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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Development And Investigation of Two-Stage Silica Gel + Water Adsorption Cooling Cum Desalination System

Mitra, Sourav January 2016 (has links) (PDF)
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.
2

Numerical Modeling And Performance Analysis Of Solar-powered Ideal Adsorption Cooling Systems

Taylan, Onur 01 May 2010 (has links) (PDF)
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.
3

An Experimental Study On The Performance Of An Adsorption Cooling System And The Numerical Analysis Of Its Adsorbent Bed

Solmus, Ismail 01 December 2011 (has links) (PDF)
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.
4

Solar Cooling : -A study of two thermal systems

Åhlund, Anton January 2015 (has links)
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 €.
5

Enhanced Desorption in Novel Sorbent Materials Using Ultrasound

January 2018 (has links)
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
6

MODELLING AND OPTIMIZATION OF AN ADSORPTION COOLING SYSTEM FOR AUTOMOTIVE APPLICATIONS

Verde Trindade, María 01 September 2015 (has links)
[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
7

Investigation of renewable, coupled solar-hydrogen fuel generation with thermal management systems suitable for equatorial regions

Wilson, Earle Anthony January 2010 (has links)
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.
8

Kyla med värme : En jämförelsestudie med huvudfokus på fjärrvärmedriven kyla

Eliasson, Dennis January 2017 (has links)
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 &amp; 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.
9

Design And Experimental Testing Of An Adsorbent Bed For A Thermal Wave Adsorption Cooling Cycle

Caglar, Ahmet 01 September 2012 (has links) (PDF)
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.
10

Thermodynamic And Economic Analysis Of A Solar Thermal Powered Adsorption Cooling System

Demirocak, Emre Dervis 01 October 2008 (has links) (PDF)
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 &amp / 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.

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