Thermal Fractionation Research Articles

Combined measurement and calibration method for the thermal conductivity of phase change materials

A combined method for determining the thermal conductivity of phase-change materials (PCMs) is proposed in this paper. A primary concern for this method is mitigating the effect of factors that exist in real experiments but are excluded in the measurement model. Thus, a measurement model was proposed to establish the mathematical relationship between the thermal conductivity and liquid fraction during the melting process. An experimental system was developed, and two different PCMs were used for the experiment. The thermal conductivity obtained via the experiments depicted an increasing trend during the entire melting process; these measurements were treated as the effective thermal conductivity of the PCM. The enhanced heat transfer rate prompted by natural convection was identified as the factor that affected the thermal conductivity measurement; a numerical calibration approach was presented to mitigate this influence. The numerical model considered all factors influencing the errors, and thermal conductivities were obtained via repeated iterations. Deviations between the calibrated thermal conductivity and reference data were less than 8%, meeting the practical requirements of engineering applications.

Rewiring of the protein–protein–metabolite interactome during the diauxic shift in yeast

In budding yeast Saccharomyces cerevisiae, the switch from aerobic fermentation to respiratory growth is separated by a period of growth arrest, known as the diauxic shift, accompanied by a significant metabolic rewiring, including the derepression of gluconeogenesis and the establishment of mitochondrial respiration. Previous studies reported hundreds of proteins and tens of metabolites accumulating differentially across the diauxic shift transition. To assess the differences in the protein–protein (PPIs) and protein–metabolite interactions (PMIs) yeast samples harvested in the glucose-utilizing, fermentative phase, ethanol-utilizing and early stationary respiratory phases were analysed using isothermal shift assay (iTSA) and a co-fractionation mass spectrometry approach, PROMIS. Whereas iTSA monitors changes in protein stability and is informative towards protein interaction status, PROMIS uses co-elution to delineate putative PPIs and PMIs. The resulting dataset comprises 1627 proteins and 247 metabolites, hundreds of proteins and tens of metabolites characterized by differential thermal stability and/or fractionation profile, constituting a novel resource to be mined for the regulatory PPIs and PMIs. The examples discussed here include (i) dissociation of the core and regulatory particle of the proteasome in the early stationary phase, (ii) the differential binding of a co-factor pyridoxal phosphate to the enzymes of amino acid metabolism and (iii) the putative, phase-specific interactions between proline-containing dipeptides and enzymes of central carbon metabolism.

Combustion optimization in consolidated porous media for thermo-photovoltaic system application Using Response Surface Methodology

Motivated by the need to optimize the operation of an MTPV system, three consolidated porous media (PM) geometries namely spherical, conical and cylindrical and a non-PM combustor are numerically simulated. The geometry with the best methane conversion rate is identified and optimized with the right porous media and combustor diameter ratio. Using Response Surface Methodology, a design of experiment (DOE) approach is adopted to examine the effects of three independent parameters namely: wall thermal conductivity, chamber radius and O2 mass fraction on output parameters critical to the operation of the MTPV system specifically radiation heat transfer rate and emitter efficiency. Results show that PM combustion produces higher and uniform wall temperatures compared to the non-PM combustor. The spherical shape consolidated PM produces the highest average methane conversion rate of 96.8% and highest mean wall temperature of 1032 K even though it produces the least flame temperature. The highest radiation heat transfer rate predicted by DOE and CFD simulations are 3.25 W and 3.17 W respectively. The best conditions to realize the optimal MTPV performance is by employing the spherical PM combustor with diameter ratio of 0.7, porosity of 0.5, equivalence ratio of 0.8, wall thermal conductivity of 22.99 W/(m∙K).

