Analysis on the convection cooling process of crushed-rock embankment of high-grade highway in permafrost regions

2012 ◽  
Vol 78 ◽  
pp. 115-121 ◽  
Author(s):  
Jin Qian ◽  
Qi-hao Yu ◽  
Yan-hui You ◽  
Jun Hu ◽  
Lei Guo
Keyword(s):  
Crushed Rock ◽  
High Grade ◽  
Cooling Process ◽  
Convection Cooling ◽  
Permafrost Regions

Effect of Crushed Rock Layer Width on Natural Convection Cooling of Highway Embankment in Permafrost Regions

2012 ◽  
Vol 204-208 ◽  
pp. 1638-1643 ◽  
Author(s):  
Li Jun Yang ◽  
Bin Xiang Sun ◽  
Wei Wang ◽  
Qi Liu
Keyword(s):  
Natural Convection ◽  
Crushed Rock ◽  
Rock Layer ◽  
Layer Width ◽  
Variable Permeability ◽  
Cold Energy ◽  
Convection Cooling ◽  
Winter Time ◽  
Permafrost Regions ◽  
Highway Embankment

For the construction of the proposed Qinghai-Tibet Express Highway in permafrost regions, it will be necessary to use the new technique of cooling the ground temperature by the coarsely crushed rock layer with a low fines content. The heat convection governing equations based on airflow function in variable permeability porous crushed rock layer are derived. Comparison of the cooling capability of winter-time natural convection in the crushed rock highway embankments with various widths of crushed rock layer and an air-permeable side slope surface were studied using a finite element method. The result indicates that the cooling capability of natural convection within the crushed rock highway embankment with a crushed rock layer width of 12 m is stronger than that with a crushed rock layer width of 10 m. Under the same temperature and pressure boundaries, the storage of cold energy in the foundation soils below the wider crushed rock highway embankment due to natural convective heat transfer is larger than that below the narrower one.

Flow Channelization Method to Enhance Transformer Radiator Cooling Capacity

2018 ◽  
Vol 10 (6) ◽  
Author(s):  
Subhashish Dasgupta ◽  
Anurag Nandwana ◽  
K. Ravikumar
Keyword(s):  
Natural Convection ◽  
Heat Exchangers ◽  
Fluid Dynamic ◽  
Cost Effective ◽  
Cooling Capacity ◽  
Structural Features ◽  
Cfd Analysis ◽  
Cooling Process ◽  
Effective Technology ◽  
Convection Cooling

Abstract Most oil-cooled equipment like transformers are provided with radiators or heat exchangers, for the heated oil to exchange heat with the surrounding air by natural convection cooling, assisting the overall cooling process. While such radiators are effective accessories in controlling equipment temperature rise, it is ever desirable to further enhance the cooling capacity by design modifications or incorporating simplistic and cost-effective cooling technologies. In this study, computational fluid dynamic (CFD) analysis has been performed to evaluate the possibility of improving radiator performance by flow channelizing structures. Significant benefits (up to 17% increase in heat transfer coefficient) of imposing such structures, like a top chimney and an enclosure surrounding the radiator, were obtained. Although several past studies have confirmed that natural convection cooling effect can be intensified by flow channelization, the phenomenon is unique to a particular application. Given the wide variety in applications, in terms of shape, size, and structural features, it is necessary to study the effect in a given application of interest. This study points to a new direction in enhancing the cooling capacity of transformer radiators, inducing flow channelization, an easy-to-implement and cost-effective technology. Further, the study offers interesting learnings regarding flow channelization effects, which are invaluable guidelines for designers of future radiators.

The albedo of crushed-rock layers and its implication to cool roadbeds in permafrost regions

2016 ◽  
Vol 128 ◽  
pp. 32-37 ◽  
Author(s):  
Yinghong Qin ◽  
Kanghao Tan ◽  
Haifeng Yang ◽  
Fanghua Li
Keyword(s):  
Crushed Rock ◽  
Permafrost Regions

Effect of Vibrating Load on Grain Size Distribution of Crushed Rock Layer

2010 ◽  
Vol 168-170 ◽  
pp. 663-668
Author(s):  
Li Jun Yang ◽  
Wen Hui Bai ◽  
Bin Xiang Sun ◽  
Shuang Jie Wang ◽  
Jin Zhao Zhang
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Crushed Rock ◽  
Rock Layer ◽  
Fines Content ◽  
The Matrix ◽  
Study Laboratory ◽  
Permafrost Regions ◽  
Highway Embankment

For the construction of the proposed Qinghai-Tibet Express Highway in warm and ice-rich permafrost regions, it will be necessary to utilize the new technique of cooling the ground temperature by the coarsely crushed rock layer with a low fines content, instead of the traditional measures taken to increase simply thermal resistances, so as to protect from damage to highway embankment due to thaw settlement. The vibrating loads such as wheel load and tamping load may cause the breakage and abrasion of the matrix grains in the coarsely crushed rock layer. This results in decreasing of grain size and increasing of fines content in the crushed rock layer, thus decreasing the porosity of crushed rock layer. The smaller porosity of crushed rock layer may weaken the cooling effect of buoyancy-driven natural convection of the pore air in the crushed rock layer of the highway embankment, thus resulting in instability and failure of the embankment structure in permafrost regions. Under these conditions, the influence of vibrating load on the grain size distribution of the coarsely crushed rock layer has to be investigated experimentally. In the present study, laboratory experiments on the grain size variation of the coarsely crushed rock layer under vertically vibrating loads were carried out. The test results show that the vibrating load can cause the breakage and abrasion of the matrix grains in the coarsely crushed rock layer and the shapes of coarely crushed rock grain tend to be non-angular.

Countermeasures combined with thermosyphons against the thermal instability of high-grade highways in permafrost regions

2020 ◽  
Vol 153 ◽  
pp. 119047 ◽  
Author(s):  
Zhongrui Yan ◽  
Mingyi Zhang ◽  
Yuanming Lai ◽  
Wansheng Pei ◽  
Tao Luo ◽  
...  
Keyword(s):  
Thermal Instability ◽  
High Grade ◽  
Permafrost Regions

Effects of Framed Embankment for High-Grade Expressway in Permafrost Regions

2014 ◽  
Vol 505-506 ◽  
pp. 139-148 ◽  
Author(s):  
Wan Sheng Pei ◽  
Yuan Ming Lai ◽  
Ming Yi Zhang ◽  
Wen Bing Yu ◽  
Shuang Yang Li ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Thermal Stability ◽  
Global Warming ◽  
Scale Effects ◽  
Simulation Method ◽  
High Grade ◽  
Permafrost Table ◽  
The Difference ◽  
Thermal Stability Of ◽  
Permafrost Regions

Construction of high-grade highways is an important action to meet the requirement of communication and transportation in permafrost regions. Frame embankment is proposed to reduce the scale effects caused by wide pavement. Numerical simulation method is employed to analyze the improvement of frame embankment for thermal stability of roadbed, with the consideration of global warming. Compared the response of permafrost at symmetric position of each embankment to construction, the consistency degree of response is taken as decision fundament. Two indexes are selected, that is, the difference of permafrost table between the embankment and that at natural side, and the change of mean annual geothermal under the embankment. Additionally, the convenient for construction and wind-blown sand hazard are considered to determine reasonable frame space. So, numerical simulation of flow field of wind around embankments is carried out. It is concluded that the minimum space between two embankment is 6 m. The aim of this study is to provide scientific guidelines on construction of major permafrost engineering in the future.

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