Performance evaluation of improved indirect flat-plate solar collector drier with integrated phase change material for drying kiwifruit (Actinidia deliciosa A. chev.)

Abstract

This study presents an innovative approach to enhancing the drying process of kiwifruit (Actinidia deliciosa A. Chev.) by integrating a phase change material (PCM) into a flat-plate solar dryer (FPSD^PCM). The research is motivated by the inefficiencies of conventional solar drying methods, which frequently result in prolonged drying times, inconsistent temperature control, and diminished product quality. The proposed system incorporates paraffin wax PCM and a flat-plate solar collector connected to a drying chamber with a 20 kg capacity. This design achieves a 10 ± 0.3% increase in thermal efficiency and a 38 ± 3.1% reduction in drying time compared to traditional solar dryers. The study's novelty lies in its innovative strategy to enhance drying performance while preserving the bioactive components of kiwifruit. Dried samples exhibited higher antioxidant activity, total phenolic content, and total flavonoid content compared to both fresh and open-sun-dried samples. Among five evaluated drying kinetic models, the Modified Henderson and Pabis model provided the most accurate predictions of the moisture ratio, as validated by statistical metrics including root mean square error (RMSE) and chi-square (X²) values. Operating within a temperature range of 44–73 °C, the FPSD^PCM reduced the moisture content of kiwifruit from 93 ± 2% to 11 ± 0.5% in 5.5 h, compared to 8 h using open sun drying (OSD). Despite these advancements, limitations such as PCM selection and experimental uncertainty (32.83%) remain. Future research should focus on exploring alternative PCMs, real-time monitoring systems, and life-cycle assessments for broader agricultural applications. With an experimental uncertainty of 32.83%, the FPSD^PCM offers a cost-effective, energy-efficient, and sustainable solution for small-scale farmers. It significantly improves drying efficiency and product quality, supporting environmentally sustainable agricultural practices.