Publication: Evaluación experimental de máquinas de absorción de simple efecto de LiBr-H₂O de pequeña potencia condensadas por aire: sistemas re-coolign frente a sistema directo, aplicación en Instalaciones de Frío Solar
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2010
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2010-11-30
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Abstract
Las máquinas de absorción de LiBr-H₂O condensadas por aire aún no han tenido el desarrollo tecnológico ni comercial suficiente para reemplazar a las máquinas de absorción condensadas por agua, y mucho menos a las de compresión mecánica. Hasta donde la autora conoce, por el momento sólo ha salido al mercado una máquina de simple efecto condensada por aire que utiliza un sistema de enfriamiento indirecto, que denominaremos en adelante sistema recooling. Tampoco se tiene constancia experimental (sólo teórica) del beneficio del enfriamiento directo por aire del absorbedor y del condensador, en adelante sistema directo, respecto de un sistema re-cooling; ni se sabe que exista en el mercado alguna máquina de absorción de simple efecto de pequeña potencia y reducidas dimensiones que utilice el sistema directo y la energía solar como energía motriz. Con esta tesis se pretende contribuir a la comercialización de una máquina de estas características para uso residencial. La tesis se compone de nueve capítulos que se comentan brevemente a continuación. El capítulo 1, es una introducción donde se explica el motivo por el que puede resultar de interés la utilización de máquinas de absorción de LiBr-H₂O condensadas por aire alimentadas con energía solar en el sector residencial. En el capítulo 2, se realiza una breve descripción de la tecnología de absorción. Se presenta la situación del mercado actual, en el que se puede observar la desproporción existente entre el número de máquinas condensadas por agua y el número de máquinas condensadas por aire. También se hace constar el protagonismo que en los últimos años está adquiriendo el llamado “frío solar”, y cómo la combinación formada por los campos de colectores solares y las máquinas de absorción se va abriendo camino y ganando poco a poco mayor interés a nivel mundial. En el capítulo 3 se muestran las características de la única máquina de simple efecto de LiBr-H₂O condensada por aire con sistema re-cooling que ha salido al mercado, la Rotartica 045v. En el capítulo 4 se presentan los resultados experimentales obtenidos del ensayo de la máquina Rotartica 045v. El objetivo es, por un lado, probar su actuación con temperatura exterior de bulbo seco entre 30ºC y 40ºC, y por otro lado, a partir de los resultados obtenidos, diseñar un campo de colectores solares capaz de proporcionar la temperatura y el calor demandados por la máquina. En la experimentación, se utilizó como fuente de calor un tanque de aceite térmico calentado por resistencias eléctricas y un fancoil para climatizar el local. En el capítulo 5, se describe la instalación solar que sirve de fuente de calor a las máquinas condensadas por aire de simple efecto de LiBr-H₂O. La instalación consta de tres circuitos, un intercambiador de calor de placas externo y un tanque de almacenamiento de calor con estratificación. En el capítulo 6, se muestran los resultados experimentales obtenidos con la instalación formada por la instalación solar descrita en el capítulo 5, la máquina de absorción Rotartica 045v y el fancoil del local a climatizar. Se presentan temperaturas, potencias, rendimiento de colectores, rendimiento de la instalación solar, CEE de la máquina y rendimiento de la instalación global para tres días característicos con temperatura exterior de bulbo seco máxima de 30ºC, 35ºC y 40ºC, respectivamente. También se presentan resultados de un período estacional comprendido entre los meses de Junio y Septiembre. En el capítulo 7, se describe un prototipo de máquina de absorción de LiBr-H₂O de simple efecto condensada por aire con sistema directo y absorbedor adiabático construido en el Laboratorio de Bombas de Calor de la Planta Experimental de Energía Solar del Consejo Superior de Investigaciones Científicas (CSIC). Se presentan resultados experimentales de la instalación formada por el campo de colectores descrito en el capítulo 5, el prototipo del CSIC y el fancoil del local a climatizar. Se han elegido dos días de ensayo en los que se muestra: temperaturas, potencias, rendimiento de colectores, rendimiento de la instalación solar, CEE de la máquina y rendimiento de la instalación global. También se muestra un resumen de resultados de 10 días de experimentación. En el capítulo 8, se realiza la comparación, a partir de los resultados experimentales, de la máquina comercial con sistema re-cooling y del prototipo del CSIC con sistema directo desde el punto de vista de los fluidos exteriores. Se elige para esta comparación un día de trabajo con cada máquina, con temperatura exterior máxima alrededor de 37ºC. En ambos casos se utiliza el campo solar como fuente de calor. En el capítulo 9 se muestran las conclusiones de la tesis y los trabajos futuros, como la optimización de los componentes del prototipo para su próxima incorporación al mercado o la divulgación de resultados obtenidos con el prototipo de simple-doble efecto.---------------------------------------------------------------------------------------------------------------------------------------------------------------
The air-cooled LiBr-H₂O absorption chillers have had neither enough technological nor commercial development to replace the water-cooled absorption chillers yet, and even less the mechanical compression ones. As far as the author knows, at the moment, only one air-cooled single effect chiller, with an indirect system, denominated from now on re-cooling system, has been commercialised. There is not either an experimental (only theoretical) evidence of the advantage of using a direct air-cooled system instead of an indirect one, and it is not known if in the market exists a single effect absorption chiller of small power and size with a direct air-cooled system and driven by solar energy. With this Thesis, we are trying to contribute to the commercialisation, for a residential use, of a chiller of such characteristics. The Thesis consists of nine chapters which are briefly commented next. Chapter 1 is an introduction where it is explained the reason why it may turn out interesting the use of air-cooled LiBr-H₂O absorption chillers driven by solar energy in the residential sector. In Chapter 2, a brief description of the absorption technology is carried out. The current market situation is displayed, where a disproportion between the amount of water-cooled machines and air-cooled ones can be observed. It is also remarkable the main role that the “solar cooling” is acquiring for the last years and the way in which the combination formed by the solar collector fields and the absorption chillers is finding a way and gaining little by little more interest at a world-wide level. In Chapter 3, the characteristics of the only air-cooled LiBr-H₂O single effect absorption chiller with a re-cooling system which has gone out to the market, Rotartica 045v, are shown. In Chapter 4, the experimental results obtained with Rotartica 045v are displayed. The objectives were, on the one hand, to test the chiller at outside dry bulb temperatures between 30ºC and 40ºC, and, on the other hand, to desing a solar collector filed able to provide the heat and temperature required by the machine. In the tests, a thermal oil tank heated by electrical resistances was used as the heat source. In Chapter 5, the solar facility used as a heat resource is described. It consists of three loops, an external plate heat exchanger and a stratified storage tank. In Chapter 6, the experimental results obtained with the facility formed by the solar facility described in Chapter 5, the Rotartica 045v absorption chiller and the fancoil are shown. They are presented: The temperatures, the heats, the solar field efficiency, the COP and the solarcooling facility efficiency for three days with maximum outside dry bulb temperatures of 30ºC, 35ºC and 40ºC, respectively. The results of a seasonal period between June and September are also displayed. In Chapter 7, it is described a Prototype of a direct air-cooled LiBr-H₂O single effect absorption chiller with an adiabatic absorber, built at the Heat Pump Laboratory (CSIC).Experimental results of the solar cooling facility formed by the collector field described in Chapter 5, the Prototype and the fancoil are displayed. The results related to: the temperatures, the heats, the COP, and the efficiencies for two days and for a ten-day experimentation period, are shown. In Chapter 8, a comparison between the results obtained from the commercial absorption chiller with the re-cooling system and the results obtained from the prototype with the direct air-cooled system, from the point of view of the external fluids, is carried out. A day work with each machine has been selected for this comparison, with a maximum outside dry bulb temperature around 37ºC. For both cases, the solar facility was used as the heat source. In Chapter 9, the Thesis conclusions the future works are displayed, like the optimization of the prototype components for its next incorporation to the market, or the spreading of the experimental results obtained with the air-cooled single-double effect prototype.
The air-cooled LiBr-H₂O absorption chillers have had neither enough technological nor commercial development to replace the water-cooled absorption chillers yet, and even less the mechanical compression ones. As far as the author knows, at the moment, only one air-cooled single effect chiller, with an indirect system, denominated from now on re-cooling system, has been commercialised. There is not either an experimental (only theoretical) evidence of the advantage of using a direct air-cooled system instead of an indirect one, and it is not known if in the market exists a single effect absorption chiller of small power and size with a direct air-cooled system and driven by solar energy. With this Thesis, we are trying to contribute to the commercialisation, for a residential use, of a chiller of such characteristics. The Thesis consists of nine chapters which are briefly commented next. Chapter 1 is an introduction where it is explained the reason why it may turn out interesting the use of air-cooled LiBr-H₂O absorption chillers driven by solar energy in the residential sector. In Chapter 2, a brief description of the absorption technology is carried out. The current market situation is displayed, where a disproportion between the amount of water-cooled machines and air-cooled ones can be observed. It is also remarkable the main role that the “solar cooling” is acquiring for the last years and the way in which the combination formed by the solar collector fields and the absorption chillers is finding a way and gaining little by little more interest at a world-wide level. In Chapter 3, the characteristics of the only air-cooled LiBr-H₂O single effect absorption chiller with a re-cooling system which has gone out to the market, Rotartica 045v, are shown. In Chapter 4, the experimental results obtained with Rotartica 045v are displayed. The objectives were, on the one hand, to test the chiller at outside dry bulb temperatures between 30ºC and 40ºC, and, on the other hand, to desing a solar collector filed able to provide the heat and temperature required by the machine. In the tests, a thermal oil tank heated by electrical resistances was used as the heat source. In Chapter 5, the solar facility used as a heat resource is described. It consists of three loops, an external plate heat exchanger and a stratified storage tank. In Chapter 6, the experimental results obtained with the facility formed by the solar facility described in Chapter 5, the Rotartica 045v absorption chiller and the fancoil are shown. They are presented: The temperatures, the heats, the solar field efficiency, the COP and the solarcooling facility efficiency for three days with maximum outside dry bulb temperatures of 30ºC, 35ºC and 40ºC, respectively. The results of a seasonal period between June and September are also displayed. In Chapter 7, it is described a Prototype of a direct air-cooled LiBr-H₂O single effect absorption chiller with an adiabatic absorber, built at the Heat Pump Laboratory (CSIC).Experimental results of the solar cooling facility formed by the collector field described in Chapter 5, the Prototype and the fancoil are displayed. The results related to: the temperatures, the heats, the COP, and the efficiencies for two days and for a ten-day experimentation period, are shown. In Chapter 8, a comparison between the results obtained from the commercial absorption chiller with the re-cooling system and the results obtained from the prototype with the direct air-cooled system, from the point of view of the external fluids, is carried out. A day work with each machine has been selected for this comparison, with a maximum outside dry bulb temperature around 37ºC. For both cases, the solar facility was used as the heat source. In Chapter 9, the Thesis conclusions the future works are displayed, like the optimization of the prototype components for its next incorporation to the market, or the spreading of the experimental results obtained with the air-cooled single-double effect prototype.
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Tecnología de la climatización, Máquinas de absorción, Frío solar