Frost Formation Research Articles

Micro/Nano Hierarchical Dumbbell-like and Micropapillae Structure Improves Light Absorption and Facilitates Anti-icing/Deicing Performance.

The emergence of ice formation and accretion presents significant challenges, catalyzing an urgent need for clean and efficient anti-icing solutions. Solar energy, a powerful and sustainable resource, can be integrated with the micronano-structured superhydrophobic surface to enhance anti-icing and deicing performance through the solar photothermal effect, overcoming the limitations of a traditional superhydrophobic surface. Herein, inspired by bamboo and lotus leaves, a synergetic photothermal anti-icing superhydrophobic surface (PASS) has been developed. This was achieved through nanosecond laser ablation and chemical modification, resulting in a surface with remarkable superhydrophobic low adhesion (water contact angle >167°, rolling angle < 2°). The PASS notably extends the freezing time of water droplets to 1056 s and delays frost formation to 47 min at 60% humidity. Moreover, the surface retains its superhydrophobic properties after enduring several rigorous tests. Additionally, the photothermal conversion efficiency reaches up to 67.31%, and the temperature increases to 95.6 °C under 1.5 sun illumination for 600 s in ambient conditions (Tr = 7 °C). The ice melting time is only 120 s under 1 sun illumination at -15 °C. Consequently, the PASS sample stands as a preeminent strategy for anti-icing and deicing pursuits owing to its exceptional photothermal proficiency, superhydrophobicity, and enduring robustness.

Frost Characterization for the Altiplano, Valleys and Chaco Regions of Bolivia

The analysis focused on frost events in the Altiplano, Valles, and Chaco regions of Bolivia, with an emphasis on sub-zero temperatures and related atmospheric patterns to identify the predominant type of frost. A retrospective, observational, and longitudinal design was employed to analyze minimum temperatures from nine meteorological stations between 2005 and 2019. Radiative frosts in the Altiplano showed stability in minimum temperatures from April to October, with low variability and the absence of outliers, while variability was higher in the Valles and Chaco regions. Frost events were more frequent and severe from May to August, with the Altiplano being the most affected region. Satellite imagery and atmospheric reanalysis data from 2010 to 2019 were used for the visual interpretation of atmospheric patterns. A mixed-method approach—quantitative for the statistical analysis of minimum temperatures and qualitative for image interpretation—identified 24 advection frost events between 2010 and 2019, primarily in July and August, associated with high-pressure systems over the Atlantic and Pacific. The Chaco region was the most affected by advection frosts, followed by the Altiplano and the Valles. These findings underscore the importance of spatial and temporal variability in frost occurrence and the need for regional strategies to manage climate risk. It is concluded that altitude, along with factors such as solar radiation, thermal inversion, and wind, is key in frost formation, with radiative frosts being the most common, although advection frosts are also significant, especially under cold front conditions.

Innovative ice mitigation: Exploring the potential of choline-based deep eutectic solvents and ionic liquids synergies

The development of anti-icing coatings for extremely low temperatures is still emerging. Deep eutectic solvents (DESs), as subset of ionic liquid (IL) analogues, have recently gained increasing attention for their unique and versatile applications. Given no investigation regarding anti-icing capabilities of DESs, our study focused on the exciting potential of choline-based DESs. The intriguing potential of hydrogen bonding through the synergistic combination of DESs and ILs offers significant promise for innovative solutions to ice-related challenges that remain largely unexplored. We conducted a comprehensive study on the anti-freezing properties of DESs by synthesizing choline-based ILs featuring both hydrophilic and hydrophobic anions. We aimed to explore how the diverse hydrogen-bond donors in DESs combined with the synthesized ILs to enhance the system’s ability to prevent ice formation. Substituting ethylene glycol (EG) with glycerol (GL) resulted in achieving an ice formation temperature of − 36 °C and an exceptionally low ice adhesion strength of 10 kPa, due to a thicker quasi-liquid layer on the coating surface, confirmed by solid-state NMR spectroscopy. The altered frost formation patterns of the DES-containing coatings demonstrated an enhance resistance against frost formation. This comprehensive study underscored the promising synergy between DESs and ILs for highly effective ice mitigation.

