scholarly journals Research and Application of the Local Differential Freezing Technology in Deep Alluvium

2020 ◽  
Vol 2020 ◽  
pp. 1-15 ◽  
Author(s):  
Bin Wang ◽  
Chuanxin Rong ◽  
Hua Cheng ◽  
Zhishu Yao ◽  
Haibing Cai
Keyword(s):  
Temperature Drop ◽  
Freezing Temperature ◽  
Average Temperature ◽  
Site Monitoring ◽  
Expansion Range ◽  
Frozen Wall ◽  
Shaft Lining ◽  
Differential Control ◽  
Drop Rate ◽  
Conventional Freezing

Aiming at the complicated engineering conditions of the auxiliary shaft repair in the Banji coal mine, it was proposed to seal the water around the shaft lining by differential control freezing technology using double rows of holes. The outer row of holes is completely frozen, and the inner row of holes is local differential frozen according to the degree of destruction of the shaft lining. The local differential freezing pipe was successfully developed according to engineering requirements. Numeral simulations were used to predict the development of the freezing temperature field; the results showed that the inward expansion range of the frozen wall formed by the inner row freezing holes was effectively limited and the temperature drop rate of the shaft lining was significantly reduced after the local differential freezing technique was adopted. The on-site monitoring data showed that the temperature of the limited freezing layer was about 5°C higher than that of the conventional freezing layer. During the drainage work and the construction of the new shaft lining, the thickness and average temperature of the frozen wall remained stable, indicating that the implementation of the local differential freezing technology achieved the expected results. Further analysis showed that when the temperature of the limited freezing part of freezing pipes in the inner row was controlled within the range of −15 to −10°C, not only could the frozen wall reach the design thickness and strength but the frost heaving pressure on the existing shaft lining could be effectively eliminated.

scholarly journals Evolution Laws for Frozen Wall Formation under Conditions of Sudden Seepage

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Song Zhang ◽  
Zurun Yue ◽  
Tiecheng Sun ◽  
Yufu Han ◽  
Wei Gao ◽  
...  
Keyword(s):  
Temperature Field ◽  
Flow Velocity ◽  
Freezing Temperature ◽  
Model Tests ◽  
Seepage Velocity ◽  
Distribution Law ◽  
Average Temperature ◽  
Ground Freezing ◽  
Artificial Ground Freezing ◽  
Frozen Wall

Sudden seepage is a special working condition affecting artificial ground freezing (AGF) in many projects which results in significant differences within the temperature field. In order to study the characteristics of frozen walls influenced by water flow, a series of model tests were carried out at different seepage velocities. The model test results show that a frozen wall will change from symmetrical to eccentric as the cooling energy absorption of the soil and the brine return temperature increase. In model tests, when the seepage velocity was 0∼30 m/d, the frozen wall was partially destroyed. When the seepage velocity exceeded 30 m/d, the frozen wall was completely destroyed. This study examines the expansion rate of the upstream and downstream freezing fronts, and the distribution law of the freezing temperature field, the average temperature change under different seepage speeds, and the bearing capacity of the freezing wall are analyzed. Research on these factors suggests that a frozen wall has a certain level of resistance to sudden seepage. When the flow velocity is small, the freezing effect will be strengthened. With an increase in the flow velocity, the freezing effect will gradually weaken. Based on these conclusions, the current study points out targeted solutions that should be adopted in cases of sudden seepage in a project.

scholarly journals Pool Boiling of Nanofluids on Biphilic Surfaces: An Experimental and Numerical Study

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 125
Author(s):  
Eduardo Freitas ◽  
Pedro Pontes ◽  
Ricardo Cautela ◽  
Vaibhav Bahadur ◽  
João Miranda ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Numerical Model ◽  
Heat Dissipation ◽  
Numerical Study ◽  
Pool Boiling ◽  
Temperature Drop ◽  
Surface Cooling ◽  
Average Temperature ◽  
Gold Silver

