Latent Heat Effects Research Articles

Boundary layer flow and heat-mass transfer of shear-thinning nanofluid past a thin needle: electroperiodic magnetic field and thermo-diffusion effects

Heat and mass transfer in a boundary layer flow (BLF) of shear-thinning nanofluid (NF) around a thin needle has various practical applications including industrial processes, like medical devices, complicated cooling systems, high-efficiency thermal control in microelectronic devices, and chemical reactors designs. With a focus on its practical applications, this work investigates the heat and mass transfer effectiveness in a BLF of shear-thinning fluid containing alumina-copper nanoparticles around a thin needle subject to electroperiodic magnetic field in a nonlinear radiative environment. A comparative analysis is done for heat-mass transfer performance of alumina-copper-water-tangent hyperbolic fluid and water-tangent hyperbolic in order to optimize thermal and mass transmission efficiency by highlighting the importance of latent heat, nanomaterial load and thermo-diffusion processes. This work is novel because such comparative investigation on heat-mass transfer for alumina-copper-water-tangent hyperbolic fluid and water-tangent hyperbolic is not taken yet. The governing model for a BLF around a thin needle are solved using Runge Kutta fourth order (RK-4) method. The findings shows that the action of electroperiodic magnetic field greatly improves mass transfer and heat transfer performance. Latent heat effect and needle thickness enlargement improve the rate of heat-mass. Elevating the Weissenberg number modifies the flow dynamics. Adding more alumina-copper nanoparticles to the mixture increases its thermal conductivity and as a result increases the heat transfer rate. The Dufour number had a positive effect on temperature distribution. The activation energy, and Soret numbers all worked together to significantly alter the concentration profile. The mixture () show better heat-mass transfer efficiency as compared to () fluid.

Thermal management optimization strategy for lithium-ion battery based on phase change material and fractal fin

In order to solve the problem of temperature control of lithium-ion battery (LB) in electric vehicles, a new battery thermal management system (BTMS) based on phase change material (PCM) coupled fractal fin (FF) was proposed. The effects of latent heat, thickness, and thermal conductivity of PCM (paraffin) on the thermal properties of BTMS were investigated. Subsequently, the fin structure was added to the BTMS to improve the heat transfer capacity, and the number of fins, aspect ratio, material and structure morphology were explored. The results show that when the latent heat of PCM is 200 kJ/kg, the thickness is 2 cm, and the thermal conductivity is 0.8 W/(m·K), the temperature of LB is 34.9 K lower than that of LB without the BTMS at 4C. In addition, the BTMS has the best performance when FF-II with a fin count of 5, aspect ratio of 7:1, and material of carbon steel are used. The temperatures of LB are 301.8 K, 303.9 K, 305.4 K, and 307.3 K at 1 to 4C, respectively, and the temperature difference in BTMS can be controlled within 2.5 K. This study provides some guidance for the optimization of BTMS.

Spatio-temporal averaging of jets obscures the reinforcement of baroclinicity by latent heating

Abstract. Latent heating modifies the jet stream by modifying the vertical geostrophic wind shear, thereby altering the potential for baroclinic development. Hence, correctly representing diabatic effects is important for modelling the mid-latitude atmospheric circulation and variability. However, the direct effects of diabatic heating remain poorly understood. For example, there is no consensus on the effect of latent heating on the cross-jet temperature contrast. We show that this disagreement is attributable to the choice of spatio-temporal averaging. Jet representations relying on averaged wind tend to have the strongest latent heating on the cold flank of the jet, thus weakening the cross-jet temperature contrast. In contrast, jet representations reflecting the two-dimensional instantaneous wind field have the strongest latent heating on the warm flank of the jet. Furthermore, we show that latent heating primarily occurs on the warm flank of poleward directed instantaneous jets, which is the case for all storm tracks and seasons.

