1. Energy expenditure of the body under conditions of physical activity. Physical activity rate. Work increase.
2. Regulation of metabolism and energy. Metabolic regulation center. Modulators.
3. Blood glucose concentration. Scheme for regulating glucose concentration. Hypoglycemia. Hypoglycemic coma. Feeling hungry.
4. Nutrition. Nutritional norm. The ratio of proteins, fats and carbohydrates. Energy value. Calorie content.
5. Diet of pregnant and lactating women. Baby food ration. Distribution of daily ration. Dietary fiber.
6. Rational nutrition as a factor in maintaining and strengthening health. Healthy lifestyle. Meal regimen.
7. Body temperature and its regulation. Homeothermic. Poikilothermic. Isothermy. Heterothermic organisms.
8. Normal body temperature. Homeothermic nucleus. Poikilothermic shell. Comfort temperature. Human body temperature.
9. Heat production. Primary heat. Endogenous thermoregulation. Secondary heat. Contractile thermogenesis. Non-contractile thermogenesis.
There are the following ways for the body to release heat: into the environment: radiation, heat conduction, convection And evaporation.
Radiation- this is a way of releasing heat into the environment by the surface of the human body in the form electromagnetic waves infrared range (a = 5-20 microns). The amount of heat dissipated by the body into the environment by radiation is proportional to the surface area of the radiation and the difference in the average temperatures of the skin and environment. Radiation surface area is the total surface area of those parts of the body that come into contact with air. At an ambient temperature of 20 °C and a relative air humidity of 40-60%, the adult human body dissipates by radiation about 40-50% of the total heat given off. Heat transfer by radiation increases as the ambient temperature decreases and decreases as it increases. In conditions constant temperature environment, radiation from the body surface increases as the skin temperature increases and decreases as it decreases. If the average temperatures of the surface of the skin and the environment are equalized (the temperature difference becomes equal to zero), heat transfer by radiation becomes impossible. It is possible to reduce the heat transfer of the body by radiation by reducing the surface area of the radiation (“curling the body into a ball”). If the ambient temperature exceeds the average skin temperature, the human body, absorbing infrared rays emitted by surrounding objects, warms up.
Rice. 13.4. Types of heat transfer. Ways the body releases heat external environment can be conditionally divided into “wet” heat transfer, associated with the evaporation of sweat and moisture from the skin and mucous membranes, and into “dry” heat transfer, which is not associated with fluid loss.Thermal conduction- a method of heat transfer that occurs during contact or contact of the human body with others physical bodies. The amount of heat given off by the body to the environment in this way is proportional to the difference in the average temperatures of the contacting bodies, the area of the contacting surfaces, the time of thermal contact and the thermal conductivity of the contacting body. Dry air adipose tissue characterized by low thermal conductivity and are heat insulators. Using clothing made from fabrics that contain a large number of small, stationary air “bubbles” between the fibers (e.g. wool fabrics), enables the human body to reduce heat dissipation through thermal conductivity. Humid air and water saturated with water vapor are characterized by high thermal conductivity. Therefore, a person’s stay in an environment with high humidity and low temperature is accompanied by increased heat loss from the body. Wet clothing also loses its insulating properties.
Convection- a method of heat transfer from the body, carried out by transferring heat by moving air (water) particles. To dissipate heat by convection, a flow of air with a lower temperature than the temperature of the skin is required over the surface of the body. In this case, the layer of air in contact with the skin heats up, reduces its density, rises and is replaced by colder and more dense air. Under conditions when the air temperature is 20 °C and the relative humidity is 40-60%, the body of an adult dissipates about 25-30% of heat into the environment through heat conduction and convection (basic convection). When driving speed increases air flow(wind, ventilation) the intensity of heat transfer also increases significantly (forced convection).
Heat release from the body by heat conduction, convection And out of the way meanings, called together "dry" heat transfer, becomes ineffective when the average temperatures of the body surface and the environment are equalized.
Heat transfer by evaporation- this is the body’s way of dissipating heat into the environment due to its expenditure on the evaporation of sweat or moisture from the surface of the skin and moisture from the mucous membranes respiratory tract(“wet” heat transfer). In humans, sweat is constantly secreted by the sweat glands of the skin (“palpable,” or glandular, loss of water), and the mucous membranes of the respiratory tract are moisturized (“imperceptible” loss of water) (Fig. 13.4). At the same time, “perceptible” loss of water by the body has a more significant impact on total quantity heat given off by evaporation than “imperceptible.”
