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Air conditioning equipment and applications of air conditioning
- 3. THE COMPONENTS USED FOR THE WORKING OF AN AIR CONDITIONING SYSTEM ARE KNOWN AS AIR CONDITIONING EQUIPMENTS EQUIPMENTS: AIR FILTERS DUST COLLECTORS FANS AND BLOWERS DUCTS GRILLS HEATING COILS COOLING COILS HUMIDIFIERS DEHUMIDIFIERS
- 4. Air filters are used to filter , and remove the impurities present in the atmospheric air and allows purified air in to the air conditioning unit. Air filters are fitted just before the cooling coils
- 5. Dry air filters Wet air filters Viscous air filters Electronic air filters Centrifugal dust collectors or Cyclone air cleaner
- 6. Dry filters or mechanical filters are employed to remove dust particles above certain size. These are constructed from fibrous materials such as felt, fabric, cotton, wool or metallic filters Dry filters are capable of collecting 99% of dust as small as 0.5 micron size. These filters are not suitable to remove smoke and have little effect on small particles. Dry filters may be classified as Throwaway type. Reusable or semipermanent type.
- 7. Wet air filters are generally used with dry and viscous air filters to remove both dust and soluble gases present in the air. These are widely used for industrial applications where both smoke and dust particles are present in the air.
- 8. The viscous filter consists of expended metal frame which is filled with wool or fibre, wire screen etc. These filters have a large dust holding capacity and require less maintenance. However their efficiency is low and are expensive. Viscous filters are suitable for industrial applications where a high degree of atmospheric pollution prevail. The following types of viscous filters are commonly used in air conditioning systems. Throwaway or replacable type — made of cheap material, discarded after a specific period of use. Manual cleaned type — can be cleaned and reused; cleaned filters must be coated with viscous oil. Automatic or self cleaned type.
- 11. fans are used for circulating air with desired speed in air conditioning system FAN: fans is a small capacity air handling equipment BLOWERS: It is a large capacity air handling equipment EXHAUSTER is a fan used to remove air or gases from a place by suction
- 12. SELECTION OF FANS Following factors to be considered for selecting a fan for the given application Method of mounting. Noise level. Nature of load. Static pressure required. Volume of air to be handled Type of air conditioning system
- 13. 1.Axial flow fans: the air flows parallel to the axis of the fan Propeller fans Tube axial fans Vane axial fans 2. Centrifugal fans: The air enters axially in to the fan and discharged radially in to the room
- 14. A propeller fan consists of propeller or a disc type wheel which is mounted on motor shaft. It operates within a mounting ring. The ring surrounding the propeller does not permits the back flow of discharged air. Propeller fans are designed to develop low pressures, and are used only where the resistance to air movement is small. ventilation of attice space and toilets, removal of Cooking odours from kitchen and similar applications
- 15. A tube axial fan consists of an axial flow wheel which is mounted on motor shaft. The assembly of motor and wheel is housed in a cylindrical tube. These fans are more efficient than propeller fans and are capable of handling a wide range of air volumes against medium discharge pressures. The air discharged from the fan follows a spiral path as it leaves the cylindrical housing.
- 16. A vane axial fan consists of an axial flow wheel within a cylinder, integrated with a set of air guide vanes Improved design of the fan eliminates the spiral flow discharge and greatly reduce the turbulence of flow. It is more efficient than the tube axial fan. It is quiet in operation and can be installed in the duct system.
- 17. centrifugal fan blades are mounted in an impeller (or rotor) that rotates within spiral casing. In centrifugal fan the air enters the impeller axially and discharged radially at the periphery. These fans are used for duct air conditioning system. They deliver any quantity (large or small) of air over a greater range of operating pressure.
- 18. The tip of the blade is curved backward with respect to the direction of rotation of the impeller. the blade tip angle is less than 90 degree used in all air conditioners The tip of the blade is curved forward with respect to the direction of rotation of the impeller. the blade tip angle is grater than 90 degree window air conditioners The tip of the blade is straight from the hub and fixed radially with respect to the direction of rotation of the impeller. electric motors for internal cooling
- 19. These are air passages used in the air conditioning systems. Ducts are made of galvanized iron (GI) sheets or tin sheets They are also made of glass fibre and cement asbestos. Ducts can be made circular, rectangular and square shapes. to convey specified rate of air flow to the prescribed location. economical and should occupy less space. should not transmit or generate objectionable noise.
