Modeling of Hydrogen-Peroxide Films for Aseptic Processing Applications- A Parameter Study on Hydrogen-Peroxide Exposure to Internal Surfaces of mm-wide Slits

Examensarbete för masterexamen
Eriksson, Jesper
Disinfection methods are used within many fields to keep equipment and environments free from harmful biological agents such as fungi, bacteria, viruses and spore forms. Within the food and drug industry, aseptic processing refers to a process chain in which sterilized products are filled into sterilized containers. Aseptic processing brings benefits such as improved quality and increased shelf life of a product, which in turn leads to less waste due to the expiration of products. The benefits of aseptic processing introduce a demand for the development of effective disinfection methods. A common chemical disinfection method is the usage of hydrogen-peroxide to kill bacteria. One way to perform hydrogen-peroxide disinfection is to spray a vapor containing air, water and hydrogen-peroxide which is allowed to condense on cold surfaces forming a liquid film of water and hydrogen-peroxide which conducts the desired bacteria killing. It is important that all surfaces have been exposed to a hydrogen-peroxide film to ensure a rapid disinfection. This project aims to investigate the process of hydrogen-peroxide film condensation to evaluate the degree of liquid film coverage and gas hydrogen-peroxide exposure within mm-wide slits. The investigation was carried out using Computational Fluid Dynamics (CFD). The process of hydrogen-peroxide gas disinfection is well understood, but the process of liquid film formation and dynamics is more complex and many challenges remain within this field. In particular, there are no previous studies investigating film formation within small slits. A parameter study was performed to evaluate how the characteristic width of a slit h and the external gas flow velocity v influence the degree of liquid film coverage on the inside surfaces of a slit. The results suggest that the critical value of h as a function of v to ensure full surface film coverage follow hcrit(v) = 6.44v−0.2838−1.84, which is valid within the range v = [0.5, 2.0]. Expressed in terms of the dimensionless mass transfer Péclet number Peh, the criteria for full surface film coverage is according to the results Peh > 97. The results remove the need of having a high spatial resolution around mm-narrow spaces. Instead the developed macro-scale model can be used to predict the degree of hydrogen-peroxide exposure within the slit only with the knowledge of gas velocity external to the slit.
hydrogen-peroxide, aseptic, disinfection, film, condensation, model, dropwise, CFD, slit
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