scholarly journals Orthogonal Experimental Study on Heat Transfer Optimization of Backfill Slurry with Ice Particles

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Mei Wang ◽  
Peng Liu ◽  
Yuhang Jia ◽  
Yujiao Zhao ◽  
Bo Zhang
Keyword(s):  
Heat Flux ◽  
Cooling Effect ◽  
Experimental Simulation ◽  
Range Analysis ◽  
Mixture Ratio ◽  
Cement Ratio ◽  
Slurry Concentration ◽  
Ice Particles ◽  
Ice Water ◽  
Water Ratio

To reduce the risk of high-temperature geothermal environment in deep mine exploitation, an innovative method for cooling stopes by backfill slurry with ice particles has been focused on. In this paper, aiming at the cooling effect of backfill slurry with ice particles, an experimental device including stope region and ice-filled filling slurry region was established for temperature measurement experimental simulation study. The results showed the ice-filled slurry had a significant cooling effect on the stope region. Orthogonal design experiment and range analysis methods were applied for studying the influencing regularities of four factors, including boundary heat flux, ice-water ratio, sand-cement ratio, and slurry concentration. The effective cooling heat coefficient which is defined by radiation heat flux and boundary heat flux of surrounding rock was applied as an evaluation index for scheme optimization. The influencing rank of the four factors is boundary heat flux >sand-cement ratio >ice-water ratio >slurry concentration. By comprehensive analysis, the optimization of mixture ratio was obtained: the boundary heat flux of the simulated surrounding rocks is 111 W/m2, the ratio of ice to water is 8 : 5, the ratio of sand to cement is 4 : 1, and the slurry concentration is 64%.

scholarly journals Experimental Research on Heat Transfer and Strength Analysis of Backfill with Ice Grains in Deep Mines

2019 ◽  
Vol 11 (9) ◽  
pp. 2486 ◽  
Author(s):  
Xiaoyan Zhang ◽  
Yuhang Jia ◽  
Mei Wang ◽  
Lang Liu
Keyword(s):  
Mechanical Property ◽  
Temperature Distribution ◽  
Thermal Environment ◽  
Great Influence ◽  
Cooling Capacity ◽  
Strength Analysis ◽  
Deep Mine ◽  
Slurry Concentration ◽  
Ice Water ◽  
Water Ratio

In deep mines, two urgent problems are a high temperature thermal environment and solid waste. Filling the goaf with slurry mixed with ice grains is an effective way to solve these two problems simultaneously. The thermal property and mechanical property of the ice-added backfill have a great influence on the cooling effect in the deep mine. In this study, an experimental facility for measuring the temperature distribution of ice-added backfill slurry was established, and the temperature of backfill slurry with different proportions was measured. Then, the thermal properties of temperature distribution and cooling capacity and the mechanical property of uniaxial compressive strength of the backfill specimens were analyzed, and the results indicated the following: firstly, the cooling capacity of ice-added backfill specimens is negatively related with the slurry concentration C and is positively related with the ice-water ratio Ω; secondly, the strength of backfill specimens is affected by the slurry concentration C and ice-water ratio Ω by a contrary law compared to the cooling capacity; thirdly, ice-added backfill slurry with an ice-water ratio Ω of 1:1 has the best mechanical property after solidification. The effects of the slurry concentration and ice-water ratio on the thermal and mechanical properties were analyzed, and the results indicated that the optimum proportion of ice-added backfill slurry is a slurry concentration of 74% and an ice-water ratio of 1:1 in the present research range. This study is significant for the deep mine cooling method with ice-added backfill.

