Dehumidification of sewage sludge using quonset solar tunnel dryer: An experimental and numerical approach

In this study, it is aimed to design an efficient and sustainable solar tunnel dryer to be used in drying process of sewage sludge. In the first step of this study, heat and flow structure of three tunnel dryers including rectangular tunnel (RSTD), quonset tunnel (QSTD) and quonset tunnel with fins (QSTD/F) have been numerically surveyed to determine the effective design. Based on CFD results, quonset-type tunnel designs have been fabricated, experimentally analyzed and compared with numerical findings. In this work, different from previous studies on quonset-type solar-thermal systems, top surface of quonset geometry was made from sheet metal as an absorber to enhance heat transfer area. The drying tests have been performed in different months of the year (June and January) by applying two different air velocities to evaluate the performance of tunnel dryers at various climatic conditions. Integrating fins to the quonset tunnel had considerable positive effects on both thermal and drying performances. According to the experimental findings, specific moisture extraction rate (SMER) value was attained on June and January in the range of 0.50–0.89 and 0.39–0.65 kg/kWh, respectively. The results indicated the successfulness of quonset solar tunnel dryer design in the dehumidification process of sewage sludge.