This study addresses the combination of customized surface modification with the use of nanofluids, to infer on its potential to enhance pool-boiling heat transfer. Hydrophilic surfaces patterned with superhydrophobic regions were developed and used as surface interfaces with different nanofluids (water with gold, silver, aluminum and alumina nanoparticles), in order to evaluate the effect of the nature and concentration of the nanoparticles in bubble dynamics and consequently in heat transfer processes. The main qualitative and quantitative analysis was based on extensive post-processing of synchronized high-speed and thermographic images. To study the nucleation of a single bubble in pool boiling condition, a numerical model was also implemented. The results show an evident benefit of using biphilic patterns with well-established distances between the superhydrophobic regions. This can be observed in the resulting plot of the dissipated heat flux for a biphilic pattern with seven superhydrophobic spots, δ = 1/d and an imposed heat flux of 2132 w/m2. In this case, the dissipated heat flux is almost constant (except in the instant t* ≈ 0.9 when it reaches a peak of 2400 W/m2), whilst when using only a single superhydrophobic spot, where the heat flux dissipation reaches the maximum shortly after the detachment of the bubble, dropping continuously until a new necking phase starts. The biphilic patterns also allow a controlled bubble coalescence, which promotes fluid convection at the hydrophilic spacing between the superhydrophobic regions, which clearly contributes to cool down the surface. This effect is noticeable in the case of employing the Ag 1 wt% nanofluid, with an imposed heat flux of 2132 W/m2, where the coalescence of the drops promotes a surface cooling, identified by a temperature drop of 0.7 °C in the hydrophilic areas. Those areas have an average temperature of 101.8 °C, whilst the average temperature of the superhydrophobic spots at coalescence time is of 102.9 °C. For low concentrations as the ones used in this work, the effect of the nanofluids was observed to play a minor role. This can be observed on the slight discrepancy of the heat dissipation decay that occurred in the necking stage of the bubbles for nanofluids with the same kind of nanoparticles and different concentration. For the Au 0.1 wt% nanofluid, a heat dissipation decay of 350 W/m2 was reported, whilst for the Au 0.5 wt% nanofluid, the same decay was only of 280 W/m2. The results of the numerical model concerning velocity fields indicated a sudden acceleration at the bubble detachment, as can be qualitatively analyzed in the thermographic images obtained in this work. Additionally, the temperature fields of the analyzed region present the same tendency as the experimental results.

The Field Measure of Special Strata Freezing Temperature in West Area

2012 ◽  
Vol 170-173 ◽  
pp. 1207-1210
Author(s):  
Jun Hao Chen ◽  
Rui Zhang
Keyword(s):  
Engineering Design ◽  
Freezing Temperature ◽  
Design Requirement ◽  
Shaft Sinking ◽  
Design Requirements ◽  
Security Information ◽  
Frozen Wall ◽  
The Difference ◽  
Circle Tube ◽  
Field Measure

A new round of upsurge of mine well construction were set off in the west area, but there are many problems, this article through the field measure of special strata freezing temperature in Bo-jiang-hai-zi coal mine airshaft, use the freezing shaft sinking security information network visualization platform that developed by Anhui University of Science and Technology, analysis several different strata, obtain the overall temperatre decline rate, and compare the difference between in-site shaft well temperature and the calculation value at different position, and difference is very small, it shows that the platform can good response the actual situation. Through calculation, the frozen wall thickness, average of frozen wall temperature, shaft well temperature are meet the engineering design requirement, so propose that in west area at the freezing method mine well construction, the main purpose is waterproof, and use single circle tube freezing can satisfy engineering design requirements.

Optimization of Double-Ring-Pipe Freezing Scheme for Tunnel Cross-Passage Construction

2012 ◽  
Vol 446-449 ◽  
pp. 2262-2266 ◽  
Author(s):  
Xiang Dong Hu ◽  
Bing Yi Ji
Keyword(s):  
Frozen Soil ◽  
Shield Tunnel ◽  
Freezing Process ◽  
Unfrozen Water ◽  
Double Ring ◽  
Average Temperature ◽  
Unfrozen Water Content ◽  
Ground Freezing ◽  
Different Temperatures ◽  
Frozen Wall

