Dissertations / Theses on the topic 'Adsorption Cooling'

Heat driven adsorption cycles use heat sources ranging in temperature from 80 - 150 °C to provide cooling, and have been used in both air conditioning and refrigeration applications. Adsorbent heat pumps operate with low cost, simple components, and very little vibration, making them appealing as an alternative heat pump technology. However, they have been limited thus far to commercial and industrial scale applications. To date, adsorption systems have predominantly used natural or industrial waste streams as heat sources in the 10s of kW range. This work expands the scope of adsorption applications to include heat driven cooling at small capacities (watts) and mobile cooling without electronic controls. Autonomous heat driven adsorption system controls are proposed and tested for these systems. Component and system level models are developed for design and assessment. Major trends in system performance with scale are identified and the causes for these scaling effects are presented. New adsorbent bed designs are proposed and modeled for small-scale adsorption systems. The small-scale adsorbent bed designs are fabricated and tested. Models are validated and refined based on the experimental results. Through a combination of modeling and experimental results, this work demonstrates the feasibility of adsorption system application at capacities that two orders of magnitude lower than any previously demonstrated work.

A cutting edge man-portable AVMEC cooling garment was demonstrated to be able to provide sufficient cooling for personnel working at mediate activity loads. Studies were first carried out in a well controlled vacuum desiccator at room temperature to elucidate the effects of several key parameters on the performance of an AVEC device, which was similar to AVMEC except that membrane was not involved. Under the best condition, an average cooling capacity of 179 W/M2 was achieved in a period of four hours and cooling continued at a slowly declining rate for another four hours afterward. The temperature of water was maintained at approximately 12.5 oC after the pseudo steady state was established. Then, it was shown that the AVMEC cooling pads were able to provide a cooling capacity of 277.4 W/m2 in a 37 oC ambient environment (incubator). The temperature of the cooling core surface was maintained in a range of 20 – 21.8 oC in the one-hour test period. No power supply was required except for the initialization stage, which took 5 minutes. Furthermore, human subject tests with or without wearing NWBC (Nuclear Warfare Biological and Chemical) suit demonstrated that, a AVMEC garment composed of 12 cooling pads were able to maintain the core body temperature of the subjects below 38.5 oC for up to 90 minutes while the subject was walking on a treadmill at a speed of 2 miles per hour in an environment of 40 oC and 50% RH (relative humidity). These results indicate that the AVMEC garment is a promising man-portable personal cooling technology.

Due to the fact that the worldwide energy consumption caused by cooling devices in buildings has been increasing steadily and also the fact that the pressure has been rising to provide this cooling energy with environmentally friendly technology, solar powe.re~ DEC-systems (Desiccative and Evaporative Cooling) have begun capturing increasing interest over the past few years. , However, up to now little experience has been gained in the operation of these systems and thus currently little information is available about the performance, the efficiency, the control strategy and the best component choice. This lack of knowledge has resulted in a low rate of acceptance of, this technology so far. The studies presented in this thesis serve as a contribution to the advancement of DEC technology by providing fundamental knowledge about the operation and attainable performance of these systems. A comprehensive study of desiccant wheels was undertaken which provides detailed information about the operation and the achievable dehumidification performance of this component. A detailed simulation model for desiccant wheels was developed and verified with measured data from a desiccant wheel test plant. Additionally, two commercially used DEC-systems (one in a public library in Spain and the other in a plastics processing factory building in Germany) were monitored for the purposes of evaluating the performance of these systems and resolving existing problems in their operation and control strategies. In spite of the generally positive validation of the planned and expected cooling performances in both cases, the monitoring also showed that there are considerable possibilities· for improvement, especially with the regulation of the system.

Environmental concerns regarding climate change and ozone depletion urge for a paradigm shift in the cooling production. The cooling demand exhibits an alarmingly increasing trend, thus its satisfaction in a sustainable manner is imperative. Adsorption cooling systems (ACSs) are a potential candidate for a sustainable future of cooling production, since they can utilize solar energy or waste heat, as well as they can employ substances with zero ozone depletion and global warming potential. The objective of this thesis is to contribute to the investigation and improvement of ACSs, through the development of two computational models - which approach ACSs from different perspectives - and their respective utilization for the conduction of related numerical studies. The first research direction focuses on the design of the adsorption reactor, the most vital component of ACSs. Its geometrical configuration is determinant for the system performance. The reactor design is a crucial task since it creates a dichotomy between the two performance indicators - the Specific Cooling Power (SCP) and the Coefficient of Performance (COP). Individual optimizations based on the SCP and the COP would result in completely opposite geometrical configurations. A computational model for the simulation of adsorption packed bed reactors was developed, capable of simulating any potential reactor geometry. A multi-timestep approach is adopted, resulting in a drastic reduction of the computational cost of the simulations. Verification and validation assessments were performed in order to evaluate the reliability of the model. Two major studies were conducted within this research direction. The first aspires to provide a comparison between five reactor geometries, motivated by the lack of comparability across different studies in the literature. Thirteen cases of each geometry are simulated, by varying the fin thickness, fin length and solid volume fraction. The second study pertains to a thorough investigation of a geometry that remained underexplored hitherto - the hexagonal honeycomb adsorption reactor. A parametric study is conducted with respect to the three dimensions that define the geometry, as well as for various operating conditions. The second research direction is dedicated to the investigation of adsorption cooling systems, and in particular, to their integration within a wider thermal system, a solar-cooled building. Such integration is not straight-forward due to thermal inertia effects and the inherent cyclic operation of ACSs, as well as due to the dependence on an intermittent source and an auxiliary unit, with a clear objective to prioritize solar energy. A numerical model was developed using 1-d models for the adsorption reactors and 0-d models for the evaporator and condenser. The model is validated against experimental results found in the literature. The model is coupled to the generic optimization tool GenOpt, thus allowing the conduction of optimization studies. The ACS model is then coupled to solar collectors and thermal storage models, as well as to a building model. The latter was previously developed in the CTTC laboratory. This coupling results in a comprehensive simulation tool for adsorption-based solar-cooled buildings. A case study for a solar-cooled office is considered, with the objective to investigate the potential of satisfying its cooling demand using solar energy. A control strategy is proposed based on variable cycle duration, using optimized values for the instantaneous operating conditions. The variable cycle duration approach allows to satisfy the cooling demand using significantly less solar collectors or less auxiliary energy input. The potential carbon dioxide emissions avoidance is calculated between 28.1-90.7% with respect to four scenarios of electricity-driven systems of different performance and carbon emission intensity.
La preocupació mediambiental sobre el canvi climàtic i l'esgotament d'ozó exigeix un canvi de paradigma en la producció de fred. La demanda de refredament mostra una tendència alarmant creixent, així és imperatiu satisfer-la de forma sostenible. Els sistemes de refredament per adsorció (ACS) són un candidat per a un futur sostenible de la producció de fred, ja que poden utilitzar energia solar o calor residual, emprant substàncies amb zero potencial d'esgotament d'ozó i d'escalfament global. L'objectiu d'aquesta tesi és contribuir a la investigació i millora dels ACS, mitjançant el desenvolupament de dos models computacionals - que aborden els ACS des de diferents perspectives - i la seva utilització per a la realització d'estudis numèrics. La primera línia d'investigació se centra en el disseny del reactor d'adsorció, el component més important dels ACS. La seva configuració geomètrica és determinant pel rendiment de sistema. El seu disseny és una tasca crucial, ja que crea una dicotomia entre la potència específica de refrigeració (SCP) i el coeficient de rendiment (COP). Les optimitzacions individuals basades en el SCP i el COP resultarien a configuracions geomètriques completament oposades. S'ha desenvolupat un model computacional per a la simulació de reactors d'adsorció tipus "packed bed", capaç de simular reactors de qualsevol geometria. S'adopta una estratègia multi-timestep, que permet una dràstica reducció del cost computacional de les simulacions. La fiabilitat del model es va avaluar a través de processos de verificació i validació. Dins d'aquesta línia de recerca es van realitzar dos estudis principals. El primer aspira a proporcionar una comparació entre cinc geometries de reactors, motivat per la falta de comparabilitat entre diferents estudis en la literatura. Es simulen tretze casos de cada geometria, variant el gruix de les aletes, la seva longitud i la fracció de volum de sòlid. El segon estudi presenta la investigació d'una geometria sub-explorada previament, el reactor d'adsorció de honeycomb hexagonal. Es realitza un estudi paramètric pel que fa a les tres dimensions que defineixen la geometria, així com per a diverses condicions de funcionament. La segona línia de recerca es dedica a la investigació dels ACS. i en particular, a la seva integració dins d'un sistema tèrmic més ampli, un edifici refredat per energia solar. Aquesta integració no és senzilla a causa de la inèrcia tèrmica i a el funcionament cíclic inherent dels ACS, així com a la dependència d'una font intermitent i d'un sistema auxiliar, amb l'objectiu de prioritzar l'energia solar. S'ha desenvolupat un model numèric utilitzant models 1-d pels reactors i models 0-d per l'evaporador i el condensador. El model es va validar amb resultats experimentals trobats en la literatura. El model es va acoblar amb l'eina d'optimització genèrica GenOpt, permetent així estudis d'optimització. El model ACS es va acoblar amb models de col·lectors solars, emmagatzematge tèrmic i amb un model d'edifici. Aquest últim va ser desenvolupat prèviament al CTTC. Aquest acoblament resulta a una eina de simulació integral per a edificis refredats per energia solar utilitzant adsorció. Es considera un cas d'estudi per a una oficina refredada per energia solar, amb l'objectiu d'investigar el potencial de satisfer la seva demanda de fred utilitzant energia solar. Es proposa una estratègia de control basada en la duració variable del cicle, utilitzant valors optimitzats per a les condicions instantànies. La durada variable d'el cicle permet satisfer la demanda utilitzant una quantitat significativament menor de col·lectors solars o un menor aportació d'energia auxiliar. Les emissions de CO2 evitades es calculen entre 28.1-90.7% respecte a quatre escenaris de sistemes elèctrics de diferent rendiment i intensitat d'emissions de carboni.