The Prompt Emission of GRB 130518A and the Study of Its Outflow through Hybrid Jet Models

The nature of the prompt emission mechanism in gamma-ray bursts (GRBs) remains uncertain to date. This question is also tied to the composition of the jet: thermal, Poynting flux dominated or hybrid with both types of components. In this work, we aim to study these questions in the context of GRB 130518A. By analysing its prompt emission data from the Fermi Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT), we find that the time-integrated spectrum has a nonthermal component along with a subdominant blackbody component. We use these results to study the properties of the jet in various scenarios through the frameworks developed by Hascoët et al. and Gao & Zhang. Both frameworks exclude the pure fireball model for this GRB. In all other cases, the initial magnetic fraction is greater than the thermal fraction. For small launching radii of the jet, the favored nonthermal emission process is internal shocks. Magnetic reconnection seems likely only for very large initial radii.

Low-frequency Radio Continuum Imaging and SED Modeling of 11 LIRGs: Radio-only and FUV to Radio Bands

We present a detailed analysis of 11 local luminous infrared galaxies from ultraviolet through far-infrared to radio (∼70 MHz to ∼15 GHz) bands. We derive the astrophysical properties through spectral energy distribution (SED) modeling using the Code Investigating GALaxy Emission (CIGALE) and UltraNest codes. The radio SEDs include our new observations at 325 and 610 MHz from the GMRT and the measurements from public archives. Our main results are (1) radio SEDs show turnovers and bends, (2) the synchrotron spectral index of the fitted radio spectra ranges between −0.5 and −1.7, and (3) the infrared luminosity, dust mass, dust temperature, stellar mass, star formation rates (SFRs), and active galactic nuclei (AGN) fraction obtained from CIGALE fall within the range exhibited by galaxies of the same class. The ratio of 60 μm infrared and 1.4 GHz radio luminosity, the 1.4 GHz thermal fraction, and emission measure range between 2.1 and 2.9, 0.1% and 10%, 0.02 and 269.5 × 106 cm−6 pc, respectively. We conclude that the turnovers seen in the radio SEDs are due to free–free absorption; this is supported by the low AGN fraction derived from the CIGALE analysis. The decomposed 1.4 GHz thermal and nonthermal radio luminosities allowed us to compute the SFR using scaling relations. A positive correlation is observed between the SFRIR obtained 10 Myr ago (compared to 100 Myr ago) and 1.4 GHz radio (total and nonthermal) because similar synchrotron lifetimes are expected for typical magnetic field strengths observed in these galaxies (≈50 μG).

Recent applications of the Successive Self-nucleation and Annealing thermal fractionation technique

Successive Self-nucleation and Annealing (SSA) is a thermal fractionation technique that is performed by Differential Scanning Calorimetry (DSC). The combination of non-isothermal and isothermal steps applied during SSA achieves efficient molecular segregation during polymer crystallization. Such molecular segregation magnifies the effect of defects in polymer chain crystallization, thereby providing information on chain structure. The technique was created and implemented by Müller and co-workers in 1997, becoming a powerful resource for studying ethylene/α-olefin copolymers. The different variables to design the SSA protocol: fractionation window, fractionation time, scanning rate, sample mass, and the first self-nucleation temperature to be applied (Ts, ideal), have been previously reviewed, together with the different applications of SSA. SSA versatility, simplicity (when properly applied), and short times to produce results have allowed its use to study novel and more complex polymeric systems. This review article explores the most recent applications of SSA of the past decade. First, the principles of the technique are briefly explained, covering all the relevant variables. Next, we have selected different cases that show how SSA is employed in various novel fields, such as studying intermolecular interactions and topological effects in homopolymers; supernucleation and antinucleation effects in nanocomposites, including the pre-freezing phenomenon; crystallization modes in random copolymers; solid-solid transitions; miscibility, co-crystallization and composition in blends; evaluation of polymer synthesis variables; and the novel information that could be gained by using fast scanning chip-based calorimetry. Finally, we offer a perspective on SSA, a technique that has become a powerful method for studying the distribution of defects affecting crystallization in semi-crystalline polymers.

Effect of the TrFE Content on the Crystallization and SSA Thermal Fractionation of P(VDF-co-TrFE) Copolymers.

