Research about Refrigerant Charge in Domestic Heat Pumps

[ES] Debido a la crisis climática, es necesario encontrar fuentes alternativas para la climatización de locales y la producción de agua caliente sanitaria (ACS). Las bombas de calor se presentan como una alternativa excelente para sustituir a las calderas y así poder reducir las emisiones de gases contaminantes. En obra nueva, si se dispone de acceso al terreno o a una masa de agua, las bombas de calor agua-agua o salmuera-agua son altamente recomendadas debido a sus numerosas ventajas. El principal problema que presentan las bombas de calor es el refrigerante que contienen, ya que en la actualidad no existe refrigerante que sea a la vez barato, seguro y con propiedades termodinámicas óptimas. La tendencia en el futuro cercano en bombas de calor utilizadas para la calefacción de locales es volver al uso de refrigerantes naturales como los hidrocarburos y las hidrofluorolefinas. Estos refrigerantes presentan problemas de seguridad debido a su inflamabilidad o toxicidad y es por eso que, en caso de carecer de medidas de seguridad adicionales, la cantidad de refrigerante está limitada. En esta tesis se presenta un trabajo experimental sobre una bomba de calor salmuera-agua trabajando con poca cantidad de R290. La campaña experimental fue pensada para obtener resultados beneficiosos sobre cuál es el actual potencial de este tipo de tecnología tras la limitación de la carga de refrigerante, para desarrollar formas de reducción de carga de refrigerante en los sistemas y para mejorar las simulaciones de predicción de la cantidad necesaria de refrigerante. La campaña experimental está dividida en dos partes, cada una enfocada en uno de los siguientes objetivos: la primera en conocer el actual comportamiento anual de esa bomba de calor y la segunda para desarrollar estrategias de reducción de carga de refrigerante. En cada campaña experimental se almaceno tanto los datos de funcionamiento como la cantidad de refrigerante que había en cada uno de los componentes. La instalación estaba equipada con las herramientas necesarias para la toma de datos durante el funcionamiento de la bomba de calor y también era capaz de sectorizarla asilando cada uno de los componentes para poder extraer y pesar el refrigerante y así conocer que cantidad había en cada zona. Con los datos recogidos, se ha podido observar diferencias entre la predicción de carga de refrigerante en los diferentes componentes y la medida experimentalmente, y también se ha encontrado alguna de las causas de esa discrepancia, pudiendo así corregir el modelo. Para ello, se ha desarrollado un modelo de compresor y al modelo existente de intercambiadores de calor se le ha añadido un volumen muerto de refrigerante. Con estos cambios la predicción ha mejorado notablemente en el modelo utilizado y en la actualidad se puede utilizar para conocer una aproximación del refrigerante necesario.[CA] A causa de la crisi climàtica, és necessari enden fonts alternatives per a la climatització dels locals i la endencia d'aigua calenta sanitaria (ACS). Les bombes de calor es presenten com una alternativa excel·lent per a substituir a les calderes i així poder reduir les emissions de gasos contaminants. En obra nova, si es disposa d'accés al terreny o a una massa d'aigua, les bombes de calor aigua-aigua o salmorra-aigua són endencia recomanades a causa dels seus nombrosos avantatges. El principal problema que presenten les bombes de calor és el refrigerant que contenen, ja que en l'actualitat no existeix refrigerant que siga alhora barat, segur i amb propietats termodinàmiques òptimes. La tendencia actual en bombes de calor utilitzades per a la calefacció d'espais, és tornar a l'ús de refrigerants naturals com els hidrocarburs i les hidrofluorolefines. Aquests refrigerants presenten problemes de seguretat a causa de la seua inflamabilitat o toxicitat i és per això que, en cas de mancar de mesures de seguretat addicionals, la quantitat de refrigerant està limitada. En aquesta tesi es presenta un treball experimental sobre una bomba de calor salmorra-aigua treballant amb poca quantitat de R290. La campanya experimental va ser pensada per a