This thesis investigates the feasibility of producing electricity and cooling simultaneously utilising low-grade heat sources by incorporating an expander within the adsorption cooling system or by integrating an Organic Rankine Cycle with water adsorption cooling system. Advanced physical adsorbent materials have been investigated for the first time to generate cooling and electricity simultaneously utilising CPO-27(Ni), MIL101(Cr), and AQSOA-Z02 and compared to commonly used Silica-gel. Two innovative configurations of water adsorption systems for cooling and electricity were investigated. In the first configuration, the two-bed basic adsorption cooling system (BACS) is improved by including an expander within the system. In the second configuration, the BACS and ORC cycle are integrated. Four different scenarios of systems integration based on the way of powering the ORC and the adsorption system were investigated. Also, detailed CFD simulations of small-scale radial inflow turbines are developed for both configurations. Also, a novel experimental facility is developed to integrate ORC with two-bed adsorption cooling system to validate the numerical models and proof the concept of producing power as well as cooling, where maximum specific cooling power of 252 W/kgads and specific power and of 162 W/kgads can be achieved with maximum deviation of less than 17%.

[EN] This PhD study deals with the modelling of an adsorption system designed to provide air conditioning for vehicles, and is driven by the waste heat available from the water/glycol cooling circuit of the engine. The system is based on the sequential heating/cooling of two sorption beds containing a solid sorption material which desorbs or adsorbs water vapour. The condensation of the vapour is carried out by a cooling circuit while the subsequent evaporation of the condensed liquid is employed to produce the cooling effect, generating chilled water, which is then employed to cool down the air of the cabin. The developed model is fully dynamic and is based on zero-dimensional lumped parameter models for all the necessary components of the overall system including the engine, the beds, the heating circuit, the cooling circuit, the chilled water circuit and the vehicle cabin. The sorption bed model takes into account the non-equilibrium of the adsorption and desorption processes and is able to work with any kind of adsorbent materials, but the study has been restricted to silica gel and zeolite which are among the most appropriate materials for this application. The model is employed to simulate a standard driving cycle of a vehicle, evaluating the instantaneous available heat from the engine cooling system and the dynamic behaviour of the described sorption A/C system, resulting in the estimation of the evolution of the cabin temperature along the cycle. The model of the overall system has been developed under the MATLAB Simulink programming environment. The model of the adsorption system has been first validated against experimental results, showing its excellent capabilities to predict the dynamic behaviour of the system. The model was then used to analyse the influence of the main design parameters of the bed and the main operation parameters on the system's performance: cooling capacity and coefficient of performance (COP). This was done in order to provide rules for the optimal design and operation of this kind of systems. Finally, the model has been employed to analyse the overall system (engine, adsorption system, heating and cooling circuits, chilled water circuit and cabin) performance along a standard driving cycle, under various operation strategies with regards to the initial state of the adsorbent material in the beds, and operation conditions both for a car and a truck. The results show the difficulties of activating the system at the initial periods of the cycle, when the engine is warming up, and the difficulties to synchronise the operation of the system with the availability of waste energy. They also highlight the limitation in capacity of the designed system, showing that it would not able to fulfil the comfort requirements inside the cabin in hot days or after soaking conditions. Part of this PhD study was carried out in the frame of an R&D project called "Thermally Operated Mobile Air Conditioning Systems - TOPMACS", financially supported by the EU under the FP6 program, which was devoted to the evaluation of the feasibility and performance of potential sorption system solutions for the air conditioning of vehicles.
[ES] Esta tesis doctoral se centra en el modelado de un sistema de adsorción diseñado para proporcionar aire acondicionado de vehículos a partir del calor residual disponible en el circuito de refrigeración de agua/glicol del motor. El sistema se basa en el calentamiento/enfriamiento secuencial de dos reactores que contienen un material adsorbente sólido que desorbe o absorbe vapor de agua. La condensación del vapor se lleva a cabo mediante un circuito de refrigeración, mientras que la posterior evaporación del agua condensada se emplea para producir agua fría, que se emplea finalmente en enfriar el aire de la cabina. El modelo desarrollado es completamente dinámico y se basa en modelos cero dimensionales de parámetros concentrados, para todos y cada uno de los componentes del sistema global incluyendo el motor, los reactores, el circuito de calentamiento, el circuito de enfriamiento, el circuito de agua fría y la cabina del vehículo. El modelo del reactor contempla el no equilibrio de los procesos de adsorción o desorción y es capaz de trabajar con cualquier par de materiales adsorbentes. No obstante el estudio se ha restringido a gel de sílice y zeolita que se encuentran entre los materiales más adecuados para esta aplicación. El modelo se emplea para simular un ciclo de conducción estándar del vehículo, evaluando el calor disponible instantáneamente en el sistema de refrigeración del motor, y el comportamiento dinámico del sistema descrito adsorción-Aire Acondicionado, permitiendo como resultado principal la estimación de la evolución de la temperatura de la cabina a lo largo el ciclo. El modelo del sistema global se ha desarrollado en el marco del entorno de programación MATLAB Simulink. El modelo del sistema de adsorción se ha validado primero contra resultados experimentales demostrando las excelentes capacidades del modelo para predecir el comportamiento dinámico del sistema. A continuación, el modelo se ha aplicado para analizar la influencia de los principales parámetros de diseño del reactor, y de los principales parámetros de operación, sobre el rendimiento del sistema: la capacidad y coeficiente de operación (COP), con el fin de proporcionar directrices para el diseño y operación óptima de este tipo de sistemas. Por último, el modelo ha sido empleado para analizar el funcionamiento y prestaciones del sistema en su conjunto (motor, sistema de absorción, los circuitos de calefacción y refrigeración, circuito de agua fría, y la cabina) a lo largo de un ciclo de conducción estándar, bajo diferentes estrategias de operación en lo que se refiere al estado inicial del material adsorbente en los reactores, y las condiciones de operación, para el caso de un coche, y para el de un camión. Los resultados muestran las dificultades de la activación del sistema en los periodos iniciales del ciclo, cuando el motor se está calentando, y las dificultades para sincronizar el funcionamiento del sistema con la disponibilidad de energía térmica excedente del motor, así como la limitación en la capacidad de enfriamiento del sistema diseñado, que no resulta capaz de satisfacer los requerimientos mínimos de confort dentro de la cabina en los días calurosos o de enfriarlo con suficiente rapidez cuando el vehículo ha estado estacionado bajo el sol durante varias horas. Parte de este estudio de doctorado se ha llevado a cabo en el marco de un proyecto de I + D denominado " Thermally Operated Mobile Air Conditioning Systems - TOPMACS", financiado parcialmente por la UE en el marco del programa FP6, y que perseguía la evaluación de la viabilidad y el potencial de aplicación de soluciones de sistemas de adsorción activadas por el calor residual del motor para el aire acondicionado de vehículos.
[CAT] Aquesta tesi doctoral es centra en el model d'un sistema d'adsorció dissenyat per a proporcionar aire acondicionat a vehicles a partir de la calor residual disponible al circuit de refrigeració d'aigua / glicol del motor. El sistema es basa en l'escalfament / refredament seqüencial de dos reactors que contenen un material adsorbent sòlid que desorbeix o absorbeix vapor d'aigua. La condensació del vapor es porta a terme mitjançant un circuit de refrigeració, mentre que la posterior evaporació de l'aigua condensada s'utilitza per a produir aigua freda, que s'empra finalment en refredar l'aire de la cabina. El model desenvolupat és completament dinàmic i es basa en models zero dimensionals de paràmetres concentrats, per a tots i cada un dels components del sistema global incloent el motor, els reactors, el circuit d'escalfament, el circuit de refredament, el circuit d'aigua freda i la cabina del vehicle. El model del reactor contempla el no equilibri dels processos d'adsorció o desorció i és capaç de treballar amb qualsevol parell de materials adsorbents. No obstant això, l'estudi s'ha restringit a gel de sílice i zeolita que es troben entre els materials més adequats per a aquesta aplicació. El model s'utilitza per a simular un cicle de conducció estàndard del vehicle, avaluant la calor disponible instantàniament en el sistema de refrigeració del motor, i el comportament dinàmic del sistema descrit Adsorció-Aire Acondicionat, permetent com a resultat principal l'estimació de l'evolució de la temperatura de la cabina al llarg del cicle. El model del sistema global s'ha desenvolupat en l'entorn de programació MATLAB Simulink. El model del sistema d'adsorció s'ha validat primer amb resultats experimentals demostrant les excel¿lents capacitats del model per a predir el comportament dinàmic del sistema. A continuació, el model s'ha aplicat per analitzar la influència dels principals paràmetres de disseny del reactor, i dels principals paràmetres d'operació, sobre el rendiment del sistema: la capacitat i coeficient d'operació (COP), amb la finalitat de proporcionar directrius per al disseny i operació òptima d'aquest tipus de sistemes. Finalment, el model ha estat utilitzat per analitzar el funcionament i prestacions del sistema en el seu conjunt (motor, sistema d'absorció, els circuits de calefacció i refrigeració, circuit d'aigua freda, i la cabina) al llarg d'un cicle de conducció estàndard, sota diferents estratègies d'operació pel que fa a l'estat inicial del material adsorbent en els reactors, i les condicions d'operació, per al cas d'un cotxe, i per al d'un camió. Els resultats mostren les dificultats de l'activació del sistema en els períodes inicials del cicle, quan el motor s'està escalfant, i les dificultats per sincronitzar el funcionament del sistema amb la disponibilitat d'energia tèrmica excedent del motor, així com la limitació en la capacitat de refredament del sistema dissenyat, que no resulta capaç de satisfer els requeriments mínims de confort dins de la cabina en els dies calorosos o de refredar amb suficient rapidesa quan el vehicle ha estat estacionat sota el sol durant diverses hores. Part d'aquest estudi de doctorat s'ha dut a terme en el marc d'un projecte d'I + D denominat "Thermally Operated Mobile Air Conditioning Systems - TOPMACS", finançat parcialment per la UE en el marc del programa FP6, i que perseguia l'avaluació de la viabilitat i el potencial d'aplicació de solucions de sistemes d'adsorció activats per la calor residual del motor per a l'aire condicionat de vehicles.
Verde Trindade, M. (2015). MODELLING AND OPTIMIZATION OF AN ADSORPTION COOLING SYSTEM FOR AUTOMOTIVE APPLICATIONS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/54120
TESIS

