Saturated and unsaturated couples
Take a closed vessel with liquid, we will support the temperature constant. After some time, the thermodynamic equilibrium of the processes of evaporation and condensation processes will be established in such a vessel. That is, the amount of molecules that will leave the liquid will be equal to the number of molecules in the fluid returned.
Definition
A gaseous substance that is in equilibrium with its liquid is called a rich steam.
Definition
The unsaturated ferry is called steam, the pressure and the density of which is less than the pressure and the density of the saturated steam.
The pressure of saturated pair with increasing temperature is growing.
In the surrounding air, there is always any weight of water vapor. Air that contains water vapor is called wet. In the air of the atmosphere, the intensity of water evaporation depends on how different water vapor pressure differs from the pressure of saturated vapors at a given temperature.
Absolute and relative humidity
Using the concepts of absolute and relative humidity.
Definition
Absolute moisture is considered a mass of water vapor, which is in one air cubic meter.
Absolute humidity can be measured by partial pressure of water vapor (P) at some temperature (t). Regarding partial pressure is performed by the Lalton law, which indicates that the individual components of the mixture of gases are considered independent. Therefore, each component creates pressure:
and the full pressure is equal to the amount of pressure components:
where $ p_i $ is partial pressure I gas components. Equation (2) is the Law of Dalton.
Using what humidity is the amount of water vapor in the air (gas), the concept of partial pressure and the LTLA law can be very useful in the practical consideration of the issues of absolute humidity.
Also, the absolute moisture is called the density of water vapor ($ \\ rho $) at the same temperature (t). With an increase in the absolute moisture, the water pair is closer to the state of a saturated steam. The maximum absolute humidity at a given temperature is the mass of a saturated water vapor in one cubic meter of air.
Definition
The relative humidity of the air is called the ratio of absolute humidity to the maximum absolute humidity at a given temperature.
It is expressed as a percentage:
\\ [\\ Beta \u003d \\ FRAC (\\ RHO) ((\\ RHO) _ (NP)) \\ CDOT 100 \\% \u003d \\ FRAC (P) (P_ (NP)) \\ CDOT 100 \\% \\ \\ Left (1 \\ Right ), \\]
where $ (\\ rho) _ (NP) is $ saturated pair density with a certain T, $ p_ (NP) $ - the saturated pair pressure at the same temperature. When establishing a thermodynamic equilibrium of evaporation and condensation processes relative humidity 100 \\%. This means that the amount of water in the air does not change.
With isochorine cooling or isothermal compression, unsaturated steam can be turned into a rich. The temperature ($ T_R $), in which the pairs becomes saturated, called the dew point. $ T_R $ is the temperature of the thermodynamic equilibrium of steam and fluid in the air (gas). With $ (t
Air humidity is measured by special devices - hygrometers, psychrometers. Optimal for a person at a temperature of about 20 degrees Celsius is considered relative humidity from 40% to 60%. To solve practical tasks, reference tables often use reference tables and the saturated water vapor density at different temperatures.
Example 1.
Task: Determine the pressure of a saturated pair at a temperature of $ T $ pressure in one atmosphere, if the mass of wet air with a relative humidity of $ \\ beta $ in a volume of $ v $ is $ M $ under the same conditions.
As the basis of the decision, we will take the Act of Dalton, which for a mixture of gases, and we have a mixture of dry air and water vapor, will be recorded as:
where $ p_v $ is the pressure of dry air, $ p_ (H_2O) $ - water vapor pressure.
In this case, the mass of the mixture is equal to:
where $ M_V- \\ $ Mass of dry air, $ M_ (H_2O) $ - weight of water vapor.
We use the Mendeleev equation - Kilperon, write it to the component - dry air in the form:
where $ (\\ Mu) _v $ is a molar mass of air, $ t $ - air temperature, $ V $ - air volume.
For water vapor, adopting it for the perfect gas, installing the status equation:
where $ (\\ Mu) _ (H_2O) $ is a molar mass of steam, $ t $ - steam temperature, $ V $ - steam volume.
