Methods of refrigeration

Submitted by: Jeremy .Dawes..

Air conditioner is a system or an appliance which is designed to drive out heat from an area (using a refrigeration cycle), there by cooling the area as desired. The system consists of a complete set of heating, ventilation and Air conditioning which is popularly called as a HVAC (stands for heating, ventilating and air conditioning). An air conditioner is commonly used to provide comfort in homes or in offices or in vehicles or storage facilities during hot seasons. Within a refrigeration cycle, a heat pump removes heat from a lower temperature heat source to a relatively higher temperature heat sink. Naturally heat flows from higher temperature to lower temperature areas. A house hold refrigerator works in an identical way where it sends our heat from the inside of the appliance into the room.

Air conditioning systems or air conditioners simple generally reduce the humidity of the air processed. As humans perspire normally to get natural cooling by the evaporation of sweat from the skin, dry air improves the comfortness. A typical air conditioner is designed to provide 40 to 60% relative humidity in a closed area. Some conditioners just dry the air without actually cooling. They work similar to a normal air conditioner, except that between the intake and exhaust, a heat exchanger is placed and consume only one third of the electricity compared to a normal one. Some people prefer them who dislike the draft created by air coolers. Refrigerants like FREON are commonly used in air conditioners for their safety properties and superior stability. Now research shows that all the chlorine bearing refrigerators break up in the stratosphere due to UV radiation from the sun, there by releasing chlorine atoms which damage the ozone layer (vital component protecting the earth’s surface from harmful UV radiation).

There are different types of air conditioners. The Window and through wall systems are used in homes or offices. They are single rectangular units normally placed outside the buildings through a window or openings in the wall as outer air is used to cool the condenser section. The window systems have vents on both the inside and the outside so that inside air which is to be cooled will be blown in and out by a fan and also outside air that can be blown in and out by another fan (acting as a heat sink). If any building needs cooling for every room, then central air conditioning can be used and is less expensive. Evaporation coolers or swamp coolers are mostly used in dry climates for providing comfort and cooling. As these are mostly used in Iran, they are also known as Persian coolers. It is a device which draws outside air through a large and wet sponge or pad soaked in water. The sensible heat of the coming air is reduced and the total heat (latent plus sensible) of the entering air is unchanged. Sensible heat is sometimes converted into latent heat by evaporation of water in the pads. As the air is Iran is dry enough the results are quite good and cost much less and easy to maintain.

Gas turbines are used to generate electricity and the exhausts of these turbines are hot enough to force an absorptive chiller that generates cold water. This cold water is run through radiators in air ducts for cooling. This dual usage of energy is useful when regional utility and fuel prices are reasonable. Producing heat, cooling and power in a single system is called trigeneration. Central air conditioning is popularly known as central air in the US or air-con in the UK and is a system which uses air ducts to spread or distribute cooled and dehumidified air to various rooms in a building. The split system consists of a condenser and compressor in an outdoor unit and the evaporator is mounted in an air handling unit. In a package system, all the components are located in a single outdoor system. These central air conditioners have benefits like removing pollutants and dust from the outside, low noise levels as the outdoor unit is far away.

The air conditioning systems are expensive and consume a lot of power and exert extreme load on the power systems and the grids. The power is measured in tons and a ton of refrigeration is defined as the cooling power of one ton (2000 pounds) of ice in a 24 hour period (which is equal to 3517 watts or 12000 BTU per hour). House hold central air conditioners usually are of 1, 2, 3, 4, and 5 tons in capacity.