Optimization of Solar Thermal Plants, Transient Analysis and Design of Eccentric Bayonet Receivers

Mención Internacional en el título de doctorOver recent decades, solar energy has gained a prominent position as an efficient way to produce electricity from sustainable resources, reducing dependence on fossil fuels in the energy production sector. One of the most promising solar technologies is Concentrating Solar Power (CSP). The operation of CSP plants is based on the use of mirrors that concentrate the sunlight onto an absorbing element. A heat transfer fluid circulates inside the absorbing element, collecting the heat and transferring it to a power cycle for electricity generation or to a relevant industrial heating application. The Solar Power Tower (SPT) is outstanding among current CSP technologies since it offers high thermal efficiency and the possibility of extending hours of operation thanks to thermal storage, which provides stability and flexibility to electricity generation, compared to variable renewable energy technologies, such as photovoltaic and wind energy. One of the most critical systems in SPT plants is the receiver, the demanding operating conditions of which may reduce its lifespan drastically. Practical considerations related to the maturing of these technologies and their operation mean they are far from realizing their theoretical potential exploitation. For this reason, it is necessary to continue developing this technology, reducing its cost compared to conventional technologies based on fossil resources and guaranteeing it operates safely. This doctoral thesis aims to contribute to optimizing SPT plants through a broad set of theoretical and simulation studies focused on improving tubular solar receivers. For this goal, the thesis develops a series of models and thermo-fluidic simulations (Computational Fluid Mechanics, CFD) as well as mechanical simulations (Finite Element Analysis, FEM) that take into account the main heat transfer effects existing in the receiver tubes during their operation, in order to characterize their thermo-mechanical behavior and analyze the most demanding situations for the receiver. Firstly, this doctoral dissertation numerically analyzes the preheating of an external tubular receiver that operates with nitrate molten salt (i.e., solar salt), which is the type of heat transfer fluid (HTF) usually employed in external tubular receivers. For this study, two numerical models with different degrees of simplification were developed to analyze the temporal evolution of thermal stresses and the fatigue damage generated in the receiver tubes during their preheating. In particular, this analysis was carried out for two receivers of different sizes, allowing the influence of the tube diameter on preheating to be evaluated. The results show that, since the tubes are empty of solar salt during preheating, the rear side of the tubes is heated mainly by circumferential heat conduction in tube walls. This explains why the maximum stresses of the receiver tubes, generated by the non-uniform temperature distribution inside the tube walls, are obtained during the first minutes of preheating and their values increase with the tube’s diameter. The fatigue damage produced during preheating for the two receivers analyzed shows that their start-up is safe. Additionally, these models demonstrate that the preheating strategy allows sufficient temperature to be achieved to fill the receiver with nitrate salt without freezing risk. For the next generation of SPT plants, the use of supercritical CO2 Brayton cycles in the power block forces us to work with temperatures above 700 ºC for an efficient operation of cycle. Due to the fact that the nitrate salt degrades above 600 ºC, alternative HTFs that withstand higher temperatures must be selected, such as molten carbonate and chloride salts. In this doctoral thesis, the creep and fatigue damage and the feasibility of preheating a receiver for these high-temperature salts are studied. The results indicate that the receiver tubes can be preheated above the freezing temperature of these salts, which is higher than that of the nitrate salt. However, starting up high-temperature salt receivers entails a longer preheat time, reducing the plant’s operating time. This fact, combined with the larger heat losses of the receiver due to its operation at a higher temperature, requires elevated efficiencies (i.e. <= 50%) of the power cycle to improve the overall efficiency of the electricity production of an SPT plant. In general, the majority of the thermal models of SPT receivers simplify the complex heat transfer process through certain hypotheses. In this thesis, the validity of two of these hypotheses is analyzed using three-dimensional numerical models with different degrees of simplification. These