At an external temperature of about 20 "C, the evaporation of moisture is about 36 g/h. Since 0.58 kcal of thermal energy is spent on the evaporation of 1 g of water in a person, it is easy to calculate that through evaporation the body of an adult person releases about 20% of total heat dissipation. Increase in external temperature, execution. physical work, prolonged stay in heat-insulating clothing increases sweating and it can increase to 500-2000 g/h. If the external temperature exceeds the average skin temperature, then the body cannot release heat to the external environment by radiation, convection and heat conduction. Under these conditions, the body begins to absorb heat from the outside, and the only way heat dissipation becomes increased evaporation of moisture from the surface of the body. Such evaporation is possible as long as the ambient air humidity remains less than 100%. With intense sweating, high humidity and low air speed, when drops of sweat, without having time to evaporate, merge and flow from the surface of the body, heat transfer by evaporation becomes less effective.
For reducing heat consumption strict is needed accounting for heat losses in technological equipment and heating networks. Heat losses depend on the type of equipment and pipelines, their correct operation and the type of insulation.
Heat loss (W) is calculated using the formula
Depending on the type of equipment and pipeline, the total thermal resistance is:
For insulated pipeline with one layer of insulation:
for an insulated pipeline with two layers of insulation:
for technological devices with multilayer flat or cylindrical walls with a diameter of more than 2 m:
for technological devices with multilayer flat or cylindrical walls with a diameter of less than 2 m:
carrier to the inner wall of the pipeline or apparatus and from the outer surface of the wall into the environment, W/(m 2 - K); X tr, ?. st, Xj - thermal conductivity, respectively, of the pipeline material, insulation, apparatus walls, i-th layer of the wall, W/(m K); 5 ST. — apparatus wall thickness, m.
The heat transfer coefficient is determined by the formula
or according to the empirical equation
The transfer of heat from the walls of a pipeline or apparatus to the environment is characterized by the coefficient a n [W/(m 2 K)], which is determined by criterion or empirical equations:
according to criterion equations:
Heat transfer coefficients a b i a n are calculated using criterion or empirical equations. If the hot coolant is hot water or condensing steam, then a in > a n, i.e. R B< R H , и величиной R B можно пренебречь. Если горячим теплоносителем является воздух или перегретый пар, то а в [Вт/(м 2 - К)] рассчитывают по критериальным уравнениям:
according to empirical equations:
Thermal insulation of devices and pipelines is made of materials with low thermal conductivity. Well-chosen thermal insulation can reduce heat loss into the surrounding space by 70% or more. In addition, it increases the productivity of thermal installations and improves working conditions.
Thermal insulation of a pipeline consists mainly of one layer, covered on top for strength with a layer of sheet metal (roofing steel, aluminum, etc.), dry plaster from cement mortars, etc. If a covering layer of metal is used, its thermal resistance can be neglected. If the covering layer is plaster, then its thermal conductivity differs slightly from the thermal conductivity of thermal insulation. In this case, the thickness of the coating layer is, mm: for pipes with a diameter of less than 100 mm - 10; for pipes with a diameter of 100-1000 mm - 15; for pipes with large diameter - 20.
The thickness of the thermal insulation and cover layer should not exceed the maximum thickness, depending on the mass loads on the pipeline and its overall dimensions. In table Table 23 shows the values of the maximum thickness of steam pipeline insulation recommended by the thermal insulation design standards.
Thermal insulation of technological devices can be single-layer or multi-layer. Heat loss through thermal
insulation depends on the type of material. Heat loss in pipelines is calculated per 1 and 100 m of pipeline length, in technological equipment - per 1 m 2 of the surface of the apparatus.
A layer of contaminants on the inner walls of pipelines creates additional thermal resistance to the transfer of heat into the surrounding space. Thermal resistances R (m. K/W) during the movement of some coolants have the following values:
In the pipelines supplying technological solutions to devices and hot coolants to heat exchange units, there are shaped parts in which part of the heat of the flow is lost. Local heat loss (W/m) is determined by the formula
Local resistance coefficients of pipeline fittings have the following values:
When compiling the table. 24 calculation of specific heat losses was carried out for seamless steel pipelines (pressure< 3,93 МПа). При расчете тепловых потерь исходили из следующих данных: тем-
the air temperature in the room was taken to be 20 °C; its speed during free convection is 0.2 m/s; steam pressure - 1x10 5 Pa; water temperature - 50 and 70 °C; thermal insulation is made in one layer of asbestos cord, = 0.15 W/(m K); heat transfer coefficient a„ = 15 W/(m 2 - K).
Example 1. Calculation of specific heat losses in a steam pipeline.
Example 2. Calculation of specific heat losses in a non-insulated pipeline.
Specified conditions
Steel pipeline with a diameter of 108 mm. Nominal diameter d y = 100 mm. Steam temperature 110°C, ambient temperature 18°C. Thermal conductivity of steel X = 45 W/(m K).
The data obtained indicate that the use of thermal insulation reduces heat losses per 1 m of pipeline length by 2.2 times.
Specific heat losses, W/m2, in technological equipment for tanning and fulling-felt production are:
Example 3. Calculation of specific heat losses in technological devices.
