Bowen Ratio Research Articles

Thermal–moisture dynamics and thermal stability of active layer in response to wet/dry conditions in the central region of the Qinghai–Tibet Plateau, China

The amount of rainfall varies unevenly in different regions of the Qinghai-Tibet Plateau, with some regions becoming wetter and others drier. Precipitation has an important impact on the process of surface energy balance and the energy-water transfer within soils. To clarify the thermal-moisture dynamics and thermal stability of the active layer in permafrost regions under wet/dry conditions, the verified water-vapour-heat coupling model was used. Changes in the surface energy balance, energy-water transfer within the soil, and thickness of the active layer were quantitatively analyzed. The results demonstrate that rainfall changes significantly affect the Bowen ratio, which in turn affects surface energy exchange. Under wet/dry conditions, there is a positive correlation between rainfall and liquid water flux under the hydraulic gradient; water vapour migration is the main form under the temperature gradient, which indicates that the influence of water vapour migration on thermal-moisture dynamics of the active layer cannot be neglected. Concurrently, regardless of wet or dry conditions, disturbance of the heat transport by conduction caused by rainfall is stronger than that of convection by liquid water. In addition, when rainfall decreases by 1.5 times (212 mm) and increases by 1.5 times (477 mm), the thickness of the active layer increases by 0.12 m and decreases by 0.21 m, respectively. The results show that dry conditions are not conducive to the preservation of frozen soil; however, wet conditions are conducive to the preservation of frozen soil, although there is a threshold value. When this threshold value is exceeded, rainfall is unfavourable for the development of frozen soil.

Seasonal characterization, sources, and source-specific risks of PM2.5 bound PAHs at different types of urban sites in central China

Polycyclic aromatic hydrocarbons (PAHs) have been extensively investigated in China. However, most previous studies only focused on specific locations. Here, we conducted field studies simultaneously to explore the seasonal characterization, sources, and source-specific risks of 16 PAHs in four polluted cities in China. Similar seasonal Σ16 PAHs variations are observed in all four sites with relatively high values in winter and low values in summer and the ratios of Σ16 PAHs between winter and summer range from 2.7 to 4.4. From summer to winter, the extent of PAH increase outpaces that of PM2.5 increase resulting in significant increase of ∑16 PAHs/PM2.5 in winter. Five potential sources were resolved by PMF: (1) coal combustion (32–52%); (2) vehicle emissions (19–29%); (3) evaporation (9–26%); (4) coke oven emission (11–15%); and (5) biomass burning (5–13%). The highest fraction of evaporation is found in the Luoyang site due to the presence of many petrochemical plants, the largest oil refinery in Henan and large oil storage tanks. The coking factor contributes the largest proportion in Anyang site because of many out of date inefficient coking facilities. The source-related risks in four sites are all higher than the USEPA guideline value (1.0 × 10−6) except for biomass burning. The largest total risks are observed at Luoyang site, slightly higher than those of other cities. Our results suggest that the PAHs still need to be concerned due to the complexity of sources and source emitted risks in different type of cities, and specific source control strategies should be target in different regions.

Bulk Transfer Coefficients Estimated From Eddy‐Covariance Measurements Over Lakes and Reservoirs

AbstractThe drag coefficient, Stanton number and Dalton number are of particular importance for estimating the surface turbulent fluxes of momentum, heat and water vapor using bulk parameterization. Although these bulk transfer coefficients have been extensively studied over the past several decades in marine and large‐lake environments, there are no studies analyzing their variability for smaller lakes. Here, we evaluated these coefficients through directly measured surface fluxes using the eddy‐covariance technique over more than 30 lakes and reservoirs of different sizes and depths. Our analysis showed that the transfer coefficients (adjusted to neutral atmospheric stability) were generally within the range reported in previous studies for large lakes and oceans. All transfer coefficients exhibit a substantial increase at low wind speeds (<3 m s−1), which was found to be associated with the presence of gusts and capillary waves (except Dalton number). Stanton number was found to be on average a factor of 1.3 higher than Dalton number, likely affecting the Bowen ratio method. At high wind speeds, the transfer coefficients remained relatively constant at values of 1.6·10−3, 1.4·10−3, 1.0·10−3, respectively. We found that the variability of the transfer coefficients among the lakes could be associated with lake surface area. In flux parameterizations at lake surfaces, it is recommended to consider variations in the drag coefficient and Stanton number due to wind gustiness and capillary wave roughness while Dalton number could be considered as constant at all wind speeds.

