Government Polytechnic Gandhinagar Consumer Electronics (3361102) Semester 6 EXPERIMENT NO: 7 AIM: TO DEMONSTRATE OPERATION OF AIR CONDITIONER. THEORY: INTRODUCTION: To an average person, air conditioning simply means “ the cooling of air”. This definition is neither sufficiently useful not accurate. To be more precise air conditioning is the process of treating air in internal environment to establish and maintain required standards of temperature, humidity cleanness and motion. Most air conditioning systems are used for either human comfort or process control. Following are the main parameters for the air conditioning: (1) TEMPERATURE: Air temperature is controlled by heating or cooling the air. Cooling technically means the removal of heat ,in contrast to heating, the addition of heat. (2) HUMIDITY: Air humidity, the water vapour content of the air , is controlled by adding or removing water vapour from the air. (3) CLEANLINESS: Air cleanliness or air quality is controlled by either filtration, the removal of undesirable contaminants using filter or by ventilation, the introduction of outside air into the space which dilutes the concentration of contaminants. (4) MOTION: Air motion refers to air velocity and to where the air is distributed .It is controlled by appropriate air distributing equipment. Air system use air to heat or cool rooms. They may also have the added capability of controlling humidity and furnishing outdoor ventilation. Air is heated at the heat source(1), such as a furnace. It may also be a coil hot water , or steam, heated by a boiler. The heated air is circulated by a fan (2) and travels to each room through supply air ducts (3) The supply air enters the room through outlets called air diffusers or registers (4) that are designed to proper air distribution. When the warmed supply air enters the room, the room is heated. The humidifier (10) may also included to main a comfortable room humidity in where. In summer air is cooled when it flows over a cooling source (5), usually a coil of tubing containing a fluid cooled by refrigeration equipments 1

Government Polytechnic Gandhinagar Consumer Electronics (3361102) Semester 6 Because a room’s size is fixed, the same volume of air that enters the room must also exit .This is usually accomplished by return air ducts (6). The air is then heated and cooled again and recirculated. An outdoor air intake duct (7) may be provided for introducing fresh outdoors air for increased air quality. Similarly , same volume of air must be exhausted(8).Prevision may be made for cleaning the air with air filters(9) and humidifying the air. Air conditioning also involves more thanlowering the air temperature. It includes dehumidifying, cleaning (filtering), and circulatingthe air. Good air conditioning systems perform all of these functions,although most people focus on the “cool” concept. (In the broadest sense of the term, air conditioning also means heating, humidification, and ventilation. If the outdoor temperature is 70°F at night and all the windows in the house areopen, the indoor and outdoor temperatures will both be about 70°F. As the suncomes up, the outdoor temperature may rise to 85°F or 90°F. Because of shading,thermal mass, and so on, the house will not heat up as quickly as the outdoors, but it will eventually get just as hot as it is outside. The goal is to keep it more comfortableinside the house than it is outside.

AIR CONDITIONING—SCHEMATIC OF SYSTEM To recap, we can think about a cold, low-pressure liquid entering an evaporator coil.The warm house air gets blown across the cool coil by the furnace fan. The houseair gives up its heat to the cold liquid, boiling the liquid off into a relatively coolgas. The cooled air that passed over the coil is distributed through the house.Outdoors The cool gas in the pipe moves outside and is squeezed by the compressor intoa high-temperature, high-pressure gas. This hot gas passes through the condensercoil. Blowing outside air across the condenser cools the hot gas inside,

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Government Polytechnic Gandhinagar Consumer Electronics (3361102) Semester 6 releasing heatto the outdoor air that has been stolen from the house. As the gas is cooled, it condensesback to a liquid.

This hot liquid gets pushed back into the house. Just before it goes into the evaporatorcoil, it goes through the bottleneck (capillary tube or expansion valve), whichlowers the pressure and temperature dramatically. Again, we have the cold liquidentering the evaporator coil, starting the process over. Figure 1.9 summarize the entireprocess. You can think of air conditioning as a sponge. The sponge contains heat fromthe house. We squeeze (compress) it to get rid of the water (heat) outside then let itexpand (expansion device) as it comes inside so we can soak up more water (heat). When an air conditioner is running properly at steady state, the house air temperaturedrops by 15°F to 20°F (some say 14°F to 22°F) as it moves across the evaporatorcoil. For example, 75°F house air would come out of the evaporator coil at 55°Fto 60°F.One can also make sure that the air coming off the condenser fan outside iswarmer than the outside air. You can sense this with your hand. Let’s look at the cooling capacity. A TON OF ICE The cooling capacity of air conditioners is usually measured in tons. One tonequals 12,000 BTU (British Thermal Units) per hour (Figure 1.15). The term one toncomes from the amount of heat required to melt a block of ice that weighs one ton. FACTORS AFFECTING The amount of cooling required depends on a large number of factors. These Cooling Load include the outdoor temperature; the outdoor humidity; the level of insulation in thehouse; the amount of air leakage in the house; the amount of southern-, eastern-, andwesternfacing glass in the house; whether this glass is single, double, or triple glazed;whether the glass is

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Government Polytechnic Gandhinagar Consumer Electronics (3361102) Semester 6 a low emissivity glass; and whether window treatments (curtainsor blinds) are kept closed or open. Other factors include the amount of shading CONCLUSION:

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