This study employed segmented variable-frequency ultrasound synergistic hot-air drying (SVFU-HAD) for slices, selected two sets of time nodes for frequency conversion (60 min, 120 min, and 90 min, 150 min), and two sequences of frequency conversion (high-frequency to low-frequency, and low-frequency to high-frequency). It aimed to investigate the effects of SVFU-HAD on the drying characteristics, quality, and heat transfer of slices. The findings indicated that segmented variable-frequency ultrasound has advantages in increasing drying rate and improving uniformity of cavitation effects compared to constant-frequency ultrasound. Analysis of physical properties revealed that the rehydration performance of dried products subjected to ultrasonic variable-frequency treatment (90 min, 150 min) according to the drying rate was better ( > 3.3). The transition mode from high-frequency to low-frequency in variable-frequency ultrasonic treatment contributes to maintaining the overall color of . Analysis of chemical properties unveiled that treated with 40 kHz (0 min)–28 kHz (60 min)–25 kHz (120 min) segmented variable-frequency ultrasound contained overall higher levels of tannins, dianthrones and free anthraquinones content, which exceeded the average values by 3.24%, 26.65%, and 14.42%, respectively. In addition, thermal analysis results based on ANSYS Workbench software demonstrated that the drying uniformity of SVFU-HAD is superior to that of hot-air drying and constant-frequency ultrasound synergistic hot-air drying (CFU-HAD). Overall, the SVFU-HAD method employed in this study presents an innovative approach to ultrasound synergistic hot-air drying research with promising potential for enhancing the efficiency and quality characteristics of slices.

中文翻译：

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大黄分段变频超声协同热风干燥对干燥特性和品质的影响及热分析


本研究采用分段变频超声协同热风干燥（SVFU-HAD）进行切片，选取两组时间节点进行变频（60 min、120 min、90 min、150 min），并选择两组频率序列转换（高频到低频，低频到高频）。旨在研究SVFU-HAD对切片干燥特性、质量和传热的影响。研究结果表明，分段变频超声与恒频超声相比，在提高干燥速率和改善空化效应均匀性方面具有优势。物理性能分析表明，根据干燥速率进行超声波变频处理（90 min、150 min）的干燥制品复水性能较好（>3.3）。变频超声波处理中从高频到低频的过渡方式有助于保持整体颜色。化学性质分析发现，经40kHz（0分钟）–28kHz（60分钟）–25kHz（120分钟）分段变频超声处理后，单宁、二蒽酮和游离蒽醌含量总体较高，超过平均水平值分别增加了 3.24%、26.65% 和 14.42%。此外，基于ANSYS Workbench软件的热分析结果表明，SVFU-HAD的干燥均匀性优于热风干燥和恒频超声协同热风干燥（CFU-HAD）。总体而言，本研究中采用的 SVFU-HAD 方法为超声协同热风干燥研究提供了一种创新方法，在提高切片的效率和质量特性方面具有广阔的潜力。