Mathematical modeling and analysis of the interaction of parameters in the clean-in-place procedure during the pre-rinsing stage

Abstract

Cleaning procedures in the Clean-in-Place system are the subject of many authors’ research. The paper presents the dependence of the effect of removing milk impurities from the plate heat exchanger on the parameters adopted in the Cleaning in Place procedure at the stage of preliminary rinsing. The study was carried out at the laboratory cleaning station, where the plate heat exchanger contaminated with hot milk was included in the system. The research program was developed according to a 5-level statistical plan, in which process variables were water temperature, flow rate and cleaning process time. The observed variable was the cleanliness of the exchanger plates surface evaluated after the completed process. The obtained results were subjected to statistical analysis. Standard deviations of the cleaning effect with respect to the obtained averages were determined for the central points of the research plan and Tukey’s test of multiple comparisons was performed to identify the significance of individual process variables for the final cleanliness of the exchanger plates. On the basis of the scatter curves, the nature of the influence of individual independent variables on the cleaning effect in the form of partial functions was determined, which formed the basis for the development of a prediction model, in the form of non-linear regression C = f (t,T,vPHE). The developed model is a mathematical description of the process of cleaning out milk deposits from a plate heat exchanger in the Cleaning in Place system. Numerical calculations were carried out on the basis of a non-linear method of the smallest squares using the Gauss-Newton algorithm. Finally, the response area of the dependence between the analyzed variables was determined. The results showed that the cleaning effect depends mainly on the temperature of the cleaning agent and its rate of flow through the cleaned element. On the other hand, the prolongation of plate heat exchanger cleaning time favorably influences the cleaning effect only in interaction with low values of flow rate. Statistical analysis demonstrated that preliminary rinsing of heat exchangers contaminated with milk is best carried out at the temperature of 40÷50°C, at the highest possible flow rate, while decreasing the flow rate, the cleaning time should be extended.