Relative humidity is:
\\ [\\ Beta \u003d \\ FRAC (P_ (H_2O)) (P_ (NP)) \\ CDOT 100 \\% \\ \\ left (1.5 \\ RIGHT), \\]
where $ p_ (NP) $ is a saturated steam pressure. From (1.5) Express the pressure of saturated steam, we get:
Express from (1.2) a mass of dry air, we get:
From (1.1) Express the pressure of dry air, we have:
Substitute (1.7) and (1.8) in (1.3), we get:
\\ [\\ left (P-P_ (H_2O) \\ RIGHT) V \u003d \\ FRAC (\\ Left (M-M-M-M-((H_2O) \\ RIGHT)) ((\\ MU) _V) RT \\ \\ left (1.9 \\ RIGHT). \\ Express the mass of steam from (1.4), we get:
\\ [(M _ (\\)) _ (H_2O) \u003d \\ FRAC (V \\ Cdot P_ (H_2O) (\\ CDOT \\ MU) _ (H_2O)) (RT) \\ \\ Left (1.10 \\ Right). \\]
Express the pressure of steam ($ P_ (H_2O) $) using expressions (1.9) and (1.10), we obtain:
\\ [\\ left (p-p_ (h_2o) \\ right) v \u003d \\ FRAC (\\ left (m- \\ FRAC (V \\ Cdot P_ (H_2O) (\\ CDOT \\ MU) _ (H_2O)) (RT) \\ Right )) ((\\ mU) _v) rt \\ \\ to pv (\\ mu) _v-p_ (h_2o) v (\\ mu) _v \u003d MRT-V \\ CDOT P_ (H_2O) (\\ CDOT \\ MU) _ (H_2O) \\ TO V \\ CDOT P_ (H_2O) (\\ CDOT \\ MU) _ (H_2O) -P_ (H_2O) V (\\ MU) _V \u003d MRT-PV (\\ MU) _V \\ to P_ (H_2O) \u003d \\ FRAC (MRT -PV (\\ MU) _V) (V (\\ Cdot \\ Mu) _ (H_2O) -v (\\ MU) _V) \\ \\ left (1.11 \\ Right). \\]
We use (1.6), we obtain a saturated pair pressure:
Answer: The saturated pair pressure under the given conditions is equal to: $ P_ (NP) \u003d \\ FRAC (100) (\\ Beta) \\ CDOT \\ FRAC (MRT-PV (\\ MU) _V) (V (\\ CDOT \\ MU) _ (H_2O ) -V (\\ mu) _v) $.
Example 2.
Task: At a temperature of $ T_1 \\ $, the air humidity is $ (\\ beta) _1 $. How will the humidity of the air change, if the temperature of it has become $ t_2 $ ($ T_2\u003e T_1)? The volume of the vessel in which there was a gas to reduce in $ n $ times.
The task needs to find a change (difference) $ (\\ beta) _2 (- \\ beta) _ (1, \\) $ relative humidity in finite and initial states:
\\ [(\\ triangle \\ beta \u003d \\ beta) _2 (- \\ beta) _1 \u003d (\\ beta) _ (1 \\) \\ left (\\ FRAC ((\\ Beta) _2) ((\\ beta) _ (1 \\) ) -1 \\ RIGHT) (2.1) \\]
Using the definition of relative humidity Write:
\\ [(\\ Beta) _ (1 \\) \u003d \\ FRAC (P_1) (P_ (NP1)) 100 \\%, \\] \\ [(\\ beta) _ (2 \\) \u003d \\ FRAC (P_2) (P_ (NP2 )) 100 \\% \\ \\ left (2.2 \\ right), \\]
Where $ P_ (NP) $ is a saturated pair pressure in the corresponding states, $ p_1 $ is the water vapor pressure in the initial state, $ p_2 $ is the vapor pressure in the final state.
substitute (2.2) in (2.1) we get:
\\ [\\ triangle \\ beta \u003d (\\ beta) _ (1 \\) \\ left (\\ FRAC (\\ FRAC (P_2) (P_ (NP2)) (\\ FRAC (P_1) (P_ (NP1))) - 1 \\
Since, by the condition of the problem, we know the temperature of the system states, then the pressure of the saturated pair ($ P_ (NP1) $ and $ p_ (NP2) $) can be considered known in this case, as it can always take them from the corresponding reference tables.
