Author: Nencho Deliiski
Articles
 CALCULATION OF THE ENERGY CONSUMPTION FOR DEFROSTING OF THE WOOD CHIPS

Summary
Аn approach for the calculation of the specific mass energy consumption (in kWh.t^{1}) needed for defrosting of the wood chips, which contain both frozen bound an free water, has been suggested. For the calculation of the 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 for 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} and with an initial temperature at the range from t_{0} = –40 ^{o}C to t_{0} = –1 ^{o}C. At temperature equal to –1 ^{o}C the defrosting process of the wood chips has been fully completed.
Keywords: wood chips, defrosting, frozen bound water, frozen free water, specific mass energy consumption
 COMPUTATION OF THE AVERAGE WOOD TEMPERATURE AND THE RATE OF ITS CHANGE DURING UNILATERAL HEATING OF FLAT SPRUCE DETAILS BEFORE THEIR BENDING

Summary
An approach for the computation of the average mass temperature of the wood and the rate of its change during unilateral heating of flat wood details aimed at their plasticizing in the production of curved outside parts for corpses of stringed music instruments, has been suggested. The approach is based on the numerical integration of the solutions of a linear model for the calculation of the nonstationary 1D temperature distribution along the thickness of subjected to unilateral heating flat wood details.
Keywords: average mass temperature, rate of change in average temperature, spruce details, unilateral heating, plasticizing
 COMPUTATION OF THE HEAT FLUX NEEDED FOR UNILATERAL WARMING UP OF FLAT SPRUCE DETAILS BEFORE THEIR BENDING

Summary
An approach for the computation of the heat flux, which is needed for warming up of flat wood details during unilateral heating aimed at their plasticizing in the production of curved outside parts for corpses of stringed music instruments, has been suggested. The approach is based on the numerical integration and differentiation of the solutions of a linear model for the calculation of the nonstationary 1D temperature distribution along the thickness of subjected to unilateral heating flat wood details. The paper presents solutions of the model concerning the nonstationary change in the specific heat flux needed for warming up of flat spruce details with thicknesses of 6, 8 and 10 mm during their unilateral heating at temperatures of the electrically heated metal band equal to 100, 120, and 140 ^{o}C.
Keywords: unilateral heating, flat wood details, heat flux, plasticizing, bending
 MATHEMATICAL DESCRIPTION OF THE SPECIFIC HEAT CAPACITY OF THE WOOD ABOVE THE HYGROSCOPIC RANGE DURING WOOD FREEZING

Summary
A mathematical description of the specific heat capacity c of wood above the hygroscopic range during wood freezing has been suggested. The description takes into account the physics of the freezing process of both the free and the hygroscopically bound water in the wood. It reflects also the influence of the fiber saturation point of wood species on the value of their c during wood freezing and the influence of the temperature on the fiber saturation point of the wood during its freezing. A software program has been prepared for the computation of c according to the suggested mathematical description. With the help of the program, computations have been done for the determination of c of often used in veneer and plywood production beech and poplar wood with moisture content 0.4 kg∙kg^{1}≤ u≤1.2 kg∙kg^{1} at the temperature range between 0 ^{o}C and –60 ^{o}C during freezing of the wood.
Keywords: wood, freezing, specific heat capacity, mathematical description, bound water, free water, computatio
 TRANSFORMATION OF TWO MUTUALLY CONNECTED MODELS FOR CONVECTIVE HEATING OF WOOD DETAILS BEFORE THEIR LACQUERING IN A FORM, SUITABLE FOR PROGRAMMING

Summary
Using the explicit form of the finitedifference method, two suggested by the authors mutually connected mathematical models have been transformed in a form, suitable for programming. For the numerical solution of the transformed models, a software program has been prepared in the calculation environment of Visual Fortran Professional. With the help of the program, the 1D distribution of the temperature along the thicknesses of flat oak details and of their carrying transport rubber band with h_{w} = 16 mm, l_{w} = 0.6 m, u = 0.08 kg.kg^{1}, h_{B} = 4 mm, b_{B} = 0.8 m, and t_{0} = 20 ^{o}C, during unilateral convective heating for a period of 10 min at t_{ha} = 100 ^{o}C, v_{ha} = 2 m·s^{1}, 5 m·s^{1}, 8 m·s^{1}, and t_{nha} = 20 ºC in order to ensure suitable thermal conditions for the subsequent details’ lacquering has been calculated, visualized and analyzed.
Keywords: oak details, unilateral convective heating, lacquering, carrying rubber band
 APPLYING THE SOFTWARE PACKAGE TABLE CURVE 2D FOR COMPUTATION OF PROCESSING AIR MEDIUM TEMPERATURE DURING FREEZING IN A FREEZER AND DEFROSRING OF LOGS

Summary
A mathematical description of the change in the processing air medium temperature T_{m }during freezing in a freezer and subsequent defrosting of logs using a software package Table Curve 2D v.5.01 has been suggested. This package allows for the selection of equations, which provides the best similarity between the calculated with them values of T_{m} during the log’s freezing and defrosting processes and the respective experimentally established data for T_{m}. The values of the coefficients in the selected equations have been determined in the work for the cases of decreasing in T_{m} in the range from about 20 ^{о}С to about –30 ^{о}С during separately 30 h freezing and of the following increasing in T_{m} up to about 20 ^{o}C during the subsequent 30 h or 50 h defrosting of 6 pine logs with diameter of 240 mm and length of 480 mm.
Keywords: temperature, processing air medium, freezing, defrosting, pine logs, Table Curve
 COMPUTATION OF THE ENERGY CONSUMPTION FOR WARMING UP OF FLAT OAK DETAILS BEFORE THEIR BENDING

