Sensors for contactless estimation of ice concentration in "ice slurry" fluids

This paper deals with the problem of estimating the ice fraction in ice slurry fluids flowing into the pipes of industrial refrigeration apparatus based on secondary refrigerants. Such measurements must be performed in a non invasive way and the sensors must face with severe environmental conditions. Two different sensors have been developed and are presented here. In particular, an optical sensor is presented that relates the transmission of signals with the ice density, while a capacitive sensor is proposed as well exploiting the effects of ice particles concentration on the ice slurry fluid permittivity. Experimental prototypes have been realized for each one of the sensors proposed here. These sensors have been applied to an experimental refrigeration system that allows obtaining different percentage of ice in a controlled and reproducible manner. The experimental results obtained for each one of the sensors are reported showing the suitability of the approach. Some conclusive remarks are also given in order to compare the sensor performances.