Thermo-fluid dynamics and synergistic enhancement of heat transfer by interaction between Taylor-Couette flow and heat convection.

This study experimentally and numerically investigated the thermo-fluid dynamics of Taylor-Couette flow with an axial temperature gradient from the chemical engineering perspective. A Taylor-Couette apparatus with a jacket vertically divided into two parts was used in the experiments. Based on the flow visualization and temperature measurement for glycerol aqueous solutions with various concentrations, the flow pattern was classified into six modes: heat convection dominant mode (Case I), heat convection-Taylor vortex flow alternate mode (Case II), Taylor vortex flow dominant mode (Case III), fluctuation maintaining Taylor cell structure mode (Case IV), segregation between Couette flow and Taylor vortex flow mode (Case V) and upward motion mode (Case VI). These flow modes weremapped in terms of the Reynolds and Grashof numbers. Cases II, IV, V and VI are regarded as transition flow patterns between Case I and Case III, depending on the concentration. In addition, numerical simulations showed that in Case II, heat transfer was enhanced when the Taylor-Couette flow was altered by heat convection. Moreover, the average Nusselt number with the alternate flow was higher than that with the stable Taylor vortex flow. Thus, the interaction between heat convection and Taylor-Couette flow is an effective tool to enhance heat transfer. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (Part 2)'.

Effects of popping on nutrient contents of amaranth seed.

Amaranth seeds can be popped by heating. The traditional method of popping in a skillet is simple, but it is difficult to control the heating time and temperature. To overcome these disadvantages, we developed a fluidized bed continuous processing system based on hot air heating for producing popped amaranth seeds in bulk. Using this system, we evaluated the effects of heat treatment at 260 °C for 15 s on the contents of B-group vitamins and essential and trace elements in amaranth seeds. The results showed that the treatment did not affect the content of B-group vitamins, and the recovery for essential and trace elements was 97-196%. This popping system is useful for processing amaranth seeds in terms of the product quality and nutrition.

Effect of moisture content on the expansion volume of popped Amaranth seeds by hot air and superheated steam using a fluidized bed system.

The effect of the initial moisture content (X(0)) of amaranth seeds on expansion volume after popping was examined in hot air and superheated steam (SHS), using a fluidized bed system (FBS). The moisturized seeds were prepared under various vapor pressures due to various saturated salt solutions. In hot air, the maximum expansion volume was shown by seeds having X(0) of 0.16 at 260 degrees C for 15 sec, reaching 8.7-fold of the pre-popped seeds. Heating by SHS decreased the volume slightly. Thus, popping of amaranth seeds is influenced not only by the moisture content of the seeds, but also by moisture in the heat media.