Latent Heat Release Research Articles

Diagnostic Analysis of Diabatic Heating in an Extreme Rainfall Event in Shandong Province, China

This study utilizes data from national ground meteorological observation stations in Shandong province, Fengyun-4 satellite data, and ERA5 reanalysis data. Through the calculation of atmospheric heat source changes, the role of diabatic heating in the occurrence and development of heavy rainfall is revealed. The widespread heavy-to-torrential rainfall event in Shandong province on 25 June 2018 is analyzed as a case study. It was found that a deep and robust southwest jet stream was the key system for the formation of this rainfall event. Satellite cloud images during the peak rainfall period showed vigorous development in the rainfall cloud region. During the concentrated rainfall period and when the low-altitude jet stream strengthened, there was mostly cold advection overhead at the observation station. The low-altitude jet stream transported moisture, increasing the humidity gradient, thus enhancing frontogenesis. The warm advection in the low-altitude jet stream was not the main energy supplier during heavy rainfall, and local temperature variations were the primary contributors to the thermodynamic conditions during the peak rainfall period. The rate of warming caused by the condensation and release of heat from water vapor significantly increased during the concentrated rainfall period. This warming effect played a heating role in the middle and lower layers, and the positive feedback from the latent heat release of water vapor condensation intensified the weather system affecting the rainfall, providing strong thermodynamic and dynamic conditions for heavy rainfall.

Ascent of volatile-rich felsic magma in dykes: a numerical model applied to deep-sourced porphyry intrusions

SUMMARY Dyke propagation is a mechanism for more rapid ascent of felsic magmas through the crust than is possible via diapirs or percolative flow. As it ascends, the magma undergoes complex physical and chemical transformations induced by decompression and cooling. These processes dramatically change the magma density and viscosity, which in turn affect magma ascent rate and the depth at which the dyke arrests. We present a mathematical model of dyke propagation for silicic magmas taking into account the presence of multiple volatile species (H2O and CO2), bubble growth, heat advection and loss, crystallization and latent heat release. We consider conditions for dykes associated with porphyry ore deposits, which may represent an end-member in rapid ascent of felsic magmas from depth. In particular, we simulate the propagation of dykes launched from a deep (900 MPa), volatile-saturated magma source, testing the effects of the magma H2O/CO2 content, temperature and mass on its ascent rate and final emplacement depth. The model predicts short ascent times (hours to days), with a large increase in viscosity at shallow depth, leading to stagnation and solidification of the dyke. Higher initial water content, higher temperature and larger mass of the magma in the dyke promote faster propagation and shallower arrest. Volatile loss from ascending magma remains limited until the stagnation depth, providing a potential mechanism for transfer of deep volatiles to hypabyssal blind intrusions associated with porphyry ore deposits. Our findings are applicable to the problem of silicic magma ascent through the crust more generally.

Study on heat transfer of waxy crude oil melting phase change based on a novel model

The study of phase change heat transfer of crude oil melting is important for pre-heating and restarting of pipelines. Combining the characteristics of waxy crude oil characteristics of waxy crude oil melting, a novel mathematical model was established, which can accurately describe the non-linear release of latent heat, liquid-solid interface changes, natural convection, and other key heat transfer problems. In the process of heating and melting, the variation law of the solid-phase interface position in the pipe at different initial solidification states was analyzed. The results showed that in the partially solidified pipeline, the liquid crude oil in the pipeline has a higher temperature at the initial heating stage, and continuously loses heat to the low temperature crude oil, resulting in a decline in the liquid-phase ratio at the initial stage. Because crude oil was affected by different degrees of radial thermal resistance, latent heat release and porous medium characteristics at different positions of the pipeline, the temperature drop curves of the crude oil varies greatly.

