Search

This study analyses the impact of varying temperature and salinity stratifications on the thermal characteristics of the wake through a newly established simulation model, the reliability of which is confirmed by experimental validation. In a stratified environment with sTable positive salinity but a temperature changing from positive to negative, the wake has "cold" and "hot" characteristics at the free liquid surface, respectively, and these characteristics are enhanced with an increase in the temperature gradient. In a stratified environment with a sTable positive temperature but changing positive salinity, the wake stream has "cold" characteristics at the free liquid surface, and the feature intensity has a weak positive correlation with the salinity gradient. In general, under the boundary and initial conditions studied in this paper, temperature stratification is the main factor determining the thermal characteristics of the free surface, and salinity stratification is the secondary factor. The influence of the moving induced wake on the thermal characteristics of the wake is stronger than that of the buoyant jet. In a follow-up study, we will focus on a scale analysis of the impact of stratified features on the wake, and scale extrapolation. The influence of the free surface thermal boundary layer on the wake characteristics will be another key point for investigation. [ABSTRACT FROM AUTHOR]

Two large-scale snow and rain weather processes occurred in china from February 1-4, 2024 (Process 1, hereinafter), and February 19-24, 2024 (Process 2, hereinafter). During these two weather processes, the impact of freezing rain was extensive, the intensity of the disaster was severe, and the duration was long, which was rare in history. This study utilized multi-source observational data and ERA5 reanalysis data to focus on analyzing the environmental conditions and temperature layer characteristics of these two freezing rain events. The results indicate: (1) During both weather events, the 500 hPa weather patterns and influencing systems were quite similar, which were stably sustained, providing favorable conditions for widespread snow, rain, and freezing weather. However, there were differences in the low-level temperature configuration and the speed of movement. In Process 1, due to the slower movement of the cold air, the distribution of freezing rain was more concentrated. The initial southwest jet stream in Process 2 was stronger and positioned further north compared to Process 1, leading to the occurrence of freezing rain further northward. However, in the later stages, the rapid southward movement of strong cold air caused a fast-moving rain, snow, and ice, and thus a larger impacting range of the freezing rain. (2) In both processes, the mid-level warm layer was mainly located between 700 hPa and 850 hPa, while the low-level cold layer was mainly located below 900 hPa. The positions were lower than the classic conceptual model of a warm layer at 700 hPa and a cold layer at 850 hPa, which could easily lead to misjudgment of the weather situations and types. (3) Using the area method, the strength of the mid-level warm layer and the low-level cold layer was calculated separately for both processes. The results show that the strength of the warm and cold layers in Process 1 was weaker than in Process 2. In addition, the freezing rain in both processes mainly occurred in areas where the strength of the mid-level warm layer and the low-level cold layer were close.

End-gas auto-ignition leading to knocking combustion is one of the major barriers to achieving higher thermal efficiencies in downsized boosted spark-ignition engines. Despite the available framework addressing hotspot-induced ignition (detonation peninsula), a quantitative investigation on hotspot-induced auto-ignition of gasoline surrogates is yet to be done. In particular, the effect of negative temperature coefficient (NTC) chemistry on the distribution of the ignition modes in the detonation peninsula is still missing. Using the established one-dimensional (1D) theoretical and computational framework, the effect of average temperature (including NTC range), initial pressure, and ethanol addition are investigated. Moreover, appearance of NTC chemistry-related events i.e. coolspots, secondary ignition kernels, and off-centered ignition are analyzed using 1D simulations. The results are as follows. 1) NTC chemistry affects the distribution of ignition regimes in detonation peninsula and the dynamics of the front propagation via altering the reactivity gradient. 2) NTC chemistry increases the temperature gradient range associated with the detonation regime. 3) NTC may inhibit detonation development by simultaneously promoting the spontaneous/supersonic ignition modes. 4) An ethanol blend decreases the knock propensity; however, lower ignitability may promote detonation development and the appearance of strong shock waves. 5) Finally, detonation may result in a normal knock at lower initial pressures (20 bar). However, at elevated initial pressures (50 bar), detonation is noted to yield pressure intensities resembling super-knock. [ABSTRACT FROM AUTHOR]

This study investigates Williamson fluid with stratification aspects through an inclined medium with radiative effects and with consideration of transversally applied magnetic field. Additionally, the study involves novel contribution of thermal generating source and chemically reactive species. Modelling is conceded by incorporating conservation laws in view of ordinary differential setup after employing similar variables. Afterwards, numerical simulations through shooting and Rk-4 procedures are executed to inspect the behavior of flow and thermosolutal distributions versus variation in key parameters. Subsequently, the collected data is evaluated by utilizing a multilayer perceptron-based ANN model. The input data for the heat flux, corresponding to different fluid model parameters, is trained by employing Levenberg-Marquardt paradigm and validated against numerical experiment results. The precision of the predicted data is assessed by calculating the mean squared error, determination coefficient and error rating scale. The magnitude of heat flux coefficient elevates up to 15 % in the existence of radiation effect, while depreciates up to 6 % in the presence of stratification effect. The implementation of ANN model depicts a mean square error value 1.36×10−3 when no heat source, which rises to 1.41×10−2 when a heat source is present. From small values of mean squared error for testing, training and validation estimated for Nusselt number ensures the performance of developed ANN network.

Introduction. The influence of atrium on temperature stratification under indoor natural ventilation of the teaching-laboratory building of the Moscow State University of Civil Engineering (MGSU) with the help of full-scale experiments is considered. Based on this, the aim of the research is to develop a new method of calculating the optimal geometric parameters of a building atrium considering the comfort of its temperature-air regime by solving the developed basic airflow equations in combination with mathematical modelling methods. The formula for determining the air flow rate for natural ventilation in atriums, analyzing and designing a natural ventilation system in a building with an atrium with more than two ventilation outlets was derived. Based on the results obtained, a conclusion is made about the optimal area of exhaust and supply openings in an atrium building at different heights. These data may have practical application in the design of buildings with atriums.Materials and methods. Semi-empirical research methods were used. Simple linear regression methods were carried out to establish a correlation between the measured variables air temperature and building construction height in an atrium with specific conditions to determine the temperature at any height.Results. The formula for calculating the optimal area of inlet and outlet openings in connection with the atrium height and their influence on the thermal characteristics of the structures of buildings with atriums was developed.Conclusions. The results of the research make it possible to quickly and accurately determine the geometric parameters to ensure the reduction of air temperature in buildings with atriums. This plays an important role in the initial design phase.