Growing need for application of electronics at temperatures beyond their rated limit, (usually > 150 °C) and the non availability of high temperature compatible electronics necessitates thermal management solutions that should be compact, scalable, reliable and be able to work in environments characterized by high temperature (150 -250 °C), mechanical shock and vibrations. In this backdrop the proposed research aims at realization of an adsorption cooling system for evaporator temperatures in the range of 140 °C-150 °C, and condenser temperature in the range of 160 °C-200 °C. Adsorption cooling systems have few moving parts (hence less maintenance issues), and the use of Thermo-Electric (TE) devices to regenerate heat of adsorption in between adsorbent beds enhances the compactness and efficiency of the overall 'ThermoElectric-Adsorption' (TEA) system. The work presented identifies the challenges involved and respective solutions for high temperature application. An experimental set up was fabricated to demonstrate system operation and mathematical models developed to benchmark experimental results. Also, it should be noted that TEA system comprises TE and adsorption chillers. A TE device can be a compact cooler in its own right. Hence a comparison of the performance of TEA and TE cooling systems has also been presented.

In this thesis, yearly performance of the solar adsorption cooling system which is proposed to be installed to a residential building in Antalya is theoretically investigated in detail. Firstly, thermodynamic designs of the adsorption cooling cycle for three different types of cycles which are intermittent, heat recovery and heat &
mass recovery cycles are presented. Secondly, adsorption characteristics of three adsorbent/adsorbate pairs which are zeolite-water, silica gel-water and activated carbon-methanol are given. Following this, load side (i.e., building) of the system is designed and parameters that should be considered in building design are presented. Then, solar-thermal cooling system design methodology with an emphasis on solar fraction is presented. In addition, system parameters effecting the performance of the adsorption cooling system are analyzed and results are presented. Finally, economic analysis is done in order to understand the economic feasibility of the solar-thermal cooling systems compared to conventional cooling systems. TRNSYS is used for the yearly simulations and an integrated model of the overall system is developed in TRNSYS. Since energy consumption and performance investigations of environment-dependent systems such as building HVAC, refrigeration systems and solar collectors usually require weather information, typical meteorological year (TMY) data for Antalya is also generated in order to be used in the analysis of the system parameters.

Energy consumption is continuously increasing around the world and this situation yields research to find sustainable energy solutions. Demand for cooling is one of the reasons of increasing energy demand. This research is focused on one of the sustainable ways to decrease energy demand for cooling which is the solar-powered adsorption cooling system. In this study, general theoretical performance trends of a solar-powered adsorption cooling system are investigated using TRNSYS and MATLAB. Effects of different cycle enhancements, working pairs, operating and design conditions on the performance are analyzed through a series of steady and seasonal-transient simulations. Additionally, a normalized model is presented to investigate the effects of size of the system, need for backup power, collector area and mass of adsorbent. Results are presented in terms of values and ratios of cooling capacity weighted COP. For the conditions explored, the thermal wave cycle, wet cooling towers, high evaporation temperatures and evacuated tube collectors produced the highest COP values. Moreover, the heat capacity of the adsorbent bed and its shell should be low for the simple and heat recovery cycles and the adsorbent bed should be cooled down to the condensation temperature for all cases to achieve the highest possible COP. The selection of working pair should depend on the temperature of the available heat source (solar energy in this study) since each working pair has a distinct operating temperature range. Furthermore, there is always a need for backup power for the analyzed location and the system.

This thesis work is intended to investigate energy and exergy performance of a low power prototype solar air conditioning system based on sorption materials. Its performance is analyzed in the light of both the First and Second Law of Thermodynamics and compared with conventional HVAC systems as well as with a further solar cooling technology based on desiccant wheels (Solar DEC). The adsorption machine based solar cooling plant was thoroughly designed and its thermal performance analysed in several operating conditions and then optimized according to a First Law and Second Law approach. The sensitivity theory was also applied in order to investigate the system response to deviations of some state variables from their nominal values. In this context a number of sensitivity coefficients were determined in relation to the most relevant design parameters. That provided useful information for control strategies in dynamic regime and hints for systems design and optimization. A general model was also developed and implemented in a computer code for the determination of the thermophysical properties of humid air streams when leaving a desiccant wheel, based on the Jurinak Method. An important outcome of this research work is that solar energy, with its relatively low energy potential -when made available by a low-to-medium temperature collector, such as with adsorption machines or desiccant wheels-, is a more appropriate energy source to air-conditioning than conventional systems, from a true thermodynamic point of view. In this sense its technology should be developed and its use should be encouraged.

Orientador: Vivaldo Silveira Junior
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-04T02:26:51Z (GMT). No. of bitstreams: 1 Afonso_MarcosRodriguesAmorim_D.pdf: 11650736 bytes, checksum: 7e5d5f2552930a2f6fab23787c54259b (MD5) Previous issue date: 2005
Doutorado
Engenharia de Alimentos
Doutor em Engenharia de Alimentos

Adsorption cooling systems are considered to be an important alternative to conventional heating and cooling systems, however at present it has had limited commercial applications. This is because of the low thermal heat transfer during its operations cycle from heat exchanger to adsorbent packing. The main objective of this study is the design and CFD simulation of a new compact copper wire woven fins heat exchanger and silica gel adsorbent bed used as part of an adsorption cooling system. This type of heat exchanger has a large surface area because of the wire woven fins design but can still be design as a small compact heat exchanger. It is proposed that this will help improve the coefficient of performance (COP) of the cycle and improve the heat transfer rate in the system.

