Surface Heat Research Articles

Equivalence Ratio-Driven Flame Response of an Industrial Premixed Burner: Experiments and Modeling

Abstract This paper presents an analysis of the unsteady heat release rate response of premixed flames to equivalence ratio perturbations for an industrial premixed swirl-based burner. During this investigation, perfectly and technically premixed flames were acoustically forced via fuel/air mixture flow and air flow modulations, respectively, at the same operating conditions. From the resulting flame transfer functions (FTFs), measured using the multimicrophone method, the equivalence ratio driven FTF was isolated and extracted by removing the velocity driven component, i.e., the measured FTF from the perfectly premixed flame, from the technically premixed FTF with two novel extraction techniques. The results are compared with FTFs obtained directly in a previous experimental campaign where the fuel flow was acoustically forced, the resulting equivalence ratio fluctuations measured via an infrared absorption technique, and the heat release rate response to the forcing was quantified using chemiluminescence measurements. The results from both measurement approaches agreed well highlighting the validity of the techniques. Further, to understand the governing features of the equivalence ratio driven FTF, a physics-based analytical model following the G-equation approach was developed. The contributions from flame surface area, flame speed, and heat of reaction oscillations were modeled to describe the heat release rate dynamics. A limited number of physical parameters in the analytical model were anchored on one test condition, optimized and restricted to values, which were all physically reasonable, and were subsequently used for model predictions at other operating conditions. The FTF model predictions compared well with experimental data across a range of different operating conditions. Finally, the relative contributions from flame surface area, flame speed, and heat of reaction oscillations on the features of the FTFs were identified and explored.

How Severe Was the 2022 Flash Drought in the Yangtze River Basin?

Flash droughts, characterized by their rapid onset and severe impacts, have critical implications for the ecological environment and water resource security. However, inconsistent definitions of flash droughts have hindered scientific assessments of drought severity, limiting efforts in disaster prevention and mitigation. In this study, we propose a new method for explicitly characterizing flash drought events, with particular emphasis on the process of soil moisture recovery. The temporal and spatial evolution of flash droughts over the Yangtze River Basin was analyzed, and the severity of the extreme flash drought in 2022 was assessed by comparing its characteristics and impacts with those of three typical dry years. Additionally, the driving factors of the 2022 flash drought were evaluated from multiple perspectives. Results indicate that the new identification method for flash droughts is reasonable and reliable. In recent years, the frequency and duration of flash droughts have significantly increased, with the Dongting Lake and Poyang Lake basins being particularly affected. Spring and summer were identified as peak seasons for flash droughts, with the middle reaches most affected in spring, while summer droughts tend to impact the entire basin. Compared to 2006, 2011, and 2013, the flash drought in 2022 affected the largest area, with the highest number of grids experiencing two flash drought events and a development rate exceeding 15%. Moreover, the summer heat in 2022 was more extreme than in the other three years, extending from spring to fall, especially during July–August. Its evolution was driven by the Western Pacific Subtropical High, which suppressed precipitation and elevated temperatures. The divergence of water vapor flux intensified water shortages, while anomalies in latent and sensible heat fluxes increased surface evaporation and heat transfer, further disturbing the regional water cycle. This study provides valuable insights for flash drought monitoring and early warning in the context of a changing climate.

Flow behavior and heat transfer characteristics of liquid film on vertical hot surface by inclined jet impingement

