Heat balance with volumetric heat generation (source code)

= Heat balance with volumetric heat generation
{title2=$c_{\rm vol}T_t=\nabla\cdot(k\nabla T)+H$}

Integrating <energy> conservation over a fixed material volume gives storage equal to incoming conductive <heat flux> plus internally generated <heat>. Here $c_{\rm vol}$ is <volumetric heat capacity>, with units $\mathrm{J\,m^{-3}\,K^{-1}}$. For a mass-specific <heat capacity>, the <density> factor must be included. Constant isotropic conductivity reduces the divergence to $k\nabla^2T$; variable conductivity must remain inside the divergence.