg / m3, is the ratio of the mass of the air-steam mixture to the volume of this mixture:

ρ = M / V = ​​M in / V + M p / V

The density of humid air can be determined by the formula

ρ = 3.488 p b / T - 1.32 p p / T

SPECIFIC GRAVITY... Specific gravity of humid air γ Is the ratio of the weight of moist air to its volume, N / m 3. Density and specific gravity are related by dependence

ρ = γ / g,

Where g- acceleration of gravity, equal to 9.81 m / s 2.

AIR HUMIDITY... The content of water vapor in the air. characterized by two values: absolute and relative humidity.
Absolute air humidity. the amount of water vapor, kg or g, contained in 1 m 3 of air.
Relative air humidity φ expressed in%. the ratio of the partial pressure of water vapor pp contained in the air to the partial pressure of water vapor in the air when it is completely saturated with water vapor p p.n. :

φ = (p p / p p.n.) 100%

The partial pressure of water vapor in saturated humid air can be determined from the expression

lg p bp = 2.125 + (156 + 8.12t c.n.) / (236 + t c.n.),

Where t c.n.- temperature of saturated humid air, ° С.

DEW POINT... Temperature at which the partial pressure of water vapor p p contained in humid air is equal to the partial pressure of saturated water vapor p bp at the same temperature. At dew temperature, moisture condensation from the air begins.

d = M p / M in

d = 622p p / (p b - p p) = 6.22φp bp (p b - φp bp / 100)

SPECIFIC HEAT... The specific heat capacity of humid air c, kJ / (kg * ° C) is the amount of heat required to heat 1 kg of a mixture of dry air and water vapor by 10 and referred to 1 kg of dry air:

c = c b + c n d / 1000,

Where c in- the average specific heat of dry air, taken in the temperature range 0-1000C equal to 1.005 kJ / (kg * ° C); with n - the average specific heat of water vapor, equal to 1.8 kJ / (kg * ° C). For practical calculations in the design of heating, ventilation and air conditioning systems, it is allowed to use the specific heat capacity of humid air c = 1.0056 kJ / (kg * ° C) (at a temperature of 0 ° C and a barometric pressure of 1013.3 GPa)

SPECIFIC ENTHALPY... The specific enthalpy of humid air is the enthalpy I, kJ, referred to 1 kg of dry air mass:

I = 1.005t + (2500 + 1.8068t) d / 1000,
or I = ct + 2.5d

VOLUME EXPANSION RATIO... Temperature coefficient of volumetric expansion

α = 0.00367 ° C -1
or α = 1/273 ° C -1.

MIXTURE PARAMETERS .
Air mixture temperature

t cm = (M 1 t 1 + M 2 t 2) / (M 1 + M 2)

d cm = (M 1 d 1 + M 2 d 2) / (M 1 + M 2)

Specific enthalpy of air mixture

I cm = (M 1 I 1 + M 2 I 2) / (M 1 + M 2)

Where M 1, M 2- mixed air masses

FILTER CLASSES

Application	Cleaning class					Purification degree
	Standards	DIN 24185 DIN 24184	EN 779	EUROVENT 4/5	EN 1882
Coarse filter with low air purity requirements	Rough cleaning	EU1	G1	EU1	—	A%
Filter used for high dust concentration with coarse cleaning, Air conditioning and exhaust ventilation with low requirements for indoor air purity.						65
		EU2	G2	EU2	—	80
		EU3	G3	EU3	—	90
		EU4	G4	EU4	—
Separation of fine dust in ventilation equipment used in rooms with high requirements for air flow. Filter for very fine filtration. The second stage of cleaning (post-treatment) in rooms with average requirements for air purity.	Fine cleaning	EU5	EU5	EU5	—	E%
						60
		EU6	EU6	EU6	—	80
		EU7	EU7	EU7	—	90
		EU8	EU8	EU8	—	95
		EU9	EU9	EU9	—
Extra fine dust cleaning. It is used in rooms with increased requirements for air purity ("clean room"). Final purification of air in rooms with precision technology, surgical units, intensive care wards, in the pharmaceutical industry.	Extra fine cleaning	—	—	—	EU5	FROM%
						97
		—	—	—	EU6	99
		—	—	—	EU7	99,99
		—	—	—	EU8	99,999