Aircraft Electrothermal Pulse Deicing

Abstract Ice formation and accumulation on aircraft is a major problem in aviation. Icing is directly responsible for aircraft incidents, limiting the safety of air travel and requiring expensive, and sometimes ineffective deicing strategies. Furthermore, electrification of aircraft platforms leads to difficulties with integration of legacy deicing methods such as pneumatic boots. In this work, we study electrothermal pulse deicing capable of efficient and rapid removal of ice from aircraft wings. The pulse approach enables the efficient melting of a thin (<100 μm) ice layer on the wing surface to limit parasitic heat losses. Only the interface is melted, with the rest of the ice sliding on the melt lubrication layer due to aerodynamic forces. To study pulse deicing, we developed a transient thermal-hydrodynamic numerical model that accounts for multiple phases and materials, specific and latent heating effects, melt layer hydrodynamics, as well as boundary layer effects. To identify optimal deicing strategies, we use our model to study the effects of heater thickness (50 μm < th < 1 mm), substrate electrical insulation thickness (10 μm < ti < 1 mm), pulse duration (0.4 s < Δtpulse < 4.5 s), and pulse energy. Optimum operating points are identified for large (Boeing-747), midsize (Embraer-E175), and small (Cessna-172) aircraft. The scale-dependent thermal-hydraulic model results are used to estimate input conditions required for deicing and integrated into an electrical model considering energy storage, power electronics, integration, and layout, to achieve overall volumetric and gravimetric power density optimization.

A simple model linking radiative–convective instability, convective aggregation and large-scale dynamics

Abstract. A simple model is presented which is designed to analyse the relation between the phenomenon of convective aggregation at small scales and larger-scale variability that results from coupling between dynamics and moisture in the tropical atmosphere. The model is based on single-layer dynamical equations coupled to a moisture equation to represent the dynamical effects of latent heating and radiative heating. The moisture variable q evolves through the effect of horizontal convergence, nonlinear horizontal advection and diffusion. Following previous work, the coupling between moisture and dynamics is included in such a way that a horizontally homogeneous state may be unstable to inhomogeneous disturbances, and, as a result, localised regions evolve towards either dry or moist states, with divergence or convergence respectively in the horizontal flow. The time evolution of the spatial structure of the dry and moist regions is investigated using a combination of theory and numerical simulation. One aspect of the evolution is a spatial coarsening that, if moist regions and dry regions are interpreted as convecting and non-convecting respectively, represents a form of convective aggregation. When the weak temperature gradient (WTG) approximation (i.e. a local balance between heating and convergence) applies, and horizontal advection is neglected, the system reduces to a nonlinear reaction–diffusion equation for q, and the coarsening is a well-known aspect of such systems. When nonlinear advection of moisture is included, the large-scale flow that arises from the spatial pattern of divergence and convergence leads to a distinctly different coarsening process. When thermal and frictional damping and f-plane rotation are included in the dynamics, there is a dynamical length scale Ldyn that sets an upper limit for the spatial coarsening of the moist and dry regions. The f-plane results provide a basis for interpreting the behaviour of the system on an equatorial β plane, where the dynamics implies a displacement in the zonal direction of the divergence relative to q and hence to coherent equatorially confined zonally propagating disturbances, comprising separate moist and dry regions. In many cases the propagation speed and direction depend on the equatorial wave response to the moist heating, with the relative strength of the Rossby wave response to the Kelvin wave response determining whether the propagation is eastward or westward. Within this model, the key overall properties of the propagating disturbances, the spatial scale and the phase speed, depend on nonlinearity in the coupling between moisture and dynamics, and any linear theory for such disturbances therefore has limited usefulness. The model described here, in which the moisture and dynamical fields vary in two spatial dimensions and important aspects of nonlinearity are captured, provides an intermediate model between theoretical models based on linearisation and one spatial dimension and general circulation models (GCMs) or convection-resolving models.

