Air Conditioning Systems - Their Use, The Types and The Impact
Air conditioning refers to the cooling, heating, ventilation and even disinfection of air. The process modifies the condition of air. The principle of air conditioning has been used since the ancient Roman times. Water from the aqueduct was circulated through walls of Roman houses to regulate temperature. Cisterns were used by Persians to cool their homes. The Medieval Egyptians had some form of ventilators for their homes. However it wasn't until 1902 that the first electrical air conditioner was invented by Willis Haviland Carrier.
The air conditioner was not invented for the comfort of humans but more on the conditioning of air for the improvement of the manufacturing process of a printing press. The low heat and humidity helped produce consistent paper sizes and ink alignment. Later on, modifications were done to increase productivity in the workplace.
The first air conditioners and refrigerators used flammable and toxic chemicals that could cause fatal accidents when leaked. Fortunately chlorofluorocarbon gas was created by Thomas Midgely in 1928. Freon is a trademark name for chlorofluorocarbon or what is known today as CFC or HCFC. The names most associated with HCFC are R-11, R-12, R-22 and R134A. The HCFC used in air conditioner units at homes' and buildings' comfort cooling is R-22. In 2010, R-22 will no longer be used in new appliances and by 2020, R-22 will no longer be produced like R-11 and R-12 which is now phased-out in the USA. "Greener" refrigerant like R-410A and R-744 have been proposed for use.
Types of Air Conditioning System
Air conditioning systems can be classified according to the way cooling is achieved. Note that air conditioning of a residential unit is different from air conditioning a factory or a nuclear power plant. Here are the four basic systems of air conditioning.
- Central chilled water air conditioning systems - All Air Systems.
- Central chilled water air conditioning systems - air and water systems
- Central chilled water air conditioning systems -all water system including cooling tower
- Direct Expansion system - meaning direct expansion of refrigerant without passing through chilled water. This includes window-type air conditioners; split-type and package air conditioners, unitary and roof top air conditioners and heat pumps.
The first three systems are used mostly for air conditioning large areas and high rise buildings. Centralized air conditioning it is called. More and more homes are opting for centralized air conditioning to take care of the heating, cooling, and ventilation needs.
For some homes, centralized air conditioning may not be feasible or affordable. In cases like these, there is always the direct expansion system of air conditioning to depend on. When looking for an air conditioner unit make sure you look at the energy efficiency rating label attached to it.
Two Applications of Air Conditioning
Carrier said it all when first; he invented and installed an air conditioning unit in the printing plant to control the quality of printing. Next, he modified the air conditioner so he could provide a better working condition (cooler and drier air) to the employees' thereby increasing production. In a nutshell, air conditioning is for process and comfort.
Process applications mean to provide the right setting for a process or procedure in terms of the proper thermal condition regardless of the weather condition outside and/or the internal heat and humidity of the rest the building.
- Food cooking and processing
- Hospital operating theatres
- Nuclear plants
- Data Centres
- Textile factories
Comfort applications strive to have a constant indoor environment that is favoured by humans regardless of temperature or weather conditions outside. Air conditioning makes it feasible to build structures of any width and height. Without air conditioning it will not be possible to build deep structures without light wells for the inner areas to get ample natural ventilation. Without air conditioning it would not be possible to build tall buildings for increased height in structures means increased wind velocity thereby making natural ventilation for buildings not viable. Comfort applications for different structures differ and may be categorized as:
- Low-rise residential buildings - detached, semi-detached, terraces and small apartment buildings
- High-rise residential buildings- including apartment blocks, hotels
- Commercial buildings -malls, offices, restaurants, shopping centres
- Industrial areas where air conditioning comfort for the workers is aimed for
- Institutional buildings- including schools, government, hospitals and the likes
Impact of Air Conditioning
The mid 20th century saw a rising peak in the sales of air conditioner units. Centralized air conditioning was just a pipe dream then. The evolution in air conditioning technology has made quite an impact on the different aspects of your life. Air conditioning has changed your lifestyle - the way you work; the way you play and the way you live.
Architecture was greatly affected too. The advances in mechanical cooling towers at the early part of the 20th century made it possible to build the first skyscrapers in the USA. New forms of architecture evolved and whereas it was mandatory to design and build buildings with natural ventilation (windows in every room) air conditioning have made it possible to design "windowless" structures for more air tight and therefore more energy efficient buildings.
House air conditioning meant that some traditional architectural features like wide eaves, deep porches, thick walls, high ceilings, lofts, and cross ventilation, are no longer essential for natural cooling.
Air conditioning made it possible to build artificial indoor climates. You may not be able to control nature but you certainly can control indoor "nature". Man is no longer governed by the seasons or by the time of day or by time zones.
By the year 2010, harmful HCFC R-22 will be phased out. All new appliances that will be out in 2010 would be using another greener form of refrigerant. If you are planning to buy a new unit soon, wait for the more earth-friendly models by the year 2010.