Virtual sensor of insufficient lubrication in variable speed compressors

The ability to modulate the compressor’s speed and adapt the capacity to the load has permitted to decrease the annual energy consumption in many applications. However, in the compressor, having the correct lubrication at high speeds usually imply having insufficient lubrication at low speeds. This fact has to be considered by manufacturers as it limits the speed range of the compressor. In this study, a methodology to establish the working limit of a compressor is proposed. It is based on the specific consumption surface of the compressor and no oil circulation measurements are required. A compressor working between 6600 and 900rpm with propane and POE oil has been used to test the proposed methodology. The results show that lubricating issues in this compressor start at 1800rpm and rise as speed decreases.The authors would like to acknowledge the Spanish “MINISTERIO DE ECONOMIA Y COMPETITIVIDAD”, through the project ref- ENE2017-83665-C2-1-P “Maximización de la eficiencia y minimización del impacto ambiental de bombas de calor para la descarbonización de la calefacción/ acs en los edificios de consumo casi nulo” for the given support. In addition, Ruben Ossorio would like to thank the Spanish government for his PhD scholarship with reference PRE2018-083535

Evolutionary Algorithms for Community Detection in Continental-Scale High-Voltage Transmission Grids

Symmetry is a key concept in the study of power systems, not only because the admittance and Jacobian matrices used in power flow analysis are symmetrical, but because some previous studies have shown that in some real-world power grids there are complex symmetries. In order to investigate the topological characteristics of power grids, this paper proposes the use of evolutionary algorithms for community detection using modularity density measures on networks representing supergrids in order to discover densely connected structures. Two evolutionary approaches (generational genetic algorithm, GGA+, and modularity and improved genetic algorithm, MIGA) were applied. The results obtained in two large networks representing supergrids (European grid and North American grid) provide insights on both the structure of the supergrid and the topological differences between different regions. Numerical and graphical results show how these evolutionary approaches clearly outperform to the well-known Louvain modularity method. In particular, the average value of modularity obtained by GGA+ in the European grid was 0.815, while an average of 0.827 was reached in the North American grid. These results outperform those obtained by MIGA and Louvain methods (0.801 and 0.766 in the European grid and 0.813 and 0.798 in the North American grid, respectively)

Turismofobia. La situación actual de las zonas turísticas saturadas.

Se trata de un análisis de la situación actual de las zonas turísticas de nuestro país focalizado en la saturación de algunas de ellas las cuales dan lugar a un desprecio hacia los turistas por parte de la población local debido a los problemas que causan acuñando el termino turismofobia.<br /

Análisis de una metodología alternativa para realizar medidas en tiempo real de la tasa de circulación de aceite en una instalación de refrigeración

En un sistema de refrigeración, los compresores toman el refrigerante a baja presión y lo bombean hacia el condensador a una presión más elevada. Sin embargo en su proceso de operación no sólo bombea el refrigerante, parte del aceite utilizado en la lubricación del compresor también se bombea al resto del sistema. La magnitud básica utilizada para caracterizar la cantidad de aceite bombeado se conoce como tasa de circulación de aceite (TCA) y representan la fracción de aceite sobre el flujo de masa total de aceite más refrigerante. TCA es una variable importante a determinar en la caracterización de un compresor. Puede dar información acerca de problemas de lubricación del compresor y también desde el punto de vista de la operación de la instalación, valores demasiado altos de esta magnitud deben ser evitados. Sin embargo, hasta ahora no existe una metodología precisa para medir TCA que no incluya desventajas importantes como necesitar una gran cantidad de tiempo, no ser en tiempo real, costosa, o requiera una calibración muy precisa in situ de los dispositivos de medida. En este trabajo, se analiza una metodología para medir TCA indicando las principales fuentes de error implicadas. La metodología consiste en instalar un medidor de flujo másico tipo Coriolis en la línea de retorno de aceite entre el separador de aceite de la instalación y el compresor. Este sensor mide el flujo de aceite desde el separador de aceite al compresor y posteriormente se relaciona esta medida con la TCA a través del sistema. Los resultados se han comparado sistemáticamente con la metodología propuesta en ASHRAE Standard ANSI 1994 [1] en varias condiciones y con varios diseños de compresores y el grado de precisión de esta metodología se ha determinado.The authors are very grateful to the collaboration given by Francesco Botticella, Lucie Puren and Luca Di Lallo in the development of part of this experimental work

