Particle Deposition From Geothermal Supercritical Steam

Varmeutvinning fra dype varme geotermiske brønner kan føre til en størrelsesorden høyere effekt sammenlignet med konvensjonelle geotermiske brønner (Fridleifsson et al. 2003). Et slikt energipotensial kan imidlertid ikke utnyttes med dagens teknologi. Årsaken til dette er den spesielt raske utfelling av SiO2-partikler av submikron størrelse fra trykkavlastet overopphetet vanndamp, noe som resulterer i påfølgende høye avsetningshastigheter og beleggdannelse på røroverflater og prosessutstyr, noe som er problematisk. Følgende arbeid består av numeriske og eksperimentelle metoder for å utforske dominerende transportmekanismer for partikler av submikron størrelse og for å kvantifisere avsetningshastigheter fra overopphetet og superkritisk vanndamp i turbulente strømningskanaler. I dette arbeidet er det etablert en numerisk modell (PARTICLE) i den kommersielle programvaren ANSYS Fluent 20.2 for banefølging av submikronpartikler ved bruk av brukerdefinerte funksjoner (UDF). En grenseskikt-modell og korreksjoner til modellen for øyeblikkelige turbulente hastighetssvingninger er implementert i PARTICLE-modellen for å adressere feil-genererte resultater i standardmodellen i ANSYS Fluent. Ved å bruke Reynolds stress-ligningsmodell (RSM) for hastighetsfeltet og de gjennomsnittlige turbulente hastighetssvingningene i en strømningskanal, ble PARTICLE-modellen ble validert og viste meget godt samsvar med eksperimentelle, numeriske og empiriske resultater fra literaturen ved atmosfæriske luftforhold. Den etablerte PARTICLE-modellen muliggjør forbedrede simuleringer av submikron partikkelavsetninger ved bruk av ANSYS Fluent. Anvendelsen av PARTICLE-modellen ved geotermiske forhold avslørte overvurderte diffusjonshastigheter for submikronpartikler sammenlignet med empiriske korrelasjoner. Derfor blir ytterligere validering av de benyttede modellene og de resulterende konsentrasjonsprofilene i de geotermiske forholdene anbefalt for videre arbeid. Bidrag til en eksperimentell studie av utfelling, agglomerering og avsetning av trykkredusert overopphetet og superkritisk vanndamp overmettet med ortokiselsyre er gjennomført. Det foreslås en beregningsprosedyre for å sammenligne eksperimentelle og numeriske resultater av avsetningshastighet ved å inkludere en partikkelstørrelsesfordeling fra den numeriske modellen til Bordvik, Næss et al. (2021). Validering med resultatene fra denne eksperimentelle studien anbefales, da mulige avvik fra de numeriske prediksjonene kan være relatert til frastøtende krefter på veggen.Heat extraction from deep hot geothermal wells may lead to an order of magnitude higher power output than conventional geothermal wells (Fridleifsson et al. 2003). However, such energy potential cannot be exploited with current technologies. The reason for this is that precipitation of submicron-sized particles of SiO2 from depressurised superheated water vapour is especially fast in the gaseous phase, resulting in subsequent high rates of deposition and scaling onto pipe surfaces and process equipment, which is problematic. Numerical and experimental methods are conducted to explore dominant submicron particle transport mechanisms and to quantify deposition rates from superheated and supercritical water vapour in turbulent channel flows. In this work, a numerical model (PARTICLE) is established in the commercial software ANSYS Fluent 20.2 for submicron particle tracking with the use of user-defined functions (UDFs). A boundary layer model and correction terms to the model for the instantaneous turbulent velocity fluctuations are implemented in the PARTICLE model to address spurious results in the default model in ANSYS Fluent. By employing the Reynolds stress equation model (RSM) for the turbulence mean flow simulation, the PARTICLE model was validated and showed very good agreements with experimental, numerical and empirical results in ambient conditions of air. The established PARTICLE model facilitates improved submicron particle deposition simulations using ANSYS Fluent. Subsequent application of the PARTICLE model at the geothermal conditions revealed overestimated diffusion rates for submicron particles compared to empirical correlations. Therefore, further validation of the employed models and the predicted concentration profiles in the geothermal conditions is emphasised. Contributions to an experimental investigation on the precipitation, agglomeration and deposition of depressurised superheated and supercritical water vapour supersaturated with silicic acid were made. A calculation procedure is proposed to compare the experimental and numerical deposition results by including a particle size distribution from the numerical model of Bordvik, Næss et al. (2021). Validation with the results from this experimental investigation is recommended, as possible deviations from the numerical predictions might be related to repulsive wall bounding forces

