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Hvac Presentation

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  • You will recognize this picture from a previous slide, but we repeat it in order to emphasize the following:
    An air handling system introduces pre-treated air, in order to provide a manufacturing environment with specified cleanliness, temperature and humidity in order to prevent product contamination and degradation. Air is then exhausted from the manufacturing environment.
  • Objectives:
    For you, as inspectors, to be able to judge whether the air handling systems which you encounter during your factory inspections are adequate or not, it is necessary to know how such systems work, and to be aware of what problems may arise in terms of the components of the system.
    Therefore, the objectives of this part of module 3 are to study the components of air handling systems in order to:
    Become familiar with the components
    Know their functions
    Become aware of possible problems
  • To understand the air handling systems, it is necessary to know what their components are.
    A conventional Air Handling System has 4 sub-systems:
    1. Air handling of the incoming (fresh) air: elimination of coarse contaminants and protection from frost if necessary. In the case of air re-circulation, the fresh air is also called make-up air.
    2. Central air handling unit (AHU), where the air will be conditioned (heated, cooled, humidified or de-humidified and filtered), and where fresh air and re-circulated air, if any, (indicated here by the dotted line) will be mixed.
    3. Air handling in the rooms under consideration (pressure differential system, additional filtration, air distribution).
    4. Air exhaust system (filtration).
  • Another way to look at an air handling system is to consider the different components and to know their function.
    Some of the components, particularly the filters, are essential to ensure the quality of the air.
    We will later consider individual components in detail.
    Of course, a well-designed air handling system must not only be properly designed, but also properly installed, qualified and maintained (sealed ducts, tight filters).
    (The trainer should make the audience aware that this slide is just an example, and that all components may not necessarily be present in each system.)
  • A typical HVAC unit consists of a small number of elements only.
    It is important that these elements are compatible, properly installed, and fulfilling their goal.
    Whereas a weather louvre and silencer are less critical elements, the components associated with the flow rate control are essential, as they allow adjustment of the air volumes supplied to the rooms, which in turn forms the base for a pressure differential concept: to have an automated or a fixed system is largely a financial matter, but a fixed system is more difficult to set up.
    Silencer – check internal lining material of silencer as this can cause contamination.
  • Heating and cooling units (batteries), as well as humidifiers are used to adjust the climate in the room (temperature and humidity).
    Special de-humidifiers, on a dessiccant base, will be addressed later.
    Filters are one of the main components, as they determine the size of airborne particles that pass through them, and thus the hygiene class.
    It is wise to protect the finer filters by pre-filters, thus extending their life cycles, and making them less prone to clogging.
    Ducts transport the air from the air handling units to and from the rooms. Inspectors must verify that ducts do not have internal insulation as this is a great source of contamination.
  • There are different air types to be considered within the air handling system:
    Fresh air (if the plant is of the re-circulation type, it is necessary to replace some of the re-circulating air with fresh air, which is then called make-up air).
    A proportion of about 15% fresh air is normal, but this proportion can vary, depending on factors such as number of people, National Regulatory Authority requirements, the presence of certain substances in the air, leakage due to pressure control, etc.
    Supply air to the rooms
    Exhaust air from the rooms
    Return air (about 85% is being re-circulated)
  • The filtration efficacy depends on several mechanisms, and results in a rough filter classification.
    The diagram shows the commonly used classification, with current abbreviations G = Gross, F= Fine, H= High, U= Ultra.
    Filters are certified by the suppliers (challenge/efficiency test), but are often not properly installed or can be damaged. Leak tests (integrity tests), showing leakage of air through the filter itself or through its frame, therefore, have to be performed. Integrity tests are usually only carried out on the Aerosol filters (HEPA & ULPA).
    Integrity or penetration testing is performed to detect leaks from the filter media, filter frame and seal. The challenge is a poly-dispersed aerosol usually composed of particles ranging in size from one to three microns. The test is done in place and the filter face is scanned with a photometer probe; the measured downstream leakage is taken as a percentage of the upstream challenge. Integrity tests should be carried out with filters installed in the system and should be carried out by an independent body (not the filter supplier).
    The efficiency test, on the other hand, is used to determine the filter's rating. This test uses a mono-dispersed aerosol of 0.3 micron size particles, relates to filter media, and usually requires specialized equipment. Downstream readings represent an average over the entire filter surface. Therefore, leaks in a filter may not be detected by an efficiency test.
  • This slide shows
    Primary Panel filters, which are used mainly for lower filtration efficiency or as pre-filters
    Secondary filters, consisting of mini-pleated media or filter bags, and is used for higher filtration efficiency.
    HEPA or tertiary filters, usually being the final filter in the system, providing the highest filtration efficiency.
    Though there is a strong relationship between filter efficiency and cleanroom class, a filter of a high efficiency does not guarantee a high cleanroom class, as many other elements play a role, such as
    Air flow (how the air is extracted, how well the room is “flushed”)
    Air speed and number of air changes
    Positions of air terminals
    Layout and presence of objects
    Personnel and clothing
    Equipment (not all machines are designed to operate in a clean environment!)
    Proper installation and proper maintenance
  • This slide shows additional elements of the air handling units.
    For humidification purposes, especially in clean areas, high purity water should be used, to avoid contamination.
    The silencer is not important from a GMP point of view, but from an environmental one, as ventilation units can be very noisy. Be sure that the silencers are manufactured of suitable materials as the linings of standard silencers can contaminate air with particulates.
    Depending on the local legislation, the installation of silencers can be mandatory.
