Toward natural convection solar drying of date palm fruits (Phoenix dactylifera L.): An experimental study

Abstract

AbstractSun‐drying has proven to be the most sustainable technique for preserving food and agricultural products. However, conventional sun‐drying has limited drying capacity and can lead to significant losses in product quality. Greenhouse and indirect solar drying are advanced drying methods with improved product quality. In this article, the natural convection greenhouse dryer and natural convection indirect solar dryer were developed to study date palm fruits' drying characteristics (Phoenix dactylifera L.) in terms of moisture ratio and convective heat transfer coefficients. At the same time, the thermal performance of drying units was examined in terms of energy efficiency. The greenhouse dryer's higher convective heat transfer coefficient reduced drying time, and the indirect solar dryer's energy efficiency was obtained. The experimental data were fitted in various drying models, of which the Lewis model was found to be best fitted. The experimental errors were analyzed in terms of percent uncertainties. The drying costs of dried date palm fruits under greenhouse dryer and indirect solar dryer were found to be INR ₹ 22.37/kg (US$ 0.30/kg) and INR ₹ 30.14/kg (US$ 0.40/kg), respectively. Drying units could be a sustainable way of product drying, particularly in the rural areas where advanced drying mechanisms are still unavailable (1 USD = 74.8 INR as on 03 Feb, 2022).