To find the pressures of $ p_1 $ and $ p_2 $ we use the Mendeleev equation - Klaperon, take into account that the amount of substance in the processes that occur in the system does not change, then we write:
\\ [\\ FRAC (p_2v_2) (p_1v_1) \u003d \\ FRAC (T_2) (T_1) \\ Left (2.4 \\ RIGHT). \\]
From the conditions of the problem it is known that the volume has decreased in $ n $ times, that is:
\\ [\\ FRAC (V_2) (v_1) \u003d \\ FRAC (1) (N). \\]
Consequently, expression (2.4) will be recorded as:
\\ [\\ FRAC (P_2) (P_1N) \u003d \\ FRAC (T_2) (T_1) \\ To \\ FRAC (P_2) (P_1) \u003d N \\ FRAC (T_2) (T_1) \\ Left (2.5 \\ RIGHT). \\]
Substitute (2.5) in (2.3), we get:
\\ [\\ triangle \\ beta \u003d (\\ beta) _ (1 \\) \\ left (N \\ FRAC (T_2) (T_1) \\ FRAC (P_ (NP1)) (P_ (NP2)) - 1 \\ RIGHT). \\]
Answer: For given processes, the relative humidity will change to $ \\ triangle \\ beta \u003d (\\ beta) _ (1 \\) \\ left (N \\ FRAC (T_2) (T_1) \\ FRAC (P_ (NP1)) (P_ (NP2 )) - 1 \\ RIGHT) $
Teacher Physics Kokovina L.V.
Rybinsky municipal area
Air humidity. Preparation for the exam.
Part A.
The relative humidity of the air is 50%. Correct the indications of wet (t 1) and dry (t 2) of the thermometer of the psychrometer.
A) .t1 \u003d T2; B). T1\u003e T2 c) T1
2. Use the absolute and relative air humidity at a temperature of16 0 C if the dew point is 10 0 C. The calculation of the saturable vapor of water at the specified temperatures is equal, respectively: 1,81kpa and 1,22kpa.
A) .1,22kpa, 67% b) .1,81kpa, 67% c). 1,22kpa, 33% g) .1,81kpa, 33%
3. The room has two hermetic air vessels. In the first of these, the relative humidity is 40%, in the second 60%. Compare the pressure of water vapor in these vessels. The air is the same in both vessels.
A) .r1 \u003d p2 b) p1\u003e p2 c) p1
4. The pressure of water vapor in the atmosphere at 15 0 Czoded 1,5ppa. Will the dew fall out if the air temperature dropped to 10 0 s at night? The pressure of saturated vapors at 10 0 s is 1.22kpa.
A) falls b) will not fall in) the answer is ambiguous
5. In the class at a temperature of 25 0 s, high humidity is created. How will the humidity of the air in the room, if you open the window, and it's cold outside the window and rains?
A) rises b) drops c) not change d) answer is ambiguous
6. In a sealed vessel, there is a saturated par. How will the pressure of this pair change if the temperature is raised in 2 times?
A) will not change b) will increase by 2 times c) increase more than 2 times d) answer is ambiguous
IN 1. The wet thermometer of the psychrometer shows 10 0 s, and dry 14 0 S.Nighti relative humidity and partial pressure of water vapor. It is above the use of a reference book in physics.
C1. In one vessel, the volume of 10 l is air with a relative humidity of 40%, and in another vessel, the volume of 30l-air at the same temperature, but with a relative humidity of 60%. The vessels are connected by a thin tube with a crane. What is the relative humidity (in percent) will be established after the opening of the crane?
275. Specify the correct statements.
In the transition of a substance from a gaseous state into liquid at a constant temperature
276. At the same temperature, saturated water vapor in the closed vessel differs from an unsaturated pair.
277. In the vessel under the piston is unsaturated steam. It can be made saturated
278. The dew point for water vapor in the room is equal to 6 ° C. In the room made a dry bottle with water from the balcony, and soon she was covered with small droplets of water. It follows that
279. On Saturday the air temperature was higher than on Sunday. The partial pressure of water vapor in the atmosphere these days remained constant. In which days the relative humidity of the air was more? Note that the saturated steam pressure increases with increasing temperature.
