Water-ice Phase Research Articles

A novel low-temperature thermo-mechanical coupling model for frost cracking simulation using the finite-discrete element method

Frost cracking is widely prevalent in cold areas and is typically associated with the deterioration of rock masses. A better understanding of the frost cracking mechanism and precise prediction of the associated crack evolution are essential for the safety and long-term service life of engineered rock structures in cold regions. This paper presents a low temperature thermo-mechanical (TM) coupling modeling framework, implemented into the combined finite-discrete element method (FDEM), to simulate the frost crack evolution in rock masses, considering the heat transfer, water–ice phase transition, and the induced frost heaving pressure. Existing benchmark tests were used to calibrate and verify the proposed modeling framework. Moreover, experimental and numerical results from freezing experiments conducted on samples containing pre-existing cracks have been successfully reproduced the complex mechanisms that lead to crack initiation and propagation in jointed rock formations where cracks driven by the water–ice phase transition initiate and propagate from the pre-existing cracks and deviate under the influence of confining stress and multi-crack interactions (i.e., stress shadow effect). This novel numerical framework presents a potentially useful tool to further understand frost cracking mechanisms and frost crack evolution of engineering projects in cold environments.

Mathematical Modeling of Gas Hydrates Dissociation in Porous Media with Water-Ice Phase Transformations Using Differential Constrains

2D numerical modeling algorithms of multi-component, multi-phase filtration processes of mass transfer in frost-susceptible rocks using nonlinear partial differential equations are a valuable tool for problems of subsurface hydrodynamics considering the presence of free gas, free water, gas hydrates, ice formation and phase transitions. In this work, a previously developed one-dimensional numerical modeling approach is modified and 2D algorithms are formulated through means of the support-operators method (SOM) and presented for the entire area of the process extension. The SOM is used to generalize the method of finite difference for spatially irregular grids case. The approach is useful for objects where a lithological heterogeneity of rocks has a big influence on formation and accumulation of gas hydrates and therefore it allows to achieve a sufficiently good spatial approximation for numerical modeling of objects related to gas hydrates dissociation in porous media. The modeling approach presented here consistently applies the method of physical process splitting which allows to split the system into dissipative equation and hyperbolic unit. The governing variables were determined in flow areas of the hydrate equilibrium zone by applying the Gibbs phase rule. The problem of interaction of a vertical fault and horizontal formation containing gas hydrates was investigated and test calculations were done for understanding of influence of thermal effect of the fault on the formation fluid dynamic.

Phase Transition between Crystalline Variants of Ordinary Ice.

Water is one of the most abundant molecules on Earth. However, this common and "simple" material has more than 18 different phases, which poses a great challenge to theoretically study the nature of water and ice. We designed two reaction coordinates that can distinguish between water and various ice states and used them to efficiently sample all possible states of the system in all-atom molecular dynamics simulation at ambient temperature and pressure. Various structural and thermodynamics properties, including the water-ice phase diagrams, can thus be calculated. We also present a simple model that successfully explains the thermodynamic stability of different ice states. Our work provides effective methods and data for theoretical studies of different phases of water and ice.

Thermal-hydro-mechanical coupled analysis of unsaturated frost susceptible soils

Damage caused by frost heave leads to costly maintenance in cold regions, like Hokkaido, Japan. Therefore, the study of the frost mechanism with experimental and numerical methods has been of great interest. Numerous models have been developed to describe the freezing process of saturated soil, which differs from the partially saturated conditions in the field. In fact, most subsurface soils are unsaturated. The freezing process of partially saturated soils is more complex than saturated soils, as the governing equations show strongly nonlinear characteristics. This study proposes a thermo-hydro-mechanical coupled model considering the heat transfer, water infiltration, and deformation of partially saturated soil to reproduce the freezing process of partially saturated frost susceptible soils distributed in Hokkaido. This model better considers the water-ice phase change and soil freezing characteristic curve (SFCC) during freezing under field conditions. The results from the multiphysics simulations agree well with the frost heave and water migration data from frost heave tests of Touryo soil and Fujinomori soil. In addition, this study discussed the influence of the various factors on frost heave amount, including temperature gradients, overburden pressures, water supply conditions, cooling rates, and initial saturation. The simulation results indicate that the frost heave ratio is proportional to the initial degree of saturation and is inversely proportional to the cooling rate and overburden pressure.Moreover, simulation under the open system generates much more frost heave than under the closed system. Finally, the main features of the proposed model are revealed by simulating a closed-system frost heave test. The simulation results indicate that the proposed model adequately captures the coupling characteristics of water and ice redistribution, temperature development, hydraulic conductivity, and suction in the freezing process. Together with the decreased hydraulic conductivity, the increased suction controls the water flow in the freezing zone. The inflow water driven by cryogenic suction gradient feeds the ice formation, leads to a rapid increase in total water content, expanding the voids that exceed the initial porosity and contributing to the frost heave.

