HVAC Course

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HVAC

HVAC Course

Course

Dr. Eng. Ahmed Rezk Assistant professor

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Introduction

• Definition: it is the process of altering the air properties (temperature, humidity, quality and distribution) to more favorable conditions. Air

conditioning can refer to cooling, heating,

ventilation or disinfection, that modifies the condition of air.

• Atmospheric air always contains water vapor. The content of water vapor in air also plays an important role in comfort air-conditioning.

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Air conditioning systems (HV

Air conditioning systems (HVAC

AC

AC))))

Open discussion Open discussionOpen discussion Open discussion

Air conditioners

Room AC Central AC

DX systems

Package units Split units

Using - AHU Using - VAV

Hydronic system Using high wall FCU Using C - C FCU Using - AHU Evaporative coolers

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Air properties

• Psychrometry: The science which deals with the study of the behavior of air and

water vapor mixture is known as

psychrometry. The properties of water vapor and air mixture are known as psychometric properties.

• Dry air: The mixture of nitrogen and oxygen neglecting the water vapor and other gases is known as dry air.

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Air properties

• Moist air: It is a mixture of dry air and water vapor. The quantity of water vapor present in air depends upon the temperature of the air. • Moisture: The water vapor present in the

air is known as moisture and its quantity in air is an important factor in all air-conditioning system.

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Air properties

• Dry bulb temperature: The temperature of air measured by ordinary temperature thermometer is known as dry-bulb temperature.

• Wet bulb temperature: The temperature recorded by a thermometer when its bulb is covered with wet cloth and is exposed to a current of moving air is known as wet bulb temperature.

• Dew point temperature: it is the temperature at which the air can no longer "hold" all of the water vapor which is mixed with it, and some of the water vapor must condense into liquid water.

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Air properties

• Specific humidity (humidity ratio): It is the weight of water vapor present per kg of dry air.

• Relative humidity: It is defined as the ratio of actual weight of water vapor in a given volume to the weight or water vapor contained in the same volume at the same temperature when the air is saturated.

• Sensible heat of air: The quantity of heat that can be measured by measuring the dry bulb temperature of the air.

• Total heat: The total heat of the humid air is the sum of the sensible heat of the dry air and latent heat of water vapor associated with dry air.

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Air properties

Comfort Zone

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Psychrometric

Psychrometric processes

processes

Sensible heating Sensible cooling

Heating and humidification

Cooling and dehumidification

Humidification

Dehumidification Adiabatic humidification

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Psychrometric

Psychrometric processes

processes

• Cooling and dehumidification: It can be achieved by using cooling coil of surface temperature below dew point temperature. That to allow water vapor in the air to be condensed.

Supply Air

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Psychrometric

Psychrometric processes

processes

Conditioned air production

• The supply air can be reconditioned after removing the space load (all return), it can be mixed with fresh air to reduce the space air contamination (mixed), or we can use totally fresh air in special requirements (all fresh).

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Supply Air Room Air Outside Air Supply Air Room Air Outside Air Mixed Air

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Psychrometric

Psychrometric processes (humid summer)

processes (humid summer)

• Cooling coil capacity [ CCC ]

• Amount of condensate [ m_w ]

• Sensible heat factor [ SHF ] • Bypass factor [ BPF ]

1

2 S

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Psychrometric

Psychrometric processes

processes

• Sensible heating: the heating can be achieved by electrical heaters, steam, hot water coil or heat pumps.

• Sensible cooling: It can be achieved by cooling coil of surface temperature higher than the dew point temperature (where no water vapor condensation). The cooling coil could be DX coil or chilled water coil.

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Psychrometric

Psychrometric processes

processes

• Humidification: it can be produced by supplying saturated steam at a temperature equal to dry bulb temperature of the air.

• Adiabatic dehumidification: It is a special process that can be done DESCICANTS (ex, Silica gel).

• Adiabatic cooling: It can be done by direct contact between water (droplet in air washer or mist in ultrasonic mist maker) and air.

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Psychrometric

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Comfort

requirements

not

only

temperature

and

humidity

humidity control

control

control....

control

• Minimum fresh air requirements. • Lighting density.