hypotheses are radial conduction in the tube walls and the use of a uniform convective coefficient, both axially and circumferentially, for the nitrate salt inside the tubes. The results show that these hypotheses do not significantly affect the temperature distribution of tubes for the typical operating conditions of solar thermal receivers. In addition, this thesis demonstrates the need to model the mechanical properties of the tube as temperature-dependent variables to accurately obtain the thermal stresses of the receiver tubes and the damage associated with their operation, which is a crucial aspect in the receiver design. Finally, this doctoral dissertation evaluates, numerically and analytically, the thermal and mechanical behavior of a bayonet tube applied to external tubular receivers as an alternative to simple tube receivers. A bayonet tube is composed of two tubes, one inside the other, thus creating two sections, circular and annular, through which the molten salt of the receiver sequentially flows. The results obtained show that thanks to this layout, the heat transfer of the molten salt inside the tube can be improved. Furthermore, the excessive overheating of the fluid is avoided since the heat absorbed by the outer tube is distributed between the flow of molten salt in the annular section and that of the circular section. As revealed by the simulations carried out, this effect is accentuated by the eccentricity between the centers of the inner and outer tubes of the bayonet tube. This offers additional degrees of freedom, leading to an optimum in the thermomechanical behavior of the receiver. Nevertheless, this thesis shows that it is necessary to combine the optimum designs with other technological and economic factors to make the bayonet tube receivers competitive with respect to simple tube receivers commonly used in SPT plants.La energía solar se ha posicionado en las últimas décadas como alternativa viable a los combustibles fósiles en la generación de electricidad y producción de calor a escala industrial. Una de las tecnologías más prometedoras es la energía solar de concentración (Concentrating Solar power, CSP), la cual se basa en la concentración de la radiación solar en elementos absorbedores mediante espejos. Dichos elementos absorbedores conforman el receptor solar y por su interior circula un fluido de trabajo encargado de recoger la radiación absorbida y transferirla en forma de energía térmica a un ciclo de potencia para producir electricidad o hacia la aplicación industrial pertinente. Las centrales termosolares de tipo torre (Solar Power Tower, SPT) destacan entre las tecnologías actuales de CSP ya que ofrecen una elevada eficiencia térmica y la posibilidad de extender su funcionamiento mediante el uso de almacenamiento térmico, el cual proporciona firmeza y flexibilidad a la generación de energía eléctrica en contraposición a las tecnologías de energía renovable intermitentes como las energías fotovoltaica y eólica. El receptor de las plantas SPT es uno de los elementos más críticos, debido a la elevada concentración de radiación que es reflejada en las paredes de los elementos absorbedores, normalmente tubos, y la corrosión generada por el fluido de trabajo. Debido a consideraciones prácticas relacionadas con la madurez de la tecnología y su operación, las centrales SPT todavía no han alcanzado su potencial y es necesario continuar desarrollando esta tecnología para reducir su coste y garantizar una operación segura. Esta tesis doctoral pretende contribuir a la optimización de las centrales termosolares de tipo torre a través de un conjunto de estudios teóricos y de simulación enfocados a la mejora de los receptores solares tubulares. Para ello, la tesis desarrolla una serie de modelos y simulaciones fluidotérmicas (Computational Fluid Mechanics, CFD) además de mecánicas (Finite Element Analysis, FEM) que tienen en cuenta los principales mecanismos de transferencia de calor existentes en los tubos receptores durante su operación para caracterizar su comportamiento termo-mecánico y analizar las situaciones más exigentes para el receptor. En primer lugar, la tesis estudia numéricamente el precalentamiento de un receptor tubular externo que opera con sal fundida de nitrato (i.e. sal solar) que es el tipo de fluido de trabajo (Heat Transfer Fluid, HTF) más usado en estos receptores. Para dicho estudio se desarrollan dos modelos bidimensionales con distintos grados de simplificación con el objetivo de analizar la evolución temporal de las tensiones térmicas y el daño a fatiga generado en los tubos receptores durante su precalentamiento. En particular, este análisis se realiza para dos receptores de distinto tamaño, lo que permite evaluar la influencia del diámetro del tubo en el precalentamiento. Los resultados muestran que, debido a que durante