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How much air does a person need for normal existence?
Ventilation of premises ensures timely removal of excess carbon dioxide, heat, moisture, dust, harmful substances, in general, the results of various household processes and the presence of people in the premises.
Types of ventilation.
1) Natural. Consists in natural air exchange between by
movement and external environment due to the difference in temperature between the internal and external
outside air, wind, etc.
Natural ventilation May be:
Disorganized (by filtering air through cracks)
Organized (through open vents, windows, etc.) - ventilation.
2) Artificial.
Supply air - artificial supply of outside air into the room.
Exhaust - artificial extraction of air from a room.
Supply and exhaust - artificial supply and exhaust. Air enters through supply chamber, where it is heated, filtered and removed through ventilation.
General principle ventilation is that
In dirty rooms, exhaust should predominate (to prevent the spontaneous entry of dirty air into adjacent rooms)
IN clean rooms inflow should prevail (so that air from dirty rooms does not enter them).
How to determine how much clean air should enter the room per hour per person to ensure sufficient ventilation?
The amount of air that needs to be supplied to a room per person per hour is called ventilation volume.
It can be determined by humidity, temperature, but most accurately determined by carbon dioxide.
Methodology:
The air contains 0.4%<■ углекислого газа. Как уже упоминалось, для помещений, требующих высокого уровня чистоты (палаты, операционные), допускается содержание углекислого газа в воздухе не более 0.7 /~ в обычных помещениях допускается концентрация до 1 Л«.
When people stay indoors, the amount of carbon dioxide increases. One person produces approximately 22.6 liters of carbon dioxide per hour. How much air must be supplied per person per hour in order to dilute these 22.6 liters so that the concentration of carbon dioxide in the air in the room does not exceed 0.7%° or 1/<.. ?
Each liter of air supplied to the room contains 0.4%° carbon dioxide, that is, each liter of this air contains 0.4 ml of carbon dioxide and thus can still “accept” 0.3 ml (0.7 - 0.4) for clean rooms (up to 0.7 ml per liter or 0.7 /~) and 0.6 ml (1 - 0.4) for ordinary rooms (up to 1 ml per liter or 1 /~).
Since every hour 1 person produces 22.6 liters (22600 ml) of carbon dioxide, and each liter of supplied air can “accept” the above number of ml of carbon dioxide, the number of liters of air that must be supplied to the room per 1 person per hour is
For clean rooms (wards, operating rooms) - 22600 / 0.3 = 75000 l = 75 m 3. That is, 75 m 3 of air per person per hour must enter the room so that the concentration of carbon dioxide in it does not exceed 0.7%*
For ordinary premises - 22600 / 0.6 = 37000 l = 37 m3. That is, 37 m of air per person per hour must enter the room so that the concentration of carbon dioxide in it does not exceed.
If there is more than one person in the room, then the indicated numbers are multiplied by the number of people.
It was explained in detail above how the value of the ventilation volume is found directly on specific numbers, but in general it is not difficult to guess that the general formula looks like this:
b = (K * M) / (P - P0 = (22.6 l * 14) / (P - 0.4%.)
b - ventilation volume (m)
K - the amount of carbon dioxide exhaled by a person per hour (l)
N - number of people in the room
P - maximum permissible carbon dioxide content in the room (/“)
Using this formula, we calculate the required volume of supplied air (required volume of ventilation). In order to calculate the real volume of air that is supplied to a room per hour (real volume of ventilation), you need to substitute the real concentration of carbon dioxide in a given room in ppm into the formula instead of P (maximum concentration of carbon dioxide - 1/C 0.7 U"):
^ real-
- (22.6 l * 14) / ([C0 2 ] fact - 0.4 /~)
b real - real volume of ventilation
[SSYfact - actual carbon dioxide content in the room
To determine the concentration of carbon dioxide, the Subbotin-Nagorsky method is used (based on reducing the titer of caustic Ba, the most accurate), the Rehberg method (also using caustic Ba, express method), Prokhorov’s method, photocolorimetric method, etc.
Another quantitative characteristic of ventilation, directly related to the volume of ventilation, is the ventilation rate. The ventilation rate shows how many times per hour the air in the room is completely exchanged.
Ventilation rate - The volume of what gets (extracted 4) into the chug. air dry I
Room volume.
Accordingly, in order to calculate the required ventilation rate for a given room, you need to substitute the required volume of ventilation in the numerator of this formula. And in order to find out what the real ventilation rate in the room is, substitute the real volume of ventilation into the formula (see calculation above).
The ventilation ratio can be calculated by inflow (inflow ratio), then the volume of air supplied per hour is substituted into the formula and the value is indicated with a (+) sign, or it can be calculated by exhaust (exhaust ratio), then the volume of air extracted per hour is substituted into the formula and the value is indicated with a (-) sign.
For example, if in an operating room the ventilation ratio is designated as +10, -8, then this means that every hour ten times the volume of air relative to the volume of the room is supplied to this room and eight times is extracted.
There is such a thing as an air cube.
An air cube is the volume of air required for one person.
