Hybrid System Simulation to Supply Heated Air to a Solar Food Dryer

Abstract

The intermittence of solar radiation, due to continuous rainy or cloudy days, is a limitation of simple and small solar dryers. These conditions often make them impossible to use. By including storage systems (thermal accumulation) and/or auxiliary energy sources, drying processes or dehydration can be conducted continuously, even during periods of low insolation. Therefore, the present work simulates and evaluates the thermal and energetic behavior of a hybrid system for heating the air that is directed to the dehydration chamber of a solar food dryer. The software selected for the simulation was TRNSYS. The simulated hybrid system consists of a flat plate solar collector and an arrangement of electrical resistors that guarantee the entry of air, at a constant temperature, into the dehydration chamber. The target temperature selected is 70 o C, and the absence of food products in the chamber is assumed. An arrangement with four electric resistors totaling 1900 W, with three different powers of 1000 W, 500 W, and 200 W proved adequate to guarantee the entrance of air at a constant temperature when considering the climatic conditions of a city in the South of Brazil.

A Review on Solar Drying Devices: Heat Transfer, Air Movement and Type of Chambers

“…Despite their effectiveness, their availability is limited, and they are associated with environmental pollution issues. Amer and Gottschalk [139] used electric resistances as auxiliary units in fresh chamomile drying; Matouk et al [140] used them for onion slices; and Hossain et al [141] used them for tomato slices [142]. Ferreira et al [143] applied 20 incandescent lamps, 100 W each, for drying banana slices.…”

A Review on Possible Combination of Solar Dryer Materials for Crops in the Philippines

“…The study shows that in using double pass flat plate, efficiency is 2% lower than in using double pass v-groove collector. A flat plate solar accumulator is also utilized by [10] to evaluate and simulate the solar hybrid dryer's energetic and thermal behavior in heating the air inlet into the drying chamber.…”

“…Most research focused on maximizing the heat gathered inside the drying equipment, setting aside the condition that there is a constant change in weather or season (dry and wet), resulting in shrinking of products or over-drying during the dry season and raw drying during the wet season. Moreover, intermittent drying condition does not allow solar dryers' continuous function, resulting in incomplete dehydration and unsatisfactory product quality [10] [11]. Thus, a variety of published journals studied the optimization of the solar dryer, taking into account its effectivity during night and off sunshine [12], concentrating on the modelling [13] [14], simulation [15], and experimentation [16].…”