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air conditioning

  1. 1. Air-conditioning Ar. Abhinav Srivastav Assistant Professor B.Arch, M.Tech (IIT-R) Presented By-
  2. 2. Questions? Air-conditioning • Explain with sketches the working of basic air-conditioning system. List the various types of air-conditioner. • Define following term in connection with air conditioning. Sensible heat Latent heat Ton of Refrigeration • What is Air-conditioning? Why it is necessary? • Explain the basic consideration of an a.c ducting system and important conditions for the effective functioning of it.
  3. 3. OUTLINE- • History • Are you comfortable? • What is air-conditioning? • Air-condition capacity-the “ton” • Ozone depleting substances • Refrigeration cycle • Types of air-conditioning • Window Air-conditioners • Split Air-conditioners • Packaged Air-conditioners • Central Air-conditioners • Sample Drawings • References Air-conditioning
  4. 4. History Air-conditioning In 1902, the first modern electrical air conditioning unit was invented by Willis Carrier in Buffalo, New York
  5. 5. History Air-conditioning Centre Georges Pompidou Richard Rogers and Renzo Piano
  6. 6. Are you comfortable? Air-conditioning What we say about discomfort What the air conditioner does It is too warm The air is cooled It is too cold The air is warmed It is too humid Excess moisture in the air is removed It is too stuffy The conditioned air is circulated gently It is dusty or smoky The air is filtered There is an unpleasant odour The bad air is exhausted and fresh air is taken in The air is stale The air is mixed with fresh outdoor air
  7. 7. What is Air-conditioning? Air-conditioning Air-conditioning is defined as a process which cools (or heats), cleans, circulates, freshness air and control its moisture simultaneously. There are two types of ‘Heat’: Sensible Heat and Latent Heat. ‘Sensible Heat’ is any heat that raises the temperature but not the moisture content of the substance. This is our regular and familiar every day heat. Because it raises the temperature it can be detected by the senses, and this in fact, is why its is called Sensible heat. ‘Latent Heat’ is the tricky one. When we talk of Latent Heat we mean ‘Latent Heat of Vaporization’. It is that heat required to transform a liquid to vapour.
  8. 8. Air-conditioning Air-conditioning capacity-the ‘TON’ Most of us have heard about the Ton in connection with Heat Load or capacity of Air-conditioning equipment. The Ton (TR) in refrigeration & air-conditioning is a unit indicating a certain Quantity of Heat. This “Quantity of Heat” is different from temperature which only says how hot the substance is but not how much heat it contains. The two most common units for stating the heat quantity are the British thermal unit(Btu) and the Calorie (cal). • The Btu is the quantity of heat needed to raise the temperature of 1 1lb. Of water by1º Fahrenheit. • The Calorie is the metric unit of heat quantity. It is the heat needed to raise the temperature of 1gram of water by 1º Celsius. Since a calorie is very small measurement, it is practical to use thousand calories as the unit for air- conditioning and it is expressed as Kilo Calorie (K Cal) 1Ton Refrigeration = 12000Btu/hr or 3000K Cal/hr
  9. 9. Air-conditioning Ozone depleting substances  CFC Free equipments (Chillers, AC & Kitchen equipments)
  10. 10. Refrigeration Cycle Air-conditioning Now that we have discussed “Heat” let us talk about the principle at work in air- conditioning. The core concept to understand is Evaporation. Remember how cold your skin felt when dabbed by liquid spirit at a doctor’s clinic before an injection? It felt cold because the spirit evaporated (changed from liquid state to the vapour state) very rapidly. And when it evaporated it needed heat to change its state. Where did this heat come from? It came from the liquid itself, and your skin, with which it was in contact. Equipment used to produce cooling: Now that we have seen the process by which cooling takes place, and examined the nature of heat and humidity, let us briefly look at the main equipment used to produce the effects we require.