The air cube norm is 25-27 m. But as was calculated above, for one person per hour it is required to supply an air volume of 37 m, that is, for a given air cube norm (given room volume), the required air exchange rate is 1.5 (37 m / 25 m = 1.5).
Microclimate of hospital premises.
Temperature regime.
Temperature changes should not exceed:
In the direction from the inner to the outer wall - 2°C
In the vertical direction - 2.5°C per meter of height
During the day with central heating - 3°C
Relative air humidity should be 30-60%
Air speed - 0.2-0.4 m/s
6. The problem of nosocomial infections; nonspecific prevention measures, purpose and content.
NOMACHICAL INFECTIONS - any clinically recognizable disease caused by microorganisms that occurs in patients as a result of staying in a medical institution or seeking medical help, as well as in medical personnel as a result of their professional activities (World Health Organization).
Nonspecific prevention.
Architectural and planning activities
· Construction and reconstruction of inpatient and outpatient clinics in compliance with the principle of rational architectural and planning solutions:
· insulation of sections, wards, operating units, etc.;
· compliance and separation of flows of patients, personnel, “clean” and “dirty” flows;
· rational placement of departments on floors;
· correct zoning of the territory
Sanitary measures
· effective artificial and natural ventilation;
· creation of regulatory conditions for water supply and sanitation;
· correct air supply;
· air conditioning, use of laminar flow units;
· creation of regulated parameters of microclimate, lighting, noise conditions;
· compliance with the rules for the accumulation, neutralization and disposal of waste from medical institutions.
Sanitary and anti-epidemic measures
· epidemiological surveillance of nosocomial infections, including analysis of the incidence of nosocomial infections;
· control over the sanitary and anti-epidemic regime in medical institutions;
· introduction of a hospital epidemiologist service;
· laboratory monitoring of the state of the anti-epidemic regime in health care facilities;
· identification of bacteria carriers among patients and personnel;
· compliance with the norms for the placement of patients;
· inspection and admission of personnel to work;
· rational use of antimicrobial drugs, primarily antibiotics;
· training and retraining of personnel on issues of regime in health care facilities and prevention of nosocomial infections;
· sanitary educational work among patients.
Disinfection and sterilization measures.
· use of chemical disinfectants;
· use of physical methods of disinfection;
· pre-sterilization cleaning of instruments and medical equipment;
ultraviolet bactericidal irradiation;
· chamber disinfection;
· steam, dry air, chemical, gas, radiation sterilization;
· carrying out disinsection and deratization.
Every room, including a hospital ward, is designed to create artificial microclimatic conditions that are more favorable than the natural climate existing in the area. The internal climate (microclimate) of premises has a great influence on the human body, determines his well-being, affects human health, sometimes causing pathological conditions or exacerbation of existing diseases. Microclimate is usually understood as the thermal state of the air in a room, which determines the effect of the human body’s sensation of heat and is made up of the combined effect of the temperature of the air and surrounding surfaces, humidity and air movement.
From a hygienic point of view it is important:
1) so that each of these components does not go beyond physiologically acceptable limits;
2) so that throughout the day, at different points in the room, the microclimate remains smooth and constant, and does not give sharp fluctuations that disrupt a person’s normal sense of heat and adversely affect his health;
3) so that the difference in temperature horizontally at the outer and inner walls of the room does not exceed 2°C, and vertically at a height of 1.5 m and at the floor - 2.5°C in order to prevent a violation of thermal equilibrium and one-sided cooling;
4) so that the difference between the air temperature of the premises and the temperature of the cooled surfaces (external walls) is not more than 5 ° C in order to avoid negative radiation, which contributes to disruption of heat exchange in the body, one-sided cooling of the body, the appearance of a feeling of chilliness, deterioration of the sense of heat and the development of colds;
5) so that the humidity of the room does not exceed 40-60%, otherwise this will contribute to disruption of heat exchange in the body (skin temperature increases and moisture transfer of the skin decreases) and the appearance of dampness in the room;
6) so that the air speed is in the range of 0.1-0.15 m/s, because sedentary air leads to difficulty in heat transfer and, conversely, moving air promotes cooling of the body and is a useful tactile stimulus that stimulates skin-vascular reflexes that improve thermoregulation.
Indicators for assessing the complex influence of microclimate meteorological factors on the body are the cooling capacity of the air and the equivalent effective temperature. Direct determination of the amount of heat loss by the body depending on temperature and air speed is extremely difficult, therefore an indirect method is used to determine the cooling capacity of the air using a ball catathermometer or a Hill catathermometer. In view of the fact that this physical device will not be able to reproduce the conditions of heat loss from the skin surface, which depend not only on the cooling ability of the air, but also on the work of thermoregulatory centers, the catathermometry method has a convention and indicates that optimal thermal well-being in so-called sedentary persons professions with ordinary clothes is observed when the cooling value of the catathermometer is 5-7 Mcal/cm 2, with higher readings a person will feel cold, and with lower readings - stuffiness.
Determining effective temperatures allows us to indirectly determine the total effect of temperature, humidity and air movement on the body. The assessment of weather conditions is carried out based on a comparison of certain combinations of temperature, humidity and air movement with a person’s subjective thermal sensations.