obtindre resultats beneficiosos sobre quin és l'actual potencial d'aquesta mena de tecnologia després de la limitació de la càrrega de refrigerant, per a desenvolupar formes de reducció de càrrega de refrigerant en els sistemes i per a millorar les simulacions de predicció de la quantitat necessària de refrigerant. La campanya experimental està dividida en dues parts, cadascuna enfocada en un dels següents objectius: la primera a conéixer l'actual comportament anual d'aqueixa bomba de calor i la segona per a desenvolupar estratègies de reducció de càrrega de refrigerant. En cada campanya experimental s'emmagatzeme tant les dades de funcionament com la quantitat de refrigerant que hi havia en cadascun dels components. La instal·lació estava equipada amb les eines necessàries per a la presa de dades durant el funcionament de la bomba de calor i també era capaç de sectoritzar-la asilant cadascun dels components per a poder extraure i pesar el refrigerant i així conéixer que quantitat hi havia en cada zona. Amb les dades recollides, s'ha pogut observar diferències entre la predicció de càrrega de refrigerant i la mesura experimentalment, i també s'ha trobat alguna de les causes d'aqueixa discrepància, podent així corregir el model. Per a això, s'ha desenvolupat un model de compressor i al model existent de bescanviadors de calor se li ha afegit un volum mort de refrigerant. Amb aquests canvis la predicció ha millorat notablement i en l'actualitat es pot utilitzar per a conéixer una aproximació del refrigerant necessari.[EN] Due to the climate crisis, there is a need to find alternative energy sources for space heating, cooling, and domestic hot water (DHW) production. Heat pumps are an excellent alternative to substitute current boilers to reduce gas emissions. A liquid source heat pump is highly recommended in new buildings with access to land or water due to its significant advantages. The main problem with this technology is that it uses a refrigerant inside, and there is no refrigerant with good performance, cheap and safe to handle. The near future trend in heat pumps used for space heating is to use pure refrigerants such as natural refrigerants and HFOs. These refrigerants (except CO2) have safety issues (flammability or toxicity); consequently, a maximum amount of refrigerant is allowed without considering extra safety measures. This PhD presents an experimental work with a ground source heat pump (GSHP) with a low R290 refrigerant amount. This experimental campaign is helpful to know the current achievable performance derived from the limitation of refrigerant amount, to develop refrigerant charge reduction strategies and to improve existing simulation software based on refrigerant charge prediction. The experimental campaign was divided into two parts to focus separately on normal annual behaviour and refrigerant charge reduction strategies. In each test campaign, performance data was recorded during the test, and the refrigerant charge amount in each component was extracted and weighed after the end of each test. The installation had the tools to acquire data from the vapour compression circuit, isolate the components, and extract and weigh the refrigerant to know how much refrigerant was inside each section. With the data collected, it was observed that the differences in refrigerant charge prediction in the components with the software used were significant, and some causes of these differences have been identified, correcting the prediction model. So, a compressor model has been developed, and a dead volume has been added to the refrigerant charge calculation in heat exchangers. With these changes, the refrigerant prediction has greatly improved in the model used and could be a reliable approximation.Gracias a la Universitat Politècnica de València por brindarme la financiación y los medios a través del programas “Ayudas para movilidad de estudiantes de Doctorado de la Universitat Politècnica de València” y “Programa de Ayudas de investigación y Desarrollo” (PAID-01-17)Sánchez-Moreno Giner, L. (2023). Research about Refrigerant Charge in Domestic Heat Pumps [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/19678

