Análise da secagem em leito espesso com e sem reversão de escoamento usando degraus de aquecimento: ensaios numéricos
Abstract
The drying process may seem mistakenly simple. It includes several complex
mechanisms of heat and mass transfer that make the development of mathematical
models considerably harder. As a consequence, instantly controlling and optimizing this
process has become a well studied challenge. The simplest drying technic is the fixed
bed drying, as it occurs when, as an example, the coffee beans are open-air dryed on
large cement, bricks or asphalt surfaces. The fixed bed drying is widely used in
industries, mainly as packed bed columns. This equipment can be used in small scale
batch drying of seeds with seeds that are sensible to mechanical schocks, in cases where
the moving dryers are not able to operate. Another alternative to fixed bed drying is
through the use of treadmills, that allow a continuous operation. A well-known
downside of the fixed bed process is the lack of homogeneity in the product, caused by
the high temperature and moisture gradients during the drying phenomenon. The
application of timed reversal on the airflow direction through the bed results in a
product with higher homogeneity. The present thesis here summarized aims to simulate
the dynamic behaviour of the fixed bed drying with and without airflow reversal
combined with stepwise temperature changes.
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