Ice Mass Fraction Research Articles

The origins of ice crystals measured in mixed-phase clouds at the high-alpine site Jungfraujoch

Abstract. During the winter of 2013 and 2014 measurements of cloud microphysical properties over a 5-week period at the high-alpine site Jungfraujoch, Switzerland, were carried out as part of the Cloud Aerosol Characterisation Experiments (CLACE) and the Ice Nucleation Process Investigation and Quantification project (INUPIAQ). Measurements of aerosol properties at a second, lower site, Schilthorn, Switzerland, were used as input for a primary ice nucleation scheme to predict ice nuclei concentrations at Jungfraujoch. Frequent, rapid transitions in the ice and liquid properties of the clouds at Jungfraujoch were identified that led to large fluctuations in ice mass fractions over temporal scales of seconds to hours. During the measurement period we observed high concentrations of ice particles that exceeded 1000 L−1 at temperatures around −15 °C, verified by multiple instruments. These concentrations could not be explained using the usual primary ice nucleation schemes, which predicted ice nucleus concentrations several orders of magnitude smaller than the peak ice crystal number concentrations. Secondary ice production through the Hallett–Mossop process as a possible explanation was ruled out, as the cloud was rarely within the active temperature range for this process. It is shown that other mechanisms of secondary ice particle production cannot explain the highest ice particle concentrations. We describe four possible mechanisms that could lead to high cloud ice concentrations generated from the snow-covered surfaces surrounding the measurement site. Of these we show that hoar frost crystals generated at the cloud enveloped snow surface could be the most important source of cloud ice concentrations. Blowing snow was also observed to make significant contributions at higher wind speeds when ice crystal concentrations were < 100 L−1.

Lagrangian modelling of frazil ice in the ocean

AbstractA new modelling framework using Lagrangian particle tracking has been developed to assess dynamic and thermodynamic effects of underwater frazil ice. This frazil-ice model treats a Lagrangian particle as a bulk cluster of many frazil crystals, and calculates the thermodynamic growth of each particle and the corresponding budget of latent heat and fresh water. The effective density and viscosity of sea water depend on the mass fraction of underwater frazil ice, and hence affect ocean convection. An idealized experiment using our model successfully reproduces the formation of underwater frazil ice and its transition to grease ice at the surface. Because underwater frazil ice does not reduce the atmosphere/ocean heat exchange, surface heat flux and net sea-ice production in the experiment with frazil ice are relatively high compared with the experiment where surface cooling directly leads to columnar growth of a solid ice cover which effectively insulates the heat flux. These results suggest that large-scale sea-ice models which do not take account of the effects of frazil ice might underestimate atmosphere/ocean heat exchange, particularly at times of active new ice formation.

New Hailstone Physics. Part II: Interaction of the Variables

Abstract The reduction of parameter dimensions in Part I is complemented by the compaction of parameter space in Part II. The range of diameters is 0.5 ≤ D ≤ 8 cm, and the assumed liquid water content varies within 1 ≤ Wf ≤ 3 for dry growth and Wf ≤ 6 g m−3 for shedding. Entirely new data throw new light onto HMT and growth. Results are as follows: (i) dry growth is unimportant, since most hailstones grow spongy; (ii) radial growth is slow for dry and fast for spongy growth because less latent heat of freezing needs to be discarded if a smaller portion of the accreted water is frozen: this growth with shedding is particularly effective if the product Y of the net collection efficiency and ice mass fraction of the deposit is 0.2 ≤ Y ≤ 0.6; (iii) the lowest possible surface temperature tS for dry growth is −32.3°C. For water-skin-covered, spongy particles tS > −5°C, and tS > −0.55°C for shedding from wet surfaces without water skins; and (iv) the interplay between water-skin thickness and surface temperature allows interconnection of all variables. However, new icing experiments are necessary to prove the proposed sphere growth by special gyration, to quantify the components of Y, and to address water-skin properties and growth. Radically redesigned dynamic cloud models need to incorporate hail packaging and rain spectra evolution in clouds. The latter will connect hailstone shedding with a warm rain process that is parallel to and interacts with hail formation.