• Air distribution and velocity. • Noise level (30-55 db).

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Cooling load calculation

• The cooling load calculations have to be done very accurate, not to overestimate or underestimate the required systems capacities. The following parameters are required for cooling load calculations:

• Building drawings including the geographical directions. • Rooms dimensions and applications.

• Structure materials.

• Windows and doors areas. • Rooms occupancy.

• Lighting type and distribution. • Appliances available in the space • Infiltration sources.

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Cooling load calculation

• Methods of cooling load calculations

• Using estimated load per surface area based on applications. • Accurate manual calculations.

• Using Hourly Analysis Program (HAP).

• Ton of refrigeration: A ton of refrigeration (commonly abbreviated as TR) is a

unit of power used to describe the heat-extraction capacity of refrigeration and air conditioning equipment.

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Cooling load calculation

Cooling load calculation (Manually)

(Manually)

• Load components

• Transmission load through walls, celling and roof. • Solar heat gain.

• Heat gain through windows, and doors. • Occupants heat gain (sensible, latent).

• Appliances heat gain (sensible and latent). • Light heat gain.

• Ventilation load (sensible and latent). • Infiltration load (sensible and latent).

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Cooling load calculation (Manually)

• Outside design conditions

• You can get the information from the ASHRAE or using Weather Underground website. (http://www.wunderground.com/q/zmw:00000.1.62318?)

• Inside design conditions.

• Inside dry bulb temperature and relative humidity are depend on the application. • residential (24°C / 50%) • Textile (24°C / 65%) • Printing (27°C / 45%) • Sweets (25°C / 33%) • Leather (32°C / 75%)

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Cooling load calculation (Manually)

• Transmission load through walls, celling, roof and doors.

= − 1 = ℎ1 + + ℎ1 حطسلا ةيعون ةرارحلا هاجتا h نكاس ءاوھ ـ أ يقفأ يقفأ يسأر كرحتم ءاوھ ـ ب ةعرسب 6.7 رتم / ةيناث ةعرسب 3.4 رتم / ةيناث ىلعأ ىلإ لفسأ ىلإ يقفأ هاجتا يأ هاجتا يأ 10 6 8 34 23

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Cooling load calculation (Manually)

• Transmission load through walls, celling and roof.

• U= overall heat transfer coefficient (W/m2_k)

• K= thermal conductivity (W/mk)

• h= convective heat transfer coefficient (W/m2_K)

Material K يداع بوط هجاو بوط ةناسرخ طلاب ةراجح ةيتنمسا ةنوم ةيسبج ةنوم فشان بشخ يرط بشخ لمر نيلف يجاجز فوص نيرتسلوب ناسيرا يلوب جاجز (Common brick) (Face brick) (concrete) (Tiles) (Stone) (Cement plaster) (Gypsum plaster) (Hard wood) (Soft wood) (Sand) (Cork) (Glass wool) (Polystyrene) (Polyurethane) (Glass) 0.72 1.30 1.72 1.10 1.80 0.72 0.80 0.16 0.12 1.72 0.036 0.036 0.040 0.023 0.79

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Cooling load calculation (Manually)

• Solar heat gain

• Solar heat gain is due to solar radiation.

• Part of the solar radiation will be absorbed and the other will be reflected.

= ∆

∆ = _ℎ

• I= max solar radiation intensity based on wall direction (tabulated) • α= surface solar radiation absorptivity.

حطسلا ةدام α يريج يلمر رمحأ بوط يريج يلمر ضيبأ بوط ةيريج ةراجح يناسرخ طلاب يتلفسأ فقس يدامر زاودرا 0.55 – 0.7 0.4 – 0.5 0.3 – 0.5 0.65 0.9 0.8 – 0.9

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Cooling load calculation (Manually)

• Heat transmission through glasses

• Glass Load Factor (GLF) method.

= ∗ !" #$%# • GLF based on window type and direction (ASHRAE)

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Cooling load calculation (Manually)

• Heat transmission through glasses

• Normal method.

