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For Qatari residents: Do you prefer a summer or winter World Cup 2022?

Oh Cool!

Written by  Author |   Mon, 15 September 2014 12:12

In the most general sense, air conditioning is the technology of modifying the condition of air (heating, cooling, (de-)humidification, cleaning, ventilation, or air movement). Nevertheless, in construction, such a complete system of heating, ventilation, and air conditioning is referred to as HVAC.

The first modern electrical air conditioning unit was invented in 1902, by Willis Carrier in New York. Designed to improve manufacturing process control in a printing plant, Carrier's invention controlled not only temperature but also humidity. Carrier used his knowledge of the heating of objects with steam and reversed the process. In 1915 he and several partners formed the Carrier Engineering Corporation, which they dedicated to improving the technology of air conditioning. Among the key innovations was a more efficient centrifugal compressor, which Carrier used in the air conditioners he installed in Detroit's J. L. Hudson Department Store in 1924, the first department store so equipped. Office buildings soon followed.

In 1933, the Carrier Air Conditioning Company of America developed an air conditioner using a belt-driven condensing unit and associated blower, mechanical controls, and evaporator coil, and this device became the model in the growing market for air-cooling systems.

However, the first private home to have air conditioning was built in Chapel Hill, North Carolina in 1933. Realizing that air conditioning would one day be a standard feature of private homes, particularly in regions with warmer climate, David St. Pierre DuBose (1898-1994) designed a network of ductwork and vents for his home Meadowmont, all disguised behind intricate and attractive Georgian-style open moldings. This building is believed to be one of the first private homes in the United States equipped for central air conditioning.

Today's air conditioners, while operating on the same fundamental science as Carrier's 1933 system, incorporate advancements in vapor compression, diagnostics and controls, electronic sensors, materials, and energy efficiency.

Mechanical refrigeration for air conditioning relies on a closed system in which a refrigerant—basically a compound of elements with a low boiling point—circulates through sets of coils that absorb and dissipate heat as the refrigerant is alternately compressed and allowed to expand. In an air conditioner, coils containing refrigerant draw heat and moisture from room air.

The first air-conditioners were bulky, reproduced huge noises and gave out toxic chemicals too. These toxins namely, ammonia, methyl chloride and propane, were inflammable and when leaked caused fatal effects in the atmosphere and even to human lives. In 1928, an air-conditioner was built using Freon which was considered much safer for humans though it was hazardous for the environment. Thomas Midgley was the inventor of this Freon using air-conditioner.

Air-conditioners were a luxury limited to the rich sections of the society but that was only in the early 1930s and 1940s. Slowly with steady steps, Air-conditioning walked into the corporate world and demanded the bosses to provide their employees with the comfort of ACs. The wave of air-conditioning spread world-wide and by 1957, most of the offices had air-conditioners installed.

The bulky ACs have now shrunken and are no more noisy. The emission of chemicals too doesn't happen and besides all these improvements efforts are continued to be made to improve air-conditioning and the emphasis is now on energy conservation and efficiency.

HVAC ‘conquers' AC
Mainly in construction, a complete system of heating, ventilation, and air conditioning referred to as HVAC is used.

HVAC (heating, ventilation, and air conditioning) is the technology of indoor and vehicular environmental comfort. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC is important in the design of medium to large industrial and office buildings such as skyscrapers and in marine environments such as aquariums, where safe and healthy building conditions are regulated with respect to temperature and humidity, using fresh air from outdoors.
In modern buildings, the design, installation, and control systems of these functions are integrated into one or more HVAC systems. For very small buildings, contractors normally estimate the capacity, engineer, and select HVAC systems and equipment. For larger buildings, building service designers, mechanical engineers, or building services engineers analyze, design, and specify the HVAC systems. Specialty mechanical contractors then fabricate and commission the systems. Building permits and code-compliance inspections of the installations are normally required for all sizes of buildings.

Although HVAC is executed in individual buildings or other enclosed spaces, the equipment involved is in some cases an extension of a larger district heating (DH) or district cooling (DC) network, or a combined DHC network. In such cases, the operating and maintenance aspects are simplified and metering becomes necessary to bill for the energy that is consumed, and in some cases energy that is returned to the larger system. For example, at a given time one building may be utilizing chilled water for air conditioning and the warm water it returns may be used in another building for heating, or for the overall heating-portion of the DHC network (likely with energy added to boost the temperature).

Installation types
Window unit and packaged terminal
Window unit air conditioners are installed in an open window. The interior air is cooled as a fan blows it over the evaporator. On the exterior the heat drawn from the interior is dissipated into the environment as a second fan blows outside air over the condenser. A large house or building may have several such units, permitting each room to be cooled separately.

PTAC systems are also known as wall-split air conditioning systems or ductless systems. These PTAC systems which are frequently used in hotels have two separate units (terminal packages), the evaporative unit on the interior and the condensing unit on the exterior, with an opening passing through the wall and connecting them. This minimizes the interior system footprint and allows each room to be adjusted independently. PTAC systems may be adapted to provide heating in cold weather, either directly by using an electric strip, gas, or other heater, or by reversing the refrigerant flow to heat the interior and draw heat from the exterior air, converting the air conditioner into a heat pump. While room air conditioning provides maximum flexibility, when used to cool many rooms at a time it is generally more expensive than central air conditioning.

The first practical through-the-wall air conditioning unit was invented by engineers at Chrysler Motors and offered for sale starting in 1935.

Split systems
Split-system air conditioners come in two forms: mini-split and central systems. In both types, the inside-environment (evaporative) heat exchanger is separated by some distance from the outside-environment (condensing unit) heat exchanger.

Mini-split (ductless) system
A mini-split system typically supplies chilled air to a single or a few rooms of a building. Mini-split systems typically produce 9,000–36,000 Btu (9,500–38,000 kJ) per hour of cooling. Advantages of the ductless system include smaller size and flexibility for zoning or heating and cooling individual rooms. The inside wall space required is significantly reduced. Also, the compressor and heat exchanger can be located further away from the inside space, rather than merely on the other side of the same unit as in a PTAC or window air conditioner. Flexible exterior hoses lead from the outside unit to the interior one(s); these are often enclosed with metal to look like common drainpipes from the roof. In addition, ductless systems offer higher efficiency (up to 27.1 SEER on some systems).

Central (ducted) air conditioning
Central (ducted) air conditioning offers whole-house or large-commercial-space cooling, and often offers moderate multi-zone temperature control capability by the addition of air-louver-control boxes.

In central air conditioning, the inside heat-exchanger is typically placed inside the central furnace/AC unit of the forced air heating system which is then used in the summer to distribute chilled air throughout a residence or commercial building.

Portable units
A portable air conditioner can be easily transported inside a home or office. They are currently available with capacities of about 5,000–60,000 BTU/h (1,800–18,000 W output) and with or without electric-resistance heaters. Portable air conditioners are either evaporative or refrigerative.

The compressor-based refrigerant systems are air-cooled, meaning they use air to exchange heat, in the same way as a car or typical household air conditioner does. Such a system dehumidifies the air as it cools it. It collects water condensed from the cooled air and produces hot air which must be vented outside the cooled area; doing so transfers heat from the air in the cooled area to the outside air.

The top 10 AC manufacturers in the world include Hitachi, LG, Carrier, Samsung, Voltas, Daikin, Blue Star, Whirlpool, Videocon and Haier.

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October / 10 / 2014
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