WiFi tech

Type of air conditioner

2020-06-13T12:36:00.001+05:30

Various types of commercial air conditioners

A commercial air conditioner can be divided into various types. Each type has its own characteristics, and it is important to select an air conditioner that suits the usage environment and application.

In general, commercial air conditioners are also called packaged air conditioners and are distinguished from household room air conditioners. The most commonly used packaged air conditioner is the “air conditioner for stores”. Similar to home air conditioners, many of these have outdoor and indoor units paired together and can often be found in relatively small stores and offices.

"Air conditioners for stores" can be further classified, and the types are generally divided according to the installation method. Let's see a representative one.

・Ceiling embedded cassette type

The air conditioner itself is embedded in the ceiling so that only the outlet panel can be seen. There are two types, one that can blow air in all directions and one that has two directions. It has excellent design because it can be integrated with the ceiling.

・Duct type

The air conditioner is embedded in the ceiling, and only the outlets connected by ducts are visible. The feature is that the position of the air outlet can be freely laid out, and uneven temperature in the room is unlikely to occur.

・Ceiling suspension type

The air conditioner itself is exposed under the ceiling due to the installation method of suspending the indoor unit from the ceiling. Suitable for narrow spaces due to its high ventilation capacity. Also, installation is relatively easy.

・Wall hanging type

Just like a home air conditioner, it is installed on the wall. It is easy to install and easy to maintain.

・Floor type

It is an installation method that puts the air conditioner body directly on the floor. It is suitable for spaces where the ceiling is high and it is not possible to blow air to the feet when using the embedded ceiling type. Even very large ones can be installed in a short period of time.

On the other hand, what you often see in large buildings is a large-scale commercial air conditioner called "multi air conditioner for buildings" . Unlike home air conditioners, outdoor units can be integrated even if the number of indoor units is large, so it is excellent in convenience during maintenance and maintainability. In addition, the indoor unit has a multi-operation function and can be operated individually. Therefore, it is economical because it is possible to adjust the number of operating indoor units according to the room temperature and to operate the indoor units only in the room in which they are used.

"Multi air conditioners for buildings" can also be classified into more detailed types for each system. Let's see a representative one.

・Cooling and heating individual operation multi

It is a system that can change the operation method for each indoor unit. You can set the temperature individually such as cooling in one room and heating in another, and you can turn off the air conditioning in unused rooms, which is excellent in energy saving and comfort.

・Multi for an ice storage building

It is a system that stores ice during times when power consumption is low at night and is used during cooling operation during the day. It is excellent in energy saving because it can reduce power consumption during peak hours. Hot water is stored at night during heating operation in winter.

・Gas heat pump air conditioner

It is a system that suppresses the electric power load at the peak by operating a compressor by burning gas such as propane gas. You can use the heat of combustion of gas to defrost, so you do not have to feel uncomfortable when you pause during heating.

In addition to these, there are "facility air conditioners", "wall through air conditioners", and "distributed water heat source air conditioners" that are unique to commercial air conditioners. Most of the "air conditioners for equipment" are large floor-standing type and blow off from a duct. "Wall-through air conditioner" is an air conditioner that blows air from the waist-high wall under the window. Since the air conditioner is installed in a place where it can exchange heat with the outside air, it radiates heat directly to the outside during cooling and collects heat directly from outside during heating. "Dispersed water heat source air conditioner" is a system that connects many packaged air conditioners to the water circulation equipment. For example, when air conditioning and heating are used at the same time, the heat discarded in the circulating water can be reused, which is excellent in energy saving.

As you can see, there are many types of commercial air conditioners, but the shape of the room is the most important factor to consider when installing or replacing a new air conditioner. For example, for a standard room close to a square, a ceiling-embedded room with outlets in 4 directions is suitable. On the other hand, if you can install the indoor unit in only one place in a long and narrow room, we recommend the ceiling hanging type or wall hanging type that allows the wind to reach the other side. If space has a very high ceiling, the floor-standing type may be suitable for the application.

Depending on the room shape, it may be desirable to install a combination of different types of commercial air conditioners. Carefully consider the shape of the room and the capacity of the air conditioner when installing or replacing.

How does glacier form?

2020-06-11T18:49:00.004+05:30

Glacier

The snow that has accumulated on the ground (snow) gradually becomes thicker and becomes ice, and it is called a glacier when it becomes fluid due to gravity.

How does glacier form?

Let us see how does glacier form. The density of fresh snow (fresh snow) is about 0.05-0.15g/cm ³ and the space between the snow crystals is filled with air. However, when the snow is thick, the gap from the top is crushed (consolidation), and the air escapes to become hard (snow). Also, if the snow melts during the day and freezes again at night, coarse-grained rough snow will form. In this way, the snow cover gradually increases in density, and when the density reaches 0.5 g/cm ³ or more, it is called firn. When the firn is further consolidated and the density becomes about 0.83 g/cm ³ or more, the gap between the crystals is disconnected and the air trapped as bubbles. This is glacier ice or glacial ice. The change from fresh snow to glacier ice is called metamorphosis, and it progresses relatively quickly when snow accompanies melting (warm metamorphosis), but when it does not melt due to low temperatures such as Antarctica (cold metamorphosis), the transformation slowly progresses over hundreds of years.