The Effect of Solute Suppressed Nucleation Effect and Latent Heat on the Grain Refinement of Cast Aluminum Alloy

The Effect of Solute Suppressed Nucleation Effect and Latent Heat on the Grain Refinement of Cast Aluminum Alloy

Dwindling Effective Radiative Forcing of Large Volcanic Eruption: The Compensation Role of Ocean Latent Heat Flux

AbstractClimatic impacts of historical volcanism are principally tied to the eruption size, while observation versus model discrepancies have been commonly attributed to the uncertainties in paleo‐reconstruction or malpresentation of volcanic aerosols in models. Here we present convergent evidence for significant compensation effect of ocean latent heat (LH) in balancing the tropical volcanic‐induced heat loss, by introducing an effective perturbation ratio which is found to decrease with increasing eruption magnitude. Four LH compensation hot spots overlapping with the trade wind regions are identified, together with three western boundary currents regions with intensified LH loss. Comparison between the 1258 Samalas and 1452 Unidentified eruptions suggests considerable modulation of the concurring El Nino‐Southern Oscillation on LH anomaly, which is further verified by CESM large ensemble sensitivity experiments. This study depicts how the interplay between the ocean and the atmosphere could contribute to the overall resilience of the climate system in the face of volcanic disturbances.

Experimental and Theoretical Investigation of Thermal Parameters Influencing the Freezing Process of Ice Cream

Freezing time stands out as the most critical parameter in ice cream production, significantly influencing the final product’s quality and production efficiency. Therefore, it is essential to accurately estimate the freezing time based on ice cream recipes. This research paper focuses on determining the thermal properties of ice cream samples by leveraging insights from previous studies. Moreover, a new specific heat correlation is proposed to account for the latent heat effect of water during the freezing process. The results demonstrated that the new specific heat correlation aligns well with established formulas from previous research as well as experimental results with maximum 2.5% deviation. To validate the accuracy of the proposed numerical model, experimental studies were compared with numerical results for the first time in the context of ice cream freezing inside a mold. Additionally, a parametric analysis was conducted using numerical modelling to discern the relative importance of various production process parameters. Notably, the glycol–water mixture temperature emerged as the most influential parameter affecting freezing time, while the amount of air inside the ice cream was identified as the least significant factor.

Robust Reconstruction of Historical Climate Change From Permafrost Boreholes

AbstractReconstructing historical climate change from deep ground temperature measurements in cold regions is often complicated by the presence of permafrost. Existing methods are typically unable to account for latent heat effects due to the freezing and thawing of the active layer. In this work, we propose a novel method for reconstructing historical ground surface temperature (GST) from borehole temperature measurements that accounts for seasonal thawing and refreezing of the active layer. Our method couples a recently developed fast numerical modeling scheme for two‐phase heat transport in permafrost soils with an ensemble‐based method for approximate Bayesian inference. We evaluate our method on two synthetic test cases covering both cold and warm permafrost conditions as well as using real data from a 100 m deep borehole on Sardakh Island in northeastern Siberia. Our analysis of the Sardakh Island borehole data confirms previous findings that GST in the region have likely risen by 5–9°C between the pre‐industrial period of 1750–1855 and 2012. We also show that latent heat effects due to seasonal freeze‐thaw have a substantial impact on the resulting reconstructed surface temperatures. We find that neglecting the thermal dynamics of the active layer can result in biases of roughly −1°C in cold conditions (i.e., mean annual ground temperature below −5°C) and as much as −2.6°C in warmer conditions where substantial active layer thickening (>200 cm) has occurred. Our results highlight the importance of considering seasonal freeze‐thaw in GST reconstructions from permafrost boreholes.