  11. 11. Refrigeration Cycle Air-conditioning The Refrigeration cycle
  12. 12. Refrigeration Cycle Air-conditioning The Compressor: Under atmospheric temperature and pressure the refrigerant is in gaseous form. We learnt that cooling takes place when liquids evaporate to become gas. Therefore we must first transform the refrigerant gas into liquid form. Most gasses can be made into the liquid form by raising its pressure (and cooling it, which is handled by the condenser). The equipment that increases the pressure of the gas by compressing it, is called the Compressor. The Condenser: During compression however the refrigerant becomes hot. This is because of two reasons: a) Because of the work done on it (remember how warm the hand pump became when pumping air into your bicyle tyres?) and b) Because the refrigerant is converted from gas to liquid releasing its latent heat. This heat has to be removed to enable the gas to condense into a liquid easily. The equipment that removes the heat is called the Condenser.
  13. 13. Refrigeration Cycle Air-conditioning The Evaporator (‘Cooling Coil’ to most of us): From the condenser we now have the liquid refrigerant ready to go to work. This refrigerant can remove heat when it starts evaporating The liquid refrigerant from the condenser is injected through a metering device called the capillary or expansion valve into the cooling coil which is a bundle of tubes. End of cycle and beginning of the next one: Having done this, the refrigerant is back into the gaseous form. It is sucked into the compressor where it will be compressed again for the next refrigeration cycle.
  14. 14. Types of Air-conditioning Air-conditioning Air-conditioning Non-Central AC products Central AC system Split ACsWindow ACs Ceiling mountedWall MountedFloor Mounted Exposed type Concealed type Semi- concealed(cassete) type
  15. 15. Air-conditioning Air-conditioning Non-Central AC products Central AC system Types of Air-conditioning Ductable Packaged ACs Central Plants Floor-mounted Packaged Air- conditioner Air-cooled Ducted Splits Air-cooled Water-cooled
  16. 16. Air-conditioning Types of Air-conditioning Air-conditioning Non-Central AC products Central AC system Central Plants Chilled Water SystemDX SystemVariable Refrigerant Flow System Vapour Compression Units Vapour Absorption Units Direct Fired Hot Water Fired Stream Fired Single & 2 StageScrew type units air & water cooled Centrifugal units, water cooled only Reciprocating units,air & water cooled
  17. 17. Air-conditioning Window Air-conditioners Room Air conditioners are familiar to most of us. These ubiquitous machines can be seen mounted in windows and therefore are also referred to as ‘Window Air conditioners’. In Window Air conditioners, the compressor, condenser- fan, condenser and evaporator are all enclosed in a single cabinet. The unit is to be installed in a wooden frame either in a window or in a hole in the wall.
  18. 18. Air-conditioning Window Air-conditioners The air being blown through the condenser must pass freely through without restriction. We must therefore make sure that the condenser is not obstructed (for example by a neighboring wall). These air conditioners come in cooling capacities from 0.5 to 2 tons in various tonnages, adequate for a room between 5 and 20 square metres in size. Larger spaces may be handled by using multiple units of this type. While Window Air conditioners are economical and most convenient to install, they could be noisy for some applications.
  19. 19. Air-conditioning Window Air-conditioners Positives: • inexpensive • Easy to install • Each room can operate its AC independently • Simple, low-cost, service and maintenance • Running costs are low Negatives: • Tonnages are limited (1 to 2 TR typically) • Noisier (than other types of ACs) • A window is required, and blocked, by the AC • No constant fresh air circulation Keeping the above attributes in view, Window ACs are useful in: • Homes • Small office executive cabins • Small shops.
  20. 20. Air-conditioning Split Air-conditioners As the name implies, the Split Air conditioner is split int. two basic components, the Indoor unit and the Outdoor unit These two units are connected by refrigeration tubing and electrical wires that can pass through a hole in the wall barely 10 cms in diameter. The outdoor unit houses the compressor, condenser and the condenser fan. The indoor unit consists of the evaporator (cooling coil) and the evaporator blower. Since the noisier components are outside the building, the conditioned space is much quieter. Though Split Airconditioners are more expensive than the Window Mounted type, they are preferred for their low noise levels. There are also situations where it is not possible to mount a window airconditioner because of obstructions from neighbouring walls or non-availability of a suitable window. In such cases the Split Airconditioner is used because the outdoor unit can be mounted on the roof or on a ledge some distance away from the room to be airconditioned.