Frost growth on silver iodide (AgI) stripe patterned surface under condensation frosting condition

This study investigates frost accumulation on surfaces with silver iodide (AgI) patterns to control initial formation of liquid droplets and subsequent frost growth under condensation frosting condition. AgI is known as one of the most effective nucleation agents, and a novel UV-lithography technique is adopted to fabricate scalable AgI patterns on a silicon substrate. Image processing with the help of machine learning provided quantitative information of frost evolution dynamics. Frost preferentially initiated from the AgI striped patterns, and showed horizontal crystal growth. Eventually, frost-free zones appeared in between the stripes. In addition to experimental observation, mass balance analysis identified the influential factors and parameters that influence the formation of a complete frost-free zone. Present approach using AgI patterns offers a promising approach to control initial frost formation under condensation frosting condition, which may contribute to mitigate negative effects of frost in diverse applications.

Efficient anti-frosting enabled by femtosecond laser-induced salt-philic and superhydrophobic surface

Frost formation is a normal phase transition phenomenon in cold climates, while it usually brings certain troubles to human lives and production. Therefore, it is of great significance to develop frost resistant materials and key technologies. Here, a salt-philic and superhydrophobic surface is designed on a PDMS substrate by femtosecond laser direct writing technology in combination with salt–ethanol–water mixtures droplet treatment. The laser-treated PDMS embedded salt (LTP-S) surface exhibits superhydrophobicity, which alone is a property that can resist the formation of frost and enables a self-cleaning effect. Meanwhile, the salt coating further enhances the frost resistance of the surface by reducing the freezing point temperature. The LTP-S surface is revealed to perform well in frosting-defrosting cycles, washing resistance, chemical corrosion resistance, heating resistance, and long-term air exposure tests as a highly efficient and stable anti-frosting surface. This work demonstrates a facile strategy to fabricate a salt-philic and superhydrophobic surface for efficient anti-frosting.

Frost crystal growth behavior on a hydrophilic surface over a wide range of cold surface temperature

The initial frosting phenomenon is a discontinuous phase nucleation process, the cold surface temperature and properties have a decisive influence on this phenomenon, especially in the initial frosting stage. With the development of aerospace and energy transportation technology, frost formation at low temperatures (-100 °C∼-30 °C) and ultra-low temperatures (-273 °C∼-100 °C) has gradually attracted the attention of researchers. In this paper, the initial frosting phenomena on hydrophilic surfaces with a contact angle of 10° (CA= 10°) and ordinary (CA= 95°) surfaces are studied experimentally in a wide range of cold surface temperatures (-190 °C∼-30 °C). Four modes are confirmed: cold surface condensation frosting, cold surface sublimation frosting, air boundary layer condensation frosting and air boundary layer sublimation frosting. It is also found that the four frosting modes do not appear in turn with the decrease of the cold surface temperature, but two or more frosting modes appear at the same time. And the surface contact angle has an important influence on the frosting mode. The initial frost crystal morphology mainly depends on the cold surface temperature and the corresponding frosting mode. Four different forms of frost crystals are observed: hexagonal prism (feather), branch (pine needle), cluster (shrub) and floc (grape), in which the cluster frost crystal is more sensitive to the surface contact angle and can appear in different temperature ranges due to different contact angles. Based on the statistics of the size, quantity, and distribution of the initial frost crystals, it is found that -70 °C is a major turning point for frost formation from the cold surface sublimation frosting to the air boundary layer sublimation frosting, and an important change has taken place near this point. Furthermore, it affects the shape and size distribution of frost crystals. These findings are of great significance for the study and understanding of frost crystal growth mechanism in the initial stage of frost formation at low and ultra-low temperatures.

