An Approach for Computing the Heat Sources in Logs Subjected to Freezing

This study suggests an approach for computing the specific energies of the internal heat sources in logs subjected to freezing. The approach maximally considers the physics of the freezing processes of both the free and the bound water in wood. It reflects the influence on the mentioned energies of the wood density above and below the hygroscopic range. It also considers the icing degrees formed separately by both the free and bound water in the logs, as well as the influence of the fiber saturation point of each wood species on its respective amount of non-frozen water depending on temperatures below 272.15 K. Mathematical descriptions of the specific heat energies Qv-fw and Qv-bw released in logs during free water freezing in the range from 0 °C to −1 °C and of the bound water below –1 °C, respectively, have been executed. These descriptions are introduced in own 2D non-linear mathematical model of the freezing process of logs. For the solution of the model and computation of the energies Qv-fw and Qv-bw, a software program based on the suggested approach and mathematical descriptions was prepared in FORTRAN, which was input into the calculation environment of Visual Fortran. With the aid of the program, computations were completed to determine the energies Qv-fw and Qv-bw and their sum, Qv-total of a beech log subjected to freezing. The beech log had a diameter of 0.24 m, a length of 0.48 m, an initial temperature of 20.5 °C, a basic density of 683 kg·m−3, and a moisture content of 0.48 kg·kg–1 during its 30 hours in a freezer at approximately −30 °C.