In this study, the flow behavior and heat transfer characteristics of the liquid film on the hot wall by inclined jet impingement are experimentally studied in detail. The effects of jet parameters, such as jet inclination angle, impingement distance, jet Reynolds number (Rej), and nozzle diameter are explored. The liquid film flow is visualized using a high-speed camera, and the surface temperature and heat flux are obtained by solving the inverse heat conduction problem. The results indicate that the liquid film shape is strongly affected by jet inclination angle but is almost unaffected by other parameters. As the inclination angle increases, the liquid film shape changes from elliptical to fusiform. In addition, the onset, enhancement, and disappearance of boiling cause the expansion and contraction of liquid film. The splashing rate is barely affected by jet parameters and remains within the range of 80–95 % under all conditions. The propagation of wetting fronts exhibits anisotropy. Except for the impingement distance, the position of wetting fronts along y-axis direction displays a high dependence on all parameters. The Rej and nozzle diameter have a significant effect on the heat flux at the impingement point and parallel flow zone, while the jet inclination angle and impingement distance only effect the impingement point. The visualization image proves that the droplet impingement pattern is the main reason for the increase in heat flux at higher impingement distances. Optimizing jet parameters can promote the wall to enter the rapid cooling stage in advance and increase maximum heat flux, thereby improving the maximum cooling capacity of the jet. Finally, an empirical equation is proposed to predict the maximum Nusselt number.

Carbonization of Refuse-Derived Fuel Pellets with Biomass Incorporation to Solid Fuel Production

In this work, dry carbonization (DC) and hydrothermal carbonization (HTC) of refuse-derived fuel (RDF) pellets were conducted to evaluate the physical, chemical, and fuel properties of the produced chars. In the dry carbonization tests, biomass sawdust was incorporated in different proportions on the samples to minimize agglomeration caused by the melting of the plastic fraction. The experiments were carried out in a temperature of 400 °C (DC) and 250–300 °C (HTC), in a residence time of 30 min. The respective chars and hydrochars were characterized according to their mass yield, apparent density, proximate, elemental, and mineral composition, chlorine content, high heating value, thermogravimetric profile, and surface functional groups. The results showed that the dry carbonization of RDF pellets with biomass incorporation, followed by a washing step, resulted in the production of chars with improved properties such as higher fixed carbon and higher heating value (HHV) (25–26 MJ/kg) and lower ash and chlorine content. Additionally, the HTC experiments demonstrated that hydrochars showed improved properties without the need for biomass addition and washing, however, with no significant difference in the HHV (20–21 MJ/kg). Therefore, DC of RDF pellets with 10% biomass incorporation seems to be a promising option to overcome the constraints of RDF utilization as an alternative fuel.

Evaluation of the Predictive Capability of CMA Climate Prediction System Model for Summer Surface Heat Source on the Tibetan Plateau

Surface heat source (SHS) is a crucial factor affecting local weather systems. Particularly SHS on the Tibetan Plateau (TP) significantly influences East Asian atmospheric circulation and global climate. Accurate prediction of summer SHS on the TP is of urgent demand for economic development and local climate change. To evaluate the performance of SHS on the TP, the observed SHS data from the eleven sites on the TP verified against CRA40-land (CRA) is evidenced significantly better than ERA5-land (ERA5), another widely used reanalysis. The predictive capability of the CMA Climate Prediction System Model (CMA-CPS) for SHS on the TP was assessed using multiple scoring methods, including the anomaly correlation coefficient and temporal correlation coefficient, among others. Furthermore, relative variability and trend analysis were conducted. Finally, based on these assessments, the causes of the biases were preliminarily discussed. The CMA-CPS demonstrates a reasonable ability to predict the spatial distribution patterns of SHS, sensible heat (SH), and latent heat (LH) on the TP in summer. Specifically, the prediction results of SHS and LH exhibit an “east-high and west-low” distribution, while the distribution of the predicted SH is opposite. Nevertheless, the predicted values are generally lower than CRA, particularly in interannual variations and trends. Among the predictions, LH exhibits the highest temporal correlation coefficients, consistently above 0.6, followed by SHS, while SH predictions are less accurate. The spatial distribution and skill scores indicate that LH on the TP contributes more significantly to SHS than SH in summer. Furthermore, discrepancies in the predictions of surface temperature gradients, ground wind speed, and humidity on the TP may partly explain the biases in SHS and their components.