Heat transfer efficiency of thermoelastic shaped phase change materials enhanced by pressure

As the melt front gradually moves away from the heat source during the heat transfer process, phase change materials (PCMs) inevitably cause the heat transfer efficiency to decrease with heat transfer time, especially for a shaped PCM (SPCM). In this study, it is proposed to compress the SPCM phase-changed region by pressure to reduce the thermal resistance between the heat source and the phase transition interface, thus slowing down the rate of heat transfer efficiency decrease. We established a one-dimensional semi-infinite compression heat transfer theoretical model and prepared a thermoelastic SPCM (TESPCM) for compression heat transfer experiments, which verified the reliability of the theoretical model. Experimental demonstrate that the pressure enhancement contributes to the heat transfer efficiency and becomes more pronounced with heat transfer time. The pressure-enhanced heat transfer was analyzed by the theoretical model with the following conclusions: pressure enhancement not only improves the latent heat utilization, heat transfer cut-off time, and maximum tolerable heat flux of TESPCM but also increases the specific energy and specific power of TESPCM. The effect of pressure on heat transfer efficiency tends to accelerate with increasing compression. Furthermore, the improvement of heat transfer by pressure enhancement becomes more significant with the increase of thermal conductivity, but the effect of latent heat on temperature control decreases with the increase of compression.

Numerical simulation and experimental study on effect of cooling rate on microstructure and strength of nanostructured materials

In this study, by numerical simulation (finite element method, FEM) and experimental, the cooling rate was investigated by changing the product thickness (20, 3, 2, 1, 0.5 and 0.3) mm of Al based two-phase nanostructured materials casted through a copper mold. The effect of cooling rate on the microstructure and strength of the alloy was studied. The Experimental results showed that the precipitated intermetallic phases have a decreasing size corresponding to the increasing cooling rates by simulation from ~102 K/s to ~104 K/s. The results show that an appropriate cooling rate can improve the microstructure and properties of the alloy. The Abaqus/Standard capability for uncoupled heat transfer analysis was intended to model solid body heat conduction with general, temperature-dependent conductivity; internal energy (including latent heat effects); and quite general convection and radiation boundary conditions. This study describes the basic energy balance, constitutive models, boundary conditions, finite element discretization, and time integration procedures used. The time step used an automatic algorithm through the smallest tolerance. The maximum temperature change was allowed over a period and the increment was adjusted for this parameter, as was the rate of convergence in the non-linear cases. First-order heat transfer elements used the rule of numerical integration with integrated stations located at the corners of the element for thermal capacitance terms. (Jacobian terminology). This approach is particularly effective when there is a strong latent thermal effect. Thus, first - order elements were used in the case of latent heat. The HEATCAP element is available for single - point pooled thermal capacitance modeling. Centralized film loading options between the mold and the casting were specified by the user.

Preconditioning of mountain permafrost towards degradation detected by electrical resistivity

Warming permafrost has been detected worldwide and is projected to continue during the next century by many modelling studies. In mountain regions, this can lead to potentially hazardous impacts on short time-scales by an increased tendency for slope instabilities. However, time scales of permafrost thaw and the role of the ice content are less clear, especially in heterogeneous mountain terrain, where ice content can vary between zero and supersaturated conditions over small distances. Warming of permafrost near the freezing point shows therefore complex inter-annual behaviour due to latent heat effects during thawing and the influence of the snow-cover, which is governed by highly non-linear processes itself. Here, we demonstrate a preconditioning effect within near-surface layers in mountain permafrost that causes non-linear degradation and accelerates thaw. We hypothesise that a summer heat wave, as has occurred in the Central European summers 2003, 2015 and 2022, will enhance permafrost degradation if the active layer and the top of the permafrost layer are already preconditioned, i.e. have reduced latent heat content. This preconditioning can already be effectuated by a singular warm year, leading to exceptionally strong melting of the ground ice. On sloping terrain this ice-loss can be considered as irreversible, as large parts of the melted water will drain during the process, and an equivalent build-up of ice in cold years does not happen on similar time-scales as the melting. We propose a simple geophysical approach based on electrical resistivity tomography surveys that can assess the state of preconditioning in the absence of boreholes. In addition, we will show that resistivity data from a total of 124 permafrost sites in the Andes, Europe, and Antarctic adhere to a distinct power law behaviour between unfrozen and frozen states, which confirms the consistent electrical behaviour of permafrost and active layer materials over a wide range of landforms and material composition.