el precalentamiento los tubos se encuentran vacíos de sal solar, el calentamiento de la parte trasera de los tubos se realiza principalmente por medio de la conducción circunferencial del calor a través de las paredes de los tubos, partiendo de la parte delantera en donde la temperatura es máxima. Este hecho justifica que las máximas tensiones en la pared del tubo, generadas por la no uniformidad existente en su temperatura, se obtengan durante los primeros minutos del precalentamiento y se incrementen con el aumento del diámetro. El daño a fatiga obtenido durante el precalentamiento para los dos receptores analizados muestra que su arranque es totalmente seguro y permite alcanzar las temperaturas de pared necesarias para que no se congele la sal de nitrato una vez se introduzca. Sin embargo, en la próxima generación de centrales SPT, el uso de ciclos Brayton supercríticos de CO2 en el bloque de potencia obliga a trabajar con temperaturas superiores a las 700ºC para una operación eficiente del dicho ciclo. Este hecho obliga a la selección de nuevos fluidos de trabajo que soporten mayores temperaturas tales como las sales de carbonato o los cloruros fundidos, debido a que la sal de nitrato se degrada a partir de 600ºC. En esta tesis doctoral, se analiza la viabilidad de precalentar un receptor para estas sales de alta temperatura calculando el daño infligido en los tubos. Los resultados obtenidos indican que los tubos del receptor pueden precalentarse por encima de la temperatura de congelación de dichas sales, la cual es superior a la de la sal de nitrato. Sin embargo, el arranque de receptores para sales de alta temperatura conlleva un mayor tiempo de precalentamiento, reduciendo el tiempo de operación de la planta. Esto, sumado a las mayores pérdidas del receptor por operar a mayor temperatura, hace necesario que los rendimientos del bloque de potencia sean elevados (i.e. <= 50%) si se desea mejorar la eficiencia global de producción eléctrica de una planta SPT. Por lo general, las modelizaciones de los receptores solares están basados en modelos térmicos simplificados, sustentados bajo ciertas hipótesis que permiten simplificar parcialmente los complejos fenómenos de transferencia de calor involucrados en la operación del receptor. En esta tesis, se analizada la validez de dos de estas hipótesis mediante modelos numéricos tridimensionales con distinto grado de simplificación. Las hipótesis evaluadas son la conducción radial en las paredes del tubo y el uso de un coeficiente convectivo uniforme, tanto axial como circunferencialmente, para la sal de nitrato dentro de los tubos. Los resultados muestran que dichas hipótesis solo afectan sensiblemente a la distribución de temperaturas para las condiciones de operación típicas de los receptores termosolares. Además, se muestra que en los modelos es importante retener la dependencia con la temperatura de las propiedades mecánicas del material para obtener con suficiente precisión una estimación de las tensiones que soportan los tubos del receptor y del daño mecánico de los mismos, aspecto crucial para su adecuado diseño. Finalmente, la tesis evalúa numérica y analíticamente el comportamiento térmico y mecánico de los tubos bayoneta en su aplicación a receptores tubulares de torre y como alternativa al uso de receptores de tubos simples. Un tubo bayoneta está formado por dos tubos, uno dentro del otro, creando así dos secciones una circular y otra anular que son recorridas secuencialmente por la sal fundida del receptor. Los resultados obtenidos demuestran que, gracias a esta disposición, se puede mejorar la transferencia de calor de la sal fundida en el interior del tubo. Además, se evita el excesivo sobrecalentamiento del fluido ya que el calor absorbido por el tubo exterior se distribuye entre el flujo de sal fundida de la sección anular y el de la sección circular. Según revelan las simulaciones realizadas, este efecto es acentuado con la excentricidad entre centros de los tubos interior y exterior del tubo bayoneta, ofreciendo grados de libertad adicionales que dan lugar a un óptimo en el comportamiento termomecánico del receptor. Sin embargo, la tesis muestra que es necesario conjugar dicho óptimo con otros factores de tipo técnico y económico para que el uso de receptores de tubo bayoneta sea competitivo frente a los receptores de tubo simple convencionalmente usados en plantas SPT.Esta tesis doctoral ha sido desarrollada gracias al apoyo económico del Ministerio de Economía, Industria y Competitividad a través de "Ayudas para contratos predoctorales para la formación de doctores" (BES-2016-078455).Programa de Doctorado en Ingeniería Mecánica y de Organización Industrial por la Universidad Carlos III de MadridPresidente: Manuel Jesús Blanco Muriel.- Secretario:Celia Sobrino Fernández.- Vocal: Antonio Luis Ávila Marí

