In situ optimization methodology for the water circulation pumps frequency of ground source heat pump systems: Analysis for multistage heat pump units

[EN] In order to optimize the global energy performance of a ground source heat pump system, special attention needs to be paid to the auxiliaries as they stand for a considerable part of the total energy consumption. A new in situ experimental methodology based on the frequency variation of the water circulation pumps in order to optimize the energy performance of the system was previously published by the authors for a ground source heat pump system using a single stage heat pump with ON/OFF regulation. The original single stage heat pump was recently replaced with a multistage unit consisting of two compressors of the same capacity working in tandem. A new experimental campaign was carried out and a new study was performed in order to adapt the in situ optimization methodology to the performance of the tandem compressors unit, and, by extension, to the multistage case. This paper presents the in situ optimization methodology for the water circulation pumps frequency adapted for multistage ground source heat pump systems. Results show that energy savings up to 32% can be obtained by applying this optimization methodology.This work was supported by the "Programa de Ayudas de Investigacion y Desarrollo (PAID)" of the Universitat Politecnica de Valencia. This work was also supported by the European FP7 project "Advanced ground source heat pump systems for heating and cooling in Mediterranean climate" (GROUND-MED).Cervera Vázquez, J.; Montagud Montalvá, CI.; Corberán Salvador, JM. (2015). In situ optimization methodology for the water circulation pumps frequency of ground source heat pump systems: Analysis for multistage heat pump units. Energy and Buildings. 88:238-247. https://doi.org/10.1016/j.enbuild.2014.12.008S2382478

A computational methodology to account for the liquid film thickness evolution in Direct Numerical Simulation of prefilming airblast atomization

Prefilming airblast atomization is widely used in aero engines. Fundamental studies on the annular configuration of airblast atomizers are difficult to realize. For this reason, researchers focused on planar configurations. In this regard, the Karlsruhe Institute of Technology (KIT) developed a test rig to conduct experimental activities, conforming a large database with results for different conditions. Such data allow validation of two-phase flow calculations concerning primary atomization on these devices. The present investigation proposes a Direct Numerical Simulation (DNS) on the KIT planar configuration through the Volume of Fluid (VOF) method within the PARIS code. The novelty compared to DNS reported in the literature resides in the use of a boundary condition that accounts not only for the gas inflow turbulence but also for the spatio-temporal evolution of the liquid film thickness at the DNS inlet and its effect on turbulence. The proposed methodology requires computing precursor single-phase and two-phase flow Large-Eddy Simulations. Results are compared to DNS that only account for a constant (both timewise and spanwise) liquid film thickness at the domain inlet, validating the workflow. The proposed methodology improves the qualitative description of the breakup mechanism, as its different stages (liquid accumulation behind the prefilmer edge, bag formation, bag breakup, ligament formation and ligament breakup) coexist spanwise for a given temporal snapshot. This implies more continuous atomization than the one predicted by the constant film thickness case, which showed the same breakup stage to be present along the prefilmer span for a given instant and led to a more discretized set of atomization events. The proposed workflow allows quantifying the influence of the liquid film flow evolution above the prefilmer on primary breakup frequency and atomization features.Comment: Preprint submitted to International Journal of Multiphase Flo

Seasonal performance assessment of sanitary hot water production systems using propane and CO2 heat pumps

[EN] This paper presents an experimental analysis and performance evaluation of a ground source heat pumpsystem providing heating/cooling to an office building, located at the Universitat Politècnica de Valènciain Spain. The experimental data and a detailed description of the analysis tool used were presented ina previous paper for the first six operational years. This paper provides the adaptation of such analysistool to the new configuration (heat pump with two compressors working in tandem), and provides anupdated complete reference data sets over more than eleven years which can be used by researchers formodel validation purposes.The work of M. Tammaro on electric heat pumps is supported by the Next Heat Pump Generation project (funded by the European Commission in the 7th Framework Programme, grant number 307169 - European Heat Pump Association, 2013), which is gratefully acknowledged.Tammaro, M.; Montagud, C.; Corberán, J.; Mauro, A.; Mastrullo, R. (2017). Seasonal performance assessment of sanitary hot water production systems using propane and CO2 heat pumps. International Journal of Refrigeration. 74:222-237. https://doi.org/10.1016/j.ijrefrig.2016.09.0262222377