Effects of Latent Heat Release from Single‐Moment and Double‐Moment Microphysical Schemes on the Simulated Intensity of Typhoon Songda

Effects of Latent Heat Release from Single‐Moment and Double‐Moment Microphysical Schemes on the Simulated Intensity of Typhoon Songda

Solar-powered thermoelectric refrigeration with integrated phase change material: An experimental approach to food storage

In this paper, a novel phase change material (PCM) based Thermoelectric (TE) food storage refrigerator incorporating an integrated solar-powered energy source is introduced. The novelty aspects of this research lie in the unique combination of PCM with solar energy, not only to maintain temperatures below 5 °C, vital for reducing food spoilage, but also in designing extra experiments using water as a cooling method to enhance system performance. Designed to preserve a diverse range of fruits and vegetables with different moisture content below 5 °C, the system innovatively employs PCM to extend cooling time, reduce energy load, and avoid conventional refrigerants, contributing to environmental sustainability. Experimentally, the average time for PCM solidification was around 3.5 h, with a corresponding latent heat release time, maintaining a temperature range of 0 to 5 °C. The system effectively accommodated various food items with water content levels from 50 % to 99 %, achieving the target temperature within around 2 to 4 h and demonstrating a promising coefficient of performance (COP) of 0.69. A standout innovation included the utilization of water flow through copper piping to accelerate heat removal from TEC, enhancing the performance of the system and reducing the solidification time of PCM by approximately an hour. This research represents a significant advancement in refrigeration technology, highlighting the feasibility and optimization potential of integrating solar energy and PCM, and introduces a new direction for enhancing efficiency through water-cooled heat sinks.

Prediction of Ni-based alloy microstructure in wire arc additive manufacturing from cellular automata model

Wire Arc Additive manufacturing (WAAM) process is a class of directed energy deposition processes with wire feedstock. The process enables a higher build rate than the powder-based additive process and integrates multiple custom wire feedstock to induce spatial variation of microstructure and composition. The lower speed employed in WAAM reduces the cooling rate and resultant residual stress compared to the powder bed fusion process. The systematic epitaxy across the layer creates a directional/columnar microstructure for Ni-superalloy. Here, we report cellular automata model development to predict the microstructure evolution with surface and bulk nuclei for single track and multiple layers. The cellular automata model was developed to account for secondary element addition, predict segregation, local melting, and latent heat release, as well as predict crystallographic texture/Euler angles from orientation information. We experimentally validated the layer-level microstructure and texture from SEM and EBSD, respectively, and found agreement with the CA model developed.

Ultrafast Axial Freezing in a Liquid-Filled Capillary Tube.

Liquid-filled capillary tubes are a kind of standard component in life science (e.g., blood vessels, interstitial pores, and plant vessels) and engineering (e.g., MEMS microchannel resonators, heat pipe wicks, and water-saturated soils). Under sufficiently low temperatures, the liquid in a capillary tube undergoes phase transition, forming an ice nucleus randomly on its inner wall. However, how an ice layer forms from the nucleus and then expands, either axially or radially to the tube inner wall, remains obscure. We demonstrated, both experimentally and theoretically, that axial freezing along the inner wall of a water-filled capillary tube occurs way ahead of radial freezing, at a nearly constant velocity 3 orders in magnitude faster than the latter. Rapid release of latent heat during axial freezing was identified as the determining factor for the short duration of recalescence, resulting in an exponential rise of the supercooling temperature from ice nucleation via axial freezing to radial freezing. The profile of the ice-water interface is strongly dependent upon the length-to-radius ratio of the capillary tube and the supercooling degree at ice nucleation. The results obtained in this study bridge the knowledge gap between the classical nucleation theory and the Stefan solution of phase transition.

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.

Sensitivity of Arctic Surface Temperature to Including a Comprehensive Ocean Interior Reflectance to the Ocean Surface Albedo Within the Fully Coupled CESM2

AbstractAlmost all current climate models simplify the ocean surface albedo (OSA) by assuming the reflected solar energy without the ocean interior contribution. In this study, an improved ocean surface albedo scheme is incorporated into the Community Earth System Model version 2 (CESM2) to assess the sensitivity of Arctic surface temperature to including ocean interior reflectance to the OSA. Fully coupled CESM2 simulations with and without ocean interior reflectance are subsequently performed, we focus on the analysis of Arctic surface temperature responses. Incorporating ocean interior reflectance increases absorbed solar radiation and warms the ocean, enhancing seasonal heat storage and release across the Arctic Ocean, and increasing sea ice reduction and positive climate feedbacks that elevates Arctic surface temperature. Seasonal variations in air‐surface temperature differences induce changes in turbulent heat flux patterns, concurrently modifying dynamic advection and moisture processes that affect boundary layer humidity and low clouds, especially in winter. Based on partitioning physical processes in the thermodynamic energy equation, surface air warming is induced primarily through positive heating anomalies of vertical advection, latent heat release, and longwave radiative forcing. Through an examination of the surface energy budget, skin temperature warming is driven predominantly by increased downward longwave radiation, positive surface albedo feedback in summer, and increased conductive heat transport from the ocean particularly in winter. Significant effects of ocean interior reflectance on the Arctic Ocean, including sea surface warming and sea ice reduction, justify the importance of ocean interior reflectance in climate models for better understanding of ongoing Arctic climate changes.

