Experimental analysis of thermal storage tank configurationin a solar cooling installation with an absorption chiller

The use of air conditioning systems in Spanish dwellings is gaining popularity, as the installed units grows by 0,8 million per year. The most popular air conditioning system today is the vapor-compression cycle. This kind of system consumes a considerable amount of electric energy as it incorporates a mechanical compressor in its cycle and utilizes refrigerants that can be dangerous to the environment. A solution to this kind of equipment can be found in Solar Facilities configured to produce cold water for air conditioning purposes by means of an absorption chiller. This kind of equipment can be driven by a heat input produced by the solar facility. This machine consumes a very low amount of electric energy and presents great advantages for the environment. Nevertheless, the need of a heat reservoir to operate in the afternoon hours, where solar radiation is not enough to drive the chiller, is indispensable in a solar facility. To serve this purpose, the introduction of a thermal storage tank has to be made. There are two basic internal configurations of a thermal storage tank in a solar cooling facility. These are Stratification and Well-mixed configuration. Experimental results show that for solar cooling applications, having a homogeneous mixture temperature in the thermal storage tank produce more daily cooling energy than in an stratified one, although the solar field efficiency is lower. This gives the facility more autonomy of operation in the afternoon, when the sun goes down and radiation is not enough for the application. Effects on the facility produced by Well-mixed configuration are: efficiency reduction on the solar collector’s field , 0,27, higher daily COP’s, 0,33, and extended solar cooling time of about two hours.Universidad Carlos III de Madrid - ITEA Research GroupPublicad

Simulation of an absorption based solar cooling facility using a geothermal sink for heat rejection

An important issue of solar cooling facilities based on absorption cycles and sometimes not given the necessary attention is the recooling process of the absorber and condenser. This is critical in the overall behaviour of the facility because the condensation and absorption temperatures will affect the COP and cooling capacity of the chiller. Most of the time the recooling process is made by using a wet cooling tower in a closed loop through the absorber and condenser. The use of a wet cooling tower gives good results in terms of cooling capacity and COP, but presents some health risk, like legionella, and its use is restricted to the industrial sector and places where water scarcity is not present. This paper presents the modification of the already validated TRNSYS simulation of a solar cooling facility, implementing a geothermal heat sink instead of the wet cooling tower in order to dissipate the heat generated internally in the absorption chiller. Simulation results shows that a geothermal heat sink composed of 6 boreholes of 100 meters of depth should be sufficient in order to substitute the wet cooling tower, for a typical Spanish single family dwelling.Universidad Carlos III de Madrid - ITEA Research GroupPublicad

Optimized Design of Hot Water Storage in Solar Thermal Cooling Facilities

Solar thermal installations can provide a significant contribution to the energy needs of cooling demand of single family buildings. Unfortunately oversizing facility elements is not uncommon. Most of the design flaws concern collector field or auxiliary elements, such as backup boilers or electric resistances inside storage devices. This leads to lower than expected facility COP and SCOP, but also higher cost. Customer dissatisfaction is the result. This paper presents a numerical model of the multiple purpose solar thermal facility installed at Universidad Carlos III de Madrid (UC3M) using the TRNSYS® tool. The solar cooling facility (http://termica.uc3m.es/solar.htm) is completely monitored for its performance characterization in the production of AC, DHW and heating. Operational data for various summer seasons have been recorded, simultaneously with 7 meteorological variables. The experimental facility includes a single effect BrLi absorption chiller working at part load under summer season. TRNSYS is a completely feasible platform for simulating solar facilities and is commonly used by researchers and planners, for its simplicity and ease manipulation. This simulation tool contains general solar cooling elements found in most experimental facilities and has been kept as simple as possible. The model developed aims at analyzing facility elements in order to resize collector field and storage volumes. Furthermore it allows studying different configurations of the facility and the control schemes. These configurations include different hot water storage capacities within the facility allowing comparing with the facility without any kind of storage excepting its own thermal inertia. The simulation has been validated with instantaneous and seasonal experimental data for different summer seasons including 2003, 2004 and 2005. Simulation results show that there is a hot storage tank capacity that optimizes the facility in terms of COP, SCOP and total cold produced. Even with no storage at all, the facility still improves its behavior from current operating conditions. Simulation and experimental results are compared and an optimum configuration of the facility is proposed.Universidad Carlos III de Madrid - ITEA Research GroupPublicad

Energy and Exergy Analysis of Water-LiBr Absorption Systems with Adiabatic Absorbers for Heating and Cooling

AbstractSolar energy can be used to produce cold through absorption systems. In this study, the energy and exergy analysis on a single effect water-LiBr absorption facility is presented. The work is carried out for heating and cooling applications. Performance parameters are the coefficient of performance and exergy efficiency. The influence of operating temperatures on such parameters is included. An analysis of individual components is also presented. The most noticeable effect is observed for the case of exergy efficiency for absorber and generator. This parameter increases with an increase of absorption temperature. The opposite effect is observed when the generation temperature increases. Results obtained allow the identification of parameters that may influence the exergy efficiency of the adiabatic absorption system. The first candidate to optimize is the absorber, due to the lowest value of exergy efficiency obtained among all components of the system. For adiabatic absorbers, the recirculation ratio emerges as a new parameter. The solution heat exchanger is also susceptible to optimization

Vorticity dynamics in three-dimensional pulsating co-flowing jet diffusion flames