    The cooling unit is important during the hot season. Be aware that stagnating water (condensed water) can bring bacterial growth, which can contaminate the filters, pass through them (depending on their retention properties) and end up contaminating production areas.
    It is essential that there is no stagnating water. Cooling coils can be sanitized as well.
    Do remember that, if filters are not properly maintained, micro-organisms may grow through the filters and be carried towards the production rooms.
  • Dampers to control pressure differentials are important. They can be automated or fixed. As filters get dirty the system pressure losses increase, and if airflow is not regulated, the flow decreases and pressure differentials change. This could cause flow reversal and cross-contamination. Variable speed drives for fan motors are also commonly used to control airflow.
    In some cases, it is necessary to have very dry air for galenical reasons in certain rooms (production of effervescent tablets and humidity sensitive products in general).
    To generate dry air, the air supplied to the production is passed over an adsorbant (silicagel, lithium chloride, etc.) where the humidity is removed from the air.
    The adsorbant is then re-generated, on a continuous or on a batch-wise base.
  • One of the main points in the design of production rooms is the pressure differentials concept.
    Pressure differentials must be defined, monitored and alarmed in critical cases.
    The overpressure of each room is measured against a reference point in the factory (point zero). As discussed earlier, the pressure regulation can be fixed or automated. Pressure control can be by means of automatic air flow control dampers (as shown in slide 15) or by means of fan speed control. Whatever the means used it is important to ask the manufacturer how they ensure that the pressure cascade is maintained as the filters get dirty.
    In the following slides, we are going to see that an overpressure concept can be very different for sterile products and for solid products.
  • This slide illustrates the pressure differential system in a sterile area where the overpressure is kept high in the rooms, mainly in the A/B class room, to prevent the entry of micro-organisms.
    (The level of overpressure is reflected by the absolute pressure in Pascals).
    To enter all rooms, it is necessary to go through airlocks.
    In this particular example, the pressure differential in sterile areas is set up at 15 Pa between zones of different cleanliness, in accordance with FDA, EC and PIC/S regulations. Other values may apply in other regions.
    It must be understood that high pressure differentials have an influence on the stability of building elements such as walls and doors.
    Factory layouts must be carefully planned, in order not to have too high a pressure differential between entrance and exit of a sterilising or depyrogenating tunnel, as the air flow may significantly affect the temperature in a tunnel.
    Pressure differentials must be constantly monitored.
    The loss of overpressure in a filling room for injectables may mean the loss of the batches under production and the need for complete sanitation of the facility.
    It is therefore essential that the systems are designed in such a way that there is no loss of overpressure in case of power loss (overpressure fan should be linked to emergency power grid).
  • This slide illustrates the pressure differential system in a solids area where the overpressure is kept high in the corridors, to prevent cross-contamination.
    In this case, we are not too worried by the microbial contamination, but rather by dust coming out of rooms where process work is being done, and thus contaminating other rooms.
    The entry into some rooms (containing dangerous products such as hormones, cytotoxics, low RH products or strongly coloured products) is protected by airlocks.
  • Transcript

    • 1. HVAC Systems – UnderstandingHVAC Systems – Understanding the basisthe basis Table of ContentsTable of Contents 1.1. Introduction to HVAC SystemsIntroduction to HVAC Systems 2.2. HVAC System TypesHVAC System Types 3.3. HVAC Piping SystemHVAC Piping System 4.4. HVAC Air Distribution EquipmentsHVAC Air Distribution Equipments 5.5. Fans and PumpsFans and Pumps 6.6. HVAC Instrumentation and ControlHVAC Instrumentation and Control 7.7. HVAC System CommissioningHVAC System Commissioning
    • 2. Introduction to HVAC SystemsIntroduction to HVAC Systems  This article introduces the heating, ventilating and air-conditioningThis article introduces the heating, ventilating and air-conditioning (HVAC) systems. The primary function of HVAC systems is to provide(HVAC) systems. The primary function of HVAC systems is to provide healthy and comfortable interior conditions for occupants; well-healthy and comfortable interior conditions for occupants; well- designed, efficient systems do this with minimal non-renewabledesigned, efficient systems do this with minimal non-renewable energy and air, and water pollutant emissions.energy and air, and water pollutant emissions.
    • 3. Introduction to HVAC SystemsIntroduction to HVAC Systems  The purpose ofThe purpose of HVAC designHVAC design is both high indoor air quality and energyis both high indoor air quality and energy efficiency. These dual considerations require an integrated designefficiency. These dual considerations require an integrated design approach. Rigs heating,approach. Rigs heating, ventilation, and air conditioningventilation, and air conditioning system (HVAC) creates a climatesystem (HVAC) creates a climate that allows for maximum comfort bythat allows for maximum comfort by compensating for changing climaticcompensating for changing climatic conditions.conditions.  Though more costly to install and more complicated to operate, a chiller plantThough more costly to install and more complicated to operate, a chiller plant offers a number of benefits over a large number of individual packagedoffers a number of benefits over a large number of individual packaged cooling units, including greater energy efficiency, better controllability,cooling units, including greater energy efficiency, better controllability, cheaper overall maintenance, and longer life. Using a comprehensivecheaper overall maintenance, and longer life. Using a comprehensive approach to building design, designers around the world have succeeded atapproach to building design, designers around the world have succeeded at creating highly efficient air-conditioning systems that provide excellentcreating highly efficient air-conditioning systems that provide excellent comfort at significant savings.comfort at significant savings.
