Performance evaluation and CFD investigation of scraped surface ice cream freezer augmented with LN₂ freezing technique

Ice cream is a frozen mixture comprising milk, cream, sugar, milk solids-not-fat, stabilizers, and emulsifiers. This study explores the production of ice cream using a Scraped Surface Freezer (SSF) combined with a liquid nitrogen (LN2) freezing technique. The innovative approach involves utilizing liquid nitrogen as a refrigerant and employing gaseous nitrogen released during heat transfer to control the overrun in the final ice cream product. The experimental investigation of SSF involved examining the draw temperature of ice cream and determining its overall heat transfer coefficient. The drawing temperature of -6 degrees C and overall heat transfer coefficient close to 300 W/(m(2)degrees C) was obtained after the process optimization. To better understand what occurs inside SSF, numerical simulation using ANSYS Fluent was used to acquire the flow parameters such as temperature, pressure, and velocity. The flow profile was obtained under the reference operating conditions: feed flow rate = 240 lit/hr, LN2 temperature = -95 degrees C, and scraper speed =125 rpm. The computational Fluid Dynamics (CFD) results reveal confined flow between blades and the inner heat transfer tube surface, causing a directional velocity change. Due to this recirculation, a faster decrease in temperature was observed in this area. The results of the experimental investigation of the SSF were rigorously compared with the CFD results. Based on numerical simulations, the initial freezing point in SSF occurred at an axial distance of 0.2 m.