The gecko is a type of lizard from the Gekkonidae family. There are 1000 species of geckos that can be found all over the world except Antarctica. Various types of geckos have developed various fixtures for survival in a wide variety of ecosystems such as: rainforests, deserts, jungles, grasslands and mountains. Geckos are often kept as pets. Leopard gecko is the most popular home pet of all geckos. Some species of geckos are threatened with complete extinction from the face of the Earth due to loss of habitats and due to the introduction of new predatory species into their habitat.
Interesting facts about these lizards:
Geckos vary in size. smallest view gecko, the pygmy gecko, reaches ¾ inch in length. The largest gecko species, Tokay geckos, reach 14 inches in length.
Geckos are usually brightly colored. Body color depends on color environment, because it plays an important role in the camouflage "camouflage" of the animal.
Geckos are nocturnal (active at night) creatures. Their eyes are adapted to low levels of light.
In addition to well-developed vision at night, geckos have an excellent sense of hearing, which helps them detect predators in a timely manner and avoid encountering them.
Because of their small size geckos are often preyed upon by snakes, birds, mammals, and some large species spiders.
Geckos eat various types fruits, flower nectar, insects and worms.
The gecko has a thick tail, which is used as a reservoir for storing fat reserves. It also helps the gecko balance while it walks and climbs trees.
Like other lizards, the gecko can drop its tail in a life-threatening situation. The tailless gecko will regenerate its missing body part after a short amount of time.
A unique feature of some gecko species is the ability to walk on smooth or even horizontal surfaces (such as ceilings) without falling. This is possible because their toes have tiny hooks that act like suction cups while walking.
Teflon is the only material that the gecko cannot stick to (using its "suckers") and walk without slipping.
The flying gecko is the only gecko species that can fly (glide through the air). This animal has webbed feet and a tail, and a wide flap of skin that acts like a parachute as the gecko moves from tree to tree.
Unlike other reptiles, these creatures are vocal and are capable of producing various sounds that are used in communication. They make barking, chirping or clicking noises during mating or when defending their territory.
The gecko mates a couple of times during the year. The female produces two eggs. She lays her eggs under leaves a few weeks after mating and abandons them. She doesn't care about eggs. Some eggs are soft, but their shell gradually hardens when exposed to air.
Geckos have a fairly long lifespan. The Lecard gecko can live over 20 years in captivity. Other species live from 8 to 10 years.
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The process of lowering body temperature is called cooling. Distinguish natural and artificial cooling.
Natural cooling allows the body to cool down to ambient temperature. Such cooling is provided by cold water or air.
For cooling down to a temperature lower than the ambient temperature, artificial cooling, which can be carried out using any physical process associated with the removal of heat.
Artificial cooling is used in the processes of absorption, crystallization, gas separation, freeze drying and air conditioning.
With the help of refrigeration mixtures, quite low temperatures can be obtained. A mixture of ice and CaCl 2 (up to 30%) makes it possible to reach a temperature of -55 °C. However, cooling in this way requires a lot of ice and salt, so its use is limited.
In modern refrigeration machines ah, the property of a number of low-boiling liquefied gases(ammonia, freons, carbon dioxide, etc.) absorb from the environment during evaporation a large number of warmth.
Artificial refrigeration can be divided into moderate(up to -100 °C) and deep(to a lower temperature).
In industry, deep cooling is used to liquefy separated gas-vapor and gas mixtures. The gases obtained in this way are widely used in the chemical industry: nitrogen - for the production of chemical fertilizers, oxygen, methane and ethylene - for the production of mineral acids, etc.
In artificial cold installations, the necessary decrease in the temperature of the working fluid is carried out. By aggregate state of the working fluid refrigeration units
they are divided into gas, gas-liquid, vapor-liquid and adsorption (using a solid phase).
Artificial cooling in most cases is carried out by two methods:
Evaporation of low-boiling liquids;
Expansion of various pre-compressed gases by throttling or expanding.
During the evaporation of low-boiling liquids, the latter are cooled due to a decrease in internal energy.
Throttling is a process of expansion of gas as it passes through a narrowing device, resulting in a decrease in gas pressure. The energy required to expand the gas during throttling, when there is no heat input from the outside, can only be obtained from the internal energy of the gas itself. Throttle effect(Joule-Thomson effect) is a change in gas temperature during throttling in the absence of heat exchange with the environment.
