Air Conditioning (often referred to as air conditioning, A/C, or air con) is the process of removing heat and humidity from the interior of the occupied space, to improve occupant comfort. Air conditioning can be used in domestic and commercial environments. This process is most often used to achieve a more comfortable interior environment, usually for humans and animals; however, air conditioning is also used to cool/humidify rooms filled with heat-generating electronic devices, such as computer servers, power amplifiers, and even to display and store artwork.
Air conditioners often use fans to distribute air conditioning to occupied spaces such as buildings or cars to improve thermal comfort and indoor air quality. Air-cooled AC units range from small units that can cool small bedrooms, which can be carried by one adult, to large units mounted on the roof of an office tower that can cool the entire building. Cooling is usually achieved through the cooling cycle, but sometimes free evaporation or cooling is used. Air conditioning systems can also be made based on desiccants (chemicals that remove moisture from the air) and subterraneous pipes that can distribute refrigerants heated to the ground for cooling.
In the most general sense, air conditioning can refer to any form of technology that changes air conditions (heating, cooling, (de-) humidification, cleaning, ventilation, or air movement). In general use, though, "AC" refers to systems that cool the air. In construction, complete heating, ventilation and air conditioning systems are referred to as HVAC.
Video Air conditioning
History
Evaporative cooling
Since prehistoric times, snow and ice are used for cooling. The attempt to harvest ice during the winter and save for use in the summer became popular towards the end of the 17th century. This practice is replaced by mechanical ice machines.
The basic concept behind the air conditioner is said to have been applied in ancient Egypt, where the reeds are hung in windows and dampened with water dripping. Evaporation of water cools the air blowing through the windows. This process also makes the air more humid, which can be useful in dry desert climates. In Ancient Rome, water from aqueduct was circulated through the walls of certain houses to cool them down. Another technique in Persia in the Middle Ages involved the use of water tanks and wind towers to cool buildings during the summer.
Mechanical engineer and second-century mechanical inventor, Ding Huan of the Han Dynasty created a rotary fan for air conditioning, with seven wheels of 3 m (10 ft) in diameter and manually powered by prisoners at the time. In 747, Emperor Xuanzong (r.712-762) of the Tang Dynasty (618-907) had the Cool Hall ( Liang Tian ) built in the imperial palace, which > Tang Yulin describes having a water-powered fan wheel for air conditioning and a rising flow of water jets from a fountain. During the next Song Dynasty (960-1279), a written source mentions the AC cooling fan is even more widely used.
In the 17th century, Dutch inventor Cornelis Drebbel demonstrated "Turning Winter into Winter" as an early form of modern air conditioner for James I of England by adding salt to water.
Development of mechanical cooling
Modern air conditioning emerged from the advancement of chemistry during the 19th century, and the first large-scale air conditioning was invented and used in 1902 by the American inventor Willis Carrier. The introduction of residential air conditioners in the 1920s helped enable a major migration to the Sun Belt in the United States.
In 1758, Benjamin Franklin and John Hadley, a professor of chemistry at Cambridge University, conducted an experiment to explore the principle of evaporation as a means of cooling objects quickly. Franklin and Hadley assert that evaporation of a highly volatile liquid (such as alcohol and ether) can be used to lower the temperature of an object through the freezing point of water. They conducted experiments with bulb mercury thermometers as their object and with a bellows used to speed up evaporation. They lower the temperature of the thermometer ball to -14 ° C (7 ° F) while the temperature is about 18 ° C (64 ° F). Franklin notes that, as soon as they pass through the freezing point of water 0 ° C (32 ° F), a thin layer of ice forms on the surface of the thermometer ball and that ice mass is about 6 mm ( 1 / 4 on) thick when they stop the experiment after reaching -14 Â ° C (7 Â ° F). Franklin concluded: "From this experiment one can see the possibility of freezing a man to death on a warm summer day."
In 1820, British scientist and inventor Michael Faraday discovered that compressing and liquefying ammonia could cool the air when liquid ammonia was allowed to evaporate. In 1842, Florida doctor John Gorrie used a compressor technology to make ice, which he used to cool the air for his patients at his hospital in Apalachicola, Florida. He hopes to finally use an ice machine to regulate the temperature of the building. He even imagined a centralized air conditioner that could cool the whole city. Although the prototype was leaking and performing irregularly, Gorrie was granted a patent in 1851 for his ice-making machine. Despite the process of increasing artificial ice production, his hopes for success disappeared shortly afterwards when his main financial supporter died and Gorrie did not get the money needed to develop the machine. According to his biographer, Vivian M. Sherlock, he blames the "Ice King", Frederic Tudor, for his failure, suspecting that Tudor has launched a dirty campaign against his invention. Dr. Gorrie died in 1855, and the dream of a general air conditioner went on for 50 years.