  21. 21. Air-conditioning Split Air-conditioners Types of Indoor Units While the outdoor units of split airconditioners are all similar, indoor units are available in different types to suit the needs of the airconditioned space. The types of indoor units are: Floor-mounted:. Such units are mounted on the floor, may be on a platform. Air throw is upwards. Since floor-space is at a premium, and floor-mounted units occupy real- estate, such indoor units are not very widely used these days Floor mounted split ac
  22. 22. Air-conditioning Split Air-conditioners High Wall Splits: Such units are fixed on the wall, at a height of about 2.5 metres from the floor. The controls are generally operated either by a corded or cordless remote control unit. Because it is mounted on the wall it is preferred for rooms having less floor space. This model is widely used for domestic and commercial applications. High wall split
  23. 23. Air-conditioning Split Air-conditioners Ceiling-mounted: Ceiling mounted split airconditioners are designed to be suspended from the main ceiling. They are available in three models: (A) Exposed (B) Concealed (C) Semi concealed (cassette) A. Exposed These units are fixed directly to the ceiling and are visible. The unit is similar to the Floor mounted type. They are easy to mount and are preferred in commercial areas or offices that do not have a false ceiling. Ceiling mounted (exposed)
  24. 24. Air-conditioning Split Air-conditioners B.Concealed These units are also mounted on the ceiling but are designed to be hidden. They are generally concealed by a paneled box or false ceiling. These units are suitable for commercial areas where the interior designer requires the air-conditioning equipment to be concealed so as not to interface with the aesthetics. You will find such units working in restaurants and offices. Ceiling mounted (concealed)
  25. 25. Air-conditioning Split Air-conditioners C. Cassette Cassette type indoor units are mounted above the false ceiling in such a way that the outlet grill of the unit is flush with the bottom of the false ceiling. While the other types of indoor units provide for condensate draining by gravity the same is not possible for the cassette type. The cassette also has the advantage that it can be placed directly above specific areas that require airconditioning. Multiple units can aircondition larger spaces. Ceiling mounted
  26. 26. Air-conditioning Split Air-conditioners Drainage of condensate water When the air around the evaporator is cooled, the moisture in the air accumulates as water under the evaporator. This happens because the cold air cannot hold as much water vapour as it held when it was warmer. You experience the same phenomenon when a small puddle of water accumulates under a chilled glass of water. This water referred to as ‘condensate’ is collected in a pan under the evaporator and must be removed from the conditioned space. Therefore, wherever indoor units are mounted there must be a gently sloping drain tube to carry this condensate water away from the room. If the water is not drained properly it may collect in the drain pan until it overflows and drips into the room.
  27. 27. Air-conditioning Split Air-conditioners Positives: • Quieter than Window ACs • Available in larger tonnages (even upto 5 TR in Turbo Splits) • Do not require, or block, a window • May be used as ‘multiple’ units to cool 2 or 3 adjacent rooms • May suit the interiors better • May be found aesthetically better suited Negatives: • Costlier than Window Acs • Require space outside the room for the outdoor unit. • Some piping and cabling necessary • Do not provide for fresh air intake Keeping the above attributes in view, Split ACs are useful in: • Senior executive cabins • Professionally positioned small or mid-sized showrooms • Up-market homes • Small clinics, ATMs, etc.
  28. 28. Air-conditioning Packaged Air-conditioners • The window and split air conditioners are usually used for the small air conditioning capacities up to 5 tons. • The central air conditioning systems are used for where the cooling loads extend beyond 20 tons. the packaged air conditioners are used for the cooling capacities in between these two extremes. AVAILABLE IN THE FIXED RATED CAPACITIES OF 3, 5, 7, 10 AND 15 TONS.
  29. 29. Air-conditioning Packaged Air-conditioners Packaged air conditioners with water cooled condenser •The condenser is cooled by the water. •The condenser is of shell and tube type, with refrigerant flowing along the tube side and the cooling water flowing along the shell side. •The water has to be supplied continuously in these systems. •This whole packaged air conditioning unit externally looks like a box with the control panel located externally. •In the packaged units with the water cooled condenser, the compressor is located at the bottom along with the condenser. •Above these components the evaporator or the cooling coil is located. •From the top of the package air conditioners the duct comes out that extends to the various rooms that are to be cooled.
