Experimental Study Regarding the Freezing and Thawing Dynamics of Spruce Wood

The article presents the results regarding theevolution of the temperature field in spruce wood(Picea abies L.) during freezing at two differentfreezing rates: -100C/h (rapid freezing) and -10C/h(slow freezing) and then during thawing at +50C,+30°C, +50°C temperature.This approach aimed at simulating thetemperature variations which occur inside timberduring open air storage in winter in two situations(sudden vs. gradual drop of temperature), and thenwhen the timber enters the drying kiln, depending onthe temperature applied in the initial heating phase.The results clearly show that the freezing ratesignificantly influences the thawing time and speed,which increase by 13-17% in the case of slowly frozenwood (at -10C/min) compared to rapidly frozen wood(at -100C/min). It was also established that theoptimum temperature in the heating-up phase whendrying frozen spruce is 300C instead of the usual500C. This value leads to much better dryinguniformity without significantly prolonging the dryingtime.