IMPACT OF OPERATING TEMPERATURE ON THE HEAT BALANCE AND EFFICIENCY OF PITS WHEN STEAMING UNFROZEN LOGS

Abstract

An approach for calculating the heat balance and thermal efficiency of concrete pits during the steaming of unfrozen logs intended for peeled veneer production is presented. Using our non-stationary model, the heating times of beech logs with a diameter of 0.4 m, an initial temperature of 10°C, and a moisture content of 0.6 kg·kg⁻¹ were determined at steaming-medium operating temperatures of 70, 80, and 90°C. Using the calculated heating times and our stationary model of the heat balance of concrete pits during log steaming, the total energy required for the entire steaming process and for each heat-balance component was calculated. Computations were per-formed for a concrete pit with overall dimensions of 7.4 × 2.8 × 2.5 m, a working volume of 20 m³, and filling degrees of 45%, 60%, and 75%. Increasing the operating temperature from 70 to 90°C at the maximum filling degree of 75% increased the pit energy consumption from 103.4 to 127.0 kWh·m⁻³ and slightly decreased its thermal efficiency from 39.1% to 38.9%.