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Heating Ventilation & Air Conditioning (HVAC)

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A brief outline of HVAC systems related to Architecture & Building Construction

A brief outline of HVAC systems related to Architecture & Building Construction

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  • 1. serviceS ed    ACHARYA NAGARJUNA UNIVERSITY College of Architecture & Planning th Semester, Bachelor of Architecture 7
  • 2. 02 PROLUSION  HVAC (heating, ventilation, and air conditioning) is the technology of indoor and vehicular environmental comfort.  HVAC system design is a sub discipline of mechanical engineering, based on the principles of Thermodynamics, Fluid Mechanics, and Heat transfer.  HVAC systems use ventilation air ducts installed throughout a building to supply conditioned air to a room through outlet vents, called diffusers; and ducts to remove air through return-air grilles.  HVAC is important in the design of medium to large industrial and office buildings such as skyscrapers and in marine environments such as aquariums, where safe and healthy building conditions are regulated with respect to temperature and humidity, using fresh air from outdoors.  The three central functions of heating, ventilating, and airconditioning are interrelated, especially with the need to provide thermal comfort and acceptable indoor air quality within reasonable installation, operation, and maintenance costs.
  • 3. 02 PROLUSION  HVAC systems can provide ventilation, reduce air infiltration, and maintain pressure relationships between spaces.  The means of air delivery and removal from spaces is known as room air distribution.  The starting point in carrying out an estimate both for cooling and heating depends on the exterior climate and interior specified conditions.  In modern buildings the design, installation, and control systems of these functions are integrated into one or more HVAC systems.  For very small buildings, contractors normally capacity engineer and select HVAC systems and equipment.  For larger buildings, building services designers and engineers, such as mechanical, architectural, or building services engineers analyze, design, and specify the HVAC systems.  Basing HVAC on a larger network helps provide an economy of scale that is often not possible for individual buildings, for utilizing renewable energy sources such as solar heat.
  • 4. 02 INTRODUCTION  Thermodynamics is a branch of natural science concerned with heat and its relation to energy and work. It defines macroscopic variables (such as temperature, internal energy, entropy, and pressure) that characterize materials and radiation, and explains how they are related and by what laws they change with time.  Fluid Mechanics : Fluid mechanics is the branch of physics that studies fluids (liquids, gases, and plasmas) and the forces on them. Fluid mechanics can be divided into fluid statics, the study of fluids at rest; fluid kinematics, the study of fluids in motion; and fluid dynamics, the study of the effect of forces on fluid motion.  Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy and heat between physical systems. As such, heat transfer is involved in almost every sector of the economy. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes
  • 5. 02 TERMINOLOGY  In heat transfer, conduction is the transfer of heat energy by microscopic diffusion and collisions of particles or quasi-particles within a body due to a temperature gradient.  Convection is the concerted, collective movement of groups or aggregates of molecules within fluids(e.g., liquids, gases) and rheids, either through advection or through diffusion or as a combination of both of them.  Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation.
  • 6. 02 HEATING  The invention of central heating is often credited to the ancient Romans, who installed systems of air ducts called Hypocausts in the walls and floors of public baths and private villas.  The use of water as the heat transfer medium is known as Hydronics. These systems also contain either duct work for forced air systems or piping to distribute a heated fluid to radiators to transfer this heat to the air.  The radiators may be mounted on walls or installed within the floor to give floor heat.  Most modern hot water boiler heating systems have a circulator, which is a pump, to move hot water through the distribution system.  . This distribution system can be via radiators, convectors (baseboard), hot water coils (hydroair) or other heat exchangers.
  • 7. 02 VENTILATION VENTILATION  Ventilation is the process of changing or replacing air in any space to control temperature or remove any combination of moisture, odors, smoke, heat, dust, airborne bacteria, or carbon dioxide, and to replenish oxygen.  Ventilation includes both the exchange of air with the outside as well as circulation of air within the building  "Mechanical" or "forced" ventilation is provided by an air handler and 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.
