High Freezing Temperature Research Articles

Experimental investigation and strength model of rough ice-filled joints under tensile and shear loading

Warming softening of ice-filled joints has caused many rockfall disasters in cold regions. A series tensile and shear strength tests were conducted to investigate the thawing softening mechanism of ice-filled joints by considering the effect of the joint opening, temperature and roughness. The joint opening has little influence on the tensile strength of ice-filled joints, but the temperature is a remarkable influencing factor. When the temperature increases from −15 °C to −0.5 °C, the average tensile strength of ice-filled joint reduces from 0.64 MPa to 0.22 MPa, which displays a constant logarithmic decay function against the freezing temperature and it is similar to the change rule of pure ice. The shear strength of the ice-filled joint decreases with increasing the infill thickness, and tends to be the shear strength of pure ice beyond the critical infilling thickness. In addition, all the tensile failures are inside the joint ice, however, the shear failure is mainly caused by the debonding of ice-rock interface when the temperature increases to −0.5 °C. It implies that the tensile bonding strength of ice-rock interface also is larger than that of the solid ice itself even at a high freezing temperature. Based on the experimental results, a new shear strength model of the ice-filled joint is proposed for Barton's joint profiles by considering the effect of temperature and infill thickness. It has been validated that this model is accurate to predict the shear strength of ice-filled joint, which may be used to estimate the stability of freezing joint rock slope in cold regions.

Operation performance of an ultralow-temperature cascade refrigeration freezer with environmentally friendly refrigerants R290-R170.

In the present study, the operation performance of an ultralow-temperature cascade refrigeration freezer is experimentally researched. The natural refrigerants R290-R170 are adopted as high-temperature and low-temperature fluids. The experimental test is conducted in a type laboratory with a dry bulb temperature of 32.0°C and awet bulb temperature of 26.5°C. Different state monitors are set to display the system operation performance, and several temperature monitors are arranged to study the pull-down performance and temperature variations in the freezer. Based on the established experimental rig, three freezing temperatures, including - 40°C, - 80°C, and - 86°C, are measured and compared. The results show that it takes about 240min for the freezer to be pulled down to - 80°C. During the pull-down period, different monitors all experience rapid temperature drop, and the power consumption reduces from 1461.4W to 997.5W. Once the target temperature is achieved, the freezer comes into periodic start-stop operation. With the set temperature ranging from -40°C to -86°C, the inlet temperature of two compressors gradually decreases, while the discharge temperature has an increase trend. The cooling effect of the pre-cooled condenser reduces with the freezing temperature, while the long connection pipe has opposite variation profile. Moreover, it is observed that for different freezing temperatures, most of the space in the freezer can be cooled down to the target temperature. It is confirmed that the present ultralow-temperature freezer can be used for the storage and transportation of COVID-19 vaccines. However, it is also found that the cascade refrigeration system is not suitable for high freezing temperature, due to high power consumption and extensive start-stop switch of refrigeration system.

The study of new employment areas for used motor oils

The paper studies the perspective of applying a regeneration product of Mysella-40 used motor oil of Shell Company, which has high viscous-temperature properties, high flash point and low freezing temperature used in the modern power stations of module type. As a result of the studies based on the regeneration product of Мycella-40 motor and M-8 Baku oils obtained through the refinement of Azerbaijani oil mixtures and some additives of various functionalities, new lubricating compositions of motor oils for diesel engines of different purposes have been developed.

