Engineering Approach for Computation of the Energy Consumption Needed for Defrosting and Subsequent Heating of Frozen Wood Chips

Abstract

An engineering approach for the calculation of the specific mass energy consumption, which is needed for defrosting and the subsequent heating of the frozen wood chips above the hydroscopic range, (in kWh·t-1), has been suggested. Equations for easy calculation of have been derived, depending on the wood moisture content u, on the fiber saturation points of the wood species at 20 °C and at –2 °C (i.e. at 293.15 K and at 271.15 K), and respectively, on the initial chips’ temperature, T0 , and on the final temperature of the heated after their defrosting chips, T1.For the calculation of the according to the suggested approach and equations a software program has been prepared in MS Excel 2010. With the help of the program calculations have been carried out for the determination of the energy consumption , which is needed for defrosting and subsequent heating of oak, acacia, beech, and poplar frozen chips with moisture content in the range from u = 0.4 kg·kg-1 to u = 1.0 kg·kg-1, initial temperature t0 = –20 °C and t0 = –10 °C until reaching of the chips‘ mass temperature of t1 = 80 °C, t1 = 100 °C, and t1 = 120 °C at the end of the heating.

A Simulation Study of the Heat Balance of Concrete Pits During Boiling of Non-Frozen Logs

“…When τ 2 is reached, the logs subjected to boiling reach the optimal temperature required for their subsequent mechanical processing in the veneer production. Mathematical descriptions of all the thermo-physical characteristics of the non-frozen wood, which are involved in model ( 1) − (3), have been carried out and verified with foreign experimentally obtained dissertation data in Deliiski [2][3][4][5] and Deliiski et al [7] as a function of the temperature and wood moisture content. The mathematical description of the operating medium temperature in the pit shown in Figure 1, t m , is analogous to that proposed in Deliiski [2], and Deliiski and Dzurenda [6] for t m in autoclaves for steaming wood materials.…”

“…When the length of the logs (L) is at least four times their diameter (D), their required heating duration can be determined using the following experimentally verified 1D model [3,5]:…”

Computing the Thermal Efficiency of Autoclaves during Steaming of Frozen Prisms for Veneer Production at Changing Operational Conditions

“…The effective specific heat capacities of the wooden prisms during their defrosting, c w-eff1,2,3 , which participate in Equation (1), are described mathematically as follows [6,20,26,32,45]:…”

“…The defrosting process of ice-containing wood materials during steaming for the purpose of plasticization in the production of veneer takes place in three stages [14,20,32]. Figure 1 shows these three stages, as well as the symbols of the thermo-physical characteristics of the wood in each of them, for which it is necessary to have a mathematical description when solving the model ( 1)-( 5).…”

“…Heat treatment modes are usually presented in the literature sources, which are applied in practice to ensure the minimum possible duration of the wood heating process and maximum productivity of the equipment [5][6][7][8][9][10][11][12][13][14][28][29][30][31][32][33][34][35][36]. These sources completely lack data on modes in which dispatcher intervention increases their duration in order to ensure the necessary wood plasticity is achieved later than the usual time due to changed operational conditions.…”