Seite - 42 - in Adaptive and Intelligent Temperature Control of Microwave Heating Systems with Multiple Sources

3. ModelingMicrowaveHeating Net amount of absorbed powerPab = DissipatedpowerduetoheatconvectionPcv + Dissipatedpowerduetoheat radiationPrd + Dissipated/heatingpowerduetoheat conductionPcd + MicrowaveheatingpowerPmw. (3.1) Each element in the above equation can be calculated as follow- ing. • Netamountofabsorbedpower The net amount of absorbed powerPabwithin this unit cell is rep- resentedby[LNS04] Pab=ρcp dT dt · l3, (3.2) with ρ : massdensity,kg/m3 cp : specificheatperunitmassatconstantpressure,J/(K ·kg) • Dissipatedpowerduetoheatconvection The power flux density of convective heat transfer pcv (W/m2) is givenbyNewton’sLawofcooling[Win99], suchas pcv= −h(T−Ta), (3.3) whereT−Ta is the temperature difference between the load and the surrounding air flow (Ta). The parameterh is the convection heat transfercoefficient (W/ ( m2 ·K)),which isdeterminedbythe geometryoftheload, thevelocityoftheairflow,theangelbetween the surface and air flow and other elements. The negative sign 42