The temperature regime of river systems is influenced by seasonal temperature stratification in reservoirs and climate change. The release of cold water from reservoirs can affect river temperature, with a decrease in river temperature during warm periods and an increase in river temperature during winter. However, warmer air temperatures and increased solar radiation may reduce the influence of reservoirs on downstream temperatures in the future. The cooling potential of reservoirs remains strong for river reaches downstream of reservoirs with strong temperature stratification. The study analyzed air temperature trends at two climate stations, Boľkovce and Málinec, over different time periods. Data on the temperature of the water were collected from a number of stations located above the reservoirs: Smolná I and Smolná II and Málinec, and several stations below the reservoir, namely Málinec, Kalinovo, Holiša and Slovenské Ďarmoty downstream of the Ipeľ River. The Málinec Reservoir, which regulates the upper part of the Ipeľ River and serves as a drinking water reservoir, was built in 1986-1993 and put into operation in 1994. The analysis was divided into two parts. The first part analyzed data from stations with time series before the construction of Málinec reservoir, while the second part analyzed data from stations with time series after the construction of the reservoir. Increasing water temperatures were observed throughout the year, while increasing air temperatures were significant in warm months. The influence of the reservoir can be seen in the slight change of the mean monthly temperatures. The mean temperature decreases in the summer months and increases in the winter months in the period after the construction of the reservoir. [ABSTRACT FROM AUTHOR]

Thermal stratification may switch the combustion mode from deflagration to spontaneous (auto-ignition) in spark-ignition engines leading to knock. Despite the available numerical and experimental works, an analytical and systematic method on the role of local thermal stratification on the combustion mode is still missing. Particularly, the effects of heat diffusion before ignition in negative temperature coefficient (NTC) chemistry of gasoline surrogates are typically ignored. In this study, an a-priori diagnostics tool is provided to separate the deflagration and auto-ignition combustion modes by considering the diffusion effects, based on two parameters: stratification wavelength ( λ) and amplitude ( δ). The diagnostics tool is an extension of Zeldovich's theory to transient problems by solving the diffusion equation and considering the flame and ignition timescales. It is found that 1) The theory is valid against one-dimensional numerical simulations under different average temperatures and pressures. 2) NTC chemistry promotes spontaneous ignition at both low and high pressures. 3) In the presence of NTC chemistry, the transition region between the two combustion modes is broadened. A third blended mode is observed (spontaneous ignition assisted flame) with front speeds ≈ 6 S l . 4) Finally, estimation of the knock propensity from the generated maps is related to the surrogates' octane sensitivities. [ABSTRACT FROM AUTHOR]

It is necessary to satisfy the flexible requirements of solar heat storage systems to provide efficient heating and constant-temperature domestic hot water at different periods. A novel heat storage tank with both stratified and mixing functions is proposed, which can realize the integration of stable stratification and rapid mixing modes. In this research, a three-dimensional heat transfer model of the heat storage tank with stratified and mixed dual modes was established, and a thermal performance test system for the tank was built in the State Key Laboratory of Green Building in Western China. Moreover, a new evaluation index representing the mixing speed is proposed. The stratification effect and mixing characteristics of the tank were studied under different comprehensive conditions. The results show that the exergy efficiency of the tank with a stratified pipe can be increased by 10%–15% compared to that of a conventional tank. Additionally, the recommended optimal flow rate range for well-stratified tanks is 4–6 L/min. The mixing nozzle of the tank reduces the mixing reaction coefficient by 0.27 and significantly reduces the mixing time. This study provides critical guidance to meet the flexible thermal needs of users and implement high-performance applications using the stratified and mixing modes of heat storage tanks. [ABSTRACT FROM AUTHOR]

The mature seed of Paris polyphylla var. chinensis (PPC) is morphophysiologically dormant and develops differently under warm and cold temperatures. To elucidate the molecular mechanisms underlying temperature-dependent regulation of PPC seed dormancy and germination, we investigated the dynamic changes in PPC seed transcript levels under warm and cold temperature stratifications (WS and CS, respectively) by time-resolved RNA sequencing, focusing on genes related to hormone metabolism and signaling and cell wall remodeling (CWRM) and encoding transcription factors/regulators (TFs/TRs). A total of 48 765 and 47 836 differentially expressed genes (DEGs) were associated with WS and CS, respectively. Of these, 17 581 and 16 652 DEGs, respectively, unique to WS and CS, and 5 386 were common to both temperature stratifications across nine analyzed growth stages. The expression of hormone metabolism and signaling, TF/TR, and CWRM genes were closely associated with temperature. More genes related to gibberellin (GA), cytokinin, auxin, and brassinosteroid biosynthetic were upregulated in WS as compared to CS seeds, while genes related to dormancy release and germination were downregulated in WS seeds. However, only GA and abscisic acid levels were altered in PPC seeds breaking morphophysiological dormancy (MPD). Overall, 37 TF and five TR families were upregulated whereas 24 TF and 16 TR families were downregulated in WS as compared to CS seeds. Most CWRM families were highly expressed under WS as compared to CS, suggesting that they promote endosperm weakening and embryo growth of WS seeds and facilitate MPD release and germination. A coexpression analysis revealed positive correlations between TFs/TRs and DEGs involved in hormone metabolism and signaling and CWRM. These results provided a basis for investigating the interaction between the endosperm and underdeveloped embryo in the regulation of PPC seed germination and seedling emergence. [ABSTRACT FROM AUTHOR]

The application of ammonia (NH3) in combustion devices, such as internal combustion engines (ICEs), is expected to largely reduce the greenhouse gas (CO2) emission. NH3/H2 cofiring fuels in homogeneous charge compression ignition (HCCI) engines may provide a potential way to deal with zero carbon requirements. However, in HCCI engines, the ignition process needs to be moderated since the ignition is only controlled by the chemical kinetics of the fuel. Therefore, this study investigates the effects of temperature and composition stratification strategies on the auto-ignition characteristics of NH3/H2/air mixtures under HCCI engine operating conditions with direct numerical simulation (DNS). 12 cases with different stratification strategies have been set under turbulent conditions. The chemical kinetics of NH3/H2/air was verified with the laminar flame speeds and ignition delay times. Results show that the temperature stratification can reduce the peak value of heat release rate (HRR), advance the ignition time and extend the combustion duration. In this case, the chemical reaction front is dominated by the deflagration or flame propagation mode. However, in contrast, composition stratification shows very limited effect on the overall combustion process, which is similar to homogeneous ignition and denoted as the spontaneous ignition mode. When increasing the hydrogen content in the fuel, the ignition time is obviously advanced and the peak of HRR is slightly increased. Higher NO emission is also observed which is mainly due to the increase of O, H, and OH intermediates to enhance the fuel NO production. Temperature stratification degree can improve the ignition process under both negatively correlated or unrelated T-Φ fields. However, the improvement is more evident for unrelated T-Φ condition when increasing the stratification degree.

