Modeling latent heat fluxes of water in logs during their freezing = Modeliranje latentnih toplinskih tokova vode u trupcima tijekom zamrzavanja / Nencho Deliiski, Natalia Tumbarkova.
Sažetak

This paper suggests a methodology for mathematical modelling and research of two interconnected problems: 2D non-stationary temperature distribution in logs subjected to freezing and change in the latent heat fluxes of the free and bound water in logs during the freezing process. For the purpose of this methodology, a 2-dimensional mathematical model has been created, solved, and verified for the transient non-linear heat conduction in logs during their freezing at convective boundary conditions. The model includes a mathematical description of the specific latent heat fluxes, qLHv-fw and qLHv-bw, formed by the freezing of the free and bound water in the logs, respectively. The paper presents solutions of the model with explicit form of the finite-difference method in the calculation environment of Visual Fortran Professional and its verification in accordance with our own experimental studies. The paper presents the results of simulation analysis of 2D non-stationary temperature distribution in the longitudinal section of pine log with a diameter of 0.24 m, length of 0.48 m, and moisture content above the hygroscopic range during its 30-hour freezing in a freezer at the temperature of the processing air medium of approximately –30 °C. The change in the latent heat fluxes qLHv-fw and qLHv-bw during the log freezing is presented, visualized, and analyzed.; Predložena je metodologija za matematičko modeliranje i istraživanje dvaju međusobno povezanih problema: dvodimenzionalne nestacionarne raspodjele temperature u smrznutim trupcima i promjene u protoku latentne topline slobodne i vezane vode u trupcima tijekom zamrzavanja. Za realizaciju metodologije izrađen je i provjeren dvodimenzionalni matematički model za nelinearno provođenje topline u trupcima tijekom zamrzavanja pri konvekcijskim rubnim uvjetima. Model obuhvaća matematički opis specifi čnih latentnih tokova topline qLHv-fw i qLHv-bw, koji nastaju zamrzavanjem slobodne i vezane vode u trupcima. U radu su prikazana rješenja modela s eksplicitnim oblikom metode konačnih razlika u računalnom sučelju Visual Fortran Professional i njegova provjera prema vlastitim eksperimentalnim istraživanjima autora. Predstavljeni su rezultati simulacijskog istraživanja dvodimenzionalne nestacionarne raspodjele temperature u uzdužnom presjeku borovih trupaca promjera 0,24 m, dužine 0,48 m i sadržaja vode iznad higroskopskog raspona tijekom 30 sati smrzavanja u zamrzivaču, pri temperaturi zraka oko –30 °C. Također su prezentirane i analizirane promjene protoka latentne topline qLHv-fw i qLHv-bw tijekom zamrzavanja trupaca.