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  • 201.
    Arias, J
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Lundqvist, P
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Advanced Supermarket refrigeration2003Rapport (Refereegranskat)
  • 202.
    Arias, J
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Lundqvist, P
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Comparison of Recent refrigeration systems in supermarkets2001Konferensbidrag (Refereegranskat)
  • 203.
    Arias, J
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Lundqvist, P
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Den energieffektiva butiken i teori och praktik – slutrapport2001Rapport (Refereegranskat)
  • 204.
    Arias, J
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Lundqvist, P
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Heat recovery in recent refrigeration systems in supermarkets2002Konferensbidrag (Refereegranskat)
  • 205.
    Arias, Jaime
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Energy Usage in Supermarkets - Modelling and Field Measurements2005Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    This thesis investigates a special type of energy system, namely energy use in supermarkets through modelling, simulations and field studies. A user-friendly computer program, CyberMart, which calculates the total energy performance of a supermarket, is presented. The modelling method described in this thesis has four phases: the first phase is the de-velopment of a conceptual model that includes its objectives, the envi-ronment and the components of the system, and their interconnections. The second phase is a quantitative model in which the ideas from the conceptual model are transformed into mathematical and physical rela-tionships. The third phase is an evaluation of the model with a sensitivity analysis of its predictions and comparisons between the computer model and results from field measurements. The fourth phase is the model ap-plication in which the computer model answers questions identified in the beginning of the modelling process as well as other questions arising throughout the work.

    Field measurements in seven different supermarkets in Sweden were car-ried out to: (i) investigate the most important parameters that influence energy performance in supermarkets, (ii) analyse the operation of new system designs with indirect system implementation in Sweden during recent years, and (iii) validate the computer model.

    A thorough sensitivity analysis shows a total sensitivity of 5.6 %, which is a satisfactory result given a 10% change in the majority of input parame-ters and assumptions, with the exception of outdoor temperatures and solar radiation that were calculated as extreme values in METEO-NORM. Comparisons between measurements and simulations in five supermarkets also show a good agreement. Measurements and simula-tion results for a whole year were not possible due to lack of data.

    CyberMart opens up perspectives for designers and engineers in the field by providing innovative opportunities for assessment and testing of new energy efficient measures but also for evaluation of different already-installed system designs and components. The implementation of new energy-saving technologies in supermarkets requires an extensive inte-grated analysis of the energy performances of the refrigeration system, HVAC system, lighting, equipment, and the total energy usage. This analysis should be done over a long period, to evaluate and compare the real energy performance with the theoretical values calculated by Cyber-Mart.

  • 206.
    Arias, Jaime
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Claesson, Joachim
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik. KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Uthålliga byggnadssystem.
    Effektivare butikskyla: Värme ur kylanläggningar samt system med flytande kondensering, Aktiviteter 20062007Rapport (Övrigt vetenskapligt)
  • 207.
    Arias, Jaime
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Lundqvist, Per
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Choisir entre récupération de chaleur ou pression de condesation flottante en froid commercial2006Ingår i: Revue J. du Froid, nr 1066, s. 47-54Artikel i tidskrift (Refereegranskat)
  • 208.
    Arias, Jaime
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Lundqvist, Per
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Heat Recovery and Floating Condensing in Recent Refrigeration Systems in Supermarkets2005Konferensbidrag (Refereegranskat)
  • 209.
    Arias, Jaime
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Lundqvist, Per
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Modelling Supermarket Energy Usage2005Konferensbidrag (Refereegranskat)
  • 210.
    Arias, Jaime
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Lundqvist, PerKTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.Sawalha, SamerKTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Annex 31: advanced modelling and tools for analysis of energy use in supermarket systems2010Proceedings (redaktörskap) (Refereegranskat)
  • 211.
    Arias, Jaime M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Lundqvist, Per G.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Heat recovery and floating condensing in supermarkets2006Ingår i: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 38, nr 2, s. 73-81Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Supermarkets are great energy users in many countries. The potential for increased energy efficiency is large. One option is to utilize heat recovery (or heat reclaim) from condensers to heat the premises. Obviously this option is only interesting in relatively cold areas such as northern Europe, Canada, etc. An alternative to heat recovery is floating condensing pressure, which improves the coefficient of performance and decreases the energy consumption of the refrigeration system at lower outdoor temperature. Both heat recovery and floating condensing pressure can be utilized interchangeably depending on the heat requirements of the premises. A computer model that calculates the energy consumption in a supermarket with the possibility to simulate different system solutions for the refrigeration system has been developed at the Royal Institute of Technology, Department of Energy Technology. The software CyberMart is used in the present study to compare the potential of heat recovery and floating condensing in Swedish supermarkets. Measurements of different parameters such as temperatures, relative humidity and compressor power have been carried out in different supermarkets with heat recovery to validate the theoretical calculations. The present study shows that heating requirements can be covered completely by heat reclaim from the condenser. However, practical experiences show that installations are less efficient due to poor system solutions and/or control strategies. According to the results from CyberMart, the highest potential of energy saving is obtained from using a systems solution with both heat recovery and floating condensing.

  • 212.
    Arias, Jaime M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Lundqvist, Per G.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Modelling and experimental validation of advanced refrigeration systems in supermarkets2005Ingår i: Proceedings of the Institution of mechanical engineers. Part E, journal of process mechanical engineering, ISSN 0954-4089, E-ISSN 2041-3009, Vol. 219, nr E2, s. 149-156Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effective use of energy and the replacement of CFC and HCFC refrigerants are two factors that have influenced the design and operation of refrigeration systems in supermarkets during recent years. The potential for increasing energy efficiency in refrigeration systems, indoor climate and refrigerated cabinets is large. Since the energy systems of a supermarket are relatively complex, improvements in one subsystem affect other systems, thus making analysis of potential improvements non-additive. A computer model, CyberMart, that predicts building heating and cooling loads, HVAC (heating, ventilation, and air conditioning), and refrigeration system performances of a supermarket, has been developed. The focus of the model is on energy use, environmental impact (TEWI), and life cycle cost (LCC) of the refngeration system. The refrigeration system solutions included in the model are: direct system, completely indirect system, partially indirect system, cascade system, parallel system with mechanical sub-cooling (where the refrigerant in the low-temperature system is sub-cooled with the brine of the intermediate temperature level), and district cooling (that cools the condenser of the refrigeration machines). Measurements of different parameters such as outdoor and indoor temperatures, relative humidity, and compressor power have been carried out in several stores to validate the model. A theoretical description of the model and results from the model and measurements are presented in this paper.

  • 213.
    Arias, Luis
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Uthålliga byggnadssystem.
    Achieving energy efficiency in a hotel-office building under tropical Latin American climatic conditions2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 214.
    Arnaudo, Monica
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Topel, Monika
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Puerto, P.
    CREM Centre de Recherches Énergétiques et Municipales, Martigny, Switzerland. HES-SO Haute École Spécialisée de Suisse Occidentale, Sion, Switzerland.
    Widl, E.
    AIT Austrian Institute of Technology, Center for Energy, Vienna, Austria.
    Laumert, Björn
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Heat demand peak shaving in urban integrated energy systems by demand side management - A techno-economic and environmental approach2019Ingår i: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 186, artikel-id 115887Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The integration of variable renewable resources and decentralized energy technologies generates the need for a larger flexibility of the energy demand. In order to fully deploy a demand side management approach, synergies between interconnected energy systems have to be systematically implemented. By taking this standpoint, this study proposes a new approach to explore the potential of multi-energy integrated energy systems. This approach is constituted by two main steps, which are (1) the performance simulation of selected energy infrastructures and (2) the estimation of related techno-economic performance indicators. Step (1) expands the work presented in previous literature, by including a novel co-simulation feature. In step (2), the levelized cost of energy and location-dependent emission factors are used as key performance indicators. In this paper, the presented approach is demonstrated by implementing two demand side management options for heat peak demand shaving. A Swedish residential neighborhood is considered as a case study. The first option explores the potential of storing heat in the thermal mass of residential buildings. The proposed strategies lead to a decrease of up to 70% of primary energy consumption, depending on the indoor comfort requirements. The second option estimates the techno-economic feasibility of a new set of scenarios based on the integration of geothermal distributed heat pumps within a district heating network. The district heating scenario is found to be the most techno-economical convenient. Nevertheless, a moderate penetration of distributed heat pumps (around 20%) is shown to have a good trade-off with the reduction of CO2 emissions.

