Calculation of convective drying parameters taking into account the object kinetics

When drying agricultural products, drying modes are determined based on the quality of the dried product and energy consumption is taken into account in the second place. As a rule, quantitative assessment of the effect of drying modes on energy consumption is not carried out. Traditional methods of calculating drying plants involve determining the total amount of evaporated moisture under the assumption of its uniform intake. During natural drying process, moisture release does not occur uniformly and depends on the drying stage. The amount of moisture released per unit of time can be calculated from the drying curve based on experimental data. This article presents the results of assessing the effect of the temperatures of the air supplied and removed from the drying zone on the specific heat consumption produced using the traditional calculation method. Thus, when the air heating temperature in the heater is from 20 to 60 °C, the temperature of the air removed from the drying zone is reduced from 55 to 35 °C, the specific heat consumption is reduced by 4.5 times, when heated to 90 °C – by 1,6 times. To account for the effect of uneven moisture release during drying, a technique based on step-by-step calculation of the moisture released along the drying curve and subsequent calculation of heat and air consumption is proposed. Calculations performed for drying carrots to 18 % with an initial humidity of 83 % show that in the initial period, the consumption of heat and air is 3 times higher than that at the end. Obviously, not taking into account the uneven release of moisture during drying in the initial period can lead to condensation of moisture on the material dried in the chamber, which increases the drying time, and at the end of drying – to overconsumption of heat.