overview applied computer modeling for building engineering z · 2005. 2. 2. · © john straube...
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© John Straube 2005
Applied Computer Modeling Applied Computer Modeling for Building Engineering for Building Engineering
Dr John F. StraubeDr John F. StraubeDupontDupont Young ProfessorYoung Professor
Dept of Civil Engineering & School of ArchitectureDept of Civil Engineering & School of Architecture
University of WaterlooUniversity of WaterlooOntario, CanadaOntario, Canada
[email protected]@uwaterloo.ca519 888 4015519 888 4015
© John Straube 2005
OverviewOverview
Why Modeling?Heat Flow• Therm / Frame• Heat 2D / Heat 3D • Case studies
Heat & Moisture• WUFI-ORNL & Validation• Case studies
Fire Energy and LightingSummary
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ActivityActivity
Sun
EnergyEnergy
ResourcesResourcesPollutantsPollutants
The Building The Building EnclosureEnclosure
EnergyEnergyResourcesResources
PollutantsPollutantsWasteWaste
Pollutants, Waste, EnergyPollutants, Waste, Energy
HVAC
Pollutants: Moisture, odour, + +
The Building SystemThe Building System
© John Straube 2005
Modeling for fun and profitModeling for fun and profit
Predict and understand temperature and moisture condition in & on bldg enclosureAvoid design errorsUnderstand problemsAid the design of repairsDevelopment of new systems/productsDevelop understanding of performance (teach)
© John Straube 2005
What are What are ““ModelsModels””
By definition, an approximation of realityTypically a model is designed for a particular purpose,• e.g. calculate energy
As simple as• Q= U •∆T → Q(t) = U •∆T(t)
As complex as full building dynamic simulation including occupant behaviour, plant, controls, etc.
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What and for Whom?What and for Whom?
What
Who
Hygrothermal Analysis
AssessmentDesign Study
· New· Conversion· Upgrade
· Condition Survey· Forensic· Conversion
R & D· products· codes· fundamentals
Teaching· colleges· university· professional
Who Engineers, Architects, Code officials Trainers, scientists
This presentation deals with design & analysis uses
© John Straube 2005
Structural EngineeringStructural Engineering
Physics:Statics, MODS
Math
Material Properties
Loads
Idealized Model
Design Process
Performance Thresholds
Structural Analysis
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““Building ScienceBuilding Science”” EngineeringEngineering
Physics:Material science, Thermodynamics
Mathematics
Material Properties
Design Process
H.A.M. Analysis
Environmental Loads
Idealized Model
Performance Thresholds
© John Straube 2005
Action
PerformanceThresholds
Building the Building the ““ModelModel””
MaterialProperties
PhysicsNumerical Methods
Topology
Results
Boundary Conditions
Surface Transfer
Prob
lem
/ N
eed
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The ProcessThe Process
10
Need ProblemDefinition Interpret
Physics
NumericsBoundaryConditions
Topology
MaterialProperties
Iterate as necessary
Decision and Action
© John Straube 2005
RequirementsRequirements
Vary with Need, Time available, expertise
Geometry (topology)Boundary Conditions (operating conditions)Material PropertiesPhysicsPerformance Thresholds
© John Straube 2005
What to ModelWhat to ModelHeat• Flow (Energy)• Temperatures
Air• Energy• Contaminant transport
Moisture• Durability, mold
LightFire
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© John Straube 2005
Heat FlowHeat Flow
Steady-state or Dynamic• steady-state -- for average conditions or for
lightweight construction• Dynamic -- to assess thermal mass, transient
conditions
One- Two- or Three-dimensionalFree Tools• Use Therm or Frame
Both 2-D steady-state
© John Straube 2005
Thermal BridgingThermal Bridging
Why calculate? •Heat Loss calculations• Surface Condensation
–dust marking– mould–windows
• Interstitial Condensation
2-D steady state is easy2-D dynamic acceptable3-D is time consuming
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© John Straube 2005
Wall Temperatures and RHWall Temperatures and RH
Temperature Temperature ProfileProfile
tt
Temperature (C)
VapourVapourPressure Pressure
ororAir Air
moisture moisture contentcontent
1010 252520201515
∆∆tt
∆∆tt
RH=100%RH=100%
RH=80%RH=80%
RH=50%RH=50%
Poor insulation = cold surface = high RH
© John Straube 2005
Interior Air at 22 CInterior Air at 22 CSurface temperatures cannot be less than:Surface temperatures cannot be less than:
Interior RH CondensationTemperature
2020 --22 114040 88 11115050 1111 14146060 1414 17178080 1818 2222
Temperature @80%RH
© John Straube 2005
TwoTwo--D SteadyD Steady--statestate
Frame (www.enermodal.com)Therm (windows.lbl.gov/software/therm)• Free, downloadable• Can use AutoCad templates• Primary intent -- window energy calculations• Can do much more
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Interior Air: 21.5 C
Windows are usually coldest
© John Straube 2005
Example of a wooden window - meshing
© John Straube 2005
Example of a wooden window - contours, etc
© John Straube 2005
Example of a wooden window -“Infra-Red scan”
© John Straube 2005
Steel FramingSteel Framing
Metal Building Systems and Steel StudsCan be Thermal Bridges• Consume Energy • cause dust marking• Surface condensation
How much/little insulation is needed?
