Performance of a LiBr water absorption chiller operating with plate heat exchangers

This paper studies the performance of a lithium bromide water absorption chiller operating with plate heat exchangers (PHE). The overall heat transfer coefficients in the desorber, the condenser and the solution heat recoverer are calculated using the correlations provided in the literature for evaporation, condensation and liquid to liquid heat transfer in PHEs. The variable parameters are the external driving temperatures. In the desorber, the inlet temperature of the hot fluid ranges from 75°C to 105°C. In the condenser and the absorber, the inlet temperature of the cooling water goes from 20°C to 40°C. The coefficient of performance (COP) obtained ranges from 0.5 to 0.8 for cooling duties ranging from 2 kW to 12 kW. The chiller response to different hot fluid temperatures and circulated mass flow rates is also presented. The performance and the internal parameters of the chiller at part load are, therefore, calculated. A higher efficiency results when the solution pumped from the absorber to the desorber decreases. The heat transfer analysis of the PHEs is also presented. The overall heat transfer coefficient in the desorber, equal to 790 W/m²K at the design conditions, is also analysed at part load. The condenser performance can be represented by a similar relationship found in conventional air cooled condensersThis work was partially funded by CICYT Ministerio de Ciencia y Tecnología (CLIMABCAR project no. DPI 2003-01567)Publicad

On the pressure drop in plate heat exchangers used as desorbers in absorption chillers

The influence of the pressure drop in Plate Heat Exchangers (PHE) in the boiling temperature of LiBr H₂O and NH₃ H₂O solutions is studied. For the NH₃H₂O solution, the pressure drop-temperature saturation relationship estates that high pressure drops can be allowed in the solution with negligible changes in the saturation temperature, and in the PHE performance. Besides, in the case of the LiBr H₂O solution, as the working pressure is usually very low, the analysis of the pressure drop must be taken as a main limiting parameter for the use of Plate Heat Exchangers as vapour generators. In this case, the pressure drop may considerably change the boiling temperature of the solution entering the heat exchanger and therefore a higher heating fluid temperature may be required. A guideline to design these systems is proposedThis work has been partly supported by the ‘‘Ayuda a grupos” of CAM under the project numbers CCG07 UC3M/AMB 3412 and CCG08 UC3M/AMB 4227Publicad

Imaging the buried rim of Campi flegrei caldera (Italy) from array analysis

On September an extended active seismic survey(SERAPIS,Seismic Reflection Acquisition Project for Imaging Structure)was conducted in the Gulf of Naples and Pozzuoli with the aimof providing new insights on the Campi Flegrei caldera structure and of investigating its feeding system(fig.1).About3000air-gunsea-shots were shot(fig.3a,b,c).In the frame work of this project,anarray of 28 vertical-component and 4 three component sensors was deployed in the Solfatara crater(fig.2).The array had an aperture of about 200m,and receivers had a natural frequency of 1Hz.An example of the recorded wave forms is shown in figure 4

Hydrophobicity of soils affected by fires: An assessment using molecular markers from ultra-high resolution mass spectrometry

Soil water repellency (SWR) is a physical property due to a complex interaction of factors (e.g., fire, soil organic matter, soil texture) that reduces the soil water infiltration capacity. Traditionally, SWR is attributed to the accumulation and redistribution of hydrophobic compounds within soil profile. To obtain further insight into chemical compounds, which could be associated with SWR, a study was done on coarse (1–2 mm) and fine (< 0.05 mm) granulometric fractions of burned and unburned sandy soils under two Mediterranean vegetation biomes from Doñana National Park (Spain). The water drop penetration time (WDPT) test was used to assess the SWR. The molecular composition of extracted humic substances from the soil organic matter (SOM) was determined by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS). Partial least squares (PLS) regressions showed that the SWR can be predicted (P = 0.006) solely based on the abundances of approximately 1200 common compounds determined by FT-ICR/MS. This model confirmed the significant correlation between a specific SOM molecular composition and the SWR. The comparative analysis revealed that the SWR in the burned samples was significantly (P < 0.05) related to the abundance of aromatic and condensed compounds, while in the unburned samples there was a significant influence of aromatic hydrocarbons and lignin compounds. In the fine fraction, lipid compounds were significantly associated with the SWR. Contrastingly, the coarse fraction did not show any correlation. Alternatively, soils with a high SWR were significantly related to the presence of lipids and lignin. This analysis showed that combining FT-ICR/MS molecular characterizations with statistical treatments is a powerful approach for exploratory analysis suggesting that the structural features associated with SWR in the studied soils are different depending on the types of vegetation or the soil physical fractions with different particle size

Deterministic single-photon source from a single ion

We realize a deterministic single-photon source from one and the same calcium ion interacting with a high-finesse optical cavity. Photons are created in the cavity with efficiency (88 +- 17)%, a tenfold improvement over previous cavity-ion sources. Results of the second-order correlation function are presented, demonstrating a high suppression of two-photon events limited only by background counts. The cavity photon pulse shape is obtained, with good agreement between experiment and simulation. Moreover, theoretical analysis of the temporal evolution of the atomic populations provides relevant information about the dynamics of the process and opens the way to future investigations of a coherent atom-photon interface