The energy consumption rate of non-OECD countries rises about 2.3 percent per year as compared to the energy consumption rate of OECD countries which is 0.6 percent. If developing countries use energy efficient technology and integrate renewable energy systems in the new building their carbon dioxide emission rate reduces by 25 to 44 percent.  However, even now, renewable energy integrated buildings are hardly considered while constructing them.   This thesis work focuses on the study of solar cooling system options for residential house in Bahir Dar city. To meet the demand of housing in the city, different type of apartments and villa houses are under construction.  Case study was made focusing on two types of residential houses (condominium apartment and Impact Real-estate Villa house) to determine the cooling load and to select cooling system.   Simulation results of IDA ICE software show that the average operative temperatures and cooling loads for condominium apartment and Real-estate Vila are 31.8oC and 30.7oC, 5.53 kW and 5.73 kW respectively. Most of the residences are not satisfied at this operating temperature.   There are different types of solar cooling systems.  Solar Sorption cooling systems are commonly used which can also be classified in to absorption, adsorption and desiccant cooling systems.  Solar adsorption cooling systems are easy to manufacture locally as compared to solar absorption cooling systems. They do not have moving parts. Some of the working medium pairs used in adsorption cooling system are: Activated Carbon/Ammonia, Silica gel/ water, Zeolite/water. Adsorption chillier with Silica gel/ water as a working pair was selected since it can operate at regeneration/desorption temperature as low as 45oC coming from flat plate collectors.  At 75oC regeneration temperature, the system delivers 9oC chilled water temperature.   The selected solar adsorption chiller has been compared with kerosene based adsorption cooling system using HOMER software.  In this project, the optimization was limited on cost comparison between the two energy sources.  The solar based cooling system has lower working cost.   From cooling load simulation result direct solar irradiation is the highest source of cooling load for both houses. This gives an opportunity for passive solar cooling technology.

Syftet med detta examensarbete är att värdera och jämföra ett antal utvalda kyltekniker, med huvudfokus på värmedriven kyla. Dels för en specifik befintlig byggnad men även en generell jämförelse som kan ligga till grund för andra projekt. Arbetet är utförti samarbete med ÅF i Borlänge. Den specifika byggnaden som har undersökts är belägen i Borlänge och kyls idag av stadsvatten, och har en kyleffektpå 655kW. Borlänge Energis fjärrvärmenät ligger till grund för samtliga beräkningar och antaganden. Huvudsyftet har varit att jämföra de olika kylteknikerna ur ett ekonomiskt perspektiv, men även snudda vid ett miljöperspektiv. Utöver detta så var syftet att undersöka hur en fjärrvärmeleverantör ska kunna leverera kyla till sin kund, utan att behöva gräva ner nya fjärrkylledningar. De kyltekniker som jämförts i detta arbete är absorptionskyla, adsorptionskyla, sorptiv kyla & eldriven kompressorkyla. För att kunna jämföra de olika teknikerna har den totala livscykelkostnaden beräknas. Investeringskostnader och data har erhållits ifrån leverantörer genom kontakt med kunniga säljare. Driftkostnader har beräknats fram med hjälp av driftdata samt energipriser hos Borlänge Energi. Kostnader för installation, frakt och lyft är inte medräknade i detta arbete. För den befintliga byggnaden visade det sig att den mest kostnadseffektiva lösningen är absorptionskyla, tätt följt av att komplettera befintligt system med frikyla i form utav en kylmedelkylare. Absorptionskylan har väldigt låga driftkostnader under sommarhalvåret, då fjärrvärmepriset är som lägst. Dyrast av teknikerna är adsorptionskyla, tack vare den dyra investeringskostnadenoch dess låga verkningsgrad. Även för den generella jämförelsen visade det sig att den mest kostnadseffektiva lösningen är absorptionskyla, tätt följt av eldriven kompressorkyla. Absorptionskylan har mycket låga driftkostnader, men kompressorkylan har istället en lägre investeringskostnad och mycket bättre verkningsgrad. Om Borlänge Energi skulle sälja fjärrvärmeproducerad kyla under sommaren, så skulle de vid 655kW kyleffekt ha en återbetalningstid avett absorptionskylaggregat på endast 2 år. Skulle de istället ha en kyleffekt på 100kW skulle återbetalningstiden vara ca 5 år. Slutsatser kan dras ifrån detta arbete att byggnader med högre kyleffekt är mer fördelaktiga för värmedriven kyla.
The aim of this thesis is to evaluate and compare a number of selected chilling techniques, with a main focus on heat driven cooling. Mainly for an existing building, but also a more general comparison that can be used as a basis for other projects. This thesis has been carried out in cooperationwith ÅF in Borlänge.The building that has been investigated is located in Borlänge. All calculations and assumptions regarding the district heating network are based on Borlänge Energi’s district heating network. The main purpose has been to compare the different cooling techniques from an economical point of view, but also a slight comparison from an environmental point of view. In addition, the purpose has been to investigate how a district heating supplier can deliver cooling to its customers without having to dig down newdistrict cooling pipes. The cooling techniques compared in this thesis are absorption chillers, adsorption chillers, sorptive cooling and conventional electrical compression chillers. In order to compare the different techniques, the total life cycle cost has been calculated. Investment costs and data have been obtained from skillful salesmen representing variouscompanies. Operating costs have been calculated using data and energy prices from Borlänge Energi. Costs for installation, shipping and lifting are not included in this thesis. The most cost-effective solution for the existing building is to install an absorption chiller, closely followed by complementing the existing cooling system with free cooling. The absorption chillers has very low operating costs during the summer, when the price of the district heating is at its lowest. The most expensive technique are adsorption cooling, due to its expensive investment cost and its low efficiency. For the general comparison, it was found that the most cost-effective solution is absorption chiller as well, closely followed by the conventional compressor chiller. The absorption chillers has much lower operating costs than its competitors, but the compressor chiller has a lower investment cost and a much better efficiency. If Borlänge Energi were to sell district heat-produced cooling during the summerusing an adsorption chiller, they would have a payback time of only approximately 2 years, with a cooling power of 655kW. With a cooling power of 100 kW, the payback time would be approximately 5 years. Conclusions can be drawn from this thesis that buildings with higher cooling demand are better suited for heat-driven cooling.

Poor heat and mass transfer inside the adsorbent bed of thermal wave adsorption cooling cycles cause low system performance and is an important problem in the adsorbent bed design. In this thesis, a new adsorbent bed is designed, constructed and tested to increase the heat and mass transfer in the adsorbent bed. The adsorbent bed is constructed from a finned tube in order to enhance the heat transfer. Additionally, the finned bed geometry is theoretically modeled and the model is solved time dependently by using Comsol Multiphysics software program. The distributions of dependent variables, i.e. temperature, pressure and amount adsorbed, are simulated and plotted in Comsol Multiphysics. In the model, the dependent variables are computed by solving the energy, mass and momentum transfer equations in a coupled way and their variations are investigated two-dimensionally. The results are presented with multicolored plots in a 2-D domain. Furthermore, a parametric study is carried out for determining factors that enhance the heat and mass transfer inside the adsorbent bed. In this parametric study, the effects of several design and operational parameters on the dependent variables are investigated. In the experimental study, the finned tube is tested using natural zeolite-water and silica gel-water working pairs. Temperature, pressure and amount adsorbed variations inside the adsorbent bed at various operating conditions are investigated. After that, a second adsorbent bed with a larger size is constructed and tested. The effect of the particle diameter of the adsorbent is also investigated. The experimental and theoretical results are compared.

This work describes the development of Metal Organic Frameworks based adsorption system for producing ice, cooling, ice slurry and potable water using a CP0-27(Ni) and potable/sea water as working pair. Also a novel vacuum based direct freezing technique has been developed in the evaporator of the adsorption ice making system. In this new technique, cooling is generated in the evaporator to produce three outputs, namely, ice, ice slurry and cooling by lowering the freezing point of water using sea salt. The ice and ice slurry are produced in the evaporator during the adsorption-evaporation process, while the cooling process is produced by circulating the water/antifreeze to be cooled in the evaporator. Moreover, the usage of seawater as refrigerant offers producing fresh water as a fourth output in the condenser. A Single and a double bed CP0-27(Ni) MOF adsorption systems were developed to investigate the effect of this novel technique on the system performance in terms of producing of the four outputs. Compared to published literature, the proposed technology showed significantly higher Specific Daily Ice Production of 3 times those reported in literature with additional outputs of ice slurry, cooling and distilled water.

Cogeneration is a hot topic in the efforts to reduce dependence on fossil fuel usage and to reduce greenhouse gas emissions by replacing the primary energy source with a low-grade heat source. Cogeneration simultaneously produces power and cooling using a low-grade heat source (e.g. solar energy, geothermal energy or waste heat), which ideally provides a renewable carbon-free solution for implementation in domestic, industrial as well as isolated areas. This research thesis describes for the first time the development and construction of the Low Heat cogeneration chemisorption system, explores its potential and makes suggestions for its future development based on the experience gained during the experiments. The design uses two adsorption cycles operating out of phase and alternatively connected to a scroll expander in order to reach 3kW of cooling and 1kW of electricity. Each adsorption cycle consists of a reactor, a condenser and an evaporator. Each reactor contains a composite mixture of CaCl2 and activated carbon at a ratio of 4:1 by mass. The system was experimentally investigated for its cooling as well as for its cogeneration performance. Experimental investigations were performed for different heating and cooling temperatures, cycle times and the optimum overall ammonia for the system. The maximum refrigeration coefficient of the performance (COPref) of the machine was found to be 0.26 when the refrigeration power was 3.52kW. At the same time, the specific cooling power (SCP) per side was 201.14W/kg (402.28W/kg per cycle) and the cooling capacity 168.96kJ/kg (337.92kJ/kg per cycle). During the cogeneration experiments it was found that the expander affected the pressure and temperature; the refrigerant flow rate and the pressure across the expander were important for the system’s power production. The maximum power recorded was 486W which provides a power coefficient of performance (COPW) of 0.048. A model to describe the desorption power generation as well as the evaporation refrigeration process was developed using the ECLIPSE software. The cooling model was validated from the experimental results and later the power model was used for ii further investigation of the system power performance. The optimisation of the machine completes the study by using both experimental and simulation data.