The results of an experimental study of the effect of reducing the adiabatic wall temperature (aerodynamic cooling) for a case of separated supersonic flow behind a backward-facing ledge are presented. The study was conducted on an unsteady-state regime during the launching of a wind tunnel before reaching the equilibrium thermal state. The parameters of thermal gas dynamics were compared with the results for the case of continuous flow around the smooth wall. The free-stream Mach number was 2.2 and the Reynolds number along the length of the dynamic boundary layer was at least 20 million at the nozzle exit section. The height of the step ranged from 8 to 12 mm. The graphs of the wall temperature, stagnation flow temperature, adiabatic wall temperature, the total and static pressure, the heat flux, the distribution of the temperature recovery factor, and the relative Stanton number along the length of the model are presented. The studies were carried out in the joint inter-university laboratory of Moscow State University–Bauman Moscow State Technical University, Thermal Gas Dynamics on the experimental base of the Institute of Mechanics, Moscow State University. [ABSTRACT FROM AUTHOR]

Studying mixing and re-stratification during and after hurricanes have important implications for the simulation of circulation and bio-geochemical processes in oceanic and shelf waters. Numerical experiments using FVCOM on an unstructured computational mesh were implemented to study the direct effect of hurricane winds on the mixing and temperature redistribution of the stratified Louisiana shelf during Hurricane Katrina (2005), as well as the post-storm re-stratification timescale. The model was forced by Katrina's wind stress obtained from a combination of H-Wind database and NCEP model. The climatological profiles of temperature and salinity for August (the month in which Katrina occurred) from the world ocean atlas (WOA, 2013) were used as the pre-storm conditions over the shelf. Model results for sea surface temperature (SST) and mixed layer depth (MLD) were validated versus SST data from an optimally interpolated satellite product, and the MLD was calculated from the heat budget equation of the mixed layer. Model results were used to examine the temporal and spatial responses of SST and MLD over the shelf to Katrina. Results showed that intense mixing occurred within 1–1.1 RMW (RMW is the radius of maximum wind for Katrina), with turbulent mixing as the dominant mixing force for regions far from the eye, although upwelling was an important contributor to modulating SST and MLD. During the peak of Katrina and for the shelf regions severely affected by the hurricane wind, three distinct temperature zones were formed across the water column: an upper mixed layer, a transition zone, and a lower upwelling zone. Shelf re-stratification started from 3 h to more than two weeks after the landfall, depending on the distance from the track. The mixing during Hurricane Katrina affected the seasonal summertime hypoxic zone over the Louisiana shelf and likely contributed to the water column re-oxygenation. [ABSTRACT FROM AUTHOR]

Based on the Reynolds-averaged Navier-Stokes (RANS) method, the standard k-ε turbulence model was used to simulate the effects of the side ratio (SR: building depth/building width, SR = 0.5, 1.0, 1.5, and 2.0, respectively) of isolated buildings on the flow field and pollutant of ethylene dispersion under unstable temperature stratification and neutral conditions. The results showed that under unstable temperature stratification, the updraft on the leeward side of the building caused the high temperature gas to flow upward and the temperature gradient to drop. Compared with the neutral condition, the length of the recirculation zone was shorter, and with the decrease in SR, the vortex in the recirculation zone became larger and more stable. Because the pollution source was located on the leeward side of the building, the pollutant gas was concentrated in the area between the pollution source and the leeward side of the building. The near-ground concentration of pollutants under unstable temperature stratification was lower than that under neutral conditions, and with the decrease in SR, the near-ground axis concentration decreased while the width of the pollutant plumes increased. [ABSTRACT FROM AUTHOR]

The convective heat transfer in non-Newtonian fluid flow in the presence of temperature stratification, heat generation, and heat absorption effects is debated by using artificial neural networking. The heat transfer rate is examined for the four different thermal flow regimes namely (I) thermal flow field towards a flat surface along with thermal radiations, (II) thermal flow field towards a flat surface without thermal radiations, (III) thermal flow field over a cylindrical surface with thermal radiations, and (IV) thermal flow field over a cylindrical surface without thermal radiations. For each regime, a Nusselt number is carried out to construct an artificial neural networking model. The model prediction performance is reported by using varied neuron numbers and input parameters, and the results are assessed. The ANN model is designed by using the Bayesian regularization training procedure, and a high-performing MLP network model is used. The data used in the creation of the MLP network was 80 percent for model training and 20 percent for testing. The graph shows the degree of agreement between the ANN model projected values and the goal values. We discovered that an artificial neural network model can provide high-efficiency forecasts for heat transfer rates having engineering standpoints. For both flat and cylindrical surfaces, the heat transfer normal to the surface reflects inciting nature towards the Prandtl number and heat absorption parameter, while the opposite is the case for the temperature stratification parameter and heat generation parameter. It is important to note that the magnitude of heat transfer is significantly larger for Flow Regime-IV in comparison with Flow Regimes-I, -II, and -III. [ABSTRACT FROM AUTHOR]

Abstract Background To adapt seasonal climate changes under natural environments, Polygonatum sibiricum seeds have a long period of epicotyl morphophysiological dormancy, which limits their wide-utilization in the large-scale plant progeny propagation. It has been proven that the controlled consecutive warm and cold temperature treatments can effectively break and shorten this seed dormancy status to promote its successful underdeveloped embryo growth, radicle emergence and shoot emergence. To uncover the molecular basis of seed dormancy release and seedling establishment, a SMRT full-length sequencing analysis and an Illumina sequencing-based comparison of P. sibiricum seed transcriptomes were combined to investigate transcriptional changes during warm and cold stratifications. Results A total of 87,251 unigenes, including 46,255 complete sequences, were obtained and 77,148 unigenes (88.42%) were annotated. Gene expression analyses at four stratification stages identified a total of 27,059 DEGs in six pairwise comparisons and revealed that more differentially expressed genes were altered at the Corm stage than at the other stages, especially Str_S and Eme. The expression of 475 hormone metabolism genes and 510 hormone signaling genes was modulated during P. sibiricum seed dormancy release and seedling emergence. One thousand eighteen transcription factors and five hundred nineteen transcription regulators were detected differentially expressed during stratification and germination especially at Corm and Str_S stages. Of 1246 seed dormancy/germination known DEGs, 378, 790, and 199 DEGs were associated with P. sibiricum MD release (Corm vs Seed), epicotyl dormancy release (Str_S vs Corm), and the seedling establishment after the MPD release (Eme vs Str_S). Conclusions A comparison with dormancy- and germination-related genes in Arabidopsis thaliana seeds revealed that genes related to multiple plant hormones, chromatin modifiers and remodelers, DNA methylation, mRNA degradation, endosperm weakening, and cell wall structures coordinately mediate P. sibiricum seed germination, epicotyl dormancy release, and seedling establishment. These results provided the first insights into molecular regulation of P. sibiricum seed epicotyl morphophysiological dormancy release and seedling emergence. They may form the foundation of future studies regarding gene interaction and the specific roles of individual tissues (endosperm, newly-formed corm) in P. sibiricum bulk seed dormancy.

Temperature stratification between outgoing hot water and incoming cold water is a key factor in diminishing energy loss during the discharging process and maximizing the useful hot water delivered from the tank or enhancing the thermal efficiency of the heating device during the heating process. In this study, the inlet structure and the obstacle plate were designed and modified based on two main factors, the reduction of inlet water velocity and the stipulation of the water recirculation area, to develop temperature stratification through the computational fluid dynamics method. The simulation model's accuracy was validated against the experimental results. The results showed that using the equalizer as an inlet pipe's auxiliary device was the best approach for decreasing the inlet water velocity, which resulted in enhancing temperature stratification. The discharging efficiency improved from 77.3% for the original tank model to 86.1% for the tank with equalizer IV model, which meant an additional 45 L of useful hot water was gained from the good temperature stratification storage tank. The installation of the obstacle plate for controlling the turbulence zone could not improve temperature stratification significantly, which resulted in an increase in discharging efficiency by only 4% more than the original tank model. [ABSTRACT FROM AUTHOR]