In this contribution, we study the effect of trifluoro ethylene (TrFE) comonomer content (samples with 80/20, 75/25, and 70/30 VDF/TrFE molar ratios were used) on the crystallization in P(VDF-co-TrFE) in comparison with a PVDF (Poly(vinylidene fluoride)) homopolymer. Employing Polarized Light Optical Microscopy (PLOM), the growth rates of spherulites or axialites were determined. Differential Scanning Calorimetry (DSC) was used to determine overall crystallization rates, self-nucleation, and Successive Self-nucleation and Annealing (SSA) thermal fractionation. The ferroelectric character of the samples was explored by polarization measurements. The results indicate that TrFE inclusion can limit the overall crystallization of the copolymer samples, especially for the ones with 20 and 25% TrFE. Self-nucleation measurements in PVDF indicate that the homopolymer can be self-nucleated, exhibiting the classic three Domains. However, the increased nucleation capacity in the copolymers provokes the absence of the self-nucleation Domain II. The PVDF displays a monomodal distribution of thermal fractions after SSA, but the P(VDF-co-TrFE) copolymers do not experience thermal fractionation, apparently due to TrFE incorporation in the PVDF crystals. Finally, the maximum and remnant polarization increases with increasing TrFE content up to a maximum of 25% TrFE content, after which it starts to decrease due to the lower dipole moment of the TrFE defect inclusion within the PVDF crystals.

Physical properties of lacustrine shale oil: A case study on the lower member of the Lucaogou Formation (Jimusaer Sag, Junggar Basin, NW China)

Shale oil generated by the lower member of the Lucaogou Formation, which was deposited under saline lacustrine conditions within the Jimusaer Sag of the Junggar Basin (NW China), is generally characterized by high density and viscosity. However, a strong spatial heterogeneity of physical properties is observed as well. In this paper, these spatial variations and their controlling mechanisms are evaluated from the perspective of the primary depositional environment, source rock thermal evolution and fractionation effects of primary migration. Based on a detailed organic petrological and geochemical characterization of the target interval within the key well JHBE, hydrous pyrolysis experiments conducted on representative source rock samples from well JHBE, as well as established methods of oil-source correlation subjected to oil samples from several regionally distributed producing shale oil wells, a predictive model of density and viscosity changes of crude oil was established. According to the findings of this study, the thermal evolution and sedimentary environment of source rocks are the main factors affecting the quality of crude oil, and the fractionation effect of primary migration has little effect. Crude oil density and viscosity at first increase up to peak oil maturity, followed by a decrease with further increasing thermal evolution of the source rock. Furthermore, if the source rocks experienced similar thermal histories, it was discovered that relatively low density and corresponding viscosity values are characteristic for crudes from source rocks which were formed in a relatively high salinity environment. In contrast, hydrocarbon generation of source rocks formed under relatively low salinity environments is slightly retarded in direct comparison, and the density and viscosity of the generated crude oil are both relatively high. This highlights that a detailed organic petrographical and geochemical evaluation of the target formation is crucial for the assessment of shale oil potential and production sweet spots in alginite-dominated lacustrine sedimentary environments.

Hard block length distribution of thermoplastic polyurethane determined by polymerization-induced phase separation

Three thermoplastic polyurethanes (TPUs) based on the same monomers and composition were produced in bulk by hand and machine casting methods. The soft segment was PTHF® 1000 and the hard segment was made of 1,4-butanediol and 4,4′-methylene diphenyl diisocyanate (MDI). The hard segment content amounted to 30%. The hand cast TPUs were prepared at 80 and 125 °C. The temperature conditions for the machine prepared sample were comparable to that of the hand casting process at 125 °C. The samples prepared at high temperature were transparent, whereas the sample produced at low temperature was translucent. The latter showed some crystallinity and in crystallization studies it crystallized more readily than the transparent samples. The distinctions in transparency and crystallization behavior were ascribed to differences in the hard block length distribution. Using thermal fractionation – a series of successive self-nucleation and annealing steps – the minor differences in hard block length distribution could be shown and quantified. The TPU synthesized at low temperatures possessed the longer hard blocks. These facilitated crystallization by enhancing nucleation and crystal growth. Superstructures, induced by the longer hard blocks, scattered visible light and reduced the transparency.