The D/H ratio in the atmospheres of Uranus and Neptune fromHerschel-PACS observations

Herschel-PACS measurements of the rotational R(0) and R(1) HD lines in the atmospheres of Uranus and Neptune are analyzed in order to derive a D/H ratio with improved precision for both planets. The derivation of the D/H ratio includes also previous measurements of the R(2) line by the Short Wavelength Spectrometer on board the Infrared Space Observatory (ISO). The available spectroscopic line information of the three rotational transitions is discussed and applied in the radiative transfer calculations. The best simultaneous fit of all three lines requires only a minor departure from the Spitzer temperature profile of Uranus and a departure limited to 2K from the Voyager temperature profile of Neptune (both around the tropopause). The resulting and remarkably similar D/H ratios for Uranus and Neptune are found to be (4.4$\pm$0.4)$\times10^{-5}$ and (4.1$\pm$0.4)$\times10^{-5}$ respectively. Although the deuterium enrichment in both atmospheres compared to the protosolar value is confirmed, it is found to be lower compared to previous analysis. Using the interior models of Podolak et al. (1995), Helled et al. (2011) and Nettelmann et al. (2013), and assuming that complete mixing of the atmosphere and interior occured during the planets history, we derive a D/H in protoplanetary ices between (5.75--7.0)$\times10^{-5}$ for Uranus and between (5.1--7.7)$\times10^{-5}$ for Neptune. Conversely, adopting a cometary D/H for the protoplanetary ices between (15-30)$\times10^{-5}$, we constrain the interior models of both planets to have an ice mass fraction of 14-32%, i.e. that the two planets are rock-dominated.

Pressure loss coefficients of ice slurry in horizontally installed flow dividers

The paper discusses pressure drops and pressure loss coefficients of ice slurry made from 10.6% ethylene alcohol, flowing through pipe fittings. Pressure drops of the ice slurry were measured in four pipe tees: ∅15mm, ∅18mm, ∅22mm and ∅28mm in branch direction and straight direction flow, as well as in three flow dividers: two, three, and four outlets. The inlet diameter of the dividers was 28mm and the outlet was 15mm. In experimental investigations, the mass fraction of ice varying from 5% to 30% was used. The Herschel–Bulkley model was applied to describe the characteristics of slurry flow. In calculations of pressure loss coefficients for the pipe tees, pressure drops for 15mm, 18mm, 22mm and 28mm tubes were used. Furthermore, pressure loss coefficients of the ice slurry flowing through four pipe tees and three flow dividers were obtained from experimental results and corresponding correlations for the laminar range were also developed.

Physical modeling, numerical simulations and experimental investigations of Non-Newtonian ice slurry flows

This paper presents an experimental and numerical investigation of the flow of ice slurry, composed of monopropylene glycol (MPG) as an additive. The objective is to demonstrate the influence of initial concentrations of this additive and the ice fraction on the rheological behavior of the corresponding ice slurry. The ice slurry flow was modeled in a continuous approach, where the fluid is assumed to behave like a single-phase fluid. Complex fluid behavior is treated by an effective kinematic viscosity, which depends on several parameters. In the present study the rheological model of Ostwald-de Waele is applied. The results – which concern mainly the effect of velocity, ice mass fraction and solute concentration on the pressure drop – show an overall close agreement between the experimental and the numerical and analytical results.

Bionic Design and Finite Element Analysis of Elbow in Ice Transportation Cooling System

With the increase in mining depth, mine heat harm has appeared to be more prominent. The mine heat harm could be resolved or reduced by ice refrigeration. Thus, ice transportation through pipeline becomes a critical problem; typically flow resistance occurs in the elbow. In the present study, according to the analysis of the surface morphology of fish scale, a biomimetic functional surface structure for the interior wall of elbow is designed. Based on the theory of liquid-solid two phase flow, a CFD numerical simulation of ice-water mixture flowing through the elbow is carried out using finite element method. Conventional experiments of pressure drop and flow resistance for both bionic and common elbows are conducted to test the effect of the bionic elbow on flow resistance reduction. It is found that with the increase in the ice mass fraction in the ice-water mixture, the effect of bionic elbow on resistance reduction becomes more obvious.

Numerical modeling of double-diffusive convection in ice slurry storage tank

The interaction between laminar Rayleigh–Benard convection and non-isothermal melting process is studied for the case of ice slurry kept in a rectangular cavity heated from the bottom. Clear visualization of the Rayleigh–Benard convective cells and their interaction with the melting front are obtained. It is observed that the convective cells are characterized by zones of up-flow and down-flow, resulting in the development of a nonplanar interface. Because of the continuous advancement of the solid/liquid interface, the effective solid height of the cavity keeps decreasing. The results include also the evolution of the solid–liquid interface, the local temperature and the ice mass fraction inside the storage tank.