    • 4. Introduction to HVAC SystemsIntroduction to HVAC Systems  Heating, ventilating and air-Heating, ventilating and air- conditioning (HVAC) systemsconditioning (HVAC) systems reduce the environmentalreduce the environmental impact of rigs/buildings in severalimpact of rigs/buildings in several key ways. The most importantkey ways. The most important function of a HVAC systems isfunction of a HVAC systems is to provide the rig/buildings occupantsto provide the rig/buildings occupants with healthy and comfortable interiorwith healthy and comfortable interior conditions. A carefully designed, efficientconditions. A carefully designed, efficient system can do this with minimal non-system can do this with minimal non- renewable energy and air and water pollutant emissions to minimize therenewable energy and air and water pollutant emissions to minimize the environmental impact.environmental impact. Cooling equipment that avoids chlorofluorocarbons and hydro-Cooling equipment that avoids chlorofluorocarbons and hydro- chlorofluorocarbons (CFCs and HCFCs) eliminates a major cause ofchlorofluorocarbons (CFCs and HCFCs) eliminates a major cause of damage to the ozone layer.damage to the ozone layer.
    • 5. Introduction to HVAC SystemsIntroduction to HVAC Systems  Even the best HVAC equipment and systems cannot compensate for aEven the best HVAC equipment and systems cannot compensate for a faulty rig design. Problems of this type cause inherently high cooling andfaulty rig design. Problems of this type cause inherently high cooling and heating needs and consume unnecessary resources and should beheating needs and consume unnecessary resources and should be corrected if possible. Conservation of non-renewable energy through ancorrected if possible. Conservation of non-renewable energy through an intelligent architectural design offers the greatest opportunity for savings.intelligent architectural design offers the greatest opportunity for savings. The most important factors in these designs are careful control of solar gain,The most important factors in these designs are careful control of solar gain, while taking advantage of passive heating, daylighting, natural ventilationwhile taking advantage of passive heating, daylighting, natural ventilation and cooling. The critical factors in mechanical systems' energy consumptionand cooling. The critical factors in mechanical systems' energy consumption - and capital cost - are reducing the cooling and heating loads they must- and capital cost - are reducing the cooling and heating loads they must handle.handle.
    • 6. HVAC System TypesHVAC System Types  Types of System Designs - There are several major heating, ventilating, and airTypes of System Designs - There are several major heating, ventilating, and air conditioning system types in wide spread use today. These are air systems, hydronicconditioning system types in wide spread use today. These are air systems, hydronic and steam systems, and unitary type systems. Most systems in use today fall into one ofand steam systems, and unitary type systems. Most systems in use today fall into one of these categories, or are a combination or variation of them. Each type of system hasthese categories, or are a combination or variation of them. Each type of system has advantages and disadvantages.advantages and disadvantages.  Air cooledAir cooled -- Air cooledAir cooled ChillersChillers
    • 7.  Air Cooled Chiller AdvantagesAir Cooled Chiller Advantages • Lower installed costLower installed cost • Quicker availabilityQuicker availability • No cooling tower or condenser pump requiredNo cooling tower or condenser pump required • Less maintenanceLess maintenance • No mechanical room requiredNo mechanical room required
    • 8.  Water CooledWater Cooled - Sea Water cooled Chillers- Sea Water cooled Chillers - Fresh Water cooled Chillers- Fresh Water cooled Chillers
    • 9.  Water-Cooled Chiller advantagesWater-Cooled Chiller advantages • Higher efficiencyHigher efficiency • Custom selection in larger sizesCustom selection in larger sizes • Large tonnage capabilitiesLarge tonnage capabilities • Indoor Chiller locationIndoor Chiller location • Longer lifeLonger life
    • 10. Purpose of an air handling systemPurpose of an air handling system Air Handling System Room With Defined Requirements Supply Air Outlet Air Air Handling Systems
    • 11. Objectives In the following slides, we will study the components of air handling systems in order to: 1. Become familiar with the components 2. Know their functions 3. Become aware of possible problems
    • 12. + Room/Cabin Exhaust air treatment Central air handling unit Terminal air treatment at production room level Fresh air treatment (make-up air) Main subsystems
