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

Abstract

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.

An Innovative Ultrasonic Apparatus and Technology for Diagnosis of Freeze-Drying Process

“…Figure 2c shows the bottom view of the apparatus. The UT is comprised of Pb(Zr x Ti 1−x )O 3 (PZT) material and integrated into the cavity of steel plate using the sol-gel spray technique, as described in previous publications [22,24,31]. The operational temperature range of the UT is between −100 and 400 °C.…”

“…The chamber pressure is measured by the pressure sensor or vacuum gauge. The measured chamber pressure value cannot directly indicate the physical variation of frozen product real-time during the freeze-drying process [20,22]. In this paper, an idea for diagnosing the physical property variations of a product in the frozen bottle to provide additional information for a machine system is presented, as shown in Figure 1.…”

“…Passot et al utilized ultrasonic technology to decrease the sublimation time during the primary drying stage by controlling the nucleation temperature [30]. The authors presented an innovatively designed frozen bottle with an ultrasonic transducer and ultrasonic technology to be utilized for the diagnosis of the freezing point during the frozen process in our previous paper [22]. In this study, the ultrasonic technique will be applied for real-time diagnosis of the freeze-drying process.…”

Diseño de una estrategia de control difuso aplicada al proceso de ultracongelación de alimentos

“…El procedimiento en cuestión, para una pieza de alimento de forma irregular, en un ambiente a temperatura constante representa una gran dificultad [11][12]. En la práctica, para tal fin se recurre a una serie de suposiciones que permitan obtener un modelo simplificado del proceso de congelación, el que se lleva a cabo en tres (3) etapas: preenfriamiento, congelación y atemperado o subenfriamiento [13][14] A pesar de que existen diversos métodos que se usan para determinar el tiempo de congelamiento [15][16][17], muchos de los estudios relacionados con la determinación de dicho parámetro hacen referencia principalmente a la ecuación desarrollada por Plank, que permite obtener rápidamente un estimado suficientemente preciso del referido tiempo para uso en ingeniería [3][4].…”

Freezing and Thawing of D2O/Sand Mixtures Investigated by Neutron Diffraction

“…Various models have been proposed and developed aimed at theoretical description of the complex processes accompanying ice grains nucleation, growth, and preferential orientation (texture) formation [3,[9][10][11]. Representative experimental data are then necessary to evaluate and further improve the theoretical models, requiring application of advanced experimental methods, such as X-ray diffraction and tomography [2,12], electron back-scatter diffraction [13], ultrasound waves dispersion [7,14], optical automatic ice texture analysis [2,4], helium spin-echo [15] and neutron diffraction and radiography [16][17][18].…”