Experimental and numerical study of a natural convection indirect solar dryer with PCM tubes: Dynamic, thermal and nutritional quality analysis

Abstract

A natural convection solar dryer was investigated in this paper with a storage unit in the form of copper tubes filled with Paraffin wax as a PCM, experimentally and numerically using the ANSYS Fluent software. The storage unit was placed in a side-mounted plenum chamber for air uniformity and heat recovery. The validations made for the drying chamber’s temperature with and without storage, the outlet air temperature, and velocity of the SAH, show good accordance with the experimental results, which promote the use of this method in investigating the solar dryer numerically. The drying of orange slices in different modes were studied; open sun drying, in a solar dryer with and without PCM. The drying time required to reduce the moisture content from 81.19% (wb) to 19% (wb) was respectively 216 h, 144 h, and 168 h. In terms of the quality of orange slices, the open sun drying showed the poorest quality in terms of color, texture, shape, and odor. However, all these properties were enhanced with the solar dryer, particularly with the use of PCM tubes. The most valuable nutritional value of oranges is vitamin C, which was measured per slice in all mentioned cases. One fresh orange slice contains 11.34 mg of vitamin C, while it contains 7.77 mg, 7.34 mg, and 5.99 mg in the drying cases with and without PCM as well as in open sun drying respectively.