Partialization losses of ON/OFF operation of waterto- water refrigeration/heat-pump units

[EN] This paper presents the results of an experimental campaign for the characterization of the dynamic behavior of a water-to-water refrigeration/heat-pump unit under ON/OFF operation. The unit was previously tested at different water inlet temperatures under steady state conditions, and a very good agreement was found between the instantaneous dynamic performance of the heat pump and the corresponding quasi-steady state operation. In parallel, a series of tests were carried out to quantify the coefficient of performance (COP) degradation as a function of the load ratio, and a simple formula for the Part Load Factor is presented. Results lead to the conclusion that the only non-negligible factor in the COP degradation is the stand-by electrical consumption during the OFF period, especially at low load ratios. Finally, it is concluded that the minimization of the stand-by consumption is a key point for the future improvement of the seasonal performance of water-to-water systems.This research has been partially funded by the European FP7 framework project "Advanced ground source heat pump systems for heating and cooling in Mediterranean climate" (GROUND-MED) and the Spanish Ministry of Economy and Competitiveness (MINECO) through the project "Estudio de evaporadores y condensadores basados en tecnologia de minicanales para su aplicaciOn en equipos de aire acondicionado, refrigeraciOn y bomba de calor estacionarios" with reference DPI2011-26771-C02-01. The authors gratefully acknowledge their financial support.Corberán, JM.; D.Donadello; Martínez Galván, IO.; Montagud, C. (2013). Partialization losses of ON/OFF operation of waterto- water refrigeration/heat-pump units. International Journal of Refrigeration. 36(8):2251-2261. https://doi.org/10.1016/j.ijrefrig.2013.07.002S2251226136

In situ optimization methodology for ground source heat pump systems: Upgrade to ensure user comfort

[EN] Ground source heat pump systems have been proved to be one of the most efficient systems for heating and cooling in buildings. However, an optimal energy performance depends on a good control of the auxiliaries, which stand for an important part of the total energy consumption. The authors previously developed an experimental in situ optimization methodology for the water circulation pumps frequency of ground source heat pump systems when single stage and multi-stage ON/OFF regulation is employed. However, the user comfort was not completely met under extreme weather conditions during summer. This paper presents the upgrading of this energy optimization strategy combining circulation pumps frequency variation and building supply temperature compensation in order to ensure the user comfort while keeping high energy savings. Experimental results show that the user comfort is met by means of this new methodology and the energy savings (33%) are even higher than those obtained with the previous methodology. (C) 2015 Elsevier B.V. All rights reserved.This work was supported by the "Programa de Ayudas de Investigacion y Desarrollo (PAID)" of the Universitat Politecnica de Valencia. This work was also supported by the European FP7 project "Advanced ground source heat pump systems for heating and cooling in Mediterranean climate" (GROUND-MED).Cervera Vázquez, J.; Montagud Montalvá, CI.; Corberán Salvador, JM. (2015). In situ optimization methodology for ground source heat pump systems: Upgrade to ensure user comfort. Energy and Buildings. 109:195-208. https://doi.org/10.1016/j.enbuild.2015.10.026S19520810

Role of mTOR-regulated autophagy in spine pruning defects and memory impairments induced by binge-like ethanol treatment in adolescent mice

Adolescence is a brain maturation developmental period during which remodeling and changes in synaptic plasticity and neural connectivity take place in some brain regions. Different mechanism participates in adolescent brain maturation, including autophagy that plays a role in synaptic development and plasticity. Alcohol is a neurotoxic compound and its abuse in adolescence induces neuroinflammation, synaptic and myelin alterations, neural damage and behavioral impairments. Changes in synaptic plasticity and its regulation by mTOR have also been suggested to play a role in the behavioral dysfunction of binge ethanol drinking in adolescence. Therefore, by considering the critical role of mTOR in both autophagy and synaptic plasticity in the developing brain, the present study aims to evaluate whether binge ethanol treatment in adolescence would induce dysfunctions in synaptic plasticity and cognitive functions and if mTOR inhibition with rapamycin is capable of restoring both effects. Using C57BL/6 adolescent female and male mice (PND30) treated with ethanol (3 g/kg) on two consecutive days at 48-hour intervals over 2 weeks, we show that binge ethanol treatment alters the density and morphology of dendritic spines, effects that are associated with learning and memory impairments and changes in the levels of both transcription factor CREB phosphorylation and miRNAs. Rapamycin administration (3 mg/kg) prior to ethanol administration restores ethanol-induced changes in both plasticity and behavior dysfunctions in adolescent mice. These results support the critical role of mTOR/autophagy dysfunctions in the dendritic spines alterations and cognitive alterations induced by binge alcohol in adolescence

