Study of different subcooling control strategies in order to enhance the performance of a heat pump

[EN] The performance of vapor-compression systems working with subcritical refrigerants varies with the degree of subcooling. There is an optimal subcooling that maximizes efficiency. However, it depends on the operating conditions and the control of the system needs to be adapted. Most of the works available in literature are able to operate in optimal conditions only at the design point or if a system is designed to be able to adapt its subcooling, only complex control algorithms that usually are difficult to set and time-costly, are used. This work focuses on the study of the main variables influencing the optimal subcooling and analyzes two different control methodologies from the theoretical point of view. Based on the theoretical study a final control strategy is selected and tested experimentally. The reliability, stability and robustness of the selected strategy are experimentally demonstrated for a wide set of operating conditions. (c) 2018 Elsevier Ltd and IIR. All rights reserved.Part of the work presented was carried by Estefania Hervas Blasco with the financial support of a PhD scholarship from the Spanish government SFPI1500 x 074478XV0. The authors would like also to acknowledge the Spanish 'MINISTERIO DE ECONOMIA Y COMPETITIVIDAD', through 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 DECONSUMO CASI NULO" with the reference ENE2017-83665-C2-1-P for the given support.Hervas-Blasco, E.; Pitarch, M.; Navarro-Peris, E.; Corberán, JM. (2018). Study of different subcooling control strategies in order to enhance the performance of a heat pump. International Journal of Refrigeration. 88:324-336. https://doi.org/10.1016/j.ijrefrig.2018.02.003S3243368

Combination of Technologies for Architectural Planning. Parish Church of Portell

La sucesiva aplicación de las nuevas tecnologías a la expresión gráfica arquitectónica ha supuesto una revolución en cada uno de los pasos que dan como resultado el levantamiento de planos. En general se puede decir que en gran medida facilitan la consecución del trabajo a realizar. Sin embargo, su aplicación de manera generalizada e indiscriminada, puede ocasionar un trabajo excesivo e innecesario. Por tanto, el reto de la aplicación de nuevas tecnologías supone no sólo su conocimiento y adecuado manejo, sino además, la capacidad de descartar unos métodos frente a otros en función de las necesidades planteadas por el modelo a representar, la finalidad del trabajo a realizar, la disponibilidad de medios y de tiempo. El presente artículo es una muestra de la conveniencia en la utilización de métodos tradicionales y nuevas tecnologías, basada su combinación en la optimización de tiempo y recursos. El estudio realizado se fundamenta en el levantamiento de planos, y análisis gráfico y metrológico, de la Iglesia Parroquial de Portell, la primera de las iglesias de planta salón valencianas construidas en el siglo XVIII

El litoral turístico valenciano. Intereses y controversias en un territorio tensionado por el residencialismo.

El artículo quiere analizar, valorar y comprender el fortísimo oleaje inmobiliario que ha conocido el litoral valenciano en los últimos años (1998-2008) y sus repercusiones sobre el territorio turístico. Importará, desde el análisis geográfico, acercarse al planteamiento territorial y político, en sus vertientes urbanísticas y turísticas, así como a los procesos y estrategias de cambio en los destinos, sean estos manifiestamente turísticos o relevantemente residenciales. Se pretende también cuantificar a escala municipal el impacto de dicha explosión inmobiliaria-residencial y, por supuesto, incidir objetivamente en las controversias derivadas del llamado «milagro económico valenciano»

Experimental study of a subcritical heat pump booster for sanitary hot water production using a subcooler in order to enhance the efficiency of the system with a natural refrigerant (R290)

[EN] This paper presents the experimental results obtained from a new heat pump prototype for sanitary hot water production, in the application of heat recovery from water sources like sewage water or condensation loops (typical temperature condition between 10 degrees C and 30 degrees C). The system configuration is able to produce a high degree of subcooling in order to take advantage from the high water temperature glide (typical value for sanitary hot water production is 10 degrees C to 60 degrees C). Subcooling is made by using a separate heat exchanger from the condenser (subcooler). The obtained results have shown a high degree of improvement by making subcooling. COP is 5.61 in nominal conditions, which is about 31% higher than the same cycle working without subcooling (Nominal point: inlet/outlet water temperature at evaporator is 20 degrees C/15 degrees C and the water inlet/outlet temperature in the heat sink is 10 degrees C and 60 degrees C). (C) 2016 Elsevier Ltd and HR. All rights reserved.This work has been developed in the European Union Seventh Framework Programme by the project Next Generation of Heat Pump Technologies (NEXTGHP) grant agreement 307169. The authors give thanks for the given support. Part of the work presented was carried by Miguel Pitarch-Mocholi with the financial support of the Phd scholarship from the Universitat Politecnica de Valencia.Pitarch, M.; Navarro-Peris, E.; Gonzálvez-Maciá, J.; Corberán, JM. (2017). Experimental study of a subcritical heat pump booster for sanitary hot water production using a subcooler in order to enhance the efficiency of the system with a natural refrigerant (R290). International Journal of Refrigeration. 73:226-234. doi:10.1016/j.ijrefrig.2016.08.017S2262347