Rosa rugosa Thunb. has been explored multi-function in medicinal, edible, cosmetic, ornamental and ecological etc. However, R. rugosa natural populations have recently declined substantially in China, besides of global climate change, this species also has the defect of limiting the reproduction of itself such as the hard-to-release seed dormancy. In this study, only 30% of R. rugosa seeds were viable, and the others were incompletely developed or diseased seeds. Without stratification, morphologically complete viable seeds imbibed water but those seeds could not germinate even after seed husk removal under suitable condition to exhibit a physiological dormancy. After cold (4°C) and warm (18 ± 2°C) stratification, macromolecular substances containing carbon or nitrogen accumulated, and respiration, antioxidant enzyme activity, and gibberellin (GA3) /abscisic acid (ABA) and auxin (IAA)/ABA ratios increased significantly in seeds. Water absorption also increased as endocarps softened. Thus, physiological dormancy of seed was broken. Although warm and cold stratification increased separation between endocarp and embryo, the endocarp binding force was removed insufficiently, because only 10.20% of seeds germinated. Therefore, stratified seeds were treated with simulated bird digestion. Then, folds and cracks in loosened endocarps increased permeability, and water absorption rate increased to 64.43% compare to 21.14% in cold and warm stratification treatment. With simulated digestion, 24.20% of radicles broke through the endocarp with plumules and cambiums to develop into seedlings. Thus, the seed dormancy type of R. rugosa is physiological as seeds imbibed water and possessed fully developed embryos with a low growth potential in combination with a mechanical constraint from the endocarp. Cold stratification helped remove physiological dormancy, and additional warm stratification accelerated the process. The optimal stratification treatment was 4°C for 45 days followed by 18 ± 2°C for 15 days. After warm and cold stratification, simulated bird digestion broke the mechanical constraint from the seed covering layers. Based on this research, production of R. rugosa seedlings can be greatly increased to help protect the species from further declines. [ABSTRACT FROM AUTHOR]

Lake Sevan is the largest freshwater body in the Caucasus region, situated at an altitude of 1,900 m asl. While it is a major water resource in the whole region, Lake Sevan has received little attention in international limnological literature. Although recent studies pointed to algal blooms and negative impacts of climate change and eutrophication, the physical controls on thermal dynamics have not been characterized and model-based assessments of climate change impacts are lacking. We compiled a decade of historical data for meteorological conditions and temperature dynamics in Lake Sevan and used a one-dimensional hydrodynamic model (GLM 3.1) in order to study thermal structure, the stratification phenology and their meteorological drivers in this large mountain lake. We then evaluated the representativeness of meteorological data products covering almost 4 decades (EWEMBI-dataset: 1979-2016) for driving the model and found that these data are well suited to restore long term thermal dynamics in Lake Sevan. This established model setting allowed us to identify major changes in Lake Sevan's stratification in response to changing meteorological conditions as expected from ongoing climate change. Our results point to a changing mixing type from dimictic to monomictic as Lake Sevan will experience prolonged summer stratification periods and more stable stratification. These projected changes in stratification must be included in long-term management perspectives as they will intensify water quality deteriorations like surface algal blooms or deep water anoxia. [ABSTRACT FROM AUTHOR]

The thermal behavior of hot air in a natural convection mode on a solar absorber-plate has not been, so far, modeled experimentally. The present work aimed to assess the performance of the inclined solar air heater [SAH] experimentally by investigating the temperature distribution field in the natural convection flow. The solar plate collector is designed based on the aspect ratio of length to height, L / H, of 6 and 12. The measurements are carried out for the collector tilt angles of 30°, 45°, 60° and 75°. The present investigation demonstrates the temperature distribution of hot air floated in an inclined channel of the SAH. The investigation showed 2D thermal stratification increases when increasing the distance along the collector plate, which looks clear in the SAH with a height of 10 cm. The results of the study show that the thickness of the thermal layers increases with increasing the tilt angle from 30 ̊ to 75 ̊. The reason dates back to increasing the buoyancy force of the hot air overthe absorber. The results demonstrated that the air temperatures for the height of 0.1 m and 45 ̊ tilt angle are higher than that for the height of 0.2 m by 23%.

Rosa rugosa Thunb. has been explored multi-function in medicinal, edible, cosmetic, ornamental and ecological etc. However, R. rugosa natural populations have recently declined substantially in China, besides of global climate change, this species also has the defect of limiting the reproduction of itself such as the hard-to-release seed dormancy. In this study, only 30% of R. rugosa seeds were viable, and the others were incompletely developed or diseased seeds. Without stratification, morphologically complete viable seeds imbibed water but those seeds could not germinate even after seed husk removal under suitable condition to exhibit a physiological dormancy. After cold (4°C) and warm (18 ± 2°C) stratification, macromolecular substances containing carbon or nitrogen accumulated, and respiration, antioxidant enzyme activity, and gibberellin (GA3) /abscisic acid (ABA) and auxin (IAA)/ABA ratios increased significantly in seeds. Water absorption also increased as endocarps softened. Thus, physiological dormancy of seed was broken. Although warm and cold stratification increased separation between endocarp and embryo, the endocarp binding force was removed insufficiently, because only 10.20% of seeds germinated. Therefore, stratified seeds were treated with simulated bird digestion. Then, folds and cracks in loosened endocarps increased permeability, and water absorption rate increased to 64.43% compare to 21.14% in cold and warm stratification treatment. With simulated digestion, 24.20% of radicles broke through the endocarp with plumules and cambiums to develop into seedlings. Thus, the seed dormancy type of R. rugosa is physiological as seeds imbibed water and possessed fully developed embryos with a low growth potential in combination with a mechanical constraint from the endocarp. Cold stratification helped remove physiological dormancy, and additional warm stratification accelerated the process. The optimal stratification treatment was 4°C for 45 days followed by 18 ± 2°C for 15 days. After warm and cold stratification, simulated bird digestion broke the mechanical constraint from the seed covering layers. Based on this research, production of R. rugosa seedlings can be greatly increased to help protect the species from further declines.

Lake Sevan is the largest freshwater body in the Caucasus region, situated at an altitude of 1,900 m asl. While it is a major water resource in the whole region, Lake Sevan has received little attention in international limnological literature. Although recent studies pointed to algal blooms and negative impacts of climate change and eutrophication, the physical controls on thermal dynamics have not been characterized and model-based assessments of climate change impacts are lacking. We compiled a decade of historical data for meteorological conditions and temperature dynamics in Lake Sevan and used a one-dimensional hydrodynamic model (GLM 3.1) in order to study thermal structure, the stratification phenology and their meteorological drivers in this large mountain lake. We then evaluated the representativeness of meteorological data products covering almost 4 decades (EWEMBI-dataset: 1979-2016) for driving the model and found that these data are well suited to restore long term thermal dynamics in Lake Sevan. This established model setting allowed us to identify major changes in Lake Sevan’s stratification in response to changing meteorological conditions as expected from ongoing climate change. Our results point to a changing mixing type from dimictic to monomictic as Lake Sevan will experience prolonged summer stratification periods and more stable stratification. These projected changes in stratification must be included in long-term management perspectives as they will intensify water quality deteriorations like surface algal blooms or deep water anoxia.

