Hot air and solar drying are among the most popular preservation methods for fresh fruits. Ultrasonic technology could enable a faster dehydration rate at low temperatures, hence, preserving vitamins and nutrients in fruits. In this work, the application of ultrasonic vibration to pineapple drying was investigated. Experiments were conducted in hot air as well as direct solar dryers. The temperature in the hot air dryer was controlled at 60 °C, with an applied vibration frequency of 40 kHz. Three cycles of 10, 20, and 30 min with 1 min ultrasonic operation per interval were tested. The results showed that for the cycle of 10 min with 1 min vibration applied, the moisture content of pineapple slices was decreased from 87 to <13.7 %wb at a maximum evaporation rate of 49 g/h. Similar tests in the solar dryer proved to reduce the drying time from 3 to 2 days, with an increased evaporation rate of 10.6 g/h. Minimum specific energy consumption was realized by applying 1 min of ultrasonic vibration in a 10 min cycle with the solar dryer.

Maximum thermal efficiency of over 63% was achieved with ultrasonic assisted solar drying.

热风和太阳能干燥是最流行的新鲜水果保鲜方法之一。超声波技术可以在低温下加快脱水速度，从而保留水果中的维生素和营养成分。在这项工作中，研究了超声波振动在菠萝干燥中的应用。实验在热空气以及直接太阳能干燥器中进行。热风干燥器的温度控制在 60 °C，施加的振动频率为 40 kHz。测试了 10、20 和 30 分钟的三个循环，每个间隔 1 分钟的超声波操作。结果表明，在施加 1 分钟振动的 10 分钟循环中，菠萝片的水分含量从 87 下降到 <13.7 %wb，最大蒸发速率为 49 g/h。在太阳能干燥器中进行的类似测试证明，干燥时间从 3 天减少到 2 天，蒸发速率提高了 10.6 g/h。通过使用太阳能干燥器在 10 分钟的循环中施加 1 分钟的超声波振动，实现了最小的比能量消耗。

使用超声波辅助太阳能干燥实现了超过 63% 的最大热效率。