The first mechanical ice-maker machine owned by James Harrison began operations in 1851 on the banks of the Barwon River at Rocky Point in Geelong, Australia. The first commercial ice-maker machine followed the year 1853, and its patent for the eter vapor compression cooling system was given in 1855. The new system used a compressor to force the cooling gas through the condenser, where it cooled and melted. The liquid gas is then circulated through the cooling coil and evaporates again, cooling the surrounding system. The engine produces 3,000 kilograms (6,600 pounds) of ice per day.
Although Harrison had the commercial success of setting up a second ice company in Sydney in 1860, he later entered into a debate about how to compete against American gains from the sale of ice-cooled beef to England. He writes: "Fresh meat is frozen and packed as if for a journey, so that the cooling process can be continued for any required period", and in 1873 prepared a sailing vessel Norfolk for the delivery of experimental beef to England. His choice of cold space systems rather than installing a cooling system on the ship itself proved to be a disaster when ice was consumed faster than expected.
Electrical AC
In 1902, the first modern electric air conditioning unit was created by Willis Carrier in Buffalo, New York. After graduating from Cornell University, Carrier got a job at the Buffalo Forge Company. While there, he began experimenting with air conditioning as a way to solve application problems for Sackett-Wilhelms Lithographing and Publishing Company in Brooklyn, New York. The first air conditioner, designed and built in Buffalo by Carrier, began work on July 17, 1902.
Designed to improve the control of the manufacturing process at the printing plant, Carrier invention not only controls temperature but also humidity. Carrier uses his knowledge of heating objects with steam and reversing the process. Instead of sending the air through the heat coil, it sends it through a cold coil (filled with cold water). The air is cooled, and thus the amount of water vapor in the air can be controlled, which in turn makes the humidity in the room can be controlled. Controlled temperature and humidity helps maintain consistent ink dimensions and ink alignment. Later, Carrier technology was applied to improve workplace productivity, and the American Carrier Air Conditioner Company was formed to meet increased demand. Over time, air conditioning began to be used to improve comfort in homes and cars as well. Residential sales increased dramatically in the 1950s.
In 1906, Stuart W. Cramer of Charlotte was exploring ways to increase air humidity in his textile plant. Cramer coined the term "air conditioning", using it in his patent claims that year as analog for "water conditioning", then a well-known process for making textiles easier to process. It combines moisture with ventilation for "conditions" and changes the air in the factories, controlling the indispensable moisture in the textile mill. Willis Carrier adopted the term and put it in his company name.
Soon, the first private home that had air conditioning built in Minneapolis in 1914, owned by Charles Gates. Realizing that air conditioning will one day become a standard feature of private homes, especially in areas with warmer climates, David St. Pierre DuBose (1898-1994) designed a plumbing and ventilation network for his home Meadowmont , all shrouded behind an elaborate and attractive Georgian open mold. The building is believed to be one of the first private homes in the United States equipped for central air conditioning.
In 1945, Robert Sherman of Lynn, Massachusetts invented a portable air conditioner in a cooled, heated, humidified, dehumidified, and air-filtered window.
Development cooling
The first air conditioner and refrigerator use toxic or flammable gas, such as ammonia, methyl chloride, or propane, which can cause fatal accidents when leaking. Thomas Midgley, Jr. created the first non-flammable and non-toxic chlorofluorocarbon, Freon , in 1928. This name is a trademark owned by DuPont for every chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), or hydrofluorocarbon refrigerant (HFC). The names of refrigerants include numbers showing the molecular composition (eg, R-11, R-12, R-22, R-134A). The most widely used mixture in home cooling and direct build cooling convenience is HCFC known as chlorodifluoromethane (R-22).
Dichlorodifluoromethane (R-12) was the most commonly used mixture in cars in the US until 1994, when most of the designs turned into R-134A due to the ozone-depleting potential of R-12. R-11 and R-12 are no longer manufactured in the U.S. for this type of application, so the only source for repairing the air conditioner is cleaning and purifying gas recovered from other AC systems. Some non-ozone-depleting refrigerants have been developed as an alternative, including R-410A. It was first used commercially by Carrier Corp. with the brand name Puron .
Modern refrigerants have been developed to be safer for the environment than many of the early chlorofluorocarbon-based refrigerators used in the early and mid twentieth century. These include HCFC (R-22, as used in most homes in the US before 2011) and HFC (R-134a, used in most cars) has replaced most CFC usage. HCFC, in turn, should have been in the process of being removed under the Montreal Protocol and replaced by HFC like R-410A, which has no chlorine. HFC, however, contributes to the problem of climate change. In addition, policy and political influence by corporate executives resist change. Corporations insist that there is no alternative to HFC. The environmental organization Greenpeace provided funding to East German refrigerator companies to examine safe alternatives to ozone coolants and climate in 1992. The company developed a mixture of isopentane and isobutane hydrocarbons, but as a condition of contracts Greenpeace could not patent technology, which led to widespread adoption by other companies. Their first marketing activists in Germany caused companies like Whirlpool, Bosch, and then LG and others to combine technology across Europe, then Asia, even though company executives refused in Latin America, arriving in Argentina produced by domestic companies in 2003, and finally with the giant Bosch production in Brazil in 2004.