= &' ∗ ∗ − • For shade coefficient (SC) and Ug (ASHRAE)

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Cooling load calculation (Manually)

• Occupants heat gain: Heat gain due to people activities.

• _(, = *₊ ∗ _/+ • _(,- = *₊ ∗ _-/+ ناسنلإا ةلاح مادختسلاا ةرارح ةسوسحم W ةرارح ةسوسحم W عومجملا W حيرتسمو سلاج فيفخ لمع لمعيو سلاج طسوتم لمع لوازي فيفخ لمع لوازيو فقاو ءطبب يشمي سلاج طيسب لغش لوازي كرحتم لماع طسوتم لغش لوازي لماع ليقث لغش لوازي لماع ةضاير لوازي صخش حرسم قنف ـ ةقش ـ بتكم د قدنف ـ ةقش ـ بتكم ةيراجت تلاحم كنب معطم عنصم عنصم عنصم عنصم بعلم 66 72 73 73 73 81 81 110 88 170 170 31 45 59 59 73 81 139 183 204 255 255 97 117 132 132 146 162 229 293 292 425 425

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Cooling load calculation (Manually)

• Lighting load (sensible only)

_. = /ℎ0 0% 102 ∗ 3""$ $%# ىنبملا ةيعون ةءاضلإا ةدش بتاكم عناصم تاعماج ـ سرادم قدانف ـ حرسم ـ جردم ـ ةقش معاطم فحاتم ـ تابتكم ـ تايفشتسم 60 45 40 20 17 15

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Cooling load calculation (Manually)

• Appliances heat gain (sensible and latent)

• For equipment with electric motor. • _4 54 = 6₇ ∗ 8"0"$ 9"%$ دقوملا عون دوھ نودب دوھ عم ةسوسحم ةرارح ةنماك ةرارح ةسوسحم ةرارح ةوھق دقوم يداع دقوم رتسوت خارف ةياوش 515 930 1050 2190 220 525 700 2190 150 290 350 875 روتوملا ةردق ةءافكلا نم لقأ 200 تاو نم 375 ىلإ 750 تاو نم 1 ىلإ 4 تاو وليك ىلإ نم 15 تاو وليك نمر بكأ 15 تاو وليك 0.60 0.70 0.80 0.85 0.88

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Cooling load calculation (Manually)

• Ventilation load (sensible and latent)

_:4, = 8_;. ∗ ℎ − ℎ _:4,4 54 = 8_;. ∗ ℎ − ℎ

_:4,4 = 8_;. ∗ ℎ − ℎ • Air flow rate

• Air change method • Floor area method

• Person requirements method

ناكملا صاوخ ةيوھتلا لدعم ) L/S/m2 ( رييغت تارم ددع ةعاس لك ءاوھلا ) ξ ( نيخدتلا لكل ةيضرلأا ةحاسم₍_m2₎_صخش دجاوتلا ةلاح يواخ لمعم ـ كنب معطم بتكم 8 عونمم ًانايحأ ًامئاد 1 1.4 1.8 1 1.5 2 ظتكم ةماع فرغ قدانف 4 عونمم ًانايحأ ًامئاد 2.8 3.7 4.6 3 4 5 محدزم ةلاص ـ راب 2 عونمم ًانايحأ 6.7 8.3 7 9

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Cooling load calculation (Manually)

• Ventilation rate L/s/person

مادختسلاا نيخدتلا ةيوھتلا تلادعم ىندلأا لضفملا ةقش كنب نولاص راب ةيراجت تلاحم عناصم تايفشتسم قدانف تاعامتجا فرغ ةيصوصخ بتاكم ةماع بتاكم معاطم ايريتفك ًانايحأ ًانايحأ ًانايحأ ديدش عونمم عونمم عونمم ديدش ديدش ًانايحأ ًانايحأ ًانايحأ ًانايحأ 7 5 5 12 2.5 3.5 12 12 14 7 7.5 7.5 3.5 9.5 7.5 7 15 3.5 5 14 14 24 12 12.5 10 6

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Cooling load calculation (Manually)