Diurnal pattern and driving mechanisms of the thermal effects of an urban pond

Water bodies are often considered an effective solution to cool their surroundings in hot summers. However, their potential adverse nocturnal warming effect has not yet been investigated thoroughly or considered in current urban planning strategies. This study evaluates the diurnal thermal effects of an urban pond in Nanjing, China, and explores the underlying mechanisms through energy-balance analysis using the Bowen ratio method. In-situ air temperature/humidity, water temperature profile, and upward and downward short- and long-wave radiation on hot summer days were measured. Results demonstrate that compared with a reference soil-site, the pond exerted a moderate daytime cooling effect (0.6 °C) but a pronounced nocturnal warming effect (1.8 °C). During the day, the energy input Rnet (net radiation flux) comprised 77% QS (heat storage) and 23% QE (latent heat flux), while QH (sensible heat flux) was negligible. At night, a negative QS acted as a heat source from the pond, which was released through QH (5%), QE (51%), and Rnet (44%). Results of this study improve our understanding of the thermal effects of urban water bodies, and can be used to inform urban planners and landscape designers regarding implementation of water bodies in the urban context for creating sustainable cool cities and communities.

Investigation into the effects of passive check valves on the thermal performance of pulsating heat pipes

A passive check valve without a subsidiary channel that effectively increases the thermal performance of pulsating heat pipes (PHPs) is proposed. To realize this, topology optimization is employed to maximize the diodicity (Di) of the check valve. The proposed passive check valve consists of a pair of hook-shaped structures and has a Di value of 2.2. PHPs with overall dimensions of 53.5×80×1.5 mm3 are fabricated to investigate the effects of the passive check valve on the thermal performance and the flow behaviors of PHPs. A ten-turn closed-loop serpentine square channel with a height and an average width of 0.6 mm and 2 mm is engraved on a silicon plate and then covered with a glass plate for flow visualization. A total of twenty passive check valves are implemented into the entire channel at the locations where the condenser section and the adiabatic section meet. HFE-7000 is used as the working fluid and the filling ratio is fixed at 48% by volume. The experimental results on PHPs with the single-diameter channel show that the proposed passive check valves significantly improve the thermal performance of PHPs: 48% and 81% reduction in the thermal resistance in the vertical orientation and the horizontal orientation, respectively. Also, the experimental results on PHPs with the dual-diameter channel show that the passive check valves effectively improve the thermal performance over the wide operating range regardless of the orientation of PHPs: 33% and 34% reduction in the thermal resistance in the vertical orientation and the horizontal orientation, respectively. It is found through high-speed photography that this enhanced performance occurs because the passive check valves significantly increase the time-averaged volumetric fraction of vapor in the condenser section by 5 times from 0.09 to 0.45. This stems from the fact that the passive check valves effectively make the working fluid flow 3.5 times more preferentially in one direction over the other.