Experiences of social support by participants with morbid obesity who participate in conservative rehabilitation program for lifestyle change: a qualitative study

Background: Obesity is a global public health concern with significant implications for physical health and overall well-being. Lifestyle change programs are crucial in addressing obesity and its associated health risks. Social support plays a central role in facilitating successful outcomes in these programs, yet limited qualitative research exists on the experiences of individuals with morbid obesity participating in such interventions. This study aims to explore the social support experiences of participants in a group-based conservative rehabilitation lifestyle change program. Methods: Fourteen participants in a group-based conservative rehabilitation lifestyle change program in Norway, were interviewed using semi-structured interviews. Data were analyzed thematically. Results: Thematic analysis revealed three primary sources of social support: support from other participants in the group, social support from family and friends, and support from the interdisciplinary team. Participants emphasized the significance of ongoing social support throughout their lifestyle change program. Findings highlight the importance of fostering a sense of community and facilitating regular interaction among participants to sustain social support. Conclusions: Future studies should focus on long-term interventions, tailored approaches for diverse needs, involving family and friends and exploring the impact of enhanced peer support. By understanding the role of social support in lifestyle change programs, interventions can be optimized to better support individuals with morbid obesity. Bakgrunn: Fedme er et globalt folkehelseproblem som har betydelige konsekvenser for fysisk helse og livskvalitet. Livsstilsendringsprogrammer kan ha en avgjørende rolle for varige livsstilsendringer, fedme og relaterte helseproblemer. Sosial støtte spiller en viktig rolle i å oppnå vellykkede resultater i slike programmer, men det eksisterer begrenset kvalitativ forskning som undersøker erfaringene til personer med sykelig fedme som deltar i slike tiltak. Denne studien har som mål å undersøke opplevelsen av sosial støtte hos deltakere med sykelig overvekt som deltar i et (konservativt) rehabiliteringsopplegg for livsstilsendring. Metode: Fjorten deltakere i et gruppebasert konservativt rehabiliterings program i Norge ble intervjuet ved bruk av semistrukturerte intervjuer. Tematisk analyse ble benyttet som analysemetode. Resultater: Våre funn viser at deltakerne opplevde sosial støtte fra hovedsakelig tre kilder: støtte fra andre deltakere i gruppen, sosial støtte fra familie og venner, og støtte fra det tverrfaglige teamet. Deltakerne understreket betydningen av kontinuerlig sosial støtte gjennom hele livsstilsendringsprogrammet. Resultatene fremhever viktigheten av å fremme en følelse av fellesskap og legge til rette for jevnlige møtepunkter for deltakerne for å opprettholde sosial støtte. Konklusjon: Fremtidige studier bør fokusere på langsiktige tiltak, skreddersydde tilnærminger for ulike behov, involvering av familie og venner, og utforske effekten av forbedret støtte fra jevnaldrende. Ved å forstå rollen sosial støtte spiller i livsstilsendringsprogrammer, kan tiltakene optimaliseres for å bedre støtte personer med sykelig fedme.publishedVersio

The linear decision rule approach applied to the hydrothermal generation planning problem

We use the linear decision rule approach to develop a model for a stochastic multi-stage generation planning problem in the Nordic region. By developing both the primal and the dual versions of the program, the loss of optimality incurred by the linear decision rule approach can be estimated. Uncertain parameters take values in an uncertainty set defined by upper and lower bounds. Alternative modelling methods for stochastic problems of comparable size and structure either suffer from the curse of dimensionality, or have to rely on unrealistic simplifying assumptions to achieve tractability. We show that the linear decision rule approach gives a good trade-off between tractability and accuracy for a stochastic generation planning problem

Rapid genotyping of the human renin (REN) gene by the LightCycler® instrument: Identification of unexpected nucleotide substitutions within the selected hybridization probe area