Cultivable halotolerant ice-nucleating bacteria and fungi in coastal precipitation

Abstract. Ice-nucleating particles (INPs) represent a rare subset of aerosol particles that initiate cloud droplet freezing at temperatures above the homogenous freezing point of water (−38 ∘C). Considering that the ocean covers 71 % of the Earth's surface and represents a large potential source of INPs, it is imperative that the identities, properties and relative emissions of ocean INPs become better understood. However, the specific underlying drivers of marine INP emissions remain largely unknown due to limited observations and the challenges associated with isolating rare INPs. By generating isolated nascent sea spray aerosol (SSA) over a range of biological conditions, mesocosm studies have shown that marine microbes can contribute to INPs. Here, we identify 14 (30 %) cultivable halotolerant ice-nucleating microbes and fungi among 47 total isolates recovered from precipitation and aerosol samples collected in coastal air in southern California. Ice-nucleating (IN) isolates collected in coastal air were nucleated ice from extremely warm to moderate freezing temperatures (−2.3 to −18 ∘C). While some Gammaproteobacteria and fungi are known to nucleate ice at temperatures as high as −2 ∘C, Brevibacterium sp. is the first Actinobacteria found to be capable of ice nucleation at a relatively high freezing temperature (−2.3 ∘C). Air mass trajectory analysis demonstrates that marine aerosol sources were dominant during all sampling periods, and phylogenetic analysis indicates that at least 2 of the 14 IN isolates are closely related to marine taxa. Moreover, results from cell-washing experiments demonstrate that most IN isolates maintained freezing activity in the absence of nutrients and cell growth media. This study supports previous studies that implicated microbes as a potential source of marine INPs, and it additionally demonstrates links between precipitation, marine aerosol and IN microbes.

Preparation, characterisation and energy storage performance study on 1-Decanol-Expanded graphite composite PCM for air-conditioning cold storage system

Abstract Performance of a typical ice-based cold thermal energy storage system (CTESS) is immensely affected by its supercooling nature and low freezing temperature (0 °C). In this study, 1-Decanol (PCM) was recognised as a potential replacement for ice as it is cost-effective as well as having zero degree of supercooling, and high freezing temperature (5 °C). High thermal conductivity PCM-Expanded graphite (EG) composite (CPCM) was prepared by incorporating the PCM into the porous structure of EG. The thermal conductivity, specific heat, and thermal cycling stability of CPCM were studied. Further, the charging and discharging characteristics of CPCM were investigated in a 64 mm diameter spherical capsule at -3 °C and 13 °C wall temperatures, respectively. CPCM has an incorporation efficiency of 84.99%, and its thermal conductivity is 16.33 times higher than that of PCM. CPCM and PCM have good thermal reliability for 1000 cycles. The freezing temperature of CPCM is ∼4.1 °C higher than that of ice and its charging time is 81.85% lower than that of PCM, which signifies that the chiller operating time can be reduced by 81.85% to store the specified amount of energy in CPCM. Further, the time-averaged charging and discharging rate of CPCM is 5.51 and 5.97 times higher than that of PCM, respectively. Experimental results concede that CPCM is having high freezing temperature (∼4.1 °C), zero degree of supercooling and enhanced energy storage characteristics, which ensure that the utilisation of CPCM paves the way for efficiently storing and recovering the energy.

Water Freezes at Near-Zero Temperatures Using Carbon Nanotube-Based Electrodes under Static Electric Fields.

Although static electric fields have been effective in controlling ice nucleation, the highest freezing temperature (Tf) of water that can be achieved in an electric field (E) is still uncertain. We performed a systematic study of the effect of an electric field on water freezing by varying the thickness of a dielectric layer and the voltage across it in an electrowetting system. Results show that Tf first increases sharply with E and then reaches saturation at -3.5 °C after a critical value E of 6 × 106 V/m. Using classical heterogeneous nucleation theory, it is revealed that this behavior is due to saturation in the contact angle of the ice embryo with the underlying substrate. Finally, we show that it is possible to overcome this freezing saturation by controlling the uniformity of the electric field using carbon nanotubes. We achieve a Tf of -0.6 °C using carbon nanotube-based electrodes with an E of 3 × 107 V/m. This work sheds new light on the control of ice nucleation and has the potential to impact many applications ranging from food freezing to ice production.

