Using the classical molecular dynamics simulations, the interfacial partitioning of selected aromatic species, namely benzoic acid and neutral and zwitterionic form of L-phenylalanine, was studied in the three slab systems: a) aqueous organics solution, b) palmitic acid monolayer in tilted condensed phase at aqueous organics solution and c) palmitic acid monolayer in tilted condensed - 2D gas phase coexistence at aqueous organics solution. The surface activity and the tendency to aggregate in particular at the air- aqueous and palmitic acid-aqueous interface was confirmed for all of the investigated aromatic species. The results of the simulation performed for the system of palmitic acid monolayer at benzoic acid solution were compared with the literature results of a similar simulation that employed a different parametrization. The comparison showed that the behaviour of the aromatic species at the fatty acid monolayer-aqueous interface strongly depends on the force field. The structural properties of the palmitic acid Langmuir monolayers were evaluated by means of the chain tilt angle and the headgroup region dihedral angle distributions analysis depending on the surface film density and the adsorbed aromatic species. The simulations mimicking the isothermal compression of the mixed monolayer in the...

Since the industrial evolution, the CO2-levels have been increasing in a way that’s never seen in the history of the earth. To mitigate and adapt to the happening climate change it is really important to understand the global carbon cycle and each component that plays a role in it. Some studies suggest that there has been an underestimation on the influence from inland waters in the total carbon budget.To address this issue, there has been Eddy Covariance measurements going on the boreal Indalsälven river in front of the Kattstrupeforsen water dam. In this study continuous data has been collected which includes air-river CO2-flux, pCO2-values in the air and the water and some more meteorological parameters such as the wind speed, relative humidity and the air and water temperature. The aim of this study is to look into the seasonal variation in pCO2-levels and the CO2-fluxes on the Indalsälven river.The data indicates that the CO2-fluxes are mainly positive from January till July (average flux = 0.2 μmol m-2s-1) and mainly negative from September till November (average flux = -0.59 μmol m-2s-1) with an average flux of 0.212 μmol m-2s-1 during 2019. The main range of CO2-fluxes per month lies between -2 and 2 μmol m-2s-1, with the exception of March and December where there is a bigger range of fluxes. The pCO2-levels in the water mainly range between 400 and 1000 ppm. With the exception of 2 periods, one in the end of May where there is a peak to 4000ppm and more which can be explained by the spring flood and in the end of July and beginning of August where there is a peak to 3000 ppm. / <p>2020-06-17</p>