Preeclampsia is a serious disorder affecting nearly 3% of all in the Western world. It is associated with hypertension and proteinuria, and several lines of evidence suggest that the renin-angiotensin system (RAS) may be involved in the development of hypertension at different stages of a preeclamptic pregnancy. In this study, we developed rapid genotyping assays on the LightCycler® instrument to allow the detection of genetic variants in the renin gene (REN) that may predispose to preeclampsia. The method is based on real-time PCR and allele-specific hybridization probes, followed by fluorescent melting curve analysis to expose a change in melting temperature (Tm). Ninety-two mother-father-child triads (n=276) from preeclamptic pregnancies were genotyped for three haplotype-tagging single nucleotide polymorphisms (htSNPs) in REN. All three htSNPs (rs5705, rs1464816 and rs3795575) were successfully genotyped. Furthermore, two unexpected nucleotide substitutions (rs11571084 and rs61757041) were identified within the selected hybridization probe area of rs1464816 and rs3795575 due to aberrant melting peaks. In conclusion, genotyping on the LightCycler® instrument proved to be rapid and highly reproducible. The ability to uncover additional nucleotide substitutions is particularly important in that it allows the identification of potentially etiological variants that might otherwise be overlooked by other genotyping methods.publishedVersio

Challenges with onboard strain measurements on a model Francis turbine runner

As the world transitions towards more renewable energy sources, as a step to reduce the emissions of CO2, intermittent and non-dispatchable sources like solar and wind will take up a larger proportion of the energy production. With more unregulated power in the energy mix, a higher demand is put on the rest of the energy production system. Hydropower is in a unique position as it is both renewable and a highly flexible energy source. The increased use of flexible operation of Francis turbines especially, puts a higher dynamic load on the runner components which as a consequence leads to a reduced lifetime. In this paper we present the experimental setup and results from a measurement campaign performed on a model of a low specific speed Francis runner. Onboard measurements with strain gauges at the trailing edge of two runner blades were performed. The experiments were conducted as a part of the HydroFlex project with the goal of validating numerical simulations and to gain a better understanding of the reduction of lifetime on Francis turbines due to higher fatigue loading from more flexible operation. The results shows that there were a significant drift of the mean strain over time during the measurement campaign, and a lower measured strain at BEP than expected when compared to numerical simulations. In this paper, the experimental setup, results and challenges encountered are presented.publishedVersio

Modeling, Identification and Control at Telemark University College

Master studies in process automation started in 1989 at what soon became Telemark University College, and the 20 year anniversary marks the start of our own PhD degree in Process, Energy and Automation Engineering. The paper gives an overview of research activities related to control engineering at Department of Electrical Engineering, Information Technology and Cybernetics

Maternal angiotensinogen (AGT) haplotypes, fetal renin (REN) haplotypes and risk of preeclampsia; estimation of gene-gene interaction from family-triad data

Background Preeclampsia is a debilitating disorder affecting approximately 3% of pregnant women in the Western world. Although inconclusive, current evidence suggests that the renin-angiotensin system may be involved in hypertension. Therefore, our objective was to determine whether the genes for placental renin (REN) and maternal angiotensinogen (AGT) interact to influence the risk of preeclampsia. Methods Three haplotype-tagging SNPs (htSNPs) covering REN (rs5705, rs1464818, and rs3795575) and another three covering AGT (rs2148582, rs2478545 and rs943580) were genotyped in 99 mother-father-child triads of preeclampsia pregnancies. We estimated relative risks (RR) conferred by maternal AGT and fetal REN haplotypes using HAPLIN, a statistical software designed to detect multi-marker transmission distortion among triads. To assess a combined effect of maternal AGT and fetal REN haplotypes, the preeclamptic triads were first stratified by presence/absence of maternal AGT haplotype C-T-A and tested for an effect of fetal REN across these strata. Results We found evidence that mothers carrying the most frequent AGT haplotype, C-T-A, had a reduced risk of preeclampsia (RR of 0.4, 95% CI = 0.2-0.8 for heterozygotes and 0.6, 95% CI = 0.2-1.5 for homozygotes). Mothers homozygous for AGT haplotypes t-c-g and C-c-g appeared to have a higher risk, but only the former was statistically significant. We found only weak evidence of an overall effect of fetal REN haplotypes and no support for our hypothesis that an effect of REN depended on whether the mother carried the C-T-A haplotype of AGT (p = 0.33). Conclusion Our findings indicate that the mother's AGT haplotypes affect her risk for developing preeclampsia. However, this risk is not influenced by fetal REN haplotypes.publishedVersio