СЪДЪРЖАНИЕ
- Г. Петров, Битови манипулации и хардуерни оптимизации за бързи трансцендентни функции в Edge и IoT устройства
- автоматика
Н. Делийски, Л. Дзуренда, Д. Ангелски, П. Вичев, К. Атанасова, Изчисляване на топлинния баланс и КПД на бетонни ями при пропарване на фурнирни трупи в тях - П. Благов, П. Русков, Европейските проекти EBSI-NE (Node Expansion) и OnePass: рамка за доверие между стартиращи компании, инвеститори и оператори на услуги
Key Words: Concrete pits; veneer logs; steaming; thermal balance; energy efficiency.
Abstract. A methodology for computing the thermal balance and energy efficiency of concrete pits when steaming veneer logs in them has been presented. The methodology is based on the use of two personal mathematical models: 1D non-linear model of the unsteady temperature distribution along the radius in the central cross section of non-frozen logs at conductive boundary conditions, and a stationary model of the thermal balance of concrete pits when steaming wood materials in them. For numerical solving of the models and practical application of the suggested methodology, a software packages were prepared in the calculation environment of Visual FORTRAN Professional and in Excel respectively. With the help of the first model, the steaming times of beech logs with a diameter of 0.4 m, initial temperature of 0, 10, and 20 °C and moisture content of 0.4, 0.6, and 0.8 kg∙kg-1 were determined at operating temperatures in the pit equal to 70, 80, and 90 °C. Using the determined logs’ steaming durations, with the help of the second model the change in the energy required for the entire steaming process and that for each of the components of the pit’s thermal balance was calculated. The thermal efficiency of a concrete pit was also determined under different combinations of factors affecting the steaming of the logs. Computer simulations were performed for a well-insulated pit with working volume of 20 m3 and degree of filling it with logs 45%, 60%, and 75%. It has been established that the energy consumption of the pit decreases from 122.8 to 106.3 kWh·m-3 when the initial temperature of logs with a moisture content of 0.6 kg∙kg-1 is increased from 0 °C to 20 °C, and their logs heating is realized at a temperature of the steaming medium of 80 °C and a maximum possible in practice degree of filling the pit with logs of 75%. The increase in the temperature in the pit from 70 to 90 °C at its 75% filling with logs with an initial temperature of 10 °C and a moisture content of 0.6 kg∙kg-1 causes an increase in its energy consumption from 103.4 to 127.0 kWh·m-3. In these two cases, the thermal efficiency of the pit decreases – in the first case from 41.8% to 35.7% and in the second case – from 39.1% to 38.9%. The increase in the moisture content of the logs from 0.4 to 0.8 kg·kg-1 causes an increase in the energy consumption of the pit from 104.3 to 125.2 kWh∙m-3 at its 75% filling and steaming at 80 °C of logs with an initial temperature of 10 °C. In this case, the thermal efficiency of the pit increases from 34.3% to 42.9%. The presented methodology can be used to calculate the thermal balance and efficiency of concrete pits with different geometric and thermophysical parameters when steaming logs of different wood species to any desired degree of heating and plasticization in the production of veneer