Efficiency of urban greening systems with maximized latent heat effect in urban heat island and climate change mitigation

Street, wall, and rooftop greening systems are essential for urban heat reduction and carbon neutrality. In this study, we compared the temperature-reducing effect of current and developed technologies that maximize the latent heat of evaporation through such greening systems. A research site with the maximum urban heat island effect was selected by analyzing the vulnerability of Suwon City, Korea. The latent heat of evaporation for each method was determined by conducting actual measurements and verified by performing computational fluid dynamics simulations. Based on the results of statistical techniques, the validated model was highly reliable. When developed technologies were applied, the temperature of the entire city was reduced by approximately 2 °C. Compared with the existing street greening system, the developed technology achieved a temperature reduction effect even at a distance of 5 m. Current wall greening systems only have a temperature reduction effect at 1 m, but that of the developed technology was approximately 1 °C even at a distance of 2 m. The existing rooftop greening system had a temperature reduction effect only at the height of 1.2 m, whereas that of the developed technology was effective even at 6 m, contributing to a reduction in the temperature of the entire city.

Experimental investigation of thawing behavior of saline soils using resistivity method

Abstract Electrical resistivity method has been widely used to study permafrost and to monitor the process of freezing-thawing. However, a thorough understanding of the mechanism of electrical response during thawing is missing. In this study, we investigated the thawing behavior of saline soils in the temperature range from roughly −10 to 15°C considering the effects of soil type and salinity. A total of nine experiments were performed with three soil types (silica sand, sandy soil, and silt) and three salinities (0.01, 0.1, and 1 S m−1). The results show that resistivity variations with temperature can be divided into three stages. In Stage I, tortuosity and unfrozen water content play major roles in the decrease of resistivity. In Stage Ⅱ, which is an isothermal or near isothermal process, resistivity still decreases slightly due to the thawing of residual ice and pore water movement. In Stage III, ionic mobility plays an important impact on decreasing resistivity. In addition, the isothermal process is found to only occur in silica sand that can be explained by latent heat effect. Exponential and linear models linking temperature with resistivity are used to fit the experimental data in Stages I and III. The fitting parameter in different models shows great correlation with soil type and salinity. Furthermore, unfrozen water content below 0°C is also estimated and uncertainty of estimation is analyzed.

Indirect effects of latent heat of condensation on the simulation of the 2021 catastrophic Henan rainfall event in central China

AbstractCloud‐related latent heat is critical to the development and maintenance of atmospheric circulation. However, it is unclear how sensitive the key large‐scale weather systems of an extreme rainfall event could be to the variation in cloud‐related latent heat. In a companion study, by investigating the indirect effects of different microphysics schemes, we hypothesized that the latent heat of condensation (CT) would play a role in the ability to simulate the extreme rainfall event that took place in Henan Province, central China, on July 19–21, 2021. To examine the proposed hypothesis, the impacts of varying the CT and the collection of cloud water by rainwater (ACW) in the Thompson, WDM6, and Morrison microphysics schemes on the simulation of the southerly flow and its indirect effect on this extreme rainfall case were studied using the Advanced Research Weather Research and Forecasting (ARW‐WRF) model. It was found that directly changing the CT and ACW had significant effects on the southerly flow and precipitation. An increase in CT generally led to a reduced temperature gradient, a smaller pressure gradient, a stronger southerly flow, and a precipitation surge of 32%–50%. Similar outcomes resulted from increasing ACW in the WDM6 scheme, which effectively diminished the cloud mixing ratio, generated higher CT, and consequently intensified the southerly flow and precipitation by 31%. This study confirmed that the accurate simulation of microphysical processes, along with latent heating, is desirable for more realistically reproducing the key weather systems in the simulation of extreme rainfall.