Numerical simulation of the effect of injection sites arrangement on the thermal ablation in the magnetic fluid hyperthermia

Magnetic hyperthermia ablates malignant cells by the heat-dissipating from magnetic nanoparticles (MNPs) when subjects to an alternate magnetic field. To reveal the heat transfer mechanism for magnetic fluid hyperthermia (MFH) and analyze the effect of injection site arrangement on the temperature distribution during magnetic fluid hyperthermia. A three-dimensional multi-physical model was established to obtain the temperature distribution of the treated tumor tissues, the concentration distribution of magnetic fluid, effective treatment volume (Veff), and thermal damage fraction of the tumor. The treatment temperature distribution for a proposed physical model is predicted by solving Pennes bio-heat transfer equation using the finite element method, in which a heat source in form of a Gaussian distribution is used as the power dissipation of MNPs. The results demonstrate that the size of the heat source has a greater effect on the maximum temperature of the heat source center under a single injection site. Additionally, it found that the effective treatment volume is not the sum of the effective treatment volumes at each injection site for the multisite injections. The effective treatment volume shows a strong nonlinear increase with the number of injection site increases compared with the single injection site. The multisite injection can significantly increase the effective treatment volume during the hyperthermia process and achieve the effect of agglomeration heating. For eight injection sites, the optimal effective treatment volume change rate (εV) reached 94.7%. Additionally, the temperature distribution uniformity of eight injection sites is greatly improved compared with other injection site arrangements under an equal dose. The damage fraction of single site injection from 0.12 up to 0.55 when the magnetic hyperthermia treatment time increases from 0 to 40 min while the damage fraction of eight sites injection from 0.23 up to 0.94. In the clinical treatment process, the distance between the injection sites and the time of magnetic hyperthermia can be reasonably arranged according to the size, shape, and type of the tumor, which not only can obtain a good thermal ablation effect but can effectively reduce the thermal damage to normal tissues.

Gas isotope thermometry in the South Pole and Dome Fuji ice cores provides evidence for seasonal rectification of ice core gas records

Abstract. Gas isotope thermometry using the isotopes of molecular nitrogen and argon has been used extensively to reconstruct past surface temperature change from Greenland ice cores. The gas isotope ratios δ15N and δ40Ar in the ice core are each set by the amount of gravitational and thermal fractionation in the firn. The gravitational component of fractionation is proportional to the firn thickness, and the thermal component is proportional to the temperature difference between the top and bottom of the firn column, which can be related to surface temperature change. Compared to Greenland, Antarctic climate change is typically more gradual and smaller in magnitude, which results in smaller thermal fractionation signals that are harder to detect. This has hampered application of gas isotope thermometry to Antarctic ice cores. Here, we present an analytical method for measuring δ15N and δ40Ar with a precision of 0.002 ‰ per atomic mass unit, a two-fold improvement on previous work. This allows us to reconstruct changes in firn thickness and temperature difference at the South Pole between 30 and 5 kyr BP. We find that variability in firn thickness is controlled in part by changes in snow accumulation rate, which is, in turn, influenced strongly by the along-flowline topography upstream of the ice core site. Variability in our firn temperature difference record cannot be explained by annual-mean processes. We therefore propose that the ice core gas isotopes contain a seasonal bias due to rectification of seasonal signals in the upper firn. The strength of the rectification also appears to be linked to fluctuations in the upstream topography. As further evidence for the existence of rectification, we present new data from the Dome Fuji ice core that are also consistent with a seasonal bias throughout the Holocene. Our findings have important implications for the interpretation of ice core gas records. For example, we show that the effects of upstream topography on ice core records can be significant at flank sites like the South Pole – they are responsible for some of the largest signals in our record. Presumably upstream signals impact other flank-flow ice cores such as EDML, Vostok, and EGRIP similarly. Additionally, future work is required to confirm the existence of seasonal rectification in polar firn, to determine how spatially and temporally widespread rectifier effects are, and to incorporate the relevant physics into firn air models.