Efficiency characterization of a variable speed compressor

[EN] Heat pump systems have been spreading into the heating and air conditioning industry as they offer an affordable, efficient and reliable solution. They are considered by the EU as the solution to follow in heating and cooling in order to reach the objectives in reduction of CO2 emissions. As a consequence of that, there is a growing interest in the development of more efficient heat pump systems which has motivated the introduction of many technical innovations in the last 10 years. Among these innovations, the introduction of inverter system has been quite popular. This technology could imply a significant improvement when the system has to work at non-design conditions. However, in the standards there is limited information about the characterization procedure of these systems (i.e. EN 13771-1 only refers to fixed speed or vapour injection compressors) and compressor-inverter system are characterized as a single unit. In that context, it is typical to assume a fixed power loss factor of 3-5% in the inverter. That power loss factor is considered when designing a new system but could differ in the final appliance, especially when the system runs at low speed. In conclusion, the knowledge around variable speed compressors is limited and the system is usually studied as a black box. In this study, the power of a variable speed compressor and its corresponding inverter have been measured separately in a calorimeter test bench according the specifications of the norm EN 13771-1. From these measurements, it has been possible to determine the efficiency of the compressor and the inverter independently. From these results, the aim of the study is to provide a complete analysis of the performance of a variable speed compressor system. The experimental analysis was carried out using the same compressor with two different models of inverter with the same commutation technology. The study consisted in a battery of tests in which the same compression conditions were maintained while the rotation speed of the compressor were modified from 30rps to 120rps. The results of the paper show that the speed of the compressor and the chosen inverter brand has a high effect on the efficiency. Moreover, these results can be applied to get the efficiency curve of an inverter and point out the error that can be made by designers when considering a fixed 3-5% power loss. And last but not least, the study can also set the bases for other investigations involving the reductionOssorio-Santiago, RJ.; Navarro-Peris, E.; Gonzálvez-Maciá, J.; Albaladejo, P.; López-Navarro, A. (2019). Efficiency characterization of a variable speed compressor. Universidad de Castilla-La Mancha José Antonio Almendros Ibáñez. 265-275. http://hdl.handle.net/10251/180707S26527

Una actuación respetuosa con los valores ambientales en el puesto de Avilés

In 1997, the Port Authority of Avilés commissioned a study onmanoeuvre viability from the Maritime Aid and SecuritySociety “Centro Jovellanos”, in order to investigate the lengthlimitation of vessels at a portion of the entrance channelknown as the Pachico curve.The works consist on the dredge of a strip of 1400 m long andvariable width (maximun 70 m ). As dredging works continue,environmental regeneration and improvement works begin atthis point.Unique in the region, this area has a great ecological value,and today it’s included as a Natural Monument into theManagement Plan for Natural Resources in Asturias.En 1997, la Autoridad Portuaria de Avilés encarga a laSociedad de Salvamento y Seguridad Marítima “CentroJovellanos” un estudio sobre la viabilidad de las maniobras,referente a la limitación de eslora de los buques quetransitan por la curva de Pachico. En este estudio seconcluye que aumentando la anchura del canal denavegación en su parte derecha en 70 metros, se podríaaumentar la eslora máxima de los buques que transitan porel canal de navegación a 245 metros.A raíz de este estudio, la Autoridad Portuaria de Avilésdecide acometer las obras de “Ensanche de la curva dePachico, en el Puerto de Avilés, incluyendo la regeneraciónmedioambiental del entorno”, que principalmente hanconsistido en el dragado de una franja de unos 1.400 metrosde longitud y un máximo de 70 metros. El material a dragarera substrato rocoso en los primeros 800 metros y arena elresto.Además de las obras de dragado, en el proyecto también seincluyeron las obras de conservación y mejora de los valoresmedioambientales, dado que la zona sobre la que se iba aactuar goza de gran valor ecológico y paisajístico, y aunqueen ese momento se encontraba muy degradada por la acciónhumana, existía la intención de ser declarada MonumentoNatural, dentro del Plan Regional de Ordenación de losRecursos Naturales de Asturias

Deficiencias del Sistema de Financiación Autonómica Actual: Simulación de tres modelos alternativos

