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• The available heat transfer correlations for supercritical CO 2 are evaluated. • New correlations for supercritical CO 2 in vertical up/downward tubes are developed. • 12720 data points are predicted with a mean absolute relative error of 20.10%. • The effects of different parameters on heat transfer are discussed. • It is the only predictive model validated over such a wide range of parameters. Supercritical CO 2 is a promising working fluid for many industrial applications. To improve the performances of relevant components and systems, the prediction of the heat transfer of supercritical CO 2 is an important research topic. General explicit heat transfer correlations of supercritical CO 2 for upward and downward flows heated in circular tubes were established using the genetic programming (GP) method. A total of 12720 experimental data points from 22 publications were collected to develop the models. The data included hydraulic diameter from 0.0992 to 22 mm, bulk temperature from -6.0 to 134.5°C, pressure from 7.44 to 10.50 MPa, mass flux from 50 to 4834 kg•(m2•s)−1, heat flux from 2.9 to 748 kW•m−2 and wall temperature from 6.4 to 368.2°C. The database was divided into four parts according to the flow direction and the relationship between the bulk temperature and the pseudo-critical temperature. The developed correlations considered various non-dimensional parameters as the independent variables to reflect the effects of supercritical properties, flow acceleration and buoyancy on the heat transfer. The results showed that the proposed correlations had excellent accuracy with a mean absolute relative error (MARE) of 20.10% based on prediction with the iterated wall temperature. The developed correlations outperformed the existing correlations in the literature. Compared to other correlations, the trend analysis indicated that these newly developed correlations could appropriately present the physics sense when the condition parameters varied. [ABSTRACT FROM AUTHOR]

In vitro antioxidant activities of the lipid fractions from two selected seaweeds, Solieria chordalis and Sargassum muticum were investigated according to the extraction methods. The activity of neutral lipids, glycolipids and phospholipids, thanks to extraction by chloroform/methanol (1/1 v/v; CM) mixture, pure supercritical carbon dioxide (sc-CO2), supercritical carbon dioxide with 2% of ethanol (sc- CO2þEtOH 2%) and supercritical carbon dioxide with 8% of ethanol as co-solvent (sc-CO2þEtOH 8%), were studied using DPPH radical scavenging assays. All the lipid classes demonstrated a free radical scavenging activity at the concentration of 1 mg/ml. The best scavenging activity (86.6 ± 5.7%) was obtained when the neutral lipid fraction was extracted from S. chordalis with a CM mixture. The neutral lipid fraction extracted with sc-CO2 showed a lower activity than those obtained with solvents. However, the addition of ethanol in sc-CO2 did not affect the antioxidant activity of neutral lipids fixed at around 16% of radical scavenging. For S. muticum, the activity of glycolipids (50.9 ± 0.8%) and phospholipids (48.4 ± 1.6%) obtained with sc-CO2 were twice as large as that of fractions obtained with CM, 29.6 ± 3.4% and 28.0 ± 4.2%, respectively. The activity of neutral lipids did not change with the extraction method with around 25% of radical scavenging. This is the first report of free radical scavenging activity of lipid classes obtained by supercritical carbon dioxide extraction from seaweeds. [ABSTRACT FROM AUTHOR]

Supercritical fluid extraction (SFE) is a promising remediation technology for contaminated soils. This work investigates the use of SFE to remove petroleum hydrocarbons (PHCs) from flare pit soils. Extractions were performed on two flare pit soils at pressures ranging from 11.0 to 24.1 MPa and at temperatures ranging from 40 to 80 °C in an attempt to identify the best extraction conditions and to understand the effects of pressure, temperature, supercritical fluid flow rate, soil type, and extraction time on the extraction efficiency. For the conditions studied, the efficiency of the SFE process appeared to be solvent-density dependent. Conditions of 24.1 MPa and 40 °C (highest supercritical fluid density) yielded the highest extraction efficiency for both soils (89% for the sand and 80% for the loam). An increase in temperature at a fixed pressure led to a decrease in the extraction efficiency while an increase in pressure at a fixed temperature led to an increase in the extraction efficiency. The treated soils appeared to be drier, grainy, and lighter coloured than the soil prior to extraction. [ABSTRACT FROM AUTHOR]

Le dioxyde de carbone supercritique est un solvant de choix dans le cadre de la production ou de la purification des lipides. Il peut être utilisé à des températures voisines de la température ambiante, il protège les molécules sensibles à l’oxydation et, enfin, il évite l’élimination de solvant organique. La connaissance des équilibres de phases devrait permettre une meilleure précision des procédés de séparation potentielle constituée par l’extraction et la chromatographie préparative supercritique.