    • 13. FilterSilence r Terminal filter Weather louvre Control damper FanFlow rate controller Humidifier Heating coil Cooling coil with droplet separator Production Room Overview components + Prefilter Exhaust Air Grille Heater Secondary Filter Re-circulated air
    • 14.  WeatherWeather louvrelouvre  SilencerSilencer  Flow rateFlow rate controllercontroller  ControlControl damperdamper  To prevent insects, leaves,To prevent insects, leaves, dirtdirt and rainand rain from enteringfrom entering  To reduce noise caused by airTo reduce noise caused by air circulationcirculation  Automated adjustment ofAutomated adjustment of volume of air (night and day,volume of air (night and day, pressure control)pressure control)  Fixed adjustment of volumeFixed adjustment of volume of airof air Components (1)
    • 15.  Heating unitHeating unit Cooling unitCooling unit /dehumidifier/dehumidifier HumidifierHumidifier FiltersFilters DuctsDucts  ToTo heatheat the air to the properthe air to the proper temperaturetemperature  ToTo coolcool the air to thethe air to the requiredrequired temperaturetemperature or to remove moistureor to remove moisture from the airfrom the air  To bring the air to the properTo bring the air to the proper humidity, if too lowhumidity, if too low  To eliminate particles of pre-To eliminate particles of pre- determined dimensions and/ordetermined dimensions and/or micro-organismsmicro-organisms  To transport the airTo transport the air Components (2)
    • 16. + Production Room Exhaust air Return air (re-circulated) Fresh air (make-up air) Supply air Air types
    • 17. Filter classesFilter classes Dust filters Standard Aerosol FineCoarse ULPAHEPA 10 µ m > Dp > 1 µ mDp > 10 µ m Dp < 1 µ m F5 - F9G1 - G4 U 14- 17H 11 - 13 EN 1822 StandardEN 779 Standard
    • 18. Primary panelPrimary panel filterfilter SecondarySecondary filterfilter HEPA or tertiaary filter
    • 19. Duct heatersDuct heaters Room HetersRoom Heters SilensersSilensers
    • 20. Volume control damperVolume control damper De-humidification Filter Pressure Gauges AHU with fan Variable Speed Controller Humid room air Air heater Regeneration air Humid room air Adsorber wheel Dry air FireFire DampersDampers
    • 21. Annex 1, 17.26 Regulation of room pressureRegulation of room pressure – pressure– pressure differentials conceptdifferentials concept Room pressure gauges Room pressure indication panel
    • 22. Pressure cascade injectablesPressure cascade injectables PProtection from micro-organisms androtection from micro-organisms and particlesparticles N o te : D ir e c t io n o f d o o r o p e n in g r e la t iv e to r o o m p r e s s u r e 1 5 P a 0 P a A ir L o c k 3 0 P a P a s s a g eD C A B D L F A ir L o c kA ir L o c k 4 5 P a R o o m 3R o o m 2R o o m 1 4 5 P a6 0 P a3 0 P a
    • 23. Pressure cascade solids Protection from cross-contamination Note:Directionofdooropeningrelativetoroompressure 15Pa 15Pa15P aE 30PaPassage 0PaAirLock Room3Room2Room115Pa AirLockAirLock N o t e : D i r e c t i o n o f d o o r o p e n i n g r e l a t i v e t o r o o m p r e s s u r e 1 5 Pa 1 5 Pa1 5 Pa E3 0 Pa P a s s a g e 0 Pa A ir L o c k R o o m 3R o o m 2R o o m 1 1 5 Pa A ir L o c kA ir L o c k
    • 24. Fan Coil UnitFan Coil Unit
    • 25. Self Contain UnitSelf Contain Unit
    • 26. HVAC Air Distribution EquipmentsHVAC Air Distribution Equipments  DiffusersDiffusers 4 Way Diffusers4 Way Diffusers Two Way Diffusers One Way DiffuserTwo Way Diffusers One Way Diffuser Round DiffusersRound Diffusers
    • 27. Cabin UnitsCabin Units
    • 28.  Return / Exhaust GrillesReturn / Exhaust Grilles
    • 29. ContentsContents  Fan DesignFan Design  Fan PerformanceFan Performance  Fan-duct SystemsFan-duct Systems  Duct ConstructionDuct Construction  Air Duct DesignAir Duct Design Fans and Pumps
    • 30. Fan DesignFan Design  Common types of fansCommon types of fans  Centrifugal fansCentrifugal fans: radial, forward curved, air: radial, forward curved, air foil (backward curved), backward inclined,foil (backward curved), backward inclined, tubular, roof ventilatortubular, roof ventilator  Axial fansAxial fans: propeller, tube-axial, vane-axial: propeller, tube-axial, vane-axial  Fan arrangementsFan arrangements  Motor location, air discharge orientation, driveMotor location, air discharge orientation, drive train type (direct drive or pulley drive)train type (direct drive or pulley drive)  Centrifugal: single width single inlet (SWSI),Centrifugal: single width single inlet (SWSI), double width double inlet (DWDI)double width double inlet (DWDI)
    • 31. Centrifugal and axial fan components AXIAL FANSCENTRIFUGAL FANS
    • 32. Propeller Tube-axial Tube-vane AXIAL FANS
    • 33. Tubular centrifugal fan Centrifugal roof ventilator CENTRIFUGAL FANS (* Note the airflow paths and impeller design.)