Stable Isotopes Reveal the Effect of Canopy and Litter Layer Interception on Water Recharge in a Subtropical Manmade Forest of Southwest China

In areas completely covered by vegetation, the rainwater that passes through the canopy layer and litter layer is the source supplying surface runoff and seeping into the soil layer. To reveal the influence mechanisms of the canopy and litter layer on water supply in forest areas, this study conducted event-scale water sampling and hydrogen and oxygen isotopic comparison for the rainfall, canopy throughfall and litter layer throughfall in a manmade forest. The results show that canopy interception will lead to a more concentrated distribution and lower isotopic variability. The d-excess and the intercept and slope of the δD-δ18O regression line of the canopy throughfall are slightly higher than those of rainfall, reflecting that the evaporation fractionation caused by canopy interception is weak, and the selection process may play a leading role. Compared with the canopy throughfall, the distribution of the δ18O, δD and d-excess in the litter layer throughfall is more dispersed, and the slope and intercept of the δD-δ18O regression line are higher, indicating the strong influence of non-equilibrium fractionation on the water input caused by litter layer interception. The isotopic differences between the litter layer throughfall and canopy throughfall indicate that the water components of small-scale precipitation events (precipitation amount lower than 5 mm) and the early stage of large-scale precipitation events (precipitation amount higher than 25 mm) may be dissipated by litter layer interception, while that of the latter stage of large-size events is slightly affected. The findings of this study will be helpful to deeply understand the mechanisms of the water cycle in the forest ecosystem under the background of climate change and provide insights for the sustainable utilization of water resources.

Geochemical classification and secondary alteration of crude oil in the southern thrust belt of Junggar Basin

This study analyzed, 18 oil samples from four representative oil-bearing secondary tectonic units in the southern thrust belt of the Junggar Basin. The genetic types and the secondary alteration of oil were discussed based on the characteristics of light hydrocarbon compounds, adamantanes, sterane/terpene biomarkers, and stable carbon isotopic composition of the bulk oil. . The results show that the oil in the study area can be divided into five categories. Type I oil is characterized by 13C-depleted carbon isotopes, a low pristane to phytane ratio, and high gammacerane and low diasterane content, whereas Type II oil exhibits the opposite characteristics. Type III is very similar to Type II oil but has a higher 13C-depleted bulk carbon isotopic composition and a wider carbon number of tricyclic terpenes. Type IV and V oils are similar to Type I oils, except for relatively lower gammacerane content. Further, Type IV oils also have high ααα 20R regular sterane content, 13C-enriched bulk oil carbon isotopes, and a higher pristane to phytane ratio than Type I oil. In contrast, the relative content of C27 regular steranes of Type V oils is considerably lower than that of Type I oils. The oil in the study area has not suffered from biodegradation. Maturity information indicated by regular biomarkers (i.e., steroid, terpene, and phenanthrene) and adamantane differs significantly, with the latter exhibiting a strong cracking characteristic. This reflects the charging and mixing of oils formed at different evolution stages. The other types of oils are in the normal oil-generating window and do not suffer from intense cracking. The oil in the study area is generally subjected to evaporative fractionation, but there are obvious differences in the degree of alteration between different oil-bearing structures and different reservoirs with the same structure. This study is of great significance for understanding the origin and accumulation process of oil and gas in a complex structural zone.

Orbital remote sensing to estimate evapotranspiration in a cotton cropping system irrigated by a centre pivot

Evapotranspiration (ET) estimation is essential for adequate management of water resources. The main ways to quantify ET are based on the use of field sensors, class A tanks, Bowen's ratio method, turbulent vortex correlation analysis, use of lysimeters, and through Remote Sensing (RS), which allows estimating biophysical parameters based on satellite images. The objective of the research was to determine the effective evapotranspiration (ETe) of cotton plantations irrigated with a centre pivot, using the Surface Energy Balance Algorithm for Land (SEBAL), Mapping Evapotranspiration at High Resolution and with Internalized Calibration (METRIC) and Simple Algorithm for Evapotranspiration Retrieving (SAFER) methods. Comparisons were made for three agricultural years, using the R², RMSE, MAE, MBE and R statistics. The best performances in the crops were obtained with the SEBAL vs. SAFER models, which presented mean values of 0.54, -0.30 and 0.31 mm d-1 in RMSE, MBE and MAE, respectively. The data obtained by all three models can be applied to estimate ETe in irrigated cotton plantations and, consequently, their results can assist in irrigation management and in crop treatments

