Abstract
A model for the simulation of timber drying in a batch kiln has been used for the investigation of a set of different questions related to this drying process. The model is global in the sense that it takes into account that the drying air local climate changes as it passes through the kiln load. In Scandinavian, practice kiln stacks are normally built from boards of random lengths so that every second board is located flash at one end of the stack and the other boards flash at the other end. This kiln stack geometry is also included, as well as airflow reversal.This model has been utilized to investigate the following situations:The effect of sticker thickness on airflow, drying time and final MC standard deviation is illustrated.Thicker stickers mean less timber in a given kiln, but results in shorter drying time. The kiln drying capacity is not influenced very much, but the final MC spread is decreased.The influence of kiln parameters on the final MC standard deviation is investigated and simple formulas are presented for the estimation of this variation.
Highlights
There has always been a wish to increase the size of timber drying kilns in order to decrease the investment cost for the kiln, calculated per timber volume
In Scandinavian practice, kiln stacks are normally built from boards of random length so that every second board is located flash at one end of the stack, and the other boards flush at the other end
The results show clearly that a considerable improvement in the final MC variation within the kiln load is obtained with thicker stickers
Summary
There has always been a wish to increase the size of timber drying kilns in order to decrease the investment cost for the kiln, calculated per timber volume. In Scandinavian practice, kiln stacks are normally built from boards of random length so that every second board is located flash at one end of the stack, and the other boards flush at the other end This produces a center part of the stack where all positions are filled, and end parts of the stack where every second position is empty. This situation will increase the difference in drying behavior in different parts of the kiln stack. The airflows through the center and end parts as well as the stack bypass and their mixing behavior are included in the model. In (Salin, 2001) some aspects were discussed and in the following a few other questions are considered
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