CALCULATION OF CALORIFER POWER

Heating, ° С
m 3 / h	5	10	15	20	25	30	35	40	45	50
100	0.2	0.3	0.5	0.7	0.8	1.0	1.2	1.4	1.5	1.7
200	0.3	0.7	1.0	1.4	1.7	2.0	2.4	2.7	3.0	3.4
300	0.5	1.0	1.5	2.0	2.5	3.0	3.6	4.1	4.6	5.1
400	0.7	1.4	2.0	2.7	3.4	4.1	4.7	5.4	6.1	6.8
500	0.8	1.7	2.5	3.4	4.2	5.1	5.9	6.8	7.6	8.5
600	1.0	2.0	3.0	4.1	5.1	6.1	7.1	8.1	9.1	10.1
700	1.2	2.4	3.6	4.7	5.9	7.1	8.3	9.5	10.7	11.8
800	1.4	2.7	4.1	5.4	6.8	8.1	9.5	10.8	12.2	13.5
900	1.5	3.0	4.6	6.1	7.6	9.1	10.7	12.2	13.7	15.2
1000	1.7	3.4	5.1	6.8	8.5	10.1	11.8	13.5	15.2	16.9
1100	1.9	3.7	5.6	7.4	9.3	11.2	13.0	14.9	16.7	18.6
1200	2.0	4.1	6.1	8.1	10.1	12.2	14.2	16.2	18.3	20.3
1300	2.2	4.4	6.6	8.8	11.0	13.2	15.4	17.6	19.8	22.0
1400	2.4	4.7	7.1	9.5	11.8	14.2	16.6	18.9	21.3	23.7
1500	2.5	5.1	7.6	10.1	12.7	15.2	17.8	20.3	22.8	25.4
1600	2.7	5.4	8.1	10.8	13.5	16.2	18.9	21.6	24.3	27.1
1700	2.9	5.7	8.6	11.5	14.4	17.2	20.1	23.0	25.9	28.7
1800	3.0	6.1	9.1	12.2	15.2	18.3	21.3	24.3	27.4	30.4
1900	3.2	6.4	9.6	12.8	16.1	19.3	22.5	25.7	28.9	32.1
2000	3.4	6.8	10.1	13.5	16.9	20.3	23.7	27.1	30.4	33.8

STANDARDS AND REGULATIONS

SNiP 2.01.01-82 - Construction climatology and geophysics

Information about the climatic conditions of specific territories.

SNiP 2.04.05-91 * - Heating, ventilation and air conditioning

These building codes should be observed when designing heating, ventilation and air conditioning in buildings and structures (hereinafter referred to as buildings). When designing, you should also comply with the requirements for heating, ventilation and air conditioning SNiP of the corresponding buildings and premises, as well as departmental standards and other regulatory documents approved and agreed with the Gosstroy of Russia.

SNiP 2.01.02-85 * - Fire safety standards

These standards must be observed when developing projects for buildings and structures.

These standards establish the fire-technical classification of buildings and structures, their elements, building structures, materials, as well as general fire-prevention requirements for structural and planning solutions for premises, buildings and structures for various purposes.

These standards are supplemented and clarified by the fire requirements set out in the SNiP part 2 and in other regulatory documents approved or agreed by Gosstroy.

SNiP II-3-79 * - Construction heat engineering

These building heat engineering standards must be observed in the design of enclosing structures (external and internal walls, partitions, coatings, attic and intermediate floors, floors, fillings of openings: windows, lamps, doors, gates) for new and reconstructed buildings and structures for various purposes (residential, public , industrial and auxiliary industrial enterprises, agricultural and warehouse, with normalized temperature or temperature and relative humidity of the indoor air).

SNiP II-12-77 - Noise protection

These norms and rules must be observed when designing noise protection to ensure permissible sound pressure levels and sound levels in premises at workplaces in industrial and auxiliary buildings and on industrial sites, in residential and public buildings, as well as in residential areas of cities and other settlements.

SNiP 2.08.01-89 * - Residential buildings

These norms and rules apply to the design of residential buildings (apartment buildings, including apartment buildings for the elderly and families with disabled people who move in wheelchairs, hereinafter referred to as families with disabled people, as well as dormitories) up to and including 25 floors.

These rules and regulations do not apply to the design of inventory and mobile buildings.

