Hvac Course

HVAC HVAC Design Principle course

Course content:  Air condition definition  HVAC Applications  Psychometric Process  AC main component cycle  Codes and standards  Equations for cooling load calculation  Cooling Load calculation software

What is the deference between CAV and VAV Central Air condition systems  Ceiling Concealed Duct    

Package Type VRF system Air handling Unit (AHU) Chilled water systems

Survey Pattern and understanding Architecture drawing Load calculation for project and System select using HAP

Chilled water system Design    

Pipe design FCU hock Up Chilled water Hock up Head Pump Calculation

VRF System design    

Features for VRF Indoor unit selection Outdoor unit sizing Joints and copper pipes sizing

Air Distribution Air Outlets Grills ,Diffusers Air Dumpers Air Ducts  Duct Types  Duct design

Air Filters Fans and ventilation Air condition System efficiency

Air condition Definition A system or process for controlling the temperature, humidity, and the purity of the air

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HVAC Application 7

Hotels

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Residential building

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Malls

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Office building

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Restaurants

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Hospital

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Oil and Gas Industry

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Telecom Industry

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Psychometric The sience which deals with the study of the behavior of air and water vapor mixture And its effect on human comfort

Psychometric properties The properties of water vapor and air mixture

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AIR properties Dry Bulb Temperature

(DBT)

Wet Bulb Temperature

(WBT)

Dew Point Temperature

(DPT)

Humidity Ratio

(H) (Ɯ)

Relative Humidity

(RH)

Specific volume Enthalpy

(V) (h)

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Dry Bulb temperature The temperature of air measured by thermometer

Sensible heat of air The quantity of heat that can be measured by measuring the dry bulb temperature of the air 19

Wet bulb temperature The temperature is measured by thermometer its bulb covered with wet cloth and is exposed to a current of moving air  WBT≤DBT  WBT=DBT (If air is 100% saturated)

Dew Point temperature At this temperature the air can no longer hold all of the water vapor and some of water vapor condense 20

FOG Phenomena …???

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Absolute Humidity It is the weight of water vapor in kg Air g/kg

Relative humidity The ratio of actual weight of water vapor to the weight of water vapor in saturated air at the same temperature and same volume (Unit less) 22

Psychometric Chart

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Comfort zone for human Dry bulb temp Relative humidity

24 C – 75.2 F 50%

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Comfort requirement not only temperature and humidity control Fresh air requirement Air distribution Noise level 30-55 db. lighting density

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Psychometric process Sensible Heating Sensible Cooling Humidification Dehumidification Adiabatic humidification Heating and Humidification Heating and dehumidification Cooling and dehumidification 26

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Sensible Heating Using Electrical Heater ,Steam ,Hot Water coil or Heat Pump Increase Dry bulb temperature without any change in humidity

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Sensible cooling Pass air in surface which its temp above Air dew point Decrease Dry bulb temperature without any change in Humidity

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Humidification Increase Humidity without any change in Dry bulb Temperature (evaporating latent)

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Dehumidification

Decrease humidity without any change in Dry bulb temperature ( cooling latent)

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Adiabatic Humidification (evaporating and cooling ) use air washer Increase humidity and decrease dry bulb temperature without any change in wet bulb temperature

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Humidification and Heating This process in Winter season in Dry weather Like Riyadh in winter Using (Air washer +Heating coil )

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Cooling and dehumidification We use this process in hot and high humidity weather like (Alexandria and Jeddah in summer season )

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Units...... imperial Units (British units)

SI metric units Eng.| Mohamed Saad HVAC design Principle

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Length

Unit conversion

M

CM

MM

Inch

feet

1

100

1000

39.37

3.28

Note : Inch =2.54 CM

Volume CMM

CFM

gpm

l/s

1

35.3

264.2

16.67

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Power HP

W

KW

1

746

0.746

Pressure bar

KPa

Ft wg

Psi

Kg/ CM3

1

100

33.455

14.7

1.0198

Cooling capacity TR

BTU/h

KW

w

1

12000

3.5

3516.8

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Definition of BTU The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit.

Quiz : How many Btu's are required to raise the temperature of 100 pounds of water from 72°F to 82°F? Eng.| Mohamed Saad HVAC design Principle

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Temperature

C=5/9 *(F-32) Where

C: is temperature in degree of Celsius

F: is temperature in degree of Fahrenheit Eng.| Mohamed Saad HVAC design Principle

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The Fahrenheit temperature scale places the zero where a salt-water mixture freezes, and has 180 divisions between the freezing and boiling points The Celsius temperature scale has 100 divisions between the freezing and boiling points of water.

