Abstract
Solar drying using greenhouse dryers is a viable method from the technical, economic, and environmental perspectives, allowing the drying of agricultural products for conservation purposes in different regions of the world. In Colombia, the drying of aromatic plants such as mint (Mentha spicata) is usually done directly and in open fields, which exposes the product to contamination and loss of quality. Therefore, the objective of this research was to use a three-dimensional computational fluid dynamics (CFD-3D) model previously successfully validated and implemented in this work to study the performance of air flow patterns, temperature, and humidity inside four greenhouse-type dryers contemplated for a region with hot and humid climatic conditions. The results found allowed us to observe that the spatial distribution of temperature and relative humidity are related to the air flows generated inside each dryer, therefore, there were differences of up to 7.91 °C and 23.81% for the same evaluated scenario. The study also allowed us to conclude that the CFD methodology is an agile and precise tool that allows us to evaluate prototypes that have not been built to real scale, which allows us to generate useful information for decision-making regarding the best prototype to build under a specific climate condition.
Highlights
Solar drying is one of the oldest existing conditioning operations for the processing and conservation of food, species, and medicinal plants
For the Model 2 (M2), model 3 (M3), and model 4 (M4) dryers, it was found that the lowest temperature values were obtained, just in the area near the ventilation surface where the air flow from the outside enters. This flow of air as it moves through the interior of the dryer drags the heat towards the leeward wall where the highest values of temperature obtained in these three dryers can be observed, this situation is similar to the results found for greenhouse type solar dryers developed by Gupta et al [57] and Purusothaman and Valarmathi [58]
The computational fluid dynamics (CFD) model, previously validated, used in this research was efficient to determine the performance of the main variables that influence the process of solar drying of aromatic plants for four different types of dryer, without the need to perform the physical experiment, which could generate a high economic cost and obtain results in a longer period
Summary
Solar drying is one of the oldest existing conditioning operations for the processing and conservation of food, species, and medicinal plants. Its use is very popular in many regions worldwide mainly because it requires a low economic investment to carry out the drying process [1,2] This activity in the last two decades has been even more relevant due to the growth of the world population, which has caused food production systems to become more efficient and reduce post-harvest losses [3]. A common practice is to dry products in yards with free exposition during the hours of sunshine and high radiation This method has several disadvantages, among which we can mention the dependence of the drying time on the climatic conditions of the region and the exposure of the product to dust, birds, pests, and other external agents that can generate losses, contamination, and even the presence of toxins in the final product [1,6]. One of the drying alternatives that can limit some of these disadvantages mentioned, is drying using greenhouse type dryers, which is a method that has been used and is popular in many countries of the world [7,8]
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