280. Choose the right statements.
| BUT. | The dew point is called the temperature at which the relative humidity becomes 100%. | |||||||
| B. | The pressure of the saturated pair at a constant temperature does not depend on the volume held. | |||||||
| IN. | Saturated is called steam, located in dynamic equilibrium with its liquid. | |||||||
| 1) | A and B. | 2) | B and B. | 3) | A and B. | 4) | A B C | |
281. The partial pressure of water vapor in air at 20 ° C is 0.466 kPa, the pressure of saturated water vapor at this temperature is 2.33 kPa. Relative air humidity is equal
283. The relative humidity in the room is 40%. What is the ratio of partial pressure P of water vapor in the room and the pressure of the rich water vapor at the same temperature?
284. At the same temperature of 100 ° C, the pressure of saturated vapor of water is 10 5 Pa, ammonia - 59 × 10 5 Pa and mercury - 37 Pa. In which of the answer options, these substances are located in descending order of their boiling temperature in an open vessel?
285. The photograph shows two thermometers used to determine the relative humidity of air using a psychometric table in which the humidity is indicated as a percentage.
Psychricheetric table
| t dry term | Differences of dry and wet thermometers | ||||||||
| ° S. | 7 | ||||||||
The relative humidity in the room in which the shooting was taken, is equal
The article discusses in detail such a thing as air humidity in the apartment: the norm of this indicator for the residential premises of various purposes, prescribed by GOST, the consequences for the person arising from the norm from the norm in one or the other side. The text describes alternative methods for measuring moisture levels and, designed for this, as well as recommendations for maintaining optimal climatic conditions.
Air humidity in the apartment: norm Water content for comfortable living conditions
The optimal level of air humidity is one of the components that provide comfortable climatic conditions for human accommodation. Moreover, for each of the premises, depending on its purpose, its microclimate is provided. Most often, people care about the temperature and quality of air masses in the house, forgetting about this indicator. But it is precisely the number of water molecules (steam) in the composition of the air affects the perception of the temperature of the human body, the preservation of the decor in the room and the state of the plants.
Note! The generally accepted average indicator of normal air humidity in the apartment should be at the level of 45%. It may vary depending on the type of room and its operational conditions.
Deviation from the norm is possible both in the winter season and in the warm period. In both cases, the lack or abrasion of humidity entails the deterioration of the health of people, the state of the plants and the damage of furniture, finishes, etc.
What should be the humidity in the apartment (averaged indicators for the main premises):
| Type of room | Humidity level,% |
| Dining room | 40-60 |
| Bathroom, kitchen | 40-60 |
| Library and work area | 30-40 |
| Bedroom | 40-50 |
| Children's | 45-60 |
Such rooms, like a kitchen, bathroom and bathroom will always have an elevated moisture level, so the standard for these rooms is higher than for other premises.
What consequences should deviate from moisture norms in the apartment: Pesked air
When the batteries turn on, the air in the premises becomes overwhelmed. As a result, the residents annoyed the mucous membrane of the throat and the nasal cavity. There is a drying of hair and skin. With violation of the moisture rate in the residential room, static electricity is formed, lifting dust particles into the air. This process can be the basis for the spread of microbes and dust ticks.
Excessive dryness of the room entails many negative consequences:
- reducing the elasticity of the skin, nails and hair - as a result of this, dermatitis, peeling, microcracks and premature wrinkles appear;
- drying the mucosa - redness appears, an unpleasant itching and a feeling of foreign bodies ("sand");
- blood thick - because of this, the circulation of blood flow slows down, the person appears weakness, headaches. There is a decrease in performance, the heart is exposed to increased loads and is exterminated faster;
- the viscosity of intestinal and gastric juice increases - the operation of the digestive system slows down significantly;
- dry respiratory tract - as a result of this, local immunity weakened, the likelihood of colds and infectious diseases increases;
- the quality of air is reduced - a large number of allergens are concentrated in the composition of the air masses, which, with the humidity rate of air indoors, are bound by water particles.
Note! From lack of moisture, plants and animals are affected by the apartment. The life of wooden furniture and finishes is reduced, they flexible, covered by cracks.
