Mechanical Ventilation and Cooling Systems PDF

Mechanical Ventilation , Heating and Cooli-ng Systems 1 One of the most design requirements- A lot of Architects using the Ventilation as a - design idea like Norman Foster : It is essential in the spaces- where there are heat or humidity or steam* * Internal spaces that ventilation don’t reach...

Mechanical Ventilation , Heating and Cooli-ng Systems 1 One of the most design requirements- A lot of Architects using the Ventilation as a - design idea like Norman Foster : It is essential in the spaces- where there are heat or humidity or steam* * Internal spaces that ventilation don’t reach *Lack in the amount of oxygen * A non-desirable odors in a vacuum 2  -Ventilating (the V in HVAC) is the process of "changing" or replacing air in any space to provide high indoor air quality (i.e. to control temperature, replenish oxygen, or remove moisture, odors, smoke, heat, dust, airborne bacteria, and carbon dioxide). Ventilation is used to remove unpleasant smells and excessive moisture, introduce outside air, to keep interior building air circulating, and to prevent stagnation of the interior air.  Air conditioning (often referred to as aircon, AC or A/C) is the process of altering the properties of air (primarily temperature and humidity) to more favourable conditions. More generally, air conditioning can refer to any form of technological cooling, heating, 3  Ventilation includes both the exchange of air to the outside as well as circulation of air within the building. It is one of the most important factors for maintaining acceptable indoor air quality in buildings. Methods for ventilating a building may be divided into mechanical/forced and natural types ‫الفك ره ھي تحري ك وخلخل ة الھ واء داخ ل الفراغ ات‬ ‫المعمارية عن طريق خلق مناطق ذات ضغط مرتفع‬ ‫يتح رك منھ ا الھ واء الى المن اطق ذات الض غط‬.‫المنخفض فينتج عن ذلك حركة الھواء‬ 4 Natural ventilation is the ventilation of a building with outside air without the use of a fan or other mechanical system Techniques for Natural ventilation: 1- Orientation of the building: a-There must be a study on site well to achieve the best ventilation B-The best ventilation comes from north side C-The area for the north openings should be larger than the other openings D- minimize the number and the area for the south openings 5 2- Shape of building and openings: 1-The openings are high to introduce greater amount of air 2-There are two openings in the building, one for entering air and one for leaving 3-The area of the opening entering the air is small, while the other for air leaving is big. 4- The site and area for the openings are very important in building ventilation 6 3-Ventilation using shadow This can be achieved by making the buildings close to each other and different in height and size. The large one make shadow on the smaller 4- Make the buildings around courtyards 5- Using the presence of trees, pools of water to be in the face of wind 7 Transmission of air in architectural spaces: 1- The entry and exit of the air occurs naturally 2- The entry of the air occurs naturally and the exist is mechanically 3- The entry of the air occurs mechanically and the exist is naturally 4- The entry and exit of the air occurs mechanically 8 1-The entry and exit of the air occurs naturally (by openings of the doors and windows) The main idea is the difference in the temperatures and the air currents The entry and exist of the air is done through the architectural openings in spaces This way used in residential buildings 9 2-The entry of the air occurs naturally and the exist is mechanically (by using fans): According to the negative and positive pressure theory, Fans used to pull the air from the architectural space that cause decrease in the internal pressure (-) which will be less than the (+) atmospheric pressure, that cause entry of the air from the openings. This way is used in the kitchens, bathrooms, ….. That produce non-desirable odors, steam, gases. 10 3-The entry of the air occurs mechanically and the exist is naturally According to the negative and positive pressure theory, Fans used to pull the air to the architectural space that cause increase in the internal pressure (+) which will be more than the (-) atmospheric pressure, that cause exist of the air from the openings due to pressure difference. This way is used in the elevators. 11 4- The entry and exit of the air occurs mechanically (by using fans): -According to the negative and positive pressure theory, Fans used to pull the air to the architectural space and remove it by other fans. -This way used to ensure that the rate of air flow is regular and also the pressure is constant -This way used in the closed space (building under the ground like mines) 12 Mechanical Ventilation: or "forced" ventilation is used to control indoor air quality. Excess humidity, odors, and contaminants can often be controlled via dilution or replacement with outside air. However, in humid climates much energy is required to remove excess moisture from ventilation air. 13 ‫انواع التھوية الميكانيكية ودور المھندس المعماري‬ ‫‪14‬‬ 15 16 ‫دور المعماري‬ ‫‪17‬‬ ‫مكونات نظم التھوية المكيانيكية ذات االنتزاع‬ ‫المركزي‬ ‫‪18‬‬ 19 20 21 22 23 24 25 26 27 28 29 :Architectural spaces in horizontal direction