Compound Tropical Cyclone Heat (TC‐Heat) Hazard in Hong Kong: Amplifying Urban Heat Extremes With Storm Position‐Driven Peripheral Warming and Urban Footprint

AbstractCompound hazards involving tropical cyclones and extreme heat (“TC‐heat”) have rarely been examined in prior research. Peripheral subsidence associated with cyclones can warm an area to varying degrees, depending on the cyclone's strength and position. Meanwhile, the peripheral airflow also overwhelmed the land‐sea breeze circulation system in coastal cities and favored downwind urbanized heat advection on the Southern China coastline. Here, we systematically applied ERA5 global reanalysis data, local surface‐level observations, MODIS‐based land‐cover data and HYSPLIT backward trajectories to evaluate how the position of distant TCs may divert the monsoon system and foster the surface heat advection from upwind urban agglomerate amplifying air temperature in downwind coastline. The analysis suggests when a distant TC is situated in a favorable area (the vicinity of Taiwan and Luzon Strait) at roughly 500–1,250 km to the east of Hong Kong, it forms a unique meteorological condition which allows the surface heat transport from the Greater Bay Area to Hong Kong, reflecting that regional build‐up of heat could be an important mechanism for producing local heat extremes.

Influences of heat flow on corrosion behavior and interfacial reaction kinetics

Heat transfer surface of heat exchange devices often suffers from severe corrosion, and their corrosion behavior is dramatically influenced by both surface temperature and heat flow. In this work, a novel heat transfer interface corrosion testing system was designed and built based on a simulation calculation analysis (COMSOL Multiphysics 6.0 software). By the aid of it, effects of different heat flux on corrosion performance of steel Q235 was investigated through mass loss and electrochemical methods in 0.5 mol/L H2SO4 solution at controlled interface temperatures. Results indicate that variations in concentration and temperature impose a great contribution to corrosion rate but not corrosion mechanism. However, heat flow not only changed the concentration of reactants near the interfacial surface but also affected the rate and kinetic mechanism of corrosion. Positive heat flow could reduce corrosion rate of heat transfer surface, while negative heat flow increased corrosion rate. Heat flow significantly altered parameters of the corrosion reaction rate constant (such as pre-exponential factor, activation energy, entropy change, and enthalpy change), and an approximate exponential relationship between corrosion rate and heat flux was proposed.

Interdecadal Variation in the Impact of Arctic Sea Ice on El Niño–Southern Oscillation: The Role of Atmospheric Mean Flow