This paper focuses on the optimization of the deflector structures and effect of four different deflectors within the tank on the temperature stratification. Four different deflectors inside the tank are numerically studied and analyzed through computational fluid dynamics simulation, which are: (a) A type deflector (a lamina), (b) B type deflector (a lamina with two fins 90 degree apart), (c) C type deflector (a lamina with four fins 90 degree apart) and (d) D type deflector (a lamina with four fins 120 degree apart). The comparison of the tanks with different deflectors and without deflector are proposed in terms of the temperature distribution of the tank, the flow pattern of the tank, the velocity distribution of the tube opening, Stratification number and natural convection Grashof number. The temperature stratification is enhanced by placing the different deflectors inside the tank. Results illustrate that the temperature stratification depends on the effect of different deflectors on the natural convection. The Stratification number improves with the increase of the natural convection Grashof number. Compared to the tank without the deflector, the Stratification number and natural convection Grashof number of the solar water heater improve by 18.90% and 13.95%, respectively, are reported for the tank with the B type deflector or C type deflector. [ABSTRACT FROM AUTHOR]

Background: To adapt seasonal climate changes under natural environments, Polygonatum sibiricum seeds have a long period of epicotyl morphophysiological dormancy, which limits their wide-utilization in the large-scale plant progeny propagation. It has been proven that the controlled consecutive warm and cold temperature treatments can effectively break and shorten this seed dormancy status to promote its successful underdeveloped embryo growth, radicle emergence and shoot emergence. To uncover the molecular basis of seed dormancy release and seedling establishment, a SMRT full-length sequencing analysis and an Illumina sequencing-based comparison of P. sibiricum seed transcriptomes were combined to investigate transcriptional changes during warm and cold stratifications. Results: A total of 87,251 unigenes, including 46,255 complete sequences, were obtained and 77,148 unigenes (88.42%) were annotated. Gene expression analyses at four stratification stages identified a total of 27,059 DEGs in six pairwise comparisons and revealed that more differentially expressed genes were altered at the Corm stage than at the other stages, especially Str_S and Eme. The expression of 475 hormone metabolism genes and 510 hormone signaling genes was modulated during P. sibiricum seed dormancy release and seedling emergence. One thousand eighteen transcription factors and five hundred nineteen transcription regulators were detected differentially expressed during stratification and germination especially at Corm and Str_S stages. Of 1246 seed dormancy/germination known DEGs, 378, 790, and 199 DEGs were associated with P. sibiricum MD release (Corm vs Seed), epicotyl dormancy release (Str_S vs Corm), and the seedling establishment after the MPD release (Eme vs Str_S). Conclusions: A comparison with dormancy- and germination-related genes in Arabidopsis thaliana seeds revealed that genes related to multiple plant hormones, chromatin modifiers and remodelers, DNA methylation, mRNA degradation, endosperm weakening, and cell wall structures coordinately mediate P. sibiricum seed germination, epicotyl dormancy release, and seedling establishment. These results provided the first insights into molecular regulation of P. sibiricum seed epicotyl morphophysiological dormancy release and seedling emergence. They may form the foundation of future studies regarding gene interaction and the specific roles of individual tissues (endosperm, newly-formed corm) in P. sibiricum bulk seed dormancy. [ABSTRACT FROM AUTHOR]

Hydrogen is a promising energy carrier, but safety concerns must be addressed to ensure its widespread use. Aiming at the problem of hydrogen leakage and diffusion in a hydrogen workshop (HWS), a hydrogen diffusion model in the actual temperature stratified environment is established. The law of hydrogen diffusion evolution in this environment is analyzed by simulation and compared with the numerical model. It is revealed that leaked hydrogen in temperature stratified environment will be trapped at a certain height and spread horizontally, which is called the "locking phenomenon". This paper explores the conditions under which this phenomenon occurs by comparing hydrogen diffusion under different temperature gradients and leakage rates. To reduce the risk of "locking phenomenon", the vents were configured for the HWS vents. The results show that the hazard area of hydrogen diffusion is reduced by 41.10% after the vent configuration. This paper provides valuable insights into the evolution of hydrogen diffusion in a temperature stratified environment and proposes an effective solution to mitigate the associated risks. • A hydrogen diffusion model in temperature stratification is established. • The locking height and trajectory of hydrogen are studied. • The necessary conditions for the occurrence of "locking phenomenon" are given. • The deployed vent effectively reduces the hazard area after hydrogen diffusion. [ABSTRACT FROM AUTHOR]

Studying mixing and re-stratification during and after hurricanes have important implications for the simulation of circulation and bio-geochemical processes in oceanic and shelf waters. Numerical experiments using FVCOM on an unstructured computational mesh were implemented to study the direct effect of hurricane winds on the mixing and temperature redistribution of the stratified Louisiana shelf during Hurricane Katrina (2005), as well as the post-storm re-stratification timescale. The model was forced by Katrina’s wind stress obtained from a combination of H-Wind database and NCEP model. The climatological profiles of temperature and salinity for August (the month in which Katrina occurred) from the world ocean atlas (WOA, 2013) were used as the pre-storm conditions over the shelf. Model results for sea surface temperature (SST) and mixed layer depth (MLD) were validated versus SST data from an optimally interpolated satellite product, and the MLD was calculated from the heat budget equation of the mixed layer. Model results were used to examine the temporal and spatial responses of SST and MLD over the shelf to Katrina. Results showed that intense mixing occurred within 1–1.1 RMW (RMW is the radius of maximum wind for Katrina), with turbulent mixing as the dominant mixing force for regions far from the eye, although upwelling was an important contributor to modulating SST and MLD. During the peak of Katrina and for the shelf regions severely affected by the hurricane wind, three distinct temperature zones were formed across the water column: an upper mixed layer, a transition zone, and a lower upwelling zone. Shelf re-stratification started from 3 h to more than two weeks after the landfall, depending on the distance from the track. The mixing during Hurricane Katrina affected the seasonal summertime hypoxic zone over the Louisiana shelf and likely contributed to the water column re-oxygenation.

The convective heat transfer in non-Newtonian fluid flow in the presence of temperature stratification, heat generation, and heat absorption effects is debated by using artificial neural networking. The heat transfer rate is examined for the four different thermal flow regimes namely (I) thermal flow field towards a flat surface along with thermal radiations, (II) thermal flow field towards a flat surface without thermal radiations, (III) thermal flow field over a cylindrical surface with thermal radiations, and (IV) thermal flow field over a cylindrical surface without thermal radiations. For each regime, a Nusselt number is carried out to construct an artificial neural networking model. The model prediction performance is reported by using varied neuron numbers and input parameters, and the results are assessed. The ANN model is designed by using the Bayesian regularization training procedure, and a high-performing MLP network model is used. The data used in the creation of the MLP network was 80 percent for model training and 20 percent for testing. The graph shows the degree of agreement between the ANN model projected values and the goal values. We discovered that an artificial neural network model can provide high-efficiency forecasts for heat transfer rates having engineering standpoints. For both flat and cylindrical surfaces, the heat transfer normal to the surface reflects inciting nature towards the Prandtl number and heat absorption parameter, while the opposite is the case for the temperature stratification parameter and heat generation parameter. It is important to note that the magnitude of heat transfer is significantly larger for Flow Regime-IV in comparison with Flow Regimes-I, -II, and -III.

