PHYSIBEL

simulation of transient heat transferin 2D free-form objects

Introduction

The Physibel program BISTRA allows simulations of transient heat transfer in 2D free-form objects.This slide show highlights

• how to solve a 2D transient problem using BISTRA (with RADCON option)

• useful application examples- ground heat losses and frost insulation- fire engineering – steel-concrete floor- fire engineering – window frame- harmonic analysis of walls- temperature of heated & unheated rooms- thermal effect of solar radiation on façades

Solving a 2D transient heat transfer problem using BISTRA

1. Problem definition The analysis of a fictitious problem shows the powerful performances of BISTRA.

Solving a 2D transient heat transfer problem using BISTRA

1. Problem definition Materials with non-linear thermal properties, phase change materials (PCM) and an argon filled gas layer bounded by a low emissivity surface occur.

Solving a 2D transient heat transfer problem using BISTRA

1. Problem definition The water temperature in the tubes rises and a heat is released at the PCM border. Non-linear convection and radiation occur.

Solving a 2D transient heat transfer problem using BISTRA

2. Problem implementation: BISTRA program interface > windows

bitmap

colours

measures

borderline bc’s

functions

2. BISTRA program interface bitmap window

automatic filling of line drawing

each colour corresponds to a material or to a boundary condition

drawing and fill tools available for modifying the bitmap as in BISCO

2. BISTRA program interface colours windowcolour used in bitmap

material – boundary condition type

specific standard rule, for example used to calculate the equivalent thermal conductivity

thermal conductivity

constant or temperature dependentfunction

surface IR emissivity

density

specific heat

constant or temperature dependentfunction

temperature (global, air, radiant)

constant or time function

global or convective surface coefficientheat source

standard rule coefficientsconstant or time function

2. BISTRA program interface functions window

parameter or file defined functions

function graph view

2. BISTRA program interface measures window

0.5 m

size for automatic triangulation

2. BISTRA program interface calculation parameters

start-up calculation duration allows transient start condition

multiple iteration cycles for non-linear problems

both linear and non-linear radiation model with automatic view factor calculation

recalculation of temperature dependent quantities at each time step

3. BISTRA calculation results graphic output window

3. BISTRA calculation results graphic output window

3. BISTRA calculation results graphic output window

3. BISTRA calculation results graphic output window

3. BISTRA calculation results animation output

BISTRA allows transient thermal simulations according to

EN ISO 13370Thermal performance of buildings - Heat transfer via the ground - Calculation methods

EN ISO 13793Thermal performance of buildings - Thermal design of foundations to avoid frost heave

BISTRA application example 1ground heat losses and frost insulation

BISTRA application example 2fire engineering – steel-concrete floor

BISTRA allows fire engineering simulations according to the

EUROCODES for structural calculations.

A fire curve (typically ISO 834) is assumed at one side of the construction.

The simulation of the heat transfer by radiation, convection and conduction

allows predicting the temperature evolution in the construction.

Temperature dependent material properties (steel, concrete, ...) are

considered.

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BISTRA application example 3fire engineering – window frame

BISTRA application example 4harmonic analysis of walls

BISTRA application example 5temperature of heated & unheated rooms

BISTRA application example 6thermal effect of solar radiation on façades

For a south façade (double glazing, aluminium frame, opaque insulation panel) in Brussels the temperature distribution is calculated, taking into account the solar radiation transmitted through the glazing and absorbed in the façade.

… about 3D …

The Physibel program VOLTRA allows simulations of transient heat transfer in 3D objects described with rectangular blocks.VOLTRA has the same basic simulation performances as BISTRA.BISTRA data can be imported ! The bitmap pixels are treated as small rectangular blocks.

Further information can be found on: http://www.physibel.be/v0n2vo.htm

PHYSIBEL

Heirweg 21 B-9990 Maldegem Belgiumphone +32 50 711432 fax +32 50 717842www.physibel.be mail@physibel.be

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