Abstract This study reveals the remarkable interdecadal changes in the influence of boreal winter Arctic sea ice concentration (SIC) anomalies (ASICAs) in the Greenland–Barents Seas on the subsequent El Niño–Southern Oscillation (ENSO) development. Winter ASICA is strongly associated with the subsequent winter ENSO before the late 1980s and after the late 2000s, but their connection is weak during the 1990s and the 2000s. The interdecadal variations in the influence of ASICA on ENSO are associated with changes in the spatial structure of the ASICA-induced North Pacific atmospheric anomalies. During high-correlation periods, winter SIC increases in the Greenland–Barents Seas lead to tropospheric cooling via the suppression of upward surface heat fluxes, which further trigger an atmospheric teleconnection from the Arctic to the North Pacific. The accompanying North Pacific Oscillation–like atmospheric anomalies result in sea surface temperature (SST) warming in the subtropical North Pacific, which extends southward into the tropical Pacific via wind–evaporation–SST feedback and leads to surface westerly anomalies over the tropical western Pacific in the following summer. The tropical western Pacific westerly wind anomalies impact the subsequent ENSO development via triggering positive Bjerknes air–sea interaction. During low-correlation periods, atmospheric anomalies over the North Pacific generated by the winter ASICA are located more northward and cannot induce marked subtropical North Pacific SST anomalies and thus have a weak impact on the following ENSO development. Numerical experiments suggest that the interdecadal variation in the spatial structure of the North Pacific atmospheric anomalies induced by the winter ASICA is partly attributed to change in the atmospheric mean flow. Significance Statement Arctic sea ice is an important component of the global climate system. Studies have shown that Arctic sea ice has decreased significantly in recent decades, which is considered to be one of the most important responses of Earth’s climate system to global climate change. A number of studies have shown that Arctic sea ice anomalies have significant impacts on weather and climate over mid–high latitudes through tropospheric and stratospheric processes. Recent studies have suggested that the effects of Arctic sea ice anomalies could extend to the tropics via air–sea interactions. El Niño–Southern Oscillation (ENSO) is the strongest air–sea coupled system in the tropics and can have a significant impact on climate over the globe. ENSO is also considered to be one of the most important sources of subseasonal–seasonal climate predictability over many parts of the globe. It is therefore important to study the factors for the ENSO occurrence. A recent study showed that Arctic sea ice anomalies during boreal winter in the Greenland–Barents Seas have a significant impact on the following winter ENSO. In this study, we further reveal that the influence of winter Arctic sea ice anomalies in the Greenland–Barents Seas on the subsequent ENSO is unstable and has undergone significant interdecadal variation. We then investigate the mechanisms underlying the interdecadal variation via observational analysis and numerical simulations. The results of this study not only have implications for improving the prediction of ENSO but also could improve our understanding of the physical link between high-latitude climate systems and tropical air–sea coupling systems.

The Relative Importance of Ocean Advection and Surface Heat Fluxes During the Madden–Julian Oscillation in a Coupled Ocean–Atmosphere Model

AbstractIntraseasonal variability of ocean surface mixed layer temperature (MLT) in the tropics can be linked to the Madden–Julian Oscillation (MJO), the main source of intraseasonal atmospheric variability in the tropics. Here, we conduct a boreal winter mixed layer heat budget using 10‐day forecast composites of a coupled ocean–atmosphere Numerical Weather Prediction model of the UK Met Office to reveal that ocean advection plays a major role in modulating intraseasonal anomalies of MLT over the tropical Indian Ocean and the Maritime Continent. Large scale ( 10) intraseasonal anomalies of MLT ( 0.1 C) are driven by net surface heat flux. Ocean advection dominates at smaller horizontal scales ( 1), contributing up to 0.5 C to the intraseasonal MLT anomaly. Prior to the development of the enhanced MJO convection in the western Indian Ocean (phases 8 and 1), ocean advection reinforces the net heat flux warming in this region. However, ocean advection opposes the net heat flux warming in the Maritime Continent prior to the development of suppressed MJO convection in this region. When the MJO convection develops over the central Indian Ocean (phase 3), ocean advection (net surface heat flux) drives the intraseasonal MLT anomalies in the western Indian Ocean (central Indian Ocean and the Maritime Continent). Our results demonstrate the importance of ocean dynamics during the initiation and growth of the MJO, and raise implications for models that do not resolve these processes.

Investigating the Impact of Multiphysics on Modeled Planetary Boundary Layer Height Estimates during the PECAN Field Campaign

