Development of a microchannel based pasteurizer for energy efficient processing of liquids

This study focuses on the development of an energy efficient small-scale pasteurizer for processing liquids having biological contamination. The device has three sections that perform vital functions in the pasteurization process. The first is a microchannel counterflow heat exchanger for the recovery of thermal energy in the outgoing flow to heat the incoming flow. The second section also uses microchannels along with cartridge heaters to bring the preheated flow to approximately 150 °C. The third section is a residence chamber that ensures the flow remains at approximately 150 °C for at least 2 s satisfying the requirements for Ultra High Temperature (UHT) pasteurization. The integrated compact device has a characteristic channel height of less than 0.2 mm and was composed of chemically etched and diffusion bonded stainless steel shims. The design was improved with CFD modeling with validation from point measurements of the internal fluid temperature. Thermal and biological testing demonstrated successful operation; the heat exchanger effectiveness was shown to be more than 90% and samples collected showed no colony-forming bacteria at the design conditions of UHT pasteurization and 100 mL/min flow.