Refrigerant charge prediction fluctuations in the scop campaign of a brine-water heat pump

The refrigerant amount reduction is a matter of increasing importance because of the rise in prices of current hydrofluorocarbons and the safety reasons of the leading natural alternatives. There is no space for the refrigerant deposit in vapour compression cycles with refrigerant charge optimised; consequently, it is essential to know which refrigerant charge will make the vapour compression cycle work with the best performance during a year. In this work, a simulation of the different tests of the seasonal COP campaign for a brine-water heat pump is performed using the software IMST-ART. With the results, it can be possible to understand the different behaviour of the heat pump during the year and guess the best criteria to establish the optimum refrigerant charge.The authors are grateful to the Programa de Ayudas de Investigacion y Desarrollo (PAID-01- 17) to partially finance this research. As well, this publication has been carried out in the framework of the project “DECARBONIZACIÓN DE EDIFICIOS E INDUSTRIAS CON SISTEMAS HÍBRIDOS DE BOMBA DE CALOR”, funded by the Spanish “Ministerio de Ciencia e Innovación (MCIN) with code number PID2020- 115665RB-I00

Comparative study of the performance of a heat pump for heating with R410A and R32 as refrigerant, using the software IMST-ART

[EN] According to the European Commission, at this moment, heating and cooling in buildings account for half of the energy consumption, while only a 16% of the energy used in this issue is obtained employing renewable sources. One of the possible solutions to improve the current situation is the use of heat pumps for the air conditioning of buildings. However, the refrigerants used at this moment are hydrofluorocarbons (HFCs) and they have a global warming potential (GWP) elevated so that new refrigerants which can substitute the current ones are being searched. The most used refrigerant for heating applications is the R410A, which is a mixture of HFCs. Its immediate retrofit is one of its components, the R32, due to the compatibility of both refrigerants with the materials and its similar performance. Furthermore, the R32 has a value of GWP approximately of a third of the R410 s value. The objective of this work is to evaluate the main differences between the results obtained with both refrigerants and to find out the main changes to be done to obtain at least the same performance. In this work, a model of IMST-ART of an air-water heat pump is presented using both refrigerants. In the model, both refrigerants are evaluated for different conditions of heating at low temperature. Lately, a summary of changes is proposed in order to cover the same functions, or more, than the original heat pump.Luis Sánchez-Moreno-Giner acknowledges the Research and Development Aid Program (PAID01-17) of the Universitat Politècnica de València for receiving the Research Fellowship FPIUPV-2017.Sánchez-Moreno-Giner, L.; López-Juárez, E.; Gonzálvez-Maciá, J. (2019). Comparative study of the performance of a heat pump for heating with R410A and R32 as refrigerant, using the software IMST-ART. Universidad de Castilla-La Mancha José Antonio Almendros Ibáñez. 1135-1143. http://hdl.handle.net/10251/180704S1135114

Thermodynamic assessment of ultra-low-global warming potential refrigerants for space and water heaters

[EN] The current paper studies the most suitable ultra-low-global warming potential (GWP) (GWP < 30) candidates in the market, considering also its grade of flammability and toxicity, for heat pumps employed for different space heating and domestic hot water (DHW) applications. A pre-design thermodynamic model has been developed to evaluate the performance and size limits for any subcritical or transcritical heat pump under certain working conditions. This generic model is based on the pinch point approach, so it does not depend on a certain type of heat exchangers, it only depends on the external working conditions. The results showed that all subcritical ultra-low-GWP, nonflammable, and nontoxic refrigerants considered have either lower coefficient of performance (COP) or volumetric heating capacity (VHC) compared with the reference high-GWP refrigerants R-410A and R-134a. Additionally, the only refrigerants with higher COP, such as R-717 (ammonia) or R-290 (propane), are either extremely flammable or toxic. For the applications need of high water-side temperature lift, the transcritical refrigerants R-744 (CO2) and R-170 (ethane) showed the best performance, regarding both COP and VHC values, of all the refrigerants studied. The refrigerants R-161, R-1270 (propylene), and R-1234yf presented a balanced performance in both space heating and DHW applications. This makes them potential candidates to be employed in subcritical multi-temperature levels heat pumps.This work was partially supported by the Research and Development Aid Program (PAID-01-17) of the Universitat Politecnica de Valencia for receiving the Research Fellowship FPI-UPV-2017. The authors also would like to acknowledge the financial support provided by the Ministerio de Ciencia, Innovacion y Universidades de Espana for the project "Maximizacion de la eficiencia y minimizacion del impacto ambiental de bombas de calor para la descarbonizacion de la calefaccion/acs en los edificios de consumo casi nulo" (ENE2017-83665-C2-1-P).Sánchez-Moreno-Giner, L.; López-Juárez, E.; Gonzálvez-Maciá, J.; Hassan, A. (2020). Thermodynamic assessment of ultra-low-global warming potential refrigerants for space and water heaters. Heat Transfer Research. 51(14):1317-1335. https://doi.org/10.1615/HeatTransRes.2020035317S13171335511

Experimental and Theoretical Analysis of Refrigerant Charge Extraction Methods

According to the European Commission, heating, cooling and domestic hot water (DHW) production implies 79% of the total energy consumed in households. Moreover, as 84% of this energy is still generated from fossil fuels, it is required taking measures in order to improve the current situation. One way to increase the decarbonization in households is the use of heat pumps powered by renewable energy sources. Additionally, the energy captured by heat pumps is considered renewable when a certain efficiency value is achieved (2009/28/CE directive). Nowadays, refrigerants used by heat pumps are mainly hydrofluorocarbons (HFCs) which have a high global warming potential (GWP) and have a clear deadline defined at F-Gas EU Regulation 517/2014. For this reason, natural refrigerants will play an important role within heating, cooling and DHW production at the household sector. However, most of the natural refrigerants with acceptable thermodynamic properties are at least slightly flammable or toxic, and its use has an associated risk due to this condition. That is the cause that the amount of refrigerant charge must comply with the maximum refrigerant charge limited by regulations, and the prediction of the nominal refrigerant charge amount inside a heat pump has become an important matter within the design process of a heat pump. There already exist prediction models of refrigerant charge but, under certain conditions, they do not fit the reality. The current prediction methods which use simulation models may be improved by knowing the actual distribution of the refrigerant inside the different components of a real heat pump. In order to empirically determine the refrigerant charge amount inside each part of the heat pump, several methods can be used, but the most employed one is the “remove and weight” technique. This technique consists in extracting the refrigerant charge of each element of the heat pump in a sample cylinder in order to weight it, after isolating each component from another. A similar but less precise approach of this method is employed when recovering refrigerant in maintenance or decommissioning tasks. In this contribution, a theoretical and experimental study of different charge extraction methods is presented. In the study, every method has been analyzed according to different factors: percentage of refrigerant extracted, security measures employed, the time needed until stability is reached and cost of the technique. The results of this study will help in the selection of best extraction method according to the precision of the results needed, the available resources and the training of the staff which in the end will be performing the experiments