Glacier mass balance

A glacier is divided into a recharge area and consumption area. The recharge area is, in which the amount of snow and ice (recharge) that accumulates on, it is greater than the amount of snow and ice that melts (amount of consumption), and a consumption area in which the amount of recharge is less than the amount of consumption. The higher the temperature, the greater the amount of consumption, so the upstream side of the glacier is the recharge area and the downstream side is the consumption area. At the boundary between the two, the amount of recharge and the amount of consumption are equal. This line is called the balance line (balanced line). Because the amount of snow in the recharge area exceeds the amount of snowmelt, the surface of the glacier is always covered with fresh snow or snow that fell in the previous year, that is firn, and glacier ice appears from a certain depth. On the other hand, in the consumable area, the amount of snowmelt exceeds the amount of snow cover, so glacier ice is always exposed except after snowfall. Therefore, in a glacier with snow in winter, the snow melts from the downstream side in summer, and at the end of summer, the only firn remains in the recharge area. The line connecting the lower limits of the firn is called the filling line, and approximately indicates the position of the balance line. The balance between recharge and consumption of glaciers is called the mass balance of glaciers. For glaciers such as Antarctica, where the temperature is low and the entire area is a rechargeable area, the glaciers drain into the sea and become icebergs (iceberg separation, carving calving), which consumes the glaciers. , Keeps its mass balance.

Glacier flow

Since the amount of snow in the recharge area exceeds the amount of melting, the glacier will become thicker and thicker, while the amount of melting will be larger in the consumable area, the glacier should become thinner. However, in stable glaciers, the shape and thickness of glaciers hardly change year by year. This is because the amount accumulated in the recharge area compensates for the amount melted in the consumption area, which is the flow of glaciers. However, the question of why ice (solid) glaciers flow has long been a problem for physicists. J. Forbes, who studied alpine glaciers in the 19th century, published a viscous theory that glaciers flow like candy, while J. Tyndall discovered glacier flow by Faraday. Explained by the theory of recovery ice. At present, it is believed that plastic deformation of ice crystals and the bottom slip of glaciers cause flow. Since the ice crystal is near the melting point, it is plastically deformed when the metal that is heated strongly receives a force to easily deform it. The ice crystals have a structure just like stacked playing cards, so if gravity is applied from above, the crystals will shift and deform like the collapsing cards.

The study of plastic deformation of ice has helped to develop rheology. The flow due to plastic deformation plays a major role in the flow of glaciers in Antarctica, such as glaciers in which ice is always frozen on the bedrock of the bottom (cold glaciers). On the other hand, in glaciers that melt due to the pressure of ice (pressure melting) and there is a thin water film on the bottom of the glacier (warming glacier), the glacier slides on this water film. Bottom slip is the main cause of flow. Cold glaciers that flow only by plastic deformation have a slow flow rate of only a few meters to tens of meters per year, but in warm glaciers where bottom slip is actively occurring, tens to hundreds of meters per year. In the valley glacier, the flow velocity is larger in the central part like the river and becomes smaller due to friction near the valley wall. When the ice is stretched or crushed due to such a difference in flow velocity and a sudden change in the slope of the bottom surface, crevices are formed in the glacier. When a glacier passes through a particularly steep slope, many crevasses break the ice glacier into small pieces of ice called shellac seracs. These places look like glacier waterfalls and are called icefalls. Downstream of the icefall, a stripe pattern with a convex surface on the downstream side may be seen on the surface of the glacier. These are called ogives, which consist of blue ice without bubbles and white ice with bubbles. Blue ice is glacier ice that passed through the icefall in the summer, and it repeatedly melts and freezes on the surface, becoming blue due to the inclusion of fine dust, and the white ice remains frozen in winter. It corresponds to the ice that passed through the fall. Therefore, the interval of the ogives represents the one-year drift distance of the glacier.

Climate change and glaciers

Glaciers expand and contract as the climate changes. If the temperature drops or the amount of snowfall increases, the amount of recharge increases and the amount of consumption decreases, so the position of the equilibrium line (snow line) decreases and the glacier advances (expands). Conversely, glaciers recede (shrink) if there is a rise in temperature or a decrease in snowfall. The glacial period is when the glaciers moved forward and expanded due to the cold climate, creating a large ice sheet in the northern hemisphere.

History of an air conditioner

2020-06-09T23:44:00.003+05:30

The people who created Cooler mechanism (History of an air conditioner)

The commercial use of the air conditioner, the predecessor of coolers, began about 10 years after the sales of electric fans began. One of the basic principles is an experiment done by Benjamin Franklin (1706-1790), who is known as an American inventor, scientist, and politician, and John Hadley (1731-1762) at the University of Cambridge, England. Franklin is also famous for conducting electrical studies, proving that lightning is an electrical phenomenon, and devising a lightning rod in 1749. In 1758 he has done two experiments to rapidly cool an object using the principle of evaporation (heat of evaporation). He then tried to evaporate a highly volatile liquid, such as alcohol, and discovered that ether could cool an object to below freezing. Franklin concludes that humans could be frozen to death on warm summer days.

