Module 7 - SEB-2013-14

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ADAI Associao para o Desenvolvimento Aerodinmico Industrial

Adlio Rodrigues Gaspar

[email protected]

Francisco Bispo Lamas

[email protected]

Sara Carvalho Francisco

[email protected]

Nilton Janicas Oliveira

[email protected]

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SEBSEB Simulation of Energy in Bui ldingsSimulation of Energy in Buildings

-- A s s o c i a oA s s o c i a o p a r ap a r a oo D e s e n v o l v i m e n t oD e s e n v o l v i m e n t o d ad a A e r o d i n m i c aA e r o d i n m i c a I n d u s t r i a lI n d u s t r i a l

Adlio Rodrigues [email protected]

Francisco Bispo [email protected]

Module 7

Airflow: zone infiltrations

and ventilation

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-- A s s o c i a oA s s o c i a o p a r ap a r a oo D e s e n v o l v i m e n t oD e s e n v o l v i m e n t o d ad a A e r o d i n m i c aA e r o d i n m i c a I n d u s t r i a lI n d u s t r i a l 33

M o d u l e 7 : A i r f l o w : z o n e i n f i l t r a t io n s a n d v e n t i l a t i o nM o d u l e 7 : A i r f l o w : z o n e i n f i l t r a t io n s a n d v e n t i l a t i o n

Airflow

is animportant characteristicof energy consumption in buildings:

airflow between zones;

and airflow due to natural ventilation;

mechanical ventilation.

Airflow: standard parameterization of infiltrations and ventilation.

Airflow Network:advanced modeling of airflows driven by wind and a forced

air distribution system.

Airflow

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Building energy breakdown of an office building Airflow

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Zone Infiltration

Infiltration is the unintended flow of air from the outdoor environment directly into a

thermal zone.

Caused by:

the opening and closing of exterior doors;

cracks around windows;

very small amounts through building elements.

Different methods:

Design Flow Rate

Effective Leakage Area

Flow Coefficient

Airflow

for smaller,

residential-type

buildings

)()())(( 2WSDWSCTTBAFIonInfiltratiodbzonescheduledesign

2)(1000

)( WSCTCA

FonInfiltrati WSLschedule

222 )()( nW

n

Sschedule WSscCTcCFonInfiltrati

Eq. for design flow rate method:

Eq. for effective leakage area:

Eq. for flow coefficient:

WS: wind speed

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Design Flow Rate

Values for thecoefficients:

chapter 26 of theASHRAE Handbook of Fundamentals.

the EnergyPlus defaults: 1,0,0,0 which give a constant volume flow of infiltration

under all conditions.

the BLAST defaults: 0.606, 0.03636, 0.1177, 0.

The DOE-2 defaults (adjusted to SI units):0, 0, 0.224, 0.

Airflow Zone Infiltration

)()())(( 2

WSDWSCTTBAFIonInfiltrati odbzonescheduledesign

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Design Flow Rate

ZoneorZoneList Name:

to link a Zoneor ZoneList;

ZoneList can be used with the flow/area, flow/exteriorarea, flow/exteriorwallarea, or

airchanges/hour of the Design Flow Rate Calculation Method.

Schedule Name: The name of the schedule thatmodifies the maximum design volume

flow rate(Idesign). This fraction between 0.0 and 1.0 is noted asFschedule in the above

equation.

Design Flow Rate Calculation Method:

flow/area; flow/exterior area;

flow/exterior wall area;

air-changes/hour


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Design Flow Rate

Design Flow Rate (m3/s):denotes the full design volume flow rate. The design

volume flow rate (noted as Idesign in the above equation) is the maximum

amount of infiltration expectedat design conditions.

Flow per Zone Floor Area and Flow per Exterior Surface Area (m3/s-m2):used,

along with the Zone Area or Exterior Surface Area to determine the maximum

Design Flow Rate.

Air Changes per Hour: used, along with the Zone Volume to determine the

maximum Design Flow Rate.


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-- A s s o c i a oA s s o c i a o p a r ap a r a oo D e s e n v o l v i m e n t oD e s e n v o l v i m e n t o d ad a A e r o d i n m i c aA e r o d i n m i c a I n d u s t r i a lI n d u s t r i a l 1 01 0


Design Flow Rate

Constant Term Coefficient (A):function of environmental factors. This parameter, however, is a

constant under all conditionsand is not modified by any environmental effect. As a result, it is

dimensionless.

Temperature Term Coefficient (B):function ofenvironmental factors. This parameter ismodified by

the temperature difference between the outdoor and indoor air dry-bulb temperatures. The units

for this parameter are inverse Celsius.

Velocity Term Coefficient (C):function ofenvironmental factors.This parameter ismodified by the

speed of windbeing experienced outside the building. The units for this parameter are s/m.

Velocity Squared Term Coefficient (D): function of environmental factors. This parameter is

modified by square of the speed of windbeing experienced outside the building. The units for this

parameter are s2/m2.


