Structural and numerical identifiability of thermal resistances in plate fin-and-tube heat exchangers using manufacturer catalog data

Plate fin-and-tube heat exchangers, commonly known as heating/cooling coils, are widely used in HVAC systems to transfer heat to or from air. A problem of practical interest in coil simulation is to identify the thermal resistances on the air and liquid sides using manufacturer catalog data. Manufacturers rarely provide detailed information (geometry and circuitry) of the coils they sell or install in factory-made equipment such as air handling units or fan-coils; they just report the performance of the coil at a few typical operating conditions. This paper examines whether it is mathematically possible to back-calculate the thermal resistances on the air and liquid sides using a set of performance data that is disturbed by noise (e.g. measurement errors) and consists of operating cases in which none of the two thermal resistances can be neglected. The first part of the paper discusses the structural identifiability problem, that is, the mathematical possibility of fitting Nusselt-type correlations for air and liquid, as well as a constant resistance for the wall. The second part of the paper discusses the possibility of calculating the numerical value of the parameters of the Nusselt correlations (constant or constant and exponent) using noisy data. The analysis is applied to a typical coil, which is simulated by means of a mathematical modelUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

EFFECTS OF LOUVERS SHADING DEVICES ON VISUAL COMFORT AND ENERGY DEMAND OF AN OFFICE BUILDING. A CASE OF STUDY

This paper evaluates the building energy demand and visual comfort of a real case with a glazed façade office building placed in Málaga (Mediterranean city in the south of Spain). South oriented facades receive such a high solar gain that cooling demand cannot be handled by the current HVAC system. As an environmental friendly solution, a shading control strategy based on vertical and horizontal louvers is proposed. The study consists of a comparison between the actual and the refurbished building with shading devices. Daylighting simulation is done with Daysim (Daysim, 2016). A group of offices with south, east and north oriented facades is chosen for the study. Horizontal louvers in the south façade and vertical louvers in the east facade are modelled and simulated. The simulation changes the angle of the louver: 0º (perpendicular to the glazing), -30º, 30º, -60º, 60º. Visual comfort parameters analyzed are: illuminance, daylight autonomy (DA) and useful daylight index (UDI). With respect to the thermal comfort, not only louvers orientation try to provide solar protection for glazed areas in cooling period but also maximize solar gains in heating period. However, an excessive daylight could affect discomfort glare. Shading control strategy must provide the equilibrium between both aspects. Thermal demand is calculated with Trnsys (TRNSYS, 2016).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Conductive Polymer Composites Synthesized from Diacetylene-Functionalized Linseed Oil and MWCNT: Gamma Irradiation and Organic Vapor Sensing

Beca de estancia de Posdoctorado del Dr. Alejandro Ramírez JiménezEpoxidized linseed oil (ELO) was synthesized and functionalized with propargylamine (PA) or 3-ethynylaniline (EA) and the products were crosslinked to obtain the diacetylene-functionalized epoxidized linseed oil polymers which were used as matrices in the preparation of the composites with multiwalled carbon nanotubes (MWCNTs). Electrical resistance at percentages between 4 and 20 wt/wt% of filler was measured and the percolation threshold was calculated, obtaining 1.2 and 1.7% for the composites with EA and PA respectively. Low critical concentration evidenced a good dispersion of the MWCNTs without necessity of any modification. The final products were used in the sensing of acetone, chloroform and ethanol. The electrical resistance changes were measured at different concentrations and the sensibility was calculated. In order to improve stability toward the vapors, composites were irradiated with gamma rays and new sensing was done and compared. The results showed differences in sensibility, selectivity and reproducibility.CONACy

An approach for shipping emissions estimation in ports: the case of ro–ro vessels in port of Vigo