The vorticity dynamics in the near field of laminar (Re = 103) co-flowing jets subjected to the single or combined effeets of axial and azimuthal forcing is analyzed. It is shown that the interaction of the three-dimensional vortex structure resulting from the growth of the two and three-dimensional instabilities may result in large changes in the entrainment and mixing characteristics of the jet. For each azimuthal forcing, and for a fixed velocity ratio between the inner and outer jet, we show the existence of several instability modes leading to a pattern of lateral ejections of closed vortex loops. These modes and their topological changes are analyzed in view of the three-dimensional inviscid induction of the two concentric array of vortex rings emanating from the j e t s exit nozzle. For the case of methane-air diffusion flames, fiow visualizations revealed the existence of qualitatively similar patterns of closed fíame cells and fingers

Domestic hot water consumption vs. solar thermal energy storage: the optimum size of the storage tank

Many efforts have been made in order to adequate the production of a solar thermal collector field to the consumption of domestic hot water of the inhabitants of a building. In that sense, much has been achieved in different domains: research agencies, government policies and manufacturers. However, most of the design rules of the solar plants are based on steady state models, whereas solar irradiance, consumption and thermal accumulation are inherently transient processes. As a result of this lack of physical accuracy, thermal storage tanks are sometimes left to be as large as the designer decides without any aforementioned precise recommendation. This can be a problem if solar thermal systems are meant to be implemented in nowadays buildings, where there is a shortage of space. In addition to that, an excessive storage volume could not result more efficient in many residential applications, but costly, extreme in space consumption and in some cases too heavy. A proprietary transient simulation program has been developed and validated with a detailed measurement campaign in an experimental facility. In situ environmental data have been obtained through a whole year of operation. They have been gathered at intervals of 10 min for a solar plant of 50 m2 with a storage tank of 3 m3, including the equipment for domestic hot water production of a typical apartment building. This program has been used to obtain the design and dimensioning criteria of DHW solar plants under daily transient conditions throughout a year and more specifically the size of the storage tank for a multi storey apartment building. Comparison of the simulation results with the current Spanish regulation applicable, “Código Técnico de la Edificación” (CTE 2006), offers fruitful details and establishes solar facilities dimensioning criteria

Investigación e impacto ambiental de los edificios. La energía

This conference describes the main problems of energy use in face of the depleting of fosil resources, energy supply and emission of atmospheric toxic gases, green house effect gases and ozone depleting gases. The relevance of energy consumption in the environment impact is commented, as well as the key points for the posible evolution of the problem and in the appropriate technology research to cope with them In order to improve the energy and ecological efficiency of buidings. The main characteristics of present day technologies for the introduction of renewable energies in buidings are comented, dealing with their barriers for the widespread use. The most recent research on air conditioning using thermal solar energy with absorption machines is described, with application to Madrid.Se presenta la problemática actual del uso de la energía de cara al agotamiento de las fuentes fósiles, el abastecimiento y la contaminación atmosférica de gases tóxicos, de efecto invernadero y destructores de la capa de ozono. Se comenta la relevancia de la energía en el impacto ambiental de los edificios y se discuten los distintos aspectos que inciden en la posible evolución futura del problema y en la mejor estrategia de investigación tecnológica para tratar de mejorar la eficiencia energética y medioambiental de los edificios, especialmente en España. Se presentan las tecnologías actuales de introducción de las energías renovables en los edificios y se comentan sus más relevantes características, haciendo hincapié en las barreras para su difusión. Se describe la actividad más reciente de investigación en la climatización por energía solar haciendo uso de máquina de absorción, con aplicación a Madrid

Increasing the Operation Efficiency of Air Conditioning System for Integrated Power Plant on the Base of Its Monitoring

Increasing the Operation Efficiency of Air Conditioning System for Integrated Power Plant on the Base of Its Monitoring / E. Trushliakov, A. Radchenko, S. Forduy, A. Zubarev, A. Hrych // Advances in intelligent systems and computing. – 2020. – Т. 1113 AISC . – P. 351–360Abstract. The efficiency of reciprocating gas engines of integrated energy systems (IES) for combined electricity, heat and refrigeration generation is strictly influenced by their cyclic air temperatures. To evaluate the effect of gas engine cyclic air deep cooling, compared with conventional its cooling, the data on dependence of fuel consumption and power output of gas engine JMS 420 GS-N.L on its inlet air temperature at varying ambient air temperatures at the entrance of the radiator for scavenge air cooling were received. The results of treatment of gas engine efficiency monitoring proved non-effective operation of conventional chilling all the ambient air, coming into the engine room, because of increased air temperature at the inlet of turbocharger (TC), caused by heat influx from surroundings in the engine room. A new method of gas engine inlet air two-stage cooling at increased ambient air temperatures and advanced cyclic air cooling system with absorption lithium-bromide chiller and refrigerant ejector chiller was proposed. With this chilled water from absorption lithiumbromide chiller is used as a coolant in the first high-temperature stage of engine inlet air cooler and boiling refrigerant of ejector chiller in the second lowtemperature stage

AIgunos aspectos anatomoradiológicos de la displasia luxante de cadera

Ante la gran cantidad de parámetros propuestos para la confirmación radiográfica y valoración de la Displasia Luxante de Cadera, los autores realizan un análisis crítico de la inexactitud de algunos de ellos y analizan la correlación existente entre los ángulos Hilgenreiner o acetabular, de Zsboch, Moinar y Nagy, de Alsberg, y epsilon, sugiriendo a la vista de los resultados que el parámetro radiográfico de elección debe ser el ángulo de Alsberg, dada su correlación con los otros tres. ángulos