Horizontal Temperature Research Articles

Design and evaluation of an active vineyard heating system to simulate temperature increase in the context of climate change

The current study introduces an innovative direct and active heating system designed for precise temperature control in vineyards. This system serves as a valuable tool for investigating the influence of climate change on grapevine physiology and, consequently, the characteristics of the resulting wine. The research took place in an experimental vineyard located in Mendoza, Argentina, with V. vinifera cvs. trained to a vertical shoot positioning trellis system over two consecutive growing seasons. The system design utilized electric hot water tanks and polypropylene pipes attached to the foliage catch wires. Over two growing seasons, the system consistently elevated the ambient air temperatures within the canopy by 2.5 ± 0.12 °C compared to the control group. This temperature increase emulated the temperature projections for Mendoza as forecasted by the IPCC by the end of this century. The system displayed heating uniformity, as evidenced by the absence of both vertical and horizontal temperature gradients. Additionally, the significant variation in mean daytime and night-time temperatures between the control and heated treatments highlighted the effectiveness of the system in modifying temperature conditions on a diurnal basis. The heated treatment applied with this system proved to have an effective biological impact on the physiology of grapevines. In both seasons, plants under the heated treatment advanced their bud break and harvest dates. The study showed a significant growth enhancement in the heated treatment, with apical shoots extending significantly longer than those in the control treatment. Additionally, the total soluble solids content increased in the heating treatment, while yield decreased, for both experimental seasons. These results illustrate the robust performance of the system throughout the entire growth period, regardless of fluctuations in atmospheric conditions. This study establishes a new foundation for future research on grapevine responses to climate change. It also opens the door to the implementation of effective adaptation strategies in vineyards, promising a more resilient and adaptable future for grape cultivation.

Horizontal gradient effects on the flow stability in a cylindrical container in a Bèrnard–Marangoni problem

This study assesses the flow stability of the Bénard–Marangoni (BM) problem, a thermoconvective scenario occurring in an annular domain. The system is heated from below, with a linearly decreasing horizontal temperature profile from the inner to the outer wall. The top surface of the domain is open to the atmosphere, while the lateral walls are adiabatic. The analysis focuses on the effects of the Bond number, which represents capillarity or buoyancy effects, and the horizontal temperature gradient on the flow stability for three different Prandtl numbers, indicative of viscosity effects in fluids ranging from typical gases to n-butanol. Three different models for heat transmission to the atmosphere are also considered using the Biot number. The results indicate that, for the two largest Prandtl numbers (50 and 5), multiple competing solutions emerge in localized regions of the Bond–temperature gradient plane. The boundaries between these regions include co-dimension two points, where two solutions coexist, and at least one co-dimension three point for each Prandtl and Biot number combination. These transitions show a strong dependency on both the Bond and Prandtl numbers. Additionally, as anticipated, the solution space is more complex for the smallest Prandtl number (Pr=1), with seven competing solutions identified in the plane.

Research on a novel method of air distribution to create a uniform indoor environment in a long and narrow building

Because people work a long time in buildings, good indoor thermal environments and air distributions have attracted increased amounts of attention. To improve the indoor thermal environment and air quality, an effective ventilation strategy must be used. In the air conditioning of a building, the air distribution has been identified as a significant factor that affects the indoor thermal environment. A novel method for air distribution was presented to create a uniform indoor environment along the room length direction. In this study, numerical simulations were carried out to analyse the airflow pattern and performance of the sidewall air supply (SAS) and the sidewall air supply with deflector (SASD). Orthogonal experiments were conducted to study the airflow distribution law of the deflector. The ventilation performance of the two air supply modes was evaluated by air velocity distribution, temperature distribution, horizontal temperature difference, age of air, and other evaluation indicators. The results indicate that the horizontal air temperature differences in the SASD at three heights are 46.05%, 16.44%, and 26.51% lower than those in the SAS, which has a better energy-saving effect. Moreover, the indoor air distribution performance was obtained under three influencing factors: the gap width from the deflector to the ceiling, the horizontal position, and the length of the deflector. A better deflector optimization scheme was obtained. Experimental research was carried out to verify the indoor air distribution of the SASD. This research can provide a reference for the innovative design of indoor air supply systems

Resolution of the bidimensional shallow water equations with horizontal temperature gradients by a well Balanced Roe scheme

This work presents a numerical resolution of the two-dimensional Ripa system using Roe scheme. A discretization of the source term satisfying the conservation property is presented. The mathematical model is based on the ordinary shallow water equations in merging the horizontal temperature gradient. The numerical approach employs unstructured grids and integrates Runge–Kutta method and the minmod limiter to achieve second order accuracy in both time and space domains. A strategy of mesh adaptation based on temperature gradient is implemented to refine the study domain and gain in computational cost. Various numerical tests are conducted to verify the effeciency of the numerical method.

