Echanncement of Thermal Efficiency in Solar Dryer by Application of Composite Phase Change Materials for Thermal Energy Storage : Case Study of Longan Drying in Ban Tha Kloy, Tha Takiab District, Chachoengsao Province

Abstract

          This research focuses on enhancing thermal efficiency in solar drying machines by applying phase change composite materials as heat storage. The case study involves longan drying in Ban Tha Kloi, Tha Takiap District, Chachoengsao Province. The objectives are: 1) to study the thermal and chemical properties suitable for developing phase change composite materials to serve as heat storage in the solar drying machine, 2) to design and construct a solar drying machine using phase change composite materials, and 3) to examine the quality of dried longan and analyze the efficiency of the drying process using the solar drying machine combined with phase change composite materials. A sample of 30 volunteers from the Ban Tha Kloi community, including village leaders, members, and interested individuals, was selected to participate as representatives for knowledge transfer regarding the developed solar drying machine. Data were collected through open-ended interviews to gather physical, social, and production-related information and analyzed using percentages, averages, and standard deviations. The results revealed that the phase change composite materials consisting of paraffin and volcanic rock in a 2:1 ratio were most suitable, with a melting point of 79.9°C and latent heat of 89.6 J/g. The use of phase change composite materials maintained an average drying temperature of 40–50°C, reducing drying time to 16 hours, which was 6 hours less than without phase change composite materials, improving efficiency by 73%. The dried longan exhibited higher red (a*) and yellow (b*) color values compared to commercially available products, with 86% shrinkage and water activity below 0.6, meeting standard requirements. This study demonstrates that integrating phase change composite materials in solar drying machines significantly enhances efficiency and product quality, providing a practical and scalable solution for local agricultural processing.