Heralded single photon absorption by a single atom

The emission and absorption of single photons by single atomic particles is a fundamental limit of matter-light interaction, manifesting its quantum mechanical nature. At the same time, as a controlled process it is a key enabling tool for quantum technologies, such as quantum optical information technology [1, 2] and quantum metrology [3, 4, 5, 6]. Controlling both emission and absorption will allow implementing quantum networking scenarios [1, 7, 8, 9], where photonic communication of quantum information is interfaced with its local processing in atoms. In studies of single-photon emission, recent progress includes control of the shape, bandwidth, frequency, and polarization of single-photon sources [10, 11, 12, 13, 14, 15, 16, 17], and the demonstration of atom-photon entanglement [18, 19, 20]. Controlled absorption of a single photon by a single atom is much less investigated; proposals exist but only very preliminary steps have been taken experimentally such as detecting the attenuation and phase shift of a weak laser beam by a single atom [21, 22], and designing an optical system that covers a large fraction of the full solid angle [23, 24, 25]. Here we report the interaction of single heralded photons with a single trapped atom. We find strong correlations of the detection of a heralding photon with a change in the quantum state of the atom marking absorption of the quantum-correlated heralded photon. In coupling a single absorber with a quantum light source, our experiment demonstrates previously unexplored matter-light interaction, while opening up new avenues towards photon-atom entanglement conversion in quantum technology.Comment: 10 pages, 4 figure

Twin digital short period seismic Array Experiment at Stromboli Volcano

Two small arrays composed by short period (1 Hz) digital seismic stations, with an aperture of approximately 400 meters, were set up at Stromboli volcano (one at semaforo Labronzo, the other at Ginostra- Timpone del Fuoco) with the purpose of the spatial location of the high frequency source of the explosion quakes. About 75 explosion-quakes were recorded at both arrays, and constitute the available data base. We have planned to apply the zero-lag cross-correlation technique to the whole data set in order to obtain back-azimuth and apparent slowness of the coherent seismic phases. A preliminary analysis for both arrays show that the predominant back-azimuth for the first phase is oriented in the direction of , but not strictly coincident to, the crater area. Moreover some back-scattered arrivals are quite evident in the seismogram.INGV - Osservatorio VesuvianoUnpublishedope

Soil carbon stabilization pathways as reflected by the pyrolytic signature of humic acid in agricultural volcanic soils

Molecular assessment of the origin and transformation processes of soil organic matter (SOM) was carried out based on information obtained from 13C NMR and analytical pyrolysis of humic acids (HAs) in soils from wine-growing regions in Tenerife (Canary Islands, Spain). Principal component analysis, using as variables pyrolysis products, shows different soil groups defined by the molecular assemblages released from the corresponding HAs, characterized by the predominance of: i) plant biomacromolecules (lignin) in soils on pumice substrate, ii) heterocyclic N-compounds and methoxyl-lacking aromatic structures, iii) a substantial domain of alkyl compounds in cultivated soils with active C turnover and finally, iv) polysaccharide and protein-derived compounds in soils developed on amorphous gels. The proportions of the pyrolytic compounds from soil HAs were represented by an upgraded graphical-statistical method (3D Van Krevelen plot) that was used to compare the major SOM structural domains in the different soils. The above results coincide with those suggested by the 13C NMR analysis, and were associated to two groups of local land management practices, in terms of their intensity respectively favoring either the transformation of plant-inherited macromolecular precursors from vascular plants, or the humification of aliphatic precursors in the presence of specific mineralogical substrates controlling microbial degradation and humification processes.This research has been funded by the Spanish CICyT under grant CGL2013-43845-P . The authors wish to thank to three anonymous referees by their constructive comments that contributed to improving the final version of the paper.info:eu-repo/semantics/publishedVersio

A double Seismic Array Experiment on Mt. Etna

On September 1999 two seismic antennas (array) and a profile of 3-D stations equipped with short period seismometers were installed on Mt. Etna; Aims of the experiment were to investigate the structure and the polarisation parameters of the volcanic tremor wavefield radiated in eruptive conditions, and to measure the seismic velocities and attenuation in the shallow structure beneath the arrays. The first array was installed close to Pizzi Deneri Volcanological Observatory, East of the crater area; the second array was located close to Torre del Filosofo site, south of the crater area. The profile was set up close to the Pizzi Deneri array. It had a length of 600 meters and consisted of 16 short period 3- component stations. In addition, a circular array of 8 short period seismometers was set up around the main crater area (Fig. 1). Several tremor samples and explosions quakes were recorded in 10 days of operation . Spectrograms show predominant energy into 1-4 Hz frequency band. Slowness spectra indicate a predominant source of the tremor located at surface and coincident with the crater area. Polarisation analysis show that the direction of predominant motion is transverse with respect to the direction pointing to the active craters.INGV - Osservatorio VesuvianoUnpublishedope

Twin digital short period seismic Array Experiment at Stromboli Volcano

Two small arrays composed by short period (1 Hz) digital seismic stations, with an aperture of approximately 400 meters, were set up at Stromboli volcano (one at semaforo Labronzo, the other at Ginostra- Timpone del Fuoco) with the purpose of the spatial location of the high frequency source of the explosion quakes. About 75 explosion-quakes were recorded at both arrays, and constitute the available data base. We have planned to apply the zero-lag cross-correlation technique to the whole data set in order to obtain back-azimuth and apparent slowness of the coherent seismic phases. A preliminary analysis for both arrays show that the predominant back-azimuth for the first phase is oriented in the direction of , but not strictly coincident to, the crater area. Moreover some back-scattered arrivals are quite evident in the seismogram