Preparation and Properties Research of Anti-Fogging Polypropylene Packaging Films

2012 ◽  
Vol 262 ◽  
pp. 581-585 ◽  
Author(s):  
Xiao Jin Gao ◽  
Li Qiang Huang ◽  
Xin Li
Keyword(s):  
Silica Sol ◽  
Range Analysis ◽  
Machine Direction ◽  
Polypropylene Film ◽  
Mixture Ratio ◽  
Elongation At Break ◽  
Coated Film ◽  
Span 80 ◽  
Optimum Formula ◽  
The Relationship

The anti-fogging properties of a new anti-fogging agent containing silicon sprayed on polypropylene were discussed. The anti-fogging agent was prepared by using silicone hydride and silica sol, the new anti-fogging agent with different consistency was daubed on the polypropylene film .The contact angle, first dripping time and ten drippings time of the anti-fogging PP films were tested. According to the range analysis, the best mixture ratio, which was just the optimum formula was found. The relationship between the anti-fogging agent consistence and the anti-fogging performance was discussed too. The result showed that the anti-fogging properties of the coated film were better and the mechanical properties of the coated film enhanced in some sort. The mixture ratio of the anti-fogging agent was that the silica sol was 12phr; the span 80 was 15%; the pH was 5.5. After the film was coated, the tensile strength of machine direction raised by 109.14% than the contrast. The elongation at break of transverse direction raised by 32.51MPa and that of machine direction raised by 17.95MPa. This anti-fogging agent containing silicon was preferable to polypropylene.

Trends in noctilucent clouds

2021 ◽  
Author(s):  
Franz-Josef Lübken ◽  
Gerd Baumgarten
Keyword(s):  
Carbon Dioxide ◽  
Water Vapor ◽  
Middle Atmosphere ◽  
Transport Model ◽  
Particle Model ◽  
Noctilucent Clouds ◽  
Middle Latitudes ◽  
Ice Particles ◽  
Highly Correlated ◽  
Ice Water

<p>Noctilucent clouds are often cited as potential indicators of climate change in the middle<br>atmosphere. They owe their existence to the very cold summer mesopause region (~130K) at mid<br>and high latitudes. We analyze trends derived from the Leibniz-Institute Middle Atmosphere<br>Model (LIMA) and the MIMAS ice particle model (Mesospheric Ice Microphysics And tranSport model)<br>for the years 1871-2008 and for middle, high and arctic latitudes, respectively.<br>Model runs with and without an increase of carbon dioxide and water vapor (from methane oxidation)<br>concentration are performed. Trends are most prominent after ~1960 when the increase of both<br>carbon dioxide and water vapor accelerates. Negative trends of (geometric) NLC altitudes are primarily<br>due to cooling below NLC altitudes caused by carbon dioxide increase. Increases of ice particle<br>radii and NLC brightness with time are mainly caused by an enhancement of water vapor.<br>Several ice layer and background parameter trends are similar at high and arctic latitudes but are<br>substantially different at middle latitudes. This concerns, for example, occurrence rates, ice water<br>content (IWC), and number of ice particles in a column. Considering the time period after 1960,<br>geometric altitudes of NLC decrease by approximately 260m per decade, and brightness increases by<br>roughly 50% (1960-2008), independent of latitude. NLC altitudes decrease by approximately 15-20m<br>per increase of carbon dioxide by 1ppmv. The number of ice particles in a column and also at the<br>altitude of maximum backscatter is nearly constant with time. At all latitudes, yearly mean NLC<br>appear at altitudes where temperatures are close to 145+/-1K. Ice particles are present nearly<br>all the time at high and arctic latitudes, but are much less common at middle latitudes. Ice water<br>content and maximum backscatter are highly correlated, where the slope depends on latitude. This<br>allows to combine data sets from satellites and lidars. Furthermore, IWC and the concentration of<br>water vapor at the altitude of maximum backscatter are also strongly correlated. Results from<br>LIMA/MIMAS agree nicely with observations.</p>

scholarly journals Radar Scattering from Ice Aggregates Using the Horizontally Aligned Oblate Spheroid Approximation

2012 ◽  
Vol 51 (3) ◽  
pp. 655-671 ◽  
Author(s):  
Robin J. Hogan ◽  
Lin Tian ◽  
Philip R. A. Brown ◽  
Christopher D. Westbrook ◽  
Andrew J. Heymsfield ◽  
...  
Keyword(s):  
Water Content ◽  
Millimeter Wave ◽  
Mie Scattering ◽  
Ice Particles ◽  
Size Relationship ◽  
Wave Radar ◽  
Mass Size ◽  
Ice Water Content ◽  
Ice Water ◽  
Reflectivity Factor