Investigating unfrozen water and its components during freeze–thaw action in loess using a novel NMR technique

AbstractFrost heave and thaw settlement are primarily caused by water migration. Variations in liquid water and its components during freezing and thawing are crucial variables for investigating water migration. Here, a novel soil layer‐scanning method based on magnetic resonance imaging cryogenic soil‐moisture analysis (MRI‐CSMA) was applied to measure dynamic changes of liquid water and its components in nine layers (each 11.1‐mm thick) of four loess samples with different initial water contents (9.2%, 15.7%, 20.0%, and 30.0%) in freezing–thawing experiments under a closed system. The ice–water phase transition and water migration were key factors that controlled the liquid water and its components. During freezing, the liquid water content of each layer (except layer 7) decreased. In the frozen zone (layers 1–6), the liquid water content decreased with decreasing temperature owing to the water–ice phase transition. The lower the temperature, the higher the fraction of water that transitioned to ice. In the unfrozen zone (layers 8–9), parts of the liquid water migrated upward owing to the suction generated at the freezing front. The farther away the freezing front, the smaller the suction and quantity of water migration. During thawing, the liquid water content of each layer increased owing to the ice–water phase transition in the frozen zone and infiltrated down to the unfrozen zone. The contents of the free and adsorbed water exhibited similar change trends to the liquid water content during freezing. However, the change degree of free water was much larger than that of adsorbed water because the phase transition and migration of free water is easier than that of absorbed water. Notably, the liquid water content near the freezing front (layer 7) increased in the early stage of freezing, owing to the combined effect of soil compression and the water–ice phase transition. These results provide a reference for research on water migration in the soil during freezing–thawing and validate the advantage of MRI‐CSMA when characterising water migration in large soil samples.Highlights A novel device (MRI Cryogenic Soil‐Moisture Analyzer) was used. Variations in unfrozen water and its components during freezing were studied. Soil consolidation and pore pressure affect the liquid water change during freezing.

Calorimetry based temperature and specific enthalpy measurements associated with ice-water phase change in saline systems for freeze desalination

Ice based Freeze Desalination (FD) offers a potential alternative to recover fresh water from seawater. However, ice-water phase change data in saline water in the range of practical interest and of importance in FD process design is limited. In this study, reliable and accurate measurements related to ice–water phase change temperatures and specific enthalpies have been carried out using a Micro–Differential Scanning Calorimeter (μ–DSC). The runs were carried out using pure water, synthetic salt water (0.5 to 5 wt% NaCl) and seawater. The NaCl concentrations covered a range of values of practical interest in FD. In the case of pure water, the specific enthalpy value was found to be in excellent agreement to within ± 0.51% of the value reported in literature, i.e. 333 J/g which validated the experimental protocols adopted in this study. Phase change temperature and specific enthalpy values for salt water were found to decrease with an increase in salt concentration. Test runs conducted subsequently using seawater were consistent with the results obtained from the synthetic salt water test runs. The experimental protocol adopted and data presented in this study can be used in design of an ice based FD process.

A Study on the Freeze–Thaw Damage and Deterioration Mechanism of Slope Rock Mass Based on Model Testing and Numerical Simulation

Engineering rock mass in cold regions has obvious freeze–thaw damage as a result of extreme differences in temperature, rainfall, snow, and other factors, which is one of the main causes of frequent geological disasters. Therefore, it is important to investigate the deterioration mechanism and evolution laws of rock mass freeze–thaw damage. Considering a hydropower station’s left bank slope in a cold region, model testing and numerical testing of slope rock mass failure under freeze–thaw conditions are here carried out by developing a generalized model. The results reveal that heat is transmitted from the outside to the inside of the slope and that the rate of temperature change varies with depth; the frost-heave force causes tensile cracks in the rock mass, with crack propagation taking the form of a circular arc; the presence of an original structural plane influences the propagation direction of the frost-heave crack, whereas the freezing rate of the fissure water influences the amplitude and growth rate of the frost-heave force. Additionally, a novel method of measuring frost-heave force is proposed. The largest frost-heave force caused by water–ice phase change is 19.3 kPa, which is equivalent to 3.17 MPa of the actual slope.