Liquid-infused surface on optimized anodic porous aluminum for anti-frost and anti-ice application

Here, we present liquid-infused surfaces (LISs) fabricated on an aluminum substrate using the anodizing method to introduce specific nanofeatures infiltrated by silicone oil to reduce the friction between ice and surface. To achieve various nanostructures on the aluminum substrate, the anodizing conditions are varied. The ice adhesion stress could be significantly plummeted to 21.7 kPa on an LIS with optimized dimensions for nanofeatures. Frost formation tests in environments with a relative humidity of 75 % on the fabricated surfaces with a temperature of −17 ℃ reveal that the fabricated samples can considerably extend the frost formation time. The frosting time for the fabricated sample can reach 47 min, whereas the bare aluminum is completely covered by frost only after 1.5 min

Edge-affected droplet dynamic and subsequent frost growth characteristics for horizontal cold plate under different humidity levels

Frosting widely exists in engineering applications and mostly has negative impacts. To better avoid or utilize frosting, more micro and systematic investigations into the frosting mechanisms are necessary. In this study, the combined effect of humidity and plate edge on droplet dynamic and the subsequent frost growth characteristics of a horizontal cold plate is experimentally investigated. The results show that the difference in the durations of droplet condensation stage between edge-affected and unaffected regions is little, and both decrease from around 480 to 43 s when relative humidity (RH) increases from 30% to 80%. In contrast, the difference in the durations of droplet freezing stage between edge-affected and unaffected regions is significant. The former is around 9 s at all humidity levels, while the latter decreases from around 100 s to 40 s when RH increases from 30% to 80%. Meanwhile, the average equivalent droplet diameters in the edge-affected region are 87.3 × 10−3–122.1 × 10−3 mm, which are 31.0 × 10−3–45.5 × 10−3 mm larger than in the unaffected region. The frost layer surface roughness at 80% RH is smaller than others due to the frost crystal reverse melting. This paper can help better understand the frosting mechanism from a microscopic scale and guide the accurate prediction of frost formation.

Robust All-Day Frostphobic Surfaces.

The application of solar-thermal surfaces for antifrosting and defrosting has emerged as a passive and environmentally friendly approach to mitigate the negative consequences of frost formation, such as structural damage and reduced heat transfer efficiency. However, achieving robust all-day frostphobicity solely through interfacial modification and solar-thermal effects is challenging in practical applications: The thick frost that accumulates at night strongly scatters solar radiation, rendering the solar-thermal coatings ineffective during the daytime. Additionally, these nanostructured coatings are susceptible to wear and tear when exposed to the outdoors for extended periods of time. To address these challenges, we present an innovative frostphobic surface that incorporates V-grooved structures with superhydrophobic solar-thermal layers (VSSs). The out-of-plane gradient structures facilitate spatially regulated vapor diffusion, an enhanced photothermal effect, and robust water repellency. These features not only prevent frost from covering the entire surface overnight, enabling effective solar-thermal defrosting during the daytime, but also protect the surface from deterioration. The combined merits ensure robust all-day frostphobicity and exceptional durability, making the VSS surface promising for practical applications and extending the lifespan in extreme environments.

Biphilic Functional Surfaces for Frost Prevention and Efficient Active Defrosting

AbstractThe present work addresses the systematic accurate fabrication and design of biphilic surfaces having superhydrophobic circular islands surrounded by a hydrophilic background by investigating their condensation frosting and defrosting behavior. A significant delay in frost formation is observed on samples with higher superhydrophobicity ratio A*, defined as superhydrophobic area to total area ratio. As the superhydrophobic island diameter D increases from D = 500 µm to D = 700 µm (A* from 19.62% to 38.46%), a 50% improvement/delay is observed in terms of frost formation or densification. Besides delaying icing/frosting, the presence of superhydrophobic areas empowers the formation of porous and nonuniform frost structure, which facilitates ice removal during the defrosting process. To this end, as the surface is recovered the ambient temperature, almost complete passive cleaning performance within only 23 s is observed on the biphilic design having superhydrophobic islands with the diameter of D = 500 µm, that is, a superhydrophobicity ratio A* of 19.62%. This work concludes on the optimum biphilic ratio, which is not only effective as a passive method by hindering frosting but also leads to a slush/water free surface after defrosting eased by the Laplace pressure gradient which is imposed by the different biphilic wettability patterns.

