Vapor Pressure Of Ice Research Articles

Analysis of Freeze-Thaw Behavior of Double (W1/O/W2) Emulsions by Differential Scanning Calorimetry: Effects of Inner Salt Concentration and Solid Fat Content

This work is focused on the study of freeze-thaw behavior of double (W1/O/W2) emulsions by the application of a cooling-heating-cooling cycle by differential scanning calorimetry. Emulsions were prepared with sodium caseinate as hydrophilic emulsifier in outer aqueous (W2) phase and sunflower oil (SO) and/or interesterified vegetable fat (VF) plus polyglycerol polyricinoleate as lipophilic emulsifier in lipid phase. The effects of sodium chloride concentration in inner aqueous (W1) phase and solid fat content in lipid phase were analyzed. In all cases, W1 phase froze at lower temperature than W2 phase because higher undercooling was required for the crystallization of inner water droplets. In the absence of VF, the system with low salt concentration showed water diffusion from undercooled W1 phase to frozen W2 phase at the first cooling stage, due to the lower vapor pressure of ice. However, at the second cooling stage, this phenomenon was not observed and partial recovery of inner water was detected, probably because of an osmotic effect. The increase of salt concentration allowed a higher retention of inner water after freezing of W2 phase, attributed to the lowered vapor pressure of W1 phase. The loss of inner water was also restrained or prevented by the presence of VF in lipid phase due to the immobilization of water droplets within a fat crystal network. The crystallization behavior of SO was related to inner water quantity and VF content. This study could be useful for the formulation of W1/O/W2 emulsions with enhanced freeze-thaw stability.

Inhibiting Condensation Freezing on Patterned Polyelectrolyte Coatings.

Condensation freezing inhibition is of great practical importance for anti-icing applications; however, no coatings with this performance have been reported. Here, we report the inhibition of condensation freezing on patterned polyelectrolyte coatings, including polyelectrolyte brush (PB), polyelectrolyte multilayer (PEM), and polyelectrolyte hydrogel (PH) surfaces, benefiting from their feature in regulating ice nucleation and propagation via changing counterions. On the reported surfaces, ice nucleation can be initiated exclusively at the domains with the polyelectrolytes; moreover, spontaneous ice propagation can be achieved atop the patterned polyelectrolyte surface. Consequently, condensed water surrounding the frozen drops on the patterned polyelectrolyte surface evaporates due to the instantaneously released latent heat in the course of ice propagation. Afterward, ice grows specifically on polyelectrolyte surfaces via desublimation as the saturated vapor pressure of ice is smaller than that of condensed water drops. As such, an ice-free region up to 96% of the entire surface area can be accomplished. We demonstrate that various polyelectrolyte coatings can be easily introduced on almost all surfaces, revealing great promise for anti-icing applications.

Frost-free zone on macrotextured surfaces

Numerous studies have focused on designing functional surfaces that delay frost formation or reduce ice adhesion. However, solutions to the scientific challenges of developing antiicing surfaces remain elusive because of degradation such as mechanical wearing. Inspired by the discontinuous frost pattern on natural leaves, here we report findings on the condensation frosting process on surfaces with serrated structures on the millimeter scale, which is distinct from that on a conventional planar surface with microscale/nanoscale textures. Dropwise condensation, during the first stage of frosting, is enhanced on the peaks and suppressed in the valleys, causing frost to initiate from the peaks, regardless of surface chemistry. The condensed droplets in the valley are then evaporated due to the lower vapor pressure of ice compared with water, resulting in a frost-free zone in the valley, which resists frost propagation even on superhydrophilic surfaces. The dependence of the frost-free areal fraction on the geometric parameters and the ambient conditions is elucidated by both numerical simulations based on steady-state diffusion and an analytical method with an understanding of boundary conditions independent of surface chemistry. We envision that this study would provide a unified framework to design surfaces that can spatially control frost formation, crystal growth, diffusion-controlled growth of biominerals, and material deposition over a broad range of applications.

