Theoretical and Experimental Activity on Ejector Refrigeration

Abstract Ejector refrigeration has been studied at DIEF (Dipartimento di Ingegneria Industriale Firenze) since the '90s. Use of environmentally safe fluids (steam) was addressed. A two-stage prototype with cooling capacity 5 kW was optimized and built. Later, the CRMC prescription for the design of the supersonic diffuser was focused. By a gradual reduction of the fluid velocity and a continuous profile, the CRMC design promises a reduction of the normal shock that usually develops in the mixing chamber. A second 40 kWf prototype was designed in 2010 for an industrial partner (Frigel Firenze s.p.a.). The design procedure used a thermodynamic code accounting for real gas behavior. This code gives a first design of the mixing chamber and diffuser according to the CRMC criterion. It also gives an estimation of the friction loss along the diffuser. A comparison between different operating fluids was performed and resulted in the selection of R245fa. A first design of the ejector was manufactured in carbon fiber. The primary nozzle is mounted on a movable support, in order to change its axial position with respect to the mixing chamber. In terms of COP, first results were below the values predicted by the simulation code. Meanwhile a numerical simulation was in progress with FLUENT. From the first CFD results it was decided that the diffuser throat had to be moved forward from the primary nozzle exit, in order to allow a complete mixing between the primary and secondary flows, and enlarged, the losses encountered in the mixing process being higher than expected and hence the fluid density lower. This produced a second ejector design, which was manufactured and tested in 2012, showing improved performance. These results suggested a third design, with a further lengthened diffuser, which has undergone a complete testing campaign, allowing validation of the CFD results. The activity performed till now suggests that ejector refrigeration plants have a robust operation and can be easily manufactured at relatively low cost with off-the-shelf components, a part from the ejector itself, which however represents a small fraction of the system cost. However, the COP is lower with respect to absorption refrigeration and hence needs substantial improvement through detailed thermodynamic and CFD design optimization

Exploitation competition between hole-nesters (Muscardinus avellanarius, Mammalia and Parus caeruleus, Aves) in Mediterranean woodlands

Data from a long-term study (1993-2003) using artificial nest-boxes, were analysed to examine competition for nesting between blue tit Parus caeruleus and common dormouse Muscardinus avellanarius in Sicily. Occupation rates and the reproductive biology of the blue tit in sample woodlots outside the distribution area of the common dormouse were used as a control in sample areas where the two species were syntopic. A selection test showed that the two species, when living in syntopy, actively chose the small nest-boxes, thus overlapping in the use of the same spatial resource. The experimental exclusion of the common dormouse from nest-boxes caused an increase of blue tit occupation rate. Once the effect of nest-box density was removed, complementary density changes between the two species clearly appeared. The population cycle of both species in the areas of syntopy showed a swinging pattern, i.e. in areas or during years of common dormouse high abundance few blue tits bred and vice versa. The abundance of the blue tit was affected not only by common dormouse abundance, but also by some habitat and climate variables. Blue tits had low breeding success and a high percentage of nest failure (38% in syntopy vs 3% in control areas), owing to nest destruction and predation by common dormouse, as well as probably also by other rodents (23%) and Martes martes (15%). Another experiment, using stuffed models, showed that the blue tit recognized the common dormouse as an enemy, and behaved as if confronted by a competitor or predator species to protect their nests. © 2005 The Zoological Society of London

Impact of Different Developmental Instars on Locusta migratoria Jumping Performance

Ontogenetic locomotion research focuses on the evolution of locomotion behavior in different developmental stages of a species. Unlike vertebrates, ontogenetic locomotion in invertebrates is poorly investigated. Locusts represent an outstanding biological model to study this issue. They are hemimetabolous insects and have similar aspects and behaviors in different instars. This research is aimed at studying the jumping performance of Locusta migratoria over different developmental instars. Jumps of third instar, fourth instar, and adult L. migratoria were recorded through a high-speed camera. Data were analyzed to develop a simplified biomechanical model of the insect: the elastic joint of locust hind legs was simplified as a torsional spring located at the femur-tibiae joint as a semilunar process and based on an energetic approach involving both locomotion and geometrical data. A simplified mathematical model evaluated the performances of each tested jump. Results showed that longer hind leg length, higher elastic parameter, and longer takeoff time synergistically contribute to a greater velocity and energy storing/releasing in adult locusts, if compared to young instars; at the same time, they compensate possible decreases of the acceleration due to the mass increase. This finding also gives insights for advanced bioinspired jumping robot design

Sexually transmitted Q fever

We report the sexual transmission of Coxiella burnetii from a man with occupationally acquired Q fever to his wife. Fifteen days after coitus, his wife also developed serologically proven acute Q fever. C. burnetii DNA sequences were detected by polymerase chain reaction (PCR) performed on semen samples obtained from the husband at 4 and 15 months after the onset of acute Q fever, but PCR results were variable at 23 months, indicating the presence of few organisms.Adriana Milazzo, Robert Hall, Paul A. Storm, Ray J. Harris, William Winslow and Barrie P. Marmio

Volcanogenic particulates and gases from Etna volcano (Italy)

Volcanic emissions represent one of the most relevant natural sources of trace elements to the troposphere. Due to their potential toxicity they may have important environmental impacts from the local to the global scale and they can severely affect the atmospheric and terrestrial environment also at timescales ranging from a few to million years. Etna volcano is known as one of the largest global contributors of magmatic gases (CO2, SO2, and halogens) and particulate matter, including some toxic trace elements. The aim of this study was to characterize the chemical composition and the mineralogical features of the volcanogenic aerosol passively emitted from Mt. Etna. Nine samples were collected by using the filtration technique at different sites on summer 2010 and 2011. Chemical and mineralogical analyses allowed to discriminate two main constituents: the first is mainly referable to the silicate component in the volcanic plume, like lithic and juvenile fragments, crystals (e.g., plagioclases, pyroxenes, oxides) and shards of volcanic glass; the second one is linked to the soluble components like sulfosalts or halide minerals (sulfates, chlorides and fluorides). These investigations are especially important in the study area because the summit of Mt. Etna is yearly visited by nearly one hundred thousand tourists that are exposed to potentially harmful compounds