  30. 30. Air-conditioning Packaged Air-conditioners Packaged air conditioners with air cooled condensers • in this conditioners the condenser is cooled by the atmospheric air. • there is an outdoor unit that comprises of the important components like the compressor, condenser. • the outdoor unit can be kept on the terrace or any other open place where the free flow of the atmospheric air is available. • the fan located inside this unit sucks the outside air and blows it over the condenser coil cooling it in the process. • the condenser coil is made up of several turns of the copper tubing. • the packaged ac with the air cooled condensers are used more commonly than the ones with water cooled condensers. the cooling unit comprising of the expansion valve, evaporator, the air handling blower and the filter are located on the floor or hanged to the ceiling. the ducts coming from the cooling unit are connected to the various rooms that are to be cooled.
  31. 31. Air-conditioning Central Air-conditioners Introduction • Central air conditioning, commonly is an air conditioning system which uses ducts to distribute cooled and/or dehumidified air to more than one room, or uses pipes to distribute chilled water to heat exchangers in more than one room. • Commercial air conditioning is for companies or larger buildings, such as hospitals, restaurants, hotels and other places that are multi-leveled, have a certain amount of square footage and are visited by the public or have many employees that require a more intricate air conditioning system.
  32. 32. Air-conditioning Central Air-conditioners •When the air handling unit turns on, room air is drawn in from various parts of the building through return-air ducts. This air is pulled through a filter where airborne particles such as dust and lint are removed. Sophisticated filters may remove microscopic pollutants as well. The filtered air is routed to air supply ductwork that carries it back to rooms. Whenever the air conditioner is running, this cycle repeats continually. Because the central air conditioning unit is located outside the home, it offers a lower level of indoor noise than a free-standing air conditioning unit.
  33. 33. Air-conditioning Central Air-conditioners Components • Refrigerant • Evaporator/Chiller • Compressor • Condenser • Expansion Device • Receiver
  34. 34. Air-conditioning Central Air-conditioners Air handling unit (AHU) An air handler, or air handling unit (AHU), is a device used to condition and circulate air as part of a heating, ventilating, and air-conditioning (HVAC) system. Usually, an air handler is a large metal box containing a blower, heating and/or cooling elements, filter racks or chambers, sound attenuators, and dampers. Air handlers usually connect to ductwork that distributes the conditioned air through the building, and returns it to the AHU. Sometimes AHUs discharge (supply) and admit (return) air directly to and from the space served, without ductwork. Small air handlers, for local use, are called terminal units, and may only include an air filter, coil, and blower; these simple terminal units are called blower coils or fan coil units. An air handler designed for outdoor use, typically on roofs, is known as a packaged unit (PU) or rooftop unit (RTU).
  35. 35. Air-conditioning Central Air-conditioners Ducting
  36. 36. Air-conditioning Central Air-conditioners Duct design objectives 1.To provide conditioned air to meet all rooms heating & cooling requirements. 2.Is properly sized so that the pressure drop across the air handler within the manufacturer and design specifications. 3.Is properly sealed so that any leakage or entrance of any polluted air is avoided. 4.Has balanced air supply and return air flow so as to maintain a neutral pressure in house. 5.Minimizes duct air temperature gains or losses between the air handler and supply outlets, and between the return register and air handler.