Expanding- this is the expansion of gas in an expansion machine - expander. By design, this unit is similar to a reciprocating compressor or turbocharger. During expansion, the gas is cooled due to a decrease in internal energy and external work.
In HF systems, the air is heated in heating sections made in the form of multi-pass heaters made of horizontal steel pipes finned with steel tape. Typical sections are assembled from one-two and three-row basic heat exchangers.
For the first heating along the air flow, at least 2 sections are usually installed. The heat carrier can be water with a temperature of up to 150 0 C and steam with a pressure of not more than 0.6 MPa.
If the heat carrier is water, then to increase the speed of its movement in the heat exchanger tubes and the heat transfer coefficient, the heating sections are connected in series.
Parallel connection is used only in cases of insufficient pressure in the heating network to overcome the increase in hydraulic resistance of heat exchangers connected in series.
If the heat carrier is steam, then the heating sections are connected to the steam condensate pipelines in parallel. The maximum allowable steam pressure according to the strength conditions of heat exchangers is 0.6 MPa.
For sections of the second heating of local or zonal air heaters, water with a constant temperature in the supply line (usually 60-70 0 С) is used as a heat carrier. The estimated water temperature difference is taken as 15-25 0 С.
They should not be directly connected to heating networks, because. the required heat output of heaters, as a rule, does not depend on the outdoor temperature, i.e. is not connected with the temperature schedule, according to which the temperature of the network water changes. A supply of variable temperature water would significantly degrade the operation of the automatic control system.
The heat transfer of the heaters of the second heating is regulated by an automatic valve that changes the amount of water of constant temperature supplied to the heater.
To obtain water with a constant temperature according to closed scheme mixing plants with intermediate heat exchangers are used.
33.2 Refrigeration of air conditioners.
The coolant for SCR is usually water obtained from refrigeration plants, and in individual cases- from natural sources. The choice of a cooling system depends on the method of obtaining cold water, the distance of consumers from the source of cold, the type of evaporator, and also on the method of connecting the air cooler to the coolant.
33.3. Cold sources for air conditioning systems.
When designing ACS in areas with a dry and hot climate, direct, indirect or combined (two-stage) evaporative air cooling should be taken if these methods provide the specified air parameters.
In most cases, natural or artificial sources of cold are necessary for the operation of the SCR. Natural sources include cold water from artesian wells or mountain rivers. The use of these sources is economically feasible in cases where the temperature of the water serving as a coolant makes it possible to obtain the necessary air parameters when the water is heated by at least 3 0 C.
In some cases, for small HF systems that consume up to 180 thousand W of cold, ice prepared by freezing water in coils or obtained from reservoirs can be used. Direct contact between ice from riots or reservoirs and the air supplied to the room is not allowed for sanitary and hygienic reasons. Therefore, it is necessary to cool the water circulating in the surface air-to-water heat exchanger with ice.
The most common cold is obtained from artificial sources - refrigeration machines. Machine cooling is a method of obtaining cold by changing the state of aggregation of the refrigerant (boiling it at low temperatures ah with removal from the cooling medium, the heat of vaporization necessary for this).
For the subsequent condensation of refrigerant vapors, it is necessary to first increase their pressure and temperature. According to the method of increasing the temperature of vapors and pressure before their condensation, the following types of refrigeration machines are distinguished:
compression - with vapor compression by a compressor at a cost mechanical energy;
absorption - with the absorption of vapors by the appropriate absorbent and their release by evaporating the solution with the expenditure of thermal energy;
ejector - in which two cycles are simultaneously carried out: direct - with the transformation of the supplied thermal energy into mechanical and reverse - using mechanical energy to produce cold.
Compressor refrigeration units are the main consumers of electricity at enterprises for the processing and storage of perishable food products, which requires finding reserves to save energy resources. Since most of the territory of our country is characterized by long winters with low air temperatures, a very promising direction for saving energy resources is wide application natural cold. Let's note some directions of use of natural cold.