)()())(( 2WSDWSCTTBAFIonInfiltratiodbzonescheduledesign

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For smaller, residential-type buildings

Effective Leakage Area 1

Flow Coefficient 2

T is the average difference between zone air temperature and the outdoor air

temperature

1 Developed by Sherman and Grimsrud (1980)

2 Based on AIM-2 model by Walker and Wilson (1998)


2)(

1000)( WSCTCA

FonInfiltratiWS

L

schedule

222

)()( n

W

n

Sschedule WSscCTcCFonInfiltrati

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Effective Air Leakage Area (AL) (cm2, at 4 Pa):can be obtained from a whole-

building pressure test (eg. blower door test) or ASHRAE Handbook of

Fundamentals. The value should correspond to a pressure difference of 4 Pa.

Stack Coefficient 1 (CS) - (L/s)2/(cm4K)

1Tipical values listed in the ASHRAE Handbook of Fundamentals (2005 and 2001)


2)(1000

)( WSCTCAFonInfiltrati WSLschedule

One story house 0.00014

Two story house 0.000290

Three story house 0.000435

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1Tipical values listed in the ASHRAE Handbook of Fundamentals (2005 chapter 27; 2001, Chapter 26)


Shelter class Description1 No obstructions or local shielding

2 Typical shelter for an isolated rural house

3 Typical shelter caused by other buildings across the street

4 Typical shelter for urban buildings on larger lots

5 Typical shelter produced by buildings that are immediately adjacent

Shelter

class

One story

house

Two story

house

Three story

house

1 0.000319 0.000420 0.000494

2 0.000246 0.000325 0.000382

3 0.000174 0.000231 0.000271

4 0.000104 0.000137 0.000161

5 0.000032 0.000042 0.000049

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Flow Coefficient

Note:the coefficients for the Flow Coefficient model are not interchangeable with the similarly named coefficients in the Effective

Leakage Area model

Flow Coefficient (c) (m3/(sPan)):can bedetermined from the effective leakage area

andwhole-building pressure test(eg. blower door test).

Stack Coefficient1 (CS) - (Pa/K)n

Pressure Exponent (n):generally lies between 0.6 and 0.7 with a typical value of n = 0.67

for the enhanced model

1Tipical values listed in the ASHRAE Handbook of Fundamentals (2005 and 2001)


222 )()( nW

n

Sschedule

WSscCTcCFonInfiltrati

With flue No Flue

One story house 0.069 0.054

Two story house 0.089 0.078

Three story house 0.107 0.098

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Wind Coefficient 1 (CW) ((Pa.s)2/m2)n

Shelter Factor 1 (s)

1Tipical values listed in the ASHRAE Handbook of Fundamentals (2005 chapter 27; 2001, Chapter 26)2See effective Leakage Area model


One story house Two story house Three story house

Basement/slab; With Flue 0.142 0.156 0.167

Basement/slab; No Flue 0.156 0.170 0.170

Crawlspace; With Flue 0.128 0.142 0.154

Crawlspace; No Flue 0.128 0.142 0.151

Basement/slab; With Flue 0.142 0.156 0.167

Shelter class 2 No Flue One story house Two story house Three story house

1 1.00 1.10 1.07 1.06

2 0.90 1.02 0.98 0.97

3 0.70 0.86 0.81 0.79

4 0.50 0.70 0.64 0.61

5 0.30 0.54 0.47 0.43

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Portuguese regulation for residential

buildings

Region A - Generality of the territory, except

Region B

Region B - Azores, Madeira and locations at 5

km along the coast and / or altitude above

600m


Hight above

Ground

Region A Region B

I II III I II III

10 m Exp 1 Exp 2 Exp 3 Exp 1 Exp 2 Exp 3

>10 m and 18 m Exp 1 Exp 2 Exp 3 Exp 2 Exp 3 Exp 3



Roughness I Roughness II Roughness III

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Portuguese regulation for residential buildings

Openings not self-regulating: RPH + 0.10

Glazing area > 15% of floor area: RPH + 0.10

Sealed doors: RPH - 0.05 (but always 0.60).

Class ofExposition

Air permeability of frames (according EN12207)

Without

Classification

Blind box

Class 1

Blind box

Class 2

Blind box

Class 3

Blind boxNP1037-1

Yes No Yes No Yes No Yes No

0.6

1Yes 0,90 0,80 0,85 0,75 0,80 0,70 0,75 0,65

No 1,00 0,90 0,95 0,85 0,90 0,80 0,85 0,75

2Yes 0,95 0,85 0,90 0,80 0,85 0,75 0,80 0,70

No 1,05 0,95 1,00 0,90 0,95 0,85 0,90 0,80

3Yes 1,00 0,90 0,95 0,85 0,90 0,80 0,85 0,75

No 1,10 1,00 1,05 0,95 1,00 0,90 0,95 0,85

4Yes 1,05 0,95 1,00 0,90 0,95 0,85 0,90 0,80

No 1,15 1,05 1,10 1,00 1,05 0,95 1,00 0,90

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Ventilation

is thepurposeful flow of airfrom the outdoor environment directly into a thermal zone

in order toprovide:

some amount ofnon-mechanical cooling;

the needed fresh air for IAQ requirements.

