Experimental study of water freezing process improvement using ultrasound

Abstract

The phase change process of freezing water is an important application in several fields such as ice making, food freezing technologies, pharmaceuticals, etc. Due to the widespread usage of ice-related products, process improvements in this technology can potentially lead to substantial energy savings. It is well known that supercooling has a negative effect on the overall time and energy consumption of the freezing process. Therefore, ultrasound is proposed as a technique to improve the freezing process by eliminating the supercooling effect and the resulting energy savings is investigated. An experimental study was conducted to analyze the energy expenditures in the freezing process with and without the application of ultrasound. After a set of preliminary experiments, an intermittent application of ultrasound at 3.52 W & 8.25 W power levels was found to be more effective than constant-power application. The supercooling phenomenon was thoroughly studied through iterative experiments. It was also found that the application of ultrasound during the freezing process led to the formation of shard-like ice crystals. From the intermittent ultrasound experiments performed at 3.52 W & 8.25 W power levels, energy savings relative to no-ultrasound processes of 12.4% and 10.8% were observed, respectively.