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: evaporation, diagrams, boiling, cases 
It is known that all substances are solid depending on temperature and pressure, 
can be in liquid and gas state (phases). One of the substance 
transition from one state to another is called a phase change or phase transition 
is called For example, the transition of the liquid phase to the gas phase is the formation of steam; 
and the transition from the gas phase to the liquid phase is called condensation. 
Evaporation: Evaporation is when a substance changes from a liquid state to a vapor state 
is called In this case, some of the molecules are separated from the surface of the liquid 
comes out and creates steam on it. Released during evaporation 
molecules overcome the gravitational force of molecules remaining on the surface, 
that is, they work against these forces. Molecules do this 
heat movement, kinetic energy. Everyone knows 
molecules do not do this either. Kinetic energy is much 
only large molecules can do this. 
If the temperature of the liquid is kept constant, i.e. to it 
If it is continuously heated, it will fly away 
the number of molecules increases continuously. But vapor molecules 
as they change from liquid to vapor due to irregular motion 
at the same time, the reverse process - condensation is also formed. If 
if the evaporation takes place in a closed container, then the amount of steam 
until equilibrium is reached, i.e., the amount of liquid and vapor does not change 
will increase until it is. It is out of the liquid per unit time 

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the number of molecules returning to the liquid during this time 
is equal to the number 
A vapor in dynamic equilibrium with a liquid is a saturated vapor 
is called At equilibrium, the density of the vapor remains constant, which is the density 
corresponds to a certain pressure. This pressure is the elasticity of saturated steam 
is called 
Saturated vapor pressure increases with temperature. Temperature 
the higher, the more molecules of the liquid into the gas phase 
and the density of the steam at equilibrium, and consequently, the pressure 
will be so big. Touching the liquid and above it 
The steam that saturates the space is called saturated wet steam. 
Saturated wet mist1 is very fine water droplets with mist1 
is a mixture. The amount of liquid particles in the vapor is the dryness of the vapor 
or determines the level of humidity 
If the liquid is heated at constant pressure, its molecules 
the speed of movement over the entire volume increases and the formation of steam 
increases. It strictly corresponds to the pressure at which steam is generated 
at a certain temperature, the evaporation process turns into a boiling process. 
Boil. Not only the free surface of the liquid, but the entire volume 
intensively vaporization and rapid vapor bubbles 
formation and increase is called boiling. 
The temperature and pressure at which boiling occurs are related. They are 
The saturation temperature is called tm and the saturation pressure is called pm. 
The temperature and pressure are equal to the saturation pressure and temperature, but in the 
composition 
Steam with water particles is called dry saturated steam. 
Vapor density of saturated steam. Wet during steam generation 
The amount of dry steam varies from 0 to 1, as does the amount of steam 
I'm sorry. 
If 1 kg of steam contains X kg of dry steam and (1-L) kg of moisture, then X - 
The quantity is called vapor density or vapor dryness level, that is 
size is the amount of dry steam in wet steam. 
(1-L) — the quantity is called moisture content or humidity level of steam. 
For example, if ^ = 0.85, then (1-L)=(1-0.85)=0.15, i.e. saturated 
wet steam contains 85% dry steam and 15% water. 
0 hot steam. If saturated dry steam at constant pressure 
when heat is applied, its temperature rises, its volume increases and it becomes saturated and dry 
steam becomes superheated steam. Superheat of steam, At 
determined from the temperature difference: 
At = t — tm 
t is the temperature of superheated steam; 
tm is the temperature of saturated dry steam 
18. Steam turbine unit.