Annealing effects on hydrogen ordering in KOD-doped ice observed using neutron diffraction

We measured the neutron powder diffraction of 0.013 M KOD-doped D 2O ice to investigate the formation process of ice XI, a hydrogen-ordered phase of ice Ih. The doped ice Ih transformed to ice XI after annealing at 57 and subsequently at 68 K. The mass fraction of ice XI to that of the doped ice ( f) was estimated using Rietveld analysis for each sample. The f value of the doped ice, which had once experienced being ice XI ( f = 0.23), was larger than that of the doped ice, which had never experienced being ice XI ( f = 0.14). Results indicate that small hydrogen-ordered domains remained in the ice Ih, which had once transformed to ice XI, and accelerated the phase transition from ice Ih to ice XI. Results further suggest that large amounts of ice on icy bodies in our solar system can transform to ice XI, which might be detectable using infrared telescopes or planetary exploration in the near future.

Thermal and hydrodynamic considerations of ice slurry in heat exchangers

This article focuses on the behavior in heat exchangers of an ice slurry composed of fine ice particles inside an ethanol–water solution. The heat transfer and friction characteristics were studied in two double pipe heat exchangers, one with a smooth surface and another with an improved surface. Heat transfer coefficients and pressure drops were experimentally investigated for the slurry flowing in the internal tube with ice mass fractions ranging from 0 to 30% and with flow velocities between 0.3 and 1.9 m s −1. For some flow velocities, the results showed that an increase in the ice fractions caused a change in the slurry flow structure influencing the evolution of the pressure drops and the heat transfer coefficients. Critical ice fraction values were determined corresponding to a change flow structure from laminar to turbulent motion revealed by the evolution of the friction factor.

Formation and detection of Earth mass planets around low mass stars

We investigate an in situ formation scenario for Earth-mass terrestrial planets in short-period, potentially habitable orbits around low-mass stars (M∗<0.3M⊙). We then investigate the feasibility of detecting these Earth-sized planets. We find that such objects can feasibly be detected by a ground-based transit survey if their formation frequency is high and if correlated noise can be controlled to sub-milli-magnitude levels. Our simulations of terrestrial planet formation follow the growth of planetary embryos in an annular region spanning 0.036 AU⩽a⩽0.4 AU around a fiducial M7 (0.12M⊙) primary. Initial distributions of planetary embryos are calculated using the semi-analytic evolutionary model outlined by Chambers [Chambers, J., 2006. Icarus 180, 496–513]. This model specifies how planetary embryos grow to the stage where the largest embryo masses lie in the 1024 g⩽Membryo⩽5×1026 g range (corresponding to the close of the so-called oligarchic growth phase). We then model the final phases of terrestrial planet assembly by allowing the embryos to interact with one another via a full N-body integration using the Mercury code. The final planetary system configurations produced in the simulations generally consist of 3–5 planets with masses of order 0.1–1.0M⊕ in or near the habitable zone of the star. We explore a range of disk masses (0.2M⊕ to 3.3M⊕) to illuminate the role disk mass plays in our results. With a high occurrence fraction or fortunate alignments, transits by the planet formed in our simulations could be marginally detected with modest telescopes of aperture 1 m or smaller around the nearest M-dwarf stars. To obtain a concrete estimate of the detectability of the planets arising in our simulations, we present a detailed Monte-Carlo transit detection simulation incorporating sky observability, local weather, a target list of around 200 nearby M-dwarfs, and a comprehensive photometric noise model. We adopt a baseline 1.5 mmag level of correlated stellar noise sampled from the photometry of the planet-bearing red dwarf Gl 436. With this noise model we find that detection of 1R⊕ planets around the local M-dwarfs is challenging for a ground-based photometric search, but that detection of planets of larger radius is a distinct possibility. The detection of Earth-sized planets is straightforward, however, with an all-sky survey by a low-cost satellite mission. Given a reduced correlated noise level of 0.45 mmag and an intermediate planetary ice-mass fraction of planets orbiting a target list drawn from the nearest late-type M dwarfs, a ground-based photometric search could detect, on average, 0.3 of these planets within two years and another 0.5 over an indefinitely extended search. A space-based photometric search (similar to the TESS mission) should discover ∼17 of these Earth-sized planets during its two year survey, with an assumed occurrence fraction of 28%.