In 1995, Germany made the refrigerator CFC illegal. DuPont and other companies are blocking refrigerants in the US with the US. A.P.A., dismissive of the approach as "the German technology." However, in 2004, Greenpeace worked with multinational companies such as Coca-Cola and Unilever, and later Pepsico and others, to create a corporate coalition called Refrigerants Naturally !. Then, four years later, Ben & amp; Jerry's from Unilever and General Electric are taking steps to support US production and usage. In 2011, E.P.A. decided to support ozone refrigerant and a safe climate for US manufacturing.
Maps Air conditioning
Principle of operation
Cooling cycle
In the cooling cycle, heat is transported from a cooler location to a hotter area. Since heat naturally flows in the opposite direction, it takes work to accomplish this. Refrigerators are an example of such a system, as it transports heat out of the interior and into its environment. Refrigerant is used as a medium that absorbs and removes heat from the chill to be cooled and then releases it elsewhere.
The circulating refrigerant vapor enters the compressor, where the pressure and temperature increase. Hot and compressed refrigerant vapor is now at a temperature and pressure that can be condensed and flowed through the condenser. Here it is cooled by air flowing through the condenser coil and condensed into liquid. Thus, circulating refrigerants transfer heat from the system and heat is carried by air. This heat removal can be greatly enlarged by pouring water over a condenser roll, making it cooler when it touches the expansion valve.
The condensed, pressurized, and still relatively hot liquid refrigerant is then flowed through the expansion valve (often no more than the pinhole in the copper tube system) where it experiences a sudden drop in pressure. Pressure reduction results in flash evaporation from the liquid refrigerant part, greatly lowering the temperature. AC aircraft use turbines for cooling, more efficient but more complex. The cold refrigerant is then flowed through the evaporator. A fan blows the warm interior air (to be cooled) in the evaporator, causing the liquid part of the cold refrigerant mixture to evaporate as well, further lowering the temperature. The warm air is cooled and pumped by the exhaust fan/blower into the room. To complete the cooling cycle, the refrigerant vapor is flown back to the compressor. In order for the process to have efficiency, the cooling/cooling part of the system must be separated by some type of physical barrier from the heating/condensing section, and each part must have its own fan to circulate its own "type". air (either hot air or cold air).
Modern air conditioning systems are not designed to draw air into the room from the outside, they simply redistribute the cooler air inside. Since this inner air always has a certain amount of moisture suspended in it, the cooling part of the process always causes ambient warm water vapor to condense on the cooling coil and trickle down to the catch tray at the bottom of the unit from which it must then be routed outwards, usually through sinkhole. Since this moisture does not contain dissolved minerals in it, it will not cause mineral buildup in the coils. This will happen even if the ambient humidity level is low. If ice begins to form on the evaporating fins, it will reduce circulation efficiency and lead to more ice growth, etc. A clean and strong circulation fan can help prevent this, as it increases the cold temperature of the target from the thermostat unit to the point that the compressor is allowed to turn off occasionally. Failed thermistor can also cause this problem. Refrigerators without ice-melting cycles may have the same problem. Dust can also cause the fins to start blocking airflow with unwanted results: ice.
By running the AC compressor in the opposite direction, the overall effect can be completely reversed and the indoor area will be hot instead of cooled (see heat pump). The engineering of the physical and thermodynamic properties of a gas-vapor mixture is called psychrometric.
Heat pump unit
The heat pump is an air conditioner where the cooling cycle can be reversed, resulting in heating instead of cooling in the indoor environment. They are also often referred to as "reverse cycle air coolers". The heat pump is significantly more energy efficient than heating the electrical resistance. Some homeowners choose to have a heat pump system installed as a central air conditioning feature. When the heat pump is in heating mode, the indoor evaporator coil plays a role and becomes a condenser coil, generating heat. The outer condenser unit also acts as an evaporator, and removes cold air (colder than outdoor air).
Air-borne heating pumps are more popular in milder winter climates where temperatures are often in the 40-55 Â ° F (4-13 Â ° C) range, as heat pumps become inefficient in the more extreme cold. This is because ice is formed on the outdoor unit heat exchanger coil, which blocks the airflow above the coil. To compensate for this, the heat pump system must temporarily switch back to the usual AC mode to replace the outer evaporator coil back into the condenser coil, thereby heating and melting the ice. A heat pump system will therefore have a form of electrical resistance heating in indoor air lanes that is activated only in this mode to compensate for temporary indoor air cooling, which will not be comfortable in winter.