1. The “Giant” drum is made of larch.
2. Dryer from Hirako Kinzoku.
3. Longboat for dyeing berets. Made of stainless steel [k = 17.5 W/(m-K)]; there is no thermal insulation. Overall dimensions of the longboat 1.5 x 1.4 x 1.4 m. Wall thickness 8 ST = 4 mm. Process temperature t = = 90 °C; air in the workshop / av = 20 °C. Air speed in the workshop v = 0.2 m/s.
The heat transfer coefficient can be calculated as follows: a = 9.74 + 0.07 At. At /av = 20 °C a is 10-17 W/(m 2 K).
If the surface of the coolant of the apparatus is open, the specific heat losses from this surface (W/m2) are calculated using the formula
Industrial service "Capricorn" (Great Britain) proposes to use the "Alplas" system to reduce heat losses from open surfaces of coolants. The system is based on the use of hollow polypropylene floating balls that almost completely cover the surface of the liquid. Experiments have shown that at a water temperature in an open tank of 90 °C, heat losses when using a layer of balls are reduced by 69.5%, two layers - by 75.5%.
Example 4. Calculation of specific heat losses through the walls of a drying unit.
The walls of the drying unit can be made of various materials. Consider the following wall designs:
1. Two layers of steel 5 ST = 3 mm thick with insulation between them in the form of an asbestos board 5 I = 3 cm thick and thermal conductivity X U = 0.08 W/(m K).
IN. A. Vinogradov- Saltykov, National university food technologies (G. Kyiv), IN. G. Fedorov, Open international university development person "Ukraine" (G. Kyiv), IN. P. Martsenko, Branch Kievenergo "Zhilteploenergo" (G. Kyiv)
It is shown that the actual heat losses from the external surfaces of hot water boilers q 5 are significantly less than the standard losses, which were determined from graphs or tables compiled for high-performance steam boilers by extrapolation to the area of low thermal productivity of the boilers. This decrease in q 5 is explained by lower temperatures of the outer surfaces of the lining. Thus, when the DKVR steam boiler is switched to hot water mode, the temperature conditions of all boiler elements change, which leads to a decrease in heat losses to the environment.
To determine q 5, direct measurements of density were made heat flow q from the external surfaces of the boiler using small-sized, low-inertia heat meters. The distribution of heat losses over individual surfaces of steam and hot water boilers turned out to be uneven, therefore, to calculate q 5, local values of q were measured within each surface, combining the gradient method of searching for maximum heat losses and the scanning method, as well as using statistical methods of averaging experimental data over the surface and in time
Averaging the value of q (W/m2) in this way for each element F (m2) of the outer surface of the boiler was used to calculate q5:
where QhР - lower heat gas combustion per working mass, J/m 3 ; B - gas consumption, m 3 /s.
The experiments were carried out, as a rule, under conditions of industrial operation of boilers, i.e. their performance differed from nominal. Therefore, we tested the inverse dependence of heat losses on the actual heating output of the boiler, which is accepted for steam boilers:
where D and q 5 are the actual boiler performance and heat loss from external surfaces, D H and q 5 H are the same for nominal conditions.
To test (2), experiments were carried out on a KVG-6.5 boiler, the front and side walls of which, after dismantling the brick lining, were replaced with fireclay-fiber slabs ShPGT-450. To change the thermal performance of the boiler, the gas flow rate and, accordingly, the increase in water temperature in the boiler were changed, maintaining the water flow rate constant. In the range of changes in D, the maximum possible for the operating conditions of the boiler, formula (2) turned out to be valid: recalculation using it for all actual D gave almost the same value q 5 H = 0.185%. For the KVG-6.5 boiler with traditional lining, tests showed heat loss q 5 H = 0.252%. By completely replacing the lining with SHPGT-450 slabs and carefully sealing the joints between them, you can count on a reduction in q 5 and gas consumption by 0.10-0.15%. With a massive replacement of lining during repairs, this can make a significant contribution to energy and resource saving, since a reduction in gas consumption by 0.1% in the system of the Kievenergo branch “Zhilteploenergo” leads to gas savings of 1300 m3/day. .
The conclusions were confirmed that the actual heat losses from the external surfaces of hot water boilers are several times lower than the standard ones. Thus, the developers of compact TVG boilers, employees of the Gas Institute of the National Academy of Sciences of Ukraine, measured with surface thermometers during acceptance tests 
average temperature of the outer surfaces of the boiler walls and known formulas calculated q 5 . For TVG-4 and TVG-8 boilers, the standard losses are 2%, and the calculated losses increased when the load was reduced from nominal to the minimum practical for TVG-4 from 0.54 to 1%, for TVG-8 from 0.33 to 0.94 %. Therefore, the Institute recommended in 2000 that organizations operating boilers of this type take the average value q 5 = 0.75%.