Två olika värmesystem i två flerbostadshus har analyserats. Målet med analysen är att få en uppfattning om vilket värmesystem som är mest fördelaktigt i flerbostadshus. I analysen jämförs två olika värmesystem. I värmesystemen används två olika sorters frånluftsvärmepumpar för att återvinna värme ur frånluften. När värmepumparna inte klarar av att producera tillräckligt med värme för att täcka fastighetens värmebehov används fjärrvärme som spetsning. Värmepumparna är fastighetens huvudvärmekälla. I den ena fastigheten, Gäddan 1, används en luft-vatten frånluftvärmepump. Kylbatteriet som finns i frånluftsvärmepumpen är placerat i frånluftkammaren. Den andra fastigheten, Gäddan 2, använder sig av två utomhusvärmepumpar. Dessa två är placerade i en frånluftskammare för att kunna återvinna den varma luften.  Under analysen har en sammanställning av egna mätningar och prognoser tagits fram ur en mätningsperiod på tre veckor. I analysen jämförs de olika värmesystemen utifrån tre olika faktorer; energi, miljö och ekonomi. De parametrar som beräknats är värmefaktor (COP), energiförbrukning (kWh), livscykelkostnad (LCC), återbetalningstid (år) och kostnad för producerad värmeenergi (kr/kWh). Resultaten utgår från statistiken och jämförs mellan varandra. Resultatet av analysen visar att värmesystemet i fastigheten Gäddan 1 är mest fördelaktig enligt de metoder som har använts som berör både energi och ekonomi.  Det resultat som visats är att Gäddan 1 har 20 % högre värmefaktor, 12 % lägre driftskostnad och 50 % snabbare återbetalningstid för värmesystemet. Dock har värmesystemet 36 % högre koldioxidsutsläpp under systemets levnadslängd, som är baserat på 20 år.  I slutsatsen kan fastigheternas storlek påverka resultaten. Gäddan 1 är en större byggnad och har fler lägenheter jämfört med Gäddan 2. Detta påverkar förbrukningen av fjärrvärme i värmesystemen som ökar koldioxidsutsläppen, vilket kan vara en bidragande faktor till att Gäddan 1 har högre koldioxidsutsläpps resultat (36 %) än Gäddan 2. / Two different heating systems in two apartment buildings have been analyzed. The goal of this analysis is to get an idea of which heating system is most beneficial in apartment buildings. The analysis compares two different heating systems. Two different kinds of exhaust air heat pumps are used to recover heat from exhaust air. When heat pumps are unable to produce enough heat to cover the heating demand of the buildings, district heating is used. The heat pumps are the property's main source of heat. In one property, Gäddan 1, an air-water heat pump is used. The cooling coil located in the exhaust air heat pump is placed in the exhaust chamber. The other property, Gäddan 2, features two outdoor heat pumps. These two pumps are disposed in an exhaust chamber in order to recover the hot air. During analysis, a compilation of measurements and predictions from a measurement period of three weeks has been analyzed in order to calculate the various parameters. The analysis compares the different heating systems based on three different factors including energy, environment and economy. The parameters that are calculated are the coefficient of performance (COP), energy consumption (kWh), life cycle cost (LCC), payback period (years) and cost of the produced thermal energy (SEK / kWh). The results are based on statistics and compared between each other. The result of the analysis shows that the heating system in the property Gäddan 1 is the most beneficial, according to the methods used concerning both energy and economy. The result shows that Gäddan 1 has a 20 % higher coefficient of performance, 12 % lower operating cost and 50 % faster payback time for the heating system. However, this heating system has 36 % higher carbon dioxide emissions during its life span, which is based on 20 years. In conclusion the properties size may also affect the results. Gäddan 1 is a larger building and has more flats than Gäddan 2. This affects the consumption of district heating in the heating systems with increase carbon emissions. This may be a contributing factor to a higher carbon dioxide emission in Gäddan 1 (36 %) compare to Gäddan 2.

Recent reports on the formation of hydrogen peroxide (H$_2$O$_2$) in water microdroplets produced via capillary condensation or pneumatic spraying have garnered significant attention. How covalent bonds in water could break under such conditions challenges our textbook understanding of physical chemistry and the water substance. While there is no definitive answer, it has been speculated that ultrahigh electric fields at the air-water interface are responsible for this chemical transformation. This thesis documents the findings of our exploration of this mystery via a comprehensive experimental investigation of H$_2$O$_2$ formation in (i) water microdroplets condensed on hydrophobic and hydrophilic substrates formed via hot water in the 50–70 ℃ range or ultrasonic humidifier under controlled air composition, and (ii) water microdroplets sprayed over a range of liquid flow-rates, the (shearing) air flow rates, and the air composition. Our glovebox experiments, with controlled gas composition, revealed that no H$_2$O$_2$(aq) was produced in water microdroplets condensed via heating water (detection limit ≥ 0.25 μM), regardless of the droplet size or the substrate wettability. In contrast, water droplets condensed via ultrasonic humidification contained significantly higher (~1 μM) H$_2$O$_2$ concentration. We pinpointed that ultrasonic humidifiers induced cavitation of tiny bubbles in water, which is known to form H$_2$O$_2$(aq) and other reactive species. Next, in the case of sprayed water microdroplets, also, we did not detect H$_2$O$_2$(aq) unless O$_3$(g) was present in the ambient atmosphere. In contrast, water microdroplets (sprayed or condensed) exposed to O$_3$(g) concentration in the range 2–5000 ppb formed 2–100 μM H$_2$O$_2$(aq); increasing the gas–liquid surface area, mixing, and contact duration enhanced the H$_2$O$_2$(aq) concentration. Therefore, we submit that the original reports suffered from experimental artifacts due to the high regional O$_3$(g) giving rise to H$_2$O$_2$(aq), and the air–water interface does not spontaneously produce H$_2$O$_2$(aq). The water surface merely facilitates the O$_3$(g) mass transfer, which then undergoes chemical transformations in the water to form H$_2$O$_2$(aq). Taken together, these findings offer an alternative explanation to the mysterious production of H$_2$O$_2$ in water microdroplets; These findings should also advance our understanding of the implications of this chemistry in natural and applied contexts.

