The discovery of the princples of Air condtioning is one of the most mportant events in the twenteth century. Human being can work more efficiently and enjoy more leisure in comfort becausc of Air conditioning. When most people hear the expression Aur Conditioning they think of cost temperature. However Air conditioning applies in the heating season as well as in summer season. Thus, Air conditoning makes it. possible to change the condition of the air in an enclosed area. Since. most people spend a large portion of their lives in enclosed areas, some of the common uses of Air conditionng are in offices, homes, hotels. hospitals,drug industres, electrical industries. In miltary centres which can track and interccpt missiles are able to operate around the clock only because of air is at controlled temperature. Without Air conditioning computers quickly cease to operate because of the intense self generated heat. Atomic submarines can remain submerged almost indefintely due to air conditiong The uses of air conditioning shows. that when new products are made. or when new discoveres take place. and certainly in the exploration of space, Air-conditioning plays a key role The Air conditioner was invented by Dr. Willis H Carrier in 1904. To understand the complete air condtioning system it is necessary to. know the detiniton of air conditionng, method of controlling Hummidity, working of an Air Handling Unit and technical and scientilici terms commonly used in various types of Air conditioners such as window . type and split type should also be known to you.
After studying this lesson, you will be able to :
● define air conditioning
● mention the main parts of an air conditionERS
● and explain the working of each part of an air conditioner
● describe the systematic wiring daigram of an air conditioner
● explain the types of air conditioner and distinguish between window type and split type air conditioner
● adjust the range of temperature and humidity required for comfort air conditioning
● know the process purificaton of circulation air
The process of controlling simultaneously the temperature,humidity. circulation of air purification of air in a closed insulated space is called Air Conditioning. Let us see one by one how these are controlled. Temperature : It is controlled wth the help of an air conditioning. machine consisting of a cooling coil, compressor, condenser. filter, capillary tube or refrigerant control devce, blower motor, suction and discharge line The above parts are connected in a systematic method.The system is made leak proof and then freon. 22 is flled in the system when the compressor is switched on, the. piston in the compressor starts moving up and down. When piston moves downward it sucks reingerant through the suction. Line, and when the piston moves upward it compresses the refrigerant to a high pressure high temperature gas. This gas is cooled with the help of air/water in the condenser and the gas becomes. liquid. This liquid refrigerant contains some impurities which are filtered with the help of a filter.
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Now thus liquid refrigerant free from impurities enters in the refrigerant control device which controls the flow of the refrigerant and permits a calculated quantity of liquid refrigeration and permits a calculated quantity of liquid to enter in the cooling coil in the form of a fine spray and thus the pressure of this liquid refrigerent is reduced as soon as it reaches in the coolng coil Due to this drop in refrigerant liquid pressure the liquid starts evaporating in the cooling Due to this evaporation of liquid refrigerant in the cooling effect is produced, because we know coolng is produced evaporation
In the cooling coil of an air conditioner 45- 50F temperature maintained. A blower is fitted behind the cooling coil with the lower motor. When this motor 1s swtched on the blower sucks are iro the enclosed space and passes this aur through the. coi. Because the temperature of the cooling coul is very low. 50 F the aur becomes cold. This cold aur is crculated in the. nsuated space agan and again so alter some times the tempet. n the insulated space becomes between 70 to 80 F.This is the conditioned room temperature. Humidity:
The moisture present tn the air is measure humidity. For example, so relative humidity means that air contains a the amount of moisture that it half capable to he measured in grains of water vapour A graun is so so ound of water contauns 7000 grains of water Humidity is measured with the help of a sling psychrometer and psychrometEric chart the comfort range for the human body is 45 Controlled with the help of a humidity state or humidi control switch.
Humidi state/Humidity control switch
The proprty of these horse haurs is that the moosture in the air increases the length of hairs also increase when the miosture in the air decreases the lenth of hair decreases on ths princple a humidi state operates. There are three electrcal termnals in this control switch A t. attached to the hairs is a moving contact which moves upw. humidity is less and movrs downwatd when humidity is thote ate two lised contact ponts At one pouit a watet spraypumDot pray pump is connected whereas at the other point heate connected When humidity is less the water spray pump is swit. and water is spraved through the water spray noarls in the firnl spray he arculating aif, when passes through this water the t. n the air increases and when the humidity is more the heate. witched on and wien thus air passcs through the heaters the n. decreases and when the required humidity is maintauncd at 4. 35% the water spray pump and heaters are cut ofl with the help of the. humidi state. This humdity control swtch is gencrally used wth central ar condtonerng plants only The humdity is controlled by controlling. the tmperature of the coiling coil.
Circulation of Air : It is done with the help of a motor fitted with a blower In an air conditoned room the room air is circulated again and again with the help of a blower motor. The blower sucks the hot ar of the room and this hot aur passes through . the cooling col which is at low temperature say 45″ to 50 F After. Passing throuth the coolng coul. the air becomes cool and this cold ar. is agun crculated in the room. Alter somc time the temperature of the. room becomcs comfortable i.e 70 to 80 F. The flow of this crculating. air is adjusted with the help of a grll The grill is adjusted in such o way that the cold ar is distrbuted in the room evenly.
Purification of Air : In the air conditioned room the room air is circulated agan and again. Now this room air contains small part. of dust and drt and also may have bad oour The dust and drt t are removed with the help of ar-flter. When aur passses throu. filters the dust and dirt particles are trapped in the fiter 1 odour is removed by spraying a perfume or room freshener. In a window type ar conditioncr or oplit type ar conditoner th. filters are placed in tront of the coolng coil These filters are t of cor foamm, Jute or Nylon These filters are cleaned or was a weak In this way the ar in the air conditioned room is purified.
COMFORTABLE TEMPERATURE AND HUMIDITY
An acceptable comfort range of temperature for the human body is 70 F to 80 F or 75 ± 50 F? At this temperature ranging between 700 F to 800 F all human beings feel comfortable. Therefore, in an air-conditioned room the above mentioned temperature is maintained. The moisture present in the air is known as humidlity. If humidity is less the air becomes dry. If humidity is more the air cannot absorb moisture. from the human body. So, the rate of cvaporation is very less. Theretore, the cooling effect is reduced. So, a human being feels uncomfortable. The most comfortable range of humidity for the human body is at 45%. to 55% HUMIDITY or 55 ± 5%. Therefore, in an air-conditioned room, 70 F to S0 Ftemperature and 45% to. 55% humidity is maintained. A psychrometer is a combination of two thermometers mounted on a. base plate fitted with a handle. The base plate can be rotated with the. help of this handle. The thermometers mounted on the base plate are. known as dry bulb and wet bulb thermometers. The dry bulb thermometer is an ordnary thermometer. The thermometer measured by this thermometer is called Dry bulb thermometer (D.B.). The glass bulb of a thermometer is covered by a cloth which is dipped into water so that the bulb is wet. The temperature measured by this thermometer is known as wet-bulb temperature (W.B.). When the psychrometer is rotated for some time the moisture evaporatesi from the wet bulb thermometer. Thus, surface of the thermometer bulb is cooled. So, the reading in wet bulb thermometer is less than the Dry bulb temperature. The diference between the Dry bulb and wet bulb readings depend on the amount of moisture present in the. air-psychrometric chart simplifies the method of measuring properties of ar. The conditions or properties of air are graphically shown in the psychrometeric chart. By locating the intersection point of Dry bulb and wet bulb thermometers in the psychrometeric chart, we can. determine the relative humidity (RH%).