    • 34. Drive arrangements and motor positions
    • 35. Single- and double-width centrifugal fans
    • 36. Fan PerformanceFan Performance  Major parametersMajor parameters  Fan volume flow rate (mFan volume flow rate (m33 /s or l/s),/s or l/s), VVff  Fan total pressureFan total pressure ΔΔpptftf, fan velocity pressure, fan velocity pressure ppvfvf & fan static pressure& fan static pressure ΔΔppsfsf (Pa)(Pa)  Fan power & efficiencyFan power & efficiency • Fan power or air power (W) =Fan power or air power (W) = ΔΔpptftf xx VVff • Fan power input on the fan shaft (brakeFan power input on the fan shaft (brake horsepower),horsepower), PPff • Fan total efficiency:Fan total efficiency: ηηtt == ΔΔpptftf xx VVff // PPff  Combined aerodynamic, volumetric & mechanicalCombined aerodynamic, volumetric & mechanical efficienciesefficiencies • Fan static efficiency:Fan static efficiency: ηηss == ΔΔppsfsf xx VVff // PPff • Air temp. increase through fan,Air temp. increase through fan, ΔΔTT == ΔΔpp /(/(ρρcc ηη))
    • 37. Fan performance curves Total pressure Static pressure Fan total efficiency Fan static efficiency Fan power input Velocity pressure Volume flow rate
    • 38. Typical fan performance curve
    • 39. Fan PerformanceFan Performance  Fan LawsFan Laws  Speed (Speed (nn))  Volume flow (Volume flow (VV))  Total pressure lossTotal pressure loss ((ΔΔpp ))  Air density (Air density (ρρ))  For air systems thatFor air systems that are geometrically &are geometrically & dynamically similar:dynamically similar: (D = impeller(D = impeller diameter)diameter)  c.f.: pump lawsc.f.: pump laws
    • 40. Velocity triangle at the blade inlet and outlet of a centrifugal fan CENTRIFUGAL FANS
    • 41. Fan PerformanceFan Performance  Major issues causing energy losses to aMajor issues causing energy losses to a centrifugal fan:centrifugal fan:  Circulatory flow between the bladesCirculatory flow between the blades  Air leakage at the inletAir leakage at the inlet  Friction between fluid particles and the bladeFriction between fluid particles and the blade  Energy loss at the entranceEnergy loss at the entrance  Partially filled passagePartially filled passage
    • 42. Operating characteristics for a backward-curved centrifugal fan
    • 43. Total efficiency curves for centrifugal fans
    • 44. Fan power curves for centrifugal fans with same impeller diameter
    • 45. Fan pressure curves for centrifugal fans with same impeller diameter
    • 46. Velocity triangles for a vane-axial fan AXIAL FANS
    • 47. Fan pressure curves for axial fans with same impeller diameter
    • 48. Fan efficiency curves for axial fans with same impeller diameter
    • 49. Fan power curves for axial fans with same impeller diameter
    • 50. Performance curves for controllable- pitch vane-axial fans
    • 51. Fan-duct SystemsFan-duct Systems  Duct pressure changes (c.f. atmDuct pressure changes (c.f. atm pressure)pressure)  Static pressure (SP)Static pressure (SP)  Velocity pressure (VP) =Velocity pressure (VP) = ρρVV22 / 2 g/ 2 g  Total pressure (TP) = SP + VPTotal pressure (TP) = SP + VP  Fan: a pumping deviceFan: a pumping device  Fan (total) pressure = pressure differenceFan (total) pressure = pressure difference between fan inlet and fan dischargebetween fan inlet and fan discharge  At fan suction/inlet, SP = negative (c.f.At fan suction/inlet, SP = negative (c.f. atmospheric); at discharge, SP = positiveatmospheric); at discharge, SP = positive
    • 52. Fan-duct SystemsFan-duct Systems  Pressure characteristicsPressure characteristics  SP and VP are mutually convertible (↑or↓)SP and VP are mutually convertible (↑or↓)  TP always decreases in the direction ofTP always decreases in the direction of airflowairflow  For constant-area straight duct sectionsFor constant-area straight duct sections • Velocity and VP are constantVelocity and VP are constant • TP change = SP changeTP change = SP change  When duct cross-sectional areas are reducedWhen duct cross-sectional areas are reduced • Velocity and VP increaseVelocity and VP increase • Absolute value of both TP and SP decreaseAbsolute value of both TP and SP decrease • Dynamic losses from elbow, dampers, etc.Dynamic losses from elbow, dampers, etc.
    • 53. Fan-duct SystemsFan-duct Systems  Fan-duct systemsFan-duct systems  Flow resistanceFlow resistance RR, pressure drop, pressure drop ΔΔpp andand volume flow ratevolume flow rate VV  Duct sections in series:Duct sections in series:  Duct sections in parallel:Duct sections in parallel: 2 VRp ⋅=∆ o ns RRRR +++= 21 np RRRR 1111 21 +++= 
    • 54. Fan-duct SystemsFan-duct Systems  Fan-duct systemsFan-duct systems  TerminologyTerminology • Primary air (conditioned air or makeup air)Primary air (conditioned air or makeup air) • Secondary air (induced space air, plenum air, orSecondary air (induced space air, plenum air, or recirculating air)recirculating air) • Transfer air (indoor air that moves from anTransfer air (indoor air that moves from an adjacent area)adjacent area)  System curve: volume flow vs pressure lossSystem curve: volume flow vs pressure loss  System operating pointSystem operating point
    • 55. Fan-duct SystemsFan-duct Systems  System effectSystem effect ΔΔpptsts  Its additional total pressure loss caused byIts additional total pressure loss caused by uneven or non-uniform velocity profile at theuneven or non-uniform velocity profile at the fan inlet, or at duct fittings after fan outletfan inlet, or at duct fittings after fan outlet  Due to the actual inlet and outlet connectionsDue to the actual inlet and outlet connections as compared with the total pressure loss of theas compared with the total pressure loss of the fan test unit during laboratory ratingsfan test unit during laboratory ratings Inlet Outlet
    • 56. Fan system operating point & system effect
    • 57. Fan-duct SystemsFan-duct Systems  Modulation of air systemsModulation of air systems  Constant volume systemConstant volume system • Volume flow rate remains constantVolume flow rate remains constant • Supply temperature is raised during part loadSupply temperature is raised during part load  Variable-air-volume (VAV) systemVariable-air-volume (VAV) system • Volume flow rate is reduced to match part loadVolume flow rate is reduced to match part load operationoperation • Modulation curveModulation curve
