Visualized study on the mechanism of temperature effect on coal during liquid nitrogen cold shock. (25th July 2021)

• Record Type: Journal Article
• Authors: Cong, Yuzhou; Zhai, Cheng; Sun, Yong; Xu, Jizhao; Tang, Wei; Zheng, Yangfeng
• Is Part Of: Applied thermal engineering. Volume 194(2021)
• Publication Date: 2021-07-25
• Subjects: Temperature effect -- Liquid nitrogen -- Strain field -- Thermal stress; Heat engineering -- Periodicals; Heating -- Equipment and supplies -- Periodicals; Periodicals; 621.40205
• DOI: 10.1016/j.applthermaleng.2021.116988
• Languages: English
• ISSNs: 1359-4311

Abstract

Highlights: Analysis of temperature effect combined with temperature field and strain field. The range and thermal stress of liquid nitrogen cold shock are obtained. Visualize the local stress concentration caused by the temperature effect of liquid nitrogen. Abstract: This study is aimed to investigate the mechanism of temperature effect on coal during cold shock resulting from anhydrous low-temperature liquid nitrogen, which is a key issue in the application of liquid nitrogen in coalbed methane exploitation engineering. In this study, the temperature and strain distributions of coal around the drill hole during liquid nitrogen cold shock (LNCS) in an open environment were analyzed by using an infrared measurement device, thermocouples and a digital image correlation (DIC) full-field strain measurement system. The following beneficial results were obtained. With respect to the temperature field, the low-temperature zone of coal around the drill hole keeps expanding in a semicircular shape at a decelerated rate. An obvious temperature gradient exists. The position closer to the drill hole corresponds to a lower temperature and a larger temperature difference under the condition of equal spacing. The strain field around the drill hole is unevenly distributed. The strain experiences two stages in turn, namely short-term frost heave and long-term frost contraction. A strain-concentrated area exists in the vicinity of the drill hole. This area is dominated by the frost contraction strain which is distributed in a circular shape. Finally, a hierarchical model for thermal stress calculation was established. Through a combination of the model and the strain field, the variations of the radial thermal stress based on temperature difference and the radial thermal stress based on strain, as well as their distribution functions at 30 min of LNCS were concluded.