Revolutionizing Automotive Cooling: A Comprehensive Review on Enhancing Radiator Performance through Nanofluid-Based Heat Transfer Augmentation and Pipeline Integration of Phase Change Materials

Abstract: This review explores cutting-edge advancements in automotive cooling systems, specifically focusing on enhancing radiator performance through a dual approach: the utilization of nanofluids for improved heat transfer and the incorporation of phase change materials (PCMs) within radiator pipelines. Nanofluids, engineered colloidal suspensions of nanoparticles in traditional coolants, exhibit enhanced thermal conductivity, leading to improved heat dissipation. The paper provides an overview of various nanofluid synthesis methods and reviews experimental studies showcasing their efficacy in augmenting thermal performance within automotive radiators. In parallel, the integration of PCMs into radiator pipelines introduces a novel dimension to heat management. Phase change materials, with their ability to store and release latent heat during phase transitions, contribute to temperature regulation and energy efficiency. The review explores different types of PCMs, their selection criteria, and summarizes experimental findings related to their incorporation in automotive cooling systems. A significant portion of the paper delves into the synergies and challenges associated with combining nanofluid-based heat transfer enhancement and PCM integration. The discussion underscores the potential for a holistic approach to radiator design, leveraging the complementary benefits of both nanofluids and PCMs. The findings presented in this review offer insights into the evol

Effect of TiC nano-treating on the fluidity and solidification behavior of aluminum alloy 6063

Wrought aluminum alloy AA 6063 is known for its favorable mechanical properties, corrosion resistance, and weldability in high-performance applications. Nonetheless, its limited fluidity hinders the cost-effective production of intricate structures through economical casting processes. To address this, a small fraction of TiC nanoparticles were dispersed into the AA 6063 melt to enhance its fluidity, eliminate hot cracking, and improve casting surface quality. Further investigation indicates that nanoparticles contribute to gradual latent heat release, grain growth restriction, and improved molten alloy wettability. The results demonstrate the potential of the emerging nano-treating technology in making traditionally difficult-to-cast alloys viable for low-cost casting operations to deliver products with enhanced high performance for numerous applications.

Sessile super-droplets as quasi-static wall deformations in direct numerical simulation of turbulent channel flow

Condensation is an important aspect of many flow applications due to the ubiquitous presence of humidity in the air at ambient conditions. For direct numerical simulations of such flows, simulating the gas phase as a mixture characterized by temperature and humidity coupled by the latent heat release and absorption has been shown to yield results consistent with multiphase direct numerical simulations at reduced cost. In the case of surface condensation, the deposition of condensate droplets represents an additional mechanism for flow modification. Extending the single-phase approach by tracking the mean deposition rates and consolidating the condensate mass into static super-droplets reintroduces the effects of surface droplets on the flow while retaining the computational advantages of simulating only the gas phase. Results of simulations of turbulent flow through a cooled, vertical channel with and without such droplets illustrate the additional effects captured compared to the original approach. In the immediate vicinity of a super-droplet, turbulent heat and vapor transport towards the cooled wall is enhanced. Direct impingement and deflection of the flow on the super-droplet cause a qualitative change in the distribution of the condensation rates, increasing on the surface of the super-droplets and decreasing in the surrounding regions. This modification of the near-wall transport leads to increased global cooling and drying efficiency compared to a smooth channel.

Radiative forcing from aerosol–cloud interactions enhanced by large-scale circulation adjustments

The impact of anthropogenic aerosols on clouds is a leading source of uncertainty in estimating the effect of human activity on the climate system. The challenge lies in the scale difference between clouds (~1–10 km) and general circulation and climate (>1,000 km). To address this, we use convection-permitting simulations conducted in a long and narrow domain, to resolve convection while also including a representation of large-scale processes. We examine a set of simulations that include a sea surface temperature gradient—which drives large-scale circulation—and compare these with simulations that include no gradient. We show that the effective radiative forcing due to aerosol–cloud interactions is strongly enhanced by adjustments of large-scale circulation to aerosol. We find that an increase in aerosol concentration suppresses precipitation in shallow-convective regions, which enhances water vapour transport to the portion of the domain dominated by deep convection. The subsequent increase in latent heat release in deep-convective regions strengthens the overturning circulation and surface evaporation. These changes can explain the increase in cloudiness under higher aerosol concentrations and, consequently, the large aerosol radiative effect. This work highlights the fundamental importance of large-scale circulation adjustments in understanding the effective radiative forcing from aerosol–cloud interactions.