  • 215.
    Arnaudo, Monica
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Zaalouk, O. A.
    Topel, Monika
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Laumert, Björn
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Techno-economic Analysis of Integrated Energy Systems at Urban District Level - A Swedish Case Study2018Ingår i: Energy Procedia, Elsevier, 2018, s. 286-296Konferensbidrag (Refereegranskat)
    Abstract [en]

    Within the Nordic countries, distributed heat and power supply technologies, like domestic scale heat pumps and photovoltaics, are challenging the current centralized district energy infrastructure. An increasing number of customers decide to disconnect from the traditional heating network by comparing the bill to the potential economic savings which can be generated by a residential heat pump system. However, this approach can be considered valid only on a short-term perspective. This paper presents a new approach to compare the techno-economic performance of alternative technologies, based on their lifetime average cost of generation. The proposed analysis is able to determine the optimal energy infrastructure at urban district level. Within this solution, operators, city planners and users will have a solid reference for their decision making process on resources investment. From a first step analysis of a few Swedish case studies, it was found that a district heating based system is more techno-economically efficient compared to the distributed alternative. By comparing the district heating production cost to its final price, a significant profit margin for the utility was qualitatively highlighted. Thus, from a customer perspective, on the medium run, the district heating tariff can be adapted and the estimated savings from switching to a residential heat pump system can be nullified.

  • 216.
    Arnesson, Erik
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Analysis of sustainable building materials, their possibilities and challenges2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Sverige har som första välfärdsland skrivit under avtalet om att ha netto-noll utsläpp av växthusgaser 2045. Byggsektorn bidrar till en betydande del av Sveriges nuvarande utsläpp. En färdplan utformad och godkänd av flera byggbolag, däribland Veidekke, innehåller flera delmål och det slutgiltiga målet av en byggsektor med netto-noll utsläpp 2045. Samtidigt är behovet av nya bostäder stort. Valet av byggmaterial påverkar utsläppet från en byggnad under hela livstiden vilket gör det till en nyckelparameter vid planeringen av en nybyggnation. 80 % av utsläppen under konstruktionsfasen har sitt ursprung från tillverkningen av byggnadsmaterialen. Samtidigt är forsknings- och utvecklingsintensiteten i byggsektorn låg, marginalerna små och konkurrensen hög.

    Denna rapport hade avsikt att undersöka mer hållbara byggmaterial för de bärande delarna av flervåningshus, hur de mäter sig med konventionella material samt utmaningar som möter dem. Undersökta material jämfördes med en referensvägg från ett av Veidekkes byggen med hjälp av nyckeltal. Denna referensvägg beräknades att ha ett CO2-utsläpp på 107 kg CO2e/m2vägg. Med hjälp av metodik från industriell dynamik kunde sen materialen utvärderas baserat på deras egenskaper, flaskhalsar i byggsektorn undersökas samt viktiga parter för att implementera nya material analyseras. Material som undersöktes var korslimmat trä samt olika typer av miljövänlig betong. Möjligheterna till hybrider av betong och trä inspekterades också. Korslimmat trä har i nuläget en liten marknadsandel men är ett lovande material med flera positiva egenskaper. Forskning kring mer miljövänlig betong förde analysen till att undersöka återvunnen betong, alkaliaktiverad betong och en Eko-betong med lägre andel cement till fördel av kalksten. Efter detta undersöktes sociala och ekonomiska barriärer för att integrera mer hållbara material i byggsektorn. Då byggsektorn till stor del är projektbaserad, med begränsad tid och budget, försvåras integrationen av nya material. Processerna i projekten tenderar också att bli repetitiva med låg nivå av återkoppling. Som sektorn är utformad idag är den till stor del beroende av betong. Däremot ökar ständigt den sociala acceptansen kring korslimmat trä och analysen visade vikt vid att transformera hållbarhet till ett strategiskt affärsmål för att behaga kunder med ökande miljömål. Intervjuer genomförda på Veidekke visade det ökande intresset av hybrider av trä och betong, men också svårigheterna i att driva utveckling framåt i byggsektorn. 

    Analys av materialen och deras nyckeltal resulterade i en vidare analys av korslimmat trä samt Eko-betongen. Korslimmat trä gav den största reduktionen av växthusgaser. En yttervägg producerad i korslimmat trä beräknades till att ha ett negativt utsläpp på -66.2 CO2e/m2vägg. Förutom detta påvisades flera positiva egenskaper för materialet gällande konstruktionstid, livstid och tekniska egenskaper. Reduktionen av CO2-utsläpp från Eko-betongen var också god, drygt 50 % mindre jämfört med den betong som användes i referensväggen. Eftersom Eko-betongen är just en betongvariant bör den möta färre barriärer än korslimmat trä då hela värdekedjan i byggsektorn är bekant med betong, dess egenskaper och möjligheter. Vidare analys med hjälp av industriell dynamik påvisade behovet av incitament för att utveckla kunskap kring vad hållbart byggande är samt behovet av att utveckla nya nätverk mellan tillverkare och beställare för att hitta och använda nya material i processen. Timmer- och betongindustrier har det största ansvaret att utveckla nya och mer hållbara material. Samtidigt läggs stor vikt på byggsektorn att välja mer hållbara material. Att förespråka en byggsektor med en mångfald av lösningar kommer att utveckla en mer robust och anpassningsbar miljö med färre flaskhalsar än idag.

    Nyckelparterna för integrationen är affärsutvecklare, inköpare, trä- och betongindustrierna samt kunderna. Affärsutvecklare måste bedriva projekt med klara och höga miljömål för att öka chansen att lyckas. Inköpare behöver incitament för att kartlägga hållbara material och få utrymme att undersöka nya underleverantörer. Resultatet av analysen visar att ingen enskild innovation kommer kunna lösa problematiken och uppnå en byggsektor med netto-noll utsläpp 2045. Nyckelmöjligheterna för korslimmat trä är att utveckla en standard och modularisering gällande produkten. Förbättra brandskyddet för korslimmat trä är också av hög prioritet och där kan utvecklingen av brandskyddande gipsskivor och isolering vara en lösning. Vidare forskning på modifierad blandning av betong och egenskaper för puzzolana material är också en viktig del framåt. Byggnation av hybrider i trä och betong har också visat stor potential både i litteraturstudien, analysen och från intervjuer på Veidekke. Detta ses som en god möjlighet för att förenkla integrationen av trä till byggsektorn.

  • 217.
    Arnesson, Erik
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Hagdahl, Josefine
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Mötesplatsen: Där människor och energi möts2016Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Energianvändningen i Sveriges idrottsanläggningar är mycket hög jämfört med andra

    lokaler så som skolor och kontor, sett till energianvändning per kvadratmeter. I

    synnerhet ses simhallar och ishallar som de mest energikrävande

    idrottsanläggningarna och detta har ofta sin grund i föråldrad teknik men också i

    anläggningarnas höga besökssiffror. Ett kylsystem i en ishall för bort värme från

    ispisten, värme som idag ofta fläktas rakt ut i naturen. Denna värme skulle istället

    kunna användas i simhallar och helt eller delvis täcka simhallens värmebehov. Ett

    modernt kombinerat kyl- och värmesystem med CO2 som köldmedium skulle då

    kunna sammanföra en ishall och en simhall. Detta ger möjligheten till att skapa en

    mötesplats där flera idrottstyper och människor kan mötas.

    Målet med projektet var bland annat att se om värmebehovet i en kombianläggning,

    med en is- och simhall, skulle kunna täckas med överskottsvärme från ishallen.

    Förutom detta undersöktes också om ett energisystem med CO2 som kylmedium

    skulle kunna appliceras, hur värmebehoven varierar under året och om ett

    geoenergilager skulle kunna lagra överskottsvärme i systemet. En litteraturstudie med

    djupare fakta om anläggningarna, fallstudier på nuvarande is- och simhallar, deras

    energianvändning och hur de varierar under året genomfördes.

    För att uppnå projektets mål undersöktes hur värmebehovet för is- och simhallen

    varierade samt hur mycket överskottsvärme som fanns tillgänglig från ishallen för alla

    årets månader. Dessa beräkningar visade att ishallen producerade överskottsvärme

    som kunde överföras till simhallen och täcka delar av dess värmebehov. Under

    ishallens lågsäsong, juli till september månad, producerades det som mest

    överskottsvärme samtidigt som is- och simhallens värmebehov var lågt. Detta bidrog

    till ett stort överskott som kan föras vidare till geoenergilagret. I detta lager kan

    värmen lagras tills dess att kombianläggningen har ett underskott och behöver den.

    Beräkningarna ledde till ett resultat som visade att överskottsvärmen från ishallen inte

    kommer täcka hela värmebehovet för kombianläggningen men bidra till att en

    avsevärt mycket mindre mängd extern energi behöver användas för att värma upp

    anläggningen. Totalt sett saknades det 103 MWh för att täcka behovet vilket innebar

    att ishallens överskottsvärme till 92% kunde täcka kombianläggningens värmebehov.

