Publications

This study presents a new pneumatic air jet excitation nozzle, specifically designed for food processing applications. The device, which uses compressed air equipment and a precision solenoid valve, controls air discharge through a parametric air jet nozzle. Tests showed that the device could achieve shooting frequencies in the 40–45 Hz range, with operational pressures between 5 and 7 bar. A sensor system was used to measure the force generated by the device at different frequencies and pressures. Using the Design of Experiments (DOE) methodology, we identified optimal cavity designs for 5 and 6 bar pressures. These designs outperformed others in generating uniform force and maintaining consistent vibration voltage behavior. This highlights the efficacy of our approach in enhancing device performance under different conditions. The device’s practical application in food processing was demonstrated, particularly in delicate tasks such as the selective harvesting of sensitive crops like coffee fruits. The precise vibrations generated by the device could potentially enhance harvesting efficiency while significantly reducing mechanical damage to plants. The results position the device as a compelling proof of concept, offering an alternative method for exciting biostructures in food processing. This device opens up new possibilities in agricultural and biological fields, providing a non-intrusive and practical approach to manipulating and interacting with delicate, contactless structures, with a specific focus on improving food processing efficiency and quality. 

Cardona, C.I.; Tinoco, H.A.; Perdomo-Hurtado, L.; Duque-Dussán, E.; Banout, J. Optimizing Harvesting Efficiency: Development and Assessment of a Pneumatic Air Jet Excitation Nozzle for Delicate Biostructures in Food Processing. Foods 2024, 13, 1458, doi:10.3390/foods13101458.

This research aimed to provide a comprehensive set of tools to understand, simulate, predict and control the coffee drying process in different scenarios: Natural convection, forced convection and mixed. In different coffee-producing countries, the drying process poses a challenge to the coffee growers due to the complex phenomenon, considering that large amounts of water should be removed from the grain to protect it from bacteria, fungi and filamentous fungi development. However, the process must be thoroughly controlled to preserve the quality of the beans; this stands as an issue to the growers that are usually considered small because of their plot size and socio-economic conditions. In Colombia, around 96% of the 540000 coffee-growing families are considered small-scale farmers; this percentage relies mainly on sun-drying techniques to process their coffee. Nevertheless, the dependence of sun drying on the weather conditions is an issue since the harvesting times usually coincide with the rainy seasons, which are not the optimal conditions to dry coffee through natural convection due to the high ambient relative humidity and low temperatures. Therefore, mechanical dryers appeared as a solution seeing that the drying times are drastically reduced. Nonetheless, their elevated price and running costs prevent small-sized growers from acquiring these technologies. Therefore, wet coffee commercialization emerged as an answer, though the growers’ selling prices dropped drastically. Hence, a solution for the coffee growers seemed to be in place, integrating the product quality of sun-dried coffee and the technologies already existing in the farms (solar parabolic and tunnel dryers) with the rapid drying dynamics of mechanical dryers: a hybrid solar dryer. However, to achieve a proper design, independent studies were carried out on natural and forced convection drying of a coffee seed to provide predictive models to stochastic processes through Finite Element Methods (FEM) on mechanical drying to obtain mathematical models that simulate and characterize deep and thin bed drying of coffee and also, the thermal and physical properties of parchment coffee of new Colombian varieties were calculated not only to sharpen the mathematical and FEM and computational fluid dynamics models but also to update the literature. With this information, a hybrid solar drying unit was designed that provides a solution to coffee growers.

Duque-Dussán, Eduardo. ISBN: 978-80-213-3335-2 (2023). Czech University of Life Sciences Prague

Due to the extended drying time open-sun and solar drying of coffee procedures undergo, the development of microorganisms, mycotoxins and molds threaten the product. Alternatives such as mechanical dryers are available, nevertheless, their running costs and setups are usually expensive and unaffordable for small-scale coffee growers. Therefore, this research aimed to design, build and evaluate a hybrid solar dryer which mixes solar and mechanical drying principles. It uses a traditional solar tunnel-type dryer as a base featuring a biomass burner which uses coffee trunks left from the yearly crop renovation as biofuel. A heat exchanger heats the drying air, afterwards blown into a plenum chamber that homogenizes the air’s static pressure before crossing the coffee bed, ensuring an even moisture removal. Also, the hybrid unit includes a photovoltaic system to obtain a fully self-sufficient drying unit. The newly developed dryer was tested under three different configurations: Solar and mechanical day and night (C1), solar during the day and mechanical during the night (C2) and fully solar with non-mechanical aid (C3). The results displayed a notable drying time reduction in the three evaluated configurations: C1 reduced the drying time by 70.47%, C2 by 45.75% and C3 by 21.5%. Also, the predictive model for different plenum chamber heights was obtained through computational fluid dynamics simulations, where the ideal height was 0.25 m. A biomass consumption of 1.9 kg/h was registered. Also improved tem- perature and relative humidity profiles were achieved. Its design easily adapts to the existing tunnel and parabolic-type solar dryers.