Effects of local aerosol and transported dust pollution on the surface energy balance over farmland in eastern China during spring

Compared with the urban boundary layer, air pollution–surface energy budget interactions in farmland areas are relatively sparse. To investigate the roles of local aerosol and transported dust pollution on the surface energy balance over farmland, a field experiment was conducted during spring 2016 in eastern China. The heavy pollution episodes during the measurement period were typically accompanied by easterly winds, low wind speeds, and high relative humidity. On polluted days, relative to clean days, both downward and upward shortwave radiation decreased by 46%, while downward and upward longwave radiation increased by 4% and 1%. The combined effects of the four radiation components resulted in a 33% reduction in net radiation on polluted days, and thus, the surface energy budget changed. Polluted days had 15% (58%) less sensible (latent) heat flux than clean days. This resulted in a higher daytime Bowen ratio on polluted days (0.83) compared to clean days (0.44). In a case analysis of dust pollution, high wind speeds and continuous high pressure induced the outbreak of the dust pollution episodes. Compared to local pollution events, the latent (sensible) heat flux was reduced more (less) than that in transported dust pollution events. Generally, this work has important implications for understanding the surface energy balance across land–atmosphere interactions over farmland regions, which are experiencing frequent aerosol pollution from local emissions and transboundary dust events.

Numerical Examination of the Dynamic Evolution of Fluctuations in Cavitation and Pressure in a Centrifugal Pump during Startup

Rapid changes in the performance-related parameters of a pump during its startup operation lead to large pressure fluctuations and structural vibrations in it. In view of these problems, this study investigates the evolution of cavitation and the characteristics of fluctuations under pressure in a centrifugal pump during startup. We use the finite volume method to simulate this dynamic process. To characterize the acceleration, we assume that the rotational speed and rate of flow of the pump are not constant but vary with time. A steady-state numerical simulation is performed to examine the external characteristics of the pump to verify the accuracy of the numerical procedure. The evolution of fluctuations in the cavity and pressure over time is then analyzed in detail. We use the short-term Fourier transform for post-processing in light of its advantage in treating non-stationary signals. The results indicate that both the frequency and the amplitude of the fluctuations in pressure increase with the speed of the impeller. The transient operation causes the average pressure at the inlet of the impeller to decrease to the evaporation pressure, and this leads to an increase in the volume fraction of vapor. Moreover, both the impeller–tongue interaction and the impeller–diffuser interaction influence the fluctuations in cavitation.

The effect of relative humidity on eddy covariance latent heat flux measurements and its implication for partitioning into transpiration and evaporation

While the eddy covariance (EC) technique is a well-established method for measuring water fluxes (i.e., evaporation or 'evapotranspiration’, ET), the measurement is susceptible to many uncertainties. One such issue is the potential underestimation of ET when relative humidity (RH) is high (>70%), due to low-pass filtering with some EC systems. Yet, this underestimation for different types of EC systems (e.g. open-path or closed-path sensors) has not been characterized for synthesis datasets such as the widely used FLUXNET2015 dataset. Here, we assess the RH-associated underestimation of latent heat fluxes (LE, or ET) from different EC systems for 163 sites in the FLUXNET2015 dataset. We found that the LE underestimation is most apparent during hours when RH is higher than 70%, predominantly observed at sites using closed-path EC systems, but the extent of the LE underestimation is highly site-specific. We then propose a machine learning based method to correct for this underestimation, and compare it to two energy balance closure based LE correction approaches (Bowen ratio correction, BRC, and attributing all errors to LE). Our correction increases LE by 189% for closed-path sites at high RH (>90%), while BRC increases LE by around 30% for all RH conditions. Additionally, we assess the influence of these corrections on ET-based transpiration (T) estimates using two different ET partitioning methods. Results show opposite responses (increasing vs. slightly decreasing T-to-ET ratios, T/ET) between the two methods when comparing T based on corrected and uncorrected LE. Overall, our results demonstrate the existence of a high RH bias in water fluxes in the FLUXNET2015 dataset and suggest that this bias is a pronounced source of uncertainty in ET measurements to be considered when estimating ecosystem T/ET and WUE.