  • 218.
    Arokia Lourdu Marshall, Arokia
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Simplification of 3d cooled turbine blade models for efficient dynamic analyses2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In gas turbines, the temperature behind the combustors is the highest, meaning that the blades in the first stage of the turbine require cooling air. This makes the structural blade model very detailed due to the presence of the cooling pattern. For aeromechanical design, one of the first steps is to perform a modal frequency check by using 3d Finite Element models and the Campbell diagram to establish if the design is acceptable with respect to resonance margins. If the 3d detailed geometry (including all the cooling details) is used the model becomes extremely large. In order to perform various loops between structural dynamics and aerodynamics in an early stage, the dynamic model of cooled blades should be simplified. The simplified model should be accurate enough in terms of predicting correct frequencies but much lighter in size.

     

    The objective of this thesis is to perform parametric studies of different 3d simplified cooled turbine blade models. Various models with different geometrical features are created from the history of the CAD software (NX). Different FE meshes are produced in the Hypermesh software and the modal analyses are solved in Abaqus. The results are compared with the fully detailed model. The influence of the cooling features for each test case is summarized and this will be useful for creating reduced order models. Explanation and guidelines with respect to the mesh generation and loading conditions in Hypermesh software are also included in the appendix section. 

     

    For quick frequency checks during the intial stages of the design, the solid blade model can be used which has the modal frequencies within 10 percent range from the fully detailed model. The cooling core features that are important with respect to dynamics are cooling matrix, the ribs and the trailing edge cutback which contribute to the stiffness of the blade.

  • 219.
    Artola, Bixente
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Scoop optimization: A preliminary study2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Scoops are important parts in an aircraft engine design, as they provide airflowto different equipment and subsystems. The optimization of such a component isessential in order to find a design that can perform properly within a range of flightconditions, with a minimum impair of main flow aerodynamic performances. Scoopdesign methods are generally based on previous experimental results and are usuallyconstrained by the limited space available. The studied configuration concerns theflush scoop located inside the secondary flow of turbofans which provides flow fora turbine cooling equipment. Depending on flight conditions and engine workingpoint, this scoop will experience various flow regimes, from low mass flow rates tochoke flows. Therefore, the study of several scooped mass flow rates is mandatoryto extract the scoop behaviour. The thesis concerns the preliminary step beforea 3D CFD optimization : a study of influence is run on the baseline geometry inorder to investigate the robustness of the solution computed using different methodsand to determine the parameters to be optimized. Firstly, the full post-processingmethodology is defined to properly evaluate the performance of a design (scoopefficiency, induced pressure losses). A second step consists in analysing the abilityof CFD solvers to capture the different flow behaviour. This point is addressed bycomparing solvers (Fluent, elsA, PowerFLOW), meshes (structured, unstructured)and turbulence models. The third step deals with the optimization strategy definitionto improve the scoop design and thus the engine fuel consumption.

  • 220. Arturo Manrique, Carrera
    et al.
    Jayasuriya, Jeevan
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Fransson, Torsten
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Catalytic Partial Oxidation of Natural Gas in Gas Turbine Applications2013Ingår i: Proceedings of ASME Turbo Expo 2013, 2013Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The demands of emissions, combustion efficiency over a wider operational range, and fuel flexibility for industrial gas turbine applications are expected to increase in the coming years. Currently, it is common the use of a stabilizing piloting diffusion flame during part load operation, this flame is accountable for an important part of the thermal NOx emissions on partial load, and in some cases also at full load operation. On the other hand Catalytic Partial Oxidation (CPO) of natural gas is a technique used in petrochemical industry for the Fischer-Tropsch process and for H2 production, and is based in the production of Syn-Gas rich in H2 and CO.

    The present work explores the possibility to use the CPO of natural gas in industrial gas turbine applications, it is based in experiments performed between 5 and 13 bar using an arrangement of Rh based catalyst and CH4. The experiments were done at the Catalytic Combustion High Pressure Test Facility, at the Royal Institute of Technology (KTH) in Sweden. The gas produced leaves the CPO reactor between 700 and 850 °C and it is rich in H2 and CO. It was found that the most important parameter after reaching the light off temperature in the CPO reactor is the equivalence ratio Φ, which evidences the kinetically controlled regime in the Rh catalyst that depends on O2 availability. The H2/CO ratio is close to the theoretical value of 2 and the selectivity towards H2 and CO are 90% and 95% respectively while the CH4 conversion reached approximately 55%.

    Pressure on the other hand had a small negative influence in the tested pressure range and it is more relevant at richer fuel conditions (high equivalence ratios). The CPO process had shown that it is relatively easy to control the operation temperature of the catalyst. This temperature is kept below the maximum allowed by reducing the O2 availability.

    The high temperature Syn-Gas gas produced through CPO process could be burnt in the downstream of the catalysts steadily at flame temperatures below the thermal-NOx threshold. The CPO reactor could provide the flame stabilization function at a wide range of operational conditions, and replace the diffusion piloting flame. This approach could cope with NOx and CO emissions in a wider operational range and offers the possibility of using different fuels as the reaction controlling factor is O2 availability. Furthermore, an initial design of a possible combustion strategy downstream of the CPO reactor is also presented.

  • 221. Arturo Manrique, Carrera
    et al.
    Jayasuriya, Jeevan
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Fransson, Torsten
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Staged Lean Catalytic Combustion of Gasified Biomass for Gas Turbine Applications: an Experimental Approach to Investigate Performance of Catalysts2013Ingår i: Proceedings of ASME Turbo Expo 2013, 2013Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Emission demands for gas turbine utilization will become more stringent in the coming years. Currently different techniques are used to reach low levels of NOx emissions. One possible solution is the Staged Lean Catalytic Combustion. In this concept a catalysts arrangement is used to generate high temperature combustion gases. The high temperature gases could be used to feed a second combustion stage in which more fuel is injected.

    In this work a series of experiments were performed at the Catalytic Combustion High Pressure Test Facility at the Royal Institute of Technology (KTH) in Sweden. The fuel used was a simulated gasified biomass and the catalytic combustor consisted of an arrangement of different catalysts, e.g. bimetallic, hexaaluminates, and perovskites catalysts. These were used as, ignition catalyst, medium temperature catalyst and high temperature catalyst respectively.

    The tests were performed between 5 and 13.5 bar, and the overall conversion varied between 60% and 70% and the temperature of flue gases could reach 750°C and contains high level of oxygen. The determining factor to control the exit gas temperature was the richness of the mixture (λ value). On the other hand, the increased pressure had a moderate negative effect in the overall fuel conversion. This effect is stronger at leaner mixtures compared to richer ones. Moreover, λ value and also pressure affected the temperature distribution along the reactor.

    The utilization of a lean catalytic combustion approach makes possible the use of a post catalytic combustion. In this region additional fuel is injected to fully burn the exiting gases and increase the exit temperature to the desired levels. This staged lean catalytic combustion approach could resemble moderate levels exhaust gas recirculation techniques and/or high air temperature combustion and it is also briefly examined in the present work.

  • 222.
    Aruna Rathnakumara, Piladuwa Parana Hewage Janaka
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Dendro Power for Industrial Print-ing Press at Wijeya Newspapers Ltd. Sri Lanka2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Wijeya Newspapers Limited (WNL) är en av de ledande tidnings- och tidskriftsförlagen på Sri Lanka. Företaget har sin huvudfabrik (tryckeri) i Hokandara, 15 km från Colombo City. Totalt effektbehov för fabriken är 3000 kVA (2,4 MW) och bolagets årliga energibehov är 3,8 GWh, som för närvarande tillhandahålls av Ceylon Electricity Board (CEB). Som en strategi av den högre ledningen genomför företaget projekt rörande förnybar elproduktion, såsom bioenergi, sol- och vindenergi utöver sin befintliga energitillförsel och energianvändning i fabriken. För att uppfylla WNL:s vision om 2 MW alternativ grön och ren energiproduktion skall en biomassabaserad anläggning installeras som det första pilotenergiprojektet i företaget. Det föreslagna området för detta kraftverk kommer att vara på det egna kokosplantaget, och kommer att förse den nordvästra provinsen med elektricitet inom en radie av 15 – 20 km. Målet för WNL är att utveckla ekonomiskt bärkraftiga energianläggningar som använder lättillgängliga förnybara biomassbränslen till en acceptabel kostnad per kilowattimme, att använda grön och ren energi i sin tryckeriverksamhet och att ge ny intäktsgenerering för sina affärsportföljer. Biomassa-kraftprojektet (Dendro) kommer att generera ett grönt energiförsörjningssystem till sin tryckeriverksamhet och samtidigt skapa extra intäkter. Förutom att bidra till att uppfylla företagets mål kommer projektet att bidra till att minska beroendet av importerade icke-förnybara energikällor i landet. Mot denna bakgrund utförs denna forskning för att bedöma den nuvarande situationen för Dendros kraftproduktion och dess tillämpningar i Sri Lanka och att utvärdera möjligheten att utnyttja Dendros makt för att möta effektbehovet från den grafiska industrin. Denna studie drar slutsatsen att Dendros kraftgenerering för verksamheten vid WNL är ekonomiskt och tekniskt genomförbart och att den optimala anläggningskapaciteten för biobränslebaserade kraftverk skulle vara 2-5 MW. Det har också visats att det finns god social acceptans för biomassabaserad elproduktion i det lokala samhället. Som en rekommendation föreslår studien att regeringen vidtar åtgärder för att integrera förnybar energi i den nationellaelproduktionsplanen.

