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dgd December 11, 2003 18:53

Convection + Radiation BC
Could anyone advise how to add both the convective heat loss (linear heat bc) and the radiative heat loss to the same region?

mike July 14, 2004 09:09

Re: Convection + Radiation BC
Hello, just set two separate patch/covals for the same region as the sources are additive and hence the heat loss will be a net one.

I think these patches will need area multipliers, but you can check by looking at examples from the PHOENICS literature or working out units. Sources to the heat equations are in units Watts.

the heat transfer loss Q is : Q=htc(Tw-Tphi); where Tw=temp of wall or temp outside the domain. and htc is the heat transfer coefficient.

So in Phoenics for the coval Co=htc and Val =Tw

Radiative heat loss will be of the form Qrad= sigma Eps(Tw^4 -T^phi). Where sigma Eps are stefhan boltzman and emmisivity or something like this. In Phoenics there is a special patch to add radiative heat loss. Alternatively you will have to express Qrad in terms of Co(Val-Phi).

There will be plenty of examples of how to do this.

But to summarise two separate patch/covals are ok for the same region the net heat loss will be a combined one.

AMBER April 28, 2005 11:30

Re: Convection + Radiation BC

i dunno?? February 19, 2006 17:28

Re: Convection + Radiation BC
u r well confusing me plz someone help me wiv ma science stuc in ahole....*cries really bady* aww well im gonna get a e that will be cos of ma pathtic looser gonna kill every1 argh!!! going mad....stupid bloody coursework....arrhg!!!

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