Heat transfer enhancement using nanofluids in the compression exchanger in a solar Stirling engine

In this paper a improvement in the heat exchange of a solar Stirling engine during the compression phase was studied. The viability of using nanoparticles as ceramic oxide (Al2O3 in water) at different concentrations instead of conventional refrigerants (water or air) was evaluated. Since these systems could behave as non- Newtonian fluids the dynamic viscosity was measured, as well as other thermophysical properties. The results showed that the convective heat transfer coefficient could raise one order of magnitude respect to the conventional heat transfer fluids at moderately volume fractions (over 0.15).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Characterization and thermophysical properties of rutile and alumina nanofluids

The characterization in relation to shape and particle size of alumina and rutile suspensions was performed. The intrinsic viscosity exhibited the presence of nonspherical aggregates in both suspensions although TEM images showed non monodisperse spherical shape of alumina particles. DLS indicated the existence of particle aggregates for both systems. In all cases, the increase in thermal conductivity with respect to the base fluid is verified. The thermal conductivities obtained experimentally were compared with three mathematical models, which yielded lower values than those measured. From rheological measurements and by means of the Peclet number defined in colloidal suspensions, values of thermal conductivity were also proposed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Rheological study of the aggregation state of alumina nanofluids

Se adjunta una comunicación, aunque se han publicado tres comunicaciones más.The presence of alumina solid particles in aqueous phase induces a change in the viscosity of the suspension from Newtonian to non- Newtonian flow. Besides, the presence of solid particles is adequate for the use as a heat exchanger fluid. The effect of nanoparticle size on thermal properties of nanofluids is still today a question, which is far from being answered. In this respect, the results reported in the literature are contradictory [1], probably due to the formation of aggregates when particles are dispersed in the liquid phase. Regarding to the nanoparticle shape influence in thermal conductivity, cylinders and spheres have been considered as the more effective in heat transfer. Spherical nanoparticles of alumina, which is one of the most investigated nanofluid, dispersed in water were used in this study. TEM images showed a mean average diameter of 50 nm. However, DLS measurements showed monodispersed particles of 260 nm. Very recently [2], the relationship between shear rheology and aggregation state of suspensions has been reviewed. Mechanical and physical properties of the resultant materials depend on shape, size and size distribution, which are considered determining parameters in the formation of particle aggregates. The steady shear flow (figure 1) has shown that these clusters, when they are at rest, are formed by highly branched aggregates that erode when shear rate increases, until a suspension of individual particles is achieved. These results are in good agreement with the intrinsic viscosity obtained by Money and Krieger-Dougherty models. In both cases, these values are far from the 2.5 corresponding to spherical particles. The temperature effects were also taken into account.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Consecuencias de la pandemia COVID – 19 en la promoción turística en una entidad pública, Sullana – 2023

A inicios del 2020 el Perú se declaró en estado de emergencia, prohibiendo el ingreso de turistas, viéndose perjudicado el sector Turismo siendo el gran generador de ingresos a los empresarios de mencionado rubro. Se planteó como objetivo general analizar las consecuencias de la pandemia COVID – 19 en la promoción turística de una entidad pública, Sullana – 2023. Se desarrolló un enfoque cualitativo de tipo aplicada, de profundidad descriptiva – explicativa, se basa en un estudio de casos, de método hermenéutico y de triangulación conociendo un poco más el manejo de la entidad pública ante una crisis, el estudio se realizó en la Provincia de Sullana. Se planteó como técnica la entrevista y como instrumento la guía de entrevista, los participantes estuvieron conformados por ex funcionario público, aliaos estratégicos del sector turismo, pobladores, periodista y licenciado en Turismo con 5 instrumentos distintos, para cumplir con los objetivos, sin perder la esencia de la categoría, luego de efectuado el análisis de información obtenida. Se concluye que las consecuencias de la pandemia aún se sufren, tomando tiempo para reactivar el sector turismo. Se recomienda contar con un plan estratégico para futuras crisis de enfermedades, esto permitiendo entender de una mejor perspectiva las interrogantes planteadas

The TAGA Study: A Study of Factors Determining Aortic Diameter in Families at High Risk of Abdominal Aortic Aneurysm Reveal Two New Candidate Genes

A variety of disorders are known to be related with aortic geometry, among them abdominal aortic aneurysm (AAA). This work aims to present the main determinants of abdominal aortic diameter in a new cohort of families at high risk of AAA. The Triple-A Genomic Analysis (TAGA) study comprises 407 individuals related in 12 families. Each family was collected through a proband with AAA. We calculated heritability and genetic correlations between abdominal aortic diameter and clinical parameters. A genome-wide linkage scan was performed based on 4.6 million variants. A predictive model was calculated with conditional forest. Heritability of the abdominal aortic diameter was 34%. Old age, male sex, higher height, weight, creatinine levels in serum, and better lung capacity were the best predictors of aortic diameter. Linkage analyses suggested the implication of Epidermal Growth Factor Receptor (EGFR) and Betacellulin (BTC) genes with aortic diameter. This is the first study to evaluate genetic components of variation of the aortic diameter in a population of AAA high-risk individuals. These results reveal EGFR, a gene that had been previously implicated in AAA, as a determinant of aortic diameter variation in healthy genetically enriched individuals, and might indicate that a common genetic background could determine the diameter of the aorta and future risk of AAA

Thermophysical and flow properties of coconut oil with silica fumed nanoparticles

This work is concerned with the rheological and thermal study of silica fumed dispersed in coconut oil. The dispersed phase behave as a non newtonian fluid during the phase change. The addition of nanoparticles complicates considerably the flow behaviour of the system. Therefore, a very thoughtful study of the flow and thermal properties with temperature when silica particles are added must be carried out.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Utilization of secondary-treated wastewater for the production of freshwater microalgae

In this work we studied the potential use of secondary-treated wastewater as nutrient source in the production of freshwater microalgae strains. Experiments were performed indoors in semicontinuous mode, at 0.3 day-1, simulating outdoor conditions. We demonstrated that all the tested strains can be produced by using only secondary-treated wastewater as the nutrient source. The utilization of secondary-treated wastewater imposes nutrient-limiting conditions, with maximal biomass productivity dropping to 0.5 g·l-1·day-1and modifies the biochemical composition of the biomass by increasing the amount of lipids and carbohydrates while reducing the biomass protein content. We measured fatty acids content and productivity of up to 25%d.wt. and 110 mg·l-1·day-1, respectively. We demonstrated that all the tested strains were capable of completely removing the nitrogen and phosphorus contained in the secondary-treated wastewater, and while the use of this effluent reduced the cells’ photosynthetic efficiency, the nitrogen and phosphorus coefficient yield increased. Muriellopsis sp. and S. subpicatus were selected as the most promising strains for outdoor production using secondary-treated wastewater as the culture medium; this was not only because of their high productivity but also their photosynthetic efficiency, of up to 2.5%, along with nutrient coefficient yields of up to 96 gbiomass·gN-1 and 166 gbiomass·gP-1. Coupling microalgae production processes to tertiary treatment in wastewater treatment plants makes it possible to recover nutrients contained in the water and to produce valuable biomass, especially where nutrient removal is required prior to wastewater discharge