C=5/9 (F-32) Eng.| Mohamed Saad HVAC design Principle

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AC main Component cycle

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P-H Chart

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Most popular Organization and it’s abbreviation

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ASHRAE American society of heating and refrigeration And Air conditioned Engineers SMACNA Sheet metal Air-conditioned National Association

AMCA Air movement and control Association Eng.| Mohamed Saad HVAC design Principle

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ARI Air conditioning and refrigerant institute ASME American Society of mechanical Engineers ANSI American national standard institute NFPA National Fire Protection Association NEMA National Electric Manufacture association Eng.| Mohamed Saad HVAC design Principle

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What the difference between code and standard….?

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Code provides mandatory guidelines for system design We can say its recommended method to do some thing

Standard Provides more specific details for the design of component Such as Dimensions and it is a degree of required quality Eng.| Mohamed Saad HVAC design Principle

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COOLING LOAD CALCULAIONS Eng.| Mohamed Saad HVAC design Principle

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Important definitions Heat Gain ) ‫(الحرارة المكتسبة‬ heat rate gain from external and internal sources

Cooling load ( ‫)حمل التبريد‬ Rate for extraction of heat required to maintain the air temperature and humidity inside the airconditioned places Eng.| Mohamed Saad HVAC design Principle

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Heat transfer methods Conduction Convection Radiation Eng.| Mohamed Saad HVAC design Principle

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Sources of heat External sources

Internal sources

-Heat transfer from wall and celling

-People -lighting

-Solar effect -Electrical equipment

-Ventilation and infiltration Eng.| Mohamed Saad HVAC design Principle

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Sources of heat Sensible Heat causes a change of temperature, but no change of state.

Latent heat causes a change of state, but no temperature change. During a change of state, the temperature remains constant until the change of state is completed.

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Design conditions Out Side design Condition

Inside design condition

DBT WBT RH% Elevation

DBT 22 -23-24-25

RH 45 -50 %

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Survey pattern  Walls directions of the building to count the effect of the sun and wind.  Dimensions of the building.  Construction materials for the building.  Glass of windows and quality of spaces and identify air leakage rates.  Occupancy conditioned persons of interest rates.  lighting rates and capabilities of the equipment motors.  Where I could feed the building with electricity and water.  The places available for the installation of air conditioning units and ducts ways Eng.| Mohamed Saad HVAC design Principle

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Cooling load calculation Manual Eng.| Mohamed Saad HVAC design Principle

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Lighting load ( Sensible load) Q light = Light intensity (W/m^2)* floor Area m^2

60 45 40 20 17 15

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Electrical Equipment 1- Get sensible and latent heat gain from tables 150 290 350 875

220 525 700 2190

515 930 1050 2190

For equipment with electrical motor

0.60 0.70 0.80 0.85 0.88

200 750 375 4 1 15 512 15

Q sensible = (1-ἠm) * motor power Eng.| Mohamed Saad HVAC design Principle

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Heat of occupants Air conditioned places get heat from occupants Because the difference between human body temperature 37 C and temperature in air conditioned places 24C

Q p,s = number of persons * QS/Person

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(W)

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total QL/person

97 117 132 132 146 162 229 293 292 425 425

31 45 59 59 73 81 139 183 204 255 255

66 72 73 73 73 81 81 110 88 170 170 Eng.| Mohamed Saad HVAC design Principle

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Ventilation load (sensible and latent)

Q vent , total = m’ air * (h o - h I )

How to get Air flow rate )m’ air( ?????? Eng.| Mohamed Saad HVAC design Principle

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Person requirement method 9.5 7.5 7 15 3.5 5 14 14 24 12 12.5 10 6 5

7 5 5 12 2.5 3.5 12 12 14 7 7.5 7.5 3.5 2.5

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Important note ASHRAE 62.1 2007 tables is updated in ventilation section – person requirement fresh air in air conditioned places per HSE laws as smoking is prevent in air conditioned places

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Floor area method and Air change method

)(

)L/S/m2(

1 1.5

1 1.4

2

1.8

3 4 5

2.8 3.7 4.6

4

7 9 11

6.7 8.3 10

2

)m2( 8

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Transmission load through walls, Celling, roof and doors

Q t = U A (T o - T I) U= overall heat transfer coefficient (W/m^2.K)

1/U = (1/ho)+

∑(x/k) + (1/hi)

K =thermal conductivity (w/m.k) h =convective heat transfer coefficient (w/m^2.k) X= wall thickness Eng.| Mohamed Saad HVAC design Principle