    • 58. Fan modulation curve
    • 59. Fan-duct SystemsFan-duct Systems  Fan modulation methodsFan modulation methods  DamperDamper (vary the opening of the air flow(vary the opening of the air flow passage)passage) • Waste energyWaste energy  Inlet vanesInlet vanes (opening & angle of inlet vanes)(opening & angle of inlet vanes) • Low cost; less efficient than following typesLow cost; less efficient than following types  Inlet coneInlet cone (peripheral area of fan impeller)(peripheral area of fan impeller) • Inexpensive; for backward curved centrifugal fanInexpensive; for backward curved centrifugal fan  Blade pitchBlade pitch (blade angle of axial fan)(blade angle of axial fan)  Fan speedFan speed (using adjustable frequency(using adjustable frequency drives)drives) • Most energy-efficient; but usually cost moreMost energy-efficient; but usually cost more
    • 60. Damper, inlet vanes & fan speed modulation
    • 61. Inlet vane modulation
    • 62. Fan speed modulation using AC inverter
    • 63. Fan-duct SystemsFan-duct Systems  Fan surgeFan surge (in centrifugal fan)(in centrifugal fan)  Occurs when air volume flow is not sufficient toOccurs when air volume flow is not sufficient to sustain the static pressure difference betweensustain the static pressure difference between discharge & suctiondischarge & suction • Discharge pressure is reduced momentarilyDischarge pressure is reduced momentarily • Volume flow & pressure fluctuationsVolume flow & pressure fluctuations • Create noise & vibrationCreate noise & vibration  Surge region: shall avoid operation in itSurge region: shall avoid operation in it  Fan stallFan stall (in axial fans)(in axial fans)  When smooth air flow suddenly breaks & pressureWhen smooth air flow suddenly breaks & pressure difference across the blades decreasesdifference across the blades decreases  The fan loses pressure capability drasticallyThe fan loses pressure capability drastically
    • 64. Stall and stall region of an axial fan
    • 65. Fan-duct SystemsFan-duct Systems  Fan selectionFan selection  Select fan type + determine fan sizeSelect fan type + determine fan size  Important factors:Important factors: • Pressure-volume flow operating characteristicsPressure-volume flow operating characteristics • Fan capacity modulationFan capacity modulation • Fan efficiencyFan efficiency • Sound power levelSound power level • Airflow directionAirflow direction • Initial costInitial cost
    • 66. Duct ConstructionDuct Construction  Types of air ductTypes of air duct  Supply air ductSupply air duct  Return air ductReturn air duct  Outdoor air ductOutdoor air duct  Exhaust airExhaust air  Duct sectionsDuct sections  Header or main duct (trunk)Header or main duct (trunk)  Branch duct or runoutBranch duct or runout
    • 67. Duct ConstructionDuct Construction  Duct systemsDuct systems  Max. pressure difference (between air insideMax. pressure difference (between air inside the duct and the ambient air)the duct and the ambient air) • 125, 250, 500, 750, 1000, 1500, 2500 Pa125, 250, 500, 750, 1000, 1500, 2500 Pa  Commercial buildingsCommercial buildings • Low-pressure duct system: ≤ 500 Pa, max 12 m/sLow-pressure duct system: ≤ 500 Pa, max 12 m/s • Medium-pressure system: 500-1500 Pa, max 17.5Medium-pressure system: 500-1500 Pa, max 17.5 m/sm/s  Residential buildings: 125 Pa or 250 PaResidential buildings: 125 Pa or 250 Pa  Industrial duct system:Industrial duct system: ΔΔP can be higherP can be higher
    • 68. Duct ConstructionDuct Construction  Duct material: e.g. UL (Underwriters’Duct material: e.g. UL (Underwriters’ Laboratory) standardLaboratory) standard  Class 0: zero flame spread, zero smokeClass 0: zero flame spread, zero smoke developeddeveloped • Iron, galvanized steel, aluminum, concrete,Iron, galvanized steel, aluminum, concrete, masonry, clay tilemasonry, clay tile  Class 1: flame spread ≤ 25, smokeClass 1: flame spread ≤ 25, smoke developed ≤ 50developed ≤ 50 • Fiberglass, many flexible ductsFiberglass, many flexible ducts  Class 2: flame spread ≤ 50, smokeClass 2: flame spread ≤ 50, smoke developed ≤ 100developed ≤ 100
    • 69. Duct ConstructionDuct Construction  Shapes of air ductShapes of air duct  RectangularRectangular • More easily fabricated on site, air leakageMore easily fabricated on site, air leakage  RoundRound • Less fluid resistance, better rigidity/strengthLess fluid resistance, better rigidity/strength  Flat ovalFlat oval  FlexibleFlexible • Multiple-ply polyester film w/ metal wire or stripsMultiple-ply polyester film w/ metal wire or strips  SMACNA (Sheet Metal and AirSMACNA (Sheet Metal and Air Conditioning Contractors’ NationalConditioning Contractors’ National Association) standardsAssociation) standards
    • 70. Rectangular duct Round duct w/ spiral seam Flat oval duct Flexible duct (Source: Wang, S. K., 2001. Handbook of Air Conditioning and Refrigeration)
    • 71. Transverse joint reinforcement (Source: Wang, S. K., 2001. Handbook of Air Conditioning and Refrigeration)
    • 72. Duct ConstructionDuct Construction  Duct specificationDuct specification  Sheet gauge and thickness of duct materialSheet gauge and thickness of duct material  Traverse joints & longitudinal seamTraverse joints & longitudinal seam reinforcementsreinforcements  Duct hangers & their spacingDuct hangers & their spacing  Tapes & adhesive closuresTapes & adhesive closures  Fire spread and smoke developedFire spread and smoke developed  Site-fabricated or factory-/pre-fabricatedSite-fabricated or factory-/pre-fabricated
    • 73. Duct ConstructionDuct Construction  Duct heat gain or lossDuct heat gain or loss  Temperature rise or dropTemperature rise or drop  Duct insulation (mounted or inner-lined)Duct insulation (mounted or inner-lined) • Reduce heat gain/loss, prevent condensation,Reduce heat gain/loss, prevent condensation, sound attentuationsound attentuation • Minimum & recommended thicknessMinimum & recommended thickness  See ASHRAE standard or local codesSee ASHRAE standard or local codes  Temperature rise curvesTemperature rise curves • Depends on air velocity, duct dimensions &Depends on air velocity, duct dimensions & insulationinsulation
    • 74. Temperature rise from duct heat gain (Source: Wang, S. K., 2001. Handbook of Air Conditioning and Refrigeration)