Cette thèse s'inscrit dans le cadre du projet européen BIOCOR ITN. Les matériaux métalliques habituellement utilisés dans les circuits de refroidissement de centrales électriques peuvent être affectés par la biocorrosion. L'objectif de ce travail était d'étudier l'influence de l'adsorption de biomolécules sur le comportement électrochimique et la composition chimique de surface de l'alliage 70Cu-30Ni, l'acier inoxydable 304L et le titane en milieu marin. Les interactions entre l'albumine de sérum bovin (BSA), et la surface de ces matériaux ont été étudiées. Ensuite, l'effet des substances polymériques extracellulaires (EPS) (étroitement liées -TB- et faiblement liées -LB- à la surface cellulaire) sur les couches d'oxydes a été évalué. Des mesures électrochimiques (Ecorr vs temps d'immersion, courbes de polarisation et EIS) ont été combinées à des analyses de surface (XPS et ToF-SIMS). En comparaison de l'alliage 70Cu-30Ni en eau de mer artificielle (ASW) statique sans biomolécules, pour lequel une couche duplex épaisse est montrée, la présence de biomolécules conduit à une couche mixte d'oxydes d'épaisseur plus faible. Un modèle est proposé pour analyser les données d'impédance obtenues à Ecorr. Un ralentissement de la réaction anodique par les biomolécules a été montré avec un effet d'inhibition de la corrosion par les LB EPS, dans une moindre mesure par la BSA et aucun effet néfaste en présence de TB EPS. L'effet des TB EPS et de la BSA sur la passivation du Ti dans ASW et de l'acier inoxydable 304L dans une solution sans chlorure a été étudié. Pour les deux matériaux, les couches d'oxydes sont plus protectrices avec la BSA et moins protectrices avec les TB EPS
This thesis was carried out in the frame of the BIOCOR ITN European project. Metallic materials commonly used in cooling systems of power plants may be affected by biocorrosion. The objective of this work was to study the influence of biomolecules adsorption on the electrochemical behaviour and the surface chemical composition of 70Cu-30Ni alloy, 304L stainless steel and titanium in seawater environments. The interactions between a model protein, the bovine serum albumin (BSA), and the surface of these materials were investigated. After, the influence of tightly bound (TB) and loosely bound (LB) extracellular polymeric substances (EPS) on the oxide layers was evaluated. For that purpose, electrochemical measurements (Ecorr vs time, polarization curves and EIS) were combined to surface analysis (XPS and ToF-SIMS). Comparing to the 70Cu-30Ni alloy in static artificial seawater (ASW) without biomolecules, for which a thick duplex oxide layer is shown, the presence of BSA, TB EPS and LB EPS leads to a mixed oxide layer with a lower thickness. A model is proposed to analyse impedance data obtained at Ecorr. The results show a slow-down of the anodic reaction in the presence of biomolecules with a corrosion inhibition effect by LB EPS, to a lesser extent by BSA and no detrimental effect with TB EPS. On the other hand, the effect of TB EPS and BSA on the passivation behaviour of Ti in ASW and of 304L stainless steel in chloride-free solution was studied. From EIS data, resistivity profiles within oxide films can be plotted. For both materials, oxide layers are more protective with BSA and less protective with TB EPS

In this thesis, firstly, the equilibrium adsorption capacity of water on a natural zeolite at several zeolite temperatures and water vapor pressures has been experimentally determined for adsorption and desorption processes. Additionally, the modified Dubinin-Astakhov adsorption equilibrium model has been fitted to experimental data and separate correlations are obtained for adsorption and desorption processes as well as a single correlation to model both processes. Experimental results show that the maximum adsorption capacity of natural zeolite is nearly 0.12 kgw/kgad for zeolite temperatures and water vapor pressures in the range 40-150 C and 0.87-7.38 kPa. Secondly, a thermally driven adsorption cooling prototype using natural zeolite-water as working pair has been built and its performance investigated experimentally at various evaporator temperatures. Under the experimental conditions of 45 C adsorption, 150 C desorption, 30 C condenser and 22:5 C, 15 C and 10 C evaporator temperatures, the COP of the adsorption cooling unit is approximately 0.25 and the maximum average volumetric specific cooling power density (SCPv) and mass specific cooling power density (SCP) of the cooling unit are 5.2 kWm-3 and 7 Wkg-1, respectively. Thirdly, in order to investigate the dynamic heat and mass transfer behavior of the adsorbent bed of an adsorption cooling unit, a transient local thermal non equilibrium model that accounts for both internal and external mass transfer resistances has been developed using the local volume averaging method. Finally, the influence of several design parameters on the transient distributions of temperature, pressure and amount adsorbed inside the cylindrical adsorbent bed of an adsorption cooling unit using silica-gel/water have been numerically investigated for the one and two dimensional computational domains. Moreover, validity of the thermal equilibrium model assumption has been shown under the given boundary and design conditions. Generally, for the conditions investigated, the validity of the local thermal equilibrium and spatially isobaric bed assumptions have been confirmed. To improve the performance of the bed considered, eorts should be focused on reducing heat transfer resistances and intra-particle mass transfer resistances but not inter-particle mass transfer resistances.

The demand for cooling and air-conditioning of building is increasingly ever growing. This increase is mostly due to population and economic growth in developing countries, and also desire for a higher quality of thermal comfort. Increase in the use of conventional cooling systems results in larger carbon footprint and more greenhouse gases considering their higher electricity consumption, and it occasionally creates peaks in electricity demand from power supply grid. Solar energy as a renewable energy source is an alternative to drive the cooling machines since the cooling load is generally high when solar radiation is high. This thesis examines the performance of PV/T solar collector manufactured by Solarus company in a solar cooling system for an office building in Dubai, New Delhi, Los Angeles and Cape Town. The study is carried out by analyzing climate data and the requirements for thermal comfort in office buildings. Cooling systems strongly depend on weather conditions and local climate. Cooling load of buildings depend on many parameters such as ambient temperature, indoor comfort temperature, solar gain to the building and internal gains including; number of occupant and electrical devices. The simulations were carried out by selecting a suitable thermally driven chiller and modeling it with PV/T solar collector in Polysun software. Fractional primary energy saving and solar fraction were introduced as key figures of the project to evaluate the performance of cooling system. Several parametric studies and simulations were determined according to PV/T aperture area and hot water storage tank volume. The fractional primary energy saving analysis revealed that thermally driven chillers, particularly adsorption chillers are not suitable to be utilizing in small size of solar cooling systems in hot and tropic climates such as Dubai and New Delhi. Adsorption chillers require more thermal energy to meet the cooling load in hot and dry climates. The adsorption chillers operate in their full capacity and in higher coefficient of performance when they run in a moderate climate since they can properly reject the exhaust heat. The simulation results also indicated that PV/T solar collector have higher efficiency in warmer climates, however it requires a larger size of PV/T collectors to supply the thermally driven chillers for providing cooling in hot climates. Therefore using an electrical chiller as backup gives much better results in terms of primary energy savings, since PV/T electrical production also can be used for backup electrical chiller in a net metering mechanism.

2013/2014
Il continuo aumento della richiesta di energia elettrica e la conseguente crescita dei valori di anidride carbonica nell'atmosfera terrestre crea sempre più la necessità di attuare modifiche sostanziali non solo nei metodi di produzione dei settori energetico e industriale, ma anche nella vita di ogni abitante del pianeta. Questa tesi analizza la possibilità di utilizzare l'energia solare per la produzione di acqua fredda grazie alla contemporaneità tra la disponibilità di energia rinnovabile e la richiesta di raffrescamento durante il periodo estivo. Due diversi impianti sperimentali, dotati di collettori solari a tubi evacuati commerciali e chiller ad adsoprbimento di piccole dimensioni (20 kW), sono stati monitorati ed i primi risultati sperimentali sono presentati in questo studio. Per studiare soluzioni diverse e trovare un design ottimale, un modello di simulazione dinamica è stato creato e testato utilizzando il software commerciale TRNSYS 17.
XXVII Ciclo
1984

Solar Energy and Hydrogen (energy carrier) are possible replacement options for fossil fuel and its associated problems of availability and high prices which are devastating small, developing, oil-importing economies. But a major drawback to the full implementation of solar energy, in particular photovoltaic (PV), is the lowering of conversion efficiency of PV cells due to elevated cell temperatures while in operation. Also, hydrogen as an energy carrier must be produced in gaseous or liquid form before it can be used as fuel; but its‟ present major conversion process produces an abundance of carbon dioxide which is harming the environment through global warming. In search of resolutions to these issues, this research investigated the application of Thermal Management to Photovoltaic (PV) modules in an attempt to reverse the effects of elevated cell temperature. The investigation also examined the effects of coupling the thermally managed PV modules to a proton exchange membrane (PEM) Hydrogen Generator for the production of hydrogen gas in an environmentally friendly and renewable way. The research took place in Kingston, Jamaica. The thermal management involved the application of two cooling systems which are Gravity-Fed Cooling (GFC) and Solar-Powered Adsorption Cooling (SPAC) systems. In both systems Mathematical Models were developed as predictive tools for critical aspects of the systems. The models were validated by the results of experiments. The results of the investigation showed that both cooling systems stopped the cells temperatures from rising, reversed the negative effects on conversion efficiency, and increased the power output of the module by as much as 39%. The results also showed that the thermally managed PV module when coupled to the hydrogen generator impacted positively with an appreciably increase of up to 32% in hydrogen gas production. The results of this work can be applied to the equatorial belt but also to other regions with suitable solar irradiation. The research has contributed to the wider community by the development of practical, environmentally friendly, cost effective Thermal Management Systems that guarantee improvement in photovoltaic power output, by introducing a novel way to use renewable energy that has potential to be used by individual household and/or as cottage industry, and by the development of Mathematical Tools to aid in photovoltaic power systems designs.

