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Tropentag, September 14 - 16, 2022, Prague

"Can agroecological farming feed the world? Farmers' and academia's views."


Mathematical model to predict and simulate bulk tomatoes temperature stored in a nature-assisted low-cost-low-temperature storage structure for rift valley production area in Ethiopia

Samuel Eshetu1, Franz Roman2, Yetenayet Bekele Tola3, Oliver Hensel2, Werner Hofacker4

1Debre Berhan University, Dept. of Food Science, Ethiopia
2University of Kassel, Agricultural and Biosystems Engineering, Germany
3Jimma University, Post-Harvest Management, Ethiopia
4University of Applied Sciences Konstanz, Inst. for Applied Thermo- and Fluiddynamicas IATF, Germany


Abstract


Ethiopia, especially the rift valley region, produces a wide range of fruits and vegetables for the central market. Despite high production the post harvest loss due to absence of cooling room facilities is high. The use of commercially available mechanical refrigeration is expensive and cannot be afforded by local farmers. This work was conducted with the aim of developing a mathematical model and simulation to predict product temperature after employing combined use of three natures assisted cooling methods (daytime evaporative cooling (EC), nighttime ventilation (NV) and use of high thermal mass materials). A 3D time-dependent heat transfer in the moist air interface in COMSOL Multiphysics is employed to develop the model that predicts and simulates tomatoes' temperature stored in a low-cost low-temperature storage structure that combines that above cooling principles. The construction materials for the storage structure were high thermal mass materials. Simulation results indicate that, during daytime, employing an EC system for 10 hours provides a 9.65 K reduction in product temperature from an ambient temperature. Additionally, utilising the NV cooling system (when nighttime air temperature is cooler than storage room temperature) in tandem with high thermal mass materials for 8 hours enables to maintain the product temperature, assisted by the daytime EC system at around 298 K. Generally, employing EC and NV cooling systems with the assistance of high thermal mass material enables to create and maintain product temperature at least 10 K below ambient. Based upon the Q10 concept this temperature reduction could double the storage time of the fruit compared to fruits stored in ambient temperature.


Keywords: Evaporative cooling, nighttime ventilation, thermal mass, tomatoes


Contact Address: Yetenayet Bekele Tola, Jimma University, Post-Harvest Management, 307 Jimma, Ethiopia, e-mail: yetenayet@gmail.com


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