  • 223.
    Arzpeima, Minoo
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    CFD Investigation of Flow Structures in Rotor-Stator Disc Cavity Systems2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 224.
    Asim, Muhammad
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Experimental Analysis of Integrated System of Membrane Distillation for pure water with solar domestic hot water2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In GCC countries, especially in UAE desalination of sea water is considered to be one of the most effective and strategic alternative for satisfying the current and future demand of water for domestic purposes. The depletion of ground water aquifers, rapid industrial development and increase of urban population in UAE lead to tremendous increase in fresh water demand during past decade. Although, desalinated fresh water is supplied to the consumers by local municipalities, people in the region rely mostly on bottled water for drinking purpose obtained through post desalination re-processing. Thousands of suppliers in UAE deliver bottled water to homes or offices thus leading to environmental unsustainability in the whole conversion chain from desalinated water to bottling, packaging and delivery. In fact, UAE is one of the leading countries in per capita bottle water consumption. Therefore, a need has been observed to provide safe drinking water for households in a sustainable way.In order to produce drinking water at homes, a concept of integrating Membrane Distillation (MD) based water purification with Solar Domestic Hot Water (SDHW) systems has been proposed and its feasibility has been evaluated in this research study. Present application is for a single family house/villa in UAE region that requires 20 l/day of drinkable water and 250 l/day of hot water for domestic purpose. An experimental pilot system has been installed at CSEM-uae for evaluating different operational parameters of such integrated system and also to determine overall thermal performance of the system. The study provides detailed design of experimental unit, procurement, installation and commissioning of the SDHW-MD integrated system along with estimated annual profiles of pure water and overall energy consumption.Experiments performed for one month during summer and distillate fluxes of around 4.5 – 12 l/m2/hour has been obtained with optimum MD hot and cold side flow rates of 6 and 3 l/min respectively and at hot side temperatures ranging from 50 - 70oC with cold side average temperature of 35oC. With recovery of cold side heat of MD unit, 25% of daily demand of DHW could be reduced and hence the estimated annual combined energy demand of 8220 kWh could be sufficiently fulfilled with either 8.5 m2 aperture area of Flat plate solar thermal collectors or with 7.5 m2 of Evacuated tubular collectors.

  • 225. Asim, Muhammad
    et al.
    Imran, Muhammad
    Leung, Michael K. H.
    Kumar, N. T. Uday
    Martin, Andrew R.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Kashif, Faiza
    Experimental analysis of solar thermal integrated MD system for cogeneration of drinking water and hot water for single family villa in Dubai using flat plate and evacuated tube solar collectors2017Ingår i: Desalination and Water Treatment, ISSN 1944-3994, E-ISSN 1944-3986, Vol. 92, s. 46-59Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents the experimental analysis performed on solar thermal integrated membrane distillation (MD) system using flat plate and evacuated tube collectors. The system will be utilized for cogeneration of drinking water and domestic hot water for single family in Dubai comprising of four to five members. Experiments have been performed in Ras Al Khaimah Research and Innovation Centre (RAKRIC) facility. The experimental setup has been installed to achieve the required production of 15-25 L/d of drinking water and 250 L/d of hot water for domestic purposes. Experiments have been performed on MD setup at optimized flow rates of 6 L/min on hot side and 3 L/min on cold side for producing the desired distillate. The hot side and cold side MD temperature has been maintained between 60 degrees C and 70 degrees C, and 20 degrees C and 30 degrees C. The total annual energy demand comes out to be 8,223 kWh (6,000 kWh is for pure water and 2,223 kWh for hot water). The optimum aperture areas for flat plate and evacuated tube collector field have been identified as 8.5 and 7.5 m(2), respectively. Annual energy consumption per liter for pure water production is 1, 0.85 and 0.7 kWh/L for different MD hot and cold inlet temperatures.

  • 226. Asim, Muhammad
    et al.
    Kumar, N. T. Uday
    Martin, Andrew R.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Feasibility analysis of solar combi-system for simultaneous production of pure drinking water via membrane distillation and domestic hot water for single-family villa: pilot plant setup in Dubai2016Ingår i: Desalination and Water Treatment, ISSN 1944-3994, E-ISSN 1944-3986, Vol. 57, nr 46, s. 21674-21684Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents the feasibility study of installation of a solar-driven integrated MD desalination system for simultaneous production of pure drinking water and solar domestic hot water in United Arab Emirates (UAE) for a single-family villa comprising of 4-5 persons. In order to satisfy the current and future demand of water for domestic purposes, the desalination of seawater is considered to be one of the most effective and strategic technique in UAE. The stress on the underground water aquifers, rapid industrial growth, and increase in urban population in UAE results in the tremendous increase in fresh water demand during the past few decades. Since the local municipalities also provide the desalinated fresh water to the people but they mostly rely on bottled water for drinking purpose. In this paper, the pilot setup plant is designed, commissioned, and installed on site in UAE using air gap membrane distillation desalination process to fulfill the demand of 15-25 L/d of pure drinking water and 250 L/d of domestic hot water for a single-family villa. Experimental analyses have been performed on this setup during summer on flat plate solar collectors having different aperture areas (Experiments have been performed for aperture area of 11.9 m(2) in this research study for feasibility purpose). The average hot-side temperature ranges from 50 to 70 degrees C and average cold-side temperature of 35 degrees C.

  • 227.
    Askin, Muharrem Kemal
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Calculations of Wind Turbine Flow in Yaw using the BEM Technique2011Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The earlier EU-sponsored project MEXICO (model experiments in controlled conditions) provided a huge database for flows past an experimental rotor in standard and yaw conditions. This study aims to determine the eligibility of different models under various conditions by using the MEXICO data. The main purpose of this project is to improve the BEM technique for yawed flows by using the new yaw model. Additionally, the BEM technique with new yaw model is compared with the CFD and measurement results. The Glauert’s yaw model is also applied in BEM model to compare the effectiveness of the new yaw model. It is proved that the CFD technique is still better than the BEM technique except at the high yaw and wind conditions. Furthermore, new yaw model is favored against Glauert’s yaw model. This project also aims to implement the new tip loss correction model in the BEM code and the results are validated with the CFD results.

  • 228.
    Askin, Muharrem Kemal
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Calculations of Wind Turbine Flow in Yaw using the BEM Technique2011Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The earlier EU-sponsored project MEXICO (model experiments in controlled conditions) provided a huge database for flows past an experimental rotor in standard and yaw conditions. This study aims to determine the eligibility of different models under various conditions by using the MEXICO data. The main purpose of this project is to improve the BEM technique for yawed flows by using the new yaw model. Additionally, the BEM technique with new yaw model is compared with the CFD and measurement results. The Glauert’s yaw model is also applied in BEM model to compare the effectiveness of the new yaw model. It is proved that the CFD technique is still better than the BEM technique except at the high yaw and wind conditions. Furthermore, new yaw model is favored against Glauert’s yaw model. This project also aims to implement the new tip loss correction model in the BEM code and the results are validated with the CFD results.

  • 229.
    Asvestas, Ioannis
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Pyrolysis of Waste Electrical and Electronic Equipment (WEEE) Plastics for Energy and Material Recovery2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Samhället strävar efter att ta itu med over utvinningen av jordens resurser på grund av den pågående befolkningsökningen. De ökade behoven hos energi och materiella resurser leder till en ökande mängd materialavfall, vilket inkluderar en mängd farliga föroreningar bland dem. Avfall av elektrisk och elektronisk utrustning utgör ett universellt problem på grund av sin stora mängd, ansvarig for miljöföroreningar och manga sjukdomar hos människor och djur. Den stora efterfrågan på elektrisk och elektronisk utrustning tillsammans med den korta livslängden på grund av dess föryngring leder till utvidgningen av WEBB-avfallsströmmen. Energi och materialåtervinning från WEBB kan betydligt minska over-extraktion av ädelmetaller och mineraler tillsammans med bränslen mot en mer hållbar framtid.