This thesis presents work on a holistic approach for improving the overall design of solar cooling systems driven by solar thermal collectors. Newly developed methods for thermodynamic optimization of hydraulics and control were used to redesign an existing pilot plant. Measurements taken from the newly developed system show an 81% increase of the Solar Cooling Efficiency (SCEth) factor compared to the original pilot system. In addition to the improvements in system design, new efficiency factors for benchmarking solar cooling systems are presented. The Solar Supply Efficiency (SSEth) factor provides a means of quantifying the quality of solar thermal charging systems relative to the usable heat to drive the sorption process. The product of the SSEth with the already established COPth of the chiller, leads to the SCEth factor which, for the first time, provides a clear and concise benchmarking method for the overall design of solar cooling systems. Furthermore, the definition of a coefficient of performance, including irreversibilities from energy conversion (COPcon), enables a direct comparison of compression and sorption chiller technology. This new performance metric is applicable to all low-temperature heat-supply machines for direct comparison of different types or technologies. The achieved findings of this work led to an optimized generic design for solar cooling systems, which was successfully transferred to the market.

This thesis deals with the issue of sorption heat pumps. The theoretical part is devoted to a detailed description of the function of adsorption and absorption heat pumps. For a better understanding of the adsorption cycle is computed theoretical thermal cycle and the heating factor of zeolite adsorption heat pump are computed. The practical part is focused on the design absorption heat pump that works in conjunction with a natural gas boiler. The pump is designed for cooling flue gas condensing boiler and the possible use of thermal energy from other low-temperature source. The thesis contains a thermal calculations, engineering design and structural design of the heat pump.

碩士
國立中央大學
能源工程研究所
99
In this study, a silica gel-water adsorption system is designed and the system performance is measured. Two different adsorption beds and two different condensers are tested in the experiment. One adsorption bed is made by 3mm diameter copper tubes and the thickness of coated silica gel is 2mm. The silica gel weight of copper-tubes adsorption bed is 0.8 kg. Another adsorption bed is made by flat-tube heat exchanger whose volume and thickness of silica gel are the same as copper-tube adsorption bed. The weight of silica gel is 1.46 kg. The first condenser is a copper tube heat exchanger; another is a fin-tube heat exchanger. In experimental condition, there are two different temperatures of hot water, 75 and 80℃; two different temperatures of cooling water, 25 and 30℃. The temperature of cold water is 20℃. The cycle time are 6、12 and 20 minutes in copper-tube adsorption bed experiment. And in flat-tube adsorption bed experiment, the cycle time are 20、30 and 40 minutes. The result shows that the copper-tube adsorption bed doesn’t refrigerate the water of evaporator. It is because that the cooling power of copper-tube adsorption bed is not enough to cool the heat capability of total vacuumed chamber. And it also indicates that the higher temperature of hot water、the lower temperature of cooling water and the longer cycle time, the COP(coefficient of performance) of flat-tube adsorption bed is higher. And COP doesn’t increase by replacing the copper-tube condenser to fin-tube condenser.

abstract: The world is grappling with two serious issues related to energy and climate change. The use of solar energy is receiving much attention due to its potential as one of the solutions. Air conditioning is particularly attractive as a solar energy application because of the near coincidence of peak cooling loads with the available solar power. Recently, researchers have started serious discussions of using adsorptive processes for refrigeration and heat pumps. There is some success for the >100 ton adsorption systems but none exists in the <10 ton size range required for residential air conditioning. There are myriad reasons for the lack of small-scale systems such as low Coefficient of Performance (COP), high capital cost, scalability, and limited performance data. A numerical model to simulate an adsorption system was developed and its performance was compared with similar thermal-powered systems. Results showed that both the adsorption and absorption systems provide equal cooling capacity for a driving temperature range of 70-120 ºC, but the adsorption system is the only system to deliver cooling at temperatures below 65 ºC. Additionally, the absorption and desiccant systems provide better COP at low temperatures, but the COP's of the three systems converge at higher regeneration temperatures. To further investigate the viability of solar-powered heat pump systems, an hourly building load simulation was developed for a single-family house in the Phoenix metropolitan area. Thermal as well as economic performance comparison was conducted for adsorption, absorption, and solar photovoltaic (PV) powered vapor compression systems for a range of solar collector area and storage capacity. The results showed that for a small collector area, solar PV is more cost-effective whereas adsorption is better than absorption for larger collector area. The optimum solar collector area and the storage size were determined for each type of solar system. As part of this dissertation work, a small-scale proof-of-concept prototype of the adsorption system was assembled using some novel heat transfer enhancement strategies. Activated carbon and butane was chosen as the adsorbent-refrigerant pair. It was found that a COP of 0.12 and a cooling capacity of 89.6 W can be achieved.
Dissertation/Thesis
Ph.D. Mechanical Engineering 2011

abstract: Just for a moment! Imagine you live in Arizona without air-conditioning systems! Air-conditioning and refrigeration systems are one of the most crucial systems in anyone’s house and car these days. Energy resources are becoming more scarce and expensive. Most of the currently used refrigerants have brought an international concern about global warming. The search for more efficient cooling/refrigeration systems with environmental friendly refrigerants has become more and more important so as to reduce greenhouse gas emissions and ensure sustainable and affordable energy systems. The most widely used air-conditioning and refrigeration system, based on the vapor compression cycle, is driven by converting electricity into mechanical work which is a high quality type of energy. However, these systems can instead be possibly driven by heat, be made solid-state (i.e., thermoelectric cooling), consist entirely of a gaseous working fluid (i.e., reverse Brayton cycle), etc. This research explores several thermally driven cooling systems in order to understand and further overcome some of the major drawbacks associated with their performance as well as their high capital costs. In the second chapter, we investigate the opportunities for integrating single- and double-stage ammonia-water (NH3–H2O) absorption refrigeration systems with multi-effect distillation (MED) via cascade of rejected heat for large-scale plants. Similarly, in the third chapter, we explore a new polygeneration cooling-power cycle’s performance based on Rankine, reverse Brayton, ejector, and liquid desiccant cycles to produce power, cooling, and possibly fresh water for various configurations. Different configurations are considered from an energy perspective and are compared to stand-alone systems. In the last chapter, a new simple, inexpensive, scalable, environmentally friendly cooling system based on an adsorption heat pump system and evacuated tube solar collector is experimentally and theoretically studied. The system is destined as a small-scale system to harness solar radiation to provide a cooling effect directly in one system.
Dissertation/Thesis
Doctoral Dissertation Mechanical Engineering 2018

Electricity-driven air-conditioning is energy-intensive and puts a strain to many grids during hot periods in warm climates. Solar thermal cooling could be an alternative to conventional cooling, using a renewable energy source and supplying the most energy during peak demand periods with insignificant effect to the electric grid. Office buildings in warm climates have high cooling loads, naturally peaking during daytime because of occupancy and ambient temperature. Thus, office buildings have a seemingly advantageous relationship between the possible supply of solar thermal energy and cooling demand. With this background, solar cooling systems for two office buildings with the same dimensions are investigated, placed in a tropical- and a sub-tropical location. There are great differences in the design conditions for solar cooling systems in the tropics and the sub-tropics, between the chosen locations Manila and Abu Dhabi more specifically. Manila has a quite evenly distributed cooling load while Abu Dhabi has a strongly pronounced summer season with very high maximum cooling loads, while the winter temperatures are relatively low. The prior described conditions creates a big difference between loads throughout the year, making a thermal chiller less effective in this aspect. However Abu Dhabi is expected to have an overall smoother- and ultimately a more high performance solar cooling system due to lower humidity, which facilitates the important cooling of the chiller. Evacuated tube collectors were used at both sites, where the collectors in Manila needs to be larger relative to the chiller cooling capacity, in order to compensate for the irregularity of direct solar radiation. The electricity price in Abu Dhabi is too low for the solar cooling system to be economically feasible compared to a conventional system, where the net values over 20 years are 163 000 € and 127 000 €, respectively. Manila has on its hand a very high price for electricity, making the 20-year net values for both the solar cooling- and the conventional system approximately 170 000 €.