The construction of high dams results in changes to the ecohydrology processes of river reaches both upstream and downstream of the dam, in addition to causing stratification of reservoir waters. Changes in these hydrodynamic processes then lead to changes in the habitats and nutrients of the waters that are important for basal food chain organisms, consequently affecting bacterial diversity. Here, the Xiangjiaba Hydropower Station (XJB) was used to investigate the above influences on microbial communities. Here, bacterial community structures were examined in 15 samples from upstream of the XJB (UD section) and 15 samples downstream of the XJB (DD section) using 16S rRNA gene sequencing. The bacterial community structures significantly differed between the surface water and 70 m of bottom water. Cyanobacteria was the dominant phylum in these communities and exhibited significantly higher abundances in the surface water. VPA (variance partitioning analysis) suggested that bacterial communities were influenced by and structured due to the combined effects of nutrient, hydrological, and environmental factors in addition to reservoir mixing dynamics. The abundance of Armatimonas, Roseomonas, Limonhabitans, and Flavobacterium were positively correlated with pH, flow velocity, and dissolved oxygen (DO). Total phosphorus (TP) was negatively correlated with the abundance of Acinetobacter, Roseomonas, Armatimonas. Burkholderia, Gemmatimonas, Nitrospira, hgcl.clade, and marine. group, all of which were highly sensitive to changes in water temperature. The results of this study can be used to understand the responses of bacterial communities to physicochemical conditions and water quality changes associated with reservoirs in order to provide a scientific basis for the protection of aquatic ecosystem stability.

The increasing use of Liquefied Natural Gas (LNG) as a fuel for ships and vehicles poses relevant safety concerns, extended to the entire LNG supply chain and distribution network. Understanding the phenomena associated with the behavior of LNG tanks exposed to severe heat sources is thus a fundamental issue to identify potential safety-critical scenarios. The experimental data and modeling approaches currently available, mainly referring to small-scale pilot vessels, feature relevant limitations when extended to large-scale applications. In the present study, a two-dimensional non-equilibrium computational fluid dynamics model (2D CFD) of LNG tanks exposed to fire engulfing scenarios was developed. The 2D CFD model was validated against experimental bonfire data and was extended to simulate the behavior of large-scale vessels used in specific industrial applications, as the road transportation of LNG and the fuel supply of ships. A set of Key Performance Indicators (KPIs) was defined to support the safety assessment of LNG tanks, and to identify the potential transition to safety critical regions during fire exposure. The CFD results obtained allowed investigating the influence of operative parameters and geometry on the pressure build-up in the tanks, as well as on the transient evolution of complicating phenomena, such as the thermal stratification. The KPIs defined provide a useful support for the design of safety systems and for decision making in emergency response. [ABSTRACT FROM AUTHOR]

Temperature stratification between outgoing hot water and incoming cold water is a key factor in diminishing energy loss during the discharging process and maximizing the useful hot water delivered from the tank or enhancing the thermal efficiency of the heating device during the heating process. In this study, the inlet structure and the obstacle plate were designed and modified based on two main factors, the reduction of inlet water velocity and the stipulation of the water recirculation area, to develop temperature stratification through the computational fluid dynamics method. The simulation model’s accuracy was validated against the experimental results. The results showed that using the equalizer as an inlet pipe’s auxiliary device was the best approach for decreasing the inlet water velocity, which resulted in enhancing temperature stratification. The discharging efficiency improved from 77.3% for the original tank model to 86.1% for the tank with equalizer IV model, which meant an additional 45 L of useful hot water was gained from the good temperature stratification storage tank. The installation of the obstacle plate for controlling the turbulence zone could not improve temperature stratification significantly, which resulted in an increase in discharging efficiency by only 4% more than the original tank model.

A numerical calculation model is developed to study the coupled thermal dynamic performance in a cryogenic fuel tank under an intermittent sloshing excitation. Both external heat inputs and the intermittent excitation are realized by User-defined functions. The volume of fluid method is adopted to simulate fluid sloshing, coupled with the mesh motion treatment. Validated against related fluid sloshing experiments, the numerical model was turned out to be acceptable on fluid sloshing prediction. Cooled by subcooled liquid, vapor is always in condensation. The middle vapor pressure test point suffers less from the intermittent excitation and has a linear pressure decrease profile, while the middle liquid pressure test point has fluctuating variations. For vapor and interface temperature monitors, obvious temperature fluctuations appear in the second holding period. While for liquid test points, the temperature profiles experience intensive fluctuations during sloshing periods and stable temperature variation during holding periods. Due to the holding period of external excitation, the tank pressure reduction in intermittent sloshing case is less than that in continuous sloshing case. That is to say the tank pressure decrease rate could be adjusted by proper intermittent excitation. This work is significant to deeply understand fluid sloshing phenomenon under some irregular external excitations in fuel storage tanks. • A thermal-flow coupled model is developed to investigate the thermal performance in a sloshing cryogenic storage tank. • Effect of intermittent excitation on the thermal performance is investigated by implementing UDF into the numerical model. • Fluid pressure variations and temperature stratification are greatly predicted and detailedly compared. • The performance comparisons are made between the continuous sinusoidal excitation and intermittent sinusoidal excitation. [ABSTRACT FROM AUTHOR]

Copyright of KPI Science News is the property of National Technical University of Ukraine KPI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The features of Casson liquid when flow field is thermally stratified are offered in this article. The flow is taken through an inclined cylinder with both MHD fluid and thermal radiations assumptions. A mathematical model is constructed in terms of differential equations via fundamental laws. Since the resultant system is non-linear so a self-coded computational algorithm is implemented to report numerical solution. The obtain observations in this regard are presented by way of both tabular and graphical trends. It is noticed that the Casson fluid temperature is decreasing function of thermal stratification parameter while opposite trend is observed via thermal radiation parameter. Moreover, the cylindrical geometry admits enlarged variations towards involved physical parameters as compared to flat surface. [ABSTRACT FROM AUTHOR]

• New analytic solution for convective heat transport. • Qualitative insight into the buoyant jet entrainment process. • Understanding some qualitative features of the charging process of hot fluid containers. • Investigation of the effectiveness of different modeling possibilities around the jet shear layer. • New test problem to verify the consistency and error estimate of numerical methods. Unsteady heat transfer process and the developed temperature field inside hot water storage tanks with a buoyant inflow jet can be described by a coupled first order partial and a first order ordinary differential equation system (PDE-ODE). Non-polynomial series solutions of this PDE-ODE system for an initial-boundary condition have been presented. The different solutions have been compared to the numerical solution of the PDE-ODE system and to the relevant measurement. The rate of the convergence of the analytic solutions is also investigated. Linear equation systems are constructed to calculate the constant coefficients of the series solution. Additionally the entire 3D flow and temperature field of the investigated thermo physical process have been calculated numerically and compared to the results of the analytic solution of the simplified model. Besides theoretical importance, the solutions can be benchmark solutions to develop the computational heat transfer. [ABSTRACT FROM AUTHOR]