Avances en Informática y Automática. Decimocuarto workshop

[ES]El Máster Oficial en Sistemas Inteligentes de la Universidad de Salamanca tiene como principal objetivo promover la iniciación de los estudiantes en el ámbito de la investigación. El congreso organizado por el Departamento de Informática y Automática que se celebra dentro del Máster en Sistemas Inteligentes de la Universidad de Salamanca proporciona la oportunidad ideal para que sus estudiantes presenten los principales resultados de sus Trabajos de Fin de Máster y obtengan una realimentación del interés de los mismos. La decimocuarta edición del workshop “Avances en Informática y Automática”, correspondiente al curso 2019 - 2020, ha sido un encuentro interdisciplinar donde se han presentado trabajos pertenecientes a un amplio abanico de líneas de investigación, desde los sistemas multiagente y la visualización de la información hasta la minería de datos pasando por otros campos relacionados. Todos los trabajos han sido supervisados por investigadores de reconocido prestigio pertenecientes a la Universidad de Salamanca, proporcionando el marco idóneo para sentar las bases de una futura tesis doctoral. Entre los principales objetivos del congreso se encuentran: - Ofrecer a los estudiantes un marco donde exponer sus primeros trabajos de investigación. - Proporcionar a los participantes un foro donde discutir ideas y encontrar nuevas sugerencias de compañeros, investigadores y otros asistentes a la reunión. - Permitir a cada estudiante una realimentación de los participantes sobre su trabajo y una orientación sobre las futuras direcciones de investigación. - Contribuir al desarrollo del espíritu de colaboración en la investigación

Role of age and comorbidities in mortality of patients with infective endocarditis

[Purpose]: The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality. [Methods]: Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015.Patients were stratified into three age groups:<65 years,65 to 80 years,and ≥ 80 years.The area under the receiver-operating characteristic (AUROC) curve was calculated to quantify the diagnostic accuracy of the CCI to predict mortality risk. [Results]: A total of 3120 patients with IE (1327 < 65 years;1291 65-80 years;502 ≥ 80 years) were enrolled.Fever and heart failure were the most common presentations of IE, with no differences among age groups.Patients ≥80 years who underwent surgery were significantly lower compared with other age groups (14.3%,65 years; 20.5%,65-79 years; 31.3%,≥80 years). In-hospital mortality was lower in the <65-year group (20.3%,<65 years;30.1%,65-79 years;34.7%,≥80 years;p < 0.001) as well as 1-year mortality (3.2%, <65 years; 5.5%, 65-80 years;7.6%,≥80 years; p = 0.003).Independent predictors of mortality were age ≥ 80 years (hazard ratio [HR]:2.78;95% confidence interval [CI]:2.32–3.34), CCI ≥ 3 (HR:1.62; 95% CI:1.39–1.88),and non-performed surgery (HR:1.64;95% CI:11.16–1.58).When the three age groups were compared,the AUROC curve for CCI was significantly larger for patients aged <65 years(p < 0.001) for both in-hospital and 1-year mortality. [Conclusion]: There were no differences in the clinical presentation of IE between the groups. Age ≥ 80 years, high comorbidity (measured by CCI),and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in the <65-year group

CARB-ES-19 Multicenter Study of Carbapenemase-Producing Klebsiella pneumoniae and Escherichia coli From All Spanish Provinces Reveals Interregional Spread of High-Risk Clones Such as ST307/OXA-48 and ST512/KPC-3

