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Sensors 2015, 15(5), 10332-10349; doi:10.3390/s150510332

Novel Real-Time Diagnosis of the Freezing Process Using an Ultrasonic Transducer

Department of Energy and Refrigerating Air-Conditioning Engineering, National Taipei University of Technology, Taipei 10608, Taiwan
Author to whom correspondence should be addressed.
Academic Editor: Vittorio M.N. Passaro
Received: 21 March 2015 / Revised: 24 April 2015 / Accepted: 27 April 2015 / Published: 4 May 2015
(This article belongs to the Section Physical Sensors)
View Full-Text   |   Download PDF [1759 KB, uploaded 4 May 2015]   |  


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. View Full-Text
Keywords: freezing point; freezing process diagnosis; ultrasonic transducer (UT); cooling/freezing periods freezing point; freezing process diagnosis; ultrasonic transducer (UT); cooling/freezing periods

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Tseng, Y.-H.; Cheng, C.-C.; Cheng, H.-P.; Lee, D. Novel Real-Time Diagnosis of the Freezing Process Using an Ultrasonic Transducer. Sensors 2015, 15, 10332-10349.

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