Then in 1820, British chemist and physicist Michael Faraday (1791-1867) discovered that vaporizing liquefied ammonia by compression could cool the surrounding air. In addition to this, Faraday had considered one of the most influential scientists in the history of science, contributing to the fields of electromagnetics and electrochemistry, including "Faraday's Law of Electromagnetic Induction".

Thirty years after the discovery of Faraday, John Gory (1802-1855), a Florida (USA) doctor uses a compression-type ice machine to make ice and chill the patient's room in his hospital for the patient. He did this because the general theory is that bad air causes illness. He had the idea of controlling the temperature of the whole building, the whole city, and controlling the air conditioning centrally, but it didn't work. However, in 1851, Gory got a patent for the ice machine.

It was an American engineer and inventor Willis Havilland Career (1876-1950) who invented the modern cooler. After graduating from the Department of Electrical Engineering at Kernel University, he joined Buffalo Forge, one of the three largest fan makers in the United States, in 1901.

In 1902, the job of humidity control at the Sackett Wilhelms printing plant in New York was brought to him. The printing factory at that time started multicolor printing, and the change in humidity in the room caused the paper to expand and contract, which made printing unsuccessful. The carrier's "electric air conditioner," which is required to keep the relative temperature inside the room constant, can control not only temperature but also humidity. By keeping the temperature and humidity low, the condition of the paper was kept constant and the ink adhered well. His invention has since contributed greatly to the development of air conditioning technology.

After further improvement and field tests, in 1906, Carrier obtained a patent for its invention and introduced the world's first spray-type air conditioner (which can humidify and dehumidify by heating and cooling water) to the world.

In 1906, when the carrier was granted a patent, Stuart W. Crammer of America sought a way to add moisture to his textile factory. A combination of humidification and ventilation is used to control the humidity in the factory to achieve the optimum value. When he applied for a patent, he used the term "air conditioning" for the first time. This is the origin of the word "air conditioner" as mentioned above.

Air conditioners and refrigerators in the early days used toxic or flammable gases such as ammonia, chloromethane, and propane. If they leaked out, there was a risk of death. Against this backdrop, in 1928, American industrial chemist Thomas Midilly (1889–1944) was asked to research substances that would replace toxic and flammable refrigerants. Freon was developed. This refrigerant was safe for humans but later found to be harmful to the ozone layer.

Currently, specific CFCs and alternative CFCs are used, but it cannot be denied that they are the cause of ozone layer depletion and global warming. Although it is a necessary refrigerant for coolers and refrigerators, technological development in air conditioning technology continues to protect the global environment of the future.

Mechanism of cooler born from various researches and inventions

The cooler was born from the experiments, research, and inventions of these ancestors. It is a device called "heat exchanger", which is used for various industrial products such as boilers, steam generators, condensers, air conditioners, and vehicles. This is an equipment that transfers heat from a fluid with a high temperature to a fluid with low temperature by utilizing the property that heat flows from a location with a high temperature to a location with a low temperature. It is heated and cooled by moving and replacing.

The basis of how heat exchangers work is the nature of liquids and gases. When a liquid turns into a gas (evaporates), it absorbs heat from surrounding objects. The lower the evaporation temperature and the lower the pressure, the greater the heat absorption. On the contrary, heat is released when the gas turns into a liquid (condensation), but it is known that if cooled at high pressure, it is easy to condense and the heat radiation increases.

For example, after sweating in the summer, when you hit the air it feels very cool, and when you wipe your hands with alcohol, it is cool because water or liquid alcohol evaporates and takes a lot of heat from the surroundings when it becomes a gas.

Coolers use these properties of fluids to control room temperature which is called as air conditioner afterword. An air conditioner consists of an indoor unit and an outdoor unit, and a fluid (refrigerant gas) circulates in the refrigerant pipe that connects them. When the fluid that became a low-temperature liquid in the decompressor of the outdoor unit enters the indoor unit, it becomes gas due to the heat inside the room. At this time, the heat of vaporization is generated. Cooled air is sent out from the indoor unit by removing the heat of the indoor air drawn by the fan. The vaporized fluid returns to the outdoor unit and becomes hot gas in the compressor. After that, when it passes through the heat exchanger of the outdoor unit, it is cooled by the fan and releases heat to the outside to return to liquid. The mechanism of the air conditioner (cooler) is that the liquid is sent to the indoor unit again.

Heating is the opposite of this, in which the heat of the outside air is absorbed and the refrigerant that has become a high-temperature gas in the compressor of the outdoor unit is sent to the indoor unit. The heat exchanger heated by the gas emits heat into the room with a fan. This creates a warm breeze from the indoor unit. Air heat in the room is sent to the outdoor unit by refrigerant gas and released to the outside. This circulation controls the temperature of the room.