Tseng Yen-Hsiang, Cheng Chin-Chi, Cheng Hong-Ping, Lee Dasheng
Department of Energy and Refrigerating Air-Conditioning Engineering, National Taipei University of Technology, Taipei 10608, Taiwan.
Sensors (Basel). 2015 May 4;15(5):10332-49. doi: 10.3390/s150510332.
The freezing stage governs several critical parameters of the freeze drying process and the quality of the resulting lyophilized products. This paper presents an integrated ultrasonic transducer (UT) in a stainless steel bottle and its application to real-time diagnostics of the water freezing process. The sensor was directly deposited onto the stainless steel bottle using a sol-gel spray technique. It could operate at temperature range from -100 to 400 °C and uses an ultrasonic pulse-echo technique. The progression of the freezing process, including water-in, freezing point and final phase change of water, were all clearly observed using ultrasound. The ultrasonic signals could indicate the three stages of the freezing process and evaluate the cooling and freezing periods under various processing conditions. The temperature was also adopted for evaluating the cooling and freezing periods. These periods increased with water volume and decreased with shelf temperature (i.e., speed of freezing). This study demonstrates the effectiveness of the ultrasonic sensor and technology for diagnosing and optimizing the process of water freezing to save energy.
冷冻阶段控制着冷冻干燥过程的几个关键参数以及所得冻干产品的质量。本文介绍了一种集成在不锈钢瓶中的超声换能器（UT）及其在水冷冻过程实时诊断中的应用。该传感器通过溶胶 - 凝胶喷涂技术直接沉积在不锈钢瓶上。它可以在 -100至400°C的温度范围内运行，并采用超声脉冲回波技术。使用超声波可以清楚地观察到冷冻过程的进展，包括进水、冰点和水的最终相变。超声信号可以指示冷冻过程的三个阶段，并评估各种加工条件下的冷却和冷冻时间。温度也被用于评估冷却和冷冻时间。这些时间随着水量的增加而增加，随着搁板温度（即冷冻速度）的降低而减少。本研究证明了超声传感器和技术在诊断和优化水冷冻过程以节省能源方面的有效性。