Evaluation of organic aerosol filter sampling artefacts and implications to gravimetric PM2.5 mass at a COALESCE network site - Bhopal, India

Filter based PM2.5 samples are typically used to measure its chemical constituents. Such measurements are made in dense sampling networks to assess regulatory compliance and for source apportionment. Thus, quantifying sampling artefacts is crucial. In this study, 24-h integrated PM2.5 samples collected over Bhopal, India a COALESCE (CarbOnaceous AerosoL Emissions, Source apportionment and ClimatE impacts) site during 2019 and 2020, were used to estimate particulate organic carbon (OC) artefacts. Total OC and its thermal fractions (OC1, OC2, OC3, and OC4) measured on 349 bare quartz (Q) and QbQ filters each, were used to determine OC positive artefacts on quartz filters. 50 QbT (Quartz behind Teflon) filters in conjunction with the simultaneous QbQ samples (a subset of the total QbQ) were used to estimate OC volatilization from Teflon filters. On average, adsorbed gaseous OC contributed 17% and 11% to the measured total OC during 2019 and 2020, respectively. Further, the volatilization loss of organics from Teflon filter (used to quantify PM2.5 mass) ranged between 7% and 9%, and 5% and 6% of the PM2.5 mass during 2019 and 2020, respectively. The results of this study provide the first systematic long-term evaluation of thermal carbon fraction-wise sampling artefacts, estimates of organic volatilization losses from Teflon filters and their implications to PM2.5 mass closure, over a regionally representative location in India.

Increasing Efficiency of Contact Devices of Column Mass-Transfer Apparatuses When Using Thermal Fractionation Processes

Increasing Efficiency of Contact Devices of Column Mass-Transfer Apparatuses When Using Thermal Fractionation Processes

Thermal Fractionation of Ethylene/1-Octene Multiblock Copolymers from Chain Shuttling Polymerization

Ethylene/1-octene statistical multiblock copolymers (OMBCs) consisting of the alternation of crystalline, hard blocks and amorphous, soft blocks, with ≈0.5 and 20 mol % of 1-octene units, respectively, are subjected to thermal fractionation resorting to successive self-nucleation and annealing (SSA). The study is extended to random copolymers (RCs) of high (44 kDa) and low (3.4 kDa) number average molecular mass Mn, mimicking in 1-octene content the crystalline hard blocks and to the OMBC fractions extracted in boiling n-hexane and cyclohexane through a suitable solution fractionation protocol. For all the samples, the melting endotherms are well resolved in a multiplicity of peaks corresponding to the melting of crystals of different thicknesses generated in the SSA protocol that reflect the distribution of the methylene sequence length (MSL) in between consecutive interruptions along the chains. It is shown that, regardless of molecular mass, the MSL distributions of the RC samples are shifted toward greater values than those of the OMBC samples, and that also the shapes of the distributions are different. Since the MSL distribution depends on the frequency and distribution of the defects along the chains, and the defects act as interruption points, the higher fraction of long crystallizable sequences in the RC samples suggests that whereas for the RC samples the interruptions are merely represented by the 1-octene units that are rejected outside the crystals, for the OMBCs, the interruption of the regular methylene sequences belonging to the crystalline hard blocks due to the amorphous soft blocks linked to them should also play a role. Indeed, due to the partial miscibility of the hard and soft blocks, the hard blocks of major length tend to crystallize in a confined environment. This prevents the formation of thicker crystals and induces decrease of the MSL values as well as changes in the shape of the MSL distributions (topological confinement). On the other hand, the hard blocks of shorter length tend to crystallize, crossing the hard block rich regions and causing melting point depression and consequent shift of the MSLs toward lower values with respect to RCs (diluent effect). It is shown that differences in the MSL distribution of OMBCs are the result of the interplay between topological confinement and diluent effect, which in turn reflects differences in the OMBC chain microstructure, that is, differences in the distribution of block length at the inter- and intra-chain level.