Similar conclusions were reached during the study of KVG boilers developed at the Gas Institute of the National Academy of Sciences of Ukraine. To determine q5, formula (1) was also used here, but instead of 2(cjF), qF K was substituted, where F K is the total outer area of the boiler thermal insulation. Average value q was calculated using the formula:
Here the heat flux density from the outer surface of the insulation to the air q o and from inner surface to air q T is determined from the formulas:
where a is the total coefficient of heat transfer to the environment; t 0 , t T , t B - temperatures of the outer, inner surface and air; R is the total thermal resistance of the lining layers; R 0 = 1/a 0 .
It is recommended to determine the values of t T and t 0 by direct measurements or by the calculation method, R - calculated depending on the thickness and thermal conductivity of the insulation layers, and a 0 - according to the well-known Kammerer formulas for flat and cylindrical surfaces.
When calculating q 0 and q T, their values differed significantly, although during stationary operation of the boiler they were almost the same. The reason that q T >q 0 turned out can be explained by the fact that due to the inevitable forced air circulation in the boiler room, the actual values of a 0 are 12-15% higher than the calculated ones, as was shown by direct measurements of q 0 and (t 0 - t B on the TGMP-314A steam boiler. Because of this difference in q 0 and q T, K K is introduced in (3) - a correction factor for the error of measurements and calculations q 0 and q T, which is recommended to be taken in the range of 0.3-0 ,7. Apparently, with equal confidence in both quantities, you need to take their half-sum.
To take into account additional heat loss through thermal bridges, the coefficient K M = 0.2-0.4 is introduced.
In addition to the introduction of K K and K M, it is proposed to increase q 5 by 10-20% to take into account heat losses through the lower (bottom) hard-to-reach surface of the boiler, as well as take into account the share of losses from external surfaces that returns to the furnace and boiler flues along with air from the boiler room.
Despite the significant differences in the methods for determining q 5 in and , the results were similar, which gives grounds for generalizing these results and their use in compiling regulatory documents. The figure shows the dependence of q 5 on the nominal heat output of water-heating boilers NIISTU-5, NIISTU-5x2, TVG-4, TVG-8, KVG-4, KVG-6.5, as well as KVG-4, KVG-6.5, KVGM -10 and KVGM-50. Data from and lie somewhat lower than the corresponding data from , but such a difference is quite justified using different methods research.
Literature
1. Fedorov IN. G., Vinogradov- Saltykov IN. A., Martsenko IN. P. Measurement losses heat from outdoor surfaces hot water boilers // Ecotechnologies And resource saving. 1997. № 3. WITH. 66-68.
2. Martsenko IN. P., Fedorov IN. G. Efficiency insulating fencing hot water boilers // Prom. heating engineering. 2000. T. 22, № 2. WITH. 78-80.
3. FedoriV IN. G., Vinogradov- Saltikov IN. A., Martsenko IN. P. Rozpodil heat consumption By fenced gardens water heateriof them Taparovich boileriV / UDUKHT. TO., 1998. 16 With. Dep. V DNTB Uk- raineither23.03.98, № 142.
4. Fedorov IN. G., Pleskonos A. TO. Planning And implementation experiments V food industry. M.: food. prom- there is, 1980. 240 With.
5. MarczakI. AND., GolyshevL. IN., Mysaki. WITH. Methodology definitions losses heat steam boiler V environment// Thermal power engineering. 2001. № 10. WITH. 67-70.
6. Zalkind E. M. Materials brickwork And calculation fencing steam boilers. M.: Energy, 1972. 184 With.
7. CammererJ.S. Erleuchtungen zu den VDI - Rechtlinien fuerWaerme - und Kalteschutz - Brennstoff - Waerme - Kraft.1958. Bd.10, № 3. S.119-121.
8. Fedorov IN. G., Vinogradov- Saltykov IN. A., Novik M. AND. Thermometry outdoor surfaces boiler TGMP-314 A // Ecotechnologies And resource saving. 1999. № 4. WITH. 77-79.
Thermal pollution refers to phenomena in which heat is released into bodies of water or into the atmospheric air. This raises the temperature much higher average norm. Thermal pollution of nature is associated with human activities and greenhouse gas emissions, which are the main cause of global warming.
Sources of thermal pollution of the atmosphere
There are two groups of sources:
- natural - these are forest fires, volcanoes, hot winds, decomposition processes of living and plant organisms;
- anthropogenic - this is oil and gas processing, industrial activity, thermal power engineering, nuclear energy, transport.
Every year, about 25 billion tons of carbon monoxide, 190 million tons of sulfur oxide, and 60 million tons of nitrogen oxide enter the Earth's atmosphere as a result of human activity. Half of all this waste is added as a result of activities energy industry, industry and metallurgy.
For recent years The amount of exhaust gases from cars has increased.