Process-Oriented Compound Long-Duration Dry and Hot Events in China: Atmospheric Conditions, Moisture, and Heat Budget Analyses

Abstract Summertime compound dry and hot events pose severe threats to agricultural production and human health, especially those with a long duration. Considering the joint evolution of such hazards in space and time, spatiotemporal compound long-duration dry and hot (SLDDH) events in China during 1961–2022 are identified with a process-oriented method. Here, we investigate the associated large-scale atmospheric circulation patterns and the physical processes causing their precipitation and temperature anomalies. In all regions of China, this persistent dry–hot compound extreme is accompanied by anomalous high pressure systems along with enhanced descending motion, increased net surface solar radiation, and decreased water vapor flux convergence. Moisture budget diagnosis shows that precipitation deficits during the SLDDH events are produced primarily by the suppressed vertical moisture advection associated with the dynamical contribution of anomalous subsidence, while the thermodynamic process due to the anomaly in atmospheric moisture content makes a small contribution. Horizontal temperature advection generally plays a negative role in sustaining SLDDH events, while it helps trigger the events in North China. In most regions, adiabatic warming due to abnormal subsidence plays a dominant role in determining the near-surface high temperatures during the long-lasting warm and dry periods, whereas diabatic heating has a cooling or small effect therein. However, in some northern areas such as North China and northern Xinjiang, hot extremes during SLDDH events arise from a combination of diabatic heating and adiabatic warming. This study thus quantifies and reveals the crucial factors leading to the severity of compound dry and hot events.

3D-Numerical simulation of free convection inside a cubical cavity filled with non-Newtonian-Bingham fluid

This work focuses on a numerical study of the natural convection of a non-Newtonian viscoplastic fluid within a cubic enclosure. The viscoplastic behavior is described by the Bingham model. The considered three-dimensional convective flow is confined within a cavity, subjected to a horizontal temperature gradient, where the vertical walls have two imposed temperatures while the rest of the walls are adiabatic. The Navier-Stokes equations, along with the mass and energy conservation equations, are numerically solved. Fluid flow and heat transfer characteristics are systematically studied over a wide range of Rayleigh numbers Ra (103 - 106) and Bingham number Bn (0 - 20). Finally, comparisons were made with previous results obtained in two dimensions in order to analyze the existence of a three-dimensional effect on the flow of the Bingham fluid. The results show that the Nusselt number decreases with the increase of the Bingham number, and for the large values ​​of the latter the heat transfer is done by conduction. It is also noteworthy that the critical Bn of the 2D model is higher than that of the 3D model, which confirms the existence of the three-dimensional effect. This is attributed to the presence of a wall along the Z axis which hinders and limits the flow of fluid within the enclosure.

GIS-based multi-criteria approach for ranking suitable areas for the implementation of PV-Powered MCDI desalination plants in the Rheris Watershed, Southeast Morocco

In Morocco's oases, which rely heavily on surface water from mountain sources, the threat of decreasing rainfall presents a significant challenge, leading to a decline in surface water availability. This study focuses on the Rheris Watershed in Southeast Morocco, where brackish water desalination emerges as a viable alternative to ensure sustainable water supply for agriculture. Prior to the deployment of a pilot plant integrating a desalination unit, selecting an optimal site for PV-powered MCDI desalination plants was critical. This selection was based on a range of criteria, including Groundwater Quantity, Global Horizontal Irradiation, Temperature, Evaporation, Water Salinity, Water Quantity, Well Density and Slope. These criteria were evaluated using a combination of the Analytical Hierarchy Process (AHP), and geospatial data obtained from Remote Sensing (RS) and Geographic Information System (GIS) techniques.This case study in the Rheris watershed identified potential sites for future Membrane Capacitive Deionization (MCDI) desalination projects, High suitability areas encompass 280.45 km² (30.91 %), located west of Tinejdad, Khettarat Moulay Hachem, north of Goulmima, and south of Tinghir. Low suitability areas cover 63.75 km² (7.02 % of the study area), including regions south of Tadighoust and Tinejdad. Moderate suitability areas span 562.86 km² (62.05 %), involving central regions of Goulmima, Tadighoust, Tinejdad, and Tinghir. Based on the results of the study, the recommendations include focusing on areas identified as highly suitable for MCDI technology for sustainable agriculture, refining selection criteria based on local data, exploring brine management strategies, and adopting integrated water management approaches to ensure sustainable resource use.

