Transient thermal behaviour of phase-change processes in solid foods with variable thermal properties Original Research Article

In this work we study the transient temperature fields and heat fluxes for simple or multilayer foods with planar, cylindrical or spherical geometry in one-phase or two-phase (phase-change) processes. The temperature dependencies of the thermal properties conductivity and/or specific heat are assumed to be specified as arbitrary and continuous functions. These dependencies are normally very pronounced in these products in the phase-change temperature interval. Interpolation tables or piece-wise functions, which are widely used in foods, may also be considered. Simple boundary conditions such as isothermal, convective and radiative, or any kind of compatible combination of lineal and/or non-lineal conditions may also be assumed with no special requirements. The problem, expressed by way of only one governing equation for both phases is solved numerically by the Network Simulation Method. This method, which has been recently applied to a great variety of non-lineal transport problems, only requires the use of finite-difference schemes for the spatial variable. The time remains as a continuous variable. Application to the freezing of white fish is presented.