Power Dissipation Within the Ceramic

It is often required to estimate the amount of power that can be safely dissipated in a ceramic given that the effective loss factor is known. This can be obtained from considering the Poynting vector x H which leads to the 

The electric field is given by equation 20. In microwave heating the electric field is assumed not to decay too fast within the material, therefore it is usual to make the following approximation  

Substituting equation 23 into equation 22 yields the power per unit volume developed in the ceramic dielectric  

It is fairly evident that in a material which exhibits the same dielectric properties at say, 900 MHz and at 2450 MHz, the electric field at the lower frequency has to be much higher in order to develop similar power densities at the two frequencies. For example, for a power dissipation of 10 MWm and e = 0.1 the required electric fields at 900 MHz and at 2450 MHz are 44.5 kVm and 27 kVm respectively. 

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Having described the electrical paraneters which control the current density and power dissipation within the ceramic material and having outlined various applicator structures, attention is now switched to the equation which controls the heat transfer. In the present context it will suffice to quote the following continuity equations for heat ... 

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