Spotting ignition of plastic foam by a fast-moving hot metal particle

Spotting ignition involves dynamic interaction between fuel bed and hot particles, but the scientific understanding of the ignition by a fast-moving hot particle is still limited. Herein, a hot steel particle with various horizontal velocities, temperatures, and sizes is shot to ignite vertically oriented low-density expandable polystyrene foam. A high-speed particle can directly get embedded into the foam to achieve flash-point, fire-point, or no ignition, while a low-speed particle bounces away from the foam without ignition. Results show that for a particle of 1150 °C, its minimum velocity for embedding is 12.00 m/s. Such a critical velocity for hot-particle embedded or ignition slightly decreases as particle temperature increases. Minimum ignition temperature of these high-speed particles is 200 °C higher than that of near-static or with a low free-fall velocity, due to the shorter residence time and insufficient to produce a flammable mixture. Moreover, when the particle is neither too slow to bounce away nor too fast to get embedded, it will be partially embedded on the sample surface to burnout the fuel, posing the biggest fire hazard. It deepens our knowledge of the complex interaction between hot moving particles and insulation foam to reduce spotting fire risk for building façade.

The thermal responses of composite box girder bridges with corrugated steel webs under solar radiation

Owing to the direct exposure to complex atmospheric environments, the temperature field of composite box girder bridge with corrugated steel webs (CBGB-CSW) is likely non-uniformly distributed. Whereas, the current researches regarding the thermal responses of CBGB-CSW are insufficient, and the thermal responses of CBGB-CSW under solar radiation are still unknown. Therefore, this paper conducted a long-term temperature experiment on a scaled model to explore the temperature distribution characteristics in CBGB-CSW. Meanwhile, a three-dimensional thermal–mechanical coupling Finite Element (FE) model is established to simulate the temperature field in the experiment girder. The accuracy and effectiveness of the developed FE model has been verified by the measured temperature data. Therewith, the thermal responses (i.e., stress and displacement) of a full-scale continuous CBGB-CSW with a span of 150 m are numerically investigated. The results indicate that the maximum stresses always occur at the midspan section (with a depth of 5 m) of the continuous CBGB-CSW, and considerable concentrations of stress are observed in the steel-concrete junction. The maximum longitudinal tensile and compressive normal stresses within 0.4 m of the upper junction can reach 5.55 MPa and −8.46 MPa respectively, and those of the lower junction can reach 6.96 MPa and −7.05 MPa respectively. Besides, owing to the impacts of vertical and horizontal temperature gradients, significant displacements of the whole bridge can also be observed. The maximum vertical displacement (5.33 mm) of the CBGB-CSW is estimated at the top plate in the midspan, while the maximum horizontal displacement (0.74 mm) is estimated at the trough of the southern corrugated steel web in the midspan. Notably, the outcomes of this paper can provide some useful references for engineers and scholars to understand the thermal responses of the CBGB-CSW.

Modelling and Analysis of Evacuated Tube Solar Collector Working with Hybrid Nanofluid

This research study is concerned with developing a mathematical model for an Evacuated Tube Solar Collector (ETSC) that utilizes a Hybrid Nanofluid flow in a manifold. The model consists of a set of the partial differential equations that, using the dimensional analysis approach, are reduced to a dimensionless system. The exact solution method, assisted by the Mathematica program, is used to solve the system. The study examines the impact of certain factors on flow and heat transmission, including horizontal velocity, temperature variation, heat source, magnetic field, Prandtl Number, and Eckert Number, and provides a detailed analysis of the results. The key findings of the analysis revealed that an increase in hybrid nanoparticle volume effects in a reduce in velocity and heat transfer coefficient. Additionally, elevated heat source and Prandtl number correspond to an increased heat transfer coefficient.

