MATLAB: How to apply external heat flux to a surface with specified “emissivity” boundary conditions in MATLAB R2018 PDE Toolbox

bcemissivityheatfluxMATLABpde

I am modelling thermal behaviour of lunar surface, thus it is necessary to specify both heat flux from incident solar radiation and thermal radiation of the lunar surface.

Unfortunately, one of these is ignored, when declared as follows:

thermalBC(thermalmodelT,'Edge',2,'HeatFlux',@SolRad_hf);

thermalmodelT.StefanBoltzmannConstant = 5.670373E-8;

thermalBC(thermalmodelT,'edge',2,'Emissivity',0.98,'AmbientTemperature',3);

Best Answer

You can specify all heat fluxes on that BC with a single function call, like:

thermalBC(thermalmodelT,'Edge',2,'HeatFlux',@SolRad_hf,'Emissivity',0.98,'AmbientTemperature',3);

Regards,

Ravi

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MATLAB: Unexpected Result for 3-D Thermal Transient Analysis of Heat sink using PDE Solver Toolbox

Here is the correct results using the new STL after fixing two more inconsitencies:

Radiation problem should include temperature in K.
All BCs on a particular set of faces need to be applied at once, otherwise the following assignment would overwrite the preceeding one if they are applied on the same set of faces.

code:

%% Model Setup for Heat Sink
thermalmodel = createpde('thermal','transient');
gm = importGeometry(thermalmodel,'heatsinkv2.stl'); 
pdegplot(thermalmodel,'FaceLabel','on','FaceAlpha',0.5);
axis equal
%% mesh
generateMesh(thermalmodel);
figure;
pdeplot3D(thermalmodel);
%% Boundary Condition,  Aluminium Alloy Properties and Initial Conditions
TCval = @(location,state)139.3 + 0.204*(state.u-273.15); %sets thermal conductivity (W/m/°C) as a function of temperature only approximate equation based on linear trend for table data from ansys engineering alumnium alloy data
MDval = 2770; %density kg/m^3
SHval = 875;  %specific heat (J/kg/°C)
ATval = 25+273.15;   %ambient temperature
CCval = 30;   %convective film coefficient W/m^2
REval = 0.77; %radiation emissivity
thermalmodel.StefanBoltzmannConstant = 5.670373E-8;
faces = [1,3:30];
thermalProperties(thermalmodel,'ThermalConductivity',TCval,'MassDensity',MDval,'SpecificHeat',SHval);
thermalBC(thermalmodel,'Face',faces,'ConvectionCoefficient',@(region,state)CCval,'Emissivity',@(region,state)REval,'AmbientTemperature',ATval);
thermalBC(thermalmodel,'Face',2,'ConvectionCoefficient',5,'Emissivity',0.1,'AmbientTemperature',ATval);
thermalIC(thermalmodel,60+273.15); %sets initial temperature °C problem with this as temp doesnt go down very fast?
%% solve
tlist= [0:10]; %time from 0 to 10seconds
thermalTransientResults = solve(thermalmodel,tlist);
pdeplot3D(thermalmodel,'ColorMapData',thermalTransientResults.Temperature(:,10)-273.15)