Duque-Dussán, E., Sanz-Uribe, J. R., & Banout, J. (2023). Design and evaluation of a hybrid solar dryer for postharvesting processing of parchment coffee. Renewable Energy, 215(March), 118961. https://doi.org/10.1016/j.renene.2023.118961

The thermophysical properties of coffee have a special partaking during the drying process since a material-depending heat and mass transfer occurs between the bean and the drying air. Conditional to the thermophysical properties of the parchment coffee, the drying can be more or less efficient, affecting the final quality and seed safety. Several coffee varieties have been studied; however, the National Coffee Research Center of Colombia has developed new highly productive coffee varieties resistant to different diseases: Cenicafé 1 and Castillo®. Nevertheless, the thermo- physical properties of these specific varieties were not yet investigated; moreover, the availability of information related to these properties of different coffee varieties in the literature is relatively scarce. Thus, this study targeted to determine the parch- ment coffee thermophysical properties of these new varieties at five different mois- ture contents % (wb): 53%, 42%, 32%, 22% and 11%, using optimized techniques and methods to ensure high accuracy and exactness. It was found that the new varieties have larger, heavier, and denser beans; it was also seen that the bulk thermal conduc- tivity and the bulk-specific heat are higher in these varieties than in the older ones. It was also revealed that the length, width, thickness, and surface area did not change as the moisture was removed, whereas the bulk density, kernel density, mass, bulk- specific heat, and bulk thermal conductivity decreased as the moisture was reduced. Displaying better thermophysical properties will improve the drying and roasting pro- cesses; hence, a better final product can be expected from these varieties

Duque‐Dussán, E., Sanz‐Uribe, J. R., Dussán‐Lubert, C., & Banout, J. (2023). Thermophysical properties of parchment coffee: New Colombian varieties. Journal of Food Process Engineering, December 2022, 1–13. https://doi.org/10.1111/jfpe.14300

Different coffee drying technologies face complex tasks in ensuring an acceptable final seed moisture content. This research performed a Finite Element Analysis (FEA) study, simulating a single coffee bean's drying process as a transient mass diffusion model under mechanical and natural convection conditions, so the drying behavior and data of both case scenarios can be foreseen and controlled by a predictive Finite Element Model (FEM). A wet bean was 3D&-scanned and digitized as the FEA simulation geometry; the water diffusion between the grain and the atmosphere was defined by a diffusion coefficient subject to the drying air temperature and the grain's moisture content. Three cases were studied: mechanical grain drying at three different temperatures (50, 45, and 40°C) in a forced convection environment; variable natural convection drying under environmental conditions (wet and dry season); and constant natural convection (wet and dry season), including the variation in day/night temperature and relative humidity. The results agree well with the data found in the literature, obtaining the graphical moisture distribution of the phenomena, predictive drying curves, diffusion coefficients, and isotherms. Both simulated drying scenarios provide essential information for coffee growers to improve and control their drying processes, thus obtaining high-quality grains, reducing contamination by microorganisms, and ensuring the integrity of their products. 

 Duque-Dussán, E., Villada-Dussán, A., Roubík, H., & Banout, J. (2022). Modeling of Forced and Natural Convection Drying Process of a Coffee Seed. Journal of the ASABE, 65(5), 1061–1070. https://doi.org/10.13031/ja.15156

This study deals with the design of a pneumatic air-jet nozzle for coffee fruits harvesting purposes. In steady- state conditions, a CFD finite element model was implemented to validate the nozzle design. We studied variations in the cavity length and outlet diameter of the nozzle under 5 bar of pressure and 140 Lt/min of caudal flow. Using additive manufacturing, three prototypes of the nozzles were created in onyx material. In addition, a pneumatic assembly was built by integrating a nozzle with a solenoid electro valve that allowed air to be discharged from a compressor. Using a high-speed video camera, we conducted an experiment to understand the air jet morphometry of each nozzle. The electro valve was operated at 42 Hz and the operating conditions were chosen based on simulations. CFD- derived velocity was compared with the filmed jets from the experiments to illustrate its turbulence. The results were analyzed in terms of their capacity to produce punctual impacts on coffee fruits Coffea Arabica L. var Castillo. The results of this study suggest that future studies could be conducted to investigate the impact capacity of pneumatic air-jet nozzles on coffee fruit excitation in terms of vibrational measurements.

 Cardona, C. I., Tinoco, H. A., Perdomo-Hurtado, L., Duque-Dussan, E., & Banout, J. (2022). Computational Fluid Dynamics Modeling of a Pneumatic Air Jet Nozzle for an application in Coffee Fruit Harvesting. 2022 International Conference on Electrical, Computer and Energy Technologies (ICECET), July, 1–7. https://doi.org/10.1109/ICECET55527.2022.9872877