Experimental study on interface characteristics of liquid sodium-water vapor interaction in SWR

When the sodium-water boundary in the sodium-cooled fast reactor (SFR) fails, water vapor will enter the liquid sodium and cause the sodium water reaction (SWR) accident. SWR may lead to many serious consequences for power plant. Thus, it is a non-negligible factor to be considered in the design and operation of SFR. In this study, experiments on the interaction between liquid sodium and water vapor were carried out. The reaction phenomena, temperature of liquid sodium, morphology of reaction product and other characteristics of the chemical were summarized and analyzed in this paper. The experiment was conducted under different initial sodium temperatures (300–450 °C) and different mass fraction of water vapor (0.1–0.9 at 200 °C) conditions. Visualization scheme was used in this experiment and the reaction process was recorded by a high-speed camera. The results indicate that both mass fraction of water vapor and initial temperature of liquid sodium are important factors in the reaction process. The mass fraction of water vapor affects the actual reaction rate. The initial temperature determines the form of reaction products (liquid NaOH) on the surface of liquid sodium. For the experiments with initial temperature below 400 °C, the reaction products appear as bubbles and foams. While the initial experiment temperature exceeds 400 °C (including 400 °C), bubbles and foams gone, replaced by a thin film. By analyzing the conditions of bubble generation, the surface tension of liquid NaOH is an important cause, which can be affected by the temperature and bounding water molecules. Furthermore, according to the measurement results of sodium temperature, the reaction products in the form of a large concentration of foams have a strong blocking effect on mass transfer and greatly slow down the actual reaction rate. This research has important reference significance for the study of the mechanism of liquid sodium and water vapor reaction.

Crotonic Acid Production by Pyrolysis and Vapor Fractionation of Mixed Microbial Culture-Based Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Crotonic acid (CA) and trans-2-pentenoic acid (2-PA) can be obtained from renewable resources by pyrolysis of the bio-based poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymer. In this study, direct pyrolysis of the PHBV-enriched biomass into CA and 2-PA was studied under an inert atmosphere and N2 carrier gas flow, aiming at obtaining high acid yields from mixed microbial cultures (MMCs). The highest yields of 80 ± 2% for CA and 67 ± 1% for 2-PA were obtained at conditions of 240 °C, 1 h, and 0.15 L/min nitrogen flow rate, corresponding to a mean hot vapor residence time of 20 s. A similar acid yield was achieved when the pyrolysis was performed under reduced pressure (150 mbar) instead of using nitrogen gas. The combined pyrolysis of extracted PHBV at 220 °C and 90 min with vapor fractionation by distillation resulted in yields of 81 and 92% for CA and 2-PA, respectively.

Water-Use Strategies and Habitat Adaptation of Four Tree Species in Karstic Climax Forest in Maolan