Asymmetry of the Distribution of Vertical Velocities of the Extratropical Atmosphere in Theory, Models, and Reanalysis

Abstract The vertical velocity distribution in the atmosphere is asymmetric with stronger upward than downward motion. This asymmetry is important for the distribution of precipitation and its extremes and for an effective static stability that has been used to represent the effects of latent heating on extratropical eddies. Idealized GCM simulations show that the asymmetry increases as the climate warms, but current moist dynamical theories based around small-amplitude modes greatly overestimate the increase in asymmetry with warming found in the simulations. Here, we first analyze the changes in asymmetry with warming using numerical inversions of a moist quasigeostrophic omega equation applied to output from the idealized GCM. The inversions show that increases in the asymmetry with warming in the GCM simulations are primarily related to decreases in moist static stability on the left-hand side of the moist omega equation, whereas the dynamical forcing on the right-hand side of the omega equation is unskewed and contributes little to the asymmetry of the vertical velocity distribution. By contrast, increases in asymmetry with warming for small-amplitude modes are related to changes in both moist static stability and dynamical forcing leading to enhanced asymmetry in warm climates. We distill these insights into a toy model of the moist omega equation that is solved for a given moist static stability and wavenumber of the dynamical forcing. In comparison to modal theory, the toy model better reproduces the slow increase of the asymmetry with climate warming in the idealized GCM simulations and over the seasonal cycle from winter to summer in reanalysis. Significance Statement Upward velocities are stronger than downward velocities in the atmosphere, and this asymmetry is important for the distribution of precipitation because precipitation is linked to upward motion. An important and open question is what sets this asymmetry and how much it increases as the climate warms. Past work has shown that current theories greatly overestimate the increase in asymmetry with warming in idealized simulations. In this work, we develop a more complete theory and show that it is able to better reproduce the slow increase of the asymmetry with warming that is found over the seasonal cycle from winter to summer and in idealized simulations of warming climates.

Effect of Latent Heat by Phase Transformation on the Thermal Behavior of Steel Billet during Heating.

The effect of latent heat via phase transformation on the thermal behavior of a billet was investigated during the heating process. The latent heat of the billet strongly affected the temperature distribution of the billet during heating, although the heating rate of the billet was not high during the process. The temperature profile of the center region of the steel billet with latent heat had a strong flat shape compared with the other regions, as the heat supply to the center region was limited during the heating process owing to the finite thermal conductivity and mass effect of the billet. The latent heat by phase transformation typically occurred in the middle stage of heating, and the latent heat increased the temperature deviation of the billet during heating owing to the delay in the temperature rise at the center region of the billet. During the phase transformation of carbon steels during heating, the gas temperature needs to be low to reduce the temperature deviation or thermal stress of the billet. Industrial hot rolling mills are required to consider the latent heat by phase transformation of the billet to properly design the heating pattern for the billet. The heating pattern in the reheating furnace should be varied with the materials to obtain a high heating quality for the billet.

Phase-field description of fracture in NiTi single crystals

A phase-field model for thermomechanically-induced fracture in NiTi at the single crystal level, i.e., fracture under loading paths that may take advantage of either of the functional properties of NiTi–superelasticity or shape memory effect–, is presented, formulated within the kinematically linear regime. The model accounts for reversible phase transformation from austenite to martensite habit plane variants and plastic deformation in the austenite phase. Transformation-induced plastic deformation is viewed as a mechanism for accommodation of the local deformation incompatibility at the austenite–martensite interfaces and is accounted for by introducing an interaction term in the free energy derived based on the Mori–Tanaka and Kröner micromechanical assumptions and the hypothesis of martensite instantaneous growth within austenite. Based on experimental observations suggesting that NiTi fractures in a stress-controlled manner, damage is assumed to be driven by the elastic energy, i.e., phase transformation and plastic deformation are assumed to contribute in crack formation and growth indirectly through stress redistribution. The model is restricted to quasistatic mechanical loading (no latent heat effects), thermal loading sufficiently slow with respect to the time rate of heat transfer by conduction (no thermal gradients), and a temperature range below Md, which is the temperature above which the austenite phase is stable, i.e., stress-induced martensitic transformation is suppressed. The numerical implementation of the model is based on an efficient scheme of viscous regularization in both phase transformation and plastic deformation, an explicit numerical integration via a tangent modulus method, and a staggered scheme for the coupling of the unknown fields. The model is shown able to capture transformation-induced toughening, i.e., stable crack advance attributed to the shielding effect of inelastic deformation left in the wake of the growing crack under nominal isothermal loading, actuation-induced fracture under a constant bias load, and crystallographic dependence on crack pattern.

