Waste heat recovery in commercial gas-fired tumble dryers

Bachir El Fil and Srinivas Garimella

Energy, 2021, vol. 218, issue C

Abstract: Thermal drying is energy intensive due to the unavoidable thermodynamic constraint of supplying sufficient energy to evaporate the water (hfg > 2000 kJ kg−1). Textile dryers only use about half (∼55%) of the total input energy for drying. To reduce the wasted energy, exhaust gas recirculation and waste heat recovery using a recuperative heat exchanger are investigated numerically and experimentally. The two methods aim to recover energy from the exhaust stream typically at T < 55 °C for most of the drying period. Experiments are conducted on a commercial gas-fired tumble dryer. A theoretical model is developed to simulate and optimize the drying process. Recirculating the hot humid exhaust gases improves heat and mass transfer in the drum; however, the high humidity ratio of the recirculated air is not amenable to enhancing evaporation. An optimal recirculation ratio of 51% is found to reduce the specific moisture extraction ratio and drying time by 9% and 164 s, respectively. To avoid the rise in humidity associated with recirculation, a compact plate-fin heat exchanger is used to recuperatively preheat the air entering the combustor. Energy savings of ∼15% and reduction in drying time by 216 s over the baseline case are estimated. The predicted data demonstrate good agreement with experiments.

Keywords: Low-grade heat; Waste heat recovery; Gas-fired dryers; Energy efficiency (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (3)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:218:y:2021:i:c:s0360544220325147

DOI: 10.1016/j.energy.2020.119407

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