Abstract Accurate representation of the planetary boundary layer (PBL) in numerical weather prediction is crucial to air quality, weather forecasting, and climate change research and operations. Here, we evaluate the estimates of PBL height (PBLH) from a set of convective-permitting simulations conducted using the Weather Research and Forecasting (WRF) Model during the Plains Elevated Convection at Night (PECAN) campaign (from June to mid-July 2015). Our analysis aims to quantify the variability in PBLH, along with its associated surface variables and atmospheric profiles, to gauge the influence of model physics on the accuracy of simulated PBL properties. Specifically, we conducted twenty-four 45-day retrospective simulations encompassing different combinations of three PBL and two microphysics schemes, two initial and boundary condition (ICBC) datasets, and two model vertical grid spacings. We compare these simulations with measurements from surface sites and radiosonde launches across four sites in the southern Great Plains during PECAN. Our findings indicate that deriving PBLH from modeled atmospheric profiles yields a narrower spread (200–300 m) compared to PBLH calculated from the model’s PBL scheme (400–500 m) relative to radiosonde-derived PBLH under fair weather conditions. The choice of PBL scheme and ICBCs exerts the most significant impact (by up to 400 m) on the spread of modeled PBLH and associated atmospheric profiles, primarily influencing the representation of surface heating, transport, and mixing processes in the model. The model has difficulty reproducing the correct thermodynamic profile under cloud-intense conditions. These results underscore the benefit of using the physically consistent approach in retrieving, evaluating, and assimilating PBLH estimates, as well as the utility of multiphysics to better address model uncertainties. Significance Statement Studies on weather forecast models typically involve running the model multiple times and adjusting model inputs slightly each time to produce a range of predicted variables. This range is crucial for evaluating forecast probabilities and integrating observations into the model. We found that using different model physics schemes can result in an equal or greater spread for predicted variables (here, we focus on boundary layer height and related variables), compared to input tweaks alone. Additionally, a particular scheme can introduce biases. These findings underscore the importance of employing multiple physics schemes in the model, as they widen the coverage (potentially doubling) of outputs, and thus better address forecast uncertainties.

Changes in the SST Seasonal Cycle in a Warmer North Pacific without Ocean Dynamical Feedbacks

Abstract Climate models project a significant intensification of the sea surface temperature (SST) seasonal cycle over the subpolar North Pacific due to global warming, with the shallower mixed layer widely recognized as the dominant factor. However, employing slab ocean experiments with only ocean–atmosphere thermal coupling, we find a substantial contribution from changes in surface heat flux to this seasonal cycle intensification. In particular, the stronger Newtonian cooling effect in winter acts as a more potent damping than in summer. This differential damping inhibits the warming in colder seasons, significantly contributing to the intensified SST seasonal cycle in the subpolar North Pacific. In addition, consistent phase shifts in the North Pacific are identified across CMIP6 models. In the northwest North Pacific, a phase advance is associated with anomalous heating in early spring, driven by enhanced warm atmospheric advection from lower latitudes and sea ice melting in marginal seas. In contrast, the southeast North Pacific exhibits a phase delay attributed to the anomalous cooling in spring relative to autumn. This cooling is due to weakened trade winds and increased presence of high clouds. The former leads to stronger evaporative cooling in spring, while the latter impedes shortwave radiation from reaching the ocean.

Highly protective and functional strengthening strategies for 3D printed continuous carbon fiber reinforced polymer composites: manufacturing and properties

Carbon fiber-reinforced polymer (CFRP) composites have gradually emerged as a crucial material in the aerospace industry. However, inadequate impact resistance and thermal stability limit survival in extreme environments. Inspired by the specific functions of multiple layers of tissue, from bird feathers to the musculoskeletal system. We propose low-cost composite strengthening strategies and efficient novel three-dimensional graphene aerogel manufacturing methods. A novel graphene aerogel/carbon fiber reinforced polymer (GAC) composite prepared by in-situ laser-induced graphene (LIG) layers on the surface of 3D-printed CFRP. GAC composites enhance CFRP's impact protection, thermal insulation, and electromagnetic shielding capabilities. For protection, GAC composites reduce low-velocity impact damage by 26.2%. The graphene layer can increase the thermal buffering capacity of the material four times, and the long-term service temperature can be increased by 40% compared to traditional CFRP. For functionality, the composites enable electromagnetic interference (EMI) shielding effectiveness of up to 50.2 dB. Furthermore, it can achieve surface heating above 400 °C and rapid de-icing through electrothermal effects. The simple and efficient processing method of GAC composites and tunable functionalities holds promise for the development of highly protective and intelligent aircraft skins.