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K

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

(Common brick) (Face brick) (concrete) (Tiles) (Stone) (Cement plaster) (Gypsum plaster) (Hard wood) (Soft wood) (Sand) (Cork) (Glass wool) (Polystyrene) (Polyurethane) (Glass)

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Heat transferred through contact surfaces (Partitions)

Q=UAt

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(W)

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Solar heat gain

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

0.7 – 0.55 0.5 – 0.4 0.5 – 0.3 0.65 0.9 0.9 – 0.8

Q sun = U A (∆T sun) ∆T sun = ᾳ I /ho

I= max solar radiation intensity based on wall direction ( table )

ᾳ = Surface solar radiation absorptivity Eng.| Mohamed Saad HVAC design Principle

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Heat Transmission through glasses Normal method Q glass=SC * Ug * (To – T i) Where: SC Shade coefficient U g Heat transfer coefficient for glass material From ASHRAE 62.1 2007 tables

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Heat Transmission through glasses Glass load factor method Q glass = GLF * window area GLF : Glass load factor GLF based on glass type and window direction Get from ASHRAE From ASHRAE 62.1 2007 tables

Glass types : Regular single glass Regular double glass Heat Absorbing Double glass Clear triple glass Eng.| Mohamed Saad HVAC design Principle

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Hourly Analysis program (HAP)

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What is the difference between CAV and VAV systems Eng.| Mohamed Saad HVAC design Principle

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Variable air volume (VAV) A traditional VAV system consist of VAV box with a damper to control the volume of air delivered to a space

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• 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 is very low

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Advantages: High efficient and not very high initial cost Independent thermostat base space control High grade of flexibility

Disadvantages VAV box needs space Inefficient in different space applications Eng.| Mohamed Saad HVAC design Principle

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Air conditioners Eng.| Mohamed Saad HVAC design Principle

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DX systems conditioners Split units

Air Packaged units and window type MultiV (VRF)

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Split units

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Window type

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Air packaged units  Packaged roof top unit

 Packaged vertical unit

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Multi V type (VRF)

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Terminals units DX (Indoor units) Concealed Duct (high static) Concealed Duct (low static) Wall mounted Celling cassette 1way ,2 ways and 4 way

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Floor standing

Celling suspended

Celling floor Eng.| Mohamed Saad HVAC design Principle

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Chilled water systems Air cooled Chilled water

Water cooled chilled water (cooling tower)

Open discussion Eng.| Mohamed Saad HVAC design Principle

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Chilled water (Air cooled)

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Chilled water (water cooled )

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Chiller system P-only

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Two way Valve

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Three way Valve

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AHU

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Terminal units (Chilled water system) FAN COIL UNIT (FCU) -2 pipe FCU

- 4 pipe FCU

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Chilled water pumping systems  Primary system (P-only)  Conventional primary secondary System (P-S)

The distribution pumps primary pump for (P-only) and the secondary pump for (P-S) system are fitted with Variable Speed drive (VSD)

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Fresh Air system

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Fresh air system ventilation reclaim

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Mixing box How to calculate T mix Use this formula (V fresh + V return) T mix =(T o* V fresh )+ (Tr * V return)

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Chilled water system

Design Eng.| Mohamed Saad HVAC design Principle

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Design steps Find the cooling load for each zone Select the suitable cooling coil for each zone Get the total new cooling load by multiply by diversity factor Select suitable Air conditioned system for your project Select the suitable outdoor unit based on the cooling capacity and the ambient temperature Define the combination ratio between indoor load and outdoor unit capacity Eng.| Mohamed Saad HVAC design Principle

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Select the risers or mechanical shafts positions Connect the coils to the main branches and then to the riser Start the pipe sizing (chilled water or refrigerant pipes) Start to design ducts according to required Air flow rates

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Chilled water system design parameters Chilled water flow rate =2.4 GPM / TR Load (tons) = Flow (US gpm) x (°Fin – °F out)/24 Chilled water supply temperature = 7 C Chilled water return temperature = 12 C Minimum allowable flow velocity = 0.6 -3 m/s Allowable pressure drop through pipes 400 pa/m Eng.| Mohamed Saad HVAC design Principle

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Piping design Important notes Decrease Pipe length as possible as Decrease number of Elbows and Tees to decrease system initial cost Decrease pressure drop in pipes to decrease system running cost Eng.| Mohamed Saad HVAC design Principle

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2 inch (50.8 mm) pipe diameter • Incase pipe diameter lower than 2 inch ,water speed should not exist 1.2 m/s or 4 F b S • Incase pipe diameter 2 inch or more than this value ,pressure drop not exist 400 pa/m

