designbuilder simulation training_hsd

8/12/2019 DesignBuilder Simulation Training_HSD

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Tr inin


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Natural VentilationDriven by

uoyancy ec

Wind

na ys s oo s

Airflow Network models Fi ure Source: J Good et al, SimBuild 2008

Computational Fluid Dynamic (CFD)

n unne stu y measurement


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Airflow Network Model Developed by NIST (Walton 1989)

oup e o

Bulk airflow movement, avera e tem eratures

Nodes connected by air flow elements

n ressure oe c ent p va ues nee to

be defined Input/Auto


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Airflow Network Model..contdCp determination

epen s on u s ape, w n rec on, near y

buildings, vegetation, terrain etc.

Can be only obtained from Wind tunnel test

ASHREA handbook of fundamentals Restricted to low rise rectangular buildings

=2

w . . . p. z


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Airflow Network Model..contd

CP Values : Source: ASHRAE handbook of

fundamentals, 2005 pp 16.5


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AIRNET Model.. contd

Plan view of a simple airflow network showing a possible airflow pattern

Source: Lixing Gu , roceedings: Building Simulation 2007


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2 Modes

DesignBuilder offers 2 Nat vent modes: Scheduled


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Scheduled Nat Vent

Infiltration is constant.

Interior airflow through mixing

Avoidance of heating


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Basic Scheduled natural ventilation model

Controlled Natural ventilation

Infiltration


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Same as first but with Internal Airflow

Check change in results


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Calculated Natural ventilation:

Set window opening % + schedule

Infiltration


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Tutorial 4As previous but with variations:

,

Wind effects

Internal vent airflow


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analytical procedure to predict the flow of

u s a r, wa er e c.

Develo ed for the aerod namics industr as a

faster alternative to wind tunnel testing

temperature, velocity, direction of flow,pressure an energy momentum o a u

particle in the solution domain


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Focus: Incompressible fluids

Continuity and Momentum Equations


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Methods based on the vorticity equation

Methods that use pressure iterations or

pressure correct on. Fract ona - StepMethods SIMPLE SIMPLERSIMPLEST, PISO etc.)

Semi Implicit Method for Pressure Linked Equation Revised


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What can we use CFD for?Architectural Applications

Airflow in and around buildings

onvect ve an ra at on eat trans er amongbuilding components effectiveness of radiant

eat ng an coo ng systems.

Natural Ventilation Design Displacement Ventilation design


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DesignBuilder CFD

Distribution of air temperature, velocity etc Internal and External Analyses

Calculations

Boundary conditions


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reate a ra ator component

Convert the component to an assembly Assign CFD boundary conditions to the assembly

Add assembly to the assembly library.

Place radiator assembly x 2 E i FD ri

Add cell monitor points

.

Comfort calculations.


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Create model for external analysis.

Perform the CFD calculation

Review the results

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