Consequences
In metropolitan cities with large industrial enterprises, the atmospheric air experiences severe thermal pollution. It receives substances that have more high temperature than the air layer of the surrounding surface. The temperature of industrial emissions is always higher than the average surface air layer. For example, when forest fires, from the exhaust pipes of cars, from the pipes of industrial enterprises, and when heating houses, streams of warm air with various impurities are released. The temperature of such a flow is approximately 50-60 ºС. This layer increases the average annual temperature in the city by six to seven degrees. “Heat islands” form in and above cities, which leads to an increase in cloudiness, while the amount of precipitation increases and air humidity increases. When combustion products add to moist air, moist smog (London type) is formed. Ecologists say that over the past 20 years, the average temperature of the troposphere has increased by 0.7º C.
Sources of thermal soil pollution
Sources of thermal pollution of soils in the territory major cities and industrial centers are:
- gas pipes of metallurgical enterprises, temperatures reach 140-150ºС;
- heating mains, temperature about 60-160ºС;
- communication outlets, temperature 40-50º C.
Consequences of thermal influence on soil cover
Gas pipes, heating mains and communication outlets increase the soil temperature by several degrees, which negatively affects the soil. In winter, this leads to snow melting and, as a consequence, freezing surface layers soil, and in summer the process is reversed, the top layer of soil heats up and dries out. is closely related to the vegetation and living microorganisms that live in it. Changes in its composition negatively affect their life.
Sources of thermal pollution of hydrological objects
Thermal pollution of water bodies and coastal marine areas occurs as a result of discharge into water bodies waste water nuclear and thermal power plants, industrial enterprises.
Consequences of wastewater discharges
The discharge of wastewater leads to an increase in water temperature in reservoirs by 6-7 ºС; the area of such warm spots can reach up to 30-40 km2.
Warm layers of water form a kind of film on the surface of the water mass, which prevents natural water exchange; they do not mix with the bottom), the amount of oxygen decreases, and the need of organisms for it increases, while the species number of algae increases.
The greatest degree of thermal water pollution is caused by power plants. Water is used to cool turbines of nuclear power plants and gas condensate in thermal power plants. The water used by power plants is heated by approximately 7-8 ºС, after which it is discharged into nearby reservoirs.
An increase in water temperature in reservoirs negatively affects living organisms. For each of them there is an optimum temperature at which the population feels excellent. IN natural environment with a slow increase or decrease in temperature, living organisms gradually adapt to the changes, but if the temperature rises sharply (for example, with a large volume of waste discharges from industrial enterprises), then the organisms do not have time for acclimatization. They receive heat shock, which can result in death. This is one of the most negative consequence thermal pollution for aquatic organisms.
But there may be other, more harmful consequences. For example, the effect of thermal water pollution on metabolism. As the temperature increases, the metabolic rate of organisms increases and the need for oxygen increases. But as the temperature of the water rises, the oxygen content in it decreases. Its lack leads to the death of many species of aquatic living organisms. Almost one hundred percent destruction of fish and invertebrates causes an increase in water temperature by several degrees per day. summer time. When changing temperature regime The behavior of fish also changes, natural migration is disrupted, and untimely spawning occurs.
Thus, an increase in water temperature can change the species structure of water bodies. Many species of fish either leave these territories or die. The algae characteristic of these places are replaced by heat-loving species.
If together with warm water organic and minerals(domestic wastewater, mineral fertilizers washed away from fields), a sharp proliferation of algae occurs, they begin to form a dense mass, covering each other. As a result of this, they die and rot, which leads to the death of all living organisms in the reservoir.
Thermal pollution of water bodies poses a danger. They generate energy using turbines; the exhaust gas must be cooled from time to time. Used water is discharged into water bodies. On large quantity reaches up to 90 m 3. This means that a continuous warm flow enters the reservoir.
Damage from pollution of aquatic ecosystems
All the consequences of thermal pollution of water bodies cause catastrophic harm to living organisms and change the human environment. As a result of pollution, damage is caused to:
- aesthetic (violated appearance landscapes);
- economic (liquidation of the consequences of pollution, disappearance of many species of fish);
- ecological (species of aquatic vegetation and living organisms are destroyed).
The volumes of warm water discharged by power plants are constantly growing, therefore, the temperature of water bodies will also increase. In many rivers, according to ecologists, it will increase by 3-4 °C. This process is already underway. For example, in some rivers in America the water overheating is about 10-15 °C, in England - 7-10 °C, in France - 5 °C.
Thermal pollution of the environment
Thermal pollution (thermal physical pollution) is a form that occurs as a result of an increase in environmental temperature. Its causes are industrial and military emissions of heated air, large fires.
Thermal pollution of the environment is associated with the work of enterprises in the chemical, pulp and paper, metallurgical, woodworking industries, thermal power plants and nuclear power plants, which require large volumes of water to cool equipment.