• Infiltration load

_=, = 8_;. ∗ ℎ − ℎ _=,4 54 = 8_;. ∗ ℎ − ℎ

_=,4 = 8_;. ∗ ℎ − ℎ • Infiltration rate through cracks (L/s/m)

رصنعلا ءاوھلا ةعرس ) m/s ( 2 5 تلاصفمب يبشخ راطإ وذ كابش : ماكحلإا ديج ماكحلإا فيعض قلزنم وأ تلاصفمب يندعم راطإ وذ كابش بيكرتلا ديج يجاجز باب يندعم وأ يبشخ باب : بيكرتلا ديج 0.19 0.70 0.16 5 1.4 10 2.87 0.82 15 2.8

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Cooling load calculation (Manually)

• Infiltration rate based on application (ACH)

فرغلاو ىنبملا ةيعون ) ξ ( ةيداع ذفاون ةمكحم ذفاون لوخدلا تلااص لابقتسلاا تلااص تامامحلا عم باب وأ ةذفان : دحاو طئاح نيطئاح طئاوح ةثلاث طئاوح ةعبرأ ةيراجت تلاحم 1.2 – 1.8 1.2 1.2 0.75 1.5 2 2 2 0.6 – 0.9 0.6 0.6 0.5 0.75 1 1

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-Air conditioning systems (HV

Air conditioning systems (HV

Air conditioning systems (HVAC

AC

AC))))

Air conditioning systems

Package units Roof top ducted Vertical ducted Split units Ducted Terminals Decorative ductless AHU Decorative ductless Ducted FCU AHU Decorative Ductless VRV Hydronic

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Air conditioning systems (HV

Air conditioning systems (HVAC

AC

AC))))

• Package unit, Roof top ducted • Cooling capacity (4–20 TR)

• Applications

• Banks

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Air conditioning systems (HV

Air conditioning systems (HVAC

AC

AC))))

• Package unit, Vertical ducted • Cooling capacity (4–20 TR) • Applications

• Banks

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Air conditioning systems (HV

Air conditioning systems (HVAC

AC

AC))))

• Package unit, decorative ductless • Cooling capacity (Up to 2 TR)

• Residential applications • Easy to install

• Easy maintenance • Noisy

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Air conditioning systems (HV

Air conditioning systems (HVAC

AC

AC))))

• Split unit, Decorative ductless • Cooling capacity (Up to 2 TR) • Residential applications

• Easy to install

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Air conditioning systems (HV

Air conditioning systems (HVAC

AC

AC))))

• Decorative ductless split and package units

• Less expensive to operate than central units.

• Their efficiency is generally lower than that of central air conditioners. • Does not need special electrical current specifications.

• Its maintenance cost is very low compared by central or mini central. • Split units is more preferable than window units in term of noise and

shape.

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Air conditioning systems (HV

Air conditioning systems (HVAC

AC

AC))))

• Split unit, Ducted terminal (small capacity, mini central)

• The outdoor metal cabinet contains the condenser and compressor, and an indoor cabinet contains the evaporator

• Capacity of (1.5-5 TR)

• Its common name is (ceiling concealed ducted CCD) • Applications

• Banks

• Residential (villas)

• Small administrative building • Retails

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Air conditioning systems (HV

Air conditioning systems (HVAC

AC

AC))))

Return air could be free return or ducted return

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Air conditioning systems (HV

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• Split unit, AHU

• Used in special air requirement.

• Clean rooms.

• Special industrial applications.

• Comfort applications of special requirement. • Cooling capacity depends on the manufacturer.

Air conditioning systems (HV

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Air conditioning systems (HV

Air conditioning systems (HVAC

AC

AC))))

• VRF system

• Multi-split system turn on / off based on master controller.

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Air conditioning systems (HV

Air conditioning systems (HVAC

AC

AC))))

• VRF system

• The modern VRF technology uses an inverter-driven scroll compressor and permits as many as 48 or more indoor units to operate from one outdoor unit.

• The inverter scroll compressors are capable of changing the speed to follow the variations in the total cooling load as determined by the suction gas pressure measured on the condensing unit.