AbstractThe assumed relationship between ice particle mass and size is profoundly important in radar retrievals of ice clouds, but, for millimeter-wave radars, shape and preferred orientation are important as well. In this paper the authors first examine the consequences of the fact that the widely used “Brown and Francis” mass–size relationship has often been applied to maximum particle dimension observed by aircraft Dmax rather than to the mean of the particle dimensions in two orthogonal directions Dmean, which was originally used by Brown and Francis. Analysis of particle images reveals that Dmax ≃ 1.25Dmean, and therefore, for clouds for which this mass–size relationship holds, the consequences are overestimates of ice water content by around 53% and of Rayleigh-scattering radar reflectivity factor by 3.7 dB. Simultaneous radar and aircraft measurements demonstrate that much better agreement in reflectivity factor is provided by using this mass–size relationship with Dmean. The authors then examine the importance of particle shape and fall orientation for millimeter-wave radars. Simultaneous radar measurements and aircraft calculations of differential reflectivity and dual-wavelength ratio are presented to demonstrate that ice particles may usually be treated as horizontally aligned oblate spheroids with an axial ratio of 0.6, consistent with them being aggregates. An accurate formula is presented for the backscatter cross section apparent to a vertically pointing millimeter-wave radar on the basis of a modified version of Rayleigh–Gans theory. It is then shown that the consequence of treating ice particles as Mie-scattering spheres is to substantially underestimate millimeter-wave reflectivity factor when millimeter-sized particles are present, which can lead to retrieved ice water content being overestimated by a factor of 4.

scholarly journals Effective Radius of Ice Particles in Cirrus and Contrails

2011 ◽  
Vol 68 (2) ◽  
pp. 300-321 ◽  
Author(s):  
U. Schumann ◽  
B. Mayer ◽  
K. Gierens ◽  
S. Unterstrasser ◽  
P. Jessberger ◽  
...  
Keyword(s):  
Water Content ◽  
Effective Radius ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Small Particles ◽  
Particle Volume ◽  
Cross Sectional ◽  
Ice Particles ◽  
Ice Water Content ◽  
Ice Water

Abstract This paper discusses the ratio C between the volume mean radius and the effective radius of ice particles in cirrus and contrails. The volume mean radius is proportional to the third root of the ratio between ice water content and number of ice particles, and the effective radius measures the ratio between ice particle volume and projected cross-sectional area. For given ice water content and number concentration of ice particles, the optical depth scales linearly with C. Hence, C is an important input parameter for radiative forcing estimates. The ratio C in general depends strongly on the particle size distribution (PSD) and on the particle habits. For constant habits, C can be factored into a PSD and a habit factor. The PSD factor is generally less than one, while the habit factor is larger than one for convex or concave ice particles with random orientation. The value of C may get very small for power-law PSDs with exponent n between −4 and 0, which is often observed. For such PSDs, most of the particle volume is controlled by a few large particles, while most of the cross-sectional area is controlled by the many small particles. A new particle habit mix for contrail cirrus including small droxtal-shape particles is suggested. For measured cirrus and contrails, the dependence of C on volume mean particle radius, ambient humidity, and contrail age is determined. For cirrus, C varies typically between 0.4 and 1.1. In contrails, C = 0.7 ± 0.3, with uncertainty ranges increasing with the volume radius and contrail age. For the small particles in young contrails, the extinction efficiency in the solar range deviates considerably from the geometric optics limit.

scholarly journals The Ice Water Paths of Small and Large Ice Species in Hurricanes Arthur (2014) and Irene (2011)

2017 ◽  
Vol 56 (5) ◽  
pp. 1383-1404 ◽  
Author(s):  
Evan A. Kalina ◽  
Sergey Y. Matrosov ◽  
Joseph J. Cione ◽  
Frank D. Marks ◽  
Jothiram Vivekanandan ◽  
...  
Keyword(s):  
Small Particle ◽  
Large Particle ◽  
Radar Data ◽  
Particle Identification ◽  
Convective Precipitation ◽  
Ratio Distribution ◽  
Identification Scheme ◽  
Ice Particles ◽  
Precipitation Type ◽  
Ice Water

