# [[Dispersed-continuous interaction]] Interfacial area per unit cell volume for dispersed spheres $ \frac{A_p}{V}=\underbrace{\frac{\text{Volume of spheres}}{\text{Volume of cell}}}_\text{volume fraction of spheres}*\frac{\text{Surface area of spheres}}{\text{Volume of spheres}} $ $ \frac{A_p}{V}=r_p\left(\frac{\pi d^2_p}{\pi d^3_p/6}\right) $ $ \frac{A_p}{V}=\frac{6r_p}{d_p} $ Interfacial area per unit volume Interfacial area density If spheres have different sizes, another [[Transport equations|transport equation]] is solved # [[Continuous-continuous interaction]] $ \frac{A_p}{V}=|\nabla r_p| $