Summary
A software program has been prepared in the calculation environment of Visual Fortran for solving of own 1D nonlinear model of the one sided heating process of flat wood details. With the help of the program, the 1D nonstationary temperature field in flat oak details with initial temperature of 20 ^{o}C, moisture content of 0.15 kg.kg^{1}, thickness of 12 mm, 16 mm, and 20 mm during their 30 min one sided heating at temperature of 80 ^{o}C of the heating metal body has been calculated. After integration of the temperature field, the energy consumption for warming up of the details before their bending in the production of curved back parts of chairs has been calculated. The obtained results are graphically presented and analyzed.
Keywords: oak details, one sided heating, bending, energy consumption
 COMPUTATION OF THE CHANGE IN THERMAL CONDUCTIVITIES OF POPLAR LOGS DURING THEIR FREEZING

Summary
A mathematical description of the thermal conductivities λ of frozen and nonfrozen wood has been introduced in an own nonlinear mathematical model of the logs’ freezing process. For the numerical solution of the model a software program has been prepared in the calculation environment of Visual Fortran Professional. With the help of the program, the 2D nonstationary distribution of the temperature and the change of λ in the longitudinal section of poplar logs with diameter of 240 mm and length of 480 mm during their 50 h freezing in a freezer at about –30 ^{o}C have been calculated. The change of λ in the radial and longitudinal directions of the wood on both surfaces and in the center of the subjected to freezing logs during the freezing process has been calculated, visualized and analyzed.
Keywords: poplar logs, freezing, radial thermal conductivity, longitudinal thermal conductivity, Visual Fortran
 MATHEMATICAL DESCRIPTION OF THE CHANGE IN THE ATMOSPHERIC TEMPERATURE DURING DAYS AND NIGHTS

Summary
A mathematical description of the periodically changing during many days and nights temperature of the atmospheric air as a processing medium has been suggested. It is introduced in the boundary conditions of our own mutually connected 2D nonlinear mathematical models of the logs’ freezing and defrosting processes. For the numerical solving of the models a software program has been prepared in the calculation environment of Visual Fortran Professional. Results from a simulative investigation of the 2D nonstationary temperature distribution in beech logs with a diameter of 0.24 m, length of 0.48 m, moisture content of 0.6 kg·kg^{1}, and initial temperature of 0 ^{o}C during their 5 days and nights continuous freezing and defrosting at sinusoidal change of the air temperature with initial values of –5 ^{o}C and different amplitudes are presented and analyzed.
Keywords: mathematical description, atmospheric air, temperature, 2D models, beech logs, freezing, defrosting
 COMPUTATION OF THE AVERAGE MASS THERMAL CONDUCTIVITY OF OAK FURNITURE ELEMENTS SUBJECTED TO CONVECTIVE HEATING BEFORE LACQUERING

Summary
A methodology for the computation and research of the following two mutually connected problems has been suggested: 1D nonstationary temperature distribution in subjected to unilateral convective heating process of flat wooden furniture elements before lacquering and change in their average mass thermal conductivity. For the realization of the methodology, created earlier by the authors 1dimensional nonlinear mathematical model has been solved for the transient heat conduction in the furniture elements during their unilateral convective heating. The model contains a mathematical description of the average mass thermal conductivity of the elements and their surface layer, which is intended for lacquering. For the numerical solution of the model with the aim of applying the methodology a software program has been prepared and input in the calculation environment of Visual FORTRAN Professional. Using the program, computations have been carried out for determination of the 1dimensional nonstationary temperature distribution along the elements’ thickness and of the average mass thermal conductivity for flat oak furniture elements with an initial temperature of 20 ^{o}C, moisture content of 8 %, thickness of 16 mm, width of 0.6 m, and length of 1.2 m during their 10 min unilateral convective heating at temperature of the processing air medium of 100 ^{o}C, which circulates above the elements with a velocity of 2 m·s^{1}, 5 m·s^{1}, and 8 m·s^{1} aimed at improvement of the conditions for the subsequent lacquering. During the computations a temperature of 20 ^{o}C for the surrounding air near the nonheated surface of the carrying rubber band has been used. The change in the average mass thermal conductivity of the studied furniture oak elements and also of their heated surface layers during the heating is graphically presented and analyzed.
Because of the wide range of applications, the need for paulownia is constantly increasing.
Keywords: oak furniture elements, one sided convective heating, lacquering, thermal conductivity
 CHANGE IN THE DURATION OF AUTOCLAVE STEAMING REGIMES OF NONFROZEN PRISMS AT DISPATCHING INTERVENTIONS IN THE PRODUCTION OF VENEER

Summary
An approach for computing and research of the duration of regimes for autoclave steaming of nonfrozen wooden prisms at limited heat power of the steam generator in cases of dispatching interventions into the regimes in order to obtain a duration that is suitable for the subsequent cutting of the veneer from the heated plasticized wood has been suggested. Using own 2D unsteady model implemented in the approach, calculations of the change of the duration of regimes for plasticizing of beech prisms in an autoclave have been carried out. The variables used during the computer simulation were, as follows: initial wood temperature of 0 °C, wood moisture content of 0.6 kg·kg^{−1}, and crosssection dimensions of the prisms 0.4 × 0.4 m; steaming autoclave with a diameter of 2. 4 m, length of 9.0 m, and loading level of 50% for the cases of lowering by the dispatcher the maximal temperature of the basic steaming regime from 130 ^{o}C to 120, 110, and 100 ^{o}C in the 3^{rd}, 5^{th}, and 7^{th} hour of this regime.
Keywords: wooden prisms, autoclave steaming, duration of regimes, dispatching intervention, veneer production