The icing problem becomes much more severe with lower outside temperatures, so heat pumps are generally installed together with more conventional heating forms, such as natural gas or oil furnaces, which are used instead of heat pumps during louder winter temperatures. In this case, the heat pump is used efficiently during lighter temperatures, and the system is diverted to a conventional heat source when the outside temperature is lower.
The absorption heat pump is a type of airborne heat pump, but they do not rely on electricity to power it. In contrast, gas, solar power, or hot water are used as the main power source. The absorption pump dissolves the ammonia gas in water, which releases heat. Furthermore, the water mixture and ammonia are depressurized to induce boiling, and the ammonia is boiled, which absorbs heat from the outside air.
Some of the more expensive fixed window air conditioning units have the actual heat pump function. However, window units may only have electrical resistance heaters.
Evaporative cooling
In a very dry climate, evaporative coolers, sometimes referred to as swamp coolers or desert coolers, are popular for improving coolness during hot weather. An evaporative cooler is a device that pulls the outside air through a wet pad, like a large sponge soaked in water. The reasonable heat of the incoming air, as measured by dry ball thermometers, is reduced. The temperature of the incoming air is reduced, but also more moist, so the total heat (sensible heat plus latent heat) is unchanged. Some plausible heat from the incoming air is converted into latent heat by evaporation of water in wet cooling pads. If the incoming air is dry enough, the result can be very large.
Evaporative coolers tend to feel as though they are not working at high humidity, when there is not much dry air that coolers can use to make the air as cool as possible for the occupants living. Unlike other types of air conditioners, evaporative coolers rely on the outside air to be channeled through cooling pads cooling the air before reaching the interior of the house through the airway system; This cooled outer air should be allowed to encourage warmer air inside the house through drain holes such as open doors or windows. This cooler is cheaper and mechanically simple to understand and maintain.
Free cooling
Air conditioning can also be provided by a process called free cooling which uses a pump to circulate the coolant (usually water or glycol mixture) from a cold source, which in turn acts as a heat sink for energy released from the cooled chamber.. Common storage media are deep aquifers or underground natural rock mass accessed via a group of small diameter drill holes, fitted with heat exchangers. Some systems with small storage capacity are hybrid systems, using free cooling at the beginning of the cooling season, and then using heat pumps to cool the circulation from storage. Heat pumps are added because storage temperatures gradually increase during the cooling season, thereby decreasing their effectiveness.
The free cooling system can have very high efficiency, and sometimes combined with seasonal thermal energy storage (STES) so winter can be used for summer air conditioning. Cooling system and hybrid free is mature technology.
Humidity control
Because humans sweat to provide natural cooling by the evaporation of sweat from the skin, the drier air (up to a point) increases the comfort provided. Comfort air conditioning is designed to create a 50% to 60% relative humidity in the occupied space.
Dehumidification and cooling
AC cooling equipment usually reduces the absolute moisture of air processed by the system. The relatively cold coil of evaporator (below dewpoint) condenses water vapor from processed air, as cold drinks will condense water on the outside of the glass. Therefore, moisture is removed from the cooled air and the relative humidity in the room is lowered. Water is usually delivered to the drain or it may drip to the ground outside. The heat is rejected by the condenser that is located outside the room to be cooled.
Program Dehumidification
In most modern AC systems there is a cycle of dehumidification; the compressor turns on and the fan is slowed down as much as possible (lowest speed under normal conditions). This reduces the evaporator temperature and therefore condenses more water than if it has a high fan speed. To help reduce the temperature drop when the temperature falls below the threshold, both the fan and the compressor die, this will stop the humidity on the evaporator being blown back into the room. As the temperature rises again the compressor comes and the fan returns to a low speed. But sometimes the fan will stay on and the compressor goes to melt the ice produced (hence why the program does not work in cold conditions).
Type AC Inverter uses a temperature sensor in the coil (usually used for heat pump operation where it regulates fan speed according to how warm the evaporator is) to adjust the speed of the compressor to keep the evaporator as cold as possible, when the evaporator is too cold the compressor is slowed or stopped with an indoor fan.
Dehumidifier
A special air conditioner used only for dehumidifying is called dehumidifier. It also uses a cooling cycle, but is different from the standard AC that is the evaporator and the condenser is placed in the same air path. The standard AC transfers heat energy outdoors because the condenser coil releases heat outside. However, since all dehumidifier components are in the same space , no heat energy is eliminated. In contrast, the electric power consumed by the dehumidifier remains in the room as heat, so the room is actually heated, just as the electric heater draws the same amount of power.
In addition, if the water is condensed indoors, the amount of heat previously required to vaporize the water is also released back into the room (latent heat of evaporation). The dehumidification process is the opposite of adding water to a room with an evaporative coolant, and instead releasing heat. Therefore, the dehumidifier in the room will always warm the room and reduce the relative humidity indirectly, and reduce the humidity directly by condensing and removing water.