The technique of stable hydrogen and oxygen isotope tracing has become an important means to study the mechanism of water movement due to its high sensitivity and traceability. In this study, four dominant tree species in the karst forest of Maolan, Guizhou Province, were selected, and their water-use strategies and the mechanism of maintenance of tree species diversity were investigated using the stable hydrogen and oxygen isotope tracing technique. The results show that: (1) The regional precipitation varied evidently with the alternation of seasons, i.e., the values of δD and δ18O in precipitation had a positive bias in spring and a negative bias in summer and autumn. The value of deuterium excess (d-excess) was between 11.67‰ and 31.02‰, with a mean value of 22.98‰. (2) The soil temperature (ST), soil water content (SWC) and precipitation, which have a significant positive correlation, imposed a joint impact on the dynamics of the soil evaporative fractionation. (3) The line-conditioned excess (LC-excess) varied seasonally in different water bodies, i.e., the relative evaporative fractionation of the rhizosphere soil of deciduous tree species was stronger than that of evergreen tree species, and the evaporative fractionation of hydrogen and oxygen isotopes in the leaf water of evergreen tree species was stronger than that of deciduous tree species in spring and summer. However, that of the latter was stronger than that of the former in autumn. (4) The soil water was the most important potential water source for dominant tree species in karst terrain (71%), followed by epikarstic water, which made up an effective supplement (29%). (5) Finally, trees of different life forms and species varied in capacity and proportion in terms of using the potential water sources in different seasons, i.e., deciduous tree species had a greater capacity for using water from potential sources and variable water-use strategies. This may be a major water-limiting mechanism that maintains photosynthesis in the leaves of evergreen tree species (leaves are evergreen and plants continue to grow via photosynthesis) and constrains photosynthesis in deciduous tree species (leaves fall and plants become dormant and stop growing). These results lead to the conclusion that the dominant tree species in karstic forests resist water stress and adjust water-use strategies towards each potential water source to adapt to the harsh karstic habitat through root plasticity and leaf defoliation.

Assessing the variations of evapotranspiration and its environmental controls over a subalpine wetland valley in China

Dynamics in long-term evapotranspiration (ET) and its controlling variables are essential for understanding how a high-altitude wetlands ecosystem responds to climate change. The rising temperature is expected to agitate the regional hydrological cycle and water balance, particularly in the subalpine wetland valley of Jiuzhaigou, located in the transition zone between the northeast Qinghai-Tibet Plateau and the Sichuan Basin, Southwest China. Here, we used growing season multi-year (2013–2021) Bowen ratio data to assess the variability in ET and its key controlling parameters at different timescales in Jiuzhaigou valley. This study also explored the ratio of ET to precipitation (P). The wetland daily mean ET varied from 0.06 to 6.77 mm d−1, with a mean value of 2.64 mm d−1 for the nine years. Fluctuations in daily ET were primarily driven by available energy (net radiation, Rn), explaining 86 % of the variation. Seasonal patterns in ET were largely similar to environmental parameters, i.e., Rn, air temperature (Ta), and vapor pressure deficit (VPD), peaking in August with an interannual monthly mean value of 3.48 mm d−1. Interannual monthly mean ET had a strong positive linear relationship with Rn, Ta, and VPD, while there was no significant correlation with P on a growing season basis. Furthermore, monthly ET was shown to be regulated by Ta largely in high-temperature months and minimally in low-temperature months. The growing season ET varied interannually, and the ET to P ratio (i.e., ET/P) ranged between 0.52 and 1.16. Interannual variation in annual ET was controlled by Ta and P, which individually explained 73 and 61 % of the variation, respectively. The multiple regression model indicated that Ta and P together elucidated 92 % of the variation in annual ET. The increased sensitivity (e.g., regression slopes) of ET to P over 2014–2021 indicates that ET consumed most of P, which leads to decreasing runoff and streams drying up. This study clarifies the temporal dynamics in ET for wetlands and its environmental controls at multiple timescales. It is demonstrated that the proportion of ET could increase in response to increasing temperature without an associated increase in P, affecting local water balance. These results could potentially contribute to sustainable water management in high-altitude wetlands and environmental planning under future climate change.

A study on the design of Waste Heat Recovery Unit (WHRU) for 30kW Organic Rankine Cycle (ORC) power system for ships

ABSTRACT As the improvement of ship energy efficiency is emphasized internationally, researches for this are being conducted in various ways. Accordingly, research is being conducted on the application of ORC power generation systems for ships using waste heat from the main engine exhaust gas generated during operation. The WHRU constituting the ORC system must be designed so that stable-phase change heat transfer occurs. In this study, a design study was conducted using the ANSYS CFX program for the production of a WHRU capable of generating ORC power generation output for a 30-kW ship using R134a refrigerant. A WHRU capable of achieving 30 kW generation output performance was designed while changing various design elements (shape, tube diameter, number of tubes, number of stages, etc.) of the WHRU. As a result, it was confirmed that the refrigerant (R134a) in a liquid state at a temperature of 14.8°C entered at a flow rate of 1.06 kg/s, evaporated by the exhaust gas, and was discharged from the outlet in a state of vapor fraction 1 at a temperature of 56.4°C. The heat transfer rate of the WHRU was 219.2 kW, the pressure during the evaporation process was constant at 13.9 bar in absolute pressure, and the enthalpy was 220 kJ/kg at the inlet and 426 kJ/kg at the outlet, respectively.