Estudio termoeconómico para la hibridación solar térmica de una central de ciclo combinado

En la sociedad actual se está desarrollando una nueva corriente de pensamiento orientada hacia un futuro más sostenible. Esta forma de pensar se debe por un lado al agotamiento de los combustibles fósiles y por otro lado al cambio climático. La dirección que se está siguiendo hacia este futuro sostenible es la utilización, cada vez mayor, de las energías renovables. El presente proyecto combina la utilización de las tecnologías actuales de producción de electricidad con energías renovables. Para ello se valorará la viabilidad termodinámica, medioambiental y económica de realizar una hibridación en una central térmica. La central escogida para realizar el estudio es la central de ciclo combinado Bèsos V, situada en Barcelona y que lleva en funcionamiento desde el año 2011. Para realizar la hibridación se utilizará energía solar, que será aprovechada a través del uso de colectores cilíndrico parabólicos. En los cuales se calculará la potencia térmica que pueden obtener en dicha localización, además del número de colectores que serían necesarios para satisfacer una determinada potencia térmica. Se estudiará la conexión entre el campo solar y el ciclo de potencia que ofrezca las mejores propiedades, con la potencia térmica del campo de colectores escogida. Observando que dicho punto se encuentra a la salida de la turbina de recalentamiento para las potencias estudiadas. Por último se estudiará la viabilidad económica y medioambiental de la hibridación, valorando si la implantación de este tipo de centrales es una alternativa aceptable en España.In today's society it is developing a new way of thinking, oriented to a more sustainable future. This way of thinking is due in part to the depletion of fossil fuels and secondly to climate change. The way is following towards this sustainable future is the use, increasingly, of renewable energy. This project combine the use of existing technologies for electricity production with renewable energies. To do thermodynamics, environmental and economic viability of hybridization in a power plant will be assessed. The central chosen for the study is the plant of combined cycle Bèsos V, located in Barcelona and has been operating since 2011. To make this hybridation will be used solar energy, which will be exploited through the use of parabolic trough collectors. In which the thermal power that can be obtained in this location and the number of collectors that would be required to meet a certain thermal power. Will be studied the connection between the solar field and power cycle that offers the best properties. Noting that best point is the output of the turbine reheat to potency studied. Finally the economic and environmental feasibility study of hybridization, assessing whether the implementation of such plants is an acceptable alternative in Spain.Ingeniería Mecánic

Non-destructive testing for the assessment of granite decay in heritage structures compared to quarry stone

Several types of granite found in two architectural heritage monuments were assessed with two non-destructive, portable techniques: Schmidt hammer rebound and ultrasound velocity (Vp). Similar assessments were conducted on the rock from which the granite was originally quarried for comparison. The results obtained, which revealed the existence of a direct correlation, constitute a useful indication of decay, particularly if the approximate dates of construction are known. And conversely, if they are not, such stone assessments may provide a rough estimate of when the structure was built. Both of these convenient, portable and non-destructive techniques may be used as reliable indicators of the degree of stone decay

Compliance validation and diagnosis of business data constraints in business processes at runtime