Assessing the Fire-Modified Meteorology of the Grassland and Forest Intersection Zone in Mongolia Using the WRF-Fire Model

Climate change is already significantly affecting the frequency of wildfires in most regions of the world, and the risk of wildfires is expected to amplify further with global warming. Accordingly, there is growing concern about the mechanisms and impacts of extreme fires. In this study, a coupling of the Weather Research and Forecasting model and the Rothermel Fire model (WRF-Fire) is employed to reproduce the spread of fire within the national boundary of inner Mongolia from 21 to 27 May 2009. Simulations were run with or without feedback from fire-to-atmosphere models, and the study focused on how the energy flux of simulated fires changes the local meteorological environment. The coupled simulation could reproduce the burned area well, and the wind speed was the dominant factor in the fire spread, with a maximum value no more than 6.4 m/s, when the terrain height changes little and the proportion of grassland is low. After the feedback, the propagation speed of the fire accelerated, accompanying the release of latent and sensible heat, and local circulation formed near the front of the fire, leading to a convergence and divergence zone in the downwind area. It is worth noting that during a period of more than 140 h of simulation, the area of the fire field increased by 17% from ignition time. Therefore, considering the fire–atmosphere interaction is necessary for accurately predicting fire behavior.

In situ probing of the present-day zircon-bearing magma chamber at Krafla, Northeastern Iceland

Active felsic magmatism has been rarely probed in situ by drilling but one recent exception is quenched rhyolite sampled during the 2009 Iceland Deep Drilling Project (IDDP). We report finding of rare zircons of up to ∼100 µm in size in rhyolite glasses from the IDDP-1 well products and the host 1724 AD Viti granophyres. The applied SHRIMP U-Th dating for both the IDDP and the Viti granophyre zircons gives zero-age (±2 kyr), and therefore suggests that the IDDP-1 zircons have crystallized from an active magma intrusion rather than due to the 20–80 ka post-caldera magmatic episodes recorded by nearby domes and ridges. Ti-in-zircon geothermometer for Viti granophyre reveals zircon crystallization temperatures ∼800°C–900°C, whereas IDDP-1 rhyolite zircon cores show Ti content higher than 100 ppm, corresponding to temperatures up to ∼1,100°C according to the Ti-in-zircon thermometer. According to our thermochemical model at such elevated temperatures as 1,100°C, rhyolitic magma cannot be saturated with zircon and zircon crystallization is not possible. We explain this controversy by either kinetic effects or non-ideal Ti incorporation into growing zircons at low pressures that start to grow from nucleus at temperatures ∼930°C. High temperatures recorded by IDDP-1 zircon together with an occurrence of baddeleyite require that the rhyolite magma formed by partial melting of the host granophyre due to basaltic magma intrusion. Zr concentration profiles in glass around zircons are flat, suggesting residence in rhyolitic melt for >4 years. In our thermochemical modeling, three scenarios are considered. The host felsite rocks are intruded by: 1) a basaltic sill, 2) rhyolite magma 3) rhyolite sill connected to a deeper magmatic system. Based on the solution of the heat conduction equation accounting for the release of latent heat and effective thermal conductivity, these data confirm that the rhyolite magma could be produced by felsic crust melting as a result of injection of a basaltic or rhyolite sill during the Krafla Fires eruption (1975 AD).

