Experimental design of drying kinetics measurements

This work deals with the study of the drying kinetics of bread cubes that are further sold as a dried food product. The cubes are dried in an industrial plant which, in order to optimise production from an energy point of view, is modernising its operation in three ways:
1. Integration of a heat pump to recover energy from the exhaust air.
2. Continuous monitoring of the product moisture content using a non-contact infrared sensor.
3. Experimental study of product drying kinetics
The master thesis focuses only on experimental research, which is important, for example, from the point of view of heat pump integration, where it can be assumed that the process parameters can be changed to those more suitable for the heat pump, i.e., increasing the temperature and water content of the exhaust air. The experimental study helps to predict the effect of changing the process conditions on the product. The use of a product moisture sensor helps to make good use of the known kinetics by providing information on the actual moisture content of the product.
Drying kinetics is evaluated with respect to temperature, flow velocity and humidity of the drying air using a characteristic drying curve approach which is material specific and independent of drying conditions as long as they are constant. This universal curve can be further used to predict the drying rate under different conditions. The work includes the design of a prototype laboratory drying oven to measure drying kinetics using continuous gravimetric measurement. This apparatus is designed to provide stable and reproducible drying conditions, while it is necessary to deal with the actual fixation of the sample in the drying chamber. The experimental and theoretical part was carried out at AIT - Austrian Institute of Technology GmbH in cooperation with the Faculty of Chemical and Food Technology of the Slovak University of Technology in Bratislava.