Modeling and simulation of heat transfer phenomena in a semi-buried anaerobic digester

A transient thermal model has been developed for predicting temperature variations in semi-buried anaerobic digesters as a function of climatic conditions (ambient temperature, solar irradiation, rain intensity, etc.). Compared to literature, the modeling of several heat transfer terms was improved. Predicted operating temperatures were in good agreement with experimental observations. The simulation results allowed identifying phenomena leading to major energy losses from the reactor. Technical solutions were recommended to reduce heat losses in anaerobic digesters. The present model constitutes a powerful predictive tool for assisting engineers in determining the optimal design of digesters, as well as in the investigation of the influence of materials type on the reactor heating requirements.