Unraveling the Formation Mechanism of Exceptionally Strong Marine Heatwaves in the Northeast Pacific in 2020

Abstract Throughout 2020, a persistent marine heatwave (MHW) event occurred in the northeast (NE) Pacific, which exhibited a record-breaking intensity and long duration. Three peaks of sea surface temperature (SST) anomaly are identified in April, July, and November 2020, respectively, all of which are caused by the surface latent heat flux (LH) term. A Taylor expansion analysis for the LH term reveals that positive LH anomaly (LHA) played the decisive role in increasing the latent heating effect, whereas the mixed layer depth anomaly was not important in the 2020 MHW. The positive LHA was primarily caused by the southerly wind anomalies, which advected more humid air from lower latitudes to the NE Pacific and thus reduced the difference between the saturated specific humidity at sea surface and actual surface specific humidity. This reduced sea–air humidity difference was conducive to less evaporation, leading to positive LHA. Using an atmospheric general circulation model forced by observed SSTs, we find that although the atmospheric circulation anomalies associated with the 2020 MHW can be partly constrained by both tropical Pacific SST and local SST over the North Pacific, the role of internal atmospheric variability in the 2020 MHW’s formation cannot be overlooked. The prediction skill for the 2020 MHW in the North American Multimodel Ensemble models is limited to one month, indicating the challenge of accurately predicting MHW in the NE Pacific. The finding about the contribution of sea–air humidity difference to the LHA provides a new insight into the formation mechanism of MHW. Significance Statement An exceptionally strong and persistent marine heatwave occurred in the northeast Pacific throughout 2020, with three peaks in April, July, and November, causing considerable damage to local fisheries and ecosystems. This study found that the evolution of this marine heatwave was due to the less-than-normal release of latent heat at the ocean surface. This was mainly caused by the reduced sea–air humidity difference, which was attributed to the increased near-surface moisture transported by southerly wind anomalies. Our model experiments demonstrated that the associated anomaly fields in the atmosphere partly stemmed from stochastic processes. The state-of-the-art dynamic models can only predict this marine heatwave one month in advance, indicating the necessity of improving prediction skill for marine heatwave’s evolution in current models.

Latent heat effects in inductive heating of shape memory alloy fibers

AbstractMotivation of the present work is an inductive heating process, used in manufacturing a new kind of improved ultra‐high performance concrete. In this novel material, fibers made out of shape memory alloys are used to increase the maximum possible fiber volume fraction, or to create an internal state of compressive stress. In contrast to other works, the underlying microstructure transformation from martensite to austenite is highlighted based on thermal analysis. Dynamic scanning calorimetry measurements are adapted as basis for development of a phenomenological phase transformation model. It relates local temperature and temperature rate to the rate of change of the phase indicator, modeling the transformation of martensite to austenite. Latent heat is considered by an enthalpy method, the inductive heating process is considered by a phenomenological model. Study results for a purely thermodynamic process of heating a single fiber embedded in concrete are presented. They show that latent heat effects delay phase transformation and the process of fiber activation is very sensitive to the induced heat. Furthermore, it is discovered that latent heat causes a strongly inhomogeneous state of transformation in radial direction of the fiber, which is of great importance for thermomechanical processes and the interpretation of experimental results.