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Air conditioning systems (HV

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Air conditioning systems (HV

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Air conditioning systems (HV

Air conditioning systems (HVAC

AC

AC))))

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Air conditioning systems (HV

Air conditioning systems (HVAC

AC

AC))))

• Chilled water system, Ducted FCU • Chilled water system, AHU

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Air conditioning systems (HV

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Variable air volume (VAV) system

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Variable air volume (VAV) system

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Variable air volume (VAV) system

• A traditional VAV system consists of a VAV box with a damper to control the volume of air delivered to a space. When the space approaches design conditions, the damper may close to provide only 15% of the design cfm.

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Variable air volume (VAV) system

• Fan Powered VAV: The addition of a fan to a VAV box improves air movement at times when a space is near its design temperature and supply air volumes are low

• Advantages:

• High efficient and not very high initial cost. • Independent thermostat base space control. • High grade of flexibility.

• Disadvantages

• VAV box needs space.

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Notes

• Air has to be conditioned in most cases for us to be comfortable.

• Equipment includes cooling coil, heating device, device to add humidity, and device to clean air.

• Air systems use the same room air over and over again.

• Fresh air enters the structure by infiltration or by mechanical means. • Different spaces require different air quantities.

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Air distribution

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Air outlets

Jet diffuser _{2 way square diffuser}

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Air outlet selection

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Air outlet

Air outlet distribution and distances

distribution and distances

Living Room 300 cfm 100 cfm 100 cfm 200 cfm 100 cfm 200 cfm 50 cfm 100 cfm 50 cfm

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Supply duct system

• Distributes air to the terminal units, diffusers in the conditioned space • Duct systems

• Plenum system

• Extended plenum system • Reducing plenum system • Perimeter loop

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Plenum system

• Suited for a job where the room outlets are all close to the unit.

Return duct

Supply plenum

Branch ducts

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Extended

Extended plenum (trunk

plenum (trunk

plenum (trunk duct)

duct)

duct) system

duct)

system

• Can be applied to a long structure.

• This system takes the plenum closer to the farthest point.

• Low noise level applications.

Living Room 9,000 btu (cooling) 18,000 btu (heating)

300 cfm 100 cfm 100 cfm 200 cfm 100 cfm 200 cfm 50 cfm 100 cfm 50 cfm

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Reducing plenum system

• Reduces the trunk duct size as branch ducts are added

• Has the advantage of saving material

and keeping the

same pressure from one end of the duct system to the other

Living Room 9,000 btu (cooling) 18,000 btu (heating)

300 cfm 100 cfm 100 cfm 200 cfm 100 cfm 200 cfm 50 cfm 100 cfm 50 cfm

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Perimeter loop system

Living Room 9,000 btu (cooling) 18,000 btu (heating) 300 cfm 100 cfm 100 cfm 200 cfm 100 cfm 200 cfm 50 cfm 100 cfm 50 cfm

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Perimeter loop system

• Well suited for installation in a concrete floor in a colder climate (heating applications).

• Warm air is in the whole loop when the fan is running. • Keeps the slab at a more even temperature.

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Duct materials

• Ductwork must meet local HVAC code.

• Galvanized sheet metal was used exclusively. • Other ductwork materials.

• Pre-insulated Aluminum duct. • Fiberglass duct-board.

• Spiral metal duct. • Flexible duct.

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Fiberglass duct-board

Flexible duct Spiral duct

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Galvanized steel duct assembly

• Metal duct can be round, square, or rectangular

Slip Drive cleat J O I N I N G S E C T I O N S O F G A L V A N I Z E D D U C T J O I N I N G S E C T I O N S O F G A L V A N I Z E D D U C T J O I N I N G S E C T I O N S O F G A L V A N I Z E D D U C T J O I N I N G S E C T I O N S O F G A L V A N I Z E D D U C T

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Galvanized steel duct assembly

Ends of drives are bent over to secure

Slip J O I N I N G S E C T I O N S O F G A L V A N I Z E D D U C T J O I N I N G S E C T I O N S O F G A L V A N I Z E D D U C T J O I N I N G S E C T I O N S O F G A L V A N I Z E D D U C T J O I N I N G S E C T I O N S O F G A L V A N I Z E D D U C T W I T H S L I P S A N D W I T H S L I P S A N D W I T H S L I P S A N D W I T H S L I P S A N D D R I V E SD R I V E SD R I V E SD R I V E S

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Other duct types

• Fiberglass duct-board.

