# simulation of transient heat transfer in 2D free-form objects

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simulation of transient heat transfer in 2D free-form objects
PHYSIBEL

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
each colour corresponds to a material or to a boundary condition automatic filling of line drawing drawing and fill tools available for modifying the bitmap as in BISCO

2. BISTRA program interface colours window
colour used in bitmap material – boundary condition type specific standard rule, for example used to calculate the equivalent thermal conductivity thermal conductivity surface IR emissivity temperature (global, air, radiant) constant or temperature dependent function density constant or time function specific heat constant or temperature dependent function heat source global or convective surface coefficient standard rule coefficients constant or time function

parameter or file defined functions
2. BISTRA program interface functions window function graph view parameter or file defined functions

size for automatic triangulation
2. BISTRA program interface measures window 0.5 m size for automatic triangulation

calculation parameters
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 application example 1 ground heat losses and frost insulation
BISTRA allows transient thermal simulations according to EN ISO Thermal performance of buildings - Heat transfer via the ground - Calculation methods EN ISO Thermal performance of buildings - Thermal design of foundations to avoid frost heave

BISTRA application example 2 fire 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 3 fire engineering – window frame

BISTRA application example 4 harmonic analysis of walls

BISTRA application example 5 temperature of heated & unheated rooms

BISTRA application example 6 thermal 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:

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