Experimental study on the characteristics of frost formation and defrosting water retention between vertical double surfaces with different wettability

Frost formation and defrosting water retention directly affect the heat transfer process of outdoor finned tube heat exchanger, which in turn influences the energy efficiency of air source heat pumps for building heating. Three typical wettability surfaces were prepared, including a bare copper hydrophilic surface (BCS), a hydrophobic copper surface (HCS) and a superhydrophobic copper surface (SHCS). The above three surfaces are combined in pairs to construct three different wettability combinations, which are Combination 1: HCS-BCS, Combination 2: BCS-SHCS and Combination 3: HCS-SHCS, respectively. Frosting-defrosting experiments between vertical double surfaces are carried out on the above combinations. The results illustrated that the combinations with SHCS exhibit excellent frost inhibition properties. Compared with Combination 1, the channel filling rate of Combination 2 and Combination 3 were reduced by 16.79 % and 30.09 % respectively at a frosting time of 60 min. The defrosting time of the combination is determined by the slower defrosting of the two surfaces. Compared with Combination 2, the defrosting rate of Combination 3 is improved by up to about 12.93 %. Avoiding the formation of large-sized liquid films and droplets or utilizing the “absorption” phenomenon caused by wettability differences between surfaces are important measures to reduce the possibility of bridge formation during the defrosting process. And the greater the wettability difference, the more obvious the “absorption” phenomenon became. Spherical droplets on the SHCS can be completely absorbed by the liquid film on BCS under the action of differential surface tension. Neither Combination 2 nor Combination 3 formed a liquid bridge at a surface spacing of 2 mm. The research will provide theoretical support for the selection of fin spacing and fin coating type under different working conditions in practical engineering.

Fabrication of SiO2/PDMS/EP superhydrophobic coating for anti-icing

In low-temperature environments, the condensation and icing phenomena of water molecules on material surfaces may adversely affect the functionality and durability of various products, so it is critical to improve the anti-icing properties of material surfaces. In this study, the anti-icing mechanism of superhydrophobic coatings was analyzed based on the surface wettability theory, and SiO2/PDMS/EP superhydrophobic coating was fabricated by the spraying method. The surface wettability, surface micro-morphology, and surface chemical composition of the coating was characterized, and the stability of the coating as well as the anti-icing properties were investigated. The results show that the SiO2/PDMS/EP superhydrophobic coating sprayed on the Al-based surface has a contact angle of 163.3° and a sliding angle of 4°, and the coating maintains excellent superhydrophobicity at a low temperature of -15°. This coating can significantly delay the freezing time and temperature of droplets on its surface, reduce the shear force and natural deicing time required to remove surface ice, and exhibit excellent anti-icing performance. The excellent anti-icing durability of the coating was demonstrated by the icing-deicing cycle experiment. Subsequently, the anti-frosting performance was further investigated, and the results showed that it effectively slowed down the speed of frost formation. Therefore, the superhydrophobic coating fabricated in this study is suitable for a wide range of working conditions and has potential practicality. It also provides experimental guidance for the application of anti-icing coatings on Al surfaces.

EXPERIMENTAL ANALYSIS OF THE INFLUENCE OF FAN SPEED ON FROST GENERATION AND ITS IMPACT ON A HEAT PUMP

The phenomenon of frost on the heat exchanger surfaces penalizes the performance of the heat pump, one of the operating parameters that influences the evaporation temperature, this is transferred to the formation of frost, and its impact is the amount of air passing through the evaporator, in that sense, an air-water heat pump has been experimented at different fan speeds and environmental conditions inside a climatic chamber. The results allow to obtain different parameters to characterize the frost formation process and to make an effective comparison between them. The lower the fan speed, the lower the air flow rate, the lower the heating time, and the higher the number of defrost cycles required for the same environmental conditions. In this way, some correlations could be developed to predict how the frosting process is affected by the fan speed in more conditions that are not tested. The aim is to determine to what level frost formation can be suppressed by achieving different fan speeds whether it is technically and economically feasible and what implications imposes on the heat pump performance.