Experimental investigation of ice slurry heat transfer in horizontal tube

Heat transfer of ice slurry flow based on ethanol–water mixture in a circular horizontal tube has been experimentally investigated. The secondary fluid was prepared by mixing ethanol and water to obtain initial alcohol concentration of 10.3% (initial freezing temperature -4.4 °C). The heat transfer tests were conducted to cover laminar and slightly turbulent flow with ice mass fraction varying from 0% to 22% depending on test performed. Measured heat transfer coefficients of ice slurry are found to be higher than those for single phase fluid, especially for laminar flow conditions and high ice mass fractions where the heat transfer is increased with a factor 2 in comparison to the single phase flow. In addition, experimentally determined heat transfer coefficients of ice slurry flow were compared to the analytical results, based on the correlation by Sieder and Tate for laminar single phase regime, by Dittus–Boelter for turbulent single phase regime and empirical correlation by Christensen and Kauffeld derived for laminar/turbulent ice slurry flow in circular horizontal tubes. It was found that the classical correlation proposed by Sieder and Tate for laminar forced convection in smooth straight circular ducts cannot be used for heat transfer prediction of ice slurry flow since it strongly underestimates measured values, while, for the turbulent flow regime the simple Dittus–Boelter relation predicts the heat transfer coefficient of ice slurry flow with high accuracy but only up to an ice mass fraction of 10% and Re cf > 2300 regardless of imposed heat flux. For higher ice mass fractions and regardless of the flow regime, the correlation proposed by Christensen and Kauffeld gives good agreement with experimental results.

Experimental investigation of ice slurry flow pressure drop in horizontal tubes

Pressure drop behaviour of ice slurry based on ethanol–water mixture in circular horizontal tubes has been experimentally investigated. The secondary fluid was prepared by mixing ethyl alcohol and water to obtain initial alcohol concentration of 10.3% (initial freezing temperature −4.4 °C). The pressure drop tests were conducted to cover laminar and slightly turbulent flow with ice mass fraction varying from 0% to 30% depending on test conditions. Results from flow tests reveal much higher pressure drop for higher ice concentrations and higher velocities in comparison to the single phase flow. However for ice concentrations of 15% and higher, certain velocity exists at which ice slurry pressure drop is same or even lower than for single phase flow. It seems that higher ice concentration delay flow pattern transition moment (from laminar to turbulent) toward higher velocities. In addition experimental results for pressure drop were compared to the analytical results, based on Poiseulle and Buckingham–Reiner models for laminar flow, Blasius, Darby and Melson, Dodge and Metzner, Steffe and Tomita for turbulent region and general correlation of Kitanovski which is valid for both flow regimes. For laminar flow and low buoyancy numbers Buckingham–Reiner method gives good agreement with experimental results while for turbulent flow best fit is provided with Dodge–Metzner and Tomita methods. Furthermore, for transport purposes it has been shown that ice mass fraction of 20% offers best ratio of ice slurry transport capability and required pumping power.

Dense-Phase Pneumatic Conveying of Slush Ice Through Plastic Pipes

Ice is being used in certain deep mines to transport refrigeration to underground areas. Research has been carried out previously into the pipeline conveying characteristics of ice with air, but there remains a lack of knowledge about some aspects of this complex flow. Previous articles (Sheer, 1995; Sheer et al., 2001) have described experimental results on the pneumatic conveying of ice in particulate form (“hard” ice) through successive long horizontal and vertical sections of pipelines into mines. More recent research has been carried out to determine the conveying characteristics of “slush” ice that resembles wet snow, with an ice mass fraction range of 65–75%. Laboratory pneumatic conveying tests with slush ice were conducted through three horizontal plastic pipelines with inner diameters of 43, 54, and 69 mm, each pipeline being approximately 50 m long and including various bends. The tests yielded numerical and photographic data that were used to investigate the conveying characteristics of slush ice (including flow regime transition to plug flow and pressure gradients) and to compare them with the previous results for particulate ice. It was found that the conveying characteristics of the slush depend strongly on the water content. Correlations are proposed for multiphase friction factors.

Entropy generation in ice slurry pipe flow

The purpose of this work is to investigate the entropy generation in ice slurry pipe flow. Fully developed laminar flow is considered with uniform heat flux at the walls. The fluid behaves as a non-Newtonian fluid following the power-law model. Expressions for velocity, entropy generation number and average entropy generation number are obtained as function of mass fraction of ice and the dimensionless group parameter.

Preparation of Porous Polycaprolactone Scaffolds by Using Freeze-Drying Combined Porogen-Leaching Methods

The microstructure of scaffold was one of key factors for tissue engineering. Porous polycaprolactone (PCL) scaffolds were fabricated by combination of porogen-leaching and freeze-drying process. Ice particulates were used as porogen material, and PCL solutions in chloroform were mixed with ice particulates for 5minuture at zero temperature. Then the mixture was freezed in liquid nitrogen, and porous scaffold was prepared by freeze - drying finally. The microstructure and properties of the scaffolds were investigated. Porous structure of the scaffolds showed that good 3D microstructure and no porogen remained in the scaffold; pore size and porosity were determined by the size and mass fraction of ice particulates. The results demonstrated that the Scaffolds possessed open and interconnected pores with sizes ranging from several μm to more than 300μm and porosities of 50~80%.