AbstractDual-polarization scanning radar measurements, air temperature soundings, and a polarimetric radar-based particle identification scheme are used to generate maps and probability density functions (PDFs) of the ice water path (IWP) in Hurricanes Arthur (2014) and Irene (2011) at landfall. The IWP is separated into the contribution from small ice (i.e., ice crystals), termed small-particle IWP, and large ice (i.e., graupel and snow), termed large-particle IWP. Vertically profiling radar data from Hurricane Arthur suggest that the small ice particles detected by the scanning radar have fall velocities mostly greater than 0.25 m s−1 and that the particle identification scheme is capable of distinguishing between small and large ice particles in a mean sense. The IWP maps and PDFs reveal that the total and large-particle IWPs range up to 10 kg m−2, with the largest values confined to intense convective precipitation within the rainbands and eyewall. Small-particle IWP remains mostly <4 kg m−2, with the largest small-particle IWP values collocated with maxima in the total IWP. PDFs of the small-to-total IWP ratio have shapes that depend on the precipitation type (i.e., intense convective, stratiform, or weak-echo precipitation). The IWP ratio distribution is narrowest (broadest) in intense convective (weak echo) precipitation and peaks at a ratio of about 0.1 (0.3).

scholarly journals A New Bulk Microphysical Scheme That Includes Riming Intensity and Temperature-Dependent Ice Characteristics

2011 ◽  
Vol 139 (3) ◽  
pp. 1013-1035 ◽  
Author(s):  
Yanluan Lin ◽  
Brian A. Colle
Keyword(s):  
Wrf Model ◽  
Computationally Efficient ◽  
Fall Velocity ◽  
Surface Precipitation ◽  
Ice Particles ◽  
Microphysical Processes ◽  
Empirical Coefficients ◽  
Oregon Cascades ◽  
Microphysical Parameterization ◽  
Ice Water

Abstract A new bulk microphysical parameterization (BMP) scheme is presented that includes a diagnosed riming intensity and its impact on ice characteristics. As a result, the new scheme represents a continuous spectrum from pristine ice particles to heavily rimed particles and graupel using one prognostic variable [precipitating ice (PI)] rather than two separate variables (snow and graupel). In contrast to most existing parameterization schemes that use fixed empirical relationships to describe ice particles, general formulations are proposed to consider the influences of riming intensity and temperature on the projected area, mass, and fall velocity of PI particles. The proposed formulations are able to cover the variations of empirical coefficients found in previous observational studies. The new scheme also reduces the number of parameterized microphysical processes by ∼50% as compared to conventional six-category BMPs and thus it is more computationally efficient. The new scheme (called SBU-YLIN) has been implemented in the Weather Research and Forecasting (WRF) model and compared with three other schemes for two events during the Improvement of Microphysical Parameterization through Observational Verification Experiment (IMPROVE-2) over the central Oregon Cascades. The new scheme produces surface precipitation forecasts comparable to more complicated BMPs. The new scheme reduces the snow amounts aloft as compared to other WRF schemes and compares better with observations, especially for an event with moderate riming aloft. Sensitivity tests suggest both reduced snow depositional growth rate and more efficient fallout due to the contribution of riming to the reduction of ice water content aloft in the new scheme, with a larger impact from the partially rimed snow and fallout.