Business processes involve data that can be modified and updated by various activities at any time. The data involved in a business process can be associated with flow elements or data stored. These data must satisfy the business compliance rules associated with the process, where business compliance rules are policies or statements that govern the behaviour of a company. To improve and automate the validation and diagnosis of compliance rules based on the description of data semantics (called Business Data Constraints), we propose a framework where dataflow variables and stored data are analyzed. The validation and diagnosis process is automated using Constraint Program-ming, to permit the detection and identification of possibly unsatisfiable Business Data Constraints, even if the data involved in these constraints are not all instantiated. This implies that the potential errors can be determined in advance. Furthermore, a language to describe Business Data Constraints is proposed, for the improvement of user-oriented aspects of the business process description. This language allows a business expert to write Business Data Constraints that will be automatically validated in run-time, without the support of an information technology expert.Junta de Andalucía P08-TIC-04095Ministerio de Ciencia y Tecnología TIN2009-1371

La igualdad de género a través de la protección por nacimiento y cuidado de menor

En el presente trabajo se desarrolla el tema de la igualdad de género a través de una figura tan relevante como la prestación por nacimiento y cuidado de menor, introducida por el Real Decreto-Ley 6/2019, de 1 de marzo, de medidas urgentes para la garantía de la igualdad de trato y de oportunidades entre mujeres y hombres en el empleo y la ocupación, que constituye una pieza fundamental en la corresponsabilidad familiar de ambos progenitores. Este trabajo gira en torno a dos ideas fundamentales, la primera es la exposición del principio de igualdad y no discriminación por razón de sexo como derecho fundamental, tanto en el ámbito internacional y comunitario como en el ámbito nacional. La segunda idea trata de la descripción exhaustiva de las medidas establecidas por dicho Real Decreto-Ley 6/2019, de manera que se describe el descanso y la prestación de la madre biológica y el del otro progenitor; dichos descansos y prestaciones para las situaciones de adopción, guarda y acogimiento; y otras circunstancias peculiares. También se desarrollan aspectos concretos como el nacimiento y cuidado del menor en el ámbito público y en el ámbito privado, la nueva prestación por corresponsabilidad en el cuidado de lactante; y la tutela especial frente al despido en situaciones de nacimiento, cuidado del menor y otras equivalentes.<br /

Experimental determination of the convection heat transfer coefficient in an eccentric annular duct

The use of bayonet tube heat exchangers and heaters is widespread in many industrial applications and an improvement in the heat transfer coefficient may provide benefits over other technologies. This work presents novel experimental results about the turbulent convection heat transfer coefficient of air in the annular section of a bayonet tube for two different configurations: concentric and eccentric tubes. For both configurations, the convection heat transfer coefficient was obtained at different air flow rates, therefore, at different Reynolds numbers. In the case of the eccentric configuration, the angular position of the inner tube was varied to determine the circumferential distribution of the local convective heat transfer coefficient. An increase of the convection coefficient was observed for both configurations at higher Reynolds numbers. Concerning the angular position with regard the inner tube, the largest local convective heat transfer coefficient was obtained at the angular position where the distance between the inner and outer tubes was maximum, yielding a value 22.3% higher than in the case of a concentric annular section. All these experimental results were used to propose a new correlation for the local convective heat transfer coefficient as a function of the Prandtl and Reynolds numbers, the eccentricity, and the angular position of the inner tube, with a maximum discrepancy between correlation and experimental data below 10%.The authors gratefully acknowledge the financial support provided by Spanish Government through the project RTI2018-096664-B-C21 (FEDER/Ministerio de Ciencia e Innovación-Agencia Estatal de Investigación). Funding for APC: Universidad Carlos III de Madrid (Read & Publish Agreement CRUE-CSIC 2022

Influence of eccentricity on the thermomechanical performance of a bayonet tube of a central solar receiver