Conceptual design of a low-pressure micro-resistojet based on a sublimating solid propellant

Abstract In the current and future trend towards smaller satellite missions, the development of a simple and reliable propulsion system with performance and characteristics in line with the typical requirements of nano-satellites and CubeSats plays a crucial role for enhancing the capabilities of this type of missions. This paper describes the design of a micro-resistojet using water stored in the frozen state (ice) as propellant, operating under sublimation conditions at low pressure. The low operating pressure allows for using the vapor pressure of ice as the only method of propellant feeding, thereby allowing for extremely low thrust and electric power usage. The results of an extensive set of numerical simulations for optimizing the thruster geometry in terms of power ratio and specific impulse produced are discussed. In addition, the design of the complete propulsion system is described. It makes use of a limited number of moving parts and two power sources, one in the thruster to increase the propellant temperature and one in the tank to maintain the propellant storage conditions. Results show that the proposed design represents an alternative option capable of meeting the typical requirements of small satellite missions by means of an intrinsically green propellant such as water, with the pressure inside the system never exceeding 600 Pa. Optimization results showed an optimum thrust to power ratio in range 0.2–1.2 mN/W for an expansion slot aspect ratio of 2.5.

High‐accuracy measurements of the vapor pressure of ice referenced to the triple point

AbstractThe vapor pressure of hexagonal (Ih) water ice was measured over the temperature range 175 K to 253.4 K and referenced to the value at the triple point of water. This experiment combined a highly accurate humidity generation system containing an ice‐coated saturator (millikelvin‐level temperature control) to provide humidified streams of nitrogen to a cavity‐enhanced laser absorption spectrometer. The measured ice vapor pressures had relative standard uncertainties ranging from 0.4% to 0.7% over the entire temperature range. We demonstrate that these measurements validate thermodynamic correlations for ice vapor pressure based on integration of the Clapeyron equation. Moreover, they also indicate that some commonly used vapor pressure correlations are inaccurate and should be avoided.

Spectroscopic measurement of the vapour pressure of ice

We present a laser absorption technique to measure the saturation vapour pressure of hexagonal ice. This method is referenced to the triple-point state of water and uses frequency-stabilized cavity ring-down spectroscopy to probe four rotation-vibration transitions of at wavenumbers near 7180 cm(-1). Laser measurements are made at the output of a temperature-regulated standard humidity generator, which contains ice. The dynamic range of the technique is extended by measuring the relative intensities of three weak/strong transition pairs at fixed ice temperature and humidity concentration. Our results agree with a widely used thermodynamically derived ice vapour pressure correlation over the temperature range 0°C to -70°C to within 0.35 per cent.

TEOS-10: A New International Oceanographic Standard for Seawater, Ice, Fluid Water, and Humid Air

Very accurate empirical thermodynamic potential functions are available for fluid water, ice, seawater, and humid air covering wide ranges of temperature and pressure conditions, including those of the terrestrial hydrosphere and atmosphere. These potential functions are formulated as international standards endorsed by the International Association for the Properties of Water and Steam (IAPWS). A related seawater standard referred to as the International Thermodynamic Equation of Seawater 2010 (TEOS-10) was adopted in 2009 by UNESCO for oceanography. Here, the formulations available from TEOS-10 for the description of the vapor pressure of ice and for thermodynamic properties of humid air, in particular, the relative humidity, are reviewed. It is concluded that the IAPWS formulation for the sublimation pressure is superior in uncertainty and range of validity over other available correlation equations, and that relative fugacity is a physically reasonable generalization of relative humidity for the case of non-ideal gases or equilibria with moist substances.

Electro-osmosis and Water Uptake in Polymer Electrolytes in Equilibrium with Water Vapor at Low Temperatures

Water uptake and electro-osmosis are investigated to improve the understanding and aid the modeling of water transport in proton-exchange membrane fuel cells (PEMFCs) below . Measurements of water sorption isotherms show a significant reduction in the water capacity of polymer electrolytes below . This reduced water content is attributed to the lower vapor pressure of ice compared to supercooled liquid water. At , 1100 equivalent weight Nafion in equilibrium with vapor over ice has of water per sulfonic acid group. Measurements of the electro-osmotic drag coefficient for Nafion and both random and multiblock copolymer sulfonated poly(arylene ether sulfone) (BPSH) chemistries are reported for vapor equilibrated samples below . The electro-osmotic drag coefficient of BPSH chemistries is found to be , and that of Nafion is . No significant temperature effect on the drag coefficient is found. The implication of an electro-osmotic drag coefficient less than unity is discussed in terms of proton conduction mechanisms. Simulations of the ohmically limited current below show that a reduced water uptake below results in a significant decrease in PEMFC performance.