Thermal storage characteristics of microencapsulated phase change material coatings in low-energy rural prefabricated building walls

ABSTRACT Prefabricated buildings in rural areas of China waste a large amount of energy due to poor thermal insulation. Phase change materials (PCMs) are able to stabilize room temperature by latent heat absorption and release during the phase change process. This study incorporated PCMs in the form of microcapsules into the interior wall coatings of prefabricated buildings, and by taking advantage of PCMs’ energy storage capacity, the thermal storage characteristics of PCM-coated bricks were investigated. The results show that microencapsulated phase change material(MPCM) coatings for prefabricated walls exhibit excellent thermal stability properties and effectively reduce the heat flux of prefabricated walls, with coatings having a MPCM mass fraction of 15% and a thickness of 5 mm providing the highest overall benefits. By fitting the numerical simulation results with experimental data, a novel multifunctional passive solar phase change heat collection and storage wall system was developed. This study innovatively combines energy storage materials with interior wall coatings in prefabricated walls of modular buildings investigating how it enhances the thermal stability of the external insulation walls and effectively reduces the reliance on heating equipment for auxiliary heating in rural residences. This essay aims to provide feasible recommendations for optimizing the dual-stage energy-saving and carbon reduction goals in both the construction and operation of rural areas.

Metallurgical slag modified monolayer graphene hybrid SA-based composite phase change materials for high thermal conductivity

Phase change materials are thermal energy storage materials with high heat storage density, low temperature loss and long cycle life. However, they also show a weak light absorption ability and low thermal conductivity, limiting their applicability for solar thermal conversion and storage technologies. In this paper, in order to improve the relatively low thermal conductivity of stearic acid and enhance its thermal conductivity, SGC-T composites with enhanced thermal conductivity were prepared using metallurgical slag, via the melt blending method. The SEM and EDS, surface scanning tests, were used to determine the morphology characteristics of the composite phase change materials and verify the addition of metallurgical slag. The physical phase composition, structure, and absorption coefficients were analyzed by XRD, FT-IR, and UV-Vis-NIR analyses. The thermophysical properties were analyzed by DSC. The thermal stability was explored using TG testing. The thermal conductivity was explored by measuring the thermal conductivity coefficient value of the samples at the testing temperature of 25 ℃ using the hot disk method/transient flat plate heat source method. The heat storage and exothermic capabilities of the samples were evaluated by the photo-thermal warming system/infrared thermography test. The results showed that the thermal conductivity of SGC was 0.663 W·(m·K)−1, and that of SGC-2 T, SGC-6 T, SGC-10 T, SGC-14 T, were 0.695 W·(m·K)−1, 0.758 W·(m·K)−1, 0.824 W·(m·K)−1 and 0.872 W·(m·K)−1, respectively, which are comparable to SGC. Compared with SGC, the thermal conductivity values of the four composite phase change materials increased by 4.8%, 14.3%, 24.3%, and 31.5%, respectively. SGC-14 T has the best heat transfer performance, which significantly improves the heat transfer performance during latent heat storage and release. Therefore, the SGC-14 T material reported in this work is a promising candidate in the field of energy-saving conversion, and further expands the applicability of phase change materials.

Anomalous Loading Rate Dependence of the Mechanical Properties of Metal-Organic Framework Crystals: Latent Heat Effects of the Pressure-Induced Local Phase Transition.

The loading rate dependence of the mechanical properties of metal-organic framework (MOF) crystals is key in determining their performance in many engineering applications, which, however, remains almost unexplored. Here, in situ nanoindentation experiments were conducted to investigate the impact of loading rate on mechanical properties of HKUST-1, a classic MOF. The Young's modulus and hardness of crystalline HKUST-1 are found to stay stable or decline with decreasing loading rate by creeping when the loading rate is below a particular speed, but they significantly decrease as the loading rate grows when it has higher magnitudes. Our molecular dynamics simulations indicate that the anomalous loading rate dependence of mechanical properties is attributed to the competition between the release and transfer of latent heat from the pressure-induced amorphous HKUST-1 because the increase in local temperature at large loading rates could induce the softening of HKUST-1 and the increase in the volume of transformed materials.

Backfill thermal properties improvement using granular phase change materials and graphite