Developing a durable anti-frost surface: Integrating the passive anti-icing properties of salt, saline, and bulk ice for enhanced frost prevention

Icing on surfaces presents significant challenges for the aviation industry and life in cold alpine regions. Developing smart surfaces to mitigate icing effects is highly desirable. When icing cannot be completely avoided in the atmosphere, limiting it to a small area on the surface is a practical solution. We have created a hydrophilic pattern on superhydrophobic surfaces using laser fabrication, which allows saline droplets to adhere to the pattern. As these droplets dry, salt grains cover the pattern, making the surface primarily superhydrophobic. Under frost conditions, the salt grains turn into saline beads, which then freeze into ice beads. Frost forms only on the tops of these ice beads within the pattern. Due to the lower saturated vapor pressure of salt, saline, and ice compared to the supersaturated vapor pressure for condensation, there is not enough humidity around the pattern for water vapor to condense and form frost. As a result, water vapor continuously deposits inside the pattern, significantly reducing frost formation around it. This combination of salt, saline, and ice, with their lower saturation vapor pressures below zero Celsius, ensures a dry perimeter during rapid temperature drops and increased humidity. By designing the pattern size appropriately, the dry perimeters overlap, keeping the entire surface outside the pattern free of frost. This approach offers a promising solution for reducing frosting on surfaces.

Micro- and Nanoengineered Metal Additively Manufactured Surfaces for Enhanced Anti-Frosting Applications.

The greater geometrical design freedom offered by additive manufacturing (AM) as compared to the conventional manufacturing method has attracted increasing interest in AM to develop innovative and complex designs for enhanced performance. However, the difference in material composition and surface properties from conventional alloys has made surface micro-/nanostructuring of AM metals challenging. Frost accretion is a safety hazard in numerous engineering applications. To expand the application of AM, this study experimentally investigates the antifrosting performance of superhydrophobic and slippery lubricant-infused porous surfaces (SLIPSs) generated on AM alloy, AlSi10Mg. By strategically utilizing the subgrain structure in the metallography of the AM alloy, the functionalized superhydrophobic AM surface featuring hierarchical structures was shown to greatly reduce frost formation as compared to functionalized single-tier structured surfaces, hierarchical structures formed on conventional aluminum alloy surfaces, and SLIPSs. Optical observation of frost propagation demonstrated that the mechanism of frost delay is governed by the inhibition of spontaneous droplet freezing through exceptional Cassie state stability during condensation frosting. The Cassie stability results from the unique AM structure morphology, which creates a higher structural energy barrier to prevent condensate from infiltrating the cavities. This phenomenon also enables the formation of a high surface-to-droplet thermal resistance, which eliminates spontaneous droplet freezing down to a -15 °C surface temperature. Our work demonstrates a scalable structuring method for AM metals, which can result in delayed frost formation, and it also provides guidelines for the development of engineered surfaces requiring the antifrosting function for several industries.

Anti-Ice PMMA Surface Design and Processing

At low temperatures, PMMA surfaces are prone to ice and frost formation, which presents a significant challenge for PMMA’s efficient application in cold environments due to the difficulty in physically removing the accumulated ice. Superhydrophobic surfaces exhibit promising potential in passive anti-icing strategies. To exploit this advantage, we employed femtosecond laser technology to create six distinct microstructured PMMA surfaces, followed by surface modification using 1H,1H,2H,2H-perfluorodecyltriethoxysilane, resulting in enhanced hydrophobic and anti-icing properties. Among the tested structures, a secondary circular dot pattern achieved a remarkable contact angle of 153.7°, prolonging the freezing duration by approximately 40% at −10 °C, and reducing frost accumulation by over 50%. The ice adhesion strength was significantly reduced to 34 kPa. These findings contribute to broadening the applicability of PMMA and advancing the use of superhydrophobic surfaces in anti-icing applications.

Evidence for transient morning water frost deposits on the Tharsis volcanoes of Mars

The present-day water cycle on Mars has implications for habitability and future human exploration. Water ice clouds and water vapour have been detected above the Tharsis volcanic province, suggesting the active exchange of water between regolith and atmosphere. Here we report observational evidence for extensive transient morning frost deposits on the calderas of the Tharsis volcanoes (Olympus, Arsia and Ascraeus Montes, and Ceraunius Tholus) using high-resolution colour images from the Colour and Stereo Surface Imaging System on board the European Space Agency’s Trace Gas Orbiter. The transient bluish deposits appear on the caldera floor and rim in the morning during the colder Martian seasons but are not present by afternoon. The presence of water frost is supported by spectral observations, as well as independent imagery from the European Space Agency’s Mars Express orbiter. Climate model simulations further suggest that early-morning surface temperatures at the high altitudes of the volcano calderas are sufficiently low to support the daily condensation of water—but not CO2—frost. Given the unlikely seasonal nature of volcanic outgassing, we suggest the observed frost is atmospheric in origin, implying the role of microclimate in local frost formation and a contribution to the broader Mars water cycle.

