Thus, the enthalpy balance (eqn. (10) and eqn. 5, the constitutive equation for T eq (m,n,p) form a system of two equations in two unknowns, subject to the initial condition in eqn. 11. Since the evolution of the vial is subject to Q(m,n,p) , which may depend on the state of the neighboring vials, the evolution of all vials is coupled and a system of (M ×N ×P) enthalpy balances has to be solved.