In situ optimization methodology for the water circulation pumps frequency of ground source heat pump systems

[EN] This paper presents an experimental study of the influence of the water circulation pumps frequency atthe indoor and outdoor loops in the overall system performance of a ground source heat pump moni-tored plant, and describes a three steps new methodology to optimize the system energy performanceand obtain the values of the optimal frequencies when ON/OFF regulation is employed. The first stepconsists of several experimental tests of pseudo-random sequence of frequency steps for both, internaland external circulation pumps, carried out during a single day. The second step is the characterization ofthe quasi-steady state system performance as a function of circulation pumps frequencies. The final stepconsists of, by means of an analytical expression, the extrapolation of results to any partial load ratio,what allows finding the optimal frequency as a function of the instantaneous thermal load. The advantageof the proposed methodology is that it can be carried out on site and is able to consider the phenomenaoccurring at the heat pump and the ground source heat exchanger when the flow rates are varied. Themethodology can be applied to any installation incorporating variable speed circulation pumps. Resultsindicate large energy savings potential for this kind of installation.This work was supported by the European Commission under the FP7 framework project GROUND-MED: "Advanced ground source heat pump systems for heating and cooling in Mediterranean climate".Montagud Montalvá, CI.; Corberán Salvador, JM.; Montero Reguera, ÁE. (2014). In situ optimization methodology for the water circulation pumps frequency of ground source heat pump systems. Energy and Buildings. 68, A:42-53. https://doi.org/10.1016/j.enbuild.2013.09.030S425368,

Numerical modeling of ground thermal response with borehole heat exchangers connected in parallel

[EN] With bore fields for energy extraction and injection, it is often necessary to predict the temperature response to heat loads for many years ahead. Mathematical methods, both analytical and numerical, with different degrees of sophistication, are employed. Often the g-function concept is used, in which the borehole wall is assumed to have a uniform temperature and the heat injected is constant over time. Due to the unavoidable thermal resistance between the borehole wall and the circulating fluid and with varying heat flux along the boreholes, the concept of uniform borehole wall temperature is violated, which distorts heat flow distribution between boreholes. This aspect has often been disregarded. This paper describes improvements applied to a previous numerical model approach. Improvements aim at taking into account the effect of thermal resistance between the fluid and the borehole wall. The model employs a highly conductive material (HCM) embedded in the boreholes and connected to an HCM bar above the ground surface. The small temperature difference occurring within the HCM allows the ground to naturally control the conditions at the wall of all boreholes and the heat flow distribution to the boreholes. The thermal resistance between the fluid and the borehole wall is taken into account in the model by inserting a thermally resistive layer at the borehole wall. Also, the borehole ends are given a hemispherical shape to reduce the fluctuations in the temperature gradients there. The improvements to the HCM model are reflected in a changed distribution of the heat flow to the different boreholes. Changes increase with the number of boreholes. The improvements to the HCM model are further illustrated by predicting fluid temperatures for measured variable daily loads of two monitored GCHP installations. Predictions deviate from measured values with a mean absolute error within 1.1 and 1.6¿K.The Swedish Energy Agency is acknowledged for financing this project. The authors thank Massimo Cimmino (Ecole Polytechnique de Montreal, Canada) for contributing to the generation of a particular solution with his approach.Monzó Cárcel, PM.; Puttige, AR.; Acuña, J.; Mogensen, P.; Cazorla-Marín, A.; Rodríguez, J.; Montagud, C.... (2018). Numerical modeling of ground thermal response with borehole heat exchangers connected in parallel. Energy and Buildings. 172:371-384. https://doi.org/10.1016/j.enbuild.2018.04.057S37138417

COVID-19 vaccination at the University of Alicante (Spain): detection of neutralizing antibodies against SARS-CoV-2 by rapid serological test, a cross-sectional study