The microclimate of the premises can be comfortable, when the physiological mechanisms of thermoregulation of the human body are not stressed, and uncomfortable, in which there is tension in the thermoregulation processes and poor sensation of heat. An uncomfortable microclimate, in turn, can be overheating (acute and chronic hyperthermia) and cooling (acute and chronic hypothermia). Considering that microclimatic factors influence a person together, the physiological effect of air temperature is most closely related to humidity and air speed. The same temperature is felt differently depending on the degree of humidity and air movement. So, if the ambient temperature is higher than body temperature and the air is saturated with water vapor, then the movement of air does not produce a cooling effect, but causes an increase in body temperature. In the case of low relative humidity, the cooling effect of moving air, despite the high temperature, is maintained, because At the same time, the possibility of heat transfer by evaporation remains.
At high temperature and humidity and low speed of air movement, a state of overheating of the body occurs, which can manifest itself in the form of acute hyperthermia, heat stroke or convulsive disease. At low air temperatures, high humidity and speed of movement, hypothermia develops: local (frostbite) or general.
Changes in weather conditions can cause the development of meteopathic reactions. These reactions can occur in both sick and healthy people; in the former, they are more often manifested by exacerbation of chronic diseases, in the latter, by deterioration of well-being and decreased performance. The largest number of diseases and their exacerbations are associated with sudden changes in weather during the passage of synoptic fronts. At the time of the passage of this front, all meteorological conditions change sharply. The most significant changes in temperature, air speed and atmospheric pressure. Moreover, it is not the absolute values of these factors that play a significant role, but the fluctuations between the previous and subsequent days. In this regard, the following types of weather according to Fedorov are distinguished:
1.Optimal
Dt no more than 2°С
DP no more than 4 mbar
DV no more than 3 m/s
2. Annoying
Dt not > 4°С
DP not > 8 mbar
DV not > 9 m/s
Dt more than 4°С
DP > 8 mbar
Meteotropic reactions that occur when the weather changes differ from an exacerbation of the underlying disease caused by other reasons and have the following symptoms:
A) occur simultaneously and en masse in patients with the same type of diseases under unfavorable weather conditions;
B) short-term deterioration in condition simultaneously with worsening weather;
C) relative stereotypicality of repeated violations in the same patient under abnormal weather conditions.
According to the degree of severity, meteotropic reactions are divided into mild and severe.
Most often, meteotropic reactions occur in patients with hypertension, coronary artery disease, bronchial asthma, glaucoma, gastric and duodenal ulcers, kidney and cholelithiasis.
Microclimate- a complex of physical factors of the internal environment of premises that influence the body’s heat exchange and human health. Microclimatic indicators include temperature, humidity and air speed, temperature of the surfaces of enclosing structures, objects, equipment, as well as some of their derivatives (air temperature gradient vertically and horizontally in the room, intensity of thermal radiation from internal surfaces).
The influence of a complex of microclimatic factors affects a person’s sense of heat and determines the characteristics of the physiological reactions of the body. Temperature effects that go beyond neutral fluctuations cause changes in muscle tone, peripheral blood vessels, sweat gland activity, and heat production. At the same time, the constancy of the thermal balance is achieved due to a significant tension in thermoregulation, which negatively affects the well-being, performance of a person, and his state of health.
The thermal state in which the voltage of the thermoregulation system is negligible is defined as thermal comfort. It is provided in the range of optimal microclimatic conditions, within which the lowest thermoregulation stress and a comfortable feeling of heat are observed. Optimal microclimate standards have been developed, which should be ensured in medical and preventive and children's institutions, residential and administrative buildings, as well as at industrial facilities where optimal conditions are required according to technological requirements. Sanitary standards for optimal microclimate are differentiated for cold and warm periods of the year ( table 1 ).
Table 1
Optimal norms of temperature, relative humidity and air speed in residential, public and administrative premises
|
Indicators |
Period of the year |
|
|
cold and transitional |
||
|
Temperature |
||
|
Relative humidity, % |
||
|
Air speed, m/s |
No more than 0.25 |
No more than 0.1-0.15 |
For the premises of medical institutions, the design air temperature is standardized, while for premises for various purposes (wards, offices and treatment rooms), these standards are differentiated. For example, in wards for adult patients, rooms for mothers in children's departments, wards for tuberculosis patients, the air temperature should be 20°; in wards for burn patients, postpartum wards - 22°; in wards for premature, injured, infants and newborns - 25°.
In cases where, for a number of technical and other reasons, optimal microclimate standards cannot be ensured, they are guided by acceptable standards ( table 2 ).
table 2
Permissible standards for temperature, relative humidity and air speed in residential, public, administrative and service premises
|
Indicators |
Period of the year |
|
|
cold and transitional |
||
|
Temperature |
No more than 28° |
|
|
for areas with an estimated air temperature of 25° |
No more than 33° |
|
|
Relative humidity, % |
||
|
in areas with an estimated relative humidity of more than 75% |
||
|
Air speed, m/s |
No more than 0.5 |
No more than 0.2 |
Acceptable sanitary microclimate standards in residential and public buildings are ensured with the help of appropriate planning equipment, heat-protective and moisture-proof properties of enclosing structures.
