Abstract
In the food industry, the efficient production of high quality products leads to increased investigation efforts in the production process. High shear rates, improper heat transfer during the production process can lead to low quality products. In many cases the produced food preparation contains additives e.g. pectin and starch, which are affecting the products flow behaviour especially at lower temperatures. High shear rates during the production can be observed rather during the cooling and mixing processes of these products. The goal of this paper is to develop a CFD solver in the open source software OpenFOAM® which will be able to recognise the weak spots of the production. For this purpose, a detailed analysis of the material properties was completed with the help of measurements. In the food industry, the average volume of a produced batch is up to 1,000 L. To speed up the development of the CFD code a model production process was set up in small scale using a 10 L stainless steel vessel with a simple mixer blade and heating/cooling jacket. The temperature of the medium inside the vessel was measured at various points. The torque of the shaft of the rotor blade was also measured during the production time. Using these measurement results the CFD computation could be validated. For the computed medium a shear rate and temperature dependent viscosity and a temperature dependent heat capacity, thermal conductivity and density model was created. To calculate the mixing during the process, dynamic mesh using the AMI concept was applied. The industrial cooling processes takes up to 30 min, but considering the inefficient mixer blade and the weak cooling power the cooling time at small scale usually takes more time. Because of the high computational need and relatively small time steps the simulation was calculated only for 25 min real time. The data of the installed PT 100 temperature sensors and the measured torque showed a close agreement with the simulation results.