    För närvarande finns det flera sätt att behandla WEEE och återvinna materialfraktioner tillsammans med energi, såsom förbränning och deponering. Termokemisk behandling av WEEE erbjuder möjlighet att omvandla avfall till energi och material samtidigt, på ett miljövänligare sätt, vilket resulterar i en mer hållbar avfallshantering.

    I denna forskning undersöks pyrolys som en metod forenergi och materialåtervinning från WEEE. Bromerad plast tillsammans med polyetylenplastblandningar har förvärvats från Stena och Boliden AB separationsprocesser. Bada materialen utsätts for pyrolys i en fast bädd och en skruvreaktor. Pyrolysprodukterna visar deras starka förhållande till pyrolys-temperaturen, reaktortypen och den ursprungliga sammansättningen av rå materialet. De utförda experimenten visar den uppåtgående trenden hos de gasformiga produkterna till forman for oljorna som pyrolystemperaturokningen. Mängden fastsubstans förblev nästan vid samma nivåer genom temperaturintervallet, vilketinneblir att inga högre temperaturer behovs for att uppnå högresönderdelningshastigheter for det testade materialet. Oreagerat kol och oorganiska föreningar hamnar i den fasta återstoden som kan användas som bränsle vid förbränningsprocessen. Metallfraktionen kan separeras och återvinnas, eftersom den har kommersiellt värde.

    De angivna huvudolja-föreningarna var styren, toluen, etylbensen, alfa-metylstyrenbensen, fenol. Föreningar såsom bensen, inden och p-xylen framställdes när de organiska föreningarna sönderdelades vidare under försöken vid de högsta temperaturerna, Klor och brominnehall maste separeras for att vara ett formidabelt bränsle.

    Mängden brännbara gaser okade och deras energipotential med temperaturökningen. Den gasformiga fraktionen bestar huvudsakligen av: H2, CO, CH4, CO2, C2H2, C2H4, C2H6, C3H6, C3H8. Både gasformiga och oljeföreningar kan användas som bränslen i en förbränningsprocess. Mängden halogener mattes vid laga halter inom produktsortimentet, fastän deras separation lir viktig.

    Pyrolys av WEEE lir en lovande metod for energi och materialåtervinning som kan oka vart samhälles hållbarhet.

  • 230.
    Athukorala, Niluka
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Feasibility Study of Heat Driven Cooling Based Thermal Energy Storage2012Självständigt arbete på avancerad nivå (masterexamen), 30 poäng / 45 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Human needs are unlimited, but resources are limited to satisfy these needs. Because of this reason, consideration of sustainability in utilization of energy is of immense importance. As an intelligent species, mankind is interested in satisfying their needs sustainably. In this view, use of renewable energy, reduction of energy usage, and reduction/ elimination of use of fossil fuels are of great importance. It can be observed that there is rising demand for space cooling, and it has the highest share of energy consumption in the building sector. Colombo, Sri Lanka has a hot and humid climate, and above mentioned condition prominently prevails. On the other hand Sri Lanka experiences a considerable increase of energy demand and electricity tariff rates annually and this trend is prominent. Therefore the demand for finding energy efficient, renewable and cost effective solution is ever increasing. Accordingly, this study was carried out to conduct a techno-economic feasibility on thermal energy storage integrated into absorption chiller. Both these technologies are commercially available and have the measure towards sustainability. It was observed that most common air conditioning applications are in office buildings, and therefore the focus of this study is on a typical office building in Colombo city. The result of the study can be then applied to other office buildings in the city. Trace700 software tool was used to model and simulate the different system alternatives and to investigate the energy and economic performance. It was found that the cool thermal storage integrated into thermally driven absorption chiller has a good energy saving and cost saving potential and biogas can be a better energy source to supply the thermal energy required by the chiller and this energy is utilized in a sustainable manner.

  • 231.
    Attanayaka, T.L.B.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Open Source Energy Model for the Electricity Sector of Sri Lanka2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    I denna avhandling utvecklades en långsiktig modell för utbyggnad av elproduktion för elsektorn i Sri Lanka. Inom de användardefinierade begränsningarna som måste följas, ger modellen den minsta kostnaden för att tillgodose det framtida elbehovet. Med utgångspunkt från det nuvarande elsystemet i den sydasiatiska önationen, sträcker sig modellen över perioden 2018-2050.

    Open Source Energy Modeling System (OSeMOSYS) användes för att skapa modellen. Den utnyttjar linjär optimering och minimerar nuvärdet av det modellerade systemet under hela perioden. Fyra sektorer med slutanvändare av elektricitet modellerades, bostäder, industri, tjänster och transporter. Det slutliga elbehovet är för närvarande cirka 13 TWh och det förväntas växa med 5.6% per år under de närmaste tio åren till cirka 28 TWh år 2028 och stiga med 4.3% per år kommande år till att överstiga 61 TWh år 2050. Tolv bränslealternativ användes av befintliga och kandiderande teknologier för elproduktion i modellen, nämligen biomassa, kol, diesel, brännolja, vatten, flytande naturgas, nafta, naturgas, nukleär, restolja, sol och vind. Elproduktion på olika nivåer, såsom överföring, distribution och slutanvändares läge, modellerades i systemet. Kapitalkostnad, fast och rörlig drift och underhållskostnad och restvärde för teknik beaktades för kostnadsoptimering. Miljömässiga utsläpp inkluderades i modellen och koldioxidutsläppsgränsen på 20% för modellperioden inkluderades i basfallet för att representera landets förväntade utvecklingsväg i framtiden. Scenarioanalys genomfördes för att undersöka känsligheten hos inmatningsvariabler som efterfrågan på elektricitet och vattenförhållanden, och effekten av användardefinierade begränsningar till lösningen med minsta kostnaden. Integreringen av förnybar energi i systemet studerades och effekten av högre andelar av förnybar energi undersöktes. Kapacitetsmix, energimix, CO 2-utsläpp och LCOE av olika scenarier jämfördes i analysen.

  • 232.
    Aubach, Rene
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Design of a microclimate for improving thermal quality2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 233.
    Aue, Gabriela
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Energi och klimatstudier, ECS.
    The Possibilities for Biogas in Bolivia: Symbioses Between Generators of Organic Residues,  Biogas Producers and Biogas Users2011Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This master thesis investigates the potential use of biogas from organic residues in the area of the cities of La Paz and El Alto in Bolivia. The two cities have currently a contamination problem and biogas emerges as opportunity for both waste management and energy generation. There are approximately 274 500 tonnes/year of residue that can be used to produce biogas. This amount of residue can generate approximately 33,500,000 m3 of biogas. The advantages and disadvantages of five different digester types (the smaller tubular digester, the fixed dome digester, the floating drum digester and the bigger German AEV digester and a Swedish digester) were investigated to see if they could be an option for use in Bolivia. The German AEV digester is better when compared to the Swedish unit from Flotech in case a larger biogas digester would be implemented. Among the smaller digesters, the tubular digester already has access to the necessary resources and knowledge, and they can be operated at a cheap price. The fixed dome digester and the floating drum digester are  not used in Bolivia at present, and there is no knowledge in the country about how to implement them.  There are technical, social and economic issues related to an eventual installation of a big digester in Bolivia including transportation logistics and costs, how to motivate the population to sort out the different residues, and also the state subvention of natural gas production that lowers the price of biogas required to make it competitive. To see if it is economically viable to build a functional biogas generator for this area, economic data were compared. The analysis shows that the fixed dome and floating drum digester are much better economic investment than the tube digester. The bigger digesters are economically viable without financial aid if there is a market for the by- product fertiliser in Bolivia. The data for this analyse also shows that the conditions that exist today in Bolivia make it economically viable to invest in a bigger digester but only the fixed dome and the floating drum digester are economically viable without a market from the fertiliser

  • 234.
    Avgerinopoulos, Georgios
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Energisystemanalys.
    Strategic energy systems analysis:Possible pathways for the transition of electricity sector inTanzania2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This study examines the concept of the evolution of electricity sector in Tanzania.Electrification of Africa has raised large discussion and thus, nine scenarios based ondifferent production pathways and demand projections are formulated. The studyconsiders both grid based centralized electricity and decentralized power production.The main differentiation is between a centralized electricity system and decentralizedpower that are closer to demand. A model is created using three modeling tools(Answer-OSeMOSYS, LEAP and MESSAGE) and the results are presented andcompared. Finally, different funding options for electricity expansion projects inTanzania are explored in order to investigate the feasibility of the scenarios as well asa geopolitical analysis is carried out.

