Ducting & Duct Ducting & Duct LayoutLayout

System PressureSystem Pressure

Pt = Ps + PvPt = Ps + Pv

Outlet Velocity of Fan = cfm / outlet areaOutlet Velocity of Fan = cfm / outlet area Ps = Pt – PvPs = Pt – Pv

In a constant cross section area duct Pv is In a constant cross section area duct Pv is constant .constant .

Pv reduces along its length Pv reduces along its length

System PressureSystem Pressure

Friction in a duct leads to loss of energyFriction in a duct leads to loss of energy Friction in a duct causes loss of Total Pressure Friction in a duct causes loss of Total Pressure Velocity Pressure is small at the fan outletVelocity Pressure is small at the fan outlet

Conventionally Static Pressure in a duct is Conventionally Static Pressure in a duct is used for design, but total pressure developed used for design, but total pressure developed is to be considered to calculate is to be considered to calculate total ,mechanical energy to be supplied total ,mechanical energy to be supplied

Friction Loss Friction Loss

Ps : Is lost along the length of the ductPs : Is lost along the length of the duct

∆∆Pt = f Pt = f DD X ( X ( ccff44 X L/D ) X Pv X L/D ) X Pv∆∆Pt = Friction Loss in inchesPt = Friction Loss in inchesf D = Friction roughness based on Reynolds no. is 0.0005 f D = Friction roughness based on Reynolds no. is 0.0005

for GI sheet duct with 40 joints per 100 feetfor GI sheet duct with 40 joints per 100 feet

cf4cf4 = Conversion factor = 12 = Conversion factor = 12L= Length of duct in feet ( say 100 feet )L= Length of duct in feet ( say 100 feet )D= Inside Duct diameter in inches D= Inside Duct diameter in inches

Friction LossFriction Loss

Based on Air being incompressible & Based on Air being incompressible & density of air = 0.075 lbs/cu ftdensity of air = 0.075 lbs/cu ft

∆∆Pt = f Pt = f DD X ( X ( ccff44 X L/D ) X Pv X L/D ) X PvWith the above values and assumptions With the above values and assumptions

becomes :becomes : ∆∆Pt = 0.0005 Pt = 0.0005 X (12 X (12 X 100 /D ) X PvX 100 /D ) X Pv ( Friction Loss( Friction Loss ) )

Friction Loss Friction Loss

Some values of Some values of ff D : D : also designated as < ( epsilon )also designated as < ( epsilon )

Carbon Steel Sheet : 0.0005Carbon Steel Sheet : 0.0005Aluminium Sheet , 12jts/100ft : 0.0001Aluminium Sheet , 12jts/100ft : 0.0001GI Sheet Contin Roll, 12 jts/100 ft : 0.0001GI Sheet Contin Roll, 12 jts/100 ft : 0.0001Spiral GI Duct rigid, 25 jts/100ft : 0.0003Spiral GI Duct rigid, 25 jts/100ft : 0.0003FRP Duct : 0.003FRP Duct : 0.003FRP Liner : 0.003FRP Liner : 0.003Flex metal duct fully extnd : 0.01Flex metal duct fully extnd : 0.01Flex wire reinf fabric duct fully extnd : 0.01Flex wire reinf fabric duct fully extnd : 0.01

Ducting & Duct LayoutDucting & Duct Layout

Planning a Single Line Duct LayoutPlanning a Single Line Duct Layout

1.1. Air qty per sq ft Air qty per sq ft

2.2. Air distribution planAir distribution plan

3.3. Ceiling layoutCeiling layout

4.4. Unit LocationUnit Location

5.5. Return Air Return Air

Ducting & Duct LayoutDucting & Duct Layout

Design CriteriaDesign Criteria

1.1. Duct Velocity / Space ApplicationDuct Velocity / Space Application

2.2. Outlet VelocityOutlet Velocity

3.3. Type of Duct / Disc with Architect Type of Duct / Disc with Architect

4.4. If Rectangular then Aspect RatioIf Rectangular then Aspect Ratio ..\Duct Design Tutorial\Aspect Ratio vs Cost.pdf..\Duct Design Tutorial\Aspect Ratio vs Cost.pdf

