Box model
= Box model
{wiki}
A <box model> represents a system by finitely many internally uniform compartments. Balances of transported material and local sources give coupled <ordinary differential equations>. For a constituent's <concentration> $c_i$ in fixed box <volume> $V_i$, the stored amount is $V_ic_i$; changing <volumes> requires the balance of that product. A transport-only closed <box model> preserves total inventory, even when its transport <matrix> is nonsymmetric.