  • 235.
    Awan, Muhammad Rizwan
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Feasibility Study of Vertical Axis wind turbines in Urban areas of Sweden2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 236.
    Awan, Muhammad Rizwan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Riaz, Fahid
    Nabi, Zahid
    Analysis of conditions favourable for small vertical axis wind turbines between building passages in urban areas of Sweden2017Ingår i: International Journal of Sustainable Energy, ISSN 1478-6451, E-ISSN 1478-646X, Vol. 36, nr 5, s. 450-461Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents the analysis of installing the vertical axis wind turbines between the building passages on an island in Stockholm, Sweden. Based on the idea of wind speed amplification due to the venture effect in passages, practical measurements were carried out to study the wind profile for a range of passage widths in parallel building passages. Highest increment in wind speed was observed in building passages located on the periphery of sland as wind enters from free field. Wind mapping was performed in the island to choose the most favourable location to install the vertical axis wind turbines (VAWT). Using the annual wind speed data for location and measured amplification factor, energy potential of the street was calculated. This analysis verified that small vertical axis wind turbines can be installed in the passage centre line provided that enough space is provided for traffic and passengers.

  • 237.
    Awan, Umer Khalid
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Experimental analysis of variable capacity heat pump system equipped with vapour injection and permanent magnet motor2012Självständigt arbete på avancerad nivå (masterexamen), 80 poäng / 120 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This study analyzes the performance of variable capacity heat pump scroll compressor which is equipped with vapour injection and permanent magnet motor. Refrigerant used in the system is R410A. The study is divided in two phases. In first phase, tests are carried out for heat pump without vapour injection. Heat pump’s performance including COPs, heating/cooling capacities, inverter losses, heat transfer behaviour in condenser/evaporator are analyzed.

    Inverter losses increase but the ratio of inverter losses to the total compressor power decreases with increase in compressor speed. Electromechanical losses of compressor are much higher than the inverter losses and so make most part of the total compressor losses (summation of inverter and electromechanical losses).

    In second phase benefits of vapour injection are analyzed. For vapour injection, heat pump’s performance is evaluated for two different refrigerant charges: 1.15kg and 1.28kg. It is noted that heat pump performs better for refrigerant charge 1.15kg even at lower compressor speeds as compared to refrigerant charge 1.28kg. For refrigerant charge 1.15kg, heat pump COP cool with vapour injection increases by an average of 10.66%, while COP heat increases by an average of 9.4%, at each compressor speed except for 30Hz, as compared to conventional heat pump cycle with no vapour injection. Similarly refrigerant temperature at outlet of compressor also reduces with vapour injection which leads to the better performance of heat pump.

  • 238.
    Ayele, Getnet Tadesse
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik. IMT Atlantique, Department of Energy Systems and Environment, GEPEA, UBL, F-44307 Nantes, France.
    Haurant, Pierrick
    IMT Atlantique.
    Laumert, Björn
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Lacarrière, Bruno
    IMT Atlantique.
    An extended energy hub approach for load flow analysis of highly coupled district energy networks: Illustration with electricity and heating2018Ingår i: Applied Energy, Vol. 212, s. 850-867Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Energy systems at district/urban level are getting more complex and diversified from time to time. Different energy carriers are coupled each other to meet various types of energy demands. The conventional way of analyzing energy networks independently does not reflect the true nature of the coupled networks. One of such a promising coupled multi-carrier energy system (MCES) is the combination of district heating and electricity networks. The coupling between these two networks is increasing due to the integration of co– and poly-generation technologies at the distribution networks. Recent literatures tried to address a load flow analysis for lightly coupled networks by formulating case-specific load flow models. This paper presents a more general and flexible tool developed using Matlab® which can be used to conduct the load flow analysis of highly coupled electricity and heating networks. An energy hub concept is extended further to formulate a general model in which local generations and detailed network parameters of MCES can be taken into account. Coupled heating and electricity networks are modeled in detail for illustration. The flexibility and generality of the model are then tested by considering case studies with different network topologies (tree and meshed). A comparison is also made with a model used in recent literature. The results show that the proposed model is more accurate. The main contribution of this paper can be summarized by the following five points: (1) Coupling matrices are used to relate network power flow equations of different energy carriers; (2) Hybrid hydraulic head and pipe flow equations are used to develop the hydraulic model which can be applied for both types of tree and meshed heating networks with the possibility of pumping units; (3) A general thermal model that relates steady state temperature drops and mass flow rates, even during change of flow direction, is developed for the heating network; (4) The electricity network is modeled with the possibility of tap changing transformers; (5) The overall system of equations are solved as a single problem using Newton-Raphson iterative method.

  • 239.
    Ayele, Getnet Tadesse
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi. CNRS, UMR 6144, GEPEA, IMT Atlantique, F-44307 Nantes, France..
    Mabrouk, Mohamed Tahar
    CNRS, UMR 6144, GEPEA, IMT Atlantique, F-44307 Nantes, France..
    Haurant, Pierrick
    CNRS, UMR 6144, GEPEA, IMT Atlantique, F-44307 Nantes, France..
    Laumert, Björn
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi. KTH Royal Inst Technol, Dept Energy Technol, S-10044 Stockholm, Sweden..
    Lacarriere, Bruno
    CNRS, UMR 6144, GEPEA, IMT Atlantique, F-44307 Nantes, France..
    Optimal placement and sizing of heat pumps and heat only boilers in a coupled electricity and heating networks2019Ingår i: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 182, s. 122-134Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multi-energy systems are reported to have a better environmental and economic performance relative to the conventional, single-carrier, energy systems. Electrification of district heating networks using heat pumps and combined heat and power technologies is one such example. Due to lack of suitable modelling tools, however, the sizing and optimal placement of heat pumps is always done only from the heating network point of view which sometimes compromises the electricity network. This paper proposes an integrated optimization algorithm to overcome such limitation. A load flow model based on an extended energy hub approach is combined with a nested particle swarm optimization algorithm. A waste to energy combined heat and power plant, heat pumps (HPs), heat only boiler (HOB), solar photovoltaic, wind turbines and imports from the neighborhood grids are considered in the case studies. The results show that optimal placement and sizing of HPs and a HOB using the proposed methodology avoids an unacceptable voltage profiles and overloading of the electricity distribution network, which could arise while optimizing only from the heating network point of view. It also shows that up to 41.2% of the electric loss and 5% of the overall operating cost could be saved.

  • 240.
    Ayele, Getnet Tadesse
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik. IMT Atlantique, Department of Energy Systems and Environment.
    Mabrouk, Mohamed Tahar
    IMT Atlantique, Department of Energy Systems and Environment.
    Haurant, Pierrick
    IMT Atlantique, Department of Energy Systems and Environment.
    Laumert, Björn
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Lacarrière, Bruno
    IMT Atlantique, Department of Energy Systems and Environment.
    Pseudo-dynamic simulation on a district energy system made of coupling technologies2018Ingår i: Proceedings of ECOS 2018 - the 31st International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems June 17-22, 2018, Guimarães, PORTUGAL, University of Minho , 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    As part of an effort towards the future smart energy system, integration of different distributed generation technologies is proposed in literature. These technologies include heat pumps, gas boilers, combined heat and power (CHP) plants, solar photo-voltaic (PV) and so on. Some of these technologies couple different energy carriers in which case the independent analysis of each network could lead to unrealistic results. Optimization of heat pumps and CHP plants in coupled electricity and heating network, for example, needs consideration of both networks’ parameters in order to get results that are optimal in both networks. The first step in such optimization process is to have a load flow model (as an equality constraint) for the two coupled networks. Even though many researchers tried to address optimization of energy mixes at a district level, they did not consider the details of network parameters. Too little has been done to investigate the effect of different distributed generation technologies on the operational parameters of different energy networks. This paper deals with a pseudo-dynamic simulation of a district energy system that consists of coupled electricity and heating networks. The details of transmission line and pipe parameters together with the coupling devices are modelled using an extended energy hub approach. A network of six energy hubs with different distributed generation technologies such as heat pump, gas boiler, CHP and Solar PV is considered in the simulation. Time series data for demands and generations at different hubs are used on hourly basis. The CHP and heat pumps are scheduled to operate in certain period of the year while the PV output follows the annual solar radiation. Annual pseudo-dynamic load flow simulation is done to see how the operational parameters and power losses in the network vary with hourly changes in demands, generations and loading of coupling technologies.

