CFD analysis of primary and secondary flows and PIV measurements in whirlpool and whirlpool kettle with pulsatile filling: Analysis of the flow in a swirl separator

Rheological Properties of Industrial Hot Trub

The boiling of beer wort with hops results in the formation of a hot trub, a sediment consisting mainly of water-insoluble tannin and protein conglomerates and hop residue. Hot trub is a waste product, removed in a clarifying tank and discarded. The use of barley malt substitutes in recipes for beer is associated with an increase in the amount of generated hot trub. In presented study, an analysis of the rheological properties of industrial hot trub was carried out. Samples varied with regard to the quantities of unmalted barley (0%, 35%, and 45%) and worts’ extract (12.5, 14.1, 16.1, and 18.2 °Plato) in the recipe. The rheology of each type of sludge was determined using a hysteresis loop at four different temperatures. The results showed the shear-thinning and thixotropic properties of the hot trub. It was found that, regardless of the raw material and extract used, all samples exhibited the same rheological properties, but with different values. It was also proved that both raw material composition and temperature affected the hot trub’s rheology. The highest values of viscosity were identified for malted barley, whereas the lowest apparent viscosity values were recorded for the hot trub with a 30% addition of unmalted barley. The Herschel–Bulkley model had the best fit to the experimental data.

A novel micro-spiral pneumatic selection system for the separation of fresh tea leaves

There are no standard machines or systems used for grading the new tea leaves in the market, a micro-spiral pneumatic selection system was designed to separate fresh tea leaves, solving the difficulties in tea leaf selecting and separation. The system can flexibly separate the tea leaves continuously in high quality. And the simulation model was established based on the experiments results to optimize the design parameters. The maximum constant air flow rate separation tests showed that the symmetrical distribution effect of six tubular fans provided better balance than four tubular fans, and three grades of fresh tea can be differentially sorted. Additionally, solid particle simulation tests showed that separation begins at heights between 0.27 and 0.37 m. When the air flow rates range from 4.4 to 6.6 m/s, fresh tea leaves containing only one leaf per stem are well separated from multi-leaf containing stems. Furthermore, solid particle simulation tests indicated that different sizes of fresh tea leaves can be distributed in corresponding annular regions of specific widths; therefore, the flow field simulation tests showed that an optimized system could separate tea leaves according to the number of leaves on the stem. To sum, this study reported a novel micro-spiral pneumatic selection system with high efficiency for the separation of fresh tea leaves.

Study on critical speed of vortex rupture and gas-liquid two-phase flow in rotating soybean milk machine

The gas-liquid two-phase flow field inside a soybean milk machine is simulated with the Navier–Stokes equations, Renormalization group (RNG) k-ɛ turbulence model and the particle two-phase flow model. The critical speed of vortex breakdown in the container and the influence of the characteristics of the two-phase flow on the soybean crushing effect at different speeds are investigated. The results show that there is a critical value of rotating speed of 1500 rpm for the vortex breakdown in the studied machine. At this rotational speed, the turbulent eddy dissipation (TED) reaches the maximum, and the position where the vortex first rupture is near the central axis and with a distance of 0.01 m from the central axis. It is also found that with the increase of rotating speed, the pressure difference around the blade varies significantly. The research in this study has important implication for the design of the soybean milk machine.

Mathematical modeling of ohmic heating for inactivation of acid-adapted foodborne pathogens in tomato juice

The objective of the present study was to predict the inactivation trends of acid-adapted foodborne pathogens in tomato juice by ohmic heating through a numerical analysis method. The mathematical model based on finite element method (FEM) was used to simulate the multiphysics phenomena including electric heating, heat transfer, fluid dynamics, and pathogen inactivation. A cold spot was observed in the corner part of the ohmic heating chamber, where some pathogens survived even though all pathogens were inactivated elsewhere. Challenges of this study were how to reflect the increased resistance of pathogen by acid-adaptation. After simulation, we verified that inactivation level of acid-adapted foodborne pathogens by 25 Vrms/cm ohmic heating (1 kHz), predicted with the developed mathematical model, had no significant differences with experimental results (p > 0.05). Therefore, the mathematical approaches described in the present study will help juice processors determine the processing conditions necessary to ensure microbial safety at the cold point of a rectangular type batch ohmic heater.