Transport is a powerful pollutant of the environment. About 80% of all annual emissions come from cars. Many harmful substances disperse over considerable distances from the source of pollution.
When burning gas at thermal power plants, in addition to the chemical impact on the atmosphere, thermal pollution also occurs. In addition, within a radius of approximately 4 km from the torch, many plants are in a depressed state, and within a radius of 100 meters, the vegetation cover dies.
Every year, about 80 million tons of various industrial and domestic wastes are generated on the territory of Russia, which are a source of pollution of soil cover, vegetation, underground and surface waters, atmospheric air. In addition, they are a source of radiation and thermal pollution of natural objects.
Land waters are contaminated with a variety of chemical wastes that get there when mineral fertilizers and pesticides are washed off from soils, with sewage and industrial effluents. Thermal and bacterial pollution occurs in water bodies, and many species of plants and animals die.
Any release of heat into the natural environment leads to a change in the temperature of its components; the lower layers of the atmosphere, soil and hydrosphere objects are especially strongly affected.
According to ecologists, thermal emissions into the environment are not yet capable of affecting the balance of the planet, but they have a significant impact on a specific territory. For example, the air temperature in major cities Usually slightly higher than outside the city, the thermal regime of rivers or lakes changes when wastewater from thermal power plants is discharged into them. The species composition of the inhabitants of these spaces is changing. Each species has its own temperature range at which the species is able to adapt. For example, trout can survive in warm water, but is not able to reproduce.
Thus, thermal discharges also have an impact on the biosphere, although this is not on a planetary scale, but is also noticeable for humans.
Temperature pollution of the soil cover results in close interaction with animals, vegetation and microbial organisms. As the soil temperature rises, the vegetation cover changes to more heat-loving species, and many microorganisms die, unable to adapt to the new conditions.
Thermal pollution of groundwater occurs due to the ingress of wastewater into aquifers. This negatively affects the quality of water, its chemical composition, thermal mode.
Thermal pollution of the environment worsens living conditions and human activities. In cities with elevated temperature in combination with high humidity, people experience frequent headaches, general malaise, horse racing blood pressure. High humidity leads to corrosion of metals, damage to sewer outlets, heating pipes, gas pipes and so much more.
Consequences of environmental pollution
It is possible to specify all the consequences of thermal pollution of the environment and highlight the main problems that require solutions:
1. Heat islands form in large cities.
2. Smog forms, air humidity increases and constant cloudiness forms in megacities.
3. Problems arise in rivers, lakes and coastal areas of seas and oceans. Due to the increase in temperature, the ecological balance is disrupted, many species of fish and aquatic plants die.
4. Chemical and physical properties water. It becomes unusable even after cleaning.
5. Living organisms of water bodies die or are in a depressed state.
6. Groundwater temperatures increase.
7. The structure of the soil and its composition are disrupted, the vegetation and microorganisms living in it are suppressed or destroyed.
Thermal pollution. Prevention and measures to prevent it
The main measure to prevent thermal pollution of the environment is a gradual abandonment of the use of fuel, a complete transition to alternative renewable energy: solar, wind and hydropower.
To protect water areas from thermal pollution in the turbine cooling system, it is necessary to construct reservoirs - coolers, from which water, after cooling, can again be used in the cooling system.
In recent decades, engineers have sought to eliminate steam turbine in thermal power plants using the magnetohydrodynamic method of converting thermal energy into electrical energy. This significantly reduces thermal pollution of the surrounding area and water bodies.
Biologists strive to identify the limits of stability of the biosphere as a whole and individual species living organisms, as well as the limits of equilibrium of biological systems.
Ecologists, in turn, study the degree of influence economic activity people on natural processes in the environment and strive to find ways to prevent negative impacts.
Protecting the environment from thermal pollution
It is customary to divide thermal pollution into planetary and local. On a planetary scale, pollution is not very large and amounts to only 0.018% of the solar radiation entering the planet, that is, within one percent. But thermal pollution has a strong impact on nature at the local level. To regulate this influence, most industrialized countries have introduced limits on thermal pollution.
As a rule, the limit is set for the regime of water bodies, since it is the seas, lakes and rivers that suffer largely from thermal pollution and receive the bulk of it.
In European countries, water bodies should not warm up more than 3 °C from their natural temperature.
In the USA, water heating in rivers should not be more than 3 °C, in lakes - 1.6 °C, in seas and oceans - 0.8 °C.
In Russia, the water temperature in reservoirs should not increase by more than 3 °C compared to the average temperature of the hottest month. In reservoirs where salmon and other cold-loving fish species live, the temperature cannot be increased by more than 5 °C, in summer no higher than 20 °C, in winter - 5 °C.
