An Experimental Study on the Heat and Mass Transfer of Liquid Nitrogen in a Loose Medium

Yang Zhang, Baiwei Lei, Bing Wu, Yu Meng and Binbin He
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Yang Zhang: School of Emergency Management and Safety Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
Baiwei Lei: School of Emergency Management and Safety Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
Bing Wu: School of Emergency Management and Safety Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
Yu Meng: School of Emergency Management and Safety Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
Binbin He: School of Emergency Management and Safety Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China

Energies, 2019, vol. 12, issue 18, 1-17

Abstract: Liquid nitrogen is a vital medium during the extinguishing and chilldown process of coal spontaneous combustion in coal mine goafs. In this paper, the heat and mass transfer of liquid nitrogen in a loose medium was investigated. A laboratory system including a temperature sensing system was designed and built to explore the effects of different nitrogen injection positions and angles on the chilldown effect. The results indicate that after liquid nitrogen injection, the temperatures in the liquid nitrogen flow area and the bottom of the model can be quickly reduced to −196 °C, which was the best chilldown effect zone. With the vaporization of the liquid nitrogen, the cryogenic nitrogen gradually diffused. At 20,000 s, the bottom temperature was about –63 °C, the middle was –30 °C, and the upper was 0 °C. When the model angle was 0°, the effective chilldown zone was the largest. As the angle increased, the effective chilldown volume and holding time decreased significantly. The model angle had a greater impact on the chilldown. For the position of nitrogen injection, the inlet was set slightly farther from the gas outlet’s position, leading to a larger coverage for the liquid nitrogen and cryogenic nitrogen chilldown. This study can provide a theoretical basis for the flow and chilldown of nitrogen injection in goafs.

Keywords: liquid nitrogen; cryogenic; gravity sedimentation; effective chilldown zone; Leidenfrost effect (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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