In this study, a novel adaptive solar dryer with a coating of polymer-dispersed liquid crystals (PDLC) was designed, built, and characterized to evaluate its optical properties and thermal performance by modulating the transmission of solar radiation toward the drying chamber. PDLC films can electrically switch between opaque and transparent states, making them ideal for controlling solar radiation. Unlike conventional direct dryers, the proposed solar drying system takes advantage of direct solar radiation, known for its rapid drying process, while minimizing the impact on product properties. The results show that the PDLC coating exhibited a significant difference in transmittance between the “on” and “off” states under ambient conditions. At 400 nm, the transmittance varied by 20 %, increasing to 30 % at 450 nm. The solar dryer with dynamic control of solar irradiance constantly maintained a temperature range of 52.19 °C–57 °C. Lower relative humidity values were achieved compared to the uncontrolled solar dryer, resulting in a uniform irradiance distribution within the drying cabinet. The solar dryer with dynamic control of solar irradiance (acrylic and PDLC film) presents a total thermal resistance (0.02817 mK/W) exhibiting better heat permanence inside the drying cabinet compared to polycarbonate (one of the materials most used for drying systems). The system's thermal efficiency ensures reliable operation regardless of weather conditions, efficiently capturing and converting solar energy into heat.

中文翻译：

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动态控制太阳辐射的新型太阳能干燥机的光学特性和热性能


在这项研究中，设计、建造了一种带有聚合物分散液晶 (PDLC) 涂层的新型自适应太阳能干燥器，并对其进行了表征，通过调节太阳辐射向干燥室的传输来评估其光学性能和热性能。 PDLC 薄膜可以在不透明和透明状态之间进行电切换，使其成为控制太阳辐射的理想选择。与传统的直接干燥机不同，所提出的太阳能干燥系统利用直接太阳辐射，以其快速干燥过程而闻名，同时最大限度地减少对产品性能的影响。结果表明，在环境条件下，PDLC涂层在“开”和“关”状态下的透光率表现出显着差异。在 400 nm 处，透射率变化了 20%，在 450 nm 处增加到 30%。动态控制太阳辐照度的太阳能干燥机始终将温度保持在 52.19 °C–57 °C 范围内。与不受控制的太阳能干燥机相比，实现了较低的相对湿度值，从而在干燥柜内实现均匀的辐照度分布。具有太阳辐照度动态控制功能的太阳能干燥机（丙烯酸和 PDLC 薄膜）具有总热阻 (0.02817 mK/W)，与聚碳酸酯（干燥系统最常用的材料之一）相比，在干燥柜内表现出更好的耐热性。该系统的热效率确保无论天气条件如何都能可靠运行，有效捕获太阳能并将其转化为热量。