When conducting routine sanitary inspection in residential, public, administrative and medical institutions, the air temperature is measured at 1.5 and 0.05 m from the floor in the center of the room and in the outer corner at a distance of 0.5 m from the walls; relative air humidity is determined in the center of the room at a height of 1.5 m from the floor; air speed is set at 1.5 and 0.05 m from the floor in the center of the room and at a distance of 1.0 m from the window; the temperature on the surface of enclosing structures and heating devices is measured at 2-3 points on the surface. When carrying out sanitary supervision in multi-storey buildings, measurements are carried out in rooms located on different floors, in end and row sections with one-sided and two-sided orientation of apartments at an outside air temperature close to the calculated one for given climatic conditions.
The air temperature gradient along the height of the room and horizontally should not exceed 2°. The temperature on the surface of the walls can be lower than the air temperature in the room by no more than 6°, the floor - by 2°, the difference between the air temperature and the window glass temperature in the cold season should not exceed an average of 10-12°, and the thermal effect on surface of the human body flux of infrared radiation from heated heating structures - 0.1 cal/cm 2 × min.
Industrial microclimate . The microclimate of industrial premises is significantly influenced by the technological process; the microclimate of workplaces located in open areas is significantly influenced by the climate and weather of the area.
In a number of industries, the list of which is established by industry documents agreed with state sanitary inspection bodies, optimal production microclimate. In cabins, at consoles and control stations for technological processes, in computer rooms, as well as in other rooms in which operator-type work is performed, optimal microclimate values must be ensured: air temperature 22-24°, humidity - 40-60%, speed air movement - no more than 0.1 m/s regardless of the period of the year. Optimal standards are achieved mainly through the use of air conditioning systems. However, the technological requirements of some industries (spinning and weaving shops of textile factories, individual shops of the food industry), as well as technical reasons and economic opportunities of a number of industries (open-hearth, blast furnace, foundry, forging shops of the metallurgical industry, heavy engineering enterprises, glass production and food industry ) do not allow for optimal production microclimate standards. In these cases, at permanent and non-permanent workplaces, in accordance with GOST, permissible microclimate standards are established.
Depending on the nature of the heat supply and the prevalence of a particular microclimate indicator, workshops are distinguished mainly with convection (for example, food shops of sugar factories, machine rooms of power plants, thermal shops, deep mines) or radiation heating (for example, metallurgical, glass production) microclimate. Convection heating microclimate is characterized by high air temperature, sometimes combined with high humidity (dying departments of textile factories, greenhouses, sintering shops), increasing the degree of overheating of the human body (see. Overheating of the body). Radiation heating microclimate is characterized by a predominance of radiant heat.
If preventive measures are not observed, people who work for a long time in a heating microclimate may experience dystrophic changes in the myocardium, arterial hypertension, hypotension, asthenic syndrome, the immunological reactivity of the body decreases, which contributes to an increase in the incidence of acute respiratory diseases, sore throat, bronchitis, myositis, and neuralgia among workers. When the body overheats, the adverse effects of chemicals, dust, noise intensify, and fatigue sets in faster.
Table 3
Optimal values of temperature and air velocity in the production work area of other premises, depending on the category of work and periods of the year
|
Energy consumption, W |
Periods of the year |
||||
|
cold |
cold |
||||
|
Temperature (°C) |
Air speed, ( m/s) |
||||
|
light, Ia |
|||||
|
light, Ib |
|||||
|
moderate severity, IIa |
|||||
|
moderate severity, IIb |
|||||
|
heavy, III |
|||||
The cooling microclimate in industrial premises can be predominantly convective (low air temperature, for example, in certain preparatory workshops of the food industry), predominantly radiation (low temperature of enclosures in refrigeration chambers) and mixed. Cooling contributes to the occurrence of respiratory diseases and exacerbation of diseases of the cardiovascular system. When cold, coordination of movements and the ability to perform precise operations deteriorate, which leads to both a decrease in performance and an increase in the likelihood of work-related injuries. When working in an open area in winter, it becomes possible frostbite, it becomes difficult to use personal protective equipment (respirators freeze when breathing).
Sanitary standards provide for ensuring optimal or acceptable parameters of the microclimate of industrial premises, taking into account 5 categories of work, characterized by different levels of energy consumption ( table 3 ). The standards regulate temperature, humidity, air speed and intensity of thermal radiation of workers (taking into account the area of the irradiated body surface), the temperature of internal surfaces enclosing the working area of structures (walls, floors, ceilings) or devices (for example, screens), the temperature of external surfaces of technological equipment, differences in air temperature along the height and horizontal of the working area, its changes during the shift, and also provide for the necessary measures to protect workplaces from radiation cooling. emanating from the glass surface of window openings (during the cold season) and heating from direct sunlight (during the warm period).
Prevention of overheating of workers in a heating microclimate is carried out by reducing the external heat load by automating technological processes, remote control, using collective and individual protective equipment (heat-absorbing and heat-reflecting screens, air showers, water curtains, radiation cooling systems), regulating the time of continuous stay at work place and in a recreation area with optimal microclimatic conditions, organization of drinking regime.
