文献类型：期刊文献

英文题名：Experimental study on cooling enhancement of crushed rock layer with perforated ventilation pipe under air-tight top surface

作者：Sun, Binxiang[1];Yang, Lijun[1];Liu, Qi[1];Wang, Wei[1];Xu, Xuezu[1]

机构：[1]Shaoxing Univ, Dept Civil Engn, Shaoxing 312000, Zhejiang, Peoples R China

年份：2011

卷号：68

期号：3

起止页码：150

外文期刊名：COLD REGIONS SCIENCE AND TECHNOLOGY

收录：SCI-EXPANDED(收录号：WOS:000295250700008)、、EI(收录号：20113214214484)、Scopus(收录号：2-s2.0-79961021937)、WOS

基金：This research was supported by the National Natural Science Foundation of China (grant no. 40772194 and no. 40972203). The support of the agency is gratefully acknowledged. We would like to express our gratitude to the editors and two anonymous reviewers for their constructive and helpful review comments.

语种：英文

外文关键词：Crushed rock layer; Perforated ventilation pipe; Air-tight surface; Heat transfer mechanism; Cooling capability

外文摘要：Under the warm and ice-rich nature of permafrost and the scenarios of climate warming on the Qinghai-Tibet Plateau, it will be necessary to use combinatorial techniques of cooling the ground temperature in the proposed Qinghai-Tibet Express Highway of construction. For the crushed rock highway embankment embedded a perforated ventilation pipe in permafrost regions of the Qinghai-Tibet Plateau, the mechanism of impact on the cooling capability enhanced by a perforated ventilation pipe in the air-tight crushed rock layer was studied using laboratory experiment. All boundary conditions at each edge of the crushed rock sample with dimensions of 100 x 60 x 100 cm except the inlet and outlet of the perforated pipe are air-tight. A ventilation steel pipe with an inner diameter of 8 cm was drilled with many small holes with a diameter of 1 cm and horizontally embedded in the length direction of the crushed rock sample with a depth of 53 cm. The laboratory experiments with a periodically fluctuating air temperature in the inner test tank regulated by program control were performed. The perforated pipe is only ventilated during the negative temperature fluctuation period in the inner test tank. The results show that the heat transfer processes in the crushed rock layer embedded a perforated ventilation pipe with an air-tight surface include pure heat conduction, forced convection that occurs in the crushed rock layer forming directly a pore air circulation in conjunction with the in-duct air by the small holes of perforated pipe wall absorbed from the inner test tank, and convective heat transport between the in-duct air and the inner surface of ventilation pipe wall. When air temperatures in the inner test tank are colder than the pore air temperatures in the crushed rock region around the perforated ventilation pipe, the perforated ventilation pipe can produce a significantly enhanced cooling of the crushed rock layer base due to the direct formation of a complete pore air circulation in the crushed rock layer in conjunction with the in-duct air via the small holes of the perforated pipe wall. When the fluctuating air temperature in the inner test tank rises from a minimum value to a warmer one than the pore air temperature in the crushed rock region around the perforated pipe during the negative temperature ventilating period, a warming process begins to occur in the crushed rock layer due to a warmer in-duct air absorbed from the inner test tank. This stronger warming process in the crushed rock region around the perforated pipe may decrease the cooling capability of the air-tight crushed rock layer. Thus, in order to avoid this warming process at this stage before ventilating end, the ventilating end time of ventilation pipe ought to be brought forward. (C) 2011 Elsevier B.V. All rights reserved.