SNiP 2.08.02-89 * - Public buildings and structures

These rules and regulations apply to the design of public buildings (up to 16 floors inclusive) and structures, as well as public premises built into residential buildings. When designing public premises built into residential buildings, SNiP 2.08.01-89 * (Residential buildings) should be additionally guided.

SNiP 2.09.04-87 * - Administrative and domestic buildings

These standards apply to the design of administrative and residential buildings up to 16 floors, inclusive, and premises of enterprises. These standards do not apply to the design of administrative buildings and public premises.

When designing buildings rebuilt in connection with the expansion, reconstruction or technical re-equipment of enterprises, deviations from these standards in terms of geometric parameters are allowed.

SNiP 2.09.02-85 * - Industrial buildings

These standards apply to the design of industrial buildings and premises. These standards do not apply to the design of buildings and premises for the production and storage of explosives and explosives, underground and mobile (inventory) buildings.

SNiP 111-28-75 - Rules for the production and acceptance of works

Start-up tests of the installed ventilation and air conditioning systems are carried out in accordance with the requirements of SNiP 111-28-75 "Rules for the production and acceptance of works" after mechanical testing of ventilation and related power equipment. The purpose of commissioning tests and adjustment of ventilation and air conditioning systems is to establish the compliance of their operating parameters with design and regulatory indicators.

Before testing, ventilation and air conditioning units must operate continuously and properly for 7 hours.

During start-up tests, the following should be performed:

• Verification of the compliance of the parameters of the installed equipment and elements of ventilation devices adopted in the project, as well as the compliance of the quality of their manufacture and installation with the requirements of TU and SNiP.
• Identification of leaks in air ducts and other elements of systems
• Verification of compliance with the design data of the volumetric flow rates of air passing through the air intake and air distribution devices of general ventilation and air conditioning units
• Checking compliance with the passport data of ventilation equipment in terms of performance and pressure
• Checking the uniformity of heating the heaters. (If there is no heat carrier in the warm season, the uniformity of heating of the heaters is not checked)