To prevent overheating of workers in open areas in the summer, work clothes made of air- and moisture-permeable fabrics and materials with high reflective properties are used, and rest is organized in sanitary premises with an optimal microclimate, which can be ensured by using air conditioners or radiation cooling systems. Measures aimed at increasing the body’s resistance to thermal effects, including adaptation to this factor, are important.
When working in a cooling microclimate, preventive measures primarily involve the use of protective clothing (see. Cloth), shoes (see Shoes), hats and mittens, the heat-protective properties of which must correspond to meteorological conditions and the severity of the work performed. The time of continuous exposure to the cold and rest breaks in sanitary facilities, which are included in working hours, are regulated. These rooms are additionally equipped with devices for heating hands and feet, as well as devices for drying work clothes, shoes, and mittens. To prevent freezing of respirators, devices are used to heat the inhaled air.
Bibliography: Hygienic regulation of factors of the production environment and the labor process, ed. N.F. Measured and A.A. . Kasparova, p. 71, M., 1986; Provincial Yu . D. and Korenevskaya E.I. Hygienic principles of microclimate conditioning in residential and public buildings, M., 1978, bibliogr.; Guide to occupational health, ed. N.F. Izmerova, vol. 1, p. 91, M., 1987, Shakhbazyan G.X. and Shleifman F.M. Hygiene of industrial microclimate, Kyiv, 1977, bibliogr.
According to the standards, the premises of hospital wards must receive a sanitary norm of supply outside air all year round in a specific amount of 80 m 3 / (h-person) with a specific filling rate of the hospital ward of 5 m 2 / person. Let us assume that the hospital ward measures 5 m in width and 6 m in depth. Floor area of the room F floor = 5 x 6 = 30 m2. The ward has beds to accommodate patients in the number L = 30/5 = 6 people. The room must be provided with an influx of outside air in the amount of l day = 6 x 80 = 480 m 3 /h.
The hospital is located in Moscow, the estimated outside air temperature during the cold season is t nx = -28 °C with a heating period duration of 214 days, the average outside air temperature during the heating period is t n.av.ot = -3.1 °C.
In the hospital ward all year round it is necessary to maintain air parameters at the level of thermal comfort for a person, which are standardized by temperature and air humidity in the human habitation area t in [°C], the air temperature in the cold season should be t in = 20-22 ° C, and in summer t = 23-25 °C. Relative air humidity in the human habitation area can vary from φin = 30% in winter to φin = 60% in summer.
For gas pollution, the determining factor affecting human health is the content of carbon dioxide in the air in the area where people live, which should exceed the concentration of carbon dioxide in the outside air by no more than:
C. gas = C. gas + 1250 mg/m3.
In the outdoor air of large cities, Сn.gas = 1000 mg/m2.
To maintain the required normalized air parameters in the habitable area of hospital wards in the area where people are located in terms of temperature, relative humidity, cleanliness and gas pollution, it is necessary to use mechanical supply and exhaust ventilation.
At rest, one adult male at tin = 20 °C emits: sensible heat 90 W/(h-person); water vapor 40 g/(h-person). For the ward under consideration with an area of 30 m2, the number of discharges from patients will be:
q tl.out = 6 x 90 = 540 W/h;
w steam = 6 x 40 = 240 g/h.
Sensible heat released from people enters the room at human body temperature, which at normal thermal comfort is t person = 36.6 °C. This temperature is higher than the temperature of the air surrounding a person, and therefore sensible heat rises by convective flow to the ceiling of the room.
In most hospital room ventilation system designs, supply air from central air supply units is supplied to the upper zone of the room. This scheme for organizing air exchange is called “mixed ventilation”
Likewise, water vapor emitted from a person has a temperature of at least 36.6 °C, and it is lighter than the water vapor contained in the air around a person, and therefore rises to the ceiling. When a person exhales, carbon dioxide enters the surrounding air, which also rises by convective currents to the ceiling of the room.
Unfortunately, in most hospital room ventilation system designs, supply air from central air supply units is supplied to the upper zone of the room. This leads to the fact that, descending into the living zone, the supply air mixes with convective flows of harmful substances and returns some of these harmful substances to the human habitation zone. This scheme for organizing air exchange is called “mixed ventilation”.
Significantly better and more comfortable conditions for the air microclimate in the area where people live indoors are provided when using the so-called scheme. "displacement ventilation". The air prepared in the central supply unit is supplied through special floor air distributors directly into the living area of people in the room.
According to the conditions of thermal comfort, the temperature of the supply external air hpn should not be lower than the following values: in winter at t in = 20 °C inflow t pnh = 20 - 3 = 17 °C; in summer at t in = 25 °C, inflow t in = 25 - 5 = 20 °C. The speed of supply air entering the room from floor air distributors should be no higher than vpn = 0.3 m/s.
For the ward in question, floor-mounted supply air distributors must have a supply cross-sectional area of the following size:
The outer wall has an area of 5 x 3 = 15 m2. It contains a window with an area of 2.5 x 2 = 5 m2. According to modern standards for thermal protection of buildings, walls in the Moscow climate should have a thermal resistance R st = 3.5 m 2 *s/W, windows - R approx = 0.6 m 2 *s/W. Let's calculate the estimated transmission heat losses.