Results of numerical hydrothermal simulation of the thermal regimes in the design of the external cooling systems of the Akkuyu nuclear power plant (Turkey) and the Kudan Kulam nuclear power plant (India), both of which are situated on the sea coast, are set forth. The STREAM 3D software package for calculation of the three-dimensional fields of stratified flows and temperatures in a hydrostatic approximation are used in the investigations. Different ways of optimizing the thermal regimes and configurations of coastal hydraulic structures by means of which the temperature in the water intakes of a nuclear power plant and in the adjacent body of water may be reduced to levels that satisfy the regulatory requirements are proposed. [ABSTRACT FROM AUTHOR]

• A water storage tank designed for geothermal heating incorporates a flow equalizing plate within the tank, significantly improving temperature stratification and the heat storage/release performance of the tank. • An exclusive experimental platform was built to evaluate the water storage tank's performance, facilitating simultaneous exploration of various functionalities. • The research results indicate that the new type of water storage tank significantly enhances temperature stratification and heat storage/release performance compared to traditional water storage tanks. This is of crucial significance for improving the utilization efficiency of geothermal resources and reducing the costs associated with geothermal heating. To enhance the utilization of geothermal energy in a geothermal heating and energy storage coupling system, a new water storage tank is proposed. The tank's structure comprises a horizontally designed multi-slot form with a flow equalizing plate positioned in the middle. Subsequently, an experimental system for evaluating the water storage tank's performance was designed, and a test rig was established. The study aimed to explore the thermocline's thickness variation using three distinct flow equalizing plate structures–uniform shunt, middle shunt, and side shunt—and examine the heat storage/release performance under different operational conditions. Concurrently, the applicability of the water storage tank's structure under various heat storage conditions was assessed. The findings revealed the following: (1) Under identical working conditions, the new tank displayed a thermocline's thickness proportion to the tank's height, ranging from 20.25% to 33.75%, lower than that of a traditional water storage tank. This indicates a superior temperature stratification performance for the new water storage tank. (2) At an inlet cross-sectional velocity of <0.40 m/s, the side shunt flow equalizing plate resulted in the thinnest thermocline's thickness. Conversely, with an inlet cross-sectional velocity of ≥0.40 m/s, the uniform shunt flow equalizing plate optimized the temperature stratification performance. (3) Higher initial temperatures in the tank led to reduced total heat storage and release, along with a decline in the heat release/storage ratio. For initial temperatures of 30°C, 35°C, and 40°C, the water storage tank exhibited heat release/storage ratios of 95.11%, 93.07%, and 92.04%, respectively, surpassing those of a traditional water storage tank. [ABSTRACT FROM AUTHOR]

The basic aim of the task is to compile a temperature stratification system in an accumulation tank. The range of the thesis concerns the shape and dimensions of a stratification system for an accumulation tank. Thermal stratification is a process that comprises the maintaining of temperature stratification at different levels of an accumulation tank which reduce to a minimum the process of temperature equalization. It results from the fact that the thermal stratification in a tank significantly increases the installation efficiency and improves the process of energy storing. It is connected with a thermodynamic element quality, that is the higher the temperature, the higher the energy, and, thus, the thermos-dynamic element quality. In this phenomenon, thanks to the same amount of accumulated thermal energy and average temperature, as in a fully mixed tank, the user has a higher temperature in the upper part of the tank at his disposal. It has significant importance in the case when there is a low-temperature heating medium that transfers heat to the accumulation tank. Such a situation occurs when heat is absorbed from synthetic freons used in cooling and air-conditioning systems.

We have found that few attempts are reported on Williamson fluid flow yields by an inclined cylindrical surface. To be more specific, Williamson fluid flow regime characteristics under stagnation point region especially when it is manifested with mutual interaction of double stratification and mixed convection effects are not proposed as yet. Therefore, we have considered stagnation point mixed convection Williamson fluid flow brought by an inclined cylinder in the presence of temperature and concentration stratification phenomena. Further, the fluid flow is entertained through no slip condition i-e the velocity of particles is directly related to velocity of cylindrical surface due to stretching. The physical situation within the real concerned constraints is translated in terms of differential equations as a boundary value problem. To make implementation of computational algorithm possible, following steps are taken into account • The PDE’s are transformed into ODE’s by using suitable transformation. • The resulting boundary value problem is converted into an initial value problem. • These constructed ordinary differential equations are solved computationally by shooting technique charted with Runge-Kutta scheme. • The effect logs of an involved physical flow parameters are explored by way of graphical outcomes and tabular values.

The stability of the state of rest of a liquid medium in a gravitational field has been studied in a linear approximation. The density of the medium is linearly dependent on temperature and on the concentration of an admixture. In the background state, the admixture is distributed uniformly, and the temperature stratification is stable (the density decreases with altitude). Therefore, according to the known criteria, the state of rest is considered stable. It was shown that even relatively weak thermodiffusion at negative Soret coefficients can destabilize the stable density-stratified medium (neutral curves characterizing a monotonic instability in an infinite vertical layer were found). In the problem of heating by the side boundary, the possibility of an effective "negative heat capacity"—a decrease in the temperature in the heat input region—is shown. [ABSTRACT FROM AUTHOR]

Low-temperature space heating systems play a prominent role in improving the indoor air quality (IAQ) and thermal comfort of energy efficient buildings in cold-climate countries such as Norway. All-air heating (AAH) systems can be a practical solution because they simplify the space heating system and use low temperature energy sources. However, temperature stratification and deficient air distribution in the occupied part of the room can reduce the AAH performance. This study evaluated the performance of a low-temperature AAH system in an office cubicle designed in accordance with the Norwegian passive house (PH) standard and equipped with an active supply diffuser. Unlike conventional supply diffuser, active supply diffusers have variable slot opening permitting draught-free airflow adjustment with moving plates changing position, so that a constant supply air velocity was achieved. System performance simulations were validated by experimental data and then analysed for various supply and outdoor conditions using thermal comfort indices, IAQ indices, and the Archimedes number (Ar). The results showed that, when negatively buoyant air was supplied, the maximum indoor temperature difference between 0.1 m and 1.1 m above the floor was around 1.5K, which is within the recommended comfort range. Furthermore, the air diffusion performance index (ADPI) analysis showed a relatively high diffusion of air in the occupancy zone for all the scenarios, with the minimum ADPI around 75% for the scenarios with a negative Archimedes number. The active supply diffuser could satisfy the thermal comfort requirement even when the system was operating with the minimum airflow rate. • Performance of an all-air heating system with active supply diffuser was studied. • CFD analysis was done using different thermal comfort and air distribution indices. • Archimedes number for various cases was defined to better interpret the results. • Applying active supply diffuser could avoid strong temperature stratification. • Minimum air diffusion performance index of 75% in the occupancy zone was reached. [ABSTRACT FROM AUTHOR]

In order to determine the influence of damming on the spatial distribution of dissolved inorganic carbon and dissolved inorganic nitrogen in river，we stratified sampling in the karst area deeply water reservoir (Longtan Reservoir) in September 2016 (rainfall season) to access to the main physical and chemical parameters of water. We studied the spatial distribution pattern of D/C，DIN and C/N in water by classical statistics and geo statistics methods. The results show that the temperature shows obvious stratification and results stratification of total dissolved solids，pH，Alkalinity，D/C，D/N and NH4+- N at Longtan Reservoir in summer. Apart from water temperature and pH，the main physical and chemical parameters have large variation in space and decrease from the surface to the bottom，in the order of DIC>C/N> D/N. The horizontal variation of D/C，D/N and C/N in the reservoir area has obvious spatial structure with the dam body is larger than the tail. The spatial heterogeneity produced by the experimental random error is small and the three have strongly spatial auto correlation. However， the natural structural factors play a significantly role in spatial heterogeneity caused on D/C，D/N and C/N. [ABSTRACT FROM AUTHOR]