Analysis on the evolution of frost heaving pressure of penetrating crack considering water content and migration

Frozen heaving failure of fractured rock mass is commonly encountered in engineering in cold regions, which is chiefly caused by the frost heaving pressure arising from the water–ice phase change in the crack. To explore the evolution of frost heaving pressure in penetrating elliptical crack considering water content and water migration, a new theoretical model embodying the frost heaving pressure evolutionary character was established by introducing freezing ratio function. The equivalent thermal expansion coefficient was used to analyze the evolution process of frost heaving pressure under the effect of water–ice phase change, which was then verified. It was found that the evolution process of frost heaving pressure can be divided into three stages: free expansion stage of water–ice phase change, rapid growth stage of frost heaving pressure, and stable stage of frost heaving pressure. Subsequently, the influences of rock thermal expansion effect, properties of rock and ice, and water content of crack on the frost heaving pressure were investigated. The results indicate that the impact of rock thermal expansion on frost heaving pressure is extremely slight, which is negligible. Comparing with the properties of rock, the properties of ice show significant effects on the frost heaving pressure, particularly the Poisson ratio of ice. In the case of identical water migration ratio, the peak frost heaving pressure increases linearly with the water content of crack.

Modeling heat and mass transfer during artificial ground freezing considering the influence of water seepage

In the system of artificial ground freezing under water seepage, the dynamic liquid–ice phase equilibrium relationship considering the contribution of water seepage pressure was established based on the classical thermodynamics fundamentals. The freezing characteristic function was represented by combining the Young–Laplace law with van Genuchten model. A thermal-hydraulic model of saturated porous media considering dynamic liquid–ice phase equilibrium was established and validated thorough laboratory tests under various seepage velocities. The temperature field evolution laws of sand, silty and clay grounds were studied based on the thermal-hydraulic model. The temperature field development laws of primary side tunnel of subway cross passages in silty-clay layer were analyzed by applying the thermal-hydraulic model. The relationship between water seepage pressure and the decrease of water freezing point temperature was obtained according to the dynamic liquid–ice phase equilibrium. Compared with the simulation results of considering static liquid–ice phase equilibrium relationship, considering the dynamic liquid–ice phase equilibrium relationship changes the distribution of water-ice phase transition front and has significant influence on the temperature evolution in silty ground. However, that influence in sand ground and clay ground is insignificant because of the relatively lower water seepage pressure in sand ground and poor thermal conductivity in clay ground. Due to the cold energy accumulation bring by water seepage, the freezing rate in the downstream of freezing pipes is faster than that in the upstream of freezing pipes. This effects are exacerbated by lower decrease of water freezing point temperature caused by minor water seepage pressure in the downstream of freezing pipes. Four representative temperature measured points were selected to acquire the relationship between simulation and on-site temperatures. It was observed that the trends of simulation results reflect the tunnel freezing process well.

Pore structure evolution in andesite rocks induced by freeze–thaw cycles examined by non-destructive methods

In this paper, we compare the values of petrophysical properties before and after 100 freeze–thaw (F–T) cycles, as well as recorded length change behaviour and temperature development on a vacuum-saturated fractured andesite rock sample taken from the Babina Quarry in Slovakia using a specially-constructed thermodilatometer, VLAP 04, equipped with two HIRT-LVDT sensors. We also used non-destructive visualization of the rock pore network by µCT imaging in order to study the development of the pore structure and fracture network in pyroxene andesites during the freeze–thaw process. The results show that the andesite rock samples, due to good fabric cohesion, low porosity, and low pore interconnection, showed good resistance against frost-induced damage. However, it must be stated that the main process causing disintegration of this type of rock is fracture opening, which is caused by internal stresses induced by water–ice phase transition. The overall residual strain recorded after 100 F–T cycles was not significant, however, the increase of 31 pp in volume of the fracture showed us that repeated freezing and thawing can lead to long term deterioration in terms of subcritical crack growth in brittle-elastic solids like pyroxene-andesite rocks.