The simplest and most common way is to directly supply cold air to the cooling or food storage chambers when the outside air temperature is equal to or lower than that required in the chambers. Openings are made in the outer walls for air intake with a fan and its release through the petal check valve(Fig. 94). Air is distributed in the chamber through an air duct with adjustable windows, which are automatically closed by dampers when the fan stops. The temperature in the chamber is maintained by a two-position temperature switch that turns on or off the fan. When placing unpackaged products in the chamber, it is necessary to install filters for cleaning the air from dust and microorganisms (for example, LAIK SP-6/15 or LAIK SP-6/15A) at the fan suction. It has been found that in areas with relative humidity air of 85% and higher in chambers with unpackaged products, you can use outside air without humidification. In other cases, an air humidification system is provided. Given the seasonal nature of the use of natural cold, it is advisable to combine equipment for natural and artificial cooling in the chambers. When working with artificial cooling in summer, the openings in the fences are closed with heat-insulated hatches. For the main areas of mass cultivation of potatoes and vegetables, the storage period coincides with the period of stable standing of sufficiently low outdoor temperatures. In this regard, the method of storing products in bulk under conditions of active ventilation using natural cold is becoming widespread. Outside air is supplied by a fan to a variable-section air duct located under the perforated storage floor (Fig. 95). The supplied air is humidified, passes through the products from the bottom up and is removed from the storage through the deflector. The fan and humidifier are automatically switched on by a signal from sensors of differentiated temperature controllers at an outdoor air temperature of 2 ... 3 ° C below the temperature that the mass of the product has. Air humidification is carried out with water vapor or water spray. The optimum values of air humidity before entering the product are 90% or more, and specific consumption air per 1 ton of products - more than 100 m 3 / h.
In the dairy industry, cooling of the refrigerant using external heat exchangers or in cooling towers is also widespread. Standard air coolers with a high degree of finning and powerful fans (for example, VOG-230) installed outdoors (on the roof of the compressor shop) can be used as heat exchangers. Considering the limited operating time of heat exchangers using natural cold, general scheme circulation of the coolant (water, brines) must be mobile and have switching based on different modes of operation: cooling of the coolant only by external heat exchangers; teamwork outdoor units and evaporators refrigeration unit; cooling of the refrigerant only in the evaporators of the refrigeration unit. AT winter time ice water can be obtained in cooling towers with full or partial shutdown refrigeration equipment. On fig. 96 shows the connection diagram of the cooling tower for cooling the coolant, operating in three modes: cold accumulation at night, coolant circulation circuit (cooling tower - tank - pump); cooling technological equipment accumulated cold and subcooling of the coolant in the cooling tower; coolant cooling in the evaporator. The parameter by which one or another cooling method is selected is the temperature of the coolant entering the technological apparatus.
Standard GPV type cooling towers are used to produce water with a temperature of 1…4°C at outdoor temperature air -5 ° C and below. The disadvantage of film cooling towers is the formation of ice on the structural elements, which leads to a sharp decrease in the amount of circulating air and. rise in chilled water temperature. This shortcoming is eliminated in the Y10-OU0 installation for natural cooling of circulating water in winter. It provides cooling of water from 10 to 5±1°C at an ambient temperature of -5°C and below. During the summer period, the installation performs the functions of a cooling tower in the circulating water supply system. A defrosting system is provided for periodic de-icing. The cooling tower is mounted in an open area with free drain from the pallet to the accumulation unit, while the difference in elevations between drain pipe sump and the water level in the accumulation unit is at least 1 m.
Deserves special attention a method of accumulating winter cold by freezing up ice piles, which allows a significant part of the summer time to do without machine cooling, which saves energy resources, lubricants, and increases the service life of equipment.
Another reserve for energy savings due to natural cold is the use of air condensers, which can be used as precondensers in combination with shell-and-tube and evaporative condensers. AT winter period air precondensers can take over all heat load from the installation, while the condensing temperature can be arbitrarily low, which leads to energy savings for the production of cold. The use of natural cold for cooling is an inexhaustible source of effective technical solutions, and by combining two or more types of free cooling, sufficiently high technical and economic indicators can be achieved.
In our imagination, the very concept of "thermal physics" is usually associated with the production of heat, the efficiency of fuel combustion, and energy production. It is clear that for the inhabitants of Siberia, the heat costs more than important place than cold. Nevertheless, the production of cold is also one of the urgent tasks for scientists working in the field of thermal physics. And the most remarkable - for the production of cold, they propose to attract all the same heat!