The scale of thermal pollution near large industrial centers is quite significant. So, for example, from industrial center with a population of 2 million people, with a nuclear power plant and an oil refinery, thermal pollution extends 120 km into the distance and 1 km in height.
Environmentalists suggest using thermal waste for household needs, for example:
- for irrigation of agricultural lands;
- in greenhouse farming;
- to maintain northern waters in an ice-free state;
- for the distillation of heavy oil industry products and fuel oil;
- for breeding heat-loving fish species;
- for the construction of artificial ponds, heated in winter, for wild waterfowl.
On a planetary scale, thermal pollution natural environment indirectly affects global warming. Emissions from industrial enterprises do not directly affect the rise in temperature, but lead to an increase in temperature as a result of the greenhouse effect.
To solve environmental problems and preventing them in the future, humanity must solve a number of global problems and direct all efforts to reduce air pollution and thermal pollution of the planet.
The exchange of thermal energy between the body and the environment is called heat exchange. One of the indicators of heat exchange is body temperature, which depends on two factors: the formation of heat, that is, the intensity of metabolic processes in the body, and the release of heat to the environment.
Animals whose body temperature varies depending on the temperature of the external environment are called poikilothermic, or cold-blooded. Animals with a constant body temperature are called homeothermic(warm-blooded). Consistency of temperature body is called isother Mia. She ensures independencemetabolic processes in tissues and organs from temperature fluctuations environment.
Human body temperature.
The temperature of individual parts of the human body is different. The lowest skin temperature is observed on the hands and feet, the highest - in armpit, where it is usually defined. In a healthy person temperature in this area is equal to 36-37° C. During the day, slight rises and falls in human body temperature are observed in accordance with the daily biorhythm:the minimum temperature is observed at 2- 4 hours nights, maximum - at 16-19 hours.
T temperature muscular fabrics in state of rest and work can fluctuate within 7 ° C. The temperature of the internal organs depends on the intensity of metabolic processes. Most intense metabolic processes take place in the liver, which is the “hottest” organ of the body: the temperature in the liver tissue is 38-38.5° WITH. The temperature in the rectum is 37-37.5 ° C. However, it can fluctuate within 4-5 ° C depending on the presence of feces in it, the blood supply to its mucosa and other reasons. In long-distance (marathon) runners, at the end of the competition, the temperature in the rectum can rise to 39-40 ° C.
The ability to maintain temperature at a constant level is ensured through interconnected processes - heat generation And heat release from the body into the external environment. If heat generation is equal to heat transfer, then body temperature remains constant. The process of heat formation in the body is called chemical thermoregulation, a process that removes heat from the body - physical thermoregulation.
Chemical thermoregulation. Heat metabolism in the body is closely related to energy metabolism. When organic substances are oxidized, energy is released. Part of the energy goes to ATP synthesis. This potential energy can be used by the body in its further activities.All tissues are a source of heat in the body. Blood flowing through tissue heats up.
An increase in ambient temperature causes a reflex decrease in metabolism, as a result of which heat generation in the body decreases. When the ambient temperature decreases, the intensity of metabolic processes reflexively increases and heat generation increases. To a greater extent, the increase in heat generation occurs due to increased muscle activity. Involuntary muscle contractions (trembling) are the main form of increased heat production. An increase in heat generation can occur in muscle tissue and due to a reflex increase in the intensity of metabolic processes - non-contractile muscle thermogenesis.
Physical thermoregulation. This process is carried out due to the transfer of heat to the external environment through convection (heat conduction), radiation (heat radiation) and evaporation of water.
Convection - direct transfer of heat to objects or particles of the environment adjacent to the skin. The greater the temperature difference between the surface of the body and the surrounding air, the more intense the heat transfer.
Heat transfer increases with air movement, such as wind. The intensity of heat transfer largely depends on the thermal conductivity of the environment. Heat transfer occurs faster in water than in air. Clothing reduces or even stops heat conduction.
Radiation - Heat is released from the body by infrared radiation from the surface of the body. Due to this, the body loses the bulk of heat. The intensity of heat conduction and heat radiation is largely determined by skin temperature. Heat transfer is regulated by a reflex change in the lumen of the skin vessels. As the ambient temperature rises, the arterioles and capillaries expand, and the skin becomes warm and red. This increases the processes of heat conduction and heat radiation. When the air temperature drops, the arterioles and capillaries of the skin narrow. The skin becomes pale, the amount of blood flowing through its vessels decreases. This leads to a decrease in its temperature, heat transfer decreases, and the body retains heat.
Evaporation of water from the surface of the body (2/3 moisture), as well as during breathing (1/3 moisture). Evaporation of water from the surface of the body occurs when sweat is secreted. Even in the complete absence of visible sweating, it evaporates through the skin per day. up to 0.5 l water - invisible sweating. The evaporation of 1 liter of sweat in a person weighing 75 kg can lower body temperature by 10° C.
