Effect of Weather on Dry Kiln Venting Losses

As an aside to a solar kiln study conducted near Jackson, Mississippi, it was noted that outside weather conditions had a significant effect on venting during both conventional and solar kiln-drying. When conditions of high humidity exist outside a kiln, an excess amount of venting occurs with accompanying large heat losses. This may be so severe in the temperate United States as to cause higher total energy requirements for drying during humid summer conditions than in winter. For conditions under which this study was conducted, total heat requirements per charge were estimated to be 13.2 x 107 Btu for summer operation and 10.6 x 107 Btu during winter. Since the study was not designed to monitor energy requirements during kiln-drying, no empirical data were gathered. Had actual data been gathered, losses due to venting would likely have been discovered to have been much larger. This is due to the assumption made in the estimate that kiln operation was suspended or the vents closed when humidity levels set inside the kiln were below those outside. In typical commercial practice, this most likely would not be done. When operating a dry kiln under conditions of high outside humidity, modifications in operational technique and/or schedule may help reduce venting losses. In some cases, extreme measures such as a change in drying method may be the only answer. Whatever method is selected, operator awareness and monitoring are essential if losses are to be minimized.

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