Inside the unit, air passes through the first evaporator coil, and is cooled and dehydrated. The now dehumidified cold air then passes through the condenser coil where it is warmed again. Then air is released back into the room. This unit produces warm, dehumidified air and can usually be placed freely in a conditioned environment.
Dehumidifiers are commonly used in cold and humid climates to prevent mold growth in the room, especially in the basement. They are also used to protect sensitive equipment from the excessive effects of excess moisture in tropical countries.
Energy transfer
In a closed thermodynamic system, any power dissipated into a system maintained at a regulated temperature (which is a standard operating mode for modern air conditioning) requires that the rate of energy loss by the AC increase. This increase has the effect that, for each unit of energy input into the system (say to light the bulb in a closed system), the AC eliminates that energy. To do so, AC should increase power consumption by the inverse of "efficiency" (performance coefficient) times the amount of power dissipated into the system. For example, assume that inside a closed system 100W heating element is activated, and AC has a performance coefficient of 200%. The AC power consumption will increase by 50 W to compensate for this, thus making the 100 W heater element cost 150 W total.
Especially for air conditioners to operate on "efficiency" significantly greater than 100%. However, it can be noted that the input electrical energy has a higher thermodynamic quality (lower entropy) than the output of heat energy (heat energy).
AC power equipment in the US is often described in terms of "tons of refrigeration". One ton of refrigeration is roughly equal to the cooling power of a short ton (2000 pounds or 907 kilograms) of melting ice in a 24-hour period. This value is defined as 12,000 BTU per hour, or 3517 watts. The central air-conditioning system is usually from 1 to 5 tons (3 to 20 kilowatts (kW)) in capacity.
Summer energy efficiency ratio
For residential homes, some countries set minimum requirements for energy efficiency. In the United States, AC efficiency is often (but not always) assessed by the seasonal energy efficiency ratio (SIER) . The higher the SEER rating, the more efficient the energy is AC. The SEER rating is the BTU of cooling output during the normal yearly usage divided by the total input of electrical energy in watts of hours (W Â · h) during the same period.
- SEER = BTU ÃÆ' Â · (W Â · h)
this can also be rewritten as:
- SIER = (BTU/h) ÃÆ' Â · W , where "W" is the average electric power in Watt, and (BTU/h) is the measured cooling power.
For example, 5000 BTU/hour air conditioning unit, with SIER 10, will consume an average power of 5000/10 = 500 Watt.
Electrical energy consumed per year can be calculated as average power multiplied by the annual operating time:
- 500 W ÃÆ'â € "1000 h = 500,000 WÃ, Â · h = 500 kWh
Assume 1000 hours of operation during a typical cooling season (ie, 8 hours per day for 125 days per year).
Another method that produces the same result, is calculate the total annual cooling output:
- 5000 BTU/hour ÃÆ'â € "1,000 hours = 5,000,000 BTU
Then, for SIER 10, annual electrical energy usage is:
- 5,000,000 BTU ÃÆ' Â · 10 = 500,000 WÃ, Â · h = 500 kWh
SIER is related to the performance coefficient (COP) commonly used in thermodynamics and also for the Energy Efficiency Ratio (EER). EER is the efficiency rating for equipment on a particular pair of external and internal temperatures, while SIER is calculated across the external temperature range (ie, temperature distribution for the geographic location of the SIER test). SIER is unusual because it consists of an Imperial unit divided by an SI unit. COP is the ratio of the same unit of energy metric (joule) in both the numerator and the denominator. They cancel, leaving quantity without dimension. The formula for approximate conversions between SIER and EER or COP is available.
- (1) Ã, SIER = EER ÃÆ' Â · 0,9
- (2) SIER = COP ÃÆ'â € "3,792
- (3) Ã, EER = COP ÃÆ'â € "3,413
From equation (2) above, SEER 13 is equivalent to COP 3.43, which means 3.43 units of heat energy are pumped per unit of energy work.
The United States now requires that the housing system produced in 2006 have a minimum SIER rating of 13 (although the box-window system is excluded from this law, so their SIER is still about 10).
Installation type
Unit window and packet terminal
The window AC unit is installed in the open window. The interior air is cooled when the fan blows it over the evaporator. On the outside, heat drawn from the interior disappears into the environment as the second fan blows outside the air above the condenser. Large houses or buildings may have several such units, allowing each room to be cooled separately.
In 1971, General Electric introduced portable in-window air conditioners designed for comfort and portability.
The air conditioning terminal system (PTAC) packaged is also known as a split-wall AC system. They are a ductless system. The PTAC, which is often used in hotels, has two separate units (terminal packages), an interior evaporative unit and an exterior condensing unit, with an opening that passes through a wall and connects it. It minimizes the traces of the interior system and allows each room to be adjusted independently. The PTAC system can be adjusted to provide heating in cold weather, either directly by using an electric strip, gas, or other heater, or by reversing the refrigerant stream to heat the interior and draw heat from the outside air, converting the air conditioning into a heat pump. While room air conditioning provides maximum flexibility, when used to cool a lot of space at that time it is generally more expensive than central air conditioning.