Influence of atmospheric stability conditions on wind energy density in Ali Al-Gharbi region of Iraq

Atmospheric stability is considered as one of the most important factors affecting the increase or decrease in wind speed in the atmosphere and thus affects the wind energy density. This study aims to analyze the stability of the atmospheric conditions in southern part of Iraq, specifically in the Ali Al-Gharbi region, using one of methods to determine atmospheric stability called Monin-Obukhov length . Field data of horizontal and vertical wind speed and air temperature collected at three heights (10m, 30m, and 50m) in 2017 from tower installed in Ali Al-Gharbi region. The results show that the vertical wind speed increases with height up to 30 m and decreases at 50 m, while the horizontal wind speed increases as the height increases. The friction velocity , surface heat flux , momentum flux and shear stress were calculated and the stability conditions were determined. Results revealed that stable atmospheric condition was the most frequent with about 59% occasions occurring during the year followed by unstable (40%) and neutral (1%) conditions. The highest wind energy density was in stable conditions (0 ≤ L< 200), with percentage (58% - 57%) in spring season at both heights 10m and 50m, respectively, followed by unstable conditions (-200 < L ≤ 0), while the lowest wind energy density was in neutral conditions (-200 ≤ L ≥ 200) with percentage (1.3% - 0.8%) in autumn season.Atmospheric stability is considered as one of the most important factors affecting the increase or decrease in wind speed in the atmosphere and thus affects the wind energy density. This study aims to analyze the stability of the atmospheric conditions in southern part of Iraq, specifically in the Ali Al-Gharbi region, using one of methods to determine atmospheric stability called Monin-Obukhov length . Field data of horizontal and vertical wind speed and air temperature collected at three heights (10m, 30m, and 50m) in 2017 from tower installed in Ali Al-Gharbi region. The results show that the vertical wind speed increases with height up to 30 m and decreases at 50 m, while the horizontal wind speed increases as the height increases. The friction velocity , surface heat flux , momentum flux and shear stress were calculated and the stability conditions were determined. Results revealed that stable atmospheric condition was the most frequent with about 59% occasions occurring during the year followed by unstable (40%) and neutral (1%) conditions. The highest wind energy density was in stable conditions (0 ≤ L< 200), with percentage (58% - 57%) in spring season at both heights 10m and 50m, respectively, followed by unstable conditions (-200 < L ≤ 0), while the lowest wind energy density was in neutral conditions (-200 ≤ L ≥ 200) with percentage (1.3% - 0.8%) in autumn season.

Thermal Imprints of Mesoscale Eddies in the Global Ocean

Abstract Mesoscale eddies have been widely documented for their significant role in regulating oceanic heat absorption and redistribution. However, our understanding of their thermal impacts on a global scale has been hampered by the scarcity of eddy-targeted observations. Here, we perform a comprehensive global analysis of over 2 million historical hydrographic profile measurements collocated with satellite-based eddy observations between 1993 and 2019, revealing rich geographical variability in the intensity, vertical extent, and asymmetry of the temperature anomalies induced by eddies. In tropical and subtropical oceans, temperature anomalies within eddies are dominated by eddy pumping and heavily influenced by near-surface vertical stratification, resulting in a relatively shallow extent of eddy effects (around 500 m) with subsurface maximum temperature anomalies occurring near 100 m. In midlatitude main current systems with sharp horizontal temperature gradients, the impact of eddy trapping becomes evident, leading to temperature anomalies extending to depths of 1000 m, with vertical peak values exceeding 4°C between 300 and 700 m, equivalent to perturbations in the local mean-state temperature of nearly 30%. This process also results in substantial temperature anomalies on isopycnal surfaces, indicating notable cross-frontal transport of heat and water mass with varying properties. The estimated meridional heat transport by eddy movement is on the order of O(1) MW, generally one order of magnitude smaller than previous estimates of the time-varying meridional heat transport (). However, this does not imply that they are unimportant, as this long-range cross-frontal heat transport may have significant consequences on regional temperature extremes and biogeochemical environments. Significance Statement Mesoscale eddies with a horizontal scale of O(100) km play a crucial role in modulating oceanic heat absorption and redistribution. However, their activities vary significantly across the global ocean, and our understanding of their thermal impacts remains incomplete. In this study, we conduct a global analysis of the influence of eddies on ocean temperature using over 2 million historical in situ temperature and salinity profile measurements combined with satellite-based eddy observations. Our analysis reveals substantial regional variability in the intensity, vertical extent, and asymmetry of temperature anomalies within eddies of different polarities and discusses the underlying mechanisms. Additionally, we estimate the meridional heat transport caused by eddy movement within each 2° × 2° grid, providing insights into the efficient pathways for eddy heat transport in western boundary currents and their extensions. These results enhance our understanding of the global-scale thermal impact of eddies and provide valuable references for assessing their biogeochemical and ecological consequences.

