Effect of base–acid properties of the mixtures of water with methanol on the solution enthalpy of selected cyclic ethers in this mixture at 298.15 K

The enthalpies of solution of cyclic ethers: 1,4- dioxane, 12-crown-4 and 18-crown-6 in the mixture of water and methanol have been measured within the whole mole fraction range at T = 298.15 K. Based on the obtained data, the effect of base–acid properties of water– methanol mixtures on the solution enthalpy of cyclic ethers in these mixtures has been analyzed. The solution enthalpy of cyclic ethers depends on acid properties of water– methanol mixtures in the range of high and medium water contents in the mixture. Based on the analysis performed, it can be assumed that in the mixtures of high methanol contents, cyclic ethe

Design and comparison of PMaSynRM versus PMSM for pumping applications

This master thesis aimed to design a permanent magnet assisted synchronous reluctancemachine (PMaSynRM) rotor for pump applications which were to be implemented inan existing Induction Machine stator. The machine were to be compared with a similarpermanent magnet synchronous machine (PMSM) with similar torque production in termsof cost and performance.This thesis goes through the theory of the Synchronous Reluctance Machine andthe Permanent Magnet assistance. A rotor was designed by utilizing existing design approachesand simulation of performance by use of finite element analysis. A demagnetizationstudy was conducted on the added permanent magnets in order to investigate thefeasiblity of the design.The final design of the PMaSynRM was thereafter compared to the equivalentsurface-mounted PMSM in terms of performance and cost. The performance parameterswas torque production, torque ripple, efficiency and power factor. Due to the lower torquedensity of the PMaSynRM, for equal torque production the PMSM had a 40% shorterlamination stack than the PMaSynRM.The economic evaluation resulted in that when utilizing ferrite magnets in the PMa-SynRM it became slightly cheaper than the PMSM, up to 20%. However, due to the fluctuatingprices of NdFeB magnets, there exist breakpoints below which the PMaSynRM isin fact more expensive than the PMSM or where the price reduction of the PMaSynRMis not worth the extra length of the motor. However, it was shown that the PMaSynRMis very insensitive to magnet price fluctuations and thereby proved to be a more securechoice than the PMSMDetta examensarbete avsåg att designa en rotor till en permanentmagnetsassisteradsynkron reluktansmaskin (PMaSynRM) för pumpapplikationer, vilken skulle implementeras i en befintlig asynkronmaskin (IM) stator. Maskinen jämfördes ekonomiskt och prestandamässigt med en liknande synkronmaskin med permanentmagneter (PMSM) med jämförbar vridmomentsproduktion.Uppsatsen avhandlar teorin bakom synkrona reluktansmaskiner och konceptet kring permanentmagnetassistans. Rotorn designades genom användandet av befintliga designmetoder och simulering genom finit elementanalys (FEA). En avmagnetiseringsstudie utfördes på de adderade magneterna för att undersöka rimligheten kring designenDen slutgiltiga designen av PMaSynRMen jämfördes därefter mot den jämlika PMSMen i termer om prestanda och kostnad. De undersökta prestandaparameterarna var vridmoment, vridmomentsrippel, verkningsgrad och effektfaktor. Eftersom vridmomentsdensiteten i en PMaSynRM är lägre än hos en PMSM så visade sig PMSMen ha en 40% kortare lamineringskropp än PMaSynRMen vid jämnlik vridmomentsproduktion.Den ekonomiska utvärderingen resulterade i att vid användandet av ferritmagneter i PMaSynRMen så blev den något billigare än PMSMen, upp till 20%. På grund av fluktuerande priser hos NdFeB magneter, så finns det brytpunkter där PMaSynRMen faktiskt blir dyrare än PMSMen eller då kostnadsreduktionen för PMaSynRMen kan bedömas att vara för låg med tanke på den ökade längden och vridmomentsrippel. Däremot visades det att PMaSynRMen är väldigt okänslig för prisvariationer och därför visades vara ettkostnadsmässigt tryggare val än PMSMe