The first practical semi-portable air-conditioning unit was created by engineers at Chrysler Motors and offered for sale starting in 1935.
Share system
Split-AC systems come in two forms: mini-split and central systems. In both types, an in-environment (evaporative) heat exchanger is separated by some distance from an out-condensing heat exchanger (condensing unit).
Mini-split (ductless) system
A mini-split system usually supplies air-conditioned and hot air to one or more rooms of a building. The multi-zone system is a common application of a no-channel system and allows up to 8 rooms (zones) to be conditioned from one outside unit. Multi-zone systems typically offer various styles of indoor units including wall-mounted, ceiling-mounted, concealed ceilings, and horizontal funnels. Mini-split systems typically produce 9,000 to 36,000 Btu (9,500-38,000 kJ) per hour of cooling. The multi-zone system provides cooling and an extended heating capacity of up to 60,000 Btu.
The advantages of ductless systems include smaller size and flexibility for individual zoning or heating and cooling rooms. The space within the wall required is significantly reduced. Also, the compressor and heat exchanger can be placed further away from the inner chamber, not just on the other side of the same unit as in the PTAC or AC window. Flexible exterior hose leads from the outer unit to the inside (s); this is often covered with metal to look like a common pipeline from the roof. In addition, the ductless system offers higher efficiency, reaching above 30 SIER.
The main disadvantage of air conditioning without air conditioning is the cost. Such systems spend around US $ 1,500 to US $ 2,000 per ton (12,000 BTU per hour) of cooling capacity. This is about 30% more than the central system (excluding the need for ducts) and can cost more than double the window units of the same capacity. "
The possible additional disadvantage that mini-split installation costs may be higher than some systems, although lower operating and rebate costs or other financial incentives - offered in some areas - can help offset initial costs.
Central air conditioning (AC)
Central air-conditioning (dispensing) offers cooling of entire homes or large commercial spaces, and often offers moderate multi zone temperature control capabilities with the addition of an air speaker box.
In central air-conditioning, internal heat exchangers are usually housed inside a central furnace/air conditioning unit of a forced air heating system which is then used in summer to distribute cold air throughout residential or commercial buildings. Click here to watch AHU Animated Work on YouTube
Multi-split system
The multi-split system is a conventional split system, which is divided into two parts (evaporator and condenser) and allows cooling or heating of multiple rooms with one external unit. In this outdoor AC unit there is a stronger compressor, a port for connecting multiple traces and automation with a locking valve to adjust the freon volume supplied to indoor indoor unit.
The difference between split systems and multi-split systems :
Another common type of AC system is a multi-split system, the difference between a separate split system and a multi-split system in some indoor units. Everything is connected to the main external unit, but their operating principles are similar to simple split systems.
Its unique feature is the presence of one major external unit connected to multiple indoor units. Such a system may be the right solution for maintaining microclimate in some offices, stores, large living spaces. Just a few outdoor units that do not worsen the aesthetic look of the building. The main external unit can be connected to several different room types: floor, ceiling, cassette, etc.
Installing Multi-split System :
Before choosing an AC installation location, several key factors need to be considered. First of all, the direction of the airflow from the indoor unit should not fall on the rest area or work area. Secondly, there should be no roadblock obstacles that might prevent it from covering as much space as possible. The outdoor unit should also be placed in an open space, otherwise the heat from the house will not come out effectively outside and the entire system productivity will drop sharply. It is advisable to install an air-conditioning unit in an easily accessible place, for further treatment during operation.
The main problem when installing a multi-split system is the laying of long freon lines to connect an external unit with an internal one. When installing a separate split system, the workers try to find two units opposite each other, where the line length is minimal. Installing a multi-split system creates more difficulties, as some indoor units can be placed away from the outside. The first model of a multi-split system has one common control system that does not allow you to set up individual air conditioners for each room. However, now the market has a wide selection of multi-split systems, where the functional characteristics of indoor units operate separately from each other.
The choice of indoor unit has one restriction - its total power should not exceed the capacity of the outer unit. In practice, however, it is very common to see multi-split systems with total indoor unit capacity greater than at least 20% outdoor capacity. However, it is wrong to expect better performance when all indoor units are turned on at the same time, because the total capacity of the entire system is limited by the capacity of outdoor units. Simply put, the outdoor unit will distribute all its power to all indoor units operating in such a way that some rooms may not have very comfortable temperature levels. However, the calculation of total power is not simple, because it takes into account not only the nominal strength of the unit, but also the capacity of cooling, heating, dehumidification, humidification, ventilation, etc.
Portable unit
Portable air conditioners can be easily transported inside the home or office. They are currently available with capacities of about 5,000-60,000 BTU/h (1,500-18,000 W) and with or without electric-resistance heaters. Portable air conditioners are either evaporative or refrigerative.