Исследование пластового флюида при разработке месторождений на шельфе Kарского моря

Introduction. With the expansion of offshore drilling and the distance of fields from the coastline, the number of production wells located in difficult underwater geological conditions is increasing, which complicates research. For example, the Yurkharovskoye field is located in a strip along the Tazovsky Peninsula under the waters of the Kara Sea. At the same time, the data obtained from the results of research are necessary when calculating reserves and designing the development of hydrocarbon deposits. Materials and research methods. Modeling of the operating conditions of the field under various thermodynamic conditions was carried out in order to determine the effect of water vapor and oil fractions on condensate losses during the development of the deposit [6–9]. The experiments were carried out to determine the amount of condensate in the reservoir gas, the physicochemical properties of hydrocarbons, and the effect of heavy oil fractions on condensate recovery [5, 10]. Prediction of condensate losses in the reservoir depending on the influence of negative factors must be taken into account when calculating hydrocarbon reserves and drawing up a field development project [11, 13]. Research results and their discussion. In the studied part of the section of the Yurkharovskoye field, located on the shelf of the Taz Bay, gas deposits were identified in the Aptian-Albian-Cenomanian complex and gas condensate deposits with oil rims in the Neocomian complex. The selection of development objects was based on a set of geological and geophysical data, the main of which are the presence of reservoirs and seals in the section and a single hypsometric position of the GWC or WOC in the case of an oil and gas condensate deposit. Correlation of well sections and identification of productive formations was based on the choice of benchmarks, the similarity of well logs, taking into account the nature of reservoir saturation and well test results. As a result of experimental PVT studies, the influence of water vapor and oil fractions as an integral part of the hydrocarbon system on the reservoir losses in the deposit was determined. The analysis of the performed studies confirmed that multicomponent hydrocarbon systems consist of a mixture of gas, condensate and water vapor, as well as oil fractions, which significantly changes the properties of the system and the dynamics of its phase processes during the development of the Yurkharovskoye field. Conclusions. The conducted PVT-experiments in order to identify the effect of water vapor and oil components that are part of natural gas showed that the predicted current and final condensate recovery factors are overestimated. An analysis of the research results revealed a different effect of water vapor on reservoir losses of hydrocarbons in the deposit due to an increase in partial pressure. In the presence of formation water in the gas condensate system, the CFC value decreased to 4-5%. Thus, the reason for the increase in reservoir losses of condensate in the deposit during the development of oil and gas condensate fields on the shelf of the Kara Sea was determined.

Large‐eddy simulation of soil moisture heterogeneity‐induced secondary circulation with ambient winds

AbstractLand surface heterogeneity in conjunction with ambient winds influences the convective atmospheric boundary layer by affecting the distribution of incoming solar radiation and forming secondary circulations. This study performed coupled large‐eddy simulation (ICON‐LEM) with a land surface model (TERRA‐ML) over a flat river corridor mimicked by soil moisture heterogeneity to investigate the impact of ambient winds on secondary circulations. The coupled model employed double‐periodic boundary conditions with a spatial scale of 4.8 km. All simulations used the same idealized initial atmospheric conditions with constant incident radiation of 700 W⋅m−2 and various ambient winds with different speeds (0 to 16 m⋅s−1) and directions (e.g., cross‐river, parallel‐river, and mixed). The atmospheric states are decomposed into ensemble‐averaged, mesoscale, and turbulence. The results show that the secondary circulation structure persists under the parallel‐river wind conditions independently of the wind speed but is destroyed when the cross‐river wind is stronger than 2 m⋅s−1. The soil moisture and wind speed determine the influence on the surface energy distribution independent of the wind direction. However, secondary circulations increase advection and dispersive heat flux while decreasing turbulent energy flux. The vertical profiles of the wind variance reflect the secondary circulation, and the maximum value of the mesoscale vertical wind variance indicates the secondary circulation strength. The secondary circulation strength positively scales with the Bowen ratio, stability parameter (−Zi/L), and thermal heterogeneity parameter under cross‐river wind and mixed wind conditions. The proposed similarity analyses and scaling approach provide a new quantitative perspective on the impact of the ambient wind under heteronomous soil moisture conditions on secondary circulation.