This work numerically evaluates the thermal and mechanical behaviors of eccentric bayonet tubes to be used in external central receivers of solar power tower plants. A bayonet tube is composed of two tubes, one inside the other, creating circular and annular sections, through which the molten salt of the receiver sequentially flows. Eccentricity in the annular section is achieved by displacing the axis of the interior tube with regard to the exterior one. For comparative purposes, two examples of conventional tubes (single tubes with circular cross-sections with diameters of 25mm and 50mm) are also investigated in this work to compare their performances with those of bayonet tubes. The results obtained with the eccentric configurations show an enhancement of the heat transfer to the molten salt and a reduction of the tube wall overheating compared with the concentric bayonet tubes and the largest simple tube. For conditions representative of the normal operation of a solar power tower, eccentric bayonet tubes could reduce the pressure drop by 30.8% and increase the convective heat transfer achieved in a concentric configuration of the bayonet tube by 26.1%. Nevertheless, this pressure drop was considerably higher than those obtained in the smallest and largest simple tubes, which were 1.28 bar and 0.13 bar, respectively. To investigate whether the enhancement of the convection heat transfer experienced by bayonet tubes compensates for their higher pressure drop or not, a Performance Evaluation Criterion (PEC) was proposed and used to compare the global performance of bayonet tubes with that of conventional tubes. The bayonet tubes with eccentricity 0.45 obtained the largest PEC, which was up to 13% higher than reference conventional tubes. Enhancement of the tube wall refrigeration produced when increasing the eccentricity is reflected in the maximum tube temperature and thermal stresses, which are found to diminish by approximately 8.8% with the highest eccentricity. In addition, the largest eccentric bayonet tube layout obtains the smallest peak temperatures compared to conventional tubes. The lower inertial moment of the smallest conventional tube indicates that its thermal stress is 2.1% lower than the stress obtained in the most eccentric layout analyzed in this work. Nevertheless, the time to rupture associated with creep damage of the eccentric bayonet tube is 1.04 times higher than that obtained in the smallest simple tube, demonstrating that bayonet tubes could be a potential alternative to the current tubes of external tubular receivers.The authors gratefully acknowledge the financial support provided by the grants RTI2018-096664-B-C21 funded by FEDER/Ministerio de Ciencia e Innovación-Agencia Estatal de Investigación, Spain and PID2021-122895OB-I00 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. This work was also financed by the Community of Madrid, Spain through the line of “Excelencia del Profesorado Universitario” of the Pluriannual Agreement with the UC3M, Spain (EPUC3M22), within the framework of the V PRICIT (V Plan Regional de Investigación Científica e Innovación Tecnológica). Rafael Pérez-Álvarez acknowledges support from the scholarship ”Ayudas para contratos predoctorales para la formación de doctores” BES-2016-078455 awarded by the Ministerio de Economá, Industria y Competitividad, Spain

Embolismo paradojal - tromboembolismo pulmonar e isquemia cerebral por foramen oval permeable: reporte de caso

30 to 40% of cerebrovascular diseases are of unknown or cryptogenic origin; they may be related to patent foramen ovale (PFO) with a prevalence of 12 to 30%. We report the case of a 62 year old woman who underwent surgery for a thyroid tumor. In the postoperative period she presented dyspnea, hypoxemia, impaired consciousness and expression aphasia. Transthoracic echocardiography showed dilatation of right chambers, and transesophageal echocardiography revealed a patent foramen ovale (PFO) with the presence of echoes compatible with clots bordering this defect; the brain scan revealed a stroke in the left hemisphere. The presence of clots and PFO intraoperatively confirmed the development of pulmonary embolism and paradoxical embolism.El 30 a 40% de las enfermedades cerebrovasculares presentan un origen desconocido o criptogénico. Puede estar relacionado con la persistencia de foramen oval (FOP), cuya prevalencia es de 12 a 30%. Reportamos el caso de una paciente mujer de 62 años, que fue intervenida por tumoración de tiroides. En el postoperatorio presentó disnea, hipoxemia, compromiso de conciencia y afasia de expresión. La ecocardiografía transtorácica mostró dilatación de cámaras derechas y la ecocardiografía transesofágica reveló un foramen oval permeable (FOP) con la presencia de ecos compatibles con coágulos que bordeaban dicho orificio: la tomografía cerebral evidenció un infarto cerebral en el hemisferio izquierdo. El hallazgo de coágulos y del FOP en el intraoperatorio confirmó el desarrollo de tromboembolismo pulmonar y embolismo paradojal

Impact of a mechanical attachment on the preheating temperatures of a central receiver tube

