June 2026

To derive the heat conduction equation in spherical coordinates$(r, \theta, \phi)$ from Cartesian coordinates, we transform the Laplacian operator$\nabla^2 T = \frac{\partial^2 T}{\partial x^2} + \frac{\partial^2 T}{\partial y^2} + \frac{\partial^2 T}{\partial z^2}$. For a system with constant thermal conductivity $k$, the resulting spherical equation is:$$\frac{1}{r^2}\frac{\partial}{\partial r}\left(r^2 \frac{\partial T}{\partial r}\right) + \frac{1}{r^2 \sin\theta}\frac{\partial}{\partial \theta}\left(\sin\theta \frac{\partial T}{\partial […]

To derive the heat conduction equation in cylindrical coordinates from Cartesian coordinates, we transform the Laplacian operator$\nabla^2 T = \frac{\partial^2 T}{\partial x^2} + \frac{\partial^2 T}{\partial y^2} + \frac{\partial^2 T}{\partial z^2}$ using the coordinate definitions $x = r \cos\theta$ and $y = r \sin\theta$. Assuming a constant thermal conductivity $k$, the Cartesian equation is:$$\frac{\partial^2 T}{\partial x^2}