  • 8. 02 VENTILATION VENTILATION  In warm or humid months in many climates maintaining thermal comfort solely via natural ventilation may not be possible so conventional air conditioning systems are used as backups.  An important component of natural ventilation is air changes per hour: the rate of ventilation through a room with respect to its volume.  For example, six air changes per hour means that the entire volume of the space is theoretically replaced with new air every ten minutes.  For human comfort, a minimum of four air changes per hour is usually targeted.  The highest recommended replacement rates are for crowded spaces like bars, night clubs, and commercial kitchens at around 30 to 50 air changes per hour
  • 9. 02 AIR CONDITIONING  Air conditioning and refrigeration are provided through the removal of heat.  Heat can be removed through Radiation, Convection, or Conduction.  A refrigerant is employed either in a heat pump system in which a compressor is used to drive Thermodynamic refrigeration cycle, or in a free cooling system which uses pumps to circulate a cool refrigerant (typically water or a glycol mix).  Free cooling systems can have very high efficiencies, and are sometimes combined with seasonal thermal energy storage so the cold of winter can be used for summer air conditioning.  Common storage mediums are deep aquifers or a natural underground rock mass accessed via a cluster of small-diameter, heat exchanger equipped boreholes.  Some systems with small storages are hybrids, using free cooling early in the cooling season, and later employing a heat pump to chill the circulation coming from the storage.
  • 10. 02 An HVAC system is responsible for moderating the temperature of a building’s interior and maintaining it at a comfortable level for the inhabitants. During the hot days of summer, the air conditioning kicks in, providing much-needed cool air. In the frigid days of winter, the system supplies heat.
  • 11. COMPONENTS 02
  • 12. 02 THE FURNACE  The furnace unit is typically fairly large, requiring its own space within a building.  It is often installed in the basement, in the attic, or in a closet.  The furnace pushes the cold or hot air outward into the ducts that run through every room in the building.  Throughout the ducts, there are vents that allow the warm or cool air to pass into rooms and change their interior temperature.
  • 13. 02 THE HEAT EXCHANGER  Heat exchangers reside in the housing of every furnace unit. When the furnace is activated by the thermostat, the heat exchanger begins to function as well.  Air is sucked into the heat exchanger, either from the outside or from a separate duct that pulls cool air out of the building’s rooms. This type of duct is called a cold air return chase.  When the cool air comes into the heat exchanger, it is quickly heated and blown out through the ducts to be dispersed into the building.  If the furnace operates on gas, the heating is accomplished by gas burners. If it uses electricity, it is done via electric coils.
  • 14. 02
  • 15. 02 THE EVAPORATOR COIL  Like heat exchangers, evaporator coils are also part of the furnace unit. However, they serve the opposite function to that of heat exchangers. They are also attached to a different part of the furnace.  Instead of being within the furnace housing, they are installed inside a metal enclosure that is affixed to the side or the top of the furnace.  Evaporator coils are activated when cool air is needed. When triggered, the evaporator coil supplies chilled air, which is then picked up by the furnace blower and forced along the ducts and out through the vents.  The internal design of an evaporator coil resembles that of a car’s radiator. Evaporator coils are connected to the HVAC system’s condensing unit, which is typically located on the exterior of the building.
  • 16. 02 THE CONDENSING UNIT  The condensing unit is installed outside the building, separate from the furnace.  Inside the condensing unit, a special kind of refrigerant gas is cooled through the exchange of heat with the air outside. Then, it is compressed and condensed into liquid form and sent through a tube or a line made of metal.  This tube runs straight to the evaporator coil. When the liquid reaches the coil, a series of small nozzles spray the liquid, lowering its pressure and allowing it to resolve back into gaseous form.  During the evaporation of liquid to gas, heat is absorbed, causing a sudden drop in temperature and supplying cold air for the furnace blowers.  The refrigerant gas is then sent back outside to the condensing unit, and the process is repeated again to generate additional cold air.
  • 17. 02 THE REFRIGERANT LINES  The refrigerant lines are the metal tubes that carry the liquid to the evaporating coil and return the gas to the condensing unit.  Refrigerant lines are usually made from aluminium or copper.  They are designed to be durable and functional under extreme temperatures.
  • 18. 02 THE THERMOSTAT  The thermostat controls the function of the furnace.  It is directly connected to the furnace and includes temperature-sensing technology as well as user controls.  A thermostat is usually positioned somewhere within the building where it can easily discern temperature and remain accessible to users.  A large building may have more than one thermostat to control different areas of the structure.  The inhabitants of the building can manually set the thermostat to a certain temperature.  If the air in the room or building is too cold, the heat exchanger kicks in and blows heat through the vents.  If the room is too warm, the condensing unit and evaporator coil start to function, and the air conditioning system sends cool air throughout the building or to one particular section of the building.