ObjectivesCARB-ES-19 is a comprehensive, multicenter, nationwide study integrating whole-genome sequencing (WGS) in the surveillance of carbapenemase-producing K. pneumoniae (CP-Kpn) and E. coli (CP-Eco) to determine their incidence, geographical distribution, phylogeny, and resistance mechanisms in Spain.MethodsIn total, 71 hospitals, representing all 50 Spanish provinces, collected the first 10 isolates per hospital (February to May 2019); CPE isolates were first identified according to EUCAST (meropenem MIC &gt; 0.12 mg/L with immunochromatography, colorimetric tests, carbapenem inactivation, or carbapenem hydrolysis with MALDI-TOF). Prevalence and incidence were calculated according to population denominators. Antibiotic susceptibility testing was performed using the microdilution method (EUCAST). All 403 isolates collected were sequenced for high-resolution single-nucleotide polymorphism (SNP) typing, core genome multilocus sequence typing (cgMLST), and resistome analysis.ResultsIn total, 377 (93.5%) CP-Kpn and 26 (6.5%) CP-Eco isolates were collected from 62 (87.3%) hospitals in 46 (92%) provinces. CP-Kpn was more prevalent in the blood (5.8%, 50/853) than in the urine (1.4%, 201/14,464). The cumulative incidence for both CP-Kpn and CP-Eco was 0.05 per 100 admitted patients. The main carbapenemase genes identified in CP-Kpn were blaOXA–48 (263/377), blaKPC–3 (62/377), blaVIM–1 (28/377), and blaNDM–1 (12/377). All isolates were susceptible to at least two antibiotics. Interregional dissemination of eight high-risk CP-Kpn clones was detected, mainly ST307/OXA-48 (16.4%), ST11/OXA-48 (16.4%), and ST512-ST258/KPC (13.8%). ST512/KPC and ST15/OXA-48 were the most frequent bacteremia-causative clones. The average number of acquired resistance genes was higher in CP-Kpn (7.9) than in CP-Eco (5.5).ConclusionThis study serves as a first step toward WGS integration in the surveillance of carbapenemase-producing Enterobacterales in Spain. We detected important epidemiological changes, including increased CP-Kpn and CP-Eco prevalence and incidence compared to previous studies, wide interregional dissemination, and increased dissemination of high-risk clones, such as ST307/OXA-48 and ST512/KPC-3

Spatiotemporal Characteristics of the Largest HIV-1 CRF02_AG Outbreak in Spain: Evidence for Onward Transmissions

Background and Aim: The circulating recombinant form 02_AG (CRF02_AG) is the predominant clade among the human immunodeficiency virus type-1 (HIV-1) non-Bs with a prevalence of 5.97% (95% Confidence Interval-CI: 5.41–6.57%) across Spain. Our aim was to estimate the levels of regional clustering for CRF02_AG and the spatiotemporal characteristics of the largest CRF02_AG subepidemic in Spain.Methods: We studied 396 CRF02_AG sequences obtained from HIV-1 diagnosed patients during 2000–2014 from 10 autonomous communities of Spain. Phylogenetic analysis was performed on the 391 CRF02_AG sequences along with all globally sampled CRF02_AG sequences (N = 3,302) as references. Phylodynamic and phylogeographic analysis was performed to the largest CRF02_AG monophyletic cluster by a Bayesian method in BEAST v1.8.0 and by reconstructing ancestral states using the criterion of parsimony in Mesquite v3.4, respectively.Results: The HIV-1 CRF02_AG prevalence differed across Spanish autonomous communities we sampled from (p &lt; 0.001). Phylogenetic analysis revealed that 52.7% of the CRF02_AG sequences formed 56 monophyletic clusters, with a range of 2–79 sequences. The CRF02_AG regional dispersal differed across Spain (p = 0.003), as suggested by monophyletic clustering. For the largest monophyletic cluster (subepidemic) (N = 79), 49.4% of the clustered sequences originated from Madrid, while most sequences (51.9%) had been obtained from men having sex with men (MSM). Molecular clock analysis suggested that the origin (tMRCA) of the CRF02_AG subepidemic was in 2002 (median estimate; 95% Highest Posterior Density-HPD interval: 1999–2004). Additionally, we found significant clustering within the CRF02_AG subepidemic according to the ethnic origin.Conclusion: CRF02_AG has been introduced as a result of multiple introductions in Spain, following regional dispersal in several cases. We showed that CRF02_AG transmissions were mostly due to regional dispersal in Spain. The hot-spot for the largest CRF02_AG regional subepidemic in Spain was in Madrid associated with MSM transmission risk group. The existence of subepidemics suggest that several spillovers occurred from Madrid to other areas. CRF02_AG sequences from Hispanics were clustered in a separate subclade suggesting no linkage between the local and Hispanic subepidemics