ABSTRACT
Smart drying technology utilizes sensors to detect and monitor online various quality parameters of the material to proactively control and detect errors or deciencies in dryer operation. It incorporates equipment, technologies, resources, and practices to save energy and promote environmental sustainability, and thus control the dryer operating conditions to make high-value products.1-3 The monitored quality parameters generally include moisture content, color, shape, taste, and avor and the conditions within the dryer such as pressure, velocity, temperature, and humidity to control the performance of the drying system. Consequently, smart drying technology includes not only dryers but also smart sensors, translators, and smart control systems to monitor the operating conditions and to improve drying product quality as well as to enhance the energy efciency. Fresh food can be successfully manufactured into high-quality products through smart drying technology, which contains three parts: manufacturing process dryer, the probe, and online analysis. The probe monitors the drying process and sends messages for online analysis, which in turn controls the drying process according to the information received. The smart drying technology needs to be designed based on the knowledge of the specication of product being dried, such as local drying conditions and the quality parameters of the product after drying. Then the product quality is assured with optimal energy
6.1 Introduction .................................................................................................. 117 6.2 Categories of Smart Drying Technology ...................................................... 119
6.2.1 Biomimetic Systems ......................................................................... 119 6.2.2 Computer Vision Technology ........................................................... 122 6.2.3 Microwave Dielectric Spectroscopy .................................................124 6.2.4 Ultrasonic Techniques ...................................................................... 125 6.2.5 Control Systems for Smart Drying Environment ............................. 127
6.3 Closing Remarks ........................................................................................... 129 References .............................................................................................................. 129
consumption and minimal environmental impact. It is also worth mentioning that the quality of foodstuff should be examined during the whole process and not only at the end point. Therefore, all unit operations need to be monitored and controlled during the entire process using appropriate instruments to assure the quality of the end products.4 Drying is a complex, dynamic, nonlinear, uncertain, and often unpredictable operation because of simultaneous heat and mass transfer, potential for several physical transformations such as shrinkage, pufng, transformation, case-hardening, as well as potential for chemical and biochemical reactions.5 This complexity becomes more severe in the process of food drying because of product heterogeneity, anisotropicity, and nonuniformity of drying conditions.6 In recent years, with the rapid development of drying science and technology and designing of new equipment, the drying industry is making huge progress. However, the present drying technology has some disadvantages, such as limited application of smart automation, high energy and fuel consumption, etc. With the emergence of computer science in the early 1980s, computer-aided design was incorporated in many areas of science and engineering and in industrial drying.7,8 About two decades ago, Professor Mujumdar1-3 proposed the development of smart or intelligent dryers to make industrial drying more efcient and cost-effective. Because drying is a highly energy-intensive operation, which affects the quality of dried product decisively and also has an adverse effect on the environment through greenhouse gas emissions, it is necessary to make this a sustainable operation by utilizing the latest technologies including advanced computer hardware and software for reliable process control. With the recent advances in mathematical modeling of dryers and sophisticated sensors for real-time measurement of variables of interest in automatic control of dryers and robust control strategies, it is now feasible to design and operate smart dryers.
