Development of heat transfer and pressure drop correlations in twisted tube heat exchangers

Heat transfer in concentric twisted tubes exchangers has several applications in the chemical and food industry mainly due to its compact structure and high transport coefficients, however, its use has been limited as a consequence of drop pressure. This study reports Nusselt number and friction factor correlations as a function of the dimensionless Dean number as well as Prandtl number, and a torsional step parameter. Simulations were carried out using ANSYS CFX® V16.0 software at workstations belonging to Grupo de Investigación en Materiales Avanzados y Energía of Instituto Tecnológico Metropolitano. Six geometries were developed with SolidEdge® ST9 academic license. Geometry modification, cleanup, and repair were made although DesignModeler® 2019 academic license. Finally Meshing® for discretization. The mesh size independence, and incidence of the turbulence model, and twisting step validated the computational tools use. Correlation numerically showed an increase of 60% average respect to smooth bending tube. © Published under licence by IOP Publishing Lt

Variación circadiana de los tiempos de tránsito T3 y T4 sobre el ajuste de las fases S, G2 y M en sistemas celulares parcialmente sincronizados

En el artículo se presenta un modelo continuo y determinista de la actividad proliferativa celular. Sobre dicho modelo básico se aplican sucesivos refinamientos que tienen por objeto mejorar el ajuste a datos experimentales existentes. La base experimental del método son los ensayos realizados sobre el pez Cauratus aclimatado a 25 grados con un fotoperiodo de 12 horas durante un mes. Se analizó la actividad proliferativa en las células intestinales observando que aquélla es parcialmente sincronizada. Las medidas efectuadas y su contraste con el método propuesto sugieren que el modelo determinista y contínuo es una aproximación adecuada a la interpretación del ciclo evolutivo. Los resultados numéricos sugieren un comportamiento circadiano también para los tiempos de tránsito en las fases. Las amplitudes se ajustan observando los mínimos de las curvas y la fase se induce mediante análisis armónico de la tendencia general

Optimisation of a high-efficiency solar-driven organic Rankine cycle for applications in the built environment

Recent years have seen a strong increase in the uptake of solar technologies in the built environment. In combined heat and power (CHP) or cogeneration systems, the thermodynamic and economic ‘value’ of the electrical output is usually considered to be greater than that of (an equivalent) thermal output, and therefore the prioritisation of the electrical output in terms of system-level optimisation has been driving much of the research, innovation and technology development in this area. In this work, the potential of a solar CHP technology based on an organic Rankine cycle (ORC) engine is investigated. We present thermodynamic models developed for different collectors, including flat-plate collectors (FPC) and evacuated-tube collectors (ETC) coupled with a non-recuperative sub-critical ORC architecture to deliver power and hot water by using thermal energy rejected from the engine. Results from dynamic 3-D simulations of the solar collectors together with a thermal energy storage (TES) tank are presented. TES offers an important buffering capability during periods of intermittent solar radiation, as well as the potential for demand-side management (DSM). Results are presented of an optimisation analysis to identify the most suitable working fluids for the ORC unit, in which the configuration and operational constraints of the collector array are taken into account. The most suitable working fluids (R245fa and R1233zd) are then chosen for a whole-system optimisation performed in a southern European climate. The system configuration with an ETC array is found to be best-suited for electricity prioritisation, delivering an electrical output of 3,605 kWh/yr from a 60 m2 array. In addition, the system supplies 13,175 kWh/yr in the form of domestic hot water, which is equivalent to more than 6 times the average annual household demand. A brief cost analysis and comparison with photovoltaic (PV) systems are also performed

An integrated approach to model strain localization bands in magnesium alloys

Strain localization bands (SLBs) that appear at early stages of deformation of magnesium alloys have been recently associated with heterogeneous activation of deformation twinning. Experimental evidence has demonstrated that such “Lüders-type” band formations dominate the overall mechanical behavior of these alloys resulting in sigmoidal type stress–strain curves with a distinct plateau followed by pronounced anisotropic hardening. To evaluate the role of SLB formation on the local and global mechanical behavior of magnesium alloys, an integrated experimental/computational approach is presented. The computational part is developed based on custom subroutines implemented in a finite element method that combine a plasticity model with a stiffness degradation approach. Specific inputs from the characterization and testing measurements to the computational approach are discussed while the numerical results are validated against such available experimental information, confirming the existence of load drops and the intensification of strain accumulation at the time of SLB initiation

Reciclando conocimientos en TICs: herramientas online y offline para su utilización en la enseñanza virtual y en la coordinación docente

El profesorado de nuestra Facultad ha ido solicitando la realización de cursos formativos sobre las nuevas tecnologías y profundizar en las herramientas más habituales, sobre todo, con las posibilidades que ofrece el Campus Virtual. Con este proyecto se pretendieron cubrir fundamentalmente dos demandas: - Optimizar la utilización de las plataformas virtuales. - Conocer herramientas offline útiles para la docencia y la coordinación docente. En total, se han realizado 7 actividades manteniendo una estructura lógica de cronología y continuidad en las mismas. De la mayoría de ellas se han generado tutoriales como material de ayuda, que se han puesto a disposición del resto de profesores y PAS en un Seminario de Trabajo abierto creado en Moodle expresamente, denominado “PIMCD2014: Reciclando conocimientos…” (seminario-invest-97673-11)

Spectrometric characterization of amorphous silicon PIN detectors

During the last years, much interest has been dedicated to the use of amorphous silicon PIN diodes as particle and radiation detectors for medical applications. This work presents the spectrometric characterization of PECVD high deposition rate diodes fabricated at our laboratory, with thickness up to 17.5 μm. Results show that the studied devices detect the Am^(241) alpha particles and the medical X-rays generated by a mammograph model Senographe 700T from General Electric. Possible reasons of the observed energy losses are discussed in the lest. Using the SRIM2000 program, the transit of 5.5 MeV alpha particles through a diode was simulated, determining the optimum thickness for these particles to deposit their energy in the intrinsic layer of the diode

Single nucleotide polymorphism (SNP) analysis used for the phylogeny of the Mycobacterium tuberculosis complex based on a pyrosequencing assay

Background Different polymorphisms have been described as markers to classify the lineages of the Mycobacterium tuberculosis complex. The analysis of nine single nucleotide polymorphisms (SNPs) was used to describe seven SNPs cluster groups (SCGs). We attempted to classify those strains that could not been categorized into lineages by the genotyping methods used in the routine testing. Results The M. tuberculosis complex isolates collected in 2010 in our region were analysed. A new method based on multiplex-PCRs and pyrosequencing to analyse these SNPs was designed. For the pyrosequencing assay nine SNPs that defined the seven SCGs were selected from the literature: 1977, 74092, 105139, 232574, 311613, 913274, 2460626, 3352929 and gyrA95. In addition, SNPs in katG463, mgtC182, Ag85C103 and RDRio deletion were detected