The effects of geometrical changes on airflow of developing-world solar fruit dryers

Abstract

Small fruit-drying operations are becoming increasingly prevalent in the developing world. Many of these operations rely on solar thermal dryers with small fans to induce active air flow, which enhances drying capabilities. This thesis examines the effects of changes in dryer geometry on the air flow within flatbed solar dryers. The interior of a dryer was simulated using Ansys Fluent, and air flow velocity and patterns were observed as the dryer's length, width, and height were varied. It was found that a small fan placed at the dryer's entrance introduces a thin jet of air, which slows and spreads out over the course of the dryer. A steady air flow pattern was reached 4 meters into the modeled dryer. Reducing dryer height was found to increase the air flow velocity at the dryer's center, but not at the dryer's bottom where fruit is usually located. In addition to decreasing dryer height, the study recommends vertically raising the racks of fruit further above the dryer bottom. Air flow consistency across the width of the dryer persisted as an issue through the variations of width and height.