HEAT TRANSFER MODEL FOR PLUG-FLOW ANAEROBIC DIGESTERS

摘要

A comprehensive and fundamental mathematical model that predicts energy requirements to operate a plug-flow anaerobic digester at a specified temperature was developed. This information is supportive to designers as they determine heating requirements and energy use by the digester system. The model accounts for heat loss/gain by the influent and effluent flows, the digester floor, and the top-covering material and walls. In addition, the model accounts for frozen ground surrounding digester walls, thus increasing heat loss through the walls. Solar energy transmitted through the top-covering material is also accounted for in the model. Predicted heat was validated against experimental data, and the results agree reasonably well. The model can be used to estimate energy requirements to operate a plug-flow anaerobic digester on a daily, monthly, or yearly basis. Low energy was required to operate the digester in June through August, the lowest being in July, and more energy was required in November through March. Considerable energy could be saved if the effluent manure heat was used to pre-heat the influent manure