    • 75. Duct ConstructionDuct Construction  Frictional lossesFrictional losses  Darcey-Weisbach EquationDarcey-Weisbach Equation • HHff = friction head loss, or= friction head loss, or ΔΔppff = pressure loss= pressure loss • ff = friction factor (dimensionless)= friction factor (dimensionless) • LL = length of duct or pipe (m)= length of duct or pipe (m) • DD = diameter of duct or pipe (m)= diameter of duct or pipe (m) • vv = mean air velocity in duct (m/s)= mean air velocity in duct (m/s)
    • 76. Mode of airflow when air passes over and around surface protuberances of the duct wall δ >ε δ <ε
    • 77. Duct ConstructionDuct Construction  Duct friction chartDuct friction chart  Colebrook formulaColebrook formula  Roughness & temperature correctionsRoughness & temperature corrections  ΔΔppff == KKsrsr KKTT KKelelΔΔppf,cf,c • KKsrsr = correction factor for surface roughness= correction factor for surface roughness • KKTT = correction factor for air temperature= correction factor for air temperature • KKelel = correction factor for elevation= correction factor for elevation
    • 78. Friction chart for round duct
    • 79. Duct ConstructionDuct Construction  Circular equivalentCircular equivalent  Hydraulic diameter,Hydraulic diameter, DDhh = 4= 4 AA // PP • AA = area (mm= area (mm22 );); PP = perimeter (mm)= perimeter (mm)  Rectangular duct:Rectangular duct:  Flat oval duct:Flat oval duct:
    • 80. Duct ConstructionDuct Construction  Dynamic lossesDynamic losses  Result from flow disturbances caused by duct-Result from flow disturbances caused by duct- mounted equipment and fittingsmounted equipment and fittings • Change airflow path’s direction and/or areaChange airflow path’s direction and/or area • Flow separation & eddies/disturbancesFlow separation & eddies/disturbances  In dynamic similarity (same Reynolds numberIn dynamic similarity (same Reynolds number & geometrically similar duct fittings), dynamic& geometrically similar duct fittings), dynamic loss is proportional to their velocity pressureloss is proportional to their velocity pressure
    • 81. Duct ConstructionDuct Construction  Local or dynamic loss coefficientLocal or dynamic loss coefficient  Ratio of total pressure loss to velocityRatio of total pressure loss to velocity pressurepressure
    • 82. Duct ConstructionDuct Construction  Duct fittingsDuct fittings  ElbowsElbows  Converging or diverging tees and wyesConverging or diverging tees and wyes  Entrances and exitsEntrances and exits  Enlargements and contractionsEnlargements and contractions  Means to reduce dynamic lossesMeans to reduce dynamic losses  Turning angle, splitter vanesTurning angle, splitter vanes  ASHRAE duct fitting databaseASHRAE duct fitting database  Fitting loss coefficientsFitting loss coefficients
    • 83. Region of eddies and turbulences in a round elbow 5-piece 90o round elbow
    • 84. Rectangular elbow, smooth radius, 2 splitter vanes Mitered elbow and its secondary flow
    • 85. Airflow through a rectangular converging or diverging wye
    • 86. Entrance Exit
    • 87. Abrupt enlargement Sudden contraction
    • 88. Duct ConstructionDuct Construction  Flow resistance,Flow resistance, RR  Total pressure lossTotal pressure loss ΔΔpptt at a specific volume flowat a specific volume flow raterate VV  Flow resistance in series:Flow resistance in series:  Flow resistance in parallel:Flow resistance in parallel: 2 VRpt ⋅=∆ ns RRRR +++= 21 np RRRR 1111 21 +++= 
    • 89. Total pressure loss and flow resistance of a round duct section
    • 90. Flow resistance in series Flow resistance in parallel
    • 91. Flow resistance for a Y connection
    • 92. Air Duct DesignAir Duct Design  Optimal air duct designOptimal air duct design  Optimal duct system layout, space availableOptimal duct system layout, space available  Satisfactory system balanceSatisfactory system balance  Acceptable sound levelAcceptable sound level  Optimum energy loss and initial costOptimum energy loss and initial cost  Install only necessary balancing devicesInstall only necessary balancing devices (dampers)(dampers)  Fire codes, duct construction & insulationFire codes, duct construction & insulation  Require comprehensive analysis & care forRequire comprehensive analysis & care for different transport functionsdifferent transport functions
    • 93. Flow characteristics of a supply duct system
    • 94. Air Duct DesignAir Duct Design  Design velocityDesign velocity  Constraints: space available, beam depthConstraints: space available, beam depth  Typical guidelines:Typical guidelines: • Main ducts: air flow usually ≤ 15 m/s; air flow noiseMain ducts: air flow usually ≤ 15 m/s; air flow noise must be checkedmust be checked • With more demanding noise criteria (e.g. hotels),With more demanding noise criteria (e.g. hotels), max. air velocity: main duct ≤ 10-12.5 m/s, returnmax. air velocity: main duct ≤ 10-12.5 m/s, return main duct ≤ 8 m/s, branch ducts ≤ 6 m/smain duct ≤ 8 m/s, branch ducts ≤ 6 m/s  Face velocities for air-handling systemFace velocities for air-handling system componentscomponents
    • 95. Air Duct DesignAir Duct Design  Reduce dynamic losses of the critical pathReduce dynamic losses of the critical path  Maintain optimum air velocity through ductMaintain optimum air velocity through duct fittingsfittings  Emphasize reduction of dynamic lossesEmphasize reduction of dynamic losses nearer to the fan outlet or inlet (high airnearer to the fan outlet or inlet (high air velocity)velocity)  Proper use of splitter vanesProper use of splitter vanes  Set 2 duct fittings as far apart as possibleSet 2 duct fittings as far apart as possible  Air duct leakageAir duct leakage  Duct leakage classificationDuct leakage classification • AISI, SMACNA, ASHRAE standardsAISI, SMACNA, ASHRAE standards
    • 96. Air Duct DesignAir Duct Design  Fire protectionFire protection  Duct material selectionDuct material selection  Vertical ducts (using masonry, concrete orVertical ducts (using masonry, concrete or clay)clay)  When ducts pass through floors & wallsWhen ducts pass through floors & walls  Use of fire dampersUse of fire dampers  Filling the gaps between ducts & bldgFilling the gaps between ducts & bldg structurestructure  Duct systems for industrial applicationsDuct systems for industrial applications  Any other fire precautions?Any other fire precautions?