Unidirectional solution-based freeze cast polymer-derived ceramics: influence of freezing conditions and templating solvent on capillary transport in isothermal wicking

Porous SiOC monoliths were prepared by solution-based freeze casting of polysiloxane at constant freezing temperature or constant freezing front velocity. Dendritic and prismatic pore structures were obtained by using cyclohexane and tert-butyl alcohol as solvent, respectively. Gradients in freezing velocity lead to gradients in pore window size, whereas a constant freezing velocity (3.3–6.8 µm/s) generates homogeneous pore structures. The water permeability varies from 1.12 × 10−13 to 1.03 × 10−11 m2 and correlates with the pore window diameter (10–59 µm) and the porosity (51–82%). In wicking tests, the gradient in pore window size is clearly reflected by a pronounced decrease in the wicking speed. Contrary, a homogeneous pore structure results in wicking curves which are closer to the prediction according to the Lucas–Washburn equation. However, this theoretical approach based on the three parameters, pore window size, porosity and permeability, is insufficient to describe complex three-dimensional pore structures. Besides the porosity, the pore morphology was found to be a major influencing factor on the wicking. The filling of secondary dendrites slows down the wicking into the dendritic structure. Fastest wicking was observed for a prismatic pore structure at low freezing front velocity (6.6 µm/s) and high porosity (78%), whereas slowest wicking occurred into the dendritic structure with high porosity (76%) and constant freezing temperature (− 20 °C). The knowledge of the relationship between structural properties and the resulting wicking behavior can address a variety of pivotal applications in chemical engineering for capillary transport.

Dielectric behaviors and relaxor characteristics in Bi0.5Na0.5TiO3-BaTiO3 ceramics

Microstructure and dielectric behaviors of heating/cooling and bias-field were investigated in lead-free ceramics ([Formula: see text])[Formula: see text][Formula: see text][Formula: see text]BaTiO3 (BNT[Formula: see text]BT, [Formula: see text], 0.02, 0.04, 0.06, 0.08 and 0.10). The relaxor characters and the Vogel–Fulcher law of frequency-dependent dielectric properties were analyzed. Three dielectric anomalies with pronounced frequency dispersion at [Formula: see text], a maximum dielectric with variable frequency-dispersion at [Formula: see text] and a third Maxwell–Wagner-type relaxation over a wide temperature range in high-temperature region were observed. The significant dielectric thermal hysteresis, low barrier energy, high freezing temperature in heating process and the maximum dielectric tunability appeared in [Formula: see text] ceramic.

Engineering aspects and thermal performance of molten salt transfer lines in solar power applications

Concentrating solar thermal power coupled with thermal energy storage is considered as one of the leading technologies to address the decarbonization of the energy sector. The use of molten solar salt (60–40% b.w. NaNO3-KNO3) as heat transfer fluid and thermal storage medium is the current commercial practice, with alternative salt mixtures being under evaluation for the next-generation higher-temperature systems. The main drawback of the molten salts is their high freezing temperature; active means are required for preheating of- and to prevent salt from freezing in- the transfer lines.In this article we present experiences from the PROTEAS facility, where heating tapes as opposed to heating cables are used. The thermal energy losses from the transfer lines are evaluated and compared to those predicted by a one-dimensional heat transfer analysis. Thermal losses between 43 and 100 W/m are found at operating temperatures from 300 to 500 °C. A joint optimization of the capital and operational expenditure for heating tapes and insulation is performed, leading to the optimal insulation thickness and installed heat tracing capacity. Increasing the installed heat tracing capacity with respect to the minimum required to overcome thermal losses, leads to a reduction of the preheating time and, therefore, a reduction in the overall operational expenses of the system. In some situations, this was found to also lead to a reduction in the necessary insulation thickness. Simulations indicate that if the optimal insulation was used, a decrease of 10 and 15% in thermal losses and O&M expenditures, respectively, could be achieved.