- 20. Supply air duct Return air duct Fresh air duct Low pressure duct Medium pressure duct High pressure duct Low velocity duct High velocity duct
- 21. Loop perimeter system Radial perimeter system Extended plenum system Single duct system Dual duct system Combination of dual duct and induction system.
- 28. Air conditioning requires that right amount of conditioned air be supplied to each room or space to maintain comfort conditions. The distribution system is properly designed and installed for the best results. Good distribution system require duct work with resisters (variable area openings) or grilles .(fixed area openings) to obtain the desired results.
- 29. The air distribution should ensure that The air movement is maintained at a velocity of 7.5 to 9.0 m/min. The variation of temperature should not exceed 20. Air should flow preferably towards the faces of occupants. Should create comfort conditions i.E., Proper combination of temperature, Humidity and air motion in the occupied zone which is normally at 2 m above the floor level.
- 30. Ejection system Downward system Upward system
- 32. In this system uniform air distribution is achieved around the occupied zone of the space. This system is commonly used in offices, commercial complexes, auditoriums, theatres, schools, hospitals etc.
- 33. In this system the supply air enters the space or room to be conditioned through openings near the floor level. The return air goes out from the openings provided either in the ceiling or at the wall near the ceiling height. In this system, the air velocity is properly controlled so that the occupants are not subjected to drafts. This system is used in auditoriums and cinema halls.
- 34. GRILLS: Grill is a perforated covering provided at the end of the duct. The function of the grill is to give a pleasing appearance to the duct. The grill may be fixed or adjustable. DAMPERS: These are used to conttrol the flow of air into the room from supply air outlets. HEATING COILS: These are used to raise the temperature of the conditioned air in an air conditioning system. COOLING COILS: These are used to reduced the temperature of the conditioned air in an air conditioning system.
- 35. HUMIDIFIER Humidifier is a device used to add moisture to the incoming air in an air conditioning system. The process of adding moisture to the air is known as humidification. Dehumidifier: The device used to remove moisture from the air is known as a Dehumidifier. The process of removing moisture from air is known as Dehumidification.
- 37. : Air conditioning is now becoming essential and widely using in domestic commercial, scientific and research applications. Some of the important applications of air conditioning are: 1. Air coolers. 2. Window air conditioners. 3. Summer, Unitary air condition systems. 4. Centralised and unitary air conditioning systems. 5. Cooling towers The refrigerants used in the Air conditioning systems are: (a) Older air conditioners used R-22 (b) Modern air conditioners are using R-410A (c) The newest air conditioners are running on R-32.
- 38. COOLING TOWERS Refrigeration plants with capacity more than 100 TR requires continuous supply of cooling tower for condensing vapour refrigerant circulating in the condenser Some industrial processes require large quantity of cooling water. The location of the Plants may be such that the supply of water from natural sources (sea or river) is not possible and a recirculating system is necessary. A cooling tower is the necessary part of the system. It cools down the water by using atmospheric air A more satisfactory cooling is produced by spraying water into the air rising Upwards. As water falls, air abstracts heat from warm water. As a result, Warm water is cooled and temperature of air is raised. Cooled water is recirculated through the system, Fresh external water is required only to make 1. Natural (atmospheric) draft cooling towers. 2. Mechanical draft cooling towers. a) Induced draft cooling towers. b) Forced draft cooling towers.
- 40. Higher capacity than natural draft cooling towers more efficient, and water can be cooled to a lower temperature than with natural draft cooling tower more compact, for same capacity they need less space can be operated to exact design conditions, and wide range of towers can be designed. However the cost (initial and maintenance) of mechanical draft cooling tower is higher. It needs periodical cleaning due to accumulation of dirt and sludge.
- 41. Air cooler works on the principle of evaporating cooling. It is generally used in dry climates as such it is sometimes called as desert cooler. In this case, water is used as a cooling medium. For better performance pads to be changed every year and water tank should be cleaned from time to time.