  • 241.
    Ayele, Getnet Tadesse
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Mabrouk, Mohamed Tahar
    IMT Atlantique - DSEE - Département Systèmes énergétiques et environnement.
    Haurant, Pierrick
    IMT Atlantique - DSEE - Département Systèmes énergétiques et environnement.
    Laumert, Björn
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Lacarrière, Bruno
    IMT Atlantique - DSEE - Département Systèmes énergétiques et environnement.
    Santarelli, Massimo
    Polito - Politecnico di Torino.
    Exergy analysis and thermo-economic optimization of a district heating network with solar- photovoltaic and heat pumps2019Ingår i: Proceedings of the 32nd International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems / [ed] Wojciech Stanek, Paweł Gładysz, Sebastian Werle, Wojciech Adamczyk, 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    Electrification of district heating networks, especially using heat pumps, is widely recommended in literature. Installing heat pumps affects both electricity and heating networks. Due to lack of suitable modelling tools, size optimization of heat pumps in the heating network with the full consideration of the electric distribution network is not well addressed in literature. This paper presents an optimization of a district heating network consisting of solar photovoltaic and heat pumps with the consideration of the detail parameters of heating and electric distribution networks. An extended energy hub approach is used to model the energy system. Exergy and energy analyses are applied to identify and isolate lossy branches in a meshed heating network. Both methods resulted into the same reduced topology. Particle swarm optimization is then applied on the reduced topology in order to find out the most economical temperature profiles and size of distributed heat pumps. The thermo-economic results are found to be highly influenced by the heat demand distribution, the power loss in both electric and heat distribution network, the cost of generation, the temperature limits and the coupling effect of the heat pumps.

  • 242.
    Ayuso, Maria
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Energisystemanalys.
    Cooperation Strategies to Support Research, Development and Demonstration of Renewable Energy Technologies within the Innovation Policy Frameworks in the Latin America and the Caribbean Region2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    IRENA is an intergovernmental organization mandated with the promotion, increased adoption and the sustainable use of all forms of renewable energy. IRENA serves as the principal platform for international cooperation, center of excellence, and a repository of policy, technology, resource and financial knowledge on renewable energy.

    As part of this mandate, IRENA seeks to stimulate the Research, Development and Demonstration (RD&D) of Renewable Energy Technologies (RET). Hence, fostering cooperation and strengthening innovation instruments are key focus areas of the Agency’s Programme of Work for 2013. The Latin America and the Caribbean (LAC) region has been selected as a region of focus for this effort.

    This thesis addresses IRENA’s efforts in reinforcing current cooperation mechanisms in LAC. The project seeks to identify initiatives, drivers and opportunities of cooperation in LAC, and supports IRENA’s role as a promoter of RD&D in RET. It analyses existing gaps in cooperation to provide strategies to overcome barriers to innovation.

  • 243.
    Azizi, Shoaib
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Castelló Pérez, Luis
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Novel defrost techniques on air source heat pumps2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Denna studie syftade till att nå en ny lösning för avfrostningen problem för luftvärmepumpar. För att uppnå detta mål, var studien uppdelad i 3 olika delar. En litteraturstudie om vad industrin och akademin utnyttjar nu; ett riktmärke studie med produkter som passar in i ett specifikt område av egenskaper och välj sedan och prova en av de möjliga lösningarna i laboratoriet.

    En litteraturundersökning gjordes för att söka efter alternativa lösningar för avfrostning för luftvärmepumpar. Flera typer av lösningar hittades och de kan delas på elavfrostning, varm gas injektion metoder avancerade lutande system, pre-torr behandling av luft, ytbehandling av värmeväxlaren, termisk energilagring och andra typer av lösningar som inte kan placeras i de tidigare etiketter.

    Riktmärket studie gjordes samtidigt med litteraturstudien och två produkter av 9000 Btu/h värmeeffekt var demonteras och testades i psychrometric kammare Electrolux AB i Stockholm. Resultaten var olika och vissa slutsatser uppnåddes, men den största skillnaden mellan enheterna var kondensationstemperaturen under avfrostning, som är relaterad till en högre värmeväxling mellan kylmediet och frost, också noterades att styrningen av kompressorn och elektroniska expansionsventil, kan en hög optimering av dessa förbättras avsevärt avfrostning av en luftvärmepumpen.

    Lösningen valts för att ställas inför rätta i labbet baserades på en termisk energilagring som använder fasomvandlingsmaterial (PCM). En PCM värmeväxlare designat, byggt och installerat i testriggen. Två typer av PCM utnyttjades, med smältpunkter av 18 ° C och 28 ° C. De jämfördes med en referens utan PCM termisk energilagring. Resultaten visade att 18ºC är inte en livskraftig val för en smältpunkt av PCM, och med denna lösning avfrostningen med hjälp av 28ºC PCM, kan värmeöverföringen förbättras 57%, vilket innebär en kortare avfrostningsperiod. Dessutom kan avfrostningscykeln tiden minskas upp till en 67% och energiförbrukningen under avfrostning också minskat med 70%.

  • 244.
    Baagherzadeh Hushmandi, Narmin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Numerical Analysis of Partial Admission in Axial Turbines2010Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    HTML clipboard Numerical analysis of partial admission in axial turbines is performed in this work. Geometrical details of an existing two stage turbine facility with low reaction blades is used for this purpose. For validation of the numerical results, experimental measurements of one partial admission configuration at design point was used. The partial admission turbine with single blockage had unsymmetrical shape; therefore the full annulus of the turbine had to be modeled numerically.

    The numerical grid included the full annulus geometry together with the disc gaps and rotor shrouds. Importance of various parameters in accurate modeling of the unsteady flow field of partial admission turbines was assessed. Two simpler models were selected to study the effect of accurate modeling of radial distribution of flow parameters. In the first numerical model, the computational grid was two dimensional and the radial distribution of flow parameters was neglected. The second case was three-dimensional and full blades’ span height was modeled but the leakage flows at disc cavity and rotor shroud were neglected. Detailed validation of the results from various computational models with the experimental data showed that modeling of the leakage flow at disc cavities and rotor shroud of partial admission turbines has substantial importance in accuracy of numerical computations. Comparison of the results from two computational models with varying inlet extension showed that modeling of the inlet cone has considerable importance in accuracy of results but with increased computational cost.

    Partial admission turbine with admission degree of  ε = 0.524 in one blocked arc and two opposing blocked arcs were tested. Results showed that blocking the inlet annulus in one single arc produce better overall efficiency compared to the two blocked arc model. Effect of varying axial gap distance between the first stage stator and rotor rows was also tested numerically for the partial admission turbine with admission degree of  ε = 0.726. Results showed higher efficiency for the reduced axial gap model.

    Computations showed that the main flow leave the blade path down to the disc cavity and re-enter into the flow channel downstream the blockage, this flow would pass the rotor with very low efficiency. First stage rotor blades are subject to large unsteady forces due to the non-uniform inlet flow. Plotting the unsteady forces of first stage rotor blades for partial admission turbine with single blockage showed that the blades experience large changes in magnitude and direction while traveling along the circumference. Unsteady forces of first stage rotor blades were plotted in frequency domain using Fourier transform. The largest amplitudes caused by partial admission were at first and second multiples of rotational frequency due to the existence of single blockage and change in the force direction.

    Results obtained from the numerical computations showed that the discs have nonuniform pressure distribution especially in the first stage of partial admission turbines. The axial force of the first rotor wheel was considerably higher when the axial gap distance was reduced between the first stage stator and rotor rows. The commercial codes used in this work are ANSYS ICEM-CFD 11.0 as mesh generator and FLUENT 6.3 as flow solver.

  • 245.
    Baagherzadeh Hushmandi, Narmin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Fransson, Torsten
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Effects of multiblocking and axial gap distance on performance of partial admission turbines: A numerical analysis2011Ingår i: Journal of turbomachinery, ISSN 0889-504X, E-ISSN 1528-8900, Vol. 133, nr 3, s. 031028-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the effects of axial gap distance between the first stage stator and rotor blades and multiblocking on aerodynamics and performance of partial admission turbines are analyzed numerically. The selected test case is a two stage axial steam turbine with low reaction blades operating with compressed air. The multiblocking effect is studied by blocking the inlet annulus of the turbine in a single arc and in two opposing blocked arcs, each having the same admission degree. The effect of axial gap distance between the first stage stator and rotor blades is studied while varying the axial gap by 20% compared with the design gap distance. Finally, full admission turbine is modeled numerically for comparison. Performance of various computational cases showed that the first stage efficiency of the two stage partial admission turbine with double blockage was better than that of the single blockage turbine; however, the extra mixing losses of the double blockage turbine caused the efficiency to deteriorate in the downstream stage. It was shown that the two stage partial admission turbine with smaller axial gap than the design value had better efficiency of the first stage due to lower main flow and leakage flow interactions; however, the efficiency at the second stage decreased faster compared with the other cases. Numerical computations showed that the parameters, which increased the axial force of the first stage rotor wheel for the partial admission turbine, were longer blocked arc, single blocked arc, and reduced axial gap distance between the first stage stator and rotor blades.

