Final control questions on the subject “heat engineering” The purpose and function of the subject. Working parameter. Status parameters. Base words and phrases

 
Base words and phrases: definition, equation, humidity, absolute and relative humidity, 
density, gas constant, axial pressure, wet storage, psychrometer, hd-diagram 
Atmospheric air contains a certain amount of water vapor. 
A mixture of dry air and water vapor is called moist air. 
Humid air is mainly in ventilation systems, air conditioning 
(air conditioning), cooling devices and drying of materials 
occurs in processes. 
Heat and electricity located far from water supply sources 
humid air in stations, technical water cooling processes 
properties are of great importance. 
Moist air is one of the special cases of a mixture of gases. Dalton 
According to the law, each gas in a mixture of gases is itself a mixture of gases 
at its temperature, it behaves as if it occupies the entire volume of the mixture, otherwise 
in other words, the partial pressures of gases in a gas mixture 
the sum is equal to the total pressure of this mixture. 
Partial pressure of dry air - with phavo, partial pressure of water vapor 
If we denote the pressure by pb and the pressure of the mixture by p, Dalton 
we write the law as follows: 
P = P air+Pb 
Usually, the pressure of moist air is equal to atmospheric pressure (V). 
for can be written as: 
V = Rhavo+ Rb 
The more water vapor in the air mixture, the more water vapor is in the mixture 
the higher the partial pressure of water vapor. In humid air 
the partial pressure of water vapor is the quantity ps, p is the value of moist air 
the saturation temperature cannot be higher than the pressure, i.e 
Ph^Ps 
if there is, moist air is not saturated, moist air with Pb < Ps is saturated moist 
called air. 
If we cool the unsaturated air at a constant pressure, it is so 
a temperature is formed at which steam1 begins to recondense. This temperature is humid 
is called the dew point temperature of the air (t^). If the air is dew 
If cooled to a temperature below the boiling point, the steam begins to condense 
and fog is formed, and the air becomes very saturated. Humid air 
The main thermodynamic characteristics include: absolute 
humidity, relative humidity, density, gas constant, moisture retention and enthalpy 

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Absolute humidity - m of water vapor in 1 m 3 of moist air with specific movement 
is a quantity equal to its mass (kg/m 3 or g/m 3). 
It is convenient to describe moist air and heat-technical calculations 
for the purpose of simplification, the concept of relative humidity is used. 
Relative humidity is the partial pressure of water vapor in moist air 
the ratio of steam to the saturation pressure at this temperature is called: 
or 
Relative humidity (f) is expressed as a percentage. Since 0
0 < 
𝜑 < 100 %. 
If j = 0 — dry air; 
𝜑=1 or 𝜑 =100% — saturated air, f<1 
- refers to the saturated air. 
If water vapor in moist air is an ideal gas, it obeys the equation of state 
if it is considered, then 
As the moisture content of moist air, the vapor contained in moist air 
the ratio of its mass to the mass of dry air 
In 1918, the graphic method of moist air parameters was developed by Professor 
It is much easier to determine using the h-d diagram proposed by A.K.Ramzin 
is convenient. 
In this diagram, the ordinate axis is h, kJ/kg enthalpy, abscissa axis 
moisture content along — d, g/kg. dry air quantities are set. 
Coordinate axes are 135°C for convenient placement of different lines 
placed under Thus, the lines of moisture conservation d are vertical 
b is , and the enthalpy lines are h-slanted straight lines. 
The diagram has the following lines: 
1) constant enthalpy line (isoenthalpy) - (45° to the ordinate axis 
straight line at an angle) h = const. 
2) the moisture conservation line — d=const — is parallel to the abscissa axis. 
3) t = const is a straight line. 
4) 
𝜑 = const. 
5) Pp — line — to determine the partial pressure of water vapor in the air 
gives im mine 
20. Thermal conductivity.