    • 97. Air Duct DesignAir Duct Design  Design procedure (computer-aided or manual)Design procedure (computer-aided or manual)  Verify local codes & material availabilityVerify local codes & material availability  Preliminary duct layoutPreliminary duct layout  Divide into consecutive duct sectionsDivide into consecutive duct sections  Minimise local loss coefficients of duct fittingsMinimise local loss coefficients of duct fittings  Select duct sizing methodsSelect duct sizing methods  Critical total pressure loss of tentative critical pathCritical total pressure loss of tentative critical path  Size branch ducts & balance total pressure atSize branch ducts & balance total pressure at junctionsjunctions  Adjust supply flow rates according to duct heat gainAdjust supply flow rates according to duct heat gain  Resize duct sections, recalculate & balance parallelResize duct sections, recalculate & balance parallel pathspaths  Check sound level & add necessary attenuationCheck sound level & add necessary attenuation
    • 98. Air Duct DesignAir Duct Design  Duct layoutDuct layout  Symmetric layout is easier to balanceSymmetric layout is easier to balance • Smaller main duct & shorter design pathSmaller main duct & shorter design path  For VAV systems, duct looping allows feedFor VAV systems, duct looping allows feed from opposite directionfrom opposite direction • Optimise transporting capacity (balance pointsOptimise transporting capacity (balance points often follow the sun’s position)often follow the sun’s position) • Result in smaller main ductResult in smaller main duct  Compare alternative layouts & reduce fittingsCompare alternative layouts & reduce fittings  For exposed ducts, appearance & integrationFor exposed ducts, appearance & integration with the structure is importantwith the structure is important
    • 99. Typical supply duct system with symmetric layout & looping
    • 100. Air Duct DesignAir Duct Design  Duct linerDuct liner  Lined internally on inner surface of duct wallLined internally on inner surface of duct wall  Mainly used for noise attenuation & insulationMainly used for noise attenuation & insulation  Fiberglass blanket or boardsFiberglass blanket or boards  Duct cleaningDuct cleaning  Prevent accumulation of dirt & debrisPrevent accumulation of dirt & debris  Agitation device to loosen the dirt & debrisAgitation device to loosen the dirt & debris  Duct vacuum to extract loosened debrisDuct vacuum to extract loosened debris  Sealing of access openingsSealing of access openings
    • 101. Duct breakout noise
    • 102. HVAC Piping SystemHVAC Piping System
    • 103. HVAC Instrumentation and ControlHVAC Instrumentation and Control
    • 104. HVAC System CommissioningHVAC System Commissioning  The key elements of commissioning include:The key elements of commissioning include:  Installation checks.Installation checks. Check installed equipment to ensure that all associatedCheck installed equipment to ensure that all associated components and accessories are in place.components and accessories are in place.  Operational checks.Operational checks. Verify and document that systems are performing as expected,Verify and document that systems are performing as expected, and that all sensors and other system control devices are properly calibrated.and that all sensors and other system control devices are properly calibrated.  Documentation.Documentation. Confirm that all required documentation has been provided, such asConfirm that all required documentation has been provided, such as a statement of the design intent and operating protocols for all building systems.a statement of the design intent and operating protocols for all building systems.  O&M manuals and training.O&M manuals and training. Prepare comprehensive operation and maintenancePrepare comprehensive operation and maintenance (O&M) manuals, and provide training for rig operations staff.(O&M) manuals, and provide training for rig operations staff.  Ongoing monitoring.Ongoing monitoring. Conduct periodic monitoring after the school is occupied toConduct periodic monitoring after the school is occupied to ensure that equipment and systems continue to perform according to design intent.ensure that equipment and systems continue to perform according to design intent.  Correctly implemented, commissioning is extremely cost-effective, and shouldCorrectly implemented, commissioning is extremely cost-effective, and should improve the delivery process, increase systems reliability, improve energyimprove the delivery process, increase systems reliability, improve energy performance, ensure good indoor environmental quality, and improve operation andperformance, ensure good indoor environmental quality, and improve operation and maintenance of the facility.maintenance of the facility.