Air Conditioning
From Swikipedia
Introduction
Air Conditioning is ventilation obtained without the use of mechanical devices and external energy. It can also be defined as the control of the indoor environment by controlling the thermal characteristics (cleaning, changing the water content) but mainly heating and cooling the air supplied to the room.
Brief Description
Types of Air Conditioners:
The basic types of air conditioners are room air conditioners, split-system central air conditioners, and packaged central air conditioners.
1. Room Air Conditioners:
Room air conditioners cool rooms rather than the entire home. If they provide cooling only where they are needed, room air conditioners are less expensive to operate than central units are, even though their efficiency is generally lower than that of central air conditioners.
2. Central Air Conditioners:
The “lifespan” of a central air conditioner is about 15 to 20 years. Central air conditioners circulate cool air through a system of supply and return ducts. A central air conditioner is either a split-system unit or a packaged unit.
3. Split-system central air conditioner:
In this, an outdoor metal cabinet contains the condenser and compressor, and an indoor cabinet contains the evaporator. In many split-system air conditioners, this indoor cabinet also contains a furnace or the indoor part of a heat pump. If the building already has a furnace but no air conditioner, a split-system is the most economical central air conditioner to install.
4. Central air conditioner:
This type of air conditioner also is used in small commercial buildings. Air supply and return ducts come from indoors through the home’s exterior wall or roof to connect with the packaged air conditioner, which is usually located outdoors
Air Conditioning Applications:
Air conditioning engineers broadly divide air conditioning applications into comfort and process.
Comfort applications aim to provide an indoor environment that remains relatively constant in a range preferred by humans despite changes in external weather conditions or in internal heat loads.
o Commercial buildings, which are built for commerce, including offices, malls, shopping centers, restaurants, etc.
o Institutional buildings, which includes hospitals, governmental, academic, and so on
o Industrial spaces where thermal comfort of workers is desired
o Low-Rise Residential buildings, including single family houses, duplexes, and small apartment buildings
o High-rise Residential buildings, such as tall dormitories and apartment blocks
In addition to buildings, air conditioning can be used for comfort in a wide variety of transportation including land vehicles, trains, ships, aircraft, and spacecraft.
Process applications aim to provide a suitable environment for a process being carried out, regardless of internal heat and humidity loads and external weather conditions. Process applications include these:
o Hospital operating theatres, in which air is filtered to high levels to reduce infection risk and the humidity controlled to limit patient dehydration
o Clean rooms for the production of integrated circuits, pharmaceuticals, and the like, in which very high levels of air cleanliness and control of temperature and humidity are required for the success of the process
o Facilities for breeding laboratory animals. Since many animals normally only reproduce in spring, holding them in rooms at which conditions mirror spring all year can cause them to reproduce year round
o Aircraft air conditioning
o In addition to aircraft air conditioning ,it also includes Data Processing Centers, Textile Factories , Physical Testing Facilities , Plants and Farm Growing Areas , Nuclear Facilities , mines, industrial environments, Food cooking and processing areas.
In both comfort and process applications the objective may be to not only control temperature, but also humidity, air quality, air motion, and air movement from space to space.
Air Conditioner Efficiency:
Each air conditioner has an energy-efficiency rating that lists how many Btu per hour (Btu, the abbreviated form of British Thermal Units is the traditional unit of energy, one Btu = 1.06 Kilojoules) are removed for each watt of power it draws. The three cooling-efficiency measurements defined in the ARI standards are EER (the energy-efficiency ratio). SEER (the seasonal energy-efficiency ratio), and IPLV (the integrated part-load value).
o LER is a ratio of the rate of cooling (Btu/h) to the power input (in watts) at full-load conditions.
o SEER is a seasonally adjusted rating based on representative residential loads that apply only to units with a cooling capacity of less than 65,000 Btu/h.
o IPLV, a seasonal efficiency rating method based on representative commercial loads, applies to units with cooling capacities at or greater than 65,000 Btu per hour.
o For room air conditioners, this efficiency rating is the Energy Efficiency Ratio, or EER, Room air conditioners generally range from 5,500 Btu per hour to 14,000 Btu per hour.
o For central air conditioners, it is the Seasonal Energy Efficiency Ratio, or SEER.