Impact of the Tibetan Plateau on Global High-Frequency Temperature Variability

Abstract The Tibetan Plateau’s (TP) topography has long been recognized for its impact on climate. However, recognition of the influence of the TP on global weather variability remains insufficient. Therefore, this study used numerical simulations to demonstrate the influences of the TP and its mechanical and thermal forcing on global high-frequency temperature variability and eddy kinetic energy (EKE). Despite local influences, the TP influenced the high-frequency temperature variability in far-flung regions like North America. In summer, the TP’s influence on high-frequency temperature variability showed dipole patterns in Eurasia and tripole patterns in North America, which were mainly induced by TP thermal forcing. In winter, the TP’s influence on high-frequency temperature variability was dominated by mechanical forcing and was less significant for remote regions than in summer. Mechanical forcing dominated EKE in both summer and winter. Furthermore, the horizontal temperature advection dominated the TP’s influence on high-frequency temperature variability for both its thermal effect in summer and its mechanical effect in winter, wherein EKE, as the dynamical factor, determined the horizontal temperature advection rather than the thermodynamical factor, the temperature gradient. Our findings suggest that the TP, via its mechanical and thermal forcing, may have an impact on temperature-related weather extremes around the world. Significance Statement The Tibetan Plateau (TP), being one of the world’s largest topographies, has been demonstrated to influence both paleoclimatic evolution and contemporary climate variability. However, the effect of TP on global weather variability has not been thoroughly studied. Therefore, this study looked into the effect of the TP on global high-frequency temperature variability. The TP’s overall, mechanical, and thermal effects on high-frequency temperature variability and EKE were specifically demonstrated. To get insights into dynamics, the physical processes underpinning the TP’s influence on high-frequency temperature variability were further clarified. This study contributes to a better understanding of the effects of large-scale topography on global high-frequency temperature variations, as well as relevant weather extremes.

Obvious difference of dominant circulation patterns between dry‐type and humid‐type heatwaves in North China

AbstractBased on the observed maximum temperature (Tmax), relative humidity (RH) and NCEP/NCAR reanalysis data during 1981–2021, basic temporal features and dominant atmospheric circulation patterns of dry‐type and humid‐type heatwaves in North China are investigated and compared. Statistical results indicate the dry heatwaves occur mainly in early summer (from early June to early July), that is, before the rainy season of North China, while the humid heatwaves have a high frequency in mid‐July to mid‐August. During the research period, the increasing trend of dry heatwaves is 0.67 days·decade−1, while the humid heatwaves increase at a greatly higher rate of 1.85 days·decade−1. For the dry heatwave, a high ridge in the subtropical westerlies plays the main role, and the northerly wind in the east of the ridge reduces the air moisture convergence over the region. However, for the humid heatwave, the westward and northward propagations of the western Pacific subtropical high (WPSH) may make the major contribution, and the southerly wind anomalies in the west of the WPSH enlarge the water vapour to the region. The adiabatic heating in subsiding air at all levels and horizontal temperature advection at lower troposphere are stronger for dry heatwaves than for humid heatwaves, which cause a higher Tmax for the former type. These results highlight the diversity of the heatwaves in North China, which suggests that multiple local and large‐scale subseasonal circulations should be considered to improve the subseasonal to seasonal forecast skills for heat extremes.