This values according to ASHRAE but we should consider that we don’t deal with ideal materials and ideal welding Eng.| Mohamed Saad HVAC design Principle

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Pipe material The second factor we should consider in piping design is pipe material Steel PVC Aluminum Cupper Eng.| Mohamed Saad HVAC design Principle

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Important definition Nominal pipe diameter Internal pipe diameter Example : 1 inch nominal pipe diameter =25.4 mm You will find internal pipe diameter higher than 25.4 mm Eng.| Mohamed Saad HVAC design Principle

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Friction loss for pipe steel SCH 40

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Pressure drop in elbows or tee connection

∆P= K * Ᵽ * (v^2/2g) Use tables to get K and charts to get v

Where

K Ᵽ V g

pressure drop factor water density kg/m^3 water speed m/s gravity m/s^2 Eng.| Mohamed Saad HVAC design Principle

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Piping design software Pipe Sizer by mcQuay version 6.2 Pipe flow advisor Pipe flow wizard Pipe flow expert

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Pipe flow wizard software

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Total Dynamic Head Pump Calculation  Get Pressure drop in chiller

(from Catalogue)

 Get Pressure drop in AHU or FCU

(from Catalogue)

 Get Pressure drop in two way valve

(from Catalogue)

 Calculate Pressure drop in pipe supply and return

Take Safety factor 10 or 20% Eng.| Mohamed Saad HVAC design Principle

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pressure drop in chilled water calculation To calculate the total pressure drop we should study the worst piping pass The farthest fan coil not should be the worst piping pass ,we should consider elbows and tee connection

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VRF System Design

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Air outlets • Grill

• Linear bar grill

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• Ceiling diffuser (Square – rectangular round)

• Linear bar diffuser

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Air distribution Important definition Throw Drop

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AIR Ducts Eng.| Mohamed Saad HVAC design Principle

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Duct material Galvanized sheet metal duct Pre-insulated Aluminum Duct Fiberglass duct-board Spiral metal duct Flexible duct Textile duct

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Supply duct system Distributes air to the terminal units , diffusers in the conditioned spaces

Duct systems: Plenum system Extended plenum system Reducing Plenum system Perimeter loop Eng.| Mohamed Saad HVAC design Principle

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Plenum system Suited for a job where the room outlets are all close to the unit

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Extended plenum system (Trunk duct System) Can be applied to a long structure ,this system takes the plenum closer to the farthest Point, low noise level applications

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Reducing plenum system Reduce 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

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Perimeter loop system Well suited for installation in a concrete floor in heating application , Provides the same pressure to all outlets

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Duct system combination Metal trunk lines with round branch ducts Metal trunk lines with flexible branch ducts Duct board trunk lines with round metal branch duct Duct board trunk lines with flexible branch duct Round metal duct with round metal branch duct round metal trunk lines with flexible branch duct

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Return duct

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Fire damper Installed in the return duct before air enter AHU. To Prevent air return to AHU in case of fire

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Duct design Eng.| Mohamed Saad HVAC design Principle

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Important notes • Decrease duct length as possible as • Decrease number of fittings and elbows to decrease initial cost , and decrease pressure drop to decrease running cost

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Ducts types Round Ducts

Rectangular ducts

Low pressure drop

High pressure drop

High initial cost because high manufacturing cost and high insulation cost

Low initial cost compared with round ducts

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Air duct design Consideration We should consider the following parameter when we design ducts  Heat loss or gain through air ducts  Maximum allowable aspect ratio  Air friction loss  Elbow and fitting used

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low velocity air duct system V air =6-12 m/s ∆P=0.8 -1.5 Pa/m

High velocity air duct system V air=12-30 m/s ∆P=3-5 Pa/m Eng.| Mohamed Saad HVAC design Principle

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Air duct design steps • Building drawing • Select Air duct system (plenum ,extended plenum ,reduced plenum ,perimeter). • Select air outlet positions (supply &return) • Duct routing (single line) • Identify Air flow in duct sections • Find duct dimensions • Find the total pressure drop to select the proper fan section Eng.| Mohamed Saad HVAC design Principle

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Two methods to get duct dimension • Constant friction method ‫ى‬ • Velocity

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Equal friction method

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Convert from round duct to rectangular duct

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Duct sizer soft ware

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Duct thickness and duct Gauge

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How to calculate Metal Sheet weight required for your project? Duct Weight = 0.4 * (W+H) * t * L Where:W = duct width (inch) H = duct depth (inch) t = duct thickness (mm) L = duct length (m)

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Thermal insulation Using fiberglass material Internal insulation thickness = 1 inch External insulation thickness = 2 inch

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Air fans Provide the pressure difference to moves the air through the duct system and outlets with a proper velocity

Total pressure in duct system =Static pressure + velocity pressure Eng.| Mohamed Saad HVAC design Principle

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Air fans Centrifugal fans Used in exhaust air • Desirable for system. ductwork. Will handle large volumes • Builds more pressure of air at from the inlet to the low pressure differentials. outlet. Makes noise and is used • Very quiet when where noise is not a properly applied. factor. • Can be used in very large high pressure systems.