Can becontrolled by a scheduleand through thespecification of minimum, maximum

and delta temperatures. The temperatures can be either single constant values for the

entire simulation or schedules which can vary over time.

For more advancedventilation calculations useEnergyPlus Airflow Network.

Airflow Ventilation

)()())(( 2WSDWSCTTBAFVnVentilatioodbzonescheduledesign

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Design Flow Rate Calculation Method

flow/zone; flow/area; flow/person; airchanges/hour

Design Flow Rate (m3/s):denotes the full design volume flow rate. The design volume flow rate

(noted as Vdesignin the above equation) is the maximum amount of ventilation expectedat design

conditions.

m3/(h.person) m3/(h.m2)

Airflow Ventilation

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Ventilation Type

Natural

Air movement/exchange result ofopenings in the building

faade;

Do notconsumes fan energy;

Theconditions of the air enteringthe space are assumed to beequivalent to outside air

conditions;

Values forfan pressure and efficiency for natural ventilation are ignored.

Airflow Ventilation

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Ventilation Type (cont.)

Exhaust or Intake

Values for fan pressure and efficiency define thefan electric consumption;

For exhaust ventilation: the conditions of the air entering the space are assumed to be

equivalent to outside air conditions;

For intake ventilation: an appropriate amount offan heat is added to the entering air

stream.

Pfan - fan pressure rise (Pa);

Qfan -fan flow at std conditions (m3/s);

Hfan - fan shaft power (W).

Airflow Ventilation

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Ventilation Type (cont.)

Balanced

An appropriate amount of fan heat is added to the entering air stream;

Both an intake fan and an exhaust fan are assumed to co-exist, both having the same flow

rate and power consumption.

Fan Pressure Rise - Pascals (N/m2): this is a function of

the fan and plays a role in determining the amount of

energy consumed by the fan.

Fan Total Efficiency (0.0 1.0): this is a function of

the fan and plays a role in determining the amount of

energy consumed by the fan.

Airflow Ventilation

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Minimum Indoor Temperature (-100.0 to 100.0C): indoor temperature

(C)belowwhichventilation is shutoff. The default valueis -100.0Cif the field is left blank.

This lower temperature limit is intended to avoid overcooling a space.

Minimum Indoor Temperature Schedule Name:defines the name of a schedule which contains

the minimum indoor temperature (C) below which ventilation is shutoff as a function of time.

This field is an optional field and has the same functionality as the Minimum Indoor

Temperaturefield.

Maximum Indoor Temperature (-100.0 to 100.0 C): indoor temperature (C)abovewhich

ventilation is shutoff. The default value is 100.0C if the field is left blank. This upper

temperature limit is intended to avoid overheating a space.

Maximum Indoor Temperature Schedule Name: defines the name of a schedule whichcontains the minimum indoor temperature (C) below which ventilation is shutoff as a function

of time. This field is an optional field and has the same functionality as the Maximum Indoor

Temperaturefield.

Airflow Ventilation

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Maximum Outdoor Temperature (-100.0 100.0 C): outdoor

temperature(C)abovewhich ventilationis shutoff.

Maximum Outdoor Temperature Schedule Name:This field is an optional field and has

the same functionality as the Maximum Outdoor Temperature field.

Maximum Wind Speed (m/s):This field is the wind speedabovewhich ventilation isshut

off. Thiscan help simulateconditions where one would normallyclose windows to avoid

chaosin a space (papers blowing around, etc.).

Airflow Ventilation

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Other options:

WindandStackOpenArea: For this model, the

ventilation air flow rate is a function of wind speed and

thermal stack effect, along with the area of the openingbeing modeled.

ZoneAirBalance:OutdoorAir: This model calculates a

combined zone outdoor airflow by including

interactions between mechanical ventilation,

infiltration and duct leakage. It is mainly applied to a

single zone (e.g., residential) building. The modelcombines all outdoor airflows from ZoneInfiltration and

ZoneVentilation objects in the same zone.

ZoneMixing: In EnergyPlus, the ZoneMixing syntax is

intended to allow simplified treatment of air exchange

between zones. Note that this statement only affects

the energy balance of the receiving zone and that thisstatement will not produce any effect on the source

zone. Mixing statements can be complementary and

include multiple zones, but the balancing of flows

between zones is left to the users discretion.

ZoneCrossMixing: The ZoneCrossMixing syntax is

ideally suited for two zones that exchange an equalamount of air between each other and do not have any

air exchange with other zones.

ZoneRefrigerationDoorMixing: The ZoneRefrigeration

DoorMixing syntax is ideally suited for two zones, at

least one of which is refrigerated, that exchange an

equal amount of dry air. They may also have mixed airfrom other zones, but only one object should be

entered for any one pair of zones.

CalcSoilSurfTemp Auxiliary Programs Document: The

CalcSoilSurfTemp program is simple and requires only

two input fields : soil condition and soil surface

condition in addition to a valid weather file.ZoneCoolTower:Shower

ZoneThermalChimney

Airflow Ventilation

Module 7 - SEB-2013-14

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