Electro-osmosis and Water Uptake in Polymer Electrolytes in Equilibrium with Water Vapor at Low Temperatures

Measurements of the electro-osmotic drag coefficient for Nafion® and both random and multi-block co-polymer sulfonated poly(arylene ether sulfone) (BPSH) chemistries are reported for vapor equilibrated samples below 0 {degree sign}C. No significant change in the drag coefficient behavior for Nafion from that reported above 0 {degree sign}C is found. However BPSH is found to have a drag coefficient of 0.4. The implication of a drag coefficient less than unity in the interpretation of conduction mechanisms is discussed. Measurements of water sorption isotherms below 0 {degree sign}C are also presented. A significant reduction in the capacity of polymer electrolytes to store water below 0 {degree sign}C is found. This reduced water content is a result of the lower vapor pressure of ice compared to supercooled liquid.

Desiccation tolerance and drought acclimation in the Antarctic collembolan Cryptopygus antarcticus

The availability of water is recognized as the most important determinant of the distribution and activity of terrestrial organisms within the maritime Antarctic. Within this environment, arthropods may be challenged by drought stress during both the austral summer, due to increased temperature, wind, insolation, and extended periods of reduced precipitation, and the winter, as a result of vapor pressure gradients between the surrounding icy environment and the body fluids. The purpose of the present study was to assess the desiccation tolerance of the Antarctic springtail, Cryptopygus antarcticus, under ecologically-relevant conditions characteristic of both summer and winter along the Antarctic Peninsula. In addition, this study examined the physiological changes and effects of mild drought acclimation on the subsequent desiccation tolerance of C. antarcticus. The collembolans possessed little resistance to water loss under dry air, as the rate of water loss was >20% h −1 at 0% relative humidity (RH) and 4 °C. Even under ecologically-relevant desiccating conditions, the springtails lost water at all relative humidities below saturation (100% RH). However, slow dehydration at high RH dramatically increased the desiccation tolerance of C. antarcticus, as the springtails tolerated a greater loss of body water. Relative to animals maintained at 100% RH, a mild drought acclimation at 98.2% RH significantly increased subsequent desiccation tolerance. Drought acclimation was accompanied by the synthesis and accumulation of several sugars and polyols that could function to stabilize membranes and proteins during dehydration. Drought acclimation may permit C. antarcticus to maintain activity and thereby allow sufficient time to utilize behavioral strategies to reduce water loss during periods of reduced moisture availability. The springtails were also susceptible to desiccation at subzero temperatures in equilibrium with the vapor pressure of ice; they lost ∼40% of their total body water over 28 d when cooled to −3.0 °C. The concentration of solutes in the remaining body fluids as a result of dehydration, together with the synthesis of several osmolytes, dramatically increased the body fluid osmotic pressure. This increase corresponded to a depression of the melting point to approximately −2.2 °C, and may therefore allow C. antarcticus to survive much of the Antarctic winter in a cryoprotectively dehydrated state.

Cryoprotective dehydration and the resistance to inoculative freezing in the Antarctic midge, Belgica antarctica