Refrigerant systems are air-cooled compressors, which means they use air to exchange heat, in the same way as car radiators or ordinary household coolers. Such systems moisten the air while cooling it down. It collects condensed water from cooled air and produces hot air to be discharged outside the cooled area; it transfers heat from the air in the cooled area to the outside air.
Portable distribution system
The portable system has an indoor unit on the wheel that is connected to an outdoor unit via a flexible pipe, similar to a permanently attached fixed unit.
Portable hose system
The hose system, which can be either monoblock or air-to-air , is discharged out through the air ducts. Type monoblock collects water in bucket or tray and stops when full. The air-to-air type re-vaporizes water and removes it through a channel that is channeled and can run continuously.
A single hose unit uses air from the room to cool its condenser, and then vent it outside. This air is replaced by outside heat or other rooms (due to negative pressure indoors), thus reducing the overall efficiency of the unit.
Modern units may have a performance coefficient of about 3 (ie, 1 kW of electricity will produce 3 kW cooling). A dual-hose unit draws air to cool its condenser from the outside instead of indoors, and thus more effectively than most single hose units. These units do not create negative pressure in the room.
Portable evaporative system
Evaporative coolers, sometimes called "swamp coolers", do not have compressors or condensers. The liquid water is evaporated on the cooling fins, releasing the steam to the cooled area. Evaporating water absorbs large amounts of heat, latent heat of evaporation, cools the air. Humans and animals use the same mechanism to cool themselves by sweating.
Evaporative coolers have the advantage of not requiring a hose to vent heat outside the cooled area, making it completely portable. They are also very cheap to install and use less energy than air conditioning.
Usage
AC engineers widely share AC applications into the convenience and process applications.
Comfort apps
Convenience applications aim to provide in-building environments that remain relatively constant despite changes in external weather conditions or internal heat loads.
Air conditioners make plans in a viable building, because otherwise they have to be built more narrowly or with light wells so the inner spaces receive sufficient outside air through natural ventilation. The air conditioner also allows the building to become taller, as wind speed increases significantly with altitude making natural ventilation impractical for very high buildings. Comfort applications are very different for different types of buildings and can be categorized as:
- Commercial buildings, built for trade, including offices, malls, shopping malls, restaurants, etc.
- High-rise residential buildings, such as high dorms and apartment blocks
- An industrial room where the thermal comfort of the worker is desired
- Cars, airplanes, ships, carrying passengers or fresh goods
- Institutional building, which includes government buildings, hospitals, schools, etc.
- Low-rise residential buildings, including single-family homes, duplexes, and small apartment buildings
- Sports stadiums, such as the University of Phoenix Stadium and in Qatar for the 2022 FIFA World Cup.
The average woman has a much lower resting metabolic rate than men. Using inaccurate metabolic rate guidance for air conditioning measures can result in equipment that is too large and inefficient, and setting up a cold-setpoint operating system can result in reduced worker productivity.
In addition to buildings, air conditioning can be used for various types of transportation, including cars, buses and other land vehicles, trains, boats, aircraft, and spacecraft.
Domestic use
Air conditioning is common in the US, with 88% of new single-family homes built in 2011 including air conditioning, ranging from 99% in the South to 62% in the West. In Canada, the use of air conditioners varies by province. In 2013, 55% of Canadian households reported having air conditioning, with high usage in Manitoba (80%), Ontario (78%), Saskatchewan (67%), and Quebec (54%) and lower use in Prince Edward Island (23%), British Columbia (21%), and Newfoundland and Labrador (9%). In Europe, air conditioning is generally less common. Southern European countries such as Greece have seen a wide proliferation of AC units homes in recent years. In another southern European country, Malta, an estimated 55% of households have air conditioning installed. In India, air conditioning sales fell 40% due to higher costs and stricter energy efficiency regulations.
Application process
The process application aims to provide an appropriate environment for the process being performed, regardless of internal heat and humidity loads and external weather conditions. It is a process requirement that determines conditions, not human preferences. Application processes include this:
- Chemical and biological laboratory
- Cleanrooms for the production of integrated circuits, pharmaceuticals, and the like, where extremely high levels of air cleanliness and temperature and moisture control are required for process success.
- Environmental control from the data center
- Facilities for laboratory animal breeding. Because many animals typically reproduce only in the spring, holding them in a room where conditions reflect spring throughout the year can cause them to reproduce throughout the year.
- Cooking and Food Processing Areas
- Hospitals that operate cinemas, where air is filtered to high levels to reduce the risk of infection and moisture are controlled to limit the dehydration of the patient. Although the temperature is often in the comfort range, some special procedures, such as open heart surgery, require low temperatures (about 18 ° C, 64 ° F) and others, such as neonatal, relatively high temperatures (about 28 ° C, 82 ° F).