Evaluation of the static electric field effects on freezing parameters of some food systems

In present study the effect of freezing in the absence and presence of static electric field (SEF) on selected freezing parameters of liquid and solid food including: distilled water, NaCl solutions, mushroom extract and mushroom were investigated. The static electric field was applied at the intensities of 0.0–9.6 × 105 V/m during freezing at -30 ± 1 °C. The freezing parameters of different samples were evaluated from the freezing curve of them. Results showed that among the different samples, the pure water had the highest freezing temperature, supercooling degree and shortest phase transition period in the absence of electric field. By applying the electric field, the nucleation temperature and phase transition period of the samples increased. The highest nucleation temperature was observed in the pure water under 6.4 × 105 V/m electric field. The nucleation temperature of the other samples showed an optimum value in the intensity of 3.2 × 105 V/m.

Preparation and Experimental Evaluation of Phase-Change Characteristics in Carbon-Based Suspensions.

In this study, micro/nanocarbon-based materials (MNCBMs) were prepared using the high-pressure combustion method (HPCM) with an isoperibol oxygen bomb calorimeter at different oxygen pressures (0.5–3.0 MPa). The prepared MNCBMs were added to water to form carbon-based suspensions (CBSs); sodium dodecyl benzene sulfonate (SDBS) and defoamer were added to the CBSs to enhance their stability. The thermal conductivity, viscosity, density, and contact angle of the CBSs were measured using appropriate instruments to determine their fundamental characteristics. The phase-change characteristics of the CBSs were measured and analyzed using a differential scanning calorimeter (DSC) to evaluate the feasibility of employing them as phase-change materials in ice-storage air-conditioning systems. The results revealed that the maximal change ratios of thermal conductivity, viscosity, density, and contact angle of the samples were −3.15%, 6.25%, 0.23%, and −57.03%, respectively, as compared with the water. The CBS of S5 (oxygen pressure of 2.0 MPa) had the lowest melting temperature and subcooling degree (SD) and the highest freezing temperature in the experiments conducted using the DSC; thus, S5 was determined to be the most suitable CBS for use as a phase-change material of cold energy storage in this study.

Investigation of activated carbon/ethanol for low temperature adsorption cooling

ABSTRACTCommercially available adsorption cooling systems use water/silica gel, water/zeolite and ammonia/ chloride salts working pairs. The water-based pairs are limited to work above 0°C due to the water high freezing temperature, while ammonia has the disadvantage of being toxic. Ethanol is a promising refrigerant due to its low freezing point (161 K), nontoxicity, zero ozone depletion, and low global warming potential. Activated carbon (AC) is a porous material with high degree of porosity (500–3000 m2/g) that has been used in wide range of applications. Using Dynamic Vapour Sorption (DVS) test facility, this work characterizes the ethanol adsorption of eleven commercially available activated carbon materials for cooling at low temperature of −15°C. DVS adsorption results show that Maxsorb has the best performance in terms of ethanol uptake and adsorption kinetics compared to the other tested materials. The Maxsorb/ethanol adsorption process has been numerically modeled using computational fluid dynamics (CFD) and simulation results are validated using the DVS experimental measurements. The validated CFD simulation of the adsorption process is used to predict the effects of adsorbent layer thickness and packing density on cycle uptake for evaporating temperature of −15°C. Simulation results show that as the thickness of the Maxsorb adsorbent layer increases, its uptake decreases. As for the packing density, the amount of ethanol adsorbed per plate increases with the packing density reaching maximum at 750 kg/m3. This work shows the potential of using Maxsorb/ethanol in producing low temperature cooling down to −15°C with specific cooling energy reaching 400 kJ/kg.