Optimal sizing of a heat pump booster for sanitary hot water production to maximize benefit for the substitution of gas boilers

[EN] Heat recovery from water sources such as sewage water or condensation loops at low temperatures (usually between 10 and 30 °C) is becoming very valuable. Heat pumps are a potential technology able to overcome the high water temperature lift of the Sanitary Hot Water (SHW) application (usually from 10 °C to 60 °C with COPs up to 6). This paper presents a model to find the optimal size of a system (heat pump and recovery heat exchanger) based on water sources to produce SHW compared to the conventional production with a gas boiler in order to maximize the benefit. The model includes a thermal and economic analysis for a base case and analyzes the influence of a wide set of parameters which could have a significant influence. Even the uncertainties involved, results point out considerable benefits from this substitution based on the capacity of the system. Thus, demonstrating the importance of the optimal size analysis before an investment is done.Part of the work presented was carried by Estefania Hervas Blasco with the financial support of a PhD scholarship from the Spanish government SFPI1500X074478XV0. Part of the work presented was carried by Miguel Pitarch-Mocholi with the financial support of a PhD scholarship from the Universitat Politecnica de Valencia. The authors would like also to acknowledge the Spanish 'MINISTERIO DE ECONOMIA Y COMPETITIVIDAD', through the project ref-ENE2014-53311-C2-1-P-AR "Aprovechamiento del calor residual a baja temperatura mediante bombas de calor para la produccion de agua caliente" for the given supportHervas-Blasco, E.; Pitarch, M.; Navarro-Peris, E.; Corberán, JM. (2017). Optimal sizing of a heat pump booster for sanitary hot water production to maximize benefit for the substitution of gas boilers. Energy. 127:558-570. https://doi.org/10.1016/j.energy.2017.03.13155857012

Experimental study of a heat pump with high subcooling in the condenser for sanitary hot water production

[EN] The use of heat pumps in order to produce sanitary hot water have been demonstrated as a very efficient alternative to traditional boilers. Nevertheless, the high water temperature lift (usually from 10 degrees C to 60 degrees C) involved in this application has conditioned the type of used solutions. In order to overcome it, transcritical cycles have been considered as the most suitable solution. The current article analyzes a new heat pump prototype able to enhance the heat pump efficiency using a subcritical cycle. The proposed prototype is able to control the system subcooling and make it capable to work at different subcoolings in the condenser. That kind of mechanism has demonstrated its capability to increase the efficiency of the heat pump. The obtained results have shown that coefficient of performance depends strongly on subcooling. In nominal condition (inlet/outlet water temperature at evaporator is 20 degrees C/15 degrees C and the water inlet/outlet temperature in the heat sink is 10 degrees C and 60 degrees C), the optimal subcooling is 42 K with a heating coefficient of performance of 5.35, which is about 25% higher than the same cycle working without subcooling.Pitarch, M.; Navarro-Peris, E.; Gonzálvez-Maciá, J.; Corberán, JM. (2018). Experimental study of a heat pump with high subcooling in the condenser for sanitary hot water production. Science and Technology for the Built Environment. 24(1):105-114. https://doi.org/10.1080/23744731.2017.1333366S10511424

Exergy analysis on a heat pump working between a heat sink and a heat source of finite heat capacity rate

[EN] The optimum performance of a pure subcritical refrigeration cycle depends significantly on the temperature lift of the heat source and sink. Therefore, the maximization of the system efficiency has to be linked to them. This paper shows an exergy analysis of each heat pump component (condenser, evaporator, expansion valve and compressor) considering that the heat source and sink are not at constant temperature. The performed study shows the components with more possibilities for improvement. Based on this analysis, the optimization of cycle parameters like subcooling and superheat as a function of the external conditions have been done. In addition, this work has demonstrated that the components having a higher influence in the system irreversibility's depends significantly on the temperature lift of the secondary fluids. Finally, the obtained results show potentials improvements of the efficiency up to 23% if the system is able to operate in the optimal subcooling and superheat.Part of the results of this study were developed in the mainframe of the FP7 European project 'Next Generation of Heat Pumps workingwith natural fluids' (NxtHPG). Part of the work presented was carried by Miquel Pitarch with the financial support of a PhD scholarship from the Universitat Politecnica de Valencia. Part of the work presented was carried by Estefania Hervas-Blasco with the financial support of a Ph.D. scholarship from the Spanish government SFPI1500X074478XV. The authors would like also to acknowledge the Spanish 'MINISTERIO DE ECONOMIA Y COMPETITIVIDAD', through the Project ENE2017-83665-C2-1-P, "Maximizacion de la Eficiencia y Minimizacion del Impacto Ambiental de Bombas de Calor para la descarbonizacion de la calefaccion/ACS en los proximos edificios de consumo energetico casi nulo" for the given support.Pitarch, M.; Hervás-Blasco, E.; Navarro-Peris, E.; Corberán, JM. (2019). Exergy analysis on a heat pump working between a heat sink and a heat source of finite heat capacity rate. International Journal of Refrigeration. 99:337-350. https://doi.org/10.1016/j.ijrefrig.2018.11.044S3373509