TABLE OF PHYSICAL VALUES

Fundamental constants
Constant (number) Avogadro	N A	6.0221367 (36) * 10 23 mol -1
Universal gas constant	R	8.314510 (70) J / (mol * K)
Boltzmann constant	k = R / NA	1.380658 (12) * 10 -23 J / K
Absolute zero temperature	0K	-273.150C
Sound speed in air under normal conditions		331.4 m / s
Acceleration of gravity	g	9.80665 m / s 2
Length (m)
micron	μ (μm)	1 micron = 10 -6 m = 10 -3 cm
angstrom	-	1 - = 0.1 nm = 10 -10 m
yard	yd	0.9144 m = 91.44 cm
foot	ft	0.3048 m = 30.48 cm
inch	in	0.0254 m = 2.54 cm
Area, m2)
square yard	yd 2	0.8361 m 2
square foot	ft 2	0.0929 m 2
square inch	in 2	6.4516 cm 2
Volume, m3)
cubic yard	yd 3	0.7645 m 3
cubic foot	ft 3	28.3168 dm 3
cubic inch	in 3	16.3871 cm 3
gallon (english)	gal (UK)	4.5461 dm 3
gallon (US)	gal (US)	3.7854 dm 3
pint (English)	pt (UK)	0.5683 dm 3
dry pint (US)	dry pt (US)	0.5506 dm 3
liquid pint (US)	liq pt (US)	0.4732 dm 3
fluid ounce (English)	fl.oz (UK)	29.5737 cm 3
fluid ounce (US)	fl.oz (US)	29.5737 cm 3
bushel (US)	bu (US)	35.2393 dm 3
dry barrel (US)	bbl (US)	115.628 dm 3
Weight (kg)
lb.	lb	0.4536 kg
slug	slug	14.5939 kg
gran	gr	64.7989 mg
trade ounce	oz	28.3495 g
Density (kg / m 3)
pound per cubic foot	lb / ft 3	16.0185 kg / m 3
pound per cubic inch	lb / in 3	27680 kg / m 3
slug per cubic foot	slug / ft 3	515.4 kg / m 3
Thermodynamic temperature (K)
Rankine degree	° R	5/9 K
Temperature (K)
degree Fahrenheit	° F	5/9 K; t ° C = 5/9 * (t ° F - 32)
Force, weight (N or kg * m / s 2)
newton	H	1 kg * m / s 2
poundal	pdl	0.1383 H
lbf	lbf	4.4482 H
kilogram-force	kgf	9.807 H
Specific gravity (N / m 3)
lbf per cubic inch	lbf / ft 3	157.087 N / m 3
Pressure (Pa or kg / (m * s 2) or N / m 2)
pascal	Pa	1 N / m 2
hectopascal	GPa	10 2 Pa
kilopascal	Kpa	10 3 Pa
bar	bar	10 5 N / m 2
physical atmosphere	atm	1.013 * 10 5 N / m 2
millimeter of mercury	mm Hg	1.333 * 10 2 N / m 2
kilogram-force per cubic centimeter	kgf / cm 3	9.807 * 10 4 N / m 2
poundal per square foot	pdl / ft 2	1.4882 N / m 2
pound-force per square foot	lbf / ft 2	47.8803 N / m 2
pound-force per square inch	lbf / in 2	6894.76 N / m 2
foot of water column	ft H 2 O	2989.07 N / m 2
inch of water	in H 2 O	249.089 N / m 2
inch of mercury	in Hg	3386.39 N / m 2
Work, energy, heat (J or kg * m 2 / s 2 or N * m)
joule	J	1 kg * m 2 / s 2 = 1 N * m
calorie	cal	4.187 J
kilocalorie	Kcal	4187 J
kilowatt hour	kwh	3.6 * 10 6 J
British thermal unit	Btu	1055.06 J
foot poundal	ft * pdl	0.0421 J
foot lbf	ft * lbf	1.3558 J
liter-atmosphere	l * atm	101.328 J
Power, W)
foot poundal per second	ft * pdl / s	0.0421W
foot-pound-force per second	ft * lbf / s	1.3558 Watt
horsepower (English)	hp	745.7 Watt
British thermal unit per hour	Btu / h	0.2931 Watt
kilogram-force-meter per second	kgf * m / s	9.807 Watt
Mass flow (kg / s)
pound-mass per second	lbm / s	0.4536 kg / s
Thermal conductivity coefficient (W / (m * K))
British thermal unit per second-foot-degree Fahrenheit	Btu / (s * ft * degF)	6230.64 W / (m * K)
Heat transfer coefficient (W / (m 2 * K))
British thermal unit per second - square foot-degree Fahrenheit	Btu / (s * ft 2 * degF)	20441.7 W / (m 2 * K)
Thermal diffusivity, kinematic viscosity (m 2 / s)
Stokes	St (St)	10 -4 m 2 / s
centistokes	cSt (cSt)	10 -6 m 2 / s = 1mm 2 / s
square foot per second	ft 2 / s	0.0929 m 2 / s
Dynamic viscosity (Pa * s)
poise	P (P)	0.1 Pa * s
centipoise cP	(cp)	10 6 Pa * s
poundal second per square foot	pdt * s / ft 2	1.488 Pa * s
pound-force second per square foot	lbf * s / ft 2	47.88 Pa * s
Specific heat (J / (kg * K))
calorie per gram-degree Celsius	cal / (g * ° C)	4.1868 * 10 3 J / (kg * K)
British thermal unit per pound-degree Fahrenheit	Btu / (lb * degF)	4187 J / (kg * K)
Specific entropy (J / (kg * K))
British thermal unit per pound-degree Rankine	Btu / (lb * degR)	4187 J / (kg * K)
Heat flux density (W / m 2)
kilocalorie per square meter - hour	Kcal / (m 2 * h)	1.163 W / m 2
British thermal unit per square foot - hour	Btu / (ft 2 * h)	3.157 W / m 2
Moisture permeability of building structures
kilogram per hour per meter millimeter of water column	kg / (h * m * mm H 2 O)	28.3255 mg (s * m * Pa)
Volumetric permeability of building structures
cubic meter per hour per meter-millimeter of water column	m 3 / (h * m * mm H 2 O)	28.3255 * 10 -6 m 2 / (s * Pa)
The power of light
candela	cd	SI base unit
Illumination (lx)
luxury	lx	1 cd * sr / m2 (sr - steradian)
ph	ph (ph)	10 4 lx
Brightness (cd / m2)
stilb	st (st)	10 4 cd / m2
nit	nt (nt)	1 cd / m2

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