Drying process. Calculation of energy costs

The calculation of energy consumption during the drying process is performed according to the following formulas:

There are three ways to calculate energy consumption. According to the first option, the indicators of heat and mass of the output product are taken into account. The calculation formula is as follows:

The moisture transfer is small, and the phase transformation is equal to 1. Zones of concentration in this case become the main calculation unit for indicators of mass conductivity and moisture content. Moreover, these indicators take into account the value of the initial and final result of moisture content. The product passes from a state of increased humidity content to a state of reduced humidity concentration, and then its complete loss. That means the heat exchange remains the same, and the concentration of the moisture is lost. Applying this calculation formula, it is necessary to know many coefficients, such as: heat, mass, thermal conductivity, heat transfer. In the process of calculations, it is necessary to pay attention to the interaction of these indicators with the value of temperature and humidity.

The second calculation option is related to the mass conductivity index. This option is the most economical because it does not require knowledge of a large number of indicators. To calculate them, you need to draw a curve in the form of a graph, which will display all the necessary numerical data. They take the average and internal indicators of temperature and moisture, then take into account their relationship, displaying it on a graph. Experiments that study the kinetics of the drying and heating processes of particles of the same material help to reveal their correlation.

The third option is to calculate the thermal conductivity indicators. Mass conductivity is not taken into account here due to the fact that the curve of temperature and moisture of the material is drawn. All the necessary data for calculations is obtained from this curve. It reflects the concentration zones in which there was a reduced or increased heat content. Based on these data, the efficiency is analyzed.

Calculation methods

The various calculation methods are used: zone-based iterative and simplified iterative. The zone-by-zone iterative method requires a more detailed consideration of humidity and temperature indicators at each of the segments of their interaction. This operation is more time consuming compared to the simplified calculation method. Simplified calculations are that during the drying process, the product is processed, and at different stages, different indicators of the degree of readiness of the material are distinguished. The simplified method facilitates the division of processing stages into zones and their subsequent analysis in order to identify the best temperature regime for a particular product.

These methods can be successfully combined with the options described above.

To make the calculations accurate, use, in addition to graphs, computing tools and devices that help to calculate not only the temperature and humidity resistance of the product, but also heat exchange, thermophysical indicators.

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