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The importance of volumetric expanders has been increasing in the last decades because several studies confirmed that they lead to improved energy savings, limit the environmental impact, and reduce the energy intensity of industrial and domestic applications. In particular, several applications of the two-phase volumetric expanders, in which the operating fluid consists of liquid and vapor phases, were recently proposed. Nevertheless, the contributions in the scientific literature related to the overview of the state-of-the-art aspects of this technology are rare. For this reason, the present work discussed the potentialities and drawbacks of the available typologies of volumetric expanders that process a two-phase pure working fluid by analyzing a summary of leading studies in this field to go beyond previous efforts in the literature. The analysis revealed that twin-screw machines represent the best candidates, while reciprocating piston devices seemed the least well-adapted because of their reduced tolerance to droplets and high friction losses. Flash evaporation appeared to have the most significant impact on the expander because it affects both inlet and expansion phases, thus, determining the shape of the indicated cycle and the isentropic efficiency. [ABSTRACT FROM AUTHOR]

The importance of volumetric expanders has been increasing in the last decades because several studies confirmed that they lead to improved energy savings, limit the environmental impact, and reduce the energy intensity of industrial and domestic applications. In particular, several applications of the two-phase volumetric expanders, in which the operating fluid consists of liquid and vapor phases, were recently proposed. Nevertheless, the contributions in the scientific literature related to the overview of the state-of-the-art aspects of this technology are rare. For this reason, the present work discussed the potentialities and drawbacks of the available typologies of volumetric expanders that process a two-phase pure working fluid by analyzing a summary of leading studies in this field to go beyond previous efforts in the literature. The analysis revealed that twin-screw machines represent the best candidates, while reciprocating piston devices seemed the least well-adapted because of their reduced tolerance to droplets and high friction losses. Flash evaporation appeared to have the most significant impact on the expander because it affects both inlet and expansion phases, thus, determining the shape of the indicated cycle and the isentropic efficiency.

• Experimental tests oriented to HTC process layout assessment. • A flash expansion step could improve plant performances. • The correct process scheme depends on waste biomass treated. • Sulfur emission per unit of energy produced significantly reduced. This paper contributes to the knowledge on waste biomass conversion processes occurring in the presence of hot compressed water. The experimental procedure detailed herein assesses different process schemes based on the low-temperature reaction known as hydrothermal carbonization. The performances of two lab-scale reactor configurations, with and without a downstream flash expansion step, were evaluated and compared. Each setup was tested with six different types of waste biomass. Fir, beech, and olive prunings are representative of lignocellulosic raw materials, while potato, pea, and carrot are representative of non-lignocellulosic wastes from processing in the local agro-food industry. The batch reactions (200 °C, water/solid = 7/1) were carried out for up to 120 min. The hydrochars were characterized by elemental composition, humidity, heating value, and mass and energy yields. The extent of difference between the results obtained for the two procedures varied significantly with the material treated. At a residence time of 30 min, the solid yields increased due to expansion, ranging from 10 to 36% for lignocellulosic material and 50 to 220% for agro-food industry scraps. The downstream flash expansion step causes an increase of the solid yields, especially for hydrochars from lignocellulosic materials, leading to higher energy recovered compared to the configuration without expansion. Lignocellulosic and agro-food wastes behaved dissimilarly, likely because of different hydrothermal reaction pathways. The additional expansion step can considerably increase the efficiency of energy recovery in full-scale plants, the extent of which depends on the biomass waste substrate used. [ABSTRACT FROM AUTHOR]

• Fermenting off skins enhanced red fruit and confectionery aromas but not mouthfeel. • Dark fruit attributes were enhanced when fermenting on or off skins with oak chips. • Flash détente mitigated the intensity of green, savory and dusty sensory attributes. • Oak or tannin addition pre-fermentation did not improve wine color stability. The ability to create differentiated red wine styles is key to meeting the diverse preferences of wine consumers. This study investigated the composition and style of Merlot wines made from flash détente (FD) treated must fermented with different levels of grape solids and skin contact time, and the potential for pre-fermentation addition of enotannin (0.4 g/L) or oak chips (4 g/L) to stabilize color. Off-skins fermentations, with or without addition of enotannin, gave wines with enhanced red fruit and confectionery characters (P = 0.0001), whereas addition of oak chips gave wines with prominent dark fruit, vanilla, toasty and allspice characters (P = 0.0001). However, additives did not improve wine color stability. Macerative fermentation of FD must enhanced dark fruit, body and astringency ratings (P = 0.0001), with FD wines exhibiting less intense green, savory and dusty notes (P = 0.0001). The study demonstrated solids removal had a greater influence on wine composition and style than skin contact time. [ABSTRACT FROM AUTHOR]

The selfish herd hypothesis, as proposed by Hamilton (1971, Journal of Theoretical Biology , 31 , 295–311), is a powerful hypothesis to explain emergent grouping behaviour by individuals acting in their own self-interest. However, immediately after prey detect a predator, the prey group may undergo a rapid disassembly, called a flash expansion, which might be considered a ‘repulsive herd’. Although flash expansion occurs in bird flocks, fish schools and insect swarms, few empirical or simulation studies have directly examined it or tested whether there are differences among its members. In addition, although flash expansion is typically thought of as a near-simultaneous movement of individuals away from the group centre, little data has been collected to verify this. We performed an empirical study to test whether the overall movement of individuals within a flash expansion is away from (1) the first individual to startle, (2) the geometric centre or (3) the point of highest density. We videotaped replicate swarms of marked whirligig beetles (Gyrinidae: Dineutes ) during flash expansion and determined their trajectories. Overall, individuals moved away from the geometric centre more strongly than from the density maximum or the first to respond (starter). The geometric centre hypothesis was also supported by the lack of polarization of the group and that the bearing angle was away from the geometric centre. The starter was more likely to be a female at the edge of a group, and she moved more quickly than others and favoured the centre of the group. This is one of the first detailed examinations of flash expansion and the individual differences within it. Future empirical and simulation studies of the movement rules and emergent properties of flash expansion are needed to better understand the collective motion of other animals. [ABSTRACT FROM AUTHOR]