碩士
國立中興大學
機械工程學系所
101
This work experimentally investigated the specific cooling power (SCP) and coefficient of performance (COP) of a newly developed adsorption heat pump containing four fin-tube adsorbers. The adsorption pair were silica gel and water. In the experiment, two different operating conditions were considered. The result shows that, for the operation without a water circulation pump in the evaporator, the optimal cycle time is 32 minutes. The maximum SCP value is 70.6 W/kg-silica gel and corresponding COP value is 0.65；For the operation with a circulation pump, the optimal cycle time reduces to 20 minutes. The maximum SCP value is 75.2 W/kg-silica gel and corresponding COP value is 0.53. Installing the circulation pump results in a 6.52% increase in the maximum SCP value, but the COP value is decreased. The experiment result also reveals that the length of the copper tube in the evaporator maybe too short. Liquid water droplet might directly flow into the adsorber. In addition, the condensation performance of the condenser is not as expected. These three reasons might affect the performance of the adsorption heat pump.

The present research work caters to two important needs of rural India: i) desalination of subsoil/coastal brackish water and ii) basic refrigeration for short term preservations of agro-produce, medicines etc. Fortunately, such places are blessed with abundant solar insolation and/or low grade thermal energy (< 100°C) is available which may be tapped for this purpose instead of relying solely on grid electricity. Both the objectives of desalination and cooling are realized by evaporating brackish water at a low pressure (~1 kPa) and thermally compressing the water vapour to a higher pressure before condensing it. Adsorption route is chosen for compression where silica gel is the adsorbent and water to be desalinated as the refrigerant. The objective of this study is to develop a laboratory prototype of a two-stage adsorption cooling cum desalination system driven by low grade heat source. The entire system is air-cooled which is necessitated by non-availability of heat exchange grade cooling water. Initially various experimental and theoretical studies are carried out for characterizing silica gel + water pair which is fundamental to the system design. RD type silica gel is used in this study due to its high uptake capabilities. The uptakes for this adsorption pair at various pressure and temperature conditions are measured using a specially designed isothermal adsorber cell connected to an evaporator. Subsequently, a modelling study of adsorption kinetics is performed for a monolayer of silica gel in order to estimate the adsorption time scale. This time scale is used as an input for the scaling analysis of columnar packed silica gel bed. The scaling analysis showed that the thermal diffusion time scale limits the adsorption process. It also showed that for a given thermal length scale, the bed has a unique vapour flow length scale beyond which the adsorption phenomenon gets limited due to pressure drop. The scaling results are validated by simulation studies. A shell-and-tube heat exchanger is chosen for the adsorber which closely mimics the columnar silica gel packing studied in scaling analysis. The heat exchanger is designed for radial entry of vapour. A modelling study is performed on ANSYS® Fluent platform for optimising the tube pitch by minimising the overall thermal capacitance of the bed. The shell diameter is determined for this tube pitch based on the vapour flow length criterion established through scaling. To experimentally study the effect of pressure drop on bed performance, the radial entry of vapour is closed for 1 bed/stage (out of the 4 beds/stage) enforcing the vapour to flow along the longer axial dimension. The system is generously instrumented for precise measurements and control over the various experimental parameters. For the functioning of the adsorber system, various vapour valves and water (heat transfer fluid) valves need to be operated in a cyclical and synchronized manner. Individual components are fitted with pressure, temperature and water flow sensors. The entire operation and data acquisition for the adsorption system has been automated using National Instruments® (NI) PXIe controller executing an in-house developed code written on NI Labview® platform. To simulate solar/waste heat input, multiple electrical heaters are used in this study and a constant temperature bath is used to simulate the cooling load at the evaporator. Prior to conducting experiments a 4-bed lumped dynamic model is developed based on the design data of the system to simulate the two-stage system performance for various input conditions. The study helped to optimise the performance of a two-stage system. The study also compares the two-stage and single-stage system performance for various ambient temperatures (25–40°C). The study revealed that for pressure lifts higher than 5 kPa a two-stage system is preferable. A detailed experimental study is conducted on the developed prototype by operating it in various conditions namely 2, 3 and 4–bed modes for single and two-stage operations; with 1.0–1.7 kPa evaporator pressures, half cycle time varying between 1200–3000s and source temperature in the range of 75–85°C. The system is operated indoors during summer conditions wherein the ambient temperature is found to be 36±1°C which is significantly higher than the design point of 25°C. This resulted in lower than expected throughput; however, the system performance variation is qualitatively similar to as predicted by the lumped model. A comparison between the experimental and simulated bed temperature revealed that the thermal wave during the switching of hot/cold water plays a significant role causing a large deviation from the simulation results. A comparative study is carried out between the beds with radial vapour flow to that with axial flow and the results validate the scaling criterion. Experimental results also depict that two-stage operation is favourable when the pressure lift required is larger than 5 kPa. Such large pressure lift is encountered when air-cooling is used in a tropical country like India.

The need for clean and renewable fuel such as hydrogen is driven by a growing worldwide population and increasing air pollution from fossil fuels. One of the major barriers for the use of hydrogen in automotive industry is the storage of hydrogen. Physisorption is the most promising storage technique due to its high storage density, reversibility and rapid sorption kinetics besides being safe and volume-efficient. A major challenge for physisorption is the need to manage the heat of adsorption at cryogenic temperatures. In this thesis, a 6061 aluminum microchannel cooling plate is designed to remove the equivalent heat flux required by the adsorption of hydrogen within an adsorption bed. Therefore, the objective of this thesis is to determine whether laser welding and heat treating strategies can be developed for a 6061 aluminum microchannel cooling plate as part of a larger hydrogen storage thermal management system. Key manufacturing process requirements include controlling the hermeticity, strength and dimensional stability of the heat-treated weld joint. A hermetic microchannel cooling plate was successfully laser welded and heat treated using free convection in air to quench the solution heat treatment. The weld strength and warpage obtained were within acceptable limits. Experimental testing of the fabricated microchannel cooling plate showed acceptable percent error with an experimental heat removal rate within 13.4% of computational fluid dynamics (CFD) analyses and an average pressure drop error of 25%. Calculations show that the cooling plate developed could support a hydrogen storage thermal management system taking up 5.0% and 10.3% of the system displacement volume and mass, respectively.
Graduation date: 2013

碩士
國立臺北科技大學
冷凍與低溫科技研究所
90
A theoretical method is proposed to establish computer model to analysis adsorbent bed in adsorption cooling system. The influence of various design parameters on the performance of the adsorbent bed is discussed in particular. The theoretical analysis begins with the derivation of a set differential equations based on the porous media and thermal-fluid theory. The effects of heat source temperature, evaporator temperature, condenser temperature, adsorbent bed size, the diameter of copper tube, etc. are all considered in the derivation. The derived system of equations is then solved by using finite-volume method. In the present study, the effects of different design and operate parameters are investigated. Output variable such as adsorption/desorption amount,the ratio of adsorption/desorption was obtained. The result appear that using metallic fin can improve the ratio of adsorption/desorption sufficiently, i.e., at the first hour of simulation, it was possible to increase that the ratio of adsorption from 6.3﹪(no fin) to 12.4﹪(8mm fin pitch) and the ratio of desorption from 9.0﹪(no fin) to 16.3﹪(8mm fin pitch).

