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March 2017 (published: 30.03.2017)
Home > Issue > Simulation of biomass freezing at cryofreezing
Simulation of biomass freezing at cryofreezing
Zaitsev A.V., Kublitskiy S.E. , Pelenko V.V.
The task of modeling thermal processes during cryogenic freezing of the objects of biological origin (in particular, the foodstuff) is formulated and solved by numerical methods. Mathematical model of cryofreezing for biological objects in the form of heat balance equation (heat conductivity equation) is presented and its numerical realization is made by the method of final differences. To ensure the information value of the solution propsed, its analysis, as well as the possibility of greater variation and changes in the range of the task parameters in the research process of cryogenic freezing, our own calculation program of the object processes is written in Fortran. The following parameters are chosen as the boundary conditions: constant temperature on the heat removal surface which is the boundary condition of the type I, and constant density heat flow on this surface which is the boundary condition of the type II. The dependence of thermophysical properties of biological tissues from the target temperature contributes significant nonlinearity to the thermal conductivity equation and makes it difficult to solve the problem by analytical methods. Three stages of cryogenic freezing for the objects of different geometric shapes are considered: cooling the material to the cryoscopic temperature, freezing the liquid phase, cooling the ice to the desired temperature. The application of the technique proposed allows forecasting the cooling regime for the purpose of the necessary temperature achievement in the specified points of the object in the given time. Thus, at the relatively lower energy consumption, such technologies allow to obtain products and high quality objects while preserving most of their native properties, biologically active elements, and to implement energy-saving processes.
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Keywords: cryogenic freezing; heat balance; thermal conductivity equation; boundary conditions; thermophysical properties; numerical solution
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