Research on the Protection of Forward-Facing Cavity on the Flow Field of Low Total Pressure Opposing Jet

2014 ◽  
Vol 684 ◽  
pp. 335-340 ◽  
Author(s):  
Hai Bo Lu ◽  
Leng Han
Keyword(s):  
Heat Flux ◽  
Flow Field ◽  
Surface Heat Flux ◽  
Total Pressure ◽  
Flux Distribution ◽  
Surface Heat ◽  
Numerical Results ◽  
Cooling Effect ◽  
Heat Flux Distribution ◽  
Stable Flow

This paper focus on the detailed influence of forward-facing cavity on the opposing jet. The flow field of a hemisphere nose-tip with the combined configuration was simulated numerically and the surface heat flux distribution was obtained. The numerical results show that a suitable cavity is helpful for the opposing jet. With the same total pressure, the single opposing jet even can’t form a stable flow field and there is no cooling effect.

scholarly journals High ice water content at low radar reflectivity near deep convection – Part 2: Evaluation of microphysical pathways in updraft parcel simulations

2015 ◽  
Vol 15 (20) ◽  
pp. 11729-11751 ◽  
Author(s):  
A. S. Ackerman ◽  
A. M. Fridlind ◽  
A. Grandin ◽  
F. Dezitter ◽  
M. Weber ◽  
...  
Keyword(s):  
Water Vapor ◽  
Water Content ◽  
Deep Convection ◽  
Radar Reflectivity ◽  
Doppler Velocity ◽  
Diffusional Growth ◽  
Ice Particles ◽  
Ice Water Content ◽  
Water Drops ◽  
Ice Water

Abstract. The aeronautics industry has established that a threat to aircraft is posed by atmospheric conditions of substantial ice water content (IWC) where equivalent radar reflectivity (Ze) does not exceed 20–30 dBZ and supercooled water is not present; these conditions are encountered almost exclusively in the vicinity of deep convection. Part 1 (Fridlind et al., 2015) of this two-part study presents in situ measurements of such conditions sampled by Airbus in three tropical regions, commonly near 11 km and −43 °C, and concludes that the measured ice particle size distributions are broadly consistent with past literature with profiling radar measurements of Ze and mean Doppler velocity obtained within monsoonal deep convection in one of the regions sampled. In all three regions, the Airbus measurements generally indicate variable IWC that often exceeds 2 g m-3 with relatively uniform mass median area-equivalent diameter (MMDeq) of 200–300 μm. Here we use a parcel model with size-resolved microphysics to investigate microphysical pathways that could lead to such conditions. Our simulations indicate that homogeneous freezing of water drops produces a much smaller ice MMDeq than observed, and occurs only in the absence of hydrometeor gravitational collection for the conditions considered. Development of a mass mode of ice aloft that overlaps with the measurements requires a substantial source of small ice particles at temperatures of about −10 °C or warmer, which subsequently grow from water vapor. One conceivable source in our simulation framework is Hallett–Mossop ice production; another is abundant concentrations of heterogeneous ice freezing nuclei acting together with copious shattering of water drops upon freezing. Regardless of the production mechanism, the dominant mass modal diameter of vapor-grown ice is reduced as the ice-multiplication source strength increases and as competition for water vapor increases. Both mass and modal diameter are reduced by entrainment and by increasing aerosol concentrations. Weaker updrafts lead to greater mass and larger modal diameters of vapor-grown ice, the opposite of expectations regarding lofting of larger ice particles in stronger updrafts. While stronger updrafts do loft more dense ice particles produced primarily by raindrop freezing, we find that weaker updrafts allow the warm rain process to reduce competition for diffusional growth of the less dense ice expected to persist in convective outflow.

Design of Mix Proportion of Cement Mortar with High-Performance Composite Semi-Flexible Pavement

2013 ◽  
Vol 641-642 ◽  
pp. 342-345 ◽  
Author(s):  
Ya Jun Wang ◽  
Chang Ying Guo ◽  
Yan Feng Tian ◽  
Jian Jun Wang
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
Cement Mortar ◽  
Rupture Strength ◽  
Flexible Pavement ◽  
Mixture Ratio ◽  
Cement Ratio ◽  
Mix Proportion ◽  
High Performance Composite ◽  
The Relationship

Nine groups of cement mortar with different mix proportion were designed to measure their fluidity 0h, 0.25h, 0.5h, 0.75h and 1h later, compressive strength and rupture strength of 3d, 7d and 28d were also tested to find out the relationship between compressive strength, rupture strength, water-cement ratio and sand-cement ratio by software Origin. Considered the three factors above, the optimum mixture ratio was determined finally to meet the requirements.

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