Frost Formation over an Inclined Plate Under Natural Convection with Lattice–Boltzmann Method

The frost formation is highly complex as it involves both transient heat and mass transfer. It has significant effects on various industries such as aviation and refrigeration. In recent years, numerous researchers have focused on the periods of frost growth using physical, mathematical, and experimental methods for various geometries. But, despite inclined surfaces under natural convection being widely used in the industries, there has been limited research on frost growth on these surfaces. Therefore, the purpose of this study is to investigate the characteristics of frost growth on inclined surfaces. For these aims the Lattice–Boltzmann method (LBM) is used. The findings indicate that an increase in the inclination angle of the cold surface leads to a decrease in frost thickness. Also, it is evident that increasing the temperature difference between the ambient and cold surface causes a reduction in the differences in frost thickness across various inclination angles. Also, under same ambient and cold surface temperatures, a higher humidity yields a greater driving force for mass transfer. Consequently, this leads to a reduction in differences in frost thickness at different surface angles. Finally, results indicate that the relative error between experimental and numerical results ranges from 5 to 27%.

Condensation or Desublimation: Nanolevel Structural Look on Two Frost Formation Pathways on Surfaces with Different Wettabilities.

Processes of water condensation and desublimation on solid surfaces are ubiquitous in nature and essential for various industrial applications, which are crucial for their performance. Despite their significance, these processes are not well understood due to the lack of methods that can provide insight at the nanolevel into the very first stages of phase transitions. Taking advantage of synchrotron grazing-incidence wide-angle X-ray scattering (GIWAXS) and environmental scanning electron microscopy (ESEM), two pathways of the frosting process from supersaturated vapors were studied in real time for substrates with different wettabilities ranging from highly hydrophilic to superhydrophobic. Within GIWAXS, a fully quantitative structural and orientational characterization of the undergoing phase transition reveals the information on degree of crystallinity of the new phase and determines the ordering at the surfaces and inside the films at the initial stages of water/ice nucleation from vapor onto the substrates. The diversity of frosting scenarios, including direct desublimation from the vapor and two-stage condensation-freezing processes, was observed by both GIWAXS and ESEM for different combinations of substrate wettability and vapor supersaturations. The classical nucleation theory straightforwardly predicts the pathway of the phase transition for hydrophobic and superhydrophobic substrates. The case of hydrophilic substrates is more intricate because the barriers in Gibbs free energy for nucleating both liquid and solid embryos are close to each other and comparable to thermal energy kBT. At that end, classical nucleation theory allows concluding a relation between contact angles for ice and water embryos on the basis of the observed frosting pathway.

Delaying frost formation by controlling surface chemistry of ZnO-coated 304 stainless steel surfaces

Because 304 stainless steel is extensively used in everyday life, surface icing frost would cause annoyance; thus, the research on 304 stainless steel with frost inhibition is quite important. The superhydrophobic surface anti-frost is energy-saving and ecologically beneficial, but it also avoids typical defrosting, which reduces energy consumption, pollution, and other difficulties. As a result, the investigation of superhydrophobic surface frost inhibition performance offers promising practical potential. However, traditional manufacturing procedures for superhydrophobic surfaces have proven to be difficult and expensive, rendering them unsuitable for mass production. In this paper, a simple hydrothermal and sol-gel method were used to prepare the superhydrophobic surface wettability of 304 stainless steel and determine the frosting behavior of superhydrophobic ZnO, hydrophobic ZnO, hydrophilic ZnO, and 304 stainless steel sheets at low ambient temperatures. The frost resistance of superhydrophobic ZnO was studied. As a result, this study provides a novel idea for rationally designing frost-resistant superhydrophobic surfaces at low ambient temperatures.