For numerically simulating the phase change of water in ground freezing process, a correct method is proposed in this paper, that the unfrozen water content in frozen soil is taken into account to calculate the enthalpy value at different temperatures. A calculation example of a cross-passage project in shield tunnel shows that the thickness and the average temperature of the frozen wall calculated by this method are very close to the in-situ monitored data. Based on this method, by comparison of the development rate of thickness and the average temperature of the frozen wall according to different design plans, the ground freezing scheme for the cross-passage is optimized for the shortest duration of freeze in agreement with the work standard. The study could enlighten the design for similar projects in the future.

scholarly journals Simulation of solar PV surface temperature with dimpled fin cooling

2022 ◽  
Vol 1217 (1) ◽  
pp. 012015
Author(s):  
M F Ibrahim ◽  
M S Misaran ◽  
N A Amaludin
Keyword(s):  
Temperature Drop ◽  
Solar Panel ◽  
Solar Irradiation ◽  
Solar Pv ◽  
Average Temperature ◽  
Pv Module ◽  
Air Convection ◽  
Percentage Difference ◽  
Experimental Works ◽  
Forced Air

Abstract A significant number of cooling technologies have been developed to maintain the PV module temperature within subscribed limits. This paper represents the simulation study of active cooling forced air convection with fins attached to the back of the solar panel using CFD SimScale software. It has been first carefully validated against experimental and numerical results available in the literature. The number of fins and the shape of perforated and dimpled in each fin were varied to compare cooling performance. Three types of fins were adapted into this simulation: traditional fins, circular, and triangle perforated/dimpled fins. The effect of solar irradiation and velocity inlet was also reviewed by applying the nominal operating condition from the experimental works. Results indicated that fin channels are a very effective cooling technique, which significantly reduces the average temperature of the PV cell, especially when increasing the number of fins from 20 to 26 fins. Also, the results show that the dimpled triangle fin had the highest average temperature drop with a percentage difference of 6% compared with the solar panel cooling with traditional fins.

scholarly journals Heat exchanger design studies for molten salt fast reactor

2019 ◽  
Vol 5 ◽  
pp. 12
Author(s):  
Uğur Köse ◽  
Ufuk Koç ◽  
Latife Berrin Erbay ◽  
Erdem Öğüt ◽  
Hüseyin Ayhan
Keyword(s):  
Heat Exchanger ◽  
Molten Salt ◽  
Fast Reactor ◽  
Heat Exchangers ◽  
Temperature Drop ◽  
Freezing Temperature ◽  
Fuel Temperature ◽  
Design Studies ◽  
The Core ◽  
Heat Exchanger Design

In this study, conceptual design for primary heat exchanger of the Molten Salt Fast Reactor is made. The design was carried out to remove the produced heat from the reactor developed under the SAMOFAR project. Nominal power of the reactor is 3 GWth and it has 16 heat exchangers. There are several requirements related to the heat exchanger. To sustain the steady-state conditions, heat exchangers have to transfer the heat produced in the core and it has to maintain the temperature drop as much as the temperature rise in the core due to the fission. It should do it as fast as possible. It must also ensure that the fuel temperature does not reach the freezing temperature to avoid solidification. In doing so, the fuel volume in the heat exchanger must not exceed the specified limit. Design studies were carried out taking into account all requirements and final geometric configurations were determined. Plate type heat exchanger was adopted in this study. 3D CFD analyses were performed to investigate the thermal-hydraulic behavior of the system. Analyses were made by ANSYS-Fluent commercial code. Results are in a good agreement with limitations and requirements specified for the reactor designed under the SAMOFAR project.

scholarly journals The Development Law of the Freezing Temperature Field of a Calcareous Clay Layer

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Zhi Wang ◽  
Chuanxin Rong ◽  
Meng Du ◽  
Maoyan Ma ◽  
Xiangyang Liu
Keyword(s):  
Temperature Field ◽  
Freezing Point ◽  
Early Stage ◽  
Freezing Temperature ◽  
Temperature Fields ◽  
Clay Layer ◽  
Engineering Construction ◽  
Temperature Measurement Point ◽  
Frozen Wall ◽  
Saddle Shape