• Flat sheet or round prefabricated cut

• Duct is normally 1’’ thick with aluminum foil backing • All duct seams should be stapled and taped

• Spiral metal duct

• Used more on large systems.

• Comes in rolls of flat narrow metal. • Runs can be made at the job site.

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Combination duct system

• In HVAC duct work you may find the following combinations

• Metal trunk lines with round branch ducts. • Metal trunk lines with flexible branch ducts.

• Ductboard trunk lines with round metal branch ducts. • Ductboard trunk lines with flexible branch ducts.

• Round metal duct with round metal branch ducts. • Round metal trunk lines with flexible branch ducts.

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Duct air movement

• Branch ducts are fastened to the main trunk by a takeoff-fitting. • The takeoff encourages the air to enter the branch duct.

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Balancing

Balancing (volume)

(volume)

(volume) dampers

dampers

• Used to balance the air in various parts of the system.

• Dampers should be located as close as practical to the trunk line.

• Handles allow the dampers to be turned at an angle to the airstream to slow the air down.

Branch duct

Balancing damper in the closed position

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Duct insulation

• About 10°C temperature difference from the inside of the duct to the outside of the duct is considered the maximum difference allowed. • Metal duct can be insulated on the outside and on the inside.

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Central

Central Return duct

Return duct

Supply plenum

Return plenum

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Individual return duct

R S

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Air duct design (consideration)

• The following parameters are considered

• Heat loss or gain through air duct. • Maximum allowable aspect ratio. • Air friction loss.

• Used fittings.

• Low velocity air duct system

• V_air = 6 - 12 m/s

• ΔP = 0.8 – 1.5 Pa/m

• High velocity air duct system

• V_air = 12 - 30 m/s • ΔP = 3 – 5 Pa/m

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Air duct design

Air duct design (steps)

(steps)

• Building drawings.

• Select air duct system (plenum, extended plenum, reduced plenum, perimeter).

• Select air outlet positions (supply and return).

• Select air outlets types based on air volume and distribution. • Duct routing (the simplest and shortest).

• Find duct dimensions.

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Friction chart for round duct

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Convert from round duct to rectangular duct

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U

Using duct

sing duct

sing duct----sizer

sing duct

sizer

sizer software

software

Step-1 Step-2 Step-3 _Step-4

Modify your dimensions

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Air fans

• Provides the pressure difference to moves the air through the duct system, dampers and outlets with a proper velocity.

• Typically 400 CFM_air/TR for DX coils and 350 CFM_air/TR for chilled

water coils.

• Duct system pressures.

• Static pressure. • Velocity pressure.

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Air fans

Air fans Propeller fans Centrifugal fans

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Air fans

Air fans Propeller fans Centrifugal fans

• Used in exhaust air system.

• Will handle large volumes of air at low pressure differentials.

• Makes noise and is used where noise is not a factor.

• Desirable for ductwork.

• Builds more pressure from the inlet to the outlet.

• Very quiet when properly applied. • Can be used in very large

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high-Air fans

Air fans

DIRECT DRIVE MOTOR ASSEMBLY DIRECT DRIVE MOTOR ASSEMBLY DIRECT DRIVE MOTOR ASSEMBLY DIRECT DRIVE MOTOR ASSEMBLY

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Air fans

BLOWER

MOTOR

BOTH BOTHBOTH

BOTH THETHETHETHE DRIVEDRIVEDRIVE ANDDRIVE ANDANDAND DRIVEN

DRIVENDRIVEN

DRIVEN PULLEYSPULLEYSPULLEYSPULLEYS MUSTMUSTMUSTMUST BE

BEBE

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