Losses through the wall:
losses through the window:
General heat loss
With an apparent heat gain of 540 Wh from six sick people in the room under consideration, the calculated transmission heat losses of 537 Wh are fully compensated. The heating system is left with heat compensation for reheating the supply outside air from t pnx = 17 °C to t px = 20 °C:
Significantly better conditions for the created air microclimate in the area where people live indoors are provided when using the “displacement ventilation” scheme
Currently, in many hospitals in our country it can be observed that the supply ventilation systems built according to the project are not used by the operation service due to the desire to save heat on heating the supply air. The wards create stuffiness, odors, and gas pollution. Therefore, patients open the transoms, and cold outside air enters the room. To heat cold air in sanitary norm quantities, the system must consume heat:
The specific design load on the heating system of the room in the absence of a supply ventilation system and the entry of sanitary norms of outside air through the open transom in the window is:
A significant reduction in the estimated heat consumption for heating and ventilation of hospital wards can be achieved by using energy-saving technology for operating EQA systems, described in detail in.
The simplest and most economical energy-saving FOC system is carried out by installing domestic heat exchangers of the KSK model made of bimetallic rolling finned tubes in the supply and exhaust units after the air filters, which ensures their high thermal efficiency and low aerodynamic resistance. The heat exchangers in the supply and exhaust units are connected to each other by pipelines on which a pump and a sealed expansion tank are installed.
The assembled disposal system is washed with water, drained and filled with antifreeze with a freezing point 5 °C below the design temperature of the cold outside air. In the climate of Moscow, the concentration of antifreeze should be selected for freezing temperature conditions no higher than:
The thermal efficiency of this energy saving system with pump circulation of antifreeze is assessed by an indicator that has the form:
where t Нx2 is the temperature of the supply external air after the heat exchangers in the supply unit, °C; t y1 is the temperature of the air removed from the ceiling of the rooms [°C], with a mixing ventilation scheme (supply and exhaust under the ceiling) t y1 = t in = 20 °C, with a displacement ventilation scheme we take the values t y1 = 23 °C and Θ t .yy = 0.4.
NPF Khimkholodservice has developed an original adiabatic air cooling device. The required number of sheets made of hygroscopic material is installed along the cross-section of the apparatus
Let us transform the indicator according to formula (1) to the form of calculating the temperature value t nx2:
The required heat for heating the sanitary system is l pn = 480 m 3 / h in the supply unit, which implements an energy-saving system with pump circulation of antifreeze:
The estimated heat consumption due to the use of an energy-saving ventilation system is reduced by:
The paper provides a calculation of reducing the annual heat consumption in the supply and exhaust system in the Moscow climate using an energy-saving system with pump circulation of antifreeze. A specific indicator for reducing heat consumption during the heating period of 20 kW/(year-m3) and a formula for calculating the amount of heat saved per year were obtained:
Let us assume that the hospital has 400 beds in wards for treating patients. These wards are served by a supply ventilation system, the capacity of which is: l pn = 400 x 80 = 32,000 m 3 /h.
Supply and exhaust ventilation systems in hospital wards operate 24 hours a day, i.e. t wok = 24. Using formula (2) we obtain:
According to 2011 tariffs, the cost of 1 kW of heat from a heat supply system from a fuel cell is 1.4 rubles/kW. Cost of heat saved per year:
Q t.yy = 640,000 x 1.4 = 896,000 rub.
The cost of a recycling system with pump circulation for supply and exhaust systems with a capacity of 32 thousand m 3 /h is estimated at 600 thousand rubles. So, the use of a recycling unit in supply and exhaust systems in hospitals pays for itself in less than one year.
The recent summer of 2010 was very hot and dry. At midday, the outside air temperature increased to t nm1 = 34 °C, with a wet-bulb temperature not exceeding t nm1 = 18 °C. In hot and dry climates, it is effective and economical to use the simplest and most economical method of adiabatic cooling of incoming outdoor air, the effectiveness of which is assessed by the indicator:
where t H2 is the temperature value of adiabatically humidified supply external air.
The original adiabatic air cooling device was developed at the research and production company Khimkholodservis. The required number of sheets made of hygroscopic material is installed along the cross-section of the apparatus. The number of canvases depends on the required value of the E a indicator. For E a = 0.8, it is necessary to sequentially install eight blades along the air flow, which are moistened through slots in the upper tension pipe for a tape of two blades. To achieve E a = 0.8, four tapes and four tension pipes are installed. The depth of the apparatus along the air flow is no more than 0.3 m.
Drinking quality tap water flows into the pipes, which moisturizes the fabric material. All moisture absorbed by the material of the canvases evaporates into the air passing through them. Therefore, there is no water recirculation, as is typical for traditional adiabatic humidifiers with pumped circulation of water irrigating a nozzle made of corrugated plastic sheets. Therefore, the new pumpless adiabatic humidifier does not pollute the air with bacteria that can develop in the warm water of the trays of traditional adiabatic humidifiers.