The problem of “difficult” freezing of the calcareous clay layer fractures in freezing pipes has been investigated. Based on the engineering background of the deep calcareous clay in the Yangcun Mine, model tests were carried out in order to conduct in-depth research on the development law of the freezing temperature field of this clay layer. The test results have shown that the calcareous clay has a freezing point of −1.3°C under the action of both the water and the soil’s chemistry and the supercooling temperature can be as low as −3.8°C because of its complex mineral composition causing poor thermal conductivity. This means that the calcareous clay will freeze slowly than the other layers of the soil. The time taking for the temperature fields to intersect is 2.5 h, which is equivalent to 127.6 days in the actual engineering. In the three sections, each temperature measurement point in the temperature field had an irregular saddle shape in the temperature space at the same time, and the ratio of the time between the formation and total melting of the frozen wall was 1 : 1.91. The development speed of the thickness of the frozen wall from 5 h to 16 h was 17.9 mm/h, and the development speed from 16 h to 70 h was 1.96 mm/h; corresponding to the actual development speed of the thickness of the frozen wall which were 0.0123 m/d and 0.0014 m/d, respectively. These speeds were significantly slower than the development speed of the thickness of the freezing wall of the general sandy clay layer, which were 0.0515 m/d in the early stage and 0.02 m/d in the later stage. The thin thickness and low strength of the frozen wall of the calcareous clay layer cause the fracture of the frozen pipes, which should be paid attention to in actual engineering construction.

The Mechanics Experimental Study of the Artificially Frozen Soil in Cretaceous Strata

2011 ◽  
Vol 94-96 ◽  
pp. 1844-1847 ◽  
Author(s):  
Hao Cui ◽  
Dong Wei Li ◽  
Ren He Wang
Keyword(s):  
Experimental Study ◽  
Creep Test ◽  
Strength Criterion ◽  
Freezing Temperature ◽  
Frozen Soil ◽  
Design Approach ◽  
Wall Strength ◽  
Strength Tests ◽  
Frozen Wall ◽  
Uniaxial Strength

Through the large number uniaxial strength tests and the creep test tests of the artificially frozen soil of Cretaceous strata, we obtained that the frozen wall in Cretaceous strata met the Moore - Coulomb strength criterion, and the artificially frozen soil strength increased from 6.5MPa in -5 °C to 12.0MPa in -15 °Cwith the freezing temperature decreased, Poisson's ratio from 0.35 down to -5 °C -15 °C at 0.18. Using viscoelastic-plastic theory we got the deep frozen wall strength and thickness of the Bojiang - Haizi mine in Cretaceous strata, practice showed that: the design approach in this paper was reasonable.

scholarly journals Rational Construction of Superhydrophobic PDMS/PTW@cotton Fabric for Efficient UV/NIR Light Shielding

2021 ◽  
Author(s):  
Jianying Huang ◽  
Gang Shen ◽  
Yimeng Ni ◽  
Kim Hoong Ng ◽  
Tianxue Zhu ◽  
...  
Keyword(s):  
Cotton Fabric ◽  
Temperature Drop ◽  
Direct Sunlight ◽  
Energy Saving Potential ◽  
Average Temperature ◽  
Nir Light ◽  
Application Potential ◽  
Ultraviolet Protection ◽  
Rational Construction ◽  
Recorded Temperature

Abstract Passive daytime radiative cooling (PDRC) material has intrigued increasing attentions with its energy saving potential and smart cloth feature. In this work, PDRC cotton fabric with superhydrophobicity, ultraviolet protection and self-cleaning competency was successful constructed through the deposition chemically-stable potassium titanate whiskers (PTW) and polydimethylsiloxane (PDMS) onto cotton fibers. While featured with ultra-high contact angle of 151.9±0.9 °, the synthesized fabric marked an average temperature drop of ~5.1 ℃, bestowed to its high sunlight reflectivity of 83 % and infrared emissivity of nearly 90 %. On the other hand, real human tests further confirmed the practicality of the modified cotton fabric, with the recorded temperature drops ranged from 3.1~4.7 ℃ under direct sunlight. Such performance elucidated a significant improvement upon PTW/PDMS modification, which outperformed that of pristine cotton fabric. Surmising from these, the synthesized superhydrophobic fabric exhibits advantageous techno-economical index with its excellent performance and simple preparation, therefore manifesting limitless application potential, particularly in outdoor clothing and other facilities.

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