Contrast-enhanced mammography-guided biopsy: technical feasibility and first outcomes

Objectives To evaluate the feasibility of contrast-enhanced mammography (CEM)-guided biopsy at Hospital del Mar, a Spanish university hospital. Methods We retrospectively reviewed all consecutive women with a suspicious enhancing finding eligible for CEM-guided biopsy, who were prospectively enrolled in a pre-marketing clinical validation and feasibility study (October 2019 to September 2021). CEM-guided biopsy is a stereotactic-based procedure that, by using intravenous iodinated contrast media administration and dual-energy acquisition, provides localisation of enhancing lesions. All the biopsies were performed using a vacuum-assisted device. We collected procedural characteristics (patient position and type of approach), and histopathological results. Feasibility endpoints included success (visualisation of the enhancing lesion, post-procedural biopsy changes and clip placement), procedural time, number of scout acquisitions and complications. Results A total of 66 suspicious enhancing lesions (18.0% foci, 44.0% mass, 38.0% non-mass enhancement; median size 8.5 mm) in 64 patients (median age 59 years, mostly minimal [48.4%] or mild [32.8%] background parenchymal enhancement) were referred for CEM-guided biopsy in the study period. The success rate was 63/66 (95.4%). Amongst successful procedures, patients were most frequently seated (52/63, 82.5%) and the preferred approach was horizontal (48/63, 76.2%). Median total time per procedure was 15 min. Median number of acquisitions needed before targeting was 2 (range 1-4). Complications consisted of hematoma (17/63, 27%) and vasovagal reaction (2/63, 3.2%). At histology, the malignancy rate was 25/63 (39.7%). Conclusion In this first patient series, CEM-guided breast biopsy was feasible, with success and complication rates similar to those previously reported for magnetic resonance guidance

Control synthesis for polynomial discrete-time systems under input constraints via delayed-state Lyapunov functions

This paper presents a discrete-time control design methodology for input-saturating systems using a Lyapunov function with dependence on present and past states. The approach is used to bypass the usual difficulty with full polynomial Lyapunov functions of expressing the problem in a convex way. Also polynomial controllers are allowed to depend on both present and past states. Furthermore, by considering saturation limits on the control action, the information about the relationship between the present and past states is introduced via Positivstellensatz multipliers. Sum-of-squares techniques and available semi-definite programming (SDP) software are used in order to find the controller.The research work by J.L. Pitarch and A. Sala has been partially supported by the Spanish government under research project [grant number DPI2011-27845-C02-01 (MINECO)]; Generalitat Valenciana [grant number PROMETEOII/2013/004]. The work by T.M. Guerra and J. Lauber has been supported by the International Campus on Safety and Intermodality in Transportation, the European Community, Delegation Regionale a la Recherche et a la Technologie, Ministere de l'Enseignement superieur et de la Recherche, Region Nord Pas de Calais and the Centre National de la Recherche Scientifique.Pitarch Pérez, JL.; Sala Piqueras, A.; Lauber, J.; Guerra, TM. (2016). Control synthesis for polynomial discrete-time systems under input constraints via delayed-state Lyapunov functions. International Journal of Systems Science. 47(5):1176-1184. https://doi.org/10.1080/00207721.2014.915357S1176118447

Reduction of CO2-emissions in ceramic tiles manufacture by combining energy-saving measures

Ceramic tile manufacture requires a great quantity of energy, mainly in the form of heat. The heat is principally used in the kilns and dryers, and it is obtained by natural gas combustion. The increasing cost of natural gas, as well as the application of a new gas tax, the new legislation in regard to emissions trading, and the difficult current economic situation have driven the ceramic tile sector to implement energy-saving actions in the production process with the twofold aim of reducing energy costs and abating carbon dioxide emissions. One such course of action is the European project REDUCER, funded by the European Commission and led by Azulev S.A.U., in which the Instituto de Tecnología Cerámica (ITC) also participates. This project seeks to implement energy-saving actions in company kilns and dryers in order to lower natural gas consumption and reduce carbon dioxide emissions in the tile manufacturing process. One of the saving actions envisaged is the installation of a system of waste heat recovery from one of the company kilns to the tile body dryers. This new waste heat recovery system is to be added to and will complement the already existing system at the company, thus achieving maximum heat recovery from the kiln stacks. The recovered heat will go entirely to the green tile body dryers, thus reducing natural gas consumption in the dryers. The designed installation seeks to recover 600 kW heat from the stacks of one of the kilns, entailing a natural gas saving of more than 120 k€/year and suppressing the emission into the atmosphere of 720 tons of CO2/year, savings that are to be added to those attained with other energy-saving measures. This paper describes the energy-saving actions implemented at the company, as well as the resulting energy savings