Laboratory experiments on the radiation astrochemistry of water ice phases

Water (H2O) ice is a ubiquitous component of the universe, having been detected in a variety of interstellar and Solar System environments where radiation plays an important role in its physico-chemical transformations. Although the radiation chemistry of H2O astrophysical ice analogues has been well studied, direct and systematic comparisons of different solid phases are scarce and are typically limited to just two phases. In this article, we describe the results of an in-depth study of the 2 keV electron irradiation of amorphous solid water (ASW), restrained amorphous ice (RAI) and the cubic (Ic) and hexagonal (Ih) crystalline phases at 20 K so as to further uncover any potential dependence of the radiation physics and chemistry on the solid phase of the ice. Mid-infrared spectroscopic analysis of the four investigated H2O ice phases revealed that electron irradiation of the RAI, Ic, and Ih phases resulted in their amorphization (with the latter undergoing the process more slowly) while ASW underwent compaction. The abundance of hydrogen peroxide (H2O2) produced as a result of the irradiation was also found to vary between phases, with yields being highest in irradiated ASW. This observation is the cumulative result of several factors including the increased porosity and quantity of lattice defects in ASW, as well as its less extensive hydrogen-bonding network. Our results have astrophysical implications, particularly with regards to H2O-rich icy interstellar and Solar System bodies exposed to both radiation fields and temperature gradients.Graphical abstract

Strategy optimization of proton exchange membrane fuel cell cold start

<p indent="0mm">Under the background of “carbon peaking and carbon neutrality” goals, the proton exchange membrane fuel cell (PEMFC) vehicle attracts extensive attention due to its high energy conversion efficiency, long range and zero emission. However, the challenge of cold start in low temperature environments becomes a large obstacle to its commercialization and application. The current cold start performance of typical commercial fuel cell vehicles cannot reach the optimal target yet. Several problems such as the lack of complete mechanical systems of water transport and phase change and the absence of simulation models for on-board fuel cells at system level still exist. Thus, researchers have carried out a great number of experiments and simulations to study the mechanism of degradation, water transport, phase change and heat transfer as well as start-up strategy optimization of PEMFC cold start. By measuring the output performance, it is found that the degradation of performance is attributed to the formation of ice which covers the reaction active region, blocks the gas channel and increases the electrical contact resistance. Researchers also believe that the reduction of durability is owing to the volume change of water-ice phase change which leads to the damage of the structure by characterizing the microstructure of the fuel cell. With the help of transparent cells, neutron imaging and simulations of multiphase PEMFC models, the distribution, transport and phase change of water and ice during cold start have been studied. The results indicate that the electrochemical product water first saturates the PEM and the catalyst layer (CL) as membrane water. Then the water remains liquid in the form of supercooled water at low temperatures, and finally flows out of the cell or freezes suddenly. By studying the heat transfer process both in plane and through plane during cold start, researchers find that at central regions of the single cell and in the middle part of the stack, the temperature rises fastest. They also find that the irreversible reaction heat generated by cathodic oxygen reduction reaction (ORR) is the main source of heat generation. Based on the cold start mechanism of PEMFCs, researchers have developed various self-start and auxiliary start strategies. The start-up mode and control strategies have been optimized. The internal structure and materials of each part have been improved. And a series of auxiliary startup strategies such as gas purging, heater heating, reaction heating, gas heating as well as coolant heating have been proposed. A large number of simulations and experiments are carried out to verify the advantages of these strategies. Through these excellent cold start strategies, the commercialization and promotion process of PEMFC vehicles can be accelerated.