Thermal hydraulic and material analysis of upgraded flat-type Graphite divertor mock-up for Pakistan Spherical Tokamak (PST)

The design of a divertor is critically dependent on managing power deposition, erosion effects, and plasma configuration. An upgraded double-null divertor configuration has been developed for the Pakistan Spherical Tokamak (PST), featuring graphite targets that are actively cooled and designed to withstand a peak heat flux of 0.3 MW/m² at a pressure of 0.1 MPa. This paper presents a comprehensive thermal-hydraulic and material analysis for the upgraded flat-type divertor mock-up system, covering aspects such as material surface heat load, peak temperature rise (∆T °C) on the mock-up, and surface temperature increase in the cooling channel. The analysis includes total deformation (mm) and equivalent strain for the inner vertical target (IVT), outer vertical target (OVT), and dome structure, along with material comparison. The recommended SST K-ω turbulence model is utilized in the pressure-based transient analysis, with an inlet velocity of 1.5 m s-1 and an inlet temperature of 16.8 °C. A comparative study of the material and thermal-hydraulic analyses was performed using CFD and RELAP5. The findings reveal that graphite is more suitable than tungsten for the PST's upgraded divertor system, demonstrating its effectiveness as the preferred surface material to address heat enhancement challenges in the PST.

Experimental and simulation study on hygroscopic hydrogel-based thermal management of electronic device

With the increasing power of electronic devices, thermal management has become crucial for their operational efficiency and lifespan. In this work, we have demonstrated a sorption-based thermal management strategy enabled by hygroscopic hydrogel. The polyacrylamide (PAM) hydrogel impregnated with LiCl (PAM-LiCl) was attached to a silicon wafer. And Pt metal circuits were coated to the silicon wafer to measure the temperature variations under different heat flux densities. The results show that the hydrogel can effectively reduce the surface temperature. At a heating power of 0.3 W/cm2, the temperature control duration reached 30 min, with an average effective heat transfer coefficient of 65.5 W/(m2·K) and an effective heat storage density of 171 J/cm2. Additionally, we developed and validated a multiphysics model considering desorption and vapor diffusion within the hydrogel. Numerical results indicate that during the desorption cooling process, the surface heat transfer resistance and the internal diffusion resistance play a dominant role. Additionally, we analyzed the effects of material properties, structure parameters, and operating conditions on the thermal management performance. This study helps to understand the key points of sorption-based thermal management technology and guide the design and optimization of sorption-based thermal management system.

Effect of the self-rewetting fluids on heat transfer performance of gravity heat pipes with sintered porous wick

The distribution of the working fluid in a heat pipe directly affects the phase change heat transfer process. This paper explores how self-rewetting fluids (SRWF) and porous wicks affect the distribution of working fluids and heat transfer efficiency in gravity heat pipe (GHP). We sintered a porous wick onto the evaporator section and tested two working fluids: water and SRWF (3 % butanol aqueous solution). The filling ratio of the working fluid φ was varied from 11.5 % to 46 %. We found that at large filling ratios, porous wick surface will immerse in liquid, and at small filling ratios the heating surface will lack of liquid. Consequently, the GHP operates at a lower temperature at a filling ratio of 23 % compared to 11.5 % and 46 %. The type of working fluid significantly impacts the operating temperature and temperature uniformity. The Marangoni effect of the SRWF enhances the rewetting of the fluid in the porous wick, but this effect is only observed after the temperature reaches the inflection point (where the SRWF exhibits minimum surface tension). Before this point, the GHP operating temperature with SRWF is relatively higher than with water. Correspondingly, the temperature uniformity on the evaporator section is better when using SRWF. At φ = 23 %, Q = 500 W the temperature uniformity improved by 66 %. At Q = 660 W the evaporator heat transfer coefficient increased from 3991.6 W/m2K to 6130.5 W/m2K which is a 53.6 % improvement over water. We used an infrared camera to visualize the rewetting phenomenon of SRWF in the heated porous wick, confirming that SRWF can rewet the dry-out area, thus validating our hypothesis.