Surface-charge-induced orientation of interfacial water suppresses heterogeneous ice nucleation on <i>α</i>-alumina (0001)

Abstract. Surface charge is one of the surface properties of atmospheric aerosols, which has been linked to heterogeneous ice nucleation and hence cloud formation, microphysics, and optical properties. Despite the importance of surface charge for ice nucleation, many questions remain on the molecular-level mechanisms at work. Here, we combine droplet-freezing assay studies with vibrational sum frequency generation (SFG) spectroscopy to correlate interfacial water structure to surface nucleation strength. We study immersion freezing of aqueous solutions of various pHs on the atmospherically relevant aluminum oxide α-Al2O3 (0001) surface using an isolated droplet on the surface. The high-pH solutions freeze at temperatures higher than that of the low-pH solution, while the neutral pH has the highest freezing temperature. On the molecular level, the SFG spectrum of the interfacial water changes substantially upon freezing. At all pHs, crystallization leads to a reduction of intensity of the 3400 cm−1 water resonance, while the 3200 cm−1 intensity drops for low pH but increases for neutral and high pHs. We find that charge-induced surface templating suppresses nucleation, irrespective of the sign of the surface charge. Heterogeneous nucleation is most efficient for the nominally neutral surface.

Influence of lyophilization factors and gelatin concentration on pore structures of atelocollagen/gelatin sponge biomaterial.

This study aimed to investigate influences of lyophilization factors and gelatin concentration on pore structures of ACG sponge. ACG sponges of different freezing temperatures (-30, -80 and -196oC), freezing times (1, 2 and 24 h), gelatin concentrations (0.6%AC+0.15%G, 0.6%AC+0.6%G and 0.6%AC+2.4%G), and with 500 μM fluvastatin were fabricated. Pore structures including porosity and pore size were analyzed by scanning electron microscopy and ImageJ. The cytotoxic effects of ACG sponges were evaluated in vitro. Freezing temperature did not affect porosity while high freezing temperature (-30oC) increased pore size. The high gelatin concentration group (0.6%AC+2.4%G) had decreased porosity and pore size. Freezing time and 500 μM fluvastatin did not affect pore structures. The cytotoxicity and cell proliferation assays revealed that ACG sponges had no cytotoxic effects on human mesenchymal stromal cell growth and proliferation. These results indicate that ACG sponge may be a good biomaterial scaffold for bone regeneration.

Magnetic slippery extreme icephobic surfaces.

Anti-icing surfaces have a critical footprint on daily lives of humans ranging from transportation systems and infrastructure to energy systems, but creation of these surfaces for low temperatures remains elusive. Non-wetting surfaces and liquid-infused surfaces have inspired routes for the development of icephobic surfaces. However, high freezing temperature, high ice adhesion strength, and high cost have restricted their practical applications. Here we report new magnetic slippery surfaces outperforming state-of-the-art icephobic surfaces with a ice formation temperature of −34 °C, 2–3 orders of magnitude higher delay time in ice formation, extremely low ice adhesion strength (≈2 Pa) and stability in shear flows up to Reynolds number of 105. In these surfaces, we exploit the magnetic volumetric force to exclude the role of solid–liquid interface in ice formation. We show that these inexpensive surfaces are universal and can be applied to all types of solids (no required micro/nano structuring) with no compromise to their unprecedented properties.

Pressure retaining method based on phase change for coring of gas hydrate-bearing sediments in offshore drilling

Coring of gas hydrate-bearing sediment with situ-pressure retained is significant for both geophysics and geochemistry. However, the core recovery of current pressure corers is relatively low, which is attributed to the sensitivity of mechanical valves to solid particles and drilling cuttings. To improve the core recovery of the pressure corers, the pressure retaining method based on the phase change of situ drilling fluid has been used to seal the core tube mouth. The pressure retaining capacity of the ice valves made from seawater mixed with different mass concentrations of bentonite was tested; the influence of the ice valve length and freezing temperature on the pressure retaining capacity was also studied. Results show that the ice valve made from pure seawater could not retain pressure for the fissures caused by stress because of the temperature difference and the incompletely freezing of the ice valve caused by the concentrated inorganic salts in the core of the ice valve. The ice valve made from seawater mixed with 7% mass concentration of bentonite can sustain pressures of up to 47MPa. Both high ice valve length and low freezing temperature are beneficial for improving the pressure sustaining capacity of the ice valve. Results indicate that using the ice valve made from seawater mixed with bentonite to instead mechanical valves in the pressure corer can be a potential solution to improve the recovery of pressurized hydrate-bearing sediment core.