Experimental study on deformation characteristics of chloride silty clay during freeze-thaw in an open system

Artificial ground freezing (AGF) is widely applied in coastal urban areas for underground transportation infrastructure construction. It is vital to understand deformation characteristics and the mechanisms of chloride soils during freeze-thaw (F-T) for the safe application of AGF. A series of unidirectional open-system F-t-tests were conducted to investigate the deformation characteristics of saturated clay with various NaCl content. Continuous measurements were performed on important parameters such as temperature, solution intake volume, frost heave, and thaw settlement during F-T. Besides, the pore size distributions were obtained via the Nuclear Magnetic Resonance relaxometry to help reveal the deformation mechanism. The results indicated that the freezing front propagated rapidly (Phase I) and then reached a plateau at the thermal equilibrium stage (Phase II). The location of the freezing front in Phase II was dependent on salt content. The amount of solution intake decreased with increased salt content. The rate of solution intake in two phases was also found to be salt content-dependent, while for a certain specimen the order of the rates in two phases varied with increasing salt content. The total frost heave for the same freeze time decreased with increasing salt content and the solution intake induced frost heave mainly contributed to the total frost heave. Total thaw settlement was relatively insensitive to the salt content of higher values. At the end of freezing and thawing processes, minimal frost heave ratio and thaw settlement coefficient were both identified in the specimen with 1% salt content. Moreover, the evolution of pore structure was found to be more prominent in specimens with lower salt content due to more water-ice phase change during freezing, which caused more significant frost heave.

How do antifreeze proteins inhibit Ostwald ripening of ice crystals?: analyzing local surface curvature changes at high resolution

Many lifeforms produce ice-binding proteins, sometimes referred to as antifreeze proteins, that can protect them against frost-damage by controlling the nucleation and growth of ice crystals. Our goal is to elucidate how these proteins can modulate the water-ice phase transition and function as such remarkable cryo-protectants. Specifically, we seek to directly resolve how antifreeze proteins dynamically organize at the solid-liquid interface and interact with advancing ice-crystal planes. To this end, we have developed a new experimental approach that is suited for high-resolution imaging of ice crystals and for fluorescence microscopy for localization of single proteins.

Experimental and unified mathematical frameworks of water-ice phase change for cold thermal energy storage

Cold thermal energy storage (CTES) is a process that supplies cold thermal energy to a medium for storage and extracts it whenever is needed. The storage medium is phase change material (PCM), which makes great use of the large quantity of latent heat released during solidification or melting. However, some key fundamental and applied issues have not yet been resolved: how do we overcome the thermal interference in PCMs from unstable microscopic crystallization and external mechanical forces? Are there any unified and robust models to predict the whole time evolution of phase change accurately and rapidly? To fulfill these research gaps, we firstly establish a novel, well-controlled experimental system for PCMs that mitigates the thermal disturbance over a medium to large volume during solidification, capable of measuring transient temperature data and characterizing freezing stages at both macro- and micro-scale. We also develop in detail a unified semi-analytical mathematical framework to model the solidification of PCMs, consisting of five subsequent stages: liquid supercooling, nucleation, recalescence, equilibrium freezing, and solid subcooling. The modeling results yield a good agreement with our experimental data in several scenarios, particularly the nucleation temperature and time as well as the total freezing time are accurately predicted. Lastly, we extend our study to investigate the thermal effects of various radial positions, geometries, initial temperatures, heat transfer fluid temperature, and heat transfer coefficients in the context of CTES system.

Numerical analysis of cooling performance of a novel structure affected by aeolian sand clogging on expressway embankment in permafrost regions

As an efficient and economical engineering measure, the inverted T-shaped crushed-rock interlayer is used to protect the permafrost under expressway. Its cooling performance is threatened by the climate warming, strong heat absorption of asphalt pavement and aeolian sand on the Qinghai-Tibet Plateau. However, the influence effect of the aeolian sand is unclear. In this study, a hydro-thermo coupled model, including ice-water phase change, heat and water transfer, and air convection heat transfer in the crushed rock, is established to simulate and evaluate the cooling performance of the inverted T-shaped crushed-rock interlayer affected by aeolian sand clogging. A novel structure combining the L-shaped two-phase closed thermosyphons with the inverted T-shaped crushed-rock interlayer is proposed to satisfy the strict requirement of expressway. The numerical results show that the cooling effect of the inverted T-shaped crushed-rock interlayer on the underlying permafrost is influenced by aeolian sand to some extent, whose cooling effect is weak and concentrated at the embankment center. Permafrost beneath expressway was still degenerated, which is unfavorable for the long-term stability of expressway embankment. The novel structure can overcome the adverse effect of aeolian sand, produce a significant cooling performance on the permafrost under the embankment, and maintain the thermal stability of expressway embankment. Under the threat of aeolian sand, this novel structure is a candidate structure for the expressway embankment in permafrost regions.

