Vasileios K. Firfiris 1,*
Zoi D. Kaffe 1
Sotirios D. Kalamaras 1
Antonios A. Lithourgidis 1
Anastasia G. Martzopoulou 2
Thomas A. Kotsopoulos 1,*

1 Department of Hydraulics, Soil Science and Agricultural Engineering, School of Agriculture, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece

2 School of Architecture, Faculty of Engineering, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece

* Authors to whom correspondence should be addressed.

Appl. Sci. 2022, 12(22), 11784; https://doi.org/10.3390/app122211784

Received: 14 October 2022 / Revised: 11 November 2022 / Accepted: 17 November 2022 / Published: 19 November 2022

Abstract
Agricultural product drying is of great importance as it is a reliable method for fruit and vegetable preservation. Tackling the high energy consumption of the process will reduce the final product cost and mitigate greenhouse gas emissions. In this work, a passive drying method was experimentally evaluated. The method was based on the principle of the stack effect taking place in the solar chimney structure. Different types of solar chimneys in terms of dimensions and materials were evaluated for the drying of banana and potato slices. The results of the experiments showed that the drying rate was close to solar drying systems. Parameters such as height and material characteristics of drying tubes, as also weather conditions, influenced the drying rate. It was found that the banana and potato slices were dried at a satisfactory rate for almost 48 h during the summer period in Greece. From the parameters of the drying tubes that were varied, it was found that both the height and material played a major role, as did the air flow rate. With the increase in the drying tube by 1 m and with the choice of proper manufacturing material, an increase in the flow rate between 40% and 100% can be achieved. When only the color of two 3 m-high tubes changed, the flow rate varied between 4% and 15%. The proposed method has almost zero energy consumption, and it could be used as a standalone or as a part of a hybrid drying system. It can also be adjusted in existing greenhouse-type agricultural structures as a parallel operation system.

Keywords: passive drying; solar drying; solar chimney; greenhouse; drying tube; dried agricultural products

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Πηγή: https://www.mdpi.com/2076-3417/12/22/11784

Funding
This research has been co-financed by the European Regional Development Fund of the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH–CREATE–INNOVATE (project code: T1EDK-00100).