- Industrial environment
- Mining
- Nuclear power facility
- Physical testing facility
- Plant and agricultural growing areas
- Textile manufacture
Both in comfort and process applications, the goal may not only control the temperature, but also humidity, air quality, and air movement from outer space into space.
Health effects
Air conditioning systems can promote the growth and spread of microorganisms, such as Legionella pneumophila, an infectious agent responsible for Legionnaires disease, or thermophilic actinomycetes; However, this is only prevalent in less well-preserved water cooling towers. As long as the cooling tower is kept clean (usually using chlorine treatment), these health hazards can be avoided or reduced.
In contrast, air conditioning (including filtering, humidification, cooling and disinfecting) can be used to provide a clean, safe, hypoallergenic atmosphere in hospital operating rooms and other environments where the right atmosphere is essential for patient safety and well-being. Excessive air conditioning can have a negative effect on the skin, causing it to dry out, and can also cause dehydration.
Environmental impact
Power consumption
Innovation in air conditioning technology continues, with much emphasis recently placed on energy efficiency. The electricity production used to operate the air conditioner has an environmental impact, including the release of greenhouse gases.
Cylindrical unloaders are load control methods used primarily in commercial air conditioning systems. In a semi-hermetic (or open) compressor, the head can be mounted with an unloader that removes a portion of the load from the compressor so that it can run better when full cooling is not required. The decomposer can be either electrical or mechanical.
Use of programmable thermostats
In the United States, 87 percent of homes use air conditioning and 65 percent of these houses have central air conditioning. Most homes with central air conditioning have programmable thermostats, but about two-thirds of houses with central air do not use their features to make their homes more energy efficient.
Car power consumption
In the car, the AC system will use about 4 horsepower (3 kW) of engine power, thus increasing vehicle fuel consumption.
Refrigerant
The choice of working fluid (refrigerant) has a significant impact not only on AC performance but also on the environment. Most coolers used for air conditioning contribute to global warming, and many also deplete the ozone layer. CFC, HCFC, and HFC are potent greenhouse gases when leaking into the atmosphere.
The use of CFC as a refrigerant was once common, including R-11 and R-12 refrigerants (sold under the brand name Freon-12 ). Freon refrigerant is typically used during the 20th century in air conditioning because of its superior stability and safety properties. When they are released unintentionally or intentionally, these chlorine coolers eventually reach the upper atmosphere. After the refrigerant reaches the stratosphere, UV radiation from the Sun homologically cuts the carbon-chlorine bond, producing chlorine radicals. This chlorine radical catalyzes the breakdown of ozone into diatomic oxygen, diluting the ozone layer that protects the Earth's surface from strong UV radiation. Each chlorine radical remains active as a catalyst until it binds to another radical, forming a stable molecule and extinguishing a chain reaction.
Prior to 1994, most air-conditioning systems used R-12 as a refrigerant. It was replaced with an R-134a refrigerant, which lacked the ozone depletion potential. The old R-12 system can be fitted to R-134a with complete flush and filter/dryer replacements to remove mineral oil, which is not compatible with R-134a.
R22 (also known as HCFC-22) has a global warming potential of about 1,800 times higher than CO 2 . It has been removed for use in new equipment in 2010, and will be completely discontinued by 2020. Although this gas can be recycled when air conditioning units are discharged, uncontrolled leaks and leaks can release gas directly into the atmosphere.
In the UK, the Ozone Regulation came into force in 2000 and banned the use of ozone that consumes HCFC refrigerants such as R22 in new systems. The regulation prohibits the use of R22 as a "top-up" fluid for maintenance between 2010 (for virgin fluids) and 2015 (for recycled liquids). This means that equipment using R22 can still operate, as long as it does not leak. Although R22 is now banned, units that use refrigerant can still be repaired and treated.
The fabrication and use of CFCs has been banned or severely restricted due to concerns about ozone depletion (see also Montreal Protocol). In view of this environmental issue, commencing on 14 November 1994, the US Environmental Protection Agency has limited the sale, ownership and use of refrigerants to licensed technicians only, per rule under sections 608 and 609 of the Clean Air Act.
As an alternative to conventional refrigerants, other gases, such as CO 2 (R-744), have been proposed. R-744 is being adopted as refrigerant in Europe and Japan. This is an effective refrigerant with global warming potential 1, but must use higher compression to produce an equal cooling effect.
In 1992, a non-governmental organization, Greenpeace, was encouraged by the company's executive policy and requested that European laboratories find replacement refrigerants. This causes two alternatives, one mixture of propane (R290) and isobutane (R600a), and one pure isobutan. The industry rejected changes in Europe until 1993, and in the US until 2011, despite several supportive measures in 2004 and 2008 (see Refrigerant Development above).
See also
References
External links
- Media related to Air Conditioner in Wikimedia Commons
Source of the article : Wikipedia
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