Nuclear power plants rely on the Emergency Core Cooling System (ECCS) to cool down the reactor core in case of an accident. Occasionally, air is entrained into the suction piping of ECCS causing voids that decrease pumping efficiency, and consequently damage the pumps. In an attempt to minimize the amount of voids entering the suction side of the pump in ECCS, a Void Recirculation System (VRS) experiment was conducted for a proof of concept purpose. While many studies have been oriented in studying two-component flow behavior in ECCS, none of them propose a solution to minimize air entrainment. As a consequence, there are no simulation models that use computational fluid dynamics to address gas entrainment solutions in ECCS. The objectives of this thesis are to (1) simulate and investigate two-component air-water flow in a VRS that minimizes the amount of air in piping systems, using RELAP5/MOD3 as the computational tool, and (2) to validate the numerical results with respect to experimental results and observations. A one-dimensional model of the VRS was built in RELAP5, in which eight different scenarios (replicating those from the VRS experiment) were simulated for a period of 150 seconds. Four Froude numbers of 0.8, 1.0, 1.3 and 1.6 were evaluated in two different pipe configurations, and the experimental data obtained from the VRS experiment was used to validate the numerical results obtained from these simulations. It was concluded that air recirculation occurs indefinitely throughout the entire 150 seconds of the simulation for Froude numbers up to 1.3; while for a Froude number of 1.6, air recirculation occurs for approximately 100 seconds and ceases after 125 seconds of the simulation. An average air reduction effectiveness of 90% was found for all simulation scenarios. The VRS model was successfully validated and can be used to investigate the effects of air entrainment in suction piping.

No description available.

Yes / Understanding the dynamic free surface of geophysical flows has the potential to enable direct inference of the flow properties based on measurements of the free surface. An important step is to understand the inherent response of free surfaces in depth-limited flows. Here a model is presented to demonstrate that free surface oscillatory spatial correlation patterns result from individual surface features oscillating vertically as they advect over space and time. Comparison with laboratory observations shows that these oscillating surface features can be unambiguously explained by simple harmonic motion, whereby the oscillation frequency is controlled by the root-mean-square water surface fluctuation, and to a lesser extent the surface tension. This demonstrates that the observed “complex” wave pattern can be simply described as an ensemble of spatially and temporally distributed oscillons. Similarities between the oscillon frequency and estimated frequency of near-bed bursting events suggest that oscillon behaviour is linked with the creation of coherent flow structures.