are horizontal spaces that designed in cooperation between architectural and mechanical engineer through interior.decoration work Architectural spaces in vertical direction are vertical spaces that designed in cooperation between architectural and mechanical engineer In most cases, we put these spaces in the central areas of the project. (besides walls and columns that continue in the vertical direction ex:elevators 30 Made of galvanized tin or cardboard-1 Determine the areas and dimensions of these -2 : Grille depend on a)The amount of the air that should be entered b) Losses due to friction cased by air movement inside grille c)Speed of air inside grille 31 32 33 AIR-CONDITIONING SYSTEMS AND APPLICATIONS 34 AIR-CONDITIONING SYSTEMS Earliest air conditioning system used only for heating (winter) Provided heated air for comfort- -Provided ventilation Using simple ductwork and control- In later time , addition of cooling, dehumidification, and/or humidification provide all year round air conditioning 35 Air conditioning (often referred to as aircon, AC or A/C) is the process of altering the properties of air (primarily temperature and humidity) to more favourable conditions. More generally, air conditioning can refer to any form of cooling, heating technological Control of temperature, moisture, cleanliness, air quality, and air circulation in space as required by occupants, process, or product 36 An air conditioner is a major or home appliance, system, or mechanism designed to change the air temperature and humidity within an area (used for cooling and sometimes heating depending on the air properties at a given time). The cooling is typically done using a simple refrigeration cycle, but sometimes evaporation is used, commonly for comfort cooling in buildings and motor vehicles. In construction, a complete system of heating, ventilation and air conditioning is referred to as " HVAC". 37  Goal COMFORT FOR THE HUMAN  People need 1.2 kg of water per day , 1.7 kg of food and 16 kg of air. They can be dispensed with food and water for a few days but not releasing the air for more than ten minutes. 38 Air Conditioning systems effects on: 1-Air temperature 2- Air humidity 3- Air motion 4- ventilation 5-purity of the air 6- sound level 39 :Benefits of Air condition 1- Residential buildings 2- Restaurants and places of entertainment 3-public places 4- large buildings 5-means of transportation 6-Industry 7- Pharmacies 8-imaging tools 40 Cooling systems 41 42 43 44 45 46 47 :PRINCIPLES IN COOLING THEORY Liquids absorb heat when changed from liquid to gas)1 )1.Gases give off heat when changed from gas to liquid )2 Fluids change their condition at constant pressure and temperature )3 The heat transferred from the body that has a higher temperature to the )4 one with lower temperature Metal parts of the evaporator and condenser should be good conducted for )5 heat and we should chose the metal that doesn’t react with the cooling.medium such as yellow and red copper, aluminum 48 COOLING CYCLE 49 For an air conditioning system to operate with economy, the refrigerant must be used.repeatedly For this reason, all air conditioners use the same cycle of compression, condensation, expansion, and evaporation in a closed circuit. The same refrigerant is used to move the heat from one area, to cool this area, and to expel this heat in another area 50 The refrigerant comes into the compressor as a-1 low-pressure gas, it is compressed and then moves.out of the compressor as a high-pressure gas The gas then flows to the condenser. Here the-2 gas condenses to a liquid, and gives off its heat to.the outside air The liquid then moves to the expansion valve-3 under high pressure. This valve restricts the flow of the fluid, and lowers its pressure as it leaves the.expansion valve The low-pressure liquid then moves to the-4 evaporator, where heat from the inside air is.absorbed and changes it from a liquid to a gas As a hot low-pressure gas, the refrigerant moves 51 to the compressor where the entire cycle is.repeated 52 53 ‫نظام وحدة الشباك‬ ‫‪Window Unit‬‬ ‫‪54‬‬ 55 56 :Advantages Low Cost.1 Extremely Energy Efficient.2 this is the most important benefit you will receive from a window air conditioner. If you want to stay cool without spending a lot of money, then.a window AC unit may just be the perfect system for you Easy to Install.3 Can Be Used in Many Places.4 Doesn’t Take Up Floor Space.5 Since they are designed to fit inside a window, this type of air conditioner doesn’t take up any square footage in your home. This a huge benefit if you.live in a tiny house or want to cool a small room 57 :Disadvantages If you shut doors to certain rooms, they will be sweltering hot -1 Once they are installed they can not be easily relocated to another -2.part of the house If they are in a window they will block the view from inside and -3.outside of the home If you have multiple units in your home, it could put a hole in your -4 pocket when the electricity bill comes; you may have to monitor the.use of each system more carefully Source of noise inside the building-5 Distotion for the exterior facades-6 58 59 ‫نظام التكييف بالوحدات المنفصلة‬ ‫‪Split Unit‬‬ ‫‪60‬‬ 61 62 63 64 65 66 67 68 69 70 71 72 73 :ADVANTAGES 74 75 76 DISADVANTAGES 77 78 79 80 81 