Encyclopaedia Index

### TITLE : Convection affected by radiation

BY : Dr S V Zhubrin, CHAM Ltd

DATE : November, 2000

FOR : Demonstration case for V3.3.3

### INTRODUCTION

An IMMERSOL application is presented aimed at the demonstration of the method for the radiation-affected buoyancy-induced convection in a rectangular enclosure with thick conductive walls.

### THE STATEMENT OF THE PROBLEM

This case deals with conjugate heat transfer in the free-convected flow of participating gas arising in a rectangular cavity the thick walls of which are made from aluminium with an emmitance of 0.9.

The outer surfaces of the bottom and top walls are supposed to be well insulated. The temperatures of side walls are different: one has 300K at the outer surface, another is fixed at 600K.

The task is to compare the velocity and temperature distributions for the different absorptive and scattering properties of the gas.

### Conservation equations

The independent variables of the problem are the two components of cartesian coordinate system, namely X and Y.

The main dependent (solved for) variables are:

• Pressure, P1
• Two velocity components, U1 and V1
• Temperature of the medium, TEM1 and

### Buoyancy model

The Boussinesq approximation is ised to incorporate the temperature dependence of the density.

The IMMERSOL model is used to simulate the distribution of T3 and TEM1 within the space filled with transparent air. From the temperature fields the radiant heat fluxes, QRX and QRY, W/m^2, are calculated and used as the heat sources in iterative manner.

### Properties and auxiliary relations

The gas physical properties are taken constant as for air at 20C with the constant uniform values of absorption and scattering coefficients being subject to parametric changes.

### THE RESULTS

The plots show the distribution of velocity, temperature and X-, Y-direction radiant heat fluxes within the enclosure.

Pictures are as follows :

### THE IMPLEMENTATION

All model settings have been made in VR-Editor of PHOENICS 3.3.3.

The relevant Q1 file can be inspected by clicking here.