Design and comparison of PMaSynRM versus PMSM for pumping applications

This master thesis aimed to design a permanent magnet assisted synchronous reluctancemachine (PMaSynRM) rotor for pump applications which were to be implemented inan existing Induction Machine stator. The machine were to be compared with a similarpermanent magnet synchronous machine (PMSM) with similar torque production in termsof cost and performance.This thesis goes through the theory of the Synchronous Reluctance Machine andthe Permanent Magnet assistance. A rotor was designed by utilizing existing design approachesand simulation of performance by use of finite element analysis. A demagnetizationstudy was conducted on the added permanent magnets in order to investigate thefeasiblity of the design.The final design of the PMaSynRM was thereafter compared to the equivalentsurface-mounted PMSM in terms of performance and cost. The performance parameterswas torque production, torque ripple, efficiency and power factor. Due to the lower torquedensity of the PMaSynRM, for equal torque production the PMSM had a 40% shorterlamination stack than the PMaSynRM.The economic evaluation resulted in that when utilizing ferrite magnets in the PMa-SynRM it became slightly cheaper than the PMSM, up to 20%. However, due to the fluctuatingprices of NdFeB magnets, there exist breakpoints below which the PMaSynRM isin fact more expensive than the PMSM or where the price reduction of the PMaSynRMis not worth the extra length of the motor. However, it was shown that the PMaSynRMis very insensitive to magnet price fluctuations and thereby proved to be a more securechoice than the PMSMDetta examensarbete avsåg att designa en rotor till en permanentmagnetsassisteradsynkron reluktansmaskin (PMaSynRM) för pumpapplikationer, vilken skulle implementeras i en befintlig asynkronmaskin (IM) stator. Maskinen jämfördes ekonomiskt och prestandamässigt med en liknande synkronmaskin med permanentmagneter (PMSM) med jämförbar vridmomentsproduktion.Uppsatsen avhandlar teorin bakom synkrona reluktansmaskiner och konceptet kring permanentmagnetassistans. Rotorn designades genom användandet av befintliga designmetoder och simulering genom finit elementanalys (FEA). En avmagnetiseringsstudie utfördes på de adderade magneterna för att undersöka rimligheten kring designenDen slutgiltiga designen av PMaSynRMen jämfördes därefter mot den jämlika PMSMen i termer om prestanda och kostnad. De undersökta prestandaparameterarna var vridmoment, vridmomentsrippel, verkningsgrad och effektfaktor. Eftersom vridmomentsdensiteten i en PMaSynRM är lägre än hos en PMSM så visade sig PMSMen ha en 40% kortare lamineringskropp än PMaSynRMen vid jämnlik vridmomentsproduktion.Den ekonomiska utvärderingen resulterade i att vid användandet av ferritmagneter i PMaSynRMen så blev den något billigare än PMSMen, upp till 20%. På grund av fluktuerande priser hos NdFeB magneter, så finns det brytpunkter där PMaSynRMen faktiskt blir dyrare än PMSMen eller då kostnadsreduktionen för PMaSynRMen kan bedömas att vara för låg med tanke på den ökade längden och vridmomentsrippel. Däremot visades det att PMaSynRMen är väldigt okänslig för prisvariationer och därför visades vara ettkostnadsmässigt tryggare val än PMSMe

