Wpływ wilgotności i gatunku drewna opałowego na przebieg procesu łupania

Traditional firewood is still the most popular type of solid fuel. This is mainly because of the availability of raw materials and simple production process, which involves mostly just sawing and cleaving. Cleaving increases the surface of the wood through which water evaporates, which in turn speeds up the drying. Dry wood has a higher calorific value and its combustion releases less harmful carbon monoxide and hydrocarbons. Wood cleaving process can be divided into three phases that lasts from the introduction of the wedge till the appearance of a crack (phase I), from the appearance of the crack till the stop of the slots (phase II) and then until the piece of the wood is completely cleaved (phase III). Although it is a conditional phase and it does not always occur in the case of the firewood species popular in Poland, the last phase takes the longest and has the greatest impact on the cleaving performance. The aim of the study was to determine the effect of wood and its moisture content on the duration of the phase III during the trial cleaving. The tested samples comprised of five popular in Poland species: hornbeam, beech, birch, alder and ash. The cleaving were carried out immediately after cutting and sawing the timber and after 3−month−long period of natural drying. For hornbeam, beech and alder humidity does not affect the hollow wedge in wood at the time of rupture. The duration of phase III was significantly longer than duration of phases I and II for each species independently of humidity. Significant dependence was observed for depression wedge as a function of humidity obtained in phase I and II for silver birch, and in phase III for ash.