Ducting & Duct LayoutDucting & Duct Layout

Equal Friction MethodEqual Friction Method

1.1. Applied universally for Duct DesignApplied universally for Duct Design

2.2. Other Methods – Velocity Method & Static Other Methods – Velocity Method & Static Regain MethodRegain Method

3.3. Charts of Friction vs DiameterCharts of Friction vs Diameter

4.4. Equivalent Rectangular SizeEquivalent Rectangular Size

5.5. Use of Ductulator Use of Ductulator

Ducting & Duct LayoutDucting & Duct Layout

Ductulator UseDuctulator Use

1.1. To make single line layout To make single line layout

2.2. Assign the air quantities on the layoutAssign the air quantities on the layout

3.3. Understand the scales of DuctulatorUnderstand the scales of Ductulator

4.4. Selecting correct VelocitySelecting correct Velocity

5.5. Fixing the friction – Select initial duct Fixing the friction – Select initial duct sizesize

..\Duct Design Tutorial\Duct Tutorial pdf.pdf..\Duct Design Tutorial\Duct Tutorial pdf.pdf DUCTSIZE.EXEDUCTSIZE.EXE

Ducting & Duct LayoutDucting & Duct Layout

Plenum Design Plenum Design duct system-modern referigeration.tifduct system-modern referigeration.tif

1. Criteria & Sizing1. Criteria & Sizing

Return Air ConsiderationsReturn Air Considerations

1. Use of RA Ducts / False ceiling / Boxing1. Use of RA Ducts / False ceiling / Boxing

Ducting & Duct LayoutDucting & Duct Layout

GSS Duct StandardsGSS Duct Standards

1.1. IS Standard IS 655IS Standard IS 655

2.2. SMACNA StandardSMACNA Standard

3.3. ISHRAE StandardISHRAE Standard4.4. Commercial Standard Commercial Standard Duct General Standard.xlsDuct General Standard.xls

Ducting & Duct LayoutDucting & Duct Layout

Methods of ConstructionMethods of Construction

1.1. Material of ConstructionMaterial of Construction

2.2. Fabrication methods Fabrication methods

3.3. Supports / BracingSupports / Bracing

4.4. Collar fixing & terminationCollar fixing & termination

Ducting & Duct LayoutDucting & Duct Layout

Types of DuctingTypes of Ducting

1.1. RectangularRectangular

2.2. CircularCircular

3.3. FlexibleFlexible

4.4. Prefabricated Prefabricated

Ducting & Duct LayoutDucting & Duct Layout

Measurements Measurements

1.1. Perimeter & Length measurement Perimeter & Length measurement ..\Sahara ..\Sahara

India Duct Meas.xlsIndia Duct Meas.xls

2.2. Bends & TapersBends & Tapers3.3. Recording measurements gauge-wiseRecording measurements gauge-wise4.4. Joint measurements and presentation Joint measurements and presentation

for billingfor billing

Ducting & Duct LayoutDucting & Duct Layout

Duct AccessoriesDuct Accessoriesduct and system static.pptduct and system static.ppt

1.1. VanesVanes

2.2. DampersDampers

3.3. AttenuatorsAttenuators

Ducting & Duct LayoutDucting & Duct Layout

Working Examples of Duct DesignWorking Examples of Duct Design

1.1. Office Layout Office Layout ..\SAHARA STUDIO.zip..\SAHARA STUDIO.zip

2.2. Factory / LaboratoryFactory / Laboratory

3.3. Large Public Spaces Large Public Spaces 4.4. Under floor duct layout Under floor duct layout ..\Air Distrib\Underfloor.pdf..\Air Distrib\Underfloor.pdf

Ducting & Duct LayoutDucting & Duct Layout

1.1. ConclusionConclusion

2.2. ReviewReview

3.3. Planning for duct fabrication & ErectionPlanning for duct fabrication & Erection

4.4. Site planning & Management for Site planning & Management for ductingducting

5.5. CoordinationCoordination