A review of factors affecting the efficiency of clean-in-place procedures in closed processing systems

This paper reviews the current state of researches on improvement of Clean-In-Place (CIP) procedures in closed processing system thus saving energy, with a special attention paid to the hydrodynamic effects of cleaning fluid and the numerical and experimental approaches to investigate the identified controlling factors. The paper discussed the fouling problems of processing plants and the importance of sufficient CIP procedures, the forces contributing to cleaning with a special focus on the hydrodynamic effects. In general, it is possible to enhance hydrodynamic removal forces by local introduction of, among others, high wall shear stress and fluctuation rate of wall shear stress without consuming more energy. A theoretical model of particle removal in flow was also reviewed which supports the factors identified. The paper therefore further reviewed and compared the current state of modelling and experimental techniques on CIP improvement. To simulation the CIP process, it is necessary to consider 3D time-resolved Large Eddy Simulation with a Hybrid RANS-LES WMLES as Sub-Grid-Scale model because it captures both the mean and fluctuation rate of flow variables, while affordable for industrial flows. The wall shear stress measurement techniques and cleanablity test methods were also discussed and suggested.