Influence of thermal radiation and magnetic field on convective transfer within an inclined square enclosure filled with Cu-water nanofluid

The present work investigates the effects of thermal radiation and magnetic field on the laminar convective transfer process on copper-based nanofluid within an inclined square enclosure. The studied configuration is a rigid-walled cavity subjected to a horizontal temperature gradient where the left wall is maintained at a hot temperature Th and subjected to a magnetic field B0. In contrast, the right wall is kept at a cold temperature Tc. The horizontal walls are adiabatic. The dimensionless governing equations are solved using the finite difference method and the UPWIND scheme to solve the convective terms. Formulated using the stream function, vorticity, and temperature. Effects on mean Nusselt numbers are investigated at different Rayleigh numbers 104,105,106, Hartmann numbers HA=0to100, tilt angles γ=0,π/6,π/4andπ/3, nanofluid volume fractions 0%≤φ≤6% and different radiation parameters ( Rd=0,1,2,3 ). The findings show that the HTR increased 3.6 times by augmenting the Ra from 104 to 106. Also, increasing the Ha number from 0 to 100 causes an 83.16% reduction in the HTR. Considering the radiation mode of heat transfer causes an increase in HTR. The average Nusselt values increase by 59.72% for the concentration of 6% while increasing the radiation parameter from 0 to 3. On the other hand, an increase in volume fraction leads to a deterioration in mean Nusselt numbers (Numean).

Compressible and anelastic governing-equation solution methods for thermospheric gravity waves with realistic background parameters

Abstract abstract A previously developed numerical-multilayer modeling approach for systems of governing equations is extended so that unwanted terms, resulting from vertical variations in certain background parameters, can be removed from the dispersion-relation polynomial associated with the system. The new approach is applied to linearized anelastic and compressible systems of governing equations for gravity waves including molecular viscosity and thermal diffusion. The ability to remove unwanted terms from the dispersion-relation polynomial is crucial for solving the governing equations when realistic background parameters, such as horizontal velocity and temperature, with strong vertical gradients, are included. With the unwanted terms removed, previously studied dispersion-relation polynomials, for which methods for defining upgoing and downgoing vertical wavenumber roots already exist, are obtained. The new methods are applied to a comprehensive set of medium-scale time-wavepacket examples, with realistic background parameters, lower boundary conditions at 30 km altitude, and modeled wavefields extending up to 500 km altitude. Results from the compressible and anelastic model versions are compared, with compressible governing-equation solutions understood as the more physically accurate of the two. The new methods provide significantly less computationally expensive alternatives to nonlinear time-step methods, which makes them useful for comprehensive studies of the behavior of viscous/diffusive gravity waves and also for large studies of cases based on observational data. Additionally, they generalize previously existing Fourier methods that have been applied to inviscid problems while providing a theoretical framework for the study of viscous/diffusive gravity waves. Graphic abstract

KHz Rate Fs/Ps-CARS Thermometry For Supersonic H_2/Air Combustion Studies

Accurate flow field measurements are essential to probe the phenomena involved in aeronautical engines undergoing high temperature and high turbulences. Indeed, reliable experimental datasets are needed to compare and validate numerical models. Among other laser diagnostics, Coherent Anti-stokes Raman Scattering (CARS) is a well-established non-linear spectroscopic technique used to probe harsh environments, since it provides non-intrusive local point measurements of chemical composition and temperature. We report here hybrid fs/ps Coherent Anti-Stokes Raman Scattering (fs/ps-CARS) thermometry campaign performed on N 2 in a supersonic H2 /air combustion. We used a mobile and compact laser architecture that shapes, synchronize and generates the laser beams necessary for CARS spectroscopy. The instrument was moved to a large-scale facility representative of a scramjet combustor (ONERA LAERTE/LAPCAT-II bench). H2 /air was injected during several burst at 0,12 and 0,15 equivalent ratios. Using kHz single-shot measurements combined with motorized translation stages, spatial and temporal resolution were obtained to probe the flow and the combustion at various positions upstream and downstream the hydrogen injectors. At these positions, horizontal and vertical temperature profiles were retrieved and compared with a numerical unsteady fluid dynamic simulation using delayed detached eddy simulations (DDES) developed at ONERA (CEDRE). The position of the combustion inside the combustion chamber could be identified through several horizontal and vertical profile temperature measurements. The signal-to-noise ratio of the detection was optimized by empirically adjusting the number of averaged laser shots based on the level of flow turbulence. For instance, far downstream the H2 injection, averaging over 10 to 100 pulses was possible as the heated air flow was steady. This was confirmed by the good agreement with numerical simulations although some distortion could still be observed and will be used to adjust the numerical simulation algorithm. However, averaging was no longer possible close to the injectors, where a highly turbulent H2 /air combustion was observed. Nevertheless, taking advantages of the high rate single-shot capacity of the spectroscopic technique, temperature could still be retrieved inside this area. These measurements provided a valuable experimental database for comparing and refining computational fluid dynamics modeling.