FUNDAMENTOS // Los anticuerpos neutralizantes frente al SARS-CoV-2 han resultado una herramienta eficaz para el análisis de la inmunidad generada frente a la COVID-19. Numerosos estudios de seroprevalencia realizados en diferentes colectivos han permitido trazar un mapa global sobre la cobertura vacunal mediante el uso de pruebas serológicas rápidas de inmunocromatografía de flujo lateral con fines clínicos y epidemiológicos. El objetivo de nuestro estudio fue determinar el grado de inmunidad frente al SARS-CoV-2 asociado a la presencia de anticuerpos neutralizantes en personal administrativo, docentes y estudiantes de la Universidad de Alicante, mediante un test serológico rápido, así como conocer su experiencia sobre la vacunación frente a la COVID-19. MÉTODOS // Se diseñó un estudio epidemiológico, transversal, basado en la prevalencia de anticuerpos frente a la proteína S (espícula o Spike) del SARS-CoV-2. Participaron un total de 888 personas. El estudio se llevó a cabo con un único test (6 de julio a 22 de julio de 2021). Mediante regresión logística se calcularon Odds Ratios ajustadas según sexo, edad, tipo de vacuna, número de dosis de vacuna recibidas, pauta completa de vacunación y haber padecido la COVID-19. RESULTADOS // Las vacunas recibidas mayoritariamente fueron Vaxzevria® y Comirnaty®, con un 73,3% entre ambas; el 67,2% presentó pauta completa. Los resultados del test rápido de anticuerpos neutralizantes OJABIO dieron un resultado positivo en el 61,4% de la muestra. La posibilidad de un resultado positivo en el test OJABIO estuvo fuertemente asociada a haber padecido la COVID-19, haber recibido dos dosis, estar vacunado con Spikevax® o Comirnaty® o pertenecer al grupo de dieciocho a veintinueve años. Un total de 712 sujetos respondieron a un cuestionario (80%) paralelo sobre los efectos adversos y las preferencias entre las distintas vacunas contra la COVID-19. CONCLUSIONES // El estado de vacunación frente a la COVID-19 en la comunidad universitaria a los seis meses de la puesta en marcha de las estrategias nacionales de inmunización refleja una baja cobertura asociada, a pesar de la excelente predisposición a vacunarse. Los test rápidos de anticuerpos neutralizantes (AcN) pueden ser de utilidad para orientar las estrategias de inmunización y para decidir el momento de administrar nuevas dosis de refuerzo.BACKGROUND // Neutralizing antibodies against SARS-CoV-2 have shown to be an effective tool for the analysis of the immunity generated against COVID-19. Numerous seroprevalence studies carried out in different groups have made it possible to draw a global map of vaccination coverage through the use of rapid lateral flow immunochromatography serological tests for clinical and epidemiological purposes. The objective of our study was to determine the degree of immunity against SARS-CoV-2 associated with the presence of neutralizing antibodies in administrative staff, teachers and students at the University of Alicante by means of a rapid serological test and to learn about their experience with vaccination against COVID-19. METHODS // A cross-sectional epidemiological study was designed, based on the prevalence of antibodies against the S protein (spike) of SARS-CoV-2. A total of 888 people participated. The study was carried out with a single test (July 6 to July 22, 2021). Using logistic regression, adjusted Odds Ratios were calculated according to sex, age, type of vaccine, number of vaccine doses received, complete vaccination schedule, and having had COVID-19. RESULTS // The vaccines received mostly were Vaxzevria® and Comirnaty®, with 73.3% between both, although 67.2% presented a complete regimen. The results of the OJABIO rapid neutralizing antibody test gave a positive result in 61.4% of the sample. There was a high association between the variables COVID-19 infection, two doses of vaccine, Spikevax® or Comirnaty® vaccine, and eighteen/twenty-nine years old group with a positive result on the OJABIO test. A total of 712 subjects answered the parallel survey (80%) on adverse effects and preferences between the different vaccines against COVID-19. CONCLUSIONS // The vaccination status against COVID-19 in the university community after six months of the start of national immunization strategies reflects low coverage despite the excellent willingness to get vaccinated. Neutralizing antibodies (NAb) rapid tests can be useful to guide immunization strategies and decide when to administer new booster doses