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© John Straube 2005
InfraInfra--Red PhotosRed Photos
14.0
22.0 °C
14
16
18
20
22
14
15
16
17
18
19
20
21
22
From inside a building at 22 C
© John Straube 2005
Mixing ModelsMixing Models
One model or modeling approache.g.Temperature flow, combined with dewpoint“suite of models”• range of complexity/accuracy• range of expertise required
Case Study Major manufacturing plant• High interior humidity for film production
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© John Straube 2005
Metal Building SystemOut:Cool
In:WarmHumid
© John Straube 2005
Mesh
© John Straube 2005
-10.0 -5.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0
Temperature ( °C)
0
500
1000
1500
2000
2500
3000
3500
4000
Vap
our
Pre
ssure
(Pa
)
100% RH75% RH50% RH25% RH
Psych Chart: Air Vapour Content vs Temperature
Saturation
50%
RH
25%RH
75%
RH
100%
RH
100%RH
Temperature
Air
Moi
stur
e C
onte
nt
= va
pour
pres
sure
(Pa,
in H
g),
hum
idity
rat
io (g
/kg,
gra
ins/
pd)
-10 ºC14 º F
0 ºC32 º F
10 ºC50 º F
20 ºC68 º F
30 ºC86 º F
40 ºC104º F © John Straube 2005
SurfaceCondensation
InterstitialCondensation
© John Straube 2005
Case StudyCase Study-- Rec. ComplexRec. ComplexMetal building systemCondensation and Dripping?
© John Straube 2005
Add ¾” insulation blockZero riskNow – other building details
© John Straube 2005
TwoTwo--Dimensional DynamicDimensional Dynamic
Thermally Massive Systems• Energy• Surface condensation
Blocon - Heat2 v4.0 (USD320 www.blocon.se)Physibel- Sectra (www.physiblel.be)
© John Straube 2005
Case Study: SubCase Study: Sub--slab insulation slab insulation below Radiant Heatingbelow Radiant Heating
Question: Does the use of radiant floor heating change the normal rules of thumb regarding sub-slab insulation?Approach: Dynamic 2- Heat flow model
2.1 m below grade At grade
Grade
Grade
4 m tocenter
4 m tocenter
© John Straube 2005
Case studyCase study
Uses Heat2 range of soil types and conductivity Apply heat in each tubeControl upward flux to be the same in both
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Boundary ConditionsBoundary Conditions
High thermal lag allows large time steps to be practicalCreated synthetic but representative “climate” file
© John Straube 2005
Radiant Floor Heat InputRadiant Floor Heat Input
Based radiant tubes heat output on weekly average outdoor temperature to balance conductive/air leakage losses
© John Straube 2005
Material PropertiesMaterial Properties
Soil properties are both poorly known andimportant to the resultsHence – parametric studySoil Description Conductivity Heat Capacity
(W/mK) (MJ/m3 K)
Dry Sandy Loam 0.70 1.50
Moist Clay 1.50 1.65
Wet Sand 2.30 1.80
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© John Straube 2005
Heat2Mesh
© John Straube 2005
Materials andProperties
© John Straube 2005Uninsulated Slab FebruaryUninsulated Slab February
Heating power kept the same
ResultsResults
© John Straube 2005Insulated Slab FebruaryInsulated Slab February
Note individual pipes
© John Straube 2005
Heat loss comparedHeat loss compared
Savings: 28.2 kWh/m2/yr
© John Straube 2005
ThreeThree--Dimensional Heat FlowDimensional Heat Flow
Steady-state: systems with complex shapes• point thermal bridges, ties, connections
Dynamic: thermally massive complex • as above but thermal mass, fires, foundations
Rarely require this detail -- easier to be cleverCommercial Tools• Physibel Voltra (dynamic) Trisco (static)• Blocon Heat3 (both USD520)• Heat 7.2 (ORNL - not really commercial)
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© John Straube 2005
TriscoTrisco --3D steady state3D steady state
© John Straube 2005
Voltra FoundationWinter Conditions
© John Straube 2005
Boundary Conditions and Annual Temp variations
Note Node 1 and Node 2
© John Straube 2005