The authors have developed a scheme for two-stage evaporative cooling of supply external air, which can be quite simply built into existing supply and exhaust units in hospitals. The first stage uses a recycling installation with pump circulation of antifreeze, discussed in detail above in operating mode during the cold season. After the air filter in the exhaust units, an adiabatic exhaust air humidifier with an index of E a = 0.8 is added. An adiabatic humidifier E a = 0.6 is installed in the supply unit after the heater.
In Fig. Figure 1 shows the construction in the i-d diagram of humid air of a two-stage evaporative cooling mode of supply external air, which at midday has a dry-bulb temperature of t nt = 34 °C and a wet-bulb temperature of t nm1 = 18 °C, and the exhaust air has a dry-bulb temperature of thermometer t у1 = 28 °C and wet thermometer t ум1 = 19 °C. Let us transform expression (3) to the form of finding the air temperature after adiabatic humidification:
We use expression (4) to calculate the temperature of the exhaust air after adiabatic humidification in an apparatus with E a = 0.8:
Passing through the heat exchanger recovery installations, the exhaust air with t y2 = 20.8 °C through the walls of the finned tubes will cool the antifreeze passing through the tubes to a temperature t af = 23 °C, from which the pump will supply cooled antifreeze into the heat exchanger tubes in the air supply unit. The thermal efficiency of a heat exchanger is determined by:
where t H2 is the outside air temperature after the heat exchanger, °C. Let us transform expression (5) to the form of calculating the temperature t nx2 at Θ t = 0.7:
On the i-d diagram (Fig. 1) we find the value t nm2 = 15.6 °C. An adiabatic humidifier with E a = 0.6 is installed in the supply unit. We calculate the temperature of the supply outside air after adiabatic humidification:
In the supply fan and air ducts, air with tn3 = 19.9 °C will be heated by 1 °C and with a temperature tpn = 20.9 °C will enter the area of the beds with patients through the floor air distributor, displacing the generated excess heat and water vapor to the ceiling and gases, where the temperature of the displaced air will increase to tу1 = 28 °С and tум1 = 19 °С (see construction in Fig. 1).
The calculations carried out and plotted on the i-d diagram in Fig. 1 showed that adiabatic humidification can ensure the maintenance of a comfortable temperature tb = 25 °C in hospital wards. Currently, hospital wards generally do not have air cooling facilities. This leads to the fact that in a hot summer, when t H = 34 °C increases and such heat persists for more than two months, the temperature in the premises will rise to t ≈ 30-34 °C. This creates extremely difficult conditions for people in these premises. This especially adversely affects the physical condition of people with various diseases of the cardiovascular system.
Complementing traditional ventilation systems with adiabatic humidification devices and recycling systems with pump circulation of antifreeze will pay for itself in less than a year due to a reduction of up to 50% of heat consumption during the cold season and improvement of comfortable conditions for patients in the wards on hot summer days.
How much air does a person need for normal existence?
Ventilation of premises ensures the timely removal of excess carbon dioxide, heat, moisture, dust, harmful substances, in general, the results of various household processes and the presence of people in the premises.
Types of ventilation.
1) Natural. Consists of natural air exchange between
location and external environment due to the temperature difference between the internal and external
outside air, wind, etc.
Natural ventilation can be:
Disorganized (by filtering air through cracks)
Organized (through open vents, windows, etc.) - ventilation.
2) Artificial.
Supply air - artificial supply of outside air into the room.
Exhaust - artificial extraction of air from a room.
Supply and exhaust - artificial supply and exhaust. Air enters through the supply chamber, where it is heated, filtered and removed through ventilation.
The general principle of ventilation is that
In dirty rooms, exhaust should predominate (to prevent the spontaneous entry of dirty air into adjacent rooms)
In clean rooms, inflow should prevail (so that air from dirty rooms does not enter them).
How to determine how much clean air should enter a room per hour per person in order for ventilation to be sufficient?
The amount of air that needs to be supplied to a room per person per hour is called ventilation volume.
It can be determined by humidity, temperature, but most accurately determined by carbon dioxide.
Methodology:
The air contains 0.4%<■ углекислого газа. Как уже упоминалось, для помещений, требующих высокого уровня чистоты (палаты, операционные), допускается содержание углекислого газа в воздухе не более 0.7 /~ в обычных помещениях допускается концентрация до 1 Л«.
When people stay indoors, the amount of carbon dioxide increases. One person produces approximately 22.6 liters of carbon dioxide per hour. How much air must be supplied per person per hour in order to dilute these 22.6 liters so that the concentration of carbon dioxide in the air in the room does not exceed 0.7%° or 1/<.. ?
Each liter of air supplied to the room contains 0.4%° carbon dioxide, that is, each liter of this air contains 0.4 ml of carbon dioxide and thus can still “accept” 0.3 ml (0.7 - 0.4) for clean rooms (up to 0.7 ml per liter or 0.7 /~) and 0.6 ml (1 - 0.4) for ordinary rooms (up to 1 ml per liter or 1 /~).