The use of moss-bags technique for volcanic aerosols investigation on Mt. Etna (Italy)

Explosive eruptions and volcanic passive degassing inject large quantities of gas and particles into the atmosphere that are ultimately deposited at the Earth’s surface through wet or dry deposition processes, affecting the atmosphere, the hydrosphere and the biosphere. Mount Etna (Italy) is one of the most prodigious and persistent sources of gases and particles to the troposphere. Volcanic emissions were studied at Etna volcano by using moss-bags technique. Mosses (Sphagnum species) were exposed around the volcano at different distances from the active vents to evaluate the impact of its emissions into the atmosphere and in the local surrounding. The results confirmed the huge amount of silicates, sulfates and halides compounds emitted into the atmosphere from Mount Etna. X-ray microanalysis showed that chemical composition of the particles is mostly defined by silicate (from pure silica to metal-rich silicate composition) and sulfate/halide compounds. The contents of major and trace elements in the Sphagnum moss-bags significantly increased after their exposure to volcanic emissions, confirming mosses as efficient accumulators. Metals uptake rate rapidly decreases with the distance from the volcanic emission vents. The elements that showed the greatest accumulation after exposition were S, Na, Fe, Al, Cu, V, As, Cd, Li, Se, Sc, Th, Bi and Tl. This study confirmed the marked environmental impact of volcanic emissions in the eastern sector of Etna, leading to an intense “geochemical anomaly” of volatile major and trace elements due to the fumigation by the volcanic plume, in agreement with passive biomonitoring studies reported by previous authors. Finally, moss-bags techniques provide a cheap and efficient method to investigate quantitatively in space and time the environmental impact of volcanogenic atmospheric deposition

Volcanogenic particulates and gases from Etna volcano (Italy)

Volcanic emissions represent one of the most relevant natural sources of trace elements to the troposphere. Due to their potential toxicity they may have important environmental impacts from the local to the global scale and they can severely affect the atmospheric and terrestrial environment also at timescales ranging from a few to million years. Etna volcano is known as one of the largest global contributors of magmatic gases (CO2, SO2, and halogens) and particulate matter, including some toxic trace elements. The aim of this study was to characterize the chemical composition and the mineralogical features of the volcanogenic aerosol passively emitted from Mt. Etna. Nine samples were collected by using the filtration technique at different sites on summer 2010 and 2011. Chemical and mineralogical analyses allowed to discriminate two main constituents: the first is mainly referable to the silicate component in the volcanic plume, like lithic and juvenile fragments, crystals (e.g., plagioclases, pyroxenes, oxides) and shards of volcanic glass; the second one is linked to the soluble components like sulfosalts or halide minerals (sulfates, chlorides and fluorides). These investigations are especially important in the study area because the summit of Mt. Etna is yearly visited by nearly one hundred thousand tourists that are exposed to potentially harmful compounds

Plants as biomonitors for volcanic emissions

Biomonitoring techniques have been widely used in environmental studies to monitor anthropogenic pollutant. Recently such techniques have been applied also to ascertain the impact of contaminants naturally released by volcanic activity. In the present study a biomonitoring surveys has been performed in many different active volcanic systems: Mt. Etna and Vulcano (Italy), Nisyros (Greece), Nyiragongo (DRC), Masaya (Nicaragua), Gorely (Kamchatka, Russia). We sampled leaves of different species Betulla aethnensis, Pinus nigra, Populus tremula, Senecio aethnensis and Rumex aethnensis on Etna, Cistus creticus and salvifolius on Vulcano and Nisyros, Senecio ssp. on Nyiragongo, a Fern on Masaya and Salix arctica at Gorely. All samples were analyzed by ICP-MS and ICP-OES for 49 elements after acid digestion with a microwave oven (HNO3 + H2O2). Major constituents in leaves are K, Ca, Mg, Na, Si, Al and Fe ranging from about 10 3 to 105 ppm. Manganesium, Sr, Rb, Ba, Zn, B, Cu show also relatively high concentrations (100-103 ppm) while the remaining elements (As, Bi, Cd, Ce, Co, Cr, Cs, Ga, Li, Mo, Ni, Pb, Sb, Sc, Se, Th, Tl, U, V, Y and lanthanide series) display much lower values (10-4-101 ppm). Nearly all investigated elements show their highest concentrations in the samples collected closest to the main degassing vents (open craters, fumarolic fields). Increased concentrations are also found in the samples collected in the downwind direction where volcanic emissions are prevailingly dispersed. Leaves collected along radial transects from the active vents, highlight that the levels of metals decrease from one to two orders of magnitude with increasing distance from the source. The decrease is stronger for volatile elements, which are highly enriched in volcanic emissions, (As, Bi, Cd, Cs, Pb, Sb, Tl) than for more refractory elements (Al, Ba, Sc, Si, Sr, Th, U). The different species of plants show significant differences in the bioaccumulation processes for most of the analyzed elements, in particular lanthanides, which are systematically enriched in Rumex leaves. Needles of pine (non-deciduous tree) represent a good tool for biomonitoring investigation because they are important tracers of accumulation with time. The high concentrations of many toxic elements in the leaves allow us to consider some of these plants as highly tolerant species to the volcanic emissions, and suitable for biomonitoring researches further confirming their strong potential in tracing the impact and geographic distribution of these natural contaminants