Abstract
A transient mathematical model has been evaluated to determine the principle of a solar crop dryer for drying vegetables (onion). Considering the meteorological conditions of Freetown (Latitude 8.4840 N, Longitude -13.2300 W), the model was developed to determine air temperatures and other operational parameters of the drying system for a day of March 21st. However, the investigated system had effectively reduced the drying process of onion. The developed double-pass solar air collector system showed a low-temperature output in the morning hours and displayed high-temperature results in the afternoon hours. From 8:00 to 16:00, the solar collector generates fluid output temperatures above 50 0 C, with a peak value of 96 0 C occurred at 12:00. The influence of the mass flow rate on the system's thermal efficiency was investigated. It was noticed that for a certain solar radiation value, an increased in the mass flow rate caused an exponential increased in the solar air collector thermal efficiency. Findings also revealed that an increased in the solar collector length led to a slightly decreased in the outlet air temperatures at a mass flow rate of 0.02 kg/s. The influence of increasing drying air temperatures and air velocity within the drying chamber reduces drying time significantly. The drying time for products dried in the first tray is lesser than for products dried in the subsequent trays, owing to temperature variations. The computation findings were verified to previous studies in the literature and observed to be strongly comparable.
Highlights
Fruits and vegetables remain extremely frequent, with significant quantities produced at specific times of the year [1]
We developed equations for both the solar air heater and the drying chamber and used them to simulate our dryer numerically
For certain sets of operational parameters, a theoretical approach was employed to compute the thermal efficiency of the double-pass solar air heater
Summary
Fruits and vegetables remain extremely frequent, with significant quantities produced at specific times of the year [1]. The surplus could result in the deterioration of significant quantities due to abundant production during the harvest. Preserving these fruits and vegetables will help minimize food waste and make foods more accessible during the off-season [2]. Drying is the oldest method of preserving agricultural products It is a time-consuming and energy-intensive operation. High temperature on the other hand, degrade the consistency of heat-sensitive items like food and pharmaceuticals. In this case, using the desiccant method, low-temperature and high-humidity drying is needed to preserve the product's fresh color [8,9].
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