During winter, larvae of the Antarctic midge, Belgica antarctica (Diptera, Chironomidae), must endure 7-8 months of continuous subzero temperatures, encasement in a matrix of soil and ice, and severely desiccating conditions. This environment, along with the fact that larvae possess a high rate of water loss and are extremely tolerant of desiccation, may promote the use of cryoprotective dehydration as a strategy for winter survival. This study investigates the capacity of larvae to resist inoculative freezing and undergo cryoprotective dehydration at subzero temperatures. Slow cooling to -3 degrees C in an environment at equilibrium with the vapor pressure of ice reduced larval water content by approximately 40% and depressed the body fluid melting point more than threefold to -2.6 degrees C. This melting point depression was the result of the concentration of existing solutes (i.e. loss of body water) and the de novo synthesis of osmolytes. By day 14 of the subzero exposure, larval survival was still >95%, suggesting larvae have the capacity to undergo cryoprotective dehydration. However, under natural conditions the use of cryoprotective dehydration may be constrained by inoculative freezing as result of the insect's intimate contact with environmental ice. During slow cooling within a substrate of frozen soil, the ability of larvae to resist inoculative freezing and undergo cryoprotective dehydration was dependent upon the moisture content of the soil. As detected by a reduction of larval water content, the percentage of larvae that resisted inoculative freezing increased with decreasing soil moisture. These results suggest that larvae of the Antarctic midge have the capacity to resist inoculative freezing at relatively low soil moisture contents and likely undergo cryoprotective dehydration when exposed to subzero temperatures during the polar winter.

Review of the vapour pressures of ice and supercooled water for atmospheric applications

The vapour pressures of ice and supercooled water are reviewed with an emphasis on atmospheric applications. Parametrizations are given for the vapour pressure, molar heat capacity, and latent heat of vaporization of both ice and liquid water. For ice, the experimental vapour pressure data are in agreement with a derivation from the Clapeyron equation. Below 200 K cubic ice may affect the vapour pressure of ice both in the atmosphere and in the laboratory. All of the commonly used parametrizations for the vapour pressure of supercooled water are extrapolations that were not originally intended for use below the freezing point. In addition, the World Meteorological Organization definition of the vapour pressure of supercooled water contains an easily overlooked typographical error. Recent data on the molar heat capacity of supercooled water are used to derive its vapour pressure. Nevertheless, the uncertainty is such that measurements of the deliquescence and freezing behaviour of aerosol particles are beginning to be limited by uncertainties in the thermodynamics of supercooled water. Copyright © 2005 Royal Meteorological Society

Freeze or dehydrate: only two options for the survival of subzero temperatures in the arctic enchytraeid Fridericia ratzeli.

Hygrophilic soil animals, like enchytraeids, overwintering in frozen soil are unlikely to base their cold tolerance on supercooling of body fluids. It seems more likely that they will either freeze due to inoculative freezing, or dehydrate and adjust their body fluid melting point to ambient temperature as has been shown for earthworm cocoons and Collembola. In the present study we tested this hypothesis by exposing field-collected adult Fridericia ratzeli from Disko, West Greenland, to freezing temperatures under various moisture regimes. When cooled at -1 degrees C min(-1) under dry conditions F. ratzeli had a mean temperature of crystallisation ( T(c)) of -5.8 degrees C. However, when exposed to temperatures above standard T(c) for 22 h, at -4 degrees C, most individuals (90%, n= 30) remained unfrozen. Slow cooling from -1 degrees C to -6 degrees C in vials where the air was in equilibrium with the vapour pressure of ice resulted in freezing in about 65% of the individuals. These individuals maintained a normal body water content of 2.7-3.0 mg mg(-1) dry weight and had body fluid melting points of about -0.5 degrees C with little or no change due to freezing. About 35% of the individuals dehydrated drastically to below 1.1 mg mg(-1) dry weight at -6 degrees C, and consequently had lowered their body fluid melting point to ca. -6 degrees C at this time. Survival was high in both frozen and dehydrated animals at -6 degrees C, about 60%. Approximately 25% of the animals (both frozen and dehydrated individuals) had elevated glucose concentrations, but the mean glucose concentration was not increased to any great extent in any group due to cold exposure. The desiccating potential of ice was simulated using aqueous NaCl solutions at 0 degrees C. Water loss and survival in this experiment were in good agreement with results from freezing experiments. The influence of soil moisture on survival and tendency to dehydrate was also evaluated. However, soil moisture ranging between 0.74 g g(-1) and 1.15 g g(-1) dry soil did not result in any significant differences in survival or frequency of dehydrated animals even though the apparent wetness and structure of the soil was clearly different in these moisture contents.

Freezing survival and cryoprotective dehydration as cold tolerance mechanisms in the Antarctic nematode Panagrolaimus davidi.

