Characterisation of the maximum entropy change in the process of drying materials based on a heat pump

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Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2024-01
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Language
en
Pages
12
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Thermal Science and Engineering Progress, Volume 47
Abstract
This paper studies the maximum entropy change characteristics under different working condition parameters (e.g. inlet temperature, air volume, initial sludge temperature and sludge radius) based on the validated model. Spherical sludge blocks were used as drying materials, and heat was provided by a heat pump system. Theoretical models of mass balance, energy balance and entropy balance in the drying process are established, and the model is validated with experimental results. The results show that the change in sludge entropy during the drying process is mainly caused by irreversible moisture diffusion, heat transfer and pressure. There is a peak of entropy change when the entropy value initially climbs and then declines. The lower the peak of entropy change, the smaller the irreversible dissipation in the drying process; however, the entropy change is not the main factor of drying time. For every 5 ℃ increase in inlet drying temperature, the entropy change peak increases by 5.2 ∼ 18.6 % and the drying time is shortened by 27.5 %. The entropy changes the peak increase with the rise in inlet air volume, while the drying time initially shortens and then changes slightly, and the optimal air volume interval exists. For every 0.01 m decrease in sludge radius, the entropy change peak reduces by 9.4 ∼ 23.8 %, and the drying time is shortened by 19.8 ∼ 33.1 %. The change in the initial sludge temperature has little impact on the entropy of the drying process.
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Mao , Y , Li , Y , Yuan , X & Kosonen , R 2024 , ' Characterisation of the maximum entropy change in the process of drying materials based on a heat pump ' , Thermal Science and Engineering Progress , vol. 47 , 102292 . https://doi.org/10.1016/j.tsep.2023.102292