Исследование работы термической опреснительной установки с контактным испарителем и компрессией паровоздушной смеси

One of the global issues of our time is the shortage of freshwater resources. Desalination of marine and brackish waters is a promising solution to this problem. The most common desalination technologies are thermal (distillation) and baromembrane (reverse osmosis and nanofiltration) processes. When designing demineralization stations with reverse osmosis units, it is necessary to consider a number of limitations associated with higher requirements for pretreatment of water entering the unit. The use of thermal desalination plants makes it possible to obtain fresh water of higher quality, and less stringent requirements are imposed on the preliminary preparation of water for this type of unit. However, during the operation of desalination plants of this type, scale forms on the heating surfaces, which negatively affects the efficiency of the unit. Scale is formed less intensively in the units with contact vapors, since in this case the evaporation process occurs in volume. Thus, the development of thermal scheme of such unit and the study of their operation is relevant. The tasks have been solved using the methods of experimental studies of heat and mass transfer processes, mathematical processing of experimental data, and balance calculations of power plants. A thermal scheme of a thermal desalination plant with a contact evaporator with compression of a vapor-air mixture has been developed. Thermal and material balance has been compiled, on the basis of which energy costs have been determined to obtain m3 of fresh water. The authors have proved the determining influence of the temperature of desalinated water in the bubbling zone on the productivity of desalination plants with a contact evaporator. An amendment has been obtained that allows the initial salinity of water and brine to be considered when calculating the operating cycle of the unit. As a result of the analysis of the results obtained, it is found that an increase in the water temperature in the bubbling zone allows us to increase the productivity of the unit, and an increase of the drying temperature of the vapor-air mixture leads to a decrease of the energy consumption of the desalination plant. The introduction of an amendment considering the salinity of the source water and brine makes it possible to increase the accuracy of calculating air humidification up to 15 %.

Revisiting the inconsistent influence of El Niño-Southern Oscillation on the equatorial Atlantic

Abstract The impact of El Niño-Southern Oscillation (ENSO) on the equatorial Atlantic Zonal Mode (AZM) is investigated using two atmospheric reanalysis products and 44 models from the Coupled Model Intercomparison Project Phase 6 (CMIP6). While the impact of ENSO on equatorial Atlantic SST is inconsistent, as previously reported, there is a very robust influence of decaying ENSO events in boreal spring on the contemporaneous surface zonal winds over the equatorial Atlantic, with El Niño events associated with anomalous easterlies that cool the equatorial Atlantic. This dynamic impact is counteracted by a thermodynamic impact, in which El Niño events cause changes in surface heat fluxes that lead to warming over the tropical Atlantic. The thermodynamic influence is active throughout the lifecycle of the ENSO event, but the dynamic influence is highly seasonal with a pronounced peak in boreal spring. Thus, a quickly decaying El Niño event will lead to warming, while a slowly decaying event will lead to cooling in the equatorial Atlantic. The ENSO-AZM relation is further complicated by partially independent Atlantic variability, in particular that associated with the South Atlantic subtropical dipole (SASD). Prediction experiments with a simple linear regression model support the role of the SASD as an AZM precursor. Many CMIP6 models show skillful predictions of the June-July-August AZM based on SST indices in the preceding December-January-February, with correlations above 0.5. When predictions are restricted to ENSO years, even more models exceed this threshold, but skill in the reanalyses remains relatively low, possibly due to insufficient training data.