Why it is necessary to produce cold, I think many of us understand. Cold is needed to store food, to create a favorable microclimate in the premises, for certain production processes. Each of us has a refrigerator in the house, all normal public buildings are equipped with air conditioners. Imagine a cafe, shop, hotel or business center without air conditioning, and you will understand that the cooling system is no less important than the heating system, even when it comes to Siberia. In winter, of course, we need warmth. In the summer? Summer in our area also sometimes breaks records for heat. And about southern countries and there is nothing to say.
In short, modern comfort parameters and the need for food storage somehow require the production of cold. And I must say that from year to year the need for artificial cold increases both in Russia and abroad.
How is cold produced? Today, there are two main types of refrigeration machines - vapor compression refrigeration machines and lithium bromide absorption machines. The first type is well known to us - this is how our household refrigerators operating from the mains. The operation of such machines is based on a change in the state of aggregation of the refrigerant - freon (freon) - under the influence of mechanical energy. For the transformation electrical energy in the mechanical one, as we know, compressors are used.
As for refrigerating machines of the second type, their operation is based on the chemical interaction of the substances of the working pair - the absorbent and refrigerant, and the change in the state of aggregation of the refrigerant under the influence of thermal energy. In other words, for their work, such machines use heat.
And this is where we come to the very important point concerning refrigerating machines of the second type. So, if in the first case we need to spend electricity to produce cold, then in the second case we can quite use the “excess” heat, which under other circumstances very often flies into the chimney (literally). Of course, ordinary energy resources - gas or fuel oil, can also serve as heating sources for such machines, but you can also use steam from boiler houses, intermediate withdrawals from thermal power plants, hot water, flue gases or waste steam from industries. In other words, the heat emitted into the atmosphere, thanks to absorption machines, is quite suitable for the production of cold. That is, in this case there is no need to spend valuable energy resources - it is enough to use the "surplus" heat prudently, of which there is especially much in the summer, when it makes sense to cool the premises.
It must be said that efficiency is one of the most important advantages of absorption lithium bromide refrigeration machines over vapor compression ones. As we understand, in the conditions of constant growth of electricity tariffs, this becomes especially important.
Another important advantage is environmental friendliness associated with the absence of freons (freons), the use of which is limited in many countries in accordance with the Montreal and Kyoto protocols. Lithium bromide machines are not subject to such restrictions. Used here as an absorbent water solution lithium bromide is non-volatile and non-toxic, belonging to low-hazard substances.
Another advantage is related to the low noise level during the robot. You can also mention the ease of maintenance, long service life and fire and explosion safety.
Due to these advantages, such machines are able to find wide application both in everyday life and in economic activity. The range of their application is quite wide - from metallurgical enterprises, nuclear power plants, petrochemical plants - to greenhouses, apartment buildings, shopping centers and others public buildings where you want to create a comfortable microclimate. And most importantly (we emphasize again), this comfort can be achieved with minimal cost electricity!
Are such machines being developed in our country? Yes, they are developing! They even produce. Just such a sample, developed by specialists from the Institute of Thermal Physics of the Siberian Branch of the Russian Academy of Sciences, is produced in Kemerovo region. Moreover, it is important to note that domestic cars have some advantages in comparison with foreign ones. For example, they, as they say, “adjust” to a specific consumer. Our experts use a flexible design system and assemble on site. Moreover, they can offer customers a very high power– up to 5.3 MW. In addition, given the complex realities, the developers have provided - especially for emergency cases - duplication automatic system management manual system(using buttons).
However, this individual approach also revealed its own weak spots. We are talking about market competition with foreign serial samples (coming mainly from China). So, foreign manufacturers, "stamping" such machines on the conveyor, are able to resort to dumping. And if we talk about the Chinese, then they can generally count on state support, carrying out the conquest Russian market. The state is not going to help our producers (and will not).
So for the time being, we are not talking about mass production of domestic cars. This, of course, is only in the plans. Therefore, at present (which is very important), the specialists of the IT SB RAS are perfecting their brainchild, adapting to the needs of each consumer as much as possible. Perhaps there is a plus in this individual approach. It is possible that such a manual assembly» will someday become an indicator High Quality and will be highly appreciated in the market.