In a state of relative rest, an adult person releases 15% of heat into the external environment through heat conduction, about 66% through heat radiation, and 19% through water evaporation.
On average, a person loses per day about 0.8 l of sweat, and with it 500 kcal of heat.
When breathing a person also releases about 0.5 liters of water every day.
At low ambient temperatures ( 15°C and below) about 90% of daily heat transfer occurs due to heat conduction and heat radiation. Under these conditions, no visible sweating occurs.
At air temperature 18-22° With heat transfer due to thermal conductivity and heat radiation decreases, butloss increasesbody heat through evaporationmoisture from the surface of the skin.At high air humidity, when water evaporation is difficult, overheating may occur.body and developthermal hit.
Low permeability to water vapor cloth prevents effective sweating and may be the reason overheating of the human body.
In hot weather countries, during long hikes, in hot in workshops people lose a large amount liquids from sweat. At the same time there is a feeling thirst that is not quenched by taking water. This due to the fact what's wrong then a large amount of mineral salts is lost. If you add salt to drinking water, that feeling of thirst will disappear And people's well-being will improve.
Heat exchange regulation centers.
Thermoregulation is carried out reflexively. Fluctuations in ambient temperature are perceived thermoreceptors. Thermoreceptors are located in large numbers in the skin, oral mucosa, and upper respiratory tract. Thermoreceptors have been discovered in internal organs, veins, as well as in some formations of the central nervous system.
Skin thermoreceptors are very sensitive to fluctuations in ambient temperature. They are excited when the temperature of the environment increases by 0.007° C and decreases by 0.012° C.
Nerve impulses arising in thermoreceptors travel through afferent nerve fibers to spinal cord. Along the pathways they reach the visual thalamus, and from them they go to the hypothalamic region and to the cerebral cortex. The result is sensations of heat or cold.
In the spinal cord are the centers of some thermoregulatory reflexes. Hypothalamus is the main reflex center of thermoregulation. The anterior parts of the hypothalamus control the mechanisms of physical thermoregulation, i.e. they are heat transfer center. Posterior sections the hypothalamus controls chemical thermoregulation and is heat generation center.
An important role in the regulation of body temperature belongs to cerebral cortex. The efferent nerves of the thermoregulation center are mainly sympathetic fibers.
Participates in the regulation of heat exchange hormonal mechanism, in particular thyroid and adrenal hormones. Thyroid hormone - thyroxine, increasing metabolism in the body, increases heat generation. The flow of thyroxine into the blood increases as the body cools. Adrenal hormone - adrenalin- enhances oxidative processes, thereby increasing heat generation. In addition, under the influence of adrenaline, vasoconstriction occurs, in particular skin vessels, due to this, heat transfer decreases.
Adaptation of the body to low ambient temperatures. When the ambient temperature decreases, a reflex excitation of the hypothalamus occurs. An increase in its activity stimulates pituitary , resulting in increased release of thyrotropin and corticotropin, which increase the activity of the thyroid gland and adrenal glands. Hormones from these glands stimulate heat production.
Thus, when cooling The body's defense mechanisms are activated, increasing metabolism, heat generation and reducing heat transfer.
Age-related features of thermoregulation. In children of the first year of life, imperfect mechanisms are observed. As a result, when the ambient temperature drops below 15° C, hypothermia occurs in the child’s body. In the first year of life, there is a decrease in heat transfer through thermal conductivity and heat radiation and an increase in heat production. However, up to 2 years of age, children remain thermolabile (body temperature rises after eating at high ambient temperatures). In children from 3 to 10 years old, the mechanisms of thermoregulation are improved, but their instability continues to persist.
In prepubertal age and during puberty (puberty), when increased growth of the body and restructuring of neurohumoral regulation of functions occur, the instability of thermoregulatory mechanisms increases.
In old age, there is a decrease in the formation of heat in the body compared to adulthood.
The problem of hardening the body. At all periods of life it is necessary to harden the body. Hardening is understood as increasing the body's resistance to adverse environmental influences and, first of all, to cooling. Hardening is achieved by using natural factors - sun, air and water. They act on the nerve endings and blood vessels of the human skin, increase the activity of the nervous system and help enhance metabolic processes. With constant exposure to natural factors, the body becomes accustomed to them. Hardening the body is effective if the following basic conditions are met: a) systematic and constant use of natural factors; b) a gradual and systematic increase in the duration and strength of their effect (hardening begins with the use of warm water, gradually lowering its temperature and increasing the time of water procedures); c) hardening with the use of stimuli contrasting in temperature (warm - cold water); d) an individual approach to hardening.
The use of natural hardening factors must be combined with physical education and sports. Good morning exercises for hardening fresh air or in a room with the window open, with obligatory exposure of a significant part of the body and subsequent water procedures (dousing, shower). Hardening is the most accessible means of improving people's health.