Polyhedral oligomeric silsesquioxanes (POSS) have attracted substantial academic interest for many years as hybrid materials and nanofillers for controlling thermal and mechanical properties, and providing thermal and chemical resistance while retaining ease of processing. A natural extension of these studies has been POSS-based amphiphiles and thin film coatings. Studies at the air/water (A/W) interface have shown that trisilanol-POSS derivatives are amphiphilic and form uniform Langmuir films, whereas closed-cage POSS derivatives are hydrophobic and aggregate. In previous work, a triester (POSS-triester) and a triacid (POSS-triacid) were synthesized from PSS-(3-hydroxypropyl)-heptaisobutyl (POSS-OH) and Weisocyanate and fully characterized by surface pressure – area per molecule (Π-A) isotherm and Brewster angle microscopy (BAM) studies at the A/W interface. The results indicated that POSS-triester is surface active forming a liquid expanded (LE) monolayer, whereas POSS-triacid forms a liquid condensed (LC) monolayer that is only weakly affected by pH. A face-on conformation was proposed and examined to understand the packing of POSS-based amphiphilic molecules at the A/W interface. The face-on/vertex-on comparison is rarely discussed for Langmuir monolayers at the A/W interface. In this thesis, three other POSS-based esters were synthesized from POSS-OH and aminopropylisobutyl-POSS (POSS-NH₂) using Weisocyanate and a similar isocyanate containing two tert-butyl protected carboxylic acids. The synthesized materials are characterized by Π-A isotherm and BAM. For POSS-OH based diester (PAlDE) and POSS-NH2 based diester (PAmDE), LE/LC phase transitions were observed in Π-A isotherms over part of the experimentally accessible temperature range and were attributed to a change from a vertex-on to face-on conformation. Apparent BAM images confirmed LC islands coexisted with the LE phase. The experimentally observed dynamic estimates of the critical temperatures (Tc) were estimated from a two-dimensional Clausius-Clapeyron analysis and were consistent with the temperature dependence of the Π-A isotherms. These LE/LC phase transitions are the first observed for POSS amphiphiles. / Ph. D.

Polyhedral oligomeric silsesquioxanes (POSS) have attracted substantial academic interest for many years as hybrid materials and nanofillers for controlling thermal and mechanical properties, and for providing thermal and chemical resistance while retaining ease of processing. A natural extension of these studies has been working on POSS-based amphiphiles and thin film coatings. Studies at the air/water (A/W) interface have shown that trisilanol-POSS derivatives are amphiphilic and form uniform Langmuir films, whereas closed-cage POSS derivatives are hydrophobic and aggregate. In this study, two novel POSS derivatives were synthesized from PSS-(3-hydroxypropyl)-heptaisobutyl substituted (POSS-OH) and completely characterized. Weisocyanate reacted with POSS-OH, and a POSS-based triester (POSS-triester) was obtained. Trifluoroacidolysis of the POSS-triester at room temperature afforded the corresponding triacid (POSS-triacid). Purified POSS-OH, POSS-triester, and POSS-triacid were studied by using surface pressure - area per molecule (? -A) isotherms as well as Brewster angle microscopy (BAM) at the air/water (A/W) interface. Compared with previous work on trisilanol-POSS derivatives, the results indicated that POSS-triester was surface active and formed a liquid-expanded (LE) monolayer. In contrast, POSS-triacid monolayers were more condensed (LC) and were not dramatically affected by changes in pH. Results for the lift-off areas (Alift-off), limiting areas (A0), collapse areas (Ac), and collapse pressures (? c) of POSS-OH, POSS-triester, and POSS-triacid were compared to trisilanolisobutyl-POSS (TiBP) and were interpreted in terms of possible molecular conformations. Whereas, TiBP has been hypothesized to exist in a vertex-on conformation, POSS-OH and POSS-triacid packing at the A/W interface was consistent with face-on conformations. For POSS-triester, the isotherm was consistent with a vertex-on conformation at low ? , but a face-on conformation at high ? . / Master of Science

A superhydrophobic coating can be produced using a hydrophobic material textured with surface roughness on the micro-/nano-scale. Such a coating on the outside of a submersible body may result in reduced skin-friction drag due to a trapped layer of air in the coating. However, this layer may become unstable when subjected to elevated hydrostatic pressures, and a coating’s performance is compromised beyond a certain threshold (critical pressure). This thesis presents a numerical model for predicting the pressure tolerances of superhydrophobic coatings comprised of randomly deposited hydrophobic particles or fibers. We have also derived a set of force-balance-based analytical equations for predicting critical pressure in surfaces with ordered roughness, and compared our numerical model against it, observing reasonable agreement. The numerical model was then applied in a large parameter study, predicting critical pressure for coatings with a given set of microstructure properties.