The receiver tubes of Solar Power Tower plants are typically attached through clips and sliding rods to the reradiating wall of the receiver in order to reduce the thermal deflection of the tubes. However, as a side effect, these mechanical attachments increase heat dissipation from the tube to the exterior and can reduce the local temperature of the tube during the receiver start-up, an operation performed every morning or after a severe drop of solar irradiation due to passing clouds. In the start-up operation, the empty tubes of molten salt receivers must be preheated with a careful aiming sequence of the heliostat field until their temperature is high enough to avoid the freezing of the incoming flow of the molten salt. This work numerically addresses for the first time the influence of the mechanical attachment on the preheating temperature of a receiver tube. To achieve this goal, a set of three-dimensional thermal fluid simulations of the temperature distribution in the tube and the mechanical attachment, described with different levels of detail, has been performed for the receiver of the Gemasolar Solar Power Tower plant. The results of this work show that the mechanical attachment locally affects the tube temperature, leading to a temperature overestimation above 25.1% when the tube is modeled without a mechanical attachment. In addition, the temperature measured separated from the attachment at the rear face of the tube to control the preheating sequence may not be very representative of the minimum tube temperature, which occurs in the internal face of tube just beneath the mechanical attachment. The results indicate that accumulation of heat not only by the clip but also by the guide and the rod of the mechanical attachment plays a significant role in the dissipation of heat from the tube to the attachment. This reveals the need of considering all the elements of the mechanical attachment if an accurate modeling of the preheat temperatures of the tube is needed. Besides, the use of a simplification in the modeling of the air and radiative heat transfer outside the tube reduces by a factor of 4.9 the computational cost involved in a full simulation of these transfer processes, with a temperature discrepancy between models below 14.3%. Finally, the effect of the size of the attachment clip on the minimum tube temperature is investigated, revealing that the minimum tube temperature of the preheated tube can decrease below the freezing temperature of the molten salt for clip heights larger than 170 mm.The authors gratefully acknowledge the financial support provided by Spanish Government through project RTI2018-096664-B-C21 (FEDER/Ministerio de Ciencia e Innovación-Agencia Estatal de Investigación). Eduardo Cano-Pleite acknowledges support from the CONEX-Plus programme funded by Universidad Carlos III de Madrid and the European Union's Horizon 2020 programme under the Marie Sklodowska-Curie grant agreement No. 801538 and the financial support of the Spanish Government under the project PID2019-109224RA-I00

AM3 (Inmunoferón®) as an adjuvant to hepatitis B vaccination in hemodialysis patients

AM3 (Inmunoferón®) as an adjuvant to hepatitis B vaccination in hemodialysis patients.BackgroundPatients with end-stage renal disease (ESRD) undergoing hemodialysis have severe alterations in cell-mediated immunity (CMI) that increases their risk of contracting chronic hepatitis B virus (HBV) infection and decreases their protective responses to HBV vaccine. In an effort to improve the humoral response to an accelerated HBV vaccine protocol in these patients, the ability of an immunomodulator, AM3, to improve seroconversion was investigated.MethodsA total of 269 patients were enrolled in a multicenter trial. All patients received a DNA recombinant vaccine (40 μg HBsAg/dose/day) on days 0, 10, 21, and 90. AM3 or placebo (3 g/day) was given orally for 30 consecutive days beginning 15 days prior to the first vaccine dose. Anti-HBsAg titers were measured on days 120 and 270 after the beginning of the trial.ResultsAfter one month, 207 patients could be evaluated and 132 patients after six months. The placebo and AM3-treated groups had comparable seroconversion and protective response rates one month after the final vaccine dose. The AM3 treatment group, but not the placebo group, maintained these protective titers up to six months after the final vaccine dose. At this time, the percentage of high responders (anti-HBsAg>100 IU/L) and mean anti-HBsAg titers in the AM3 group was significantly higher than in the placebo group.ConclusionsAM3 is a safe and easily tolerated oral agent that potentiates long-term serological immunity to hepatitis B in hemodialysis patients after vaccination