The relative importance of freezing tolerance and cryoprotective dehydration in the Antarctic nematode Panagrolaimus davidi has been investigated. If nucleation of the medium is initiated at a high subzero temperature (-1 degree C), the nematodes do not freeze but dehydrate. This effect occurs in deionised water, indicating that the loss of water is driven by the difference in vapour pressure of ice and supercooled water at the same temperature. If the nematodes are held above their nucleation temperature for a sufficient time, or are cooled slowly, enough water is lost to prevent freezing (cryoprotective dehydration). However, if the medium is nucleated at lower temperatures or if the sample is cooled at a faster cooling rate, the nematodes freeze and can survive intracellular ice formation. P. davidi thus has a variety of mechanisms that ensure its survival in its harsh terrestrial Antarctic habitat.

Physiology of cold hardiness in earthworms

Abstract Physiological, biochemical and behavioral mechanisms involved in the winter survival of earthworms and earthworm cocoons are reviewed. Overwintering strategies of cold hardy invertebrates are commonly divided into two groups. In freeze-avoiding animals, ice formation in the tissues is lethal and winter survival is dependent on prolonged and extensive supercooling. Freeze-tolerant animals tolerate extracellular freezing up to a certain fraction of the body water. Hatched earthworms belong to the first group, having a behaviorally-based strategy, escaping frost in the soil by migration. The cold hardiness mechanism of earthworm cocoons is based on a protective dehydration of cocoons occurring when cocoons are exposed to subzero temperatures in a frozen environment. Due to the lower vapour pressure of ice compared to supercooled water at a given temperature, water evaporates from the cocoon surface and condenses onto ice in the surroundings. Dehydration of cocoons continues until vapour pressure equilibrium between cocoon fluids and surrounding ice is attained. At equilibrium the cocoons cannot freeze since the melting point of cocoon fluids equals ambient temperature. Because the melting point of cocoon fluids is high, −0.2 to −0.4°C, the cocoons lose substantial amounts of water, even at mild freezing exposures. As a response to dehydration the embryos of the cocoons accumulate a polyol, probably sorbitol, which may prevent deleterious effects of the extensive water loss coupled with vapour equilibration. Since dehydration is a key event when earthworm cocoons are exposed to low temperatures it is likely that tolerance to drought is important for cold survival. Substantial support for this hypothesis has been found in Dendrobaena octaedra which is far more tolerant to drought and cold than other investigated species. It is suggested that the described “protective dehydration mechanism” of cold hardiness should be considered in cold hardiness studies of other soil animals with high cuticular evaporation rates.

Development of an efficient single-step freeze-drying cycle for protein formulations.

An efficient freeze-drying cycle for recombinant human interleukin-1 receptor antagonist (rhIL-1ra) formulations, which contained glycine and sucrose as excipients, was developed. Development was based on characterizing the frozen formulations by thermal analysis and by examining the effect of various lyophilization process parameters on the sublimation rate of ice. Thermal analysis showed that the metastable glass of glycine in frozen formulation could be devitrified by slowly warming the frozen product to -15 degrees C. During drying, the sublimation rate of ice was increased as a linear function of the difference between the vapor pressure of ice at the product temperature (PO) and the chamber pressure (PC). Therefore, the product temperature (Tp) was maintained as high as possible at temperatures below Tg' of the formulation, in order to maximize the PO without allowing the collapse of cake. Although various combinations of shelf temperatures and chamber pressures could be used to obtain the same Tp, the combination of higher shelf temperature and lower chamber pressure was used to maximize sublimation rate. A single-step drying cycle was developed to take advantage of these observations. The shelf temperature was set for the secondary drying and the product temperature during primary drying was maintained below Tg' by adjusting the chamber pressure. As the sublimation completed, the product temperature increased naturally to the shelf temperature for the secondary drying. This process resulted in successful drying of 1 ml of rhIL-1ra formulation to 0.4% moisture content within 6 hours.