High freezing temperature in SnO2 based diluted magnetic semiconductor

Sn0.95−yMn0.025Co0.025FeyO2 (y=0.0, y=0.01) compounds have been synthesized by the precipitation exchange method. X-ray diffraction revealed that single-phase rutile polycrystalline structure was obtained. Magnetic measurements revealed that this sample exhibits spin glass behaviors for y=0 with a spin-freezing temperature around 150K, while it exhibits ferromagnetism for y=0.01 below Tc=300K. The existences of frustrated moments due to Ruderman–Kittle–Kasuya–Yosida interactions in Sn(Mn, Co)O2 may be responsible for the spin glass state formed in Sn(Mn,Co)O2. With a tri-doping by Fe this magnetic frustration is broken, indicating that the Fe atoms introduces charge carriers responsible for the change of interaction from frustrated behaviors to ferromagnetic interaction.

Generalisation of Levine's prediction for the distribution of freezing temperatures of droplets: a general singular model for ice nucleation

Abstract. Models without an explicit time dependence, called singular models, are widely used for fitting the distribution of temperatures at which water droplets freeze. In 1950 Levine developed the original singular model. His key assumption was that each droplet contained many nucleation sites, and that freezing occurred due to the nucleation site with the highest freezing temperature. The fact that freezing occurs due to the maximum value out of a large number of nucleation temperatures, means that we can apply the results of what is called extreme-value statistics. This is the statistics of the extreme, i.e. maximum or minimum, value of a large number of random variables. Here we use the results of extreme-value statistics to show that we can generalise Levine's model to produce the most general singular model possible. We show that when a singular model is a good approximation, the distribution of freezing temperatures should always be given by what is called the generalised extreme-value distribution. In addition, we also show that the distribution of freezing temperatures for droplets of one size, can be used to make predictions for the scaling of the median nucleation temperature with droplet size, and vice versa.

Thermal property characterization of a low melting-temperature ternary nitrate salt mixture for thermal energy storage systems

Molten salts have better thermal properties than synthetic mineral oil, and hence they can be directly used as heat transfer fluids in solar power plants, but in practice their direct applications as heat transfer fluids are constrained due to their high freezing temperature points. In this paper, a class of ternary nitrate salt mixtures consisting of 50–80 wt% KNO 3, 0–25 wt% LiNO 3 and 10–45 wt% Ca(NO 3) 2 were processed and tested. Experimental results indicated that some mixtures within this range exhibited excellent thermal properties, such as a low melting point (<100 °C), robust reliability, high-temperature stability (upto 500 °C) and a low viscosity (e.g.,<5 cP at 190 °C). Apart from these desirable thermo-physical properties, the manufacturing cost of these novel inorganic salts HTFs (Heat Transfer Fluids) is considerably lower than those of the existing commercial heat transfer fluids (HTFs).

Spin Correlations in MnCu Spin-Glass Alloy

To elucidate the causes of the strong suppression of the magnetic long-range order in Mn Cu spin-glass alloy, spin correlations were studied using neutron scattering for a Mn 73 Cu 27 single crystal. Magnetic diffuse scattering was observed around the (1,0,0), (1,1/2,0), and (1,1,0) reciprocal lattice points in the (0,0,1) scattering plane. The experimental data were compared with the wave-vector-dependent susceptibility calculated using the effective exchange coupling parameters up to the fourth neighbor. In addition to the spin frustration induced by the nearest-neighbor antiferromagnetic coupling in an fcc antiferromagnet, farther-neighbor exchange coupling parameters also satisfy the special conditions for the spin frustration, resulting in the strong suppression of the magnetic LRO of Mn Cu alloys with a relevant Mn concentration. In cooperation with the random distribution of Mn atoms, the spin-glass state with a high freezing temperature is considered to be realized.