Highlights • A cryogenic sensor based on fiber Bragg grating is developed. • The fiber with pre-tensile force is adhered onto temperature sensitive metal. • The experimental results reveal that the maximum operating error is less than 0.35 °C. • The availability of the designed FBG sensor for LNG monitoring is investigated experimentally. Abstract Condition monitoring is critical for the safe usage of Liquefied Natural Gas (LNG). Temperature distribution is an important index of LNG storage and it can reflect the tendency of heat leakage and the situation of evaporation. However, traditional electric sensor may cause explosion due to spark. In this paper, a cryogenic sensor based on fiber Bragg grating (FBG) is developed in which the fiber with pre-tensile force is adhered onto temperature-sensitive metal. The liquefied nitrogen (LN 2) is used to test the designed sensor instead of LNG for safety consideration. By setting every 10 K as a testing point from 83 K to 193 K, the experimental investigation reveals that there is a positive linear relation between the reflected wavelength and the testing temperature. By using multiple linear functions to fit experimental data, the maximum measuring error of FBG sensor is less than ±0.35 K, which indicates the usability of this sensor in LNG storage. Finally, an experiment of temperature stratification is performed to validate usability of FBG sensor for LNG monitoring. The results indicate that the designed FBG sensor has enough accuracy to reveal LNG rollover and it has similar dynamic performance with RTD sensor. [ABSTRACT FROM AUTHOR]

In this paper, we generally summarize the main issues in the operational period of water conservancy and hydropower projects in China over the past several decades. First, the adverse impacts of these projects since the technical guidelines were proposed in 2006 are analyzed. Then, combined with projects and experience from 2006 to 2014, the four main issues are summarized: (1) There exist many questions in the design and construction of fishways, which are useful for fish migration, and the migration effects are not as expected. (2) Temperature stratification affecting the downstream fish is the major impact of temperature, and alters fish spawning in the reproduction season. (3) Ecological base flow has been one of the primary questions of the last 30 years in China, the greatest related difficulty being quantification of the amount and flow process necessary to satisfy fish life history. (4) Fish habitat protection and restoration are popular topics in recent years with the development of river ecosystem restoration. Fish habitat loss due to the impacts of dam construction and habitat fragmentation has become more and more serious. These four issues are now the main difficulties in water project management, and interact with one another to bear combined effects on river ecosystems. The issues of eco-hydraulic consideration in the design period are the key factors. Finally, future priorities for research and practice of environmental protection for water conservancy and hydropower projects in China are proposed. The main purpose of this paper is to enhance the scientific research, monitoring, and assessment of operating effectiveness.

Highlights • Temperature stratification characteristics of six kinds of tanks were compared. • Heat charging efficiency of six kinds of tanks was compared during charging. • The effect of radius ratio on truncated circular cone tanks' charging was studied. • The optimal tank shape for charging was determined. Abstract In solar water heating systems, the structures of thermal storage devices have played essential roles in the improvement of thermal charging efficiency and system performance. This article was focused on the optimization of thermal storage tanks, as well as the influences of thermal storage tank structures on the temperature stratification and heat storage capacity. The thermal characteristics of three shapes of thermal storage tanks were investigated and analyzed through CFD (Computational Fluid Dynamics) simulation, which were: (a) Cylindrical tank, (b) Circular truncated cone tank and (c) Spherical tank. It was observed that among the three thermal storage tanks, the spherical tank had significant symmetrical temperature stratification, while the truncated circular cone tank had the best temperature stratification and thermal charging efficiency. For the circular truncated cone tank, it was found that when the radius ratio (n) of the water tank was 0.554, it could approach the excellent characteristics of temperature stratification and thermal storage performance. This study could provide a theoretical basis for the structure optimization of the solar energy storage devices, as well as proving to be beneficial to the enhancement of thermal charging efficiency. [ABSTRACT FROM AUTHOR]

Abstract The current analysis is carried out to envision the properties of magneto-hydrodynamic boundary layer stagnation point flow of Eyring-Powell (non-Newtonian) fluid induced by an inclined stretching cylindrical surface in the presence of both mixed convection and Joule heating effects. Flow analysis is manifested with temperature stratification phenomena. The strength of temperature adjacent to the cylindrical surface is assumed to be higher in strength as compared to the ambient fluid. A suitable similarity transformations are utilized to convert the flow conducting equations (mathematically modelled) into system of coupled non-linear ordinary differential equations. A fifth order Runge-Kutta algorithm charted with shooting scheme is used to trace out the numerical additions. It was found that the velocity profile is an increasing function of both mixed convection and curvature parameters. Temperature profile show inciting nature towards Eckert number. In addition, a straight line and parabolic curve fitting way of study is executed to inspect the effect logs of mixed convection parameter, magnetic field parameter, thermal stratification parameter and heat generation parameter on skin friction coefficient and heat rate. It seems to be first attempt in this direction and will serve as a facilitating source for the preceding studies regarding fluid rheology. [ABSTRACT FROM AUTHOR]

Air flow distribution in chilled food facilities plays a critical role not only in maintaining the required food products temperature but also because of its impact on the facility energy consumption and CO 2 emissions. This paper presents an investigation of the thermal environment in existing food manufacturing facilities, with different air distribution systems including supply/return diffusers and fabric ducts, by means of both in-situ measurements and 3D CFD simulations. Measurements and CFD simulations showed that the fabric duct provides a better environment in the processing area in terms of even and low air flow if compared to that with the diffusers. Moreover, temperature stratification was identified as a key factor to be improved to reduce the energy use for the space cooling. Further modelling proved that air temperature stratification improves by relocating the fabric ducts at a medium level. This resulted in a temperature gradient increase up to 4.1 °C in the unoccupied zone. [ABSTRACT FROM AUTHOR]

The current pagination summarized the influence of bio-convection Schmidt number, bio-convection Peclet number and micro-organisms concentration difference parameter on the density of motile gyrotactic micro-organisms when they have interaction with the thermally stratified magneto-nanofluid flow past a vertical stretching surface. It is observed that the density of motile microorganisms is the decreasing function of the bio-convection Schmidt and Peclet numbers. It is trusted that the outcomes of present analysis will serve as a helping source for the upcoming developments regarding individualities of motile gyrotactic micro-organisms subject to boundary layer flows induced by stretching surfaces. [ABSTRACT FROM AUTHOR]

The results of numerical hydrothermal modeling of the temperature regimes pf the cooling ponds of the Rostov NPP and fifth unit of the Novovoronezh NPP are presented. The STREAM-3D software package is used in the study to calculate the three-dimensional fields of stratified flows and temperatures in a hydrostatic approximation. Variants of optimizing the thermal regimes that reduce the temperature at the NPP external cooling water intake system are proposed. [ABSTRACT FROM AUTHOR]