Evaluation of heat transfer conditions during polydisperse gas–solid flow in an industrial fluidised bed reactor

Knowledge of heat transfer conditions in large-scale circulating fluidised bed reactors plays an essential role in their proper design and optimization of theirs. This work presents an evaluation of the heat transfer conditions taking into account the coordinate height of the furnace chamber and the fluidised bed flow regime in the reactor. Experimental tests used method and measurement technique that provides reliable temperature data. The vertical and horizontal temperature profiles were obtained at different 966MWth fluidised bed reactor operating conditions. Four characteristic areas can be distinguished in the furnace chamber: the bottom region with a high-temperature gradient from 10.6 °C/m to 22.7 °C/m; the dense region with a medium temperature gradient from 4.7 °C/m to 7.3 °C/m; the dilute area with the lowest temperature gradient from 0.7 °C/m to 3.1 °C/m and the exit region with a temperature gradient (4.3 °C ≤ grad T ≤ 9.6 °C) similar to dense region. The horizontal temperature profiles confirmed a core-annular flow structure inside the furnace chamber. At the pressure drop below 5 kPa, the low variation of average temperature (from ±0.7 °C to ±4.2 °C) inside the furnace chamber of the CFB reactor was observed. As a result of fly ash recirculation of 3.86 kg/s, the lowest temperature gradient 0.2 °C/m was achieved in the bottom region of the furnace chamber. In the range of bed material circulation rates of 32 to 68 were registered temperature fluctuations 115 °C. The experimental results also showed the variation of the bed temperature was small and kept at a very low level of ±13 °C whereas the fluidised bed reactor was operated with a fluidisation velocity range of 1.8 to 2.4. Obtained findings provide unique data on heat transfer conditions in industrial facilities and thus fill the gap in literature data for CFB reactors. Based on main tests carried out in a large-scale CFB reactor, it can be concluded that detailed experimental data on thermal conditions provide important information to validate guidelines and for verifying empirical relationships, which are used in the design, optimization, and scaling of heat transfer surfaces in commercial fluidised bed reactors.

A junction temperature model based on heat flow distribution in an IGBT module with solder layer voids

The presence of voids in a solder layer affects the thermal reliability of an insulated-gate bipolar transistor (IGBT). In this work, the effects of the size and fraction of solder layer voids and the power losses of chips on heat flow distribution, junction temperature and thermal resistance were investigated. It was found that it was difficult for the heat to flow through the voids due to the high thermal resistance of air. Therefore, the heat above the voids could only flow horizontally, and then avoid the voids and move downward in the solder layer and the following layers, leading to a temperature difference in the surface chip layer. An improved junction temperature model based on the heat flow distribution (HD) considering the solder layer voids was established, the horizontal thermal resistance and horizontal heat capacity are introduced to characterize the effect of the solder layer voids, and the parameter extraction method was proposed. The temperature difference on the surface of the module increased with the increase of the void fraction, and when the void fraction increased from 0 % to 40 %, the surface temperature difference increased from 9.591 °C to 109.86 °C. The results showed that the proposed model not only had a higher accuracy in the estimation of the junction temperature compared with the traditional Cauer model and the improved Cauer model, but also monitored the horizontal temperature differences in the chip layer precisely.

Hydrodynamic modeling of floodplains with inundated trees and floating plants

Hydrodynamic influences of inundated forests and floating plants, common on floodplains, include modifying exchange flows and thermal structure. This study added algorithms to represent these plants in a three-dimensional hydrodynamic model, applied the model to a tropical floodplain, and validated the results with high resolution field measurements. The simulations reproduced temporal and spatial variation of thermal structures in vegetated and open water areas and demonstrated that vertical and horizontal temperature gradients were enhanced in the presence of vegetation. The study extends research findings obtained from laboratory experiments to in-situ situations and to vegetation not represented in the laboratory. The results are relevant to lateral and vertical exchanges of dissolved gases and solutes, and indicate that loss of inundated forests could lead to enhanced lateral exchange.