Central kontra distribuerad tillståndsuppskattning för hybrida AC/DC nät

State estimation enables for values throughout a power transmission grid to be known with a higher level of certainty. New technologies for bulk power transmission and power grid measuring enables for new possibilities in the energy sector and it is required that state estimation algorithms are developed to adapt to these new technologies. This project aims to develop a state estimator (SE) that is modified for hybrid AC/HVDC grids with voltage source converters (VSC) and phasor measurement units (PMU). Two different sets of architectures are tested. The centralized architecture where one common SE is implemented for both AC and DC grids or the distributed where a separate SE for every grid is used. The method used for the SE is the weighted least square (WLS) method. The SE will be developed based on the power grid model ’The CIGRE B4 DC Grid Test System’, designed by the International Council on Large Electric Systems (CIGRE) as a benchmark system. The SE is subject to four different scenarios in order to evaluate the quality of the SE, benefits of added phasor measurements and choice of architecture for the SE. The results of the tests show that the developed SE improves the accuracy of state values on the DC grid. However, regarding the AC state values of the converters the results of the test are ambiguous. Furthermore the distributed architecture offered slightly less accurate AC values than the centralized. The addition of PMU measurements improved the error of the estimated values.

Hydration of a natural polyelectrolyte xanthan gum : Comparison with non-ionic carbohydrates

In dilute solutions, polyelectrolytes exhibit more hydrophilic properties than non-charged polymers do. However, extension of this statement on almost dry systems is questionable. In this study we present sorption calorimetric data on hydration of a natural carbohydrate polyelectrolyte xanthan gum and make comparison with analogous data of three types of cellulose which is a non-charged carbohydrate polymer. An analysis of the sorption isotherm shows that at given relative humidities xanthan gum absorbs greater amount of water than non-charged cellulose does. Nonetheless, the enthalpies of hydration of xanthan gum and of all three considered types of cellulose at zero water content are equal to −18 kJ/mol. Thus, entropy of hydration plays an important role in water sorption behaviour of xanthan gum. The apparent absence of an ion effect on polymer–water interactions can be explained by solvation of ions by OH-groups of the dry xanthan gum. Ab initio calculations presented here show that solvation of an ionic group of xanthan gum by a carbohydrate hydroxyl is as strong as hydration of the same group by water. The exothermic heat effect of hydration arises from the loss of the mobility of water on the rigid glassy environment of the polymer. For the first time, the glass transition temperature of dry xanthan gum is reported to be 60 °C

Hydration and dehydration induced changes in porosity of starch microspheres

Characterization and tuning of the porosity of amorphous starch materials are important for many applications, including controlled release of encapsulated proteins. The porosities of these materials in dry and hydrated states can have different physicochemical origins and properties. Here, porosities of dry cross-linked starch microspheres and their hydration-induced transformations were characterized by small angle X-ray scattering, scanning electron and optical microscopies, thermogravimetric analysis, sorption calorimetry, nitrogen sorption, and helium-pycnometry. The analyses revealed that dry microspheres consist of porous cores with pore diameters below 100 nm and shells which appeared to be denser but contained wider pores (100–300 nm). The outer crust of the microspheres shell is non-porous, which restricts diffusion of nitrogen, water, and ethanol. Partial hydration triggered an irreversible collapse of dry porosity at 12 wt% water. Further hydration resulted in interfacial changes and promoted wet porosity, related to characteristic distances between polymer chains

Design and testing of a small-scale sublimation apparatus

In many areas of scientific research and development, for example in the pharmaceutical industry, it is important to prepare and to characterize crystals of pure organic compounds which are thermodynamically stable. The formation of crystals from the gas phase is technically less straightforward than crystallisation from solution, but sublimation techniques can have several important features. In the present paper we report the design and testing of a novel apparatus for small scale sublimation and fractional deposition of crystals. The instrument has been developed with special reference to the needs in the pharmaceutical industry. A few mg of the samples are enclosed, under reduced pressure, in thin-walled glass tubes, along which a well defined temperature gradient can be formed. During an experiment the substance will sublime from the hot end of the glass tube and crystals will be deposited along the temperature gradient. The applicability of the instrument has been verified by experiments with several test compounds. Results from experiments with carbamazepine, are reported in some detail. Carbamazepine single crystals of high quality were obtained and the transition temperature between the triclinic (Form I) and the monoclinic (Form III) crystal modifications agreed with literature values