Comparative study on coal blending and coke-making property of two kinds of thermal dissolution soluble fractions from lignite and coking coal

Thermal dissolutions (TDs) of Xilinguole lignite (XL) and coking coal (CC) with different solvents were performed, and feasibility of applying TD soluble fractions (TDSFs) to coke-making was evaluated. The results show that the TDSFs yield of XL (< 30%) is lower than that of CC (> 40%) in both polar and non-polar solvents at 360 °C. Methanol remarkably enhances TDSF yield of XL from 30% to 45.3% with 10% addition to 1-methylnaphthalene (1-MN) due to methanolysis. All TDSFs prepared show better caking property, lower softening temperatures, and greater caking indexes (GR.I) than the commonly used fat coals for coke-making. Using 5 wt.% TDSFs to substitute equivalent amount of fat coal in coal blends effectively improves the quality of the resultant coke, verifying the feasibility of using TDSFs from low rank coals for coke-making.

The Influence of Annealing Temperature on the Morphology of Structures and the Mechanical Properties of Prequenching-Quenching and Partitioning Steel.

In this study, we comparatively study the microstructures and mechanical properties of prequenching—quenching and partitioning (QQ&P) and traditional Q&P samples at different annealing temperatures (intercritical annealing temperatures). When the annealing temperature is 780 °C, the ferrite and retained austenite in QQ&P samples with lath and blocky morphologies. The lath retained austenite is mainly distributed along the lath ferrite. As the annealing temperature increases, the lath ferrite recrystallizes and gradually grows into the blocky (equiaxed) shape, leading to a decrease in the lath retained austenite content. When the annealing temperature increases to 870 °C, the ferrite content decreases significantly, and the retained austenite is mainly blocky and thin film, distributed at the boundaries of prior austenite grains and between martensite laths, respectively. Different from QQ&P samples, the ferrite and retained austenite in Q&P samples are mainly blocky when the annealing temperature is 780 °C or 810 °C. When the annealing temperature is increased to 870 °C, the microstructures of the Q&P sample are basically the same as that of the QQ&P sample. The 780 °C-QQ&P sample and the 810 °C-QQ&P sample have higher total elongation and product of strength and elongations (PSEs) than their counterpart Q&P samples due to the fact that lath ferrite and retained austenite are conducive to carbon diffusion and carbon homogenization in austenite grains, thereby improving the thermal stability and volume fraction of the retained austenite. In addition, the lath structures can release local stress concentration and delay the formation of voids and microcracks. The difference of mechanical properties between QQ&P samples and Q&P samples decreases with the increase in the annealing temperature. The results show that the low annealing temperature combined with prequenching—Q&P heat treatments can significantly improve the elongation and PSE of Q&P steel.

Dynamic recrystallisation behaviour of deformed austenite of Ti-Zr microalloyed low carbon steel with different Zr content

ABSTRACT In this paper, the dynamic recrystallisation (DRX) behaviour under the strain rate of 0.1 s−1, 1 s−1 and 10 s−1 within the deformation temperature of 900°C∼1100°C of Ti-Zr microalloyed low carbon steel with different Zr content was studied using Gleeble-3800 thermal simulation test machine. The stress–strain curves of investigated steels were obtained under the diferent deformation conditions, and the thermal deformation equation and DRX volume fraction model are established based on the stress–strain curve. The result showed that the peak stress, critical stress and deformation activation energy (496.2 kJ mol−1) of the Ti-Zr steel containing 0.091 wt% Zr were higher than those of the steels with 0.035 and 0.073 wt% Zr. The increase of Zr content will increase the deformation activation energy of Ti-Zr steel and inhibit the growth of austenite DRX grains of Ti-Zr steel at high temperature. When the deformation conditions are the same, the DRX degree of austenite of Ti-Zr steel will first decrease and then increase with the increase of Zr content.