  37. 37. Air-conditioning Central Air-conditioners • Square Ductwork – Most common – Low height • Round Ductwork – Less Expensive – Easy to Install – Lower static pressure – Taller than Rectangular – Higher pressure – Less Sound • Oval Ductwork – Same advantages of round – Height similar to rectangular – More expensive than rectangular Metal Ducts
  38. 38. Air-conditioning Central Air-conditioners Fabric Ducts • Great for certain applications – Gyms – Pools – Manufacturing – Spokane Science Museum • Advantages – Great Diffusion – Easily Cleaned – Fun – Same cost as metal
  39. 39. Air-conditioning Central Air-conditioners Extended Plenum System Simple to work with Relatively long runs of one size rectangular trunk duct Ease of fabrication and installation With centrally located equipment balanced air flow is attained System readily adapts to most type of spaces Suited for basements, crawl spaces, attics & dropped ceilings Smaller branch ducts can be installed in joist & stud spaces Low cost system
  40. 40. Air-conditioning Central Air-conditioners
  41. 41. Air-conditioning Central Air-conditioners Radial System • Radial System has the following characteristics: • Simplest duct system to install • Branch ducts run in direct route from furnace plenum to outlet • Finished appearance of ductwork is not considered • Equipment if centrally located then a best advantage • Economical when applied to single-story rectangular spaces • Air flow in the branch ducts is fairly uniform • Installed in unused crawl spaces and attics • Cost saving through reduced materials inventory
  42. 42. Air-conditioning Central Air-conditioners
  43. 43. Air-conditioning Central Air-conditioners Reducing Trunk System Reducing Trunk System has the following characteristics: • Most difficult to design and fabricate but well balanced • Each system is engineered for a specific application • Ultimate system for exacting performance if properly designed • Fittings & method of takeoff minimize air turbulence and noise • Suitable for similar applications as extended-plenum systems • Well-suited where equipment is located at one end • Duct work can be easily concealed • Most costliest than other ducts because of custom work
  44. 44. Air-conditioning Central Air-conditioners
  45. 45. Air-conditioning Central Air-conditioners Gravity System Gravity System has the following characteristics: • Mostly of radial pattern with short supply ducts • Ducts terminate at floor registers at inside walls • Operation is extremely quiet since no blower is used • Substantial fluctuation in room temperatures • Best suited for one-story houses with a basement • Equipment's should be centrally located in the basement • Impossible to conceal because of large sloping ducts • Somewhat more costly than standard radial systems
  46. 46. Air-conditioning Central Air-conditioners
  47. 47. Air-conditioning Air distributors • Grilles, Registers – Many options – GU Russell Theatre Return Grille • Return Plenum – Extra cost for plenum rated cable is less than cost of return ductwork – No Combustables
  48. 48. Air-conditioning Central Air-conditioners Cooling towers A cooling tower is an equipment used to reduce the temperature of a water stream by extracting heat from water and emitting it to the atmosphere. Cooling towers make use of evaporation whereby some of the water is evaporated into a moving air stream and subsequently discharged into the atmosphere. As a result, the remainder of the water is cooled down significantly They all work on the same principle: A cooling tower blows air through a stream of water so that some of the water evaporates. Generally, the water trickles through a thick sheet of open plastic mesh. Air blows through the mesh at right angles to the water flow. The evaporation cools the stream of water. Because some of the water is lost to evaporation, the cooling tower constantly adds water to the system to make up the difference The amount of cooling that you get from a cooling tower depends on the relative humidity of the air and the barometric pressure.
  49. 49. Air-conditioning Central Air-conditioners The basic components of a cooling tower include the frame and casing, fill, cold-water basin , drift eliminators, air inlet, louvers, nozzles and fans. • Frame and casing. Most towers have structural frames that support the exterior enclosures (casings), motors, fans, and other components. • Fill. Most towers employ fills (made of plastic or wood) to facilitate heat transfer by maximizing water and air contact. Water falls over successive layers of horizontal splash bars, continuously breaking into smaller droplets, while also wetting the fill surface. • Cold-water basin. The cold-water basin is located at or near the bottom of the tower, and it receives the cooled water that flows down through the tower and fill. • Drift eliminators. These capture water droplets entrapped in the air stream that otherwise would be lost to the atmosphere. • Air inlet. This is the point of entry for the air entering a tower. The inlet may take up an entire side of a tower (cross-flow design) or be located low on the side or the bottom of the tower (counter-flow design). • Louvers. Generally, cross-flow towers have inlet louvers. The purpose of louvers is to equalize air flow into the fill and retain the water within the tower. Many counter flow tower designs do not require louvers. • Nozzles. These spray water to wet the fill. Uniform water distribution at the top of the fill is essential to achieve proper wetting of the entire fill surface. Nozzles can either be fixed and spray in a round or square patterns
  50. 50. Air-conditioning Sample Drawings
  51. 51. Air-conditioning Sample Drawings
  52. 52. Air-conditioning Sample Drawings
  53. 53. Air-conditioning Manufacturer • Blue Star • O-General • Voltas • Mitsubishi • Daikin • Hitachi • Carrier • Sharp • L.G • Whirlpool Air-conditioning
  54. 54. References • The Blue Star Guide to Comfort Airconditioning • Prof. Subhash M.Patil, Building Services • Arthur A.Bell, HVAC Equations, Data and Rules of Thumb • ISHRAE 2017 guidelines IS Air-conditioning
  55. 55. Thanks Air-conditioning

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