What consequences entails excess of the humidity rate in the room
The overaffect of water can also be dangerous for a person, so many people think about what air humidity is considered normal in the apartment and how to keep climatic conditions within this indicator. Increased water vapor content in the room becomes a beautiful medium for breeding fungi, mold and harmful bacteria.
In such conditions, many problems arise:
- The frequency and severity of respiratory diseases increases - diseases such as bronchitis, runny nose, allergies and asthma become chronic, difficult to treat.
- The microclimate in the rooms becomes unacceptable for life - people feel dampiness or stool in rooms.
- A feeling of freshness is lost - the release of breeding pathogenic organisms causes the appearance of unpleasant odors.
- Increases drying time of linen.
Increased air humidity rate in the apartment is also harmful to the situation. Plants begin to heat up, mold appears on the ceiling and walls, wooden surfaces are exposed to deformation changes. Books and other paper products change the structure.
What should be air humidity in the apartment: GOST standards
Air humidity may be relative and absolute. To create comfortable climatic conditions in the house, the optimal value is calculated. GOST 30494-95 is regulated by an indicator indicating which normal air humidity in the apartment should be.
Relative humidity is indicated in the percentage ratio in the form of two quantities:
- optimal indicator;
- permissible value.
The permissible value is a border that does not harm human health, but can negatively affect the overall health, mood and reduce performance.
Note! If in relation to bedrooms, children's rooms and other zones, where a person is located for a long time, there are certain rules, it is strictly adhered to normal humidity in the kitchen, bathroom, corridor and bathroom. These rooms are considered auxiliary.
The actual steam content of 1 m³ of air is taken as a unit of measurement of absolute humidity. For example, in one cubic meter of air may contain 13 g of water. In this case, the absolute humidity will be equal to 13 g / m³.
To get relative humidity, you will need to perform certain calculations. For this you need two indicators:
- the maximum possible water content of 1 m³ of air;
- the actual amount of water in 1 m³ of air.
The percentage of real data to the maximum possible indicator and will be relative humidity. For example, in 1 m³ of air at a temperature of 24 ° C, 21.8 g of fluid can be maximally. If there is actually 13 g of water in it, then the relative humidity will be 60%. For convenience, you can use a special table of absolute air humidity, where the auxiliary data is contained.
Indicators of air humidity rate indoors according to GOST
The indicator prescribed by GOST depends not only on the appointment of the premises, but also from the time of year. For a warm period, 30-60% is provided. At the same time, the indicator of the relative humidity of air in the room is 60 percent, and the maximum allowable will be 65%. For some regions, where in the summer months is accompanied by high humidity, the regulatory value may be increased to 75%.
For the cold season, the standards for relative humidity in the room are equal to 40-45%. In this case, the maximum allowable value is 60%.
The most popular manufacturers and the best models, comparative characteristics of the structures, their advantages and disadvantages.
Air humidity rate in the apartment for a child
The immunity of the child does not act as effectively with the negative impact of environmental factors, as an adult organism. Children overheat or move much faster, easily picked up the cold, suffer infectious diseases and are heavier tolerable.
For this reason, it is important to maintain the optimal air humidity in the apartment for a child, especially this concerns his room where it is necessary to create conditions for maintaining the immune forces of the baby.
In the children's room, in no case, the air should not be dry. Such an atmosphere provokes intense moisture loss by the kid by the body. The drying of the mucous nasopharynx leads to their inability to resist viruses and infections. The child may appear in the eyes and peeling on the skin. The child is considered the optimal humidity of the air in the apartment within 50-60%.
According to the opinion of Dr. Evgenia Komarovsky, the importance of normal air humidity in the apartment can be increased to 60% for a healthy baby and 70% for a child with an infectious disease. The higher the level of humidity, the less intensively the drying of the mucous membranes occurs.
Indicators of normal humidity in the apartment for the children's body in winter are the same as for the warm season. However, there is one nuance here: the maximum air temperature in the room should not exceed 24 ° C. If the room is hotter, then the humidity of 60% will make the tropics from it. In practice, in the heat, high humidity in the apartment is harder to transfer than in the cold season.
Important! Excess 24 ° C in the children's room can lead to overheating of the body of the kid. As a result, the drying of the mucous membranes and fluid loss will accelerate.