Comparative analysis of single and multiphase numerical frameworks for subcooled boiling flow in an internal combustion engine coolant jacket

Computational analysis of nucleate boiling occurring in liquid cooled applications, such as internal combustion engines is often implemented within a single phase Computational Fluid Dynamics (CFD) framework, owing to low vapor fractions involved. With increase in specific power and the resulting higher thermal loads, accounting for the presence of the vapor phase using a multiphase framework is required in certain conditions, despite the higher computational costs. While detailed resolution of the liquid and vapor phases in nucleate boiling using a two fluid model is excessively computationally expensive, the homogeneous mixture multiphase framework is a good compromise between resolution and computational cost. In this article a numerical wall boiling model is implemented within both, a single phase and the mixture multiphase frameworks. Results from the two approaches are compared with measurements in a channel flow. The results from both approaches are in good agreement with experiments. The single phase approximation is valid when the vapor generation is low. The sensitivity of the results to the computational grid is also discussed in detail. Further the two frameworks are used to simulate the heat transfer in the coolant jacket of a four-cylinder petrol engine. The results from the numerical simulations are compared with measurements. Both computational frameworks compare reasonably well with the measurements in terms of local metal temperature. However, the advantage of accounting for the vapor phase using the mixture multiphase framework is evident when the parameter related to vapor bubble interactions is analysed in detail. • The Blended Boiling Model is implemented within single phase and mixture multiphase frameworks in CFD. • Numerical results are validated with relevant experimental data in the literature. • The mixture multiphase framework is more accurate with increase in net vapor generation. • Excessive grid refinement leads to inaccurate results in both frameworks. • Heat transfer in passenger car engine is analysed using both frameworks and results are validated with test data.

Evaluating four remote sensing based models to estimate latent heat flux in semi-arid climate for heterogeneous surface coverage of western Algeria

Optimal estimation of water balance components at the local and regional scales is essential for many applications such as integrated water resources management, hydrogeological modelling and irrigation scheduling. Evapotranspiration is a very important component of the hydrological cycle at the soil surface, particularly in arid and semi-arid lands. Mapping evapotranspiration at high resolution with internalised calibration (METRIC), trapezoid interpolation model (TIM), two-source energy balance (TSEB), and soil-plant-atmosphere and remote sensing evapotranspiration (SPARSE) models were applied using Landsat 8 images for four dates during 2014–2015 and meteorological data. Surface energy maps were then generated. Latent heat flux estimated by four models was then compared and evaluated with those measured by applying the method of Bowen ratio for the various days. In warm periods with high water stress differences and with important surface temperature differences, METRIC proves to be the most robust with the root-mean-square error ( RMSE) less than 40 W∙m –2. However, during the periods with no significant surface temperature and soil humidity differences, SPARSE model is superior with the RMSE of 35 W∙m –2. The results of TIM are close to METRIC, since both models are sensitive to the difference in surface temperature. However, SPARSE remains reliable with the RMSE of 55 W∙m –2 unlike TSEB, which has a large deviation from the other models. On the other hand, during the days when the temperature difference is small, SPARSE and TSEB are superior, with a clear advantage of SPARSE serial version, where temperature differences are less important.