Experimental Study on the Effect of Freezing and Thawing on the Shear Strength of the Frozen Soil in Qinghai-Tibet Railway Embankment

The direct shear tests of different dry density and moisture content samples at different temperatures of the frozen soil in the Qinghai-Tibet Railway embankment between Tanggula South and Anduo section were carried out to analyze the influence rules of each experimental factor on the mechanical properties of frozen soil during the freeze-thaw process. The results show the following. (1) When the frozen soil temperature is below 0°C and continues to drop during the freezing and thawing process, each sample shows the law of a significant increase in cohesion and a slight decrease in the internal friction angle. In the meantime, the cohesion obtained during the thawing process of the sample at the same temperature point is higher than that obtained during the freezing process. In contrast, the internal friction angles exhibit an opposite law, where the internal friction angle during the melting process is lower than the internal friction angle during the freezing process. After freezing-thawing action, it deserves to be mentioned that the cohesion increases slightly while the internal friction angles present a slight decrease trend compared to the initial state. (2) With the decrease in temperature and the gradual increase in cohesion, the temperature curve can be divided into a fast-growing section from 0 to −2°C, a slow-growing section from −2 to −8°C, and a second fast-growing section from −8 to −10°C owing to the combined effect of the pressure-thawing action and ice-water phase change. In addition, the rate of decrease in the internal friction angle also shows a similar pattern. (3) The cohesion and the internal friction angle of samples both tend to increase first and then decrease with the rise of the initial moisture content, and the critical initial moisture content is near the optimal moisture content of 15%. (4) Both the cohesion and the internal friction angle of the samples increase with dry density growth. The growth rate of cohesion will gradually increase as the temperature decreases. Moreover, the growth rate of cohesion of low dry density samples is more susceptible to temperature, while the internal friction angle growth rate is not affected by temperature.

Rayleigh-Bénard Convection and Freezing Propagation During Water-Ice Phase Change

Rayleigh-Bénard Convection and Freezing Propagation During Water-Ice Phase Change

Математическое моделирование диссоциации газовых гидратов в пористой среде с учетом льда и соли

In the work, the method of splitting by physical processes is consistently applied to the problems of underground hydromechanics associated with gas hydrates and taking into account the presence of ice and the ice-water phase transition, as well as the presence of salt. The systems are reduced to the block form, with the separation of the dissipative and hyperbolic parts. It was shown by the method of characteristics that the usual approximation of the upwind coefficients should be modified here. Using the Gibbs phase rule, a choice was made of the determining variables in the flow zones that differ from each other in the number of phases and components. A general mathematical model has been built for the entire area of the process.

Experimental Study of Dynamic Mechanics Characteristics of Saturated Marble under Low Temperature

The effect of low temperature on dynamic mechanical properties of low-temperature frozen marble at a high strain rate was studied by a dynamic impact test. The influence of temperature changes (25°C–40°C), especially negative temperature changes, on dynamic strength, peak strain, and failure mode of the marble was analyzed. Combined with the fracture morphology, the reasons for the deterioration of dynamic mechanical strength of water-saturated marble at lower negative temperatures were investigated. The experimental results show that the dynamic mechanical properties of marble are significantly affected by the change of freezing temperature. The dynamic strength firstly decreases and then increases with the decrease of temperature in the range of 25°C to −20°C, but the dynamic strength decreases sharply after −20°C. The peak strain increases first, then decreases, and then increases, and the inflection point temperature of the change is −5°C and −20°C, respectively, which is completely different from the static load test results of frozen rock at low temperature. According to fracture morphology analysis, water-ice phase transformation at −5°C leads to the nucleation and expansion of a large number of microcracks and micropores in marble, and the interaction between slip separation cracks and microstructures caused by shear deformation under impact separates the massive crystals inside the rock into microscopic crystals, thus reducing the bearing capacity and strength of marble. From −5°C to −20°C, the ice medium and marble matrix contract when cooled, and the microcracks and micropores caused by the phase transition gradually close during the contraction process, the integrity of the rock is restored, and the dynamic strength of the rock is increased. At −20°C, there is a great difference in the shrinkage rate of the marble matrix and the ice medium, and the internal microstructure increases. Meanwhile, the impact amplifies the brittleness of the rock at low temperatures, leading to a sharp decrease in the dynamic strength of the marble.