Experimental investigation of heat transfer for hot water shower sterilization of bags and bottles

Hot water shower sterilization is a crucial part in the production of liquid pharmaceutical products. This work was conducted to experimentally investigate the heat transfer for hot water shower sterilizers by examining the effects of various parameter changes. Heating and cooling runs were performed using a lab-scale test bench for a 1000 ml glass bottle and 500 ml flexible polypropylene infusion bag. The temperature range under investigation spanned from 20 °C to 80 °C, covering a significant portion of the range for heating and cooling of the sterilization process as well as typical temperatures used in food pasteurization. Temperature measurements were taken at three distinct locations within the products. High-speed and infrared photography was employed to explore the varying film regimes on the products. The results indicated that increasing the surface-averaged volume flow rate from 20 m³ h^-1 to 40 m³ h^-1 per m² of spraying surface reduced the cooling and heating rates for the bag. However, increasing the surface-averaged volume flow rate correlated to an increase in cooling and heating rates for the bottle. Additionally, configuring a distribution tray above the products with a greater number of smaller holes resulted in reduced sensitivity of the surface-averaged volume flow rate on the cooling rates and an overall decrease in cooling time. A higher hole plate porosity was identified to increase the heating rate of bags. In summary, this study offers valuable insights into how various parameter changes impact the heat transfer in bottles and bags during hot water shower sterilization.