Deccan Volcanism and Related Seismic Unrest in the Koyna–Warna Region, India

Abstract Koyna–Warna is a region of low-tectonic deformation and normal surface heat flow (∼40 mW/m2) in the Deccan volcanic province, India, where low-to-moderate magnitude earthquakes have continued to occur in the last 60 yr. These earthquakes are uniquely restricted to an 11×16 km2 area and confined to the upper crust between 3 and 9 km depth. Located at the last phase of the interaction of India with the Reunion mantle plume ∼65 Ma ago responsible for extensive volcanism, the cause of sustained seismicity in Koyna region is debated. Using the shear-wave velocity model derived through the joint inversion of the receiver function and surface-wave data from the seismic zone, we propose that earthquakes in the Koyna region occur due to stress concentration arising because of the high-density magma intrusions in the shallow crust at 3–9 km. The high-density mafic-ultramafic body exerts gravitationally induced stress of about ∼12 to 15 MPa. The continuation of earthquakes in the deeper part is inhibited by the possible fluid-filled mush zone imaged as a low-velocity layer at a 9–17 km depth. The magma intrusion as dike can induce a cycle of normal faulting in the overlying rock mass, as observed in the Warna region. We present the first evidence of an extremely high velocity (>4.7 km/s) layer at 40–50 km below Moho, interpreted as the presence of eclogite–peridotite responsible for producing Deccan magma in large volume.

Deep thermal state on the southern margin of the Zhangzhou Basin based on the electrical conductivity model

Exploring the internal spatial and thermal structure of the Zhangzhou Basin is of great scientific significance in understanding the properties of the deep heat sources and the heating mechanism of hot springs in this region. This study estimates the temperature distribution within the upper mantle of the Basin's southern margin using the Arrhenius equation and Hashin-Shtrikman bounds based on a two-dimensional crust-mantle electrical resistivity model. We also employ a layered simulation technique to calculate the crustal temperature distribution using a one-dimensional steady-state heat conduction equation, constrained by the upper mantle's top and ground surface temperatures. This approach displays the characteristics of the longitudinal variations and horizontal inhomogeneities in crust-mantle temperature. Additionally, we estimate the heat flow values within the study area. Our findings reveal that: (i) the upper mantle (at depths of 30 - 50 km) exhibits a temperature range of 700 - 1100 °C, with the presence of local Moho and upper mantle uplifts; (ii) the crustal temperature spans from 21 - 900 °C, with a diminishing influence of the upper mantle uplift area on crustal temperature at shallower depths; (iii) the surface heat flow values derived from our simulations range between 87 and 100 mW/m2, averaging at 93.23 mW/m2; (iv) the exploration of dry heat rock in this region is likely to reach a depth of at least 6 km. These results suggest that the genesis of hot springs in the study area is not solely influenced by the heat energy extracted from large-area granitic surrounding rocks during a long transport process, but is also considerably affected by local deep thermal anomalous bodies and deep-large faults.

Experimental and Numerical Studies of Heat Transfer Through a Double-Glazed Window with Electric Heating of the Glass Surface

This paper presents experimental and theoretical studies of heat transfer through single- and double-glazed windows with electrical heating of the internal surfaces. Heating is achieved by applying a voltage to the low emissivity coating of the inner glass. A thermophysical model has been developed to simulate the heat transfer through these units, allowing us to determine their thermal characteristics. Experimental data are used to validate the numerical model. The resulting heat flux and temperature distributions on the external and internal surfaces of electrically heated double-glazed units are analysed. According to the results of experimental and numerical studies, it was found that the adopted electric heating scheme allows 83–85% of the heat to enter the room and 15–17% is removed to the outside. This makes it possible to increase the radiation component of the heat flow from the window to the room and improve the thermal comfort in the room. In general, this article shows that existing industrial windows with low-emissivity glass surface coating can be upgraded with simple and inexpensive modernisation, without compromising the main function of the window—efficient transmission of visible light—and create an additional (backup) heating device that can work effectively together with the existing heating system in the event of a sudden cold snap at low temperatures (below −20 °C), to prevent condensation of water vapour in the windows, and to prevent condensation on the surface of the window facade wall. Formally, a back-up (emergency) heating system is created in the room, which contributes to the energy sustainability of the building and therefore to energy security in general.