Phase change materials (PCMs) are ideal for thermal energy storage due to latent heat release or absorption at target temperatures. Hence, adding PCMs into backfill materials of ground heat exchangers for example, can enhance the borehole thermal energy storage capacity and the corresponding shallow geothermal system performance. However, the heat transfer efficiency between the borehole and surrounding ground might be reduced because of the low thermal conductivity of PCMs. Incorporating additives with high thermal conductivity can reduce the lowering effect of PCMs on the overall thermal conductivity of the mixture while maintaining a desirable thermal capacity. This work mixes encapsulated PCMs (EPCMs), graphite and recycled glass fines, aiming to develop green backfill materials with excellent thermal properties. The heat capacity and thermal conductivity of the mixtures with different fractions of the components are measured in a laboratory. The measured data agree with simulated results. Better thermal properties can be achieved with specific fractions of components, and the findings could help geothermal systems design for better energy utilisation.
 Geothermal energy is one of the promising renewable energy sources and its utilisation can be an alternative to fossil fuels. A geothermal system requires a ground source heat exchanger with pipes installed inside a borehole, and backfill materials filling the gap between the pipe heat exchanger and the ground. Thus, the thermal properties of backfill materials are essential to the geothermal energy extraction process and influence the corresponding shallow geothermal system performance [2]. PCMs are used to improve the thermal storage capacity of backfill materials because they can absorb and release heat at a relatively constant temperature [1]. To avoid problems of leakage and volume change of PCMs during a phase change, encapsulated PCMs (EPCMs) are better suited in backfill materials [5]. However, mixtures including PCMs may hinder heat transfer because of their low thermal conductivity. Therefore, other additives with high thermal conductivity can be used to resist the low heat transfer rate [3]. Even though the thermal properties of backfill materials are fundamental to the geothermal energy extraction process, their dependence on the amount of added PCMs and other additives has not been investigated yet. This work mixes EPCMs, graphite and recycled glass fines, aiming to develop green backfill materials with excellent thermal properties. The heat capacity (), thermal conductivity () and thermal diffusivity () of the mixtures with different fractions of the components are measured in a laboratory.
 SEM images of materials used, recycled glass fines, EPCMs and graphite, are shown in Figure 1(a). Cylindrical containers with a diameter of 44 mm and a height of 57 mm are used to prepare samples of mixtures. Each sample has the controlled volume fractions of components indicated by Figure 1(b) while keeping a constant overall porosity of 0.47. A decagon KD2 Pro thermal analyzer with a dual thermal needle measures the thermal properties of samples kept at 4 °C when EPCMs are in the solid phase and 45 °C when EPCMs are in the liquid phase. The geometrical mean model is used for theoretical estimations of values for comparison against experimental results [4].
 
 The thermal conductivity () of the mixtures increases with increasing graphite volume while decreasing with increasing EPCMs volume, as shown in Figure 1(c). The difference between under solid EPCMs and liquid EPCMs is limited. The heat capacity () rises with increasing EPCMs volume but declines with the increase of graphite volume, and it is higher when EPCMs are liquid than solid. It can be observed that a trade-off between the improvement of and the reduction of exists. Hence, the thermal diffusivity (), which depends on the ratio of to , is also investigated as presented in Figure 1(d). It decreases with the increase of EPCMs volume but grows with increasing graphite volume. Besides, it is higher under solid EPCMs than that under liquid EPCMs. This indicates the backfilling materials have a faster thermal response to the change of surrounding temperature under solid EPCMs.

A Case Study on the Convection Initiation Mechanisms over the Northern Edge of Tarim Basin, Xinjiang, Northwest China

The convection initiation (CI) mechanisms of severe storms have received increasing attention because severe storms have been occurring more frequently around the globe in recent years. In this work, the CI mechanisms of severe convective weather associated with a gust front (GF) which occurred on 9 July 2016, near the Korla at the northern edge of the Tarim Basin, Xinjiang, is investigated using observational data including Doppler weather radar data and automatic weather stations data, and high-resolution numerical simulation data. The results showed that, during the eastward movement of the GF, a number of convective cells were successively triggered in the vicinity of the GF, which developed rapidly and continuously merged with the convective system from behind, resulting in the further development and maintenance of this convective system. According to the diagnostic analysis of vertical acceleration which can be decomposed into dynamic acceleration (ad) and buoyant acceleration (ab), it was found that both ad (up to ~4 × 10−3 m s−2) and ab (up to ~7 × 10−3 m s−2) made positive contributions to the CI. Further analyses based on the decompositions of the ad and ab revealed that the extension term was the main contributor for the ad, while the warming of the dry air due to the release of latent heat from the precipitation condensate made the major contribution to the ab. The extension term indicates the elevated convergence jointly induced by the airflow of mid-level horizontal convective rolls (MHCRs) and updraft flow near the leading edge of the GF. The jointly induced elevated convergent updraft can be considered to be an important contributor for the CI mechanisms.