El estudio que se va a exponer a continuación, parte del análisis de una de las subdisciplinas de la propia Hacienda Pública: El Federalismo Fiscal. A través de su análisis, se explicará de una forma teórica y práctica los principios que rigen un sistema descentralizado y con ello, nos permitirá comprobar si hoy en día, se cumplen en España. Con el objetivo de evaluar la situación de nuestro país, en el ámbito de la financiación descentralizada, se procederá a evaluar los sistemas de financiación autonómica vigentes; a contrastar con los principios teóricos del Federalismo Fiscal en el sistema de financiación actual, y además, se planteará una serie de modelos opcionales al de hoy en día, para ver las consecuencias que tendrían si se ejerciesen de una forma alternativa

Comparative Study of the Mineralogy and Chemistry Properties of Elephant Bones: Implications during Diagenesis Processes

Elephants are currently the largest terrestrial mammals, along with their extinct ancestor the mammoth. These species are of great interest due to their geographic distribution and ecological importance. However, the bone mineral characteristics of their skeleton as well as their alteration during burial processes over millions of years have been poorly investigated. In the current research, we analyzed the compositional and structural mineral properties of different types (i.e., long and flat bones) of elephant and mammoth bones. For this purpose, we performed a comparative study between these bone types using complementary analytical techniques based on X-ray diffraction, thermogravimetry, Fourier transform infrared spectroscopy, scanning electron microscopy, and inductively coupled plasma spectroscopic analysis. The chemical composition of the samples shows a relative loss of a considerable percentage of water and organic matter components for the fossilized bone, accompanied by a higher bone mineralization degree and the presence of other crystalline phases (i.e., calcite and pyrite) related to a certain degree of diagenesis alteration. Our results also show a variation in the crystalline properties of mammoth bone related to the recrystallization process during the dissolution–precipitation transformation through diagenetic burial. This research provides relevant information for understanding the mineral properties of different types of bones and their possible changes during diagenesis.Spanish Government CGL2015-64683-P PID2020-116660GB-I00European Regional Development Fund (ERDF)-Next Generation-EU progra

Effect of Heating on Avian (Cortical and Medullary) Bone Chemistry, Mineralogy and Structural Organization

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.cgd.3c00648.The study of bone changes induced by heating is highly relevant for forensic and archeological analyses as well as for the production of bone-derived materials with novel properties and applications. In the present study, we study in detail how different types of avian bone (cortical, medullary) transform during thermal treatments (up to 800 °C) using different analytical techniques such as thermogravimetry (TGA-DSC), electron microscopy, X-ray diffraction and infrared spectroscopy. We show that bone transformation following thermal treatments is strongly influenced by bone architecture, the composition of the organic matrix, and the integration of the mineral with the organic fractions. For instance, in avian cortical bone, the apatite nanocrystals are integrated within collagen fibrils and coated with phosphorylated proteins. During heating, the collagen losses structural order and denatures (at around 200 °C), losing all structural integrity at 300 °C. In the bone mineral fraction, there is a gradual conversion of phosphate, in poorly crystalline/amorphous environments, into apatite (up to 400 °C). However, it is not until all organics are completely lost at around 600 °C that recrystallization sets in with a rapid increase in the size of apatite crystals. Also, during recrystallization, foreign ions (Mg2+, Na+) are expelled from the apatite lattice to the crystal surface, and the degree of preferential orientation of the apatite crystals increases as larger, well-oriented apatite crystals grow epitaxially at the expense of smaller, randomly oriented crystals. However, the scenario is different for the medullary bone. In this case, with an organic matrix rich in noncollagen proteins and proteoglycans, the recrystallization sets in at much lower temperatures (around 400 °C compared to 600 °C in cortical bone). Thus, the association of mineral and organic components controls recrystallization, particularly in the case of apatite nanocrystals within collagen fibrils in cortical bone. Also, the calcination process creates additional microporosity in both types of bone, increasing the bone mineral surface area and reactivity. The information obtained in this study provides a better understanding of the dynamics of bone transformation during alteration in natural processes (e.g., diagenesis, burning) and how bone mineral characteristics can be modified for specific applications (e.g., bone grafts, waste removal, or chromatography).Junta de Andalucía (P20_00208 and P20_00207)Spanish government (PID2020-116660GB-I00), UCE-PP2016-05Biotechnology Institute (University of Granada

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