Heating and evaporation of Icy particles in the vicinity of comets

Although the detailed structure of the surface layers of a cometary nucleus is still unknown, there are good reasons that favor a porous and fragile ice/dust mixture. Such a nucleus will most probably emit ice particles which are blown off from the surface by sublimating gases. Their sizes may range from meter-sized boulders down to micro- and submicrometer-sized particles. In this paper we present a model which allows to calculate the “history” of ice particles with radii up to 100 μm released from a cometary nucleus. Temperatures and sublimation rates of both pure ice particles and ice particles polluted by a dark, nonvolatile material are computed. It is found that the black body approximation of the solar UV-radiation noticeably shortens the lifetimes of large (≥10 μm) particles. Moreover, the use of different formulae for the vapor pressure of ice found in the literature may affect the lifetime calculations by a factor of 10. The sublimation minimum predicted by Patashnik and Rupprecht (1975) for pure ice particles at a size of about 20 μm is confirmed. However, even small amounts of pollution in the ice tend to smear out this minimum and make it disappear which leads to much shorter particle lifetimes.

Grain Growth in Polar Ice: II. Application

AbstractGrain growth observed in polar ice that is not deforming rapidly can be accounted for if concentrations and distributions of extrinsic materials (microparticles, bubbles, and dissolved impurities) are characterized fully. Dissolved impurities segregate to grain boundaries and slow grain growth in all cold glacial ice. The high concentration of soluble impurities in Wisconsinan ice from the Dome C (Antarctica) ice core (and perhaps other ice cores) probably causes the small grain-sizes observed in that ice. Microparticles have little effect on grain growth in ordinary ice. In ice layers that appear dirty owing to concentrations of volcanic tephra (such as in the Byrd Station (Antarctica) ice core) or of morainal material, micro particles reduce grain-growth rates significantly. The relatively high vapor pressure of ice allows rapid growth and high mobility of intergranular necks, so grain growth in firn is limited by boundary migration rather than by neck growth. Bubbles formed by pore close-off at the firn-ice transition are less mobile than grain boundaries, causing bubble-boundary separation whenever geometric constraints are satisfied; however, such separation reduces grain-growth rates by only about 10%. The observed linear increase of grain area with time is thus predicted by theory, but the growth rate depends on soluble-impurity concentrations as well as on temperature.

Grain Growth in Polar Ice: II. Application

AbstractGrain growth observed in polar ice that is not deforming rapidly can be accounted for if concentrations and distributions of extrinsic materials (microparticles, bubbles, and dissolved impurities) are characterized fully. Dissolved impurities segregate to grain boundaries and slow grain growth in all cold glacial ice. The high concentration of soluble impurities in Wisconsinan ice from the Dome C (Antarctica) ice core (and perhaps other ice cores) probably causes the small grain-sizes observed in that ice. Microparticles have little effect on grain growth in ordinary ice. In ice layers that appear dirty owing to concentrations of volcanic tephra (such as in the Byrd Station (Antarctica) ice core) or of morainal material, micro particles reduce grain-growth rates significantly. The relatively high vapor pressure of ice allows rapid growth and high mobility of intergranular necks, so grain growth in firn is limited by boundary migration rather than by neck growth. Bubbles formed by pore close-off at the firn-ice transition are less mobile than grain boundaries, causing bubble-boundary separation whenever geometric constraints are satisfied; however, such separation reduces grain-growth rates by only about 10%. The observed linear increase of grain area with time is thus predicted by theory, but the growth rate depends on soluble-impurity concentrations as well as on temperature.

A random network model calculation of the free energy of liquid water

The random network model (RNM) of liquid water previously proposed by the authors is extended by imposition of a self-consistency condition designed to minimize the consequences of approximations used in representing the physical content of the model. The self-consistency condition imposed is the requirement that the computed values of T (∂S/∂T)p and (∂H/∂T)p be identical; this is achieved by modifying the quasiharmonic hindered translational and librational frequencies of the RNM. The temperature dependences of the frequencies so found are in good agreement with experiment. It is shown that the Gibbs free energy of the RNM is a minimum with respect to variation of the width of the hydrogen bond angle distribution when the new frequencies are used. As a test of the adequacy of the self-consistency condition for reduction of the error of prediction of thermodynamic properties, the isotope effect on the vapor pressure of ice I and liquid water is calculated; the RNM predictions are in good agreement with the observed values of ln(pH/pD).