Heat Transfer By Natural Convection from a Heated Square Inner Cylinder to Its Elliptical Outer Enclosure Utilizing Nanofluids

In this paper a numerical study of natural convection of stationary laminar heat transfers in a horizontal ring between a heated square inner cylinder and a cold elliptical outer cylinder is presented. A Cu-water nanofluid flows through this annular space. Different values of the Rayleigh number and volume fraction of nanoparticles are studied. The system of equations governing the problem was solved numerically by the fluent calculation code based on the finite volume method and on the Boussinesq approximation. The interior and exterior surfaces are kept at constant temperature. The study is carried out for Rayleigh numbers ranging from &lt;i&gt;103&lt;/i&gt; to &lt;i&gt;105&lt;/i&gt;. We have studied the effects of different Rayleigh numbers and volume fraction of nanoparticles on natural convection. The results are presented as isotherms, isocurrents, and local and mean Nusselt numbers. The aim of this study is to study the influence of the thermal Rayleigh number and volume fraction of nanoparticles on the heat transfer rate.

Composition, hydrogen bonding and viscoelastic properties correlation for ethylene/α,ω-alkenol copolymers

The influence of composition of ethylene/ α,ω -alkenol ( α,ω -alkenol = 10-undecen-1-ol or 9-decen-1-ol) copolymers on comonomer distribution and dynamic rheological properties were investigated. Thermal fractionation revealed formation of multiple peaks corresponding to the presence of methylene sequences of different length in copolymers. The share of fraction with shorter methylene sequence increased with increasing comonomer content. It turned out that viscoelastic behavior of ethylene/ α,ω -alkenol copolymers was dependent on comonomer content incorporated into the polymer chain. The relaxation time of reptation increased with increasing comonomer content what confirmed that comonomer units acted as physically crosslinking agent. FT-IR investigation proved the appearance of inter- and intramolecular hydrogen bonds in ethylene copolymers with α,ω -alkenols. Higher relative content of inter- and intramolecular hydrogen bonds was observed in α,ω -alkenol with a longer hydrocarbon chain. In addition, activation energy of flow increased with increasing of the comonomer content. Moreover, incorporation of α,ω -alkenols into the polymer chain resulted in a decrease of the packing length of copolymers with increasing comonomer content, what proved that the inter- and intramolecular hydrogen bond played a significant role in viscoelastic properties. • Amount of α,ω -alkenol incorporated in copolymers affected comonomer distribution. • The content of α,ω -alkenol played a key role in rheological behavior of copolymers. • The FT-IR study showed the presence of hydrogen bonds in E/ α,ω -alkenol copolymers. • The effect of hydrogen bonding is dependent on structure of α,ω -alkenol comonomer.

Performance comparison of two water pit thermal energy storage (PTES) systems using energy, exergy, and stratification indicators

Water pit thermal energy storage systems have been demonstrated in Denmark and have proven effective in increasing the solar thermal fractions of district heating systems and in covering the mismatch between heat demand and production. This study analyzed five years of measurement data for two PTES systems in Denmark, namely Marstal and Dronninglund. Their efficiency was assessed using energy, exergy, and a seasonal efficiency indicator. The degree of stratification was investigated using the MIX number, the stratification coefficient, and a newly-introduced indicator, exergy destruction. Exergy destruction was shown to be a promising indicator for assessing stratification since it can be used to compare PTES systems with different heat losses, providing a quantitative evaluation of the amount of mixing. In addition, the seasonal efficiency was found to be suitable for estimating the long-term efficiency of combined seasonal and short-term storage systems. The storage in Dronninglund had 92% energy and 73% exergy efficiency, while Marstal had 63% energy and 48% exergy efficiency. All stratification and efficiency indicators showed that the storage in Dronninglund performed better overall than the one in Marstal.