IMPACT OF THE DEGREE OF FILLING OF A STEAMING PIT WITH FROZEN VENEER LOGS ON ITS HEAT BALANCE AND EFFICIENCY

Abstract

An approach for calculating the heat balance and thermal efficiency of concrete pits during the steaming of frozen logs intended for peeled veneer production is presented. Using our non-stationary model, the temperature field and heating times of beech logs with a diameter of 0.4 m, an initial temperature of −20°C, and moisture contents of 0.4, 0.6, and 0.8 kg·kg⁻¹ were determined at a steaming-medium operating temperature of 80°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 each of the five individual heat-balance components were calculated. Computations were performed for a concrete pit with overall di-mensions of 7.4 × 2.8 × 2.5 m, a working volume of 20 m³, and filling degrees f of 45%, 60%, and 75%. Reducing the filling degree from 75% to 45% decreased the thermal efficiency from 46.0% to 34.8%, from 52.4% to 41.0%, and from 56.6% to 45.4% at log moisture contents of 0.4, 0.6, and 0.8 kg·kg⁻¹, respectively. The proposed approach can be readily adapted to calcu-late the heat balance and efficiency of concrete steaming pits with different designs and con-struction parameters.