How to achieve optimal humidity in the apartment
The main factor that has the greatest impact on the humidity is the temperature. The warmer in the room, the more water is able to absorb air. However, when calculating relative humidity it is worth remembering that at high temperatures the volume of fluid in the same air will be less. This nuance can be beneficial to be used to maintain the norm of humidity, the air on the street in the winter is very fresh and the optimal parameters are ensured by venting.
Humidity is absorbed:
- appliances intended for heating;
- such objects of the interior like toys, upholstered furniture, carpets;
- air conditioners.
As a small source of moisture, plants and aquarium can be considered, containers filled with water, wet underwear, the current roof or pipes.
How to determine air humidity in the apartment no appliance
To determine how much the level of air humidity has been rejected in the house you can do without a special device and take advantage of:
- glasses of water;
- table of Assman;
- fir shishkoy.
To determine the relative humidity of the air using a glass of water, a filled container is necessary to cool in the refrigerator to 5 ° C. It will take about 3 hours so that the water and the vessel reached the specified temperature. After that, the glass is made away from the battery on the table. For 5 minutes, condensate is formed on the walls of the container.
Further results will depend on the behavior of this condensate:
- After a few minutes, the glass dried - the humidity rate is reduced.
- Condensate on the walls did not disappear - the room has a normal microclimate.
- According to the vessel, droplets flowed - in the air there is an overabundance of moisture.
A spruce bump can serve as a device for measurements. It should be put in a distance from heating devices and after a few hours check the condition of the scales. If the air is reheated, the bump will open, when the moisture is rebupping - the flakes are densely devour.
All these devices only indirectly indicate the presence of a problem. To accurately determine the microclimate in the room better buy air humidity sensor.
Helpful advice! Primary signs of dryness of air serve dry tips of plants. Also, the insufficient level of moisture can be determined by synthetic clothing, which in such conditions emits electrical charges.
Features of the use of temperature sensor and humidity
To measure humidity, you can use special devices called sensors or hygrometers. The device independently converts the data obtained and displays the result as percentage terms.
Many people are looking for a decision by wondering how to remove moisture in the apartment. To control the microclimate in the bathroom and in other rooms with an abrasiveness of moisture, exhaust fans are used. They impede the formation of condensate on the walls and on the floor.
For residential premises, it is recommended to acquire a moisturizer if there is a lack of moisture on an ongoing basis. It will also be necessary to further buy air humidity sensors for the fan and humidifier, if so, are not provided with the designs of the instruments themselves.
The basis of the operation of the hygrostat or the sensor is the principle of the thermostat. The device opens and closes the contacts, reacting to the amount of water vapor in the air. Thus, the operation of the fan or humidifier becomes automated. The device is turned on only when it has a need.
Humidity control in the apartment: how to reduce / increase the number of steam in the air
To monitor the number of steam in the air, various methods are used, including remedies. Their aggregate allows you to achieve a certain result.
How to get rid of moisture in the apartment:
- To ventilate the room on a regular basis.
- Install exhaust type fans where they are needed.
- Purchase a climate system or.
- Timely making repairs in the house (maintenance of plumbing and water supply).
- Use heating appliances and air conditioners.
- Refuse drying linen indoors.
- Install a powerful hood in the kitchen.
Helpful advice! So that hygrometer indicators are reliable, it is recommended to establish this device in the depths of the room to eliminate the effect of drafts and other facts. ors.
How to increase air humidity in the room:
- Buy a table fountain or aquarium (if none of the household has asthma).
- Minimize the use of air conditioner and heating devices.
- Swim wet towels on radiators.
- From time to time splash the water with a spray with a spray with a spray, thereby saturating the air moisture.
- Regularly make wet cleaning in the house.
- Plant as much as possible room plants.
There are many devices that will achieve this or that result depending on the needs. They are selected taking into account the microclimate in the house. Before buying them, it is recommended to accurately set the parameters of humidity. For this purpose, measurements are made for several days.
Perfectly fit into the interior
Maintain optimal humidity in the house using special instruments - humidifiers. This category of climatic equipment includes many modifications: traditional, steam, ultrasound instruments. The "washing" of air and climatic complexes are more complex variants of these devices equipped with a hygrometer, timer and other useful additions. In the fight against mold will help ultraviolet lamp.
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