  • 246.
    Baagherzadeh Hushmandi, Narmin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Fridh, Jens
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Fransson, Torsten
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Unsteady Forces of Rotor Blades in Full and Partial Admission Turbines2011Ingår i: Journal of turbomachinery, ISSN 0889-504X, E-ISSN 1528-8900, Vol. 133, nr 4, s. 041017-1-041017-12Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A numerical and experimental study of partial admission in a low reaction two-stage axial air test turbine is performed in this paper. In order to model one part load configuration, corresponding to zero flow in one of the admission arcs, the inlet was blocked at one segmental arc, at the leading edge of the first stage guide vanes. Due to the unsymmetrical geometry, the full annulus of the turbine was modeled numerically. The computational domain contained the shroud and disk cavities. The full admission turbine configuration was also modeled for reference comparisons. Computed unsteady forces of the first stage rotor blades showed cyclic change both in magnitude and direction while moving around the circumference. Unsteady forces of first stage rotor blades were plotted in the frequency domain using Fourier analysis. The largest amplitudes caused by partial admission were at first and second multiples of rotational frequency due to the existence of single blockage and change in the force direction. Unsteady forces of rotating blades in a partial admission turbine could cause unexpected failures in operation; therefore, knowledge about the frequency content of the unsteady force vector and the related amplitudes is vital to the design process of partial admission turbine blades. The pressure plots showed that the nonuniformity in the static pressure field decreases considerably downstream of the second stage's stator row, while the nonuniformity in the dynamic pressure field is still large. The numerical results between the first stage's stator and rotor rows showed that the leakage flow leaves the blade path down into the disk cavity in the admitted sector and re-enters downstream of the blocked channel. This process compensates for the sudden pressure drop downstream of the blockage but reduces the momentum of the main flow.

  • 247.
    Baagherzadeh Hushmandi, Narmin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Hu, Jiasen
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Fridh, Jens
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Fransson, Torsten
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Numerical Investigation of Partial Admission Phenomena at Midspan of an Axial SteamTurbine2007Ingår i: Proceedings of 7th European Conference on Turbomachinery,Fluid Dynamics and Thermodynamics, 2007Konferensbidrag (Refereegranskat)
  • 248.
    Baagherzadeh Hushmandi, Narmin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Hu, Jiasen
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Fridh, Jens
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Fransson, Torsten
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Numerical Study of Unsteady Flow Phenomena in a Partial Admission Axial Steam Turbine2008Ingår i: Proceedings of ASME Turbo EXPO 2008, New York: AMER SOC MECHANICAL ENGINEERS , 2008, s. 713-722Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a numerical investigation of unsteady flow phenomena in a two-stage partial admission axial steam turbine. Results from unsteady three-dimensional computations are analyzed and compared with the available experimental data. Partial admission in the present study is introduced into the model by blocking only one segmental arc of the inlet guide vanes. Blocking only one segment (which corresponds to the experimental setup) makes the model unsymmetrical; therefore it is necessary to model the whole annulus of the turbine. The first stage rotor blades experience large static pressure change on their surface while passing the blocked channel. The effect of blockage on the rotor blades' surface pressure can be seen few passages around the blocked channel. Strong changes of the blades' surface pressure impose large unsteady forces on the blades of first stage rotor row.

    The circumferential static pressure plots at different cross sections along the domain indicate how the non-uniformity propagates in the domain. A peak pressure drop is seen at the cross section downstream of the first stage stator row. At further downstream cross sections, the static pressure becomes more evenly distributed. Entropy generation is higher behind the blockage due to the strong mixing and other loss mechanisms involved with partial admission. Analysis of the entropy plots at different cross sections indicates that the peak entropy moves in a tangential direction while traveling to the downstream stages. Comparisons of the unsteady three-dimensional numerical results and the experimental measurement data show good agreement in tendency. However some differences are seen in the absolute values especially behind the blockage.

  • 249.
    Baaklini, Daniel
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Performance analysis of Air GapMembrane Distillation:Comparison of PTFE membranes: Comparison of PTFE membranes2011Självständigt arbete på avancerad nivå (masterexamen), 30 poäng / 45 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Membrane Distillation (MD) is a very promising new technology which can be coupled with renewableenergies and/or waste heat to produce pure water at a low-cost. MD is extremely dependent upon theperformance of the membrane, as it dictates the mass transfer, the heat transfer and the long-termapplication. Unfortunately, there are no commercially produced MD-specific membranes at this point intime. This project aims at finding correlations between membrane characteristics and their performancesin order to define the optimal morphologies and operating conditions for a MD-specific membrane. Todo so, the characteristics of 3 PTFE membranes initially designed for MF were determined throughporosity measurements and microscopic imaging, while their performances were evaluated by measuringthe air permeability and by testing them on an AGMD bench-scale unit.It was found that the most desirable characteristics for a membrane with a high flux are a film with largeporosity, low tortuosity, a small thickness with a resistance to compaction and that has not been subjectedto thickness altering processes. Moreover, the surface pore sizes need to be small enough to avoid surfacewetting, and the backing layer should not restrict the vapor flow in a significant way and should possesslarge open areas.As the feed water temperature and/or the flow rate rises, the flux increases and the energy requirementdecreases, this means that one should ideally aim for the highest possible operating conditions whichrequires larger costs. Therefore it is necessary to find a cost effective solution for each application.The results show that, for comparative purposes, Gurley values are good indicators of a membrane’soverall performance in MD, despite the fact that it does not always accurately predict it. It has also beenfound that membrane specifications provided by manufacturers are generally only approximations, andshould therefore not be used as very precise data for comparing membranes.

  • 250.
    Back, Izabelle
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Dunberger, Lars
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Evaluating alternative refrigerants for the room air conditioner market2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This study aimed to facilitate evaluation of alternative refrigerants for the air conditioner market. In order to achieve this target, two objectives were set. The first being the identification of alternative refrigerant with regard to regulations and trends. The second being enabling of thermodynamic evaluation of refrigerants for single components in air conditioners via design and installation of a test rig. A literature review was conducted to investigate the regulations, standards and trends for nine regions with high market shares. Furthermore, refrigerant substitutes for R410A and R22 where identified. The literature showed strong indications that a global HFC phase down is on the horizon, but that the approach and urge for such a phase down varies between regions where three main priorities could be seen; efficiency, GWP values and safety. Comparing these priorities with simulated refrigerant characteristics such as Carnot efficiency, GWP values, volumetric capacity and the liquid density using RefProp, identified alternatives. Further the literature showed that the lower flammability limit (LFL) and the amount of charge allowed were limiting factors for flammable refrigerant. There are many new refrigerants that could have less charge for the same capacity the LFL however restricts the refrigerants like R290, R441A and R443A only to be used in small systems. A test rig was designed and constructed in order to enable testing of single components in air conditioners. To verify the test rig, tests conducted with an evaporator using two refrigerants: R410A and R32. The reliability and validity of the tests was studied by comparing the results from the air side and refrigerant side, via uncertainty calculations using the GUM method and by a thermodynamic evaluation. The results of the repetition tests showed an expanded uncertainty, with a confidence interval of 95%, of 26 W for a cooling capacity of 2190W for R410A (Q̇evap,R410A=2190±26W). For R32 the expanded uncertainty was 27W for a cooling capacity of 2795W (Q̇evap,R32=2795±27W). Also the test rig was verified to be used for analyzing detailed evaluation of evaporators such as looking at heat transfer and the differential pressure drop. Further the study presented six conclusions:

    • When evaluating refrigerants regional priorities between efficiency, safety and GWP values, refrigerant characteristics and type of unit need to be considered.
    • Safety standards need to be more acceptable towards flammable refrigerants in order to meet low GWP targets.
    • The change in market trends leads to new roles for the refrigerant and compressor suppliers and put higher demand on air conditioner manufacturers to consider refrigerant characteristics in product development.
    • The importance of experimental thermodynamic evaluation on refrigerants effect on single components is increasing.
    • Performance of different refrigerant for single components can be evaluated for optimizing cycle performance.
    • Leapfrogging in the developing world can lead to a faster introduction of low GWP refrigerants. 

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