  • 19. 02  Heating ducts are put in during the construction of a home or a building.  They are often run through the ceiling.  In each room, at least one rectangular opening is cut into the duct so that a vent or vents can be installed. THE DUCTS
  • 20. 02 THE VENTS  Vents are usually rectangular in shape. They are placed in the ceiling, with their edges corresponding to the opening in the duct above.  As warm or cool air pours through the ducts, vents allow it to disperse into the rooms below.  Vents are usually made of metal, which can handle a wide range of temperatures.  The vent is comprised of a rectangular edge or frame, within which is a series of thin metal slats. The slats are angled to channel the air downward.  Some vents also include a manual control that lets users angle the air toward a different part of the room depending on their preference.
  • 21. 02 TYPES OF FURNACES Furnaces can be divided into two main categories: Single stage furnaces Two-stage furnaces. Both types of furnaces are further distinguished by their performance ratings. The chart below explains the function of performance ratings. Efficiency Rating 80% efficiency Meaning Ducts collect and reuse 80 percent of the generated heating or cooling energy 92% efficiency Ducts collect and redistribute 90 percent of the or higher energy created by the furnace unit In furnaces with 80% or +92%efficiency, any energy that is not captured by the ducts is lost, usually through the furnace housing or through vents leading to the outside of the building.
  • 22. 02 DEFINITIONS  The Coefficient of performance or COP of a heat pump is a ratio of heating or cooling provided to electrical energy consumed. 𝑄 COP = 𝑊 Q is the heat supplied to or removed from the pump W is the work consumed by the heat pump  Energy Efficiency Ratio : The EER is the ratio of output cooling energy (in BTU) to electrical input energy (in Watt-hour) EER = 𝑜𝑢𝑡𝑝𝑢𝑡 𝑐𝑜𝑜𝑙𝑖𝑛𝑔 𝑒𝑛𝑒𝑟𝑔𝑦 𝑖𝑛 𝐵𝑇𝑈 𝑖𝑛𝑝𝑢𝑡 𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙 𝑒𝑛𝑒𝑟𝑔𝑦 𝑖𝑛 𝑊  Seasonal Energy Efficiency Ratio : It is the ratio of output cooling energy (in BTU) to electrical input energy (in Watt-hour). SEER is a representative measurement of how the system behaves over a season where the outdoor temperature varies SEER = 𝑂𝑈𝑇𝑃𝑈𝑇 𝐶𝑂𝑂𝐿𝐼𝑁𝐺 𝐸𝑁𝐸𝑅𝐺𝑌 𝑂𝐹 𝐴 𝐵𝑇𝑈 𝐼𝑁 𝐴 𝑆𝐸𝐴𝑆𝑂𝑁 𝐼𝑁𝑃𝑈𝑇 𝐸𝐿𝐸𝐶𝑇𝑅𝐼𝐶𝐴𝐿 𝐸𝑁𝐸𝑅𝐺𝑌 𝐼𝑁 𝑊ℎ
  • 23. 02 DEFINITIONS  Kilo-Watt per Ton (kW/ton) The efficiencies of large industrial air conditioner systems, especially chillers, are given in kW/ton to specify the amount of electrical power that is required for a certain power of cooling. In this case, a smaller value represents a more efficient system.  Horse Power Another unit in use in the US is the horse power (HP). This is a unit of power and typically is used to specify the size of motors. It may also be used to specify the input power of an air conditioning system. One HP is approximately 746 W.  Energy Star : In the US, Energy Star is the Environmental Protection Agency’s (EPA’s) indication for products that have high energy efficiency. it makes it easy for consumers to identify and purchase products that have higher energy efficiency than those products without such designation.
  • 24. BIBLIOGRAPHY  http://en.wikipedia.org/wiki/HVAC  http://www.powerknot.com/how-efficient-is-your-air-conditioning-system.html  http://newikis.com/km/%E1%9E%AF%E1%9E%80%E1%9E%9F%E1%9E%B6%E1%9E%9 A:Air_conditioning_unit.svg.html  http:// www.google.com/images (Image courtesy)  http:// www.edcmag.com/articles/hvac-systems-how-they-work
  • 25. Thank you..!!  Joel.T .J., Pratheek.P .A., Y10AP0116 B.Arch. (IV/V) Y10AP0103 B.Arch. (IV/V)