Thickness and Thermal Conductivities of the Walls and Fluid Layer Effects on the Onset of Thermal Convection in a Horizontal Fluid Layer Heated from Below

The thermal boundary conditions have important effects on the hydrodynamics of a thermo‐convective fluid layer. These effects are introduced through the Biot number under the Robin type boundary conditions. The thermal conductivity and thicknesses of the walls are key properties to bridge two known ideal situations widely studied: the fluid layer bounded by two insulating walls and the fluid layer bounded by two perfect thermal conducting walls. This chapter is devoted to the physical mechanisms involved in the thermal boundary conditions, its influence on the linear stability of the fluid layer and its implications with the pattern formation. A review of very important investigations on the subject is also given. The role of the thermal conductivities and thicknesses of the walls is explained with help of curves of criticality for the thermoconvection in a horizontal Newtonian fluid layer

Development of a Sustainable Process for the Solid-Liquid Extraction of Antioxidants from Oat

This research paper studies the development of a sustainable process for the extraction of antioxidants from oat. Experimentation covered two factorials to evaluate significance among temperature, time, particle size and solvent. Total polyphenolic content (TPC) and oxygen radical absorbance capacity (ORAC) were the response variables. ANOVA was applied to find significance among variables and predict optimum conditions though a regression model. Extractions at different solid/solvent ratios were developed to study solvents’ solubility. Process simulation in Aspen Process Developer was carried out to evaluate energy cost, raw material cost, campaign time, and process mass intensity. Solvent and particle size showed significance as main effects, whereas temperature and time presented significance as interactions. From an industrial and sustainable perspective, ethanol (EtOH) in a 1/20 (w/v) ratio was the best choice since it presented the lowest cost for energy and raw material. It also showed the lowest process mass intensity (PMI), short campaign time, highest g extract/g oat, and a considerable antioxidant capacity