Since every hour 1 person produces 22.6 liters (22600 ml) of carbon dioxide, and each liter of supplied air can “accept” the above number of ml of carbon dioxide, the number of liters of air that must be supplied to the room per 1 person per hour is
For clean rooms (wards, operating rooms) - 22600 / 0.3 = 75000 l = 75 m 3. That is, 75 m 3 of air per person per hour must enter the room so that the concentration of carbon dioxide in it does not exceed 0.7%*
For ordinary premises - 22600 / 0.6 = 37000 l = 37 m3. That is, 37 m of air per person per hour must enter the room so that the concentration of carbon dioxide in it does not exceed.
If there is more than one person in the room, then the indicated numbers are multiplied by the number of people.
It was explained in detail above how the value of the ventilation volume is found directly on specific numbers, but in general it is not difficult to guess that the general formula looks like this:
b = (K * M) / (P - P0 = (22.6 l * 14) / (P - 0.4%.)
b - ventilation volume (m)
K - the amount of carbon dioxide exhaled by a person per hour (l)
N - number of people in the room
P - maximum permissible carbon dioxide content in the room (/“)
Using this formula, we calculate the required volume of supplied air (required volume of ventilation). In order to calculate the real volume of air that is supplied to a room per hour (real volume of ventilation), you need to substitute the real concentration of carbon dioxide in a given room in ppm into the formula instead of P (maximum concentration of carbon dioxide - 1/C 0.7 U"):
^ real-
- (22.6 l * 14) / ([C0 2 ] fact - 0.4 /~)
b real - real volume of ventilation
[SSYfact - actual carbon dioxide content in the room
To determine the concentration of carbon dioxide, the Subbotin-Nagorsky method is used (based on reducing the titer of caustic Ba, the most accurate), the Rehberg method (also using caustic Ba, express method), Prokhorov’s method, photocolorimetric method, etc.
Another quantitative characteristic of ventilation, directly related to the volume of ventilation, is the ventilation rate. The ventilation rate shows how many times per hour the air in the room is completely exchanged.
Ventilation rate - The volume of what gets (extracted 4) into the chug. air dry I
Room volume.
Accordingly, in order to calculate the required ventilation rate for a given room, you need to substitute the required volume of ventilation in the numerator of this formula. And in order to find out what the real ventilation rate in the room is, substitute the real volume of ventilation into the formula (see calculation above).
The ventilation ratio can be calculated by inflow (inflow ratio), then the volume of air supplied per hour is substituted into the formula and the value is indicated with a (+) sign, or it can be calculated by exhaust (exhaust ratio), then the volume of air extracted per hour is substituted into the formula and the value is indicated with a (-) sign.
For example, if in an operating room the ventilation ratio is designated as +10, -8, then this means that every hour ten times the volume of air relative to the volume of the room is supplied to this room and eight times is extracted.
There is such a thing as an air cube.
An air cube is the volume of air required for one person.
The air cube norm is 25-27 m. But as was calculated above, for one person per hour it is required to supply an air volume of 37 m, that is, for a given air cube norm (given room volume), the required air exchange rate is 1.5 (37 m / 25 m = 1.5).
Microclimate of hospital premises.
Temperature regime.
Temperature changes should not exceed:
In the direction from the inner to the outer wall - 2°C
In the vertical direction - 2.5°C per meter of height
During the day with central heating - 3°C
Relative air humidity should be 30-60%
Air speed - 0.2-0.4 m/s
6. The problem of nosocomial infections; nonspecific prevention measures, purpose and content.
NOMACHICAL INFECTIONS - any clinically recognizable disease caused by microorganisms that occurs in patients as a result of staying in a medical institution or seeking medical help, as well as in medical personnel as a result of their professional activities (World Health Organization).
Nonspecific prevention.
Architectural and planning activities
· Construction and reconstruction of inpatient and outpatient clinics in compliance with the principle of rational architectural and planning solutions:
· insulation of sections, wards, operating units, etc.;
· compliance and separation of flows of patients, personnel, “clean” and “dirty” flows;
· rational placement of departments on floors;
· correct zoning of the territory
Sanitary measures
· effective artificial and natural ventilation;
· creation of regulatory conditions for water supply and sanitation;
· correct air supply;
· air conditioning, use of laminar flow units;
· creation of regulated parameters of microclimate, lighting, noise conditions;
· compliance with the rules for the accumulation, neutralization and disposal of waste from medical institutions.
Sanitary and anti-epidemic measures
· epidemiological surveillance of nosocomial infections, including analysis of the incidence of nosocomial infections;
· control over the sanitary and anti-epidemic regime in medical institutions;
· introduction of a hospital epidemiologist service;
· laboratory monitoring of the state of the anti-epidemic regime in health care facilities;
· identification of bacteria carriers among patients and personnel;
· compliance with the norms for the placement of patients;
· inspection and admission of personnel to work;
· rational use of antimicrobial drugs, primarily antibiotics;
· training and retraining of personnel on issues of regime in health care facilities and prevention of nosocomial infections;
· sanitary educational work among patients.
Disinfection and sterilization measures.
· use of chemical disinfectants;
· use of physical methods of disinfection;
· pre-sterilization cleaning of instruments and medical equipment;
ultraviolet bactericidal irradiation;
· chamber disinfection;
· steam, dry air, chemical, gas, radiation sterilization;
· carrying out disinsection and deratization.