- 42. Window air conditioner is basically a room air conditioner installed on a window or wall opening. It works on principle of vapour compression system. The refrigerant used is R - 12 or R - 22. Window air conditioners are available in sizes upto 2 ton capacity. It is employed to condition the air of a given space such as office rooms, saloons, bed rooms, drawing offices etc,
- 43. WINDOW AIR CONDITIONERS ARE DESIGNED AS SPLIT TYPE OR PACKAGED TYPE : In split type air conditioner, the indoor and outdoor sections are separated into two casings or units. Indoor unit consists of evaporator, blower, air filter; grills etc. It is installed inside the room to be conditioned. Outdoor unit consists of compressor, condenser, fan and is installed outside. Since the compressor is installed away from the room, the noise level will be appreciably lower. It is used in bed rooms, design offices etc. : • Packaged air conditioner is a self contained unit with all needed equipment in a single cabinet. The packaged units are available upto 20 ton capacity. The System is usually water cooled. • It is used in restaurants, stores, banks, laboratories, etc.
- 44. Summer air conditioning system is designed to provide comfort conditions during summer seasons. The comfort conditions required inside the room are 240C DBT and 60% relative humidity, irrespective of outdoor conditions. Summer air conditioning may be designed for two climatic conditions (i) Hot and dry outdoor conditions (ii) Hot and humid outdoor conditions.
- 50. • All components of the unit air conditioning system are assembled in the factory itself. The unit air conditioners are usually installed in or immediately adjacent to the space to be conditioned. They are preferred for low capacity requirements. The advantages Of these units are : • moderate initial cost • simple and compact design • flexible in operation, and • can be installed immediately in a given space.
- 51. The unitary air conditioners are available in two types. Window units, Packed units. are self contained units and available upto 2 tons capacity. They are mounted in a window or wall opening. Two or more units are installed if a room is bigger in size. are self contained units and available in bigger capacities ranging from 5 to 20 tons. They are used for restaurants, banks or small offices.
Editor's Notes
- The air to be cleaned is passed through the filtering media. The filter traps the dust particles from the air passing through it. The surface area of the filters should be large to eliminate the pressure drop THIS FILTERS ARE NOT CABABLEOF REMOVING SMOKE OR GASES FROM AIR
- The air to be cleaned is passed through a chamber in which water is sprayed through the nozzles. The dust particles in the wet air gain additional weight and fall down in the chamber
- These materials are coated with sticky oil which capture and holds the dust particles from air that flows through the filter. The dust particles must be uniformly distributed throughout the filter area.
- IT IS MOST EFFICIENT AN ARE USED IN LARGE INDUSTRIAL APPLICATIONS
- IT IS USED AS INDUSTRIAL AIR CLEAR
- Smooth surfaces are desirable for ducts as they offer minimum resistance to the flow of air. The system should also be air tight so that the conditioned air does not leave out to the spaces not being conditioned
- Supply air duct : Carry the conditioned air from the air conditioned equipment to the space or room to be conditioned. Return air duct : Carry the return air from the space or room to the air conditioned equipment for recondi-tioning or recirculation. Fresh air duct Carry the atmospheric air into the system. Low pressure duct • Static pressure is less than 50 mm of water gauge. Medium pressure duct : Static pressure is from 50 mm to 150 mm water gauge. High pressure duct : Static pressure is from 150 mm to 250 mm of water gauge. Low velocity duct . Velocity of air is less than 600 m /min. 8. High velocity duct : Velocity of air is more than 600 m/min.
- perimeter system is shown in Fig. 5.6. A continuous supply duct is installeu around the perimeter of room to form a close loop. The conditioned air from air conditioning unit flows to the perimeter loop through several feeder duct which are evenly placed along the loop. The supply grilles are fitted in the ducts as shown in Fig. 5.7. The return air grilles are located conveniently to collect return air or boxing is provided around the supply air duct to collect return air. This arrangement is used for residential buildings.
- FIG 5.14 : Radial Perimeter Duct System In radial perimeter duct system, the air conditioning unit is placedin the basement.Each supply outlet is connected to the air conditioning plant though separate ducts as shown in the Fig. 5.14. The conditioned air enters the room to be conditioned through the supply outlets fitted closed to the ceiling level. The return air ducts are placed on the bottom side of the inside wall. A lications : Used for multistoried buildings.
- Applications : Used for lodges, hospitals
- Single duct systems are widely used for comfort conditioning both in residential as well as commercial air conditioning.
- respectively. This system is used in applications where different temperatures of air are required at the same time in different rooms as in hospitals. It is achieved by mixing cold air and warm air in a mixing plenum controlled by thermostat.