Aerosol partitioning between the interstitial and the condensed phase in mixed‐phase clouds

The partitioning of aerosol particles between the cloud and the interstitial phase (i.e., unactivated aerosol) has been investigated during several Cloud and Aerosol Characterization Experiments (CLACE‐3, CLACE‐3 and CLACE‐4) conducted in winter and summer 2004 and winter 2005 at the high alpine research station Jungfraujoch (3580 m altitude, Switzerland). Ambient air was sampled using different inlets in order to determine the activated fraction of aerosol particles, FN, defined as the fraction of the total aerosol number concentration (with particle diameter dp &gt; 100 nm) that has been incorporated into cloud particles. The liquid and ice water content of mixed‐phase clouds were characterized by analyzing multiple cloud probes. The dependence of the activated fraction on several environmental factors is discussed on the basis of more than 900 h of in‐cloud observations and parameterizations for key variables are given. FN is found to increase with increasing liquid water content and to decrease with increasing particle number concentration in liquid clouds. FN also decreases with increasing cloud ice mass fraction and with decreasing temperature from 0 to −25°C. The Wegener‐Bergeron‐Findeisen process probably contributed to this trend, since the presence of ice crystals causes liquid droplets to evaporate, thus releasing the formerly activated particles back into the interstitial phase. Ice nucleation could also have prevented additional cloud condensation nuclei from activating. The observed activation behavior has significant implications for our understanding of the indirect effect of aerosols on climate.

Investigation into the transportation and melting of thick ice slurries in pipes

This paper presents the results of experiments and modelling carried out on ice slurries flowing in uninsulated steel pipes with a nominal diameter of 50 mm. The slurries used were formed from 4.75% NaCl aqueous solution and had ice mass fractions in the range 18–42%, with a view to the use of thick ice slurry ‘pigs’ as a pipeline clearing technique. Of particular interest was the distance over which such slurries can survive as plug-like entities, before melting reduces them to ineffective thin two-phase suspensions. The experiments showed that for small volumes of slurry, survivability is directly proportional to the quantity of slurry used, but that increasing the ice fraction has a more marked effect. A simple one-dimensional numerical model that accounts for transportation, heat transfer and melting was developed that produces reasonable predictions.

Generalized non-Newtonian flow of ice-slurry

In this paper, we present results of the studies of pressure drops during laminar and turbulent flows of ice slurry produced on the basis of 10.6% ethanol solution. The results, obtained at various ice mass fractions, include pressure drops determined in horizontal ducts of circular, rectangular, and slit cross-sections. The critical Reynolds numbers were also determined. By introducing the Kozicki's generalized definition of the Reynolds number, it was possible to verify the Fanning, Blasius and Dodge–Metzner–Kozicki relations used for determining ice slurry pressure drops during its flow through channels of various cross-sections.

Properties of sea ice and overlying snow in the Southern Sea of Okhotsk

The general properties of sea ice and overlying snow in the southern Sea of Okhotsk were examined during early February of 2003 to 2005 with the P/V “Soya”. Thin section analysis of crystal structure revealed that frazil ice (48% of total core length) was more prevalent than columnar ice (39%) and that stratigraphic layering was prominent with a mean layer thickness of 12 cm, indicating that dynamic processes are essential to ice growth. The mean thickness of ice blocks and visual observations suggest that ridging dominates the deformation process above thicknesses of 30 to 40 cm. As for snow, it was found that faceted crystals and depth hoar are dominant (78%), as which is also common in the Antarctic sea ice, and is indicative of the strong vertical temperature gradients within the snow. Stable isotope measurements (δ18O) indicate that snow ice occupies 9% of total core length and that the mass fraction of meteoric ice accounts for 1 to 2% of total ice volume, which is lower than the Antarctic sea ice. Associated with this, the effective fractionation coefficient during the freezing of seawater was also derived. Snow ice was characterized by lower density, higher salinity, and nearly twice the gas content of ice of seawater origin. In addition, it is shown that the surface brine volume fraction and freeboard are well correlated with ice thickness, indicating some promise for remote sensing approaches to the estimation of ice thickness.