Propeller fans • •

• •

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Fan type

Forward curved

Backward curved

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Radial

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Direct drive motor assembly

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Belt driven assembly

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Ventilation Ventilation is to reduce high latent heat CO2,contaminants and toxic gases in the space by means of supplying fresh air to keep the minimum permissible concentration of each in the space. That to maintain a healthy space Eng.| Mohamed Saad HVAC design Principle

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Ventilation types • Local ventilation (mechanical): The ventilation spot at the point of harmful gases generation using hoods . that to avoid the spread of gases in the space (kitchen and workshops)

• Central ventilation (mechanical) It is allow air change allover the space and not spotted at the contaminate point (Garage and factories ). The supply point is preferable to be lower than exhaust air point Eng.| Mohamed Saad HVAC design Principle

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Ventilation types Positive ventilation Negative ventilation Balanced ventilation

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Local ventilation (HOOD) Negative Pressure

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Air Filters Air Filter types: -washable filter (Aluminum mesh) -Bag filter -Box filter -throwaway filter -Pleated filter -cartage filter

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(MERV) Minimum. Efficiency Reporting. Value ASHRAE standard 52.5 Eng.| Mohamed Saad HVAC design Principle

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Typical applications for the major MERV value ranges  MERV 1 – 4 Minimum filtration, used almost exclusively in residential buildings  MERV 5 – 8 Most commercial applications and better residential buildings  MERV 9 – 12 Superior residential buildings and better commercial buildings  MERV 13 – 16 Hospital inpatient and general surgery; found in superior commercial buildings  MERV 17 – 20 Clean rooms and pharmaceutical manufacturing Eng.| Mohamed Saad HVAC design Principle

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How to get pressure drop in Air filter

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Air condition System efficiency

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Coefficient of Performance COP The Coefficient of Performance - COP - is the basic parameter used to report efficiency of refrigerant based systems. The Coefficient of Performance - COP - is the ratio between useful energy acquired and energy applied and can be expressed as COP = Eu / Ea

where  COP = coefficient of performance  Eu = useful energy acquired  Ea = energy applied Eng.| Mohamed Saad HVAC design Principle

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COP can be used to define both cooling efficiencies or heating efficiencies Cooling - COP is defined as the ratio of of heat removal to energy input to the compressor Heating - COP is defined as the ratio of heat delivered to energy input to the compressor higher COP - more efficient system COP can be treated as an efficiency where COP of 2.00 = 200% efficiency. Eng.| Mohamed Saad HVAC design Principle

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Energy Efficiency Ratio EER

The Energy Efficiency Ratio - EER - is a term generally used to define cooling efficiencies of unitary air-conditioning and heat pump systems. The efficiency is determined at a single rated condition specified by an appropriate equipment standard and is defined as the ratio of net cooling capacity - or heat removed in Btu/h - to the total input rate of electric power applied - in Watts. The units of EER are Btu/Wh. Eng.| Mohamed Saad HVAC design Principle

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EER = Ec / Pa where • EER = energy efficient ratio (Btu/Wh) • Ec = net cooling capacity (Btu/h) • Pa = applied electrical power (Watts)  This efficiency term typically includes the energy requirement of auxiliary systems such as the indoor and outdoor fans. • higher EER - more efficient system • Eng.| Mohamed Saad HVAC design Principle

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BMS All buildings have mechanical and electrical service . These services need to be controlled By some means (BMS) in order to ensure comfort conditions

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BMS functions Central controlling facilities Automatically control various operation Manage and coordinate various systems Provides a comfortable conditions in efficient way .System to be controlled (lighting ,fire fighting ,Smoke management ,HVAC, audio-visual and attendance reporting Eng.| Mohamed Saad HVAC design Principle

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BMS Smoke management is to pressurize the staircase and escape paths and exhaust the smoke from the required space

In case of fire elevators have to be stopped and direction signs should be operate In case of electric shutdown, the backup system has to operate the system partially with minimum hazardous requirements Eng.| Mohamed Saad HVAC design Principle

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