- The arrangement shown in Fig. 5.18 (a) is a simple system in which the supply air and return air grills are on the same wall at higher level. The air enters the room through supply grill and pass through the space as It is simple and shown in Fig. 5.17 (a) before going out through return air grill. cheaper than the other systems. Fig. 5.17 (b) represents the pan type arrangement in which supply grill and return grill are located in different walls. It is a better system and more uniform distribution is achieved in this arrangement. The arrangement shown in Fig. 5.17 (c) is a further improvement over simple and pan type arrangements. In this case, the supply and return air grilles are combined in one unit. This arrangement is used for heating as well as cooling applications. The arrangement shown in Fig. 5.17 (d) is intended for the rooms where the people are actively moving or doing some exercises. In this arrangement the grilles are located such that air should pass continuously around the occupants. The air is distributed only in the occupied zone which is 2 to 2.5 m above the floor level.
- In this system, air enters the space through the supply grilles or openings located in the ceiling. The return air goes out from the return grilles or openings in the floor or on the walls near the floor level. In this system uniform air distribution is achieved around the occupied zone of the space. This system is commonly used in offices, commercial complexes, auditoriums, theatres, schools, hospitals etc.
- In this system the supply air enters the space or room to be conditioned through openings near the floor level. The return air goes out from the openings provided either in the ceiling or at the wall near the ceiling height. In this system, the air velocity is properly controlled so that the occupants are not subjected to drafts. This system is used in auditoriums and cinema halls.
- The temperature of air is decreased (i.e. sensible heat is removed) by the water when air is brought in contact with the water. Water absorbs heat from the air and evaporates. To compensate loss of water due to evaporation, make up of water is added. The components of air cooler are shown in the Fig. 5.20. The basic components are fan, water pump and pads through which air enters the cooler. The electrical driven pump pumps the water from the bottom tank to the top headers. The headers have holes through which water trickles down and pass through pads fitted on three sides of the cooler. Air sucked through pads from three sides gets cooled. The cool air is discharged by the motor driven fan into the room or space to be cooled. The direction of air flow can be adjusted with the help Of grills fitted on the discharge side of the cooler.
- An electric motor drives the fan to circulate air through condenser coil and runs a blower. Blower sucks air through the filter and forces it through the evaporator coil which cools as well as dehumidifies the air. The conditioned air is circulated through the room or the space to be conditioned. Dampers are used for the appropriate air distribution in the room. It is also provided with thermostat to maintain the desired temperature by means of an on-off control of the compressor.
- Window air conditioners are designed as split type or packaged type.
- summer air conditioning system for hot and dry outdoor conditions, say 400 DBT and 20% RH is illustrated in Fig. 5.23.1 (a). For dry outdoor conditions i.e., humidity is not high, there is no need to dehumidify the air. Air is simply cooled to desired temperature by passing through the cooling coil (sensible cooling). A humidifier is provided to add certain amount of moisture. An eliminator provided next to the humidifier absorbs water particles from the air.
- SUmrner air conditioning system for hot and humid conditions, say 400C and 75% RH is illustrated in Fig. 5.23.2 For wet outdoor conditions i.e., humidity
- In winter air conditioning the air is heated and humidified to achieve designed conditions. Winter air conditioning system is shown in the Fig. 5.23.3 (a). Atmospheric air is passed through the filter to remove dirt and impurities. It is heated in a preheating coil to prevent possible freezing of water in the air during humidification. Then the air is passed through adiabatic humidifier where moisture content in the air is increased. The air is passed through the eliminator to remove suspended water particles in air. The air is finally reheated to bring the designed DBT and RI-I. The conditioned air is supplied to the conditioned space. Some of this air is recirculated and mixed with fresh air. The remaining air is exhausted to the atmosphere.
- This system is composed of heating and cooling equipment with automatic control to produce desired conditions irrespective of climatic conditions. Year round air conditioning system is shown in Fig. 523.4. In winter heating and humidification of air is achieved by the heating coils and humidifier, and cooling coil (evaporating coil of refrigerating system) inoperative. The conditioned air is distributed into the space o e con 1 lone Silencer is provided to keep the noise at desired level. In summer cooling and dehumidification is achieved by a cooling coil whose DBT is below the dew point temperature of entering air.
- In central air conditioning system all the major components are located at the central place, away from the area to be conditioned. The conditioned air is supplied to different rooms by ducks. The exhaust air can be returned and partly reused with obvious savings in heating and refrigeration.