82 83 :Components of this system are A big piece contains all the units of the cooling system-1 ,(evaporator, compressor, expansion valve, condenser )fans…..etc Two lines , one isolated and called supply line for the -2 conditioned air, and the other for the return air Mixing box used to mix the returned air with fresh air-3 it is preferred to put the supply line higher than the-4 return line in the space for give good movement for air 84 85 86 87 :Disadvantages The large size of the external unit which may cause-1.overweight on the building Grilles have an area of ​large sections So we need-2 to design carefully during architectural period design The size of the vertical air duct may be reached to -3 (2.0*2.0)m The size of the horizontal air duct may be reached to (1- -4 (1-1.5)m 88  The external condensing unit needs a wide, open-4 area in a suitable place of the building 5- it is preferred for the external unit to be near to the vertical duct to avoid exposure the supply lines for external heat 6- Consume large amount of electric energy 7- it is difficult to use for small spaces because it is not easy to distribute the conditioned air in this case. 8-During the design for this system, we should care for the conflict may happen with the columns, beams…….89 Stages of insulation 90 First stage: Design Stages The mechanical engineer starts in collaboration with civil, architectural …..engineers the design stages, which include Compute thermal loads for the building)1 Define the type, size and weight of the selected system)2 Compute the size of the vertical and horizontal grilles)3 that depend on the area to be cooled Making sure that there is no conflict between the)4 conditioning schemes and the other different schemes (architectural, civil, electrical….. ) 91 Second stage :implementation stage Chosing the material (important): the specialist engineer)1 should know the specifications for the material used in the.installation before any agreement with the companies :Ex :Insulators a)External insulators: the thickness should be around 2˝ for the external supply lines b)internal insulators: the thickness should be around 1˝ for the internal supply lines c)Sound insulator 92 Grille diffusers : :Important things choose the kind of the diffuser according to the distribution direction of )1 the air( vertical or horizontal) Choose the shape and color that is appropriate for the space )2 93  :Grilles :Materials used for manufacturing grilles are 1) Galvanized steel plates 2) Non Galvanized steel plates 3) Stainless steel plates 4) Aluminum plates Fiber Glass)5 94 :General Condition for the design of grilles The length of the airways should be as short as possible for )1 :the following reasons a)In long distances, the grilles lose amount of their heat b) The greater the distance the greater the cost All the materials are used in the manufacture of grilles should be )2 Incombustible All interior surfaces are smooth and flat surface )3 Prohibiting the presence of any sharp ends in the internal and )4 external of the grilles surfaces All openings are covered by a suitable cover to prevent the entry of )5 foreign materials during the process of installation Provide airways openings particularly suitable for cleaning)6 95 purposes 96 The angle between the main and branch -7 airway shouldn’t be more than 45 Leave sufficient space around the airways for -8.isolation and fixing purposes The number of the grilles bracings shall not -9 be less than that defined in the specifications Connecting airways with devices in a way so-10 as to ensure the flow and regularity of air flow 97  Third stage Installation stage a)Installed the external condensing unit in their specific places put the external condensing unit above cement or iron base after putting a rubber insulator to prevent.vibration transmission to the building :b)Prepared and installed the internal airways Airways are prepared according to dimensions in -1 executive schemes without interfering with other schemes (structural, electrical,……) 98 use iron paste to connect grilles so that there -2 is no air leak put heat insulator around the supply grilles-3 Hung grilles using props made of an iron angles-4 Installation of suspended ceilings after leaving-5 a space for the entrances and exits of the air (supply and return diffusers) 99 :C) Installed the external grilles Cover the external grilles with a different -1 insulator that is more thick than the one used for the internal grilles due to their exposure to sun.light and environmental conditions After insulation, cover them by cement or -2.aluminum sheets 100 D) Installation of an operating key and test the system. After all installation stages, an operation- key ( thermostat) shall be installed For increasing the efficiency of air conditioning,- this key should be away from supply air diffuser ,.and close to return air diffuser )to feel the return air and decide when to work( 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 :DISADVANTAGES High cost of this system, But in the long run is-1 more energy efficient than previous types Required skill and experience to install,-2 assemble and maintain Required significant equipment and sometimes-3 adjacent special building near to the project need to be conditioned 121 122 123