Over the last decades, demand in the field of cooling devices has been considerably increased to satisfy the requirements for human comfort. The increased demand for energy required to power the conventional compression refrigeration systems has led to both energy and environmental concerns. To overcome these concerns, the researchers have focused on the use of sorption cooling technologies driven by low-grade thermal energy sources such as solar, geothermal, and waste thermal energy. Current research of thermally driven sorption cooling technology is first reviewed. Absorption and adsorption chillers have been proven to be effective means to convert the thermal energy into useful cooling and have been wide applied in the waste heat recovery. However, these two systems cannot work efficiently when the heat source temperature drops to below 75 °C. Such temperature energy sources are abundant existing in solar, geothermal, and waste thermal energy. Development of sorption cooling system driven by low grade thermal temperature is essential to enhance the energy utilization efficiency and reduce global warming. The challenges to develop such sorption cooling system is then identified. It is found that the evaporating and condensing pressures limit the sorption capability for both absorption and adsorption cooling systems at low-grade thermal heat source temperatures. By analysing the operating characteristics of both absorption and adsorption cooling systems, a completely novel integrated adsorption-absorption (AD−AB) refrigeration system is proposed and studied. The innovation of the proposed system is that the generator of absorption cycle operates as the evaporator of adsorption cycle; hence, the generation and evaporating pressure is no longer determined by the cooling and chilled water temperatures as it is associated with the heat source temperature. This results in an effective operation at lowgrade thermal sources by adjusting the intermediate pressure in the system. A fully dynamic lumped-parameter mathematical model is then developed to investigate the operating characteristics of the proposed integrated AD-AB system. The model is first validated using experimental data for absorption and adsorption cooling systems, respectively. Then the model is applied to evaluate the operating performance of the integrated AD-AB system. The results show that the CC and COP of the proposed system are as high as 13.7 kW and 0.4, respectively at a thermal source temperature of 60 °C. The COP of the integrated system is significantly higher compared to the conventional adsorption system at heat source temperatures below 65 °C. The cooling capacity of the integrated system is increased by up to 100% as compared with a conventional adsorption system under the same operating conditions. It is also found that the COP of the proposed system does not change significantly at heat source temperatures between 50 and 85 °C. This indicates the integrated AD–AB system could work efficiently across a wide range of low-temperature heat sources. Furthermore, the results also reveal that the COP of the integrated system is largely affected by the cooling water inlet temperature if the heat source temperature was lower than 55 °C. In order to further evaluate the efficacy of the AD-AB system, optimization of effective parameters on the system’s performance in terms of maximizing the energy performance of the proposed system is also conducted. The key parameters such as intermediate pressure and solution concentration are optimized to achieve the best system performance. Furthermore, different configurations of the integrated AD-AB system and effect of the flow arrangement of hot and cold fluid are also studied. The results show that as the heat source temperature increases from 50 to 85 °C, the optimal intermediate pressure vary gently from 2.36 to 2.16 kPa while the optimal solution concentration increases significantly from 52.4 to 65%. An COP of 0.4 can be achieved for the optimized intermediate pressure and solution concentration at the heat source temperature as low as 50 °C. When compared the two different configurations, the results show that the cooling capacity and COP of the system configuration with AB as bottom cycle are about 5 to 10% higher than that of the system configuration with AD as bottom cycle. The investigation on the effect of flow arrangement of the heating and cooling fluids shows that the parallel flow arrangement for the cooling and heating can provide the best system performance. The maximum specific cooling power (SCP) is around 194 W kg\(^{-1}\) when the hot water flow arrangement between generator and desorber and cooling water flow arrangement between absorber, adsorber and condenser are both parallel. In contrast, the lowest SCP value is 157.9 W kg\(^{-1}\) obtained in the series scheme for both hot and cooling water flow arrangements. Australia has very rich solar radiation energy in the world. The application of solar energy in the proposed integrated cooling system is then examined for seven major Australian cities including Adelaide, Brisbane, Canberra, Darwin, Melbourne, Perth, and Sydney. Three different solar system configurations are considered; (i) cooling system is directly connected to the solar thermal collector, (ii) hot water storage tank is installed between the cooling unit and solar collector, and (iii) auxiliary heater with a set point of 60℃ is placed at the exit of storage tank. Results indicate that the average daily cooling capacity produced through the second system configuration with storage tank is greater than that produced with the first configuration. It is also found that the coefficient of performance is considerably more stable during the operating hours in the second solar configuration. Results reveal that all the examined cities particularly Darwin city have high potentiality for installing the proposed solar cooling system with high cooling production. In both system configurations, the greatest average cooling energy is achieved in summer months specially in January in all locations due to the high available solar radiation. The system performance was directly influenced by the collecting area in both configurations. It is observed that the average daily cooling capacity experiences an increase by expanding the collector field while the change in the average daily COP curve is too minimal, especially in the system with the storage tank. An energetic and economic optimization is then conducted in order to find the optimum system design in each Australian city. Considering the optimal design parameters including the storage tank volume and solar collector obtained for each city, it is revealed that Adelaide city with the internal rate of return of 25.2% is the most appropriate location while Melbourne with the internal rate of return of 19.4% is less suitable city for installing the proposed solar cooling system. Lastly, an economic comparison is also investigated, and the results indicates that considerably amount of energy of around 65% on average can be saved in the Australian cities by the solar integrated cooling system as compared to the conventional compression cooling systems.

碩士
國立臺北科技大學
冷凍與低溫科技研究所
91
This Paper presents a silica gel-water as adsorbent-adsorbate pair of adsorption cooling system . In the model , The numerical analysis using with the finite-volume method based on thermal-fluid theory .The performance of the system effect can be predicted in change four operate parameters of numerucal simulation and analyse of operate parameters in experimental investigation. The reasons are analyzed as follows: 1. In the adsorptive period , The efficiency of adsorption are improves with a decrease cooling fluid temperature and The efficiency of desorptive are improves with a increase heating fluid temperature at the desorptive period. 2. Using metallic fin can improve the system performance, The quantity of adsorptive can increase about 99% with using pitch 6mm of fin at adsorption period In the desorptive period, Using metallic fin can improve the quantity of desorption. and ratio of the desorption to saturation will be accelerate .When using a pitch 6mm of fin , The quantity of desorption increase about 63.4% and time of adsorptive to saturation only spend 30minuem. 3. The efficiency of adsorption will decrease with the decrease temperature of the evaporator and the efficiency of desorption will decrease with the increase temperature of the condenser .

abstract: In this study, two novel sorbents (zeolite 4A and sodium polyacrylate) are tested to investigate if utilizing ultrasonic acoustic energy could decrease the amount of time and overall energy required to regenerate these materials for use in cooling applications. To do this, an experiment was designed employing a cartridge heater and a piezoelectric element to be simultaneously providing heat and acoustic power to a custom designed desorption bed while measuring the bed mass and sorbent temperature at various locations. The results prove to be promising showing that early in the desorption process ultrasound may expedite the desorption process in zeolite by as much as five times and in sodium polyacrylate as much as three times in comparison to providing heat alone. The results also show that in zeolite desorption utilizing ultrasound may be particularly beneficial to initiate desorption whereas in sodium polyacrylate ultrasound appears most promising in the after a temperature threshold is met. These are exciting results and may prove to be significant in the future as more novel heat-based cooling cycles are developed.
Dissertation/Thesis
Masters Thesis Mechanical Engineering 2018

Hydrogen has been shown to be a promising replacement for fossil fuels for use in light duty vehicles because it is a clean, renewable and plentiful resource with a high gravimetric energy density. However, in order to obtain an acceptable volumetric energy density, densification of the hydrogen is required. Adsorptive materials have been shown in the literature to increase volumetric and gravimetric storage densities. A major issue with adsorptive storage is that the adsorption process generates heat and optimal storage conditions are at temperatures below 100 K at pressures up to 50 atm. There is a need to develop heat exchanging architecture that enables adsorbents to be a viable method for hydrogen storage by managing the thermal environment of the storage tank. Based on previous modeling efforts to determine an acceptable bed module height for removal of heat via microchannel cooling plates, a thermal management system has been designed and tested capable of removing the heat of adsorption within adsorbent-filled hydrogen storage tanks. The system uses liquid nitrogen cooling to maintain tank temperatures of below 80 K at 50 atm. System studies show that the microchannel architecture offers a high cooling capacity with about a 6% displacement volume. Simulations and experiments have been conducted to evaluate the design for the cooling capacity, pressure drop, and flow distribution between and across the cooling plates, stress due to the pressurized environment, and thermal stress. Cost models have been developed to demonstrate that the system can be manufactured for a reasonable cost at high production volumes. Experimental results show that the modular system offers an acceptable cooling capacity and pressure drop with good flow distribution while adequately managing thermal stresses during operation.
Graduation date: 2013

碩士
元智大學
機械工程研究所
88
The Research for Adsorptive Desiccant Dehumidifier Cooling System in Lithium Battery Dry Room Student：Pang-chin LiuAdvisor：Ay Su Institute of Mechanical Engineering, Yuan-Ze University ABSTRACT With the trend of light-weighted and small-packed on the portable electronics products, and the demand of prolonged energy at just one charge, as a component, lithium battery of light-small & high energy density are being requested to be crucial for modern life. Under the strict requisition for the qualified manufacturing of lithium battery, a circumstance of low humidity is definitely asked for. After studying several dehumidifier cooling systems, we adopt the honey-comb adsorptive rotary dehumidifier as the optimum way to meet thus demand. The honey-comb adsorptive rotary dehumidifier, with advantages such as maintaining a consistent low humidity at a period of time, dry air cooling down the after-cooler capacity etc., is recognized as the more energy-saving method when compared to a common-known refrigerate compressor dehumidifier. This device is just to discuss how honey-comb adsorptive rotary dehumidifier could reach the assumption of energy-saving and then is justified both by illustration & figure. Through the change of rotary speed, regeneration temperature etc., an optimum dew-point temperature could be acquired. Through a sound system design, we could change the relative temperature parameters and pressure factors to get an optimum function model. Furthermore, during a long period of observation and study, with evidence of a series of experiment procedures, figures and systematic drawings, a suitable dehumidifying device can come out for the special requirements for Lithium Battery Room. We also hope ideal dehumidifying devices can be designed for different areas of industries.