Despite most atmospheric emissions being produced by vessels when navigating at sea, they are also important when in port because of their proximity to urban areas and their harmful effects on climate change and health. First, we carried out a bibliographical review of the nine most relevant methods to estimate the emission of ships in ports. These methods have been used to estimate the emissions of the sixteen most representatives Ro–Ro (roll-on–roll-off) ships calling at the Port of Vigo. From the results obtained, a new simplified method for estimation is proposed, which is based on linear regression curves and takes into account the number of ships and the average number of hours they remain in port annually. This simplification could be a useful tool when making preliminary assessments of the emissions from ships in port, which can also be extrapolated to other ports or types of ships.Ministerio de Ciencia e Innovación | Ref. PID2021-127876OB-I0

MODELO DE FACHADA VENTILADA CON DESECANTE PARA ACONDICIONAMIENTO DEL AIRE EXTERIOR DE VENTILACIÓN

Los sistemas de climatización y ventilación de edificios deben garantizar la calidad del aire interior y unas condiciones de temperatura y humedad que proporcione a los ocupantes un ambiente confortable y saludable, tal y como se recoge en el Código Técnico de la Edificación [1]. Con este fin, los materiales desecantes son utilizados en las unidades de tratamiento de aire. Combaten, en climas húmedos, la elevada carga latente de la zona, y son regenerados con aire caliente a partir de 50-60ºC, lo suficientemente bajo para que el calor lo proporcione un colector solar plano. En este trabajo se sustituye la rueda desecante convencional y se propone un nuevo diseño de una fachada ventilada, a la que se adhiere el material desecante. El aire de ventilación circula a través de la cámara de aire de la fachada, poniéndose en contacto con el material desecante, con el que transfiere masa y energía y, posteriormente, se somete a un tratamiento en una climatizadora convencional (batería de frío, enfriamiento evaporativo…) para ser impulsado a la zona. Cuando el desecante se satura y no puede adsorber más humedad, el sistema de fachada dispone de un captador solar que calienta el aire exterior hasta la temperatura necesaria para su regeneración. El diseño de dos columnas de fachada desecante permite alternar los modos de adsorción y desorción sin que se interrumpa el caudal de aire de ventilación. Planteadas las hipótesis, se desarrolla un modelo de la transferencia de calor y masa en la fachada. Se presenta el estudio de la simulación del caso base. Un estudio posterior permitirá la optimización de los parámetros más importantes: tipo de panel exterior, tipo y características del desecante y geometría del sistema, además del comportamiento para diferentes condiciones exteriores (aire y radiación solar).El trabajo se encuadra en el proyecto FAVEDES, financiado por la Secretaría de Estado de I+D+I del Ministerio de Economía y Competitividad dentro de la convocatoria INNPACTO 2011 y cuenta con la participación de Instituto Andaluz de Tecnología, Tecnalia, Grupo de Energética de la Universidad de Málaga, Astrawall Ibérica, b720 Arquitectos y Negarra

Validity of a Clinical Scale in Predicting the Failure of Non-Invasive Ventilation in Hypoxemic Patients

Introduction: The HACOR scale is a clinical score that can predict early failure of NIV in hypoxemic acute respiratory failure (ARF) The aim of this study is to analyze the validity of the HACOR scale. Methods: A retrospective study of a cohort of over 2749 episodes on 2711 consecutive patients requiring NIV for hypoxemic ARF in a polyvalent intensive care unit. The scale was measured before starting NIV and at 1, 6, 12, 24 and 48 h after the initiation of NIV. Results: NIV failure occurred in 963 patients (35%). The value of the HACOR scale before NIV did not differ between success and failure. However, at 1, 6, 12, 24 and 48 h of NIV, the scale values clearly differed between the two groups. The HACOR scale at NIV initiation accurately predicts NIV failure in the first hour, with an optimal cut-off value of 8 points. The AUC for predicting NIV failure with HACOR at 1 h is greater than 0.9 in patients with pneumonia and adult respiratory distress syndrome (ARDS). Conclusions: The HACOR scale measured at 1 h after NIV initiation accurately predicts NIV failure, especially in pneumonia and ARDS.info:eu-repo/semantics/publishedVersio

Modelling and design of a hybrid solar+micro-cogeneration system for water heating

Se analiza el interés de combinar la microcogeneración con la producción solar térmica para preparar ACS en un edificio de viviendasUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tec