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Injecting carbon dioxide is the most effective means of preventing and extinguishing fires in sealing hazardous areas, but the traditional method slowly and remotely injects carbon dioxide gas into the well after gasification on the ground, which is dependent on the complete mine pipe network without cooling effect. To inject liquid directly from the tank with vacuum interlayer and heat insulating powder for rapid inerting and cooling, a new approach using track mobile platform to go deep into the underground mine disaster area is proposed, so the liquid can be delivered to the nozzle at the end of DN40 large diameter pipe, and the continuous gasification jet can be realized. The experimental results show that: (1) The liquid volume in a tank of vacuum degree within 2.0 Pa and 200 mm interlayer reduced no more than 15.5% after 48 days; (2) Taking the pressure in the tank as the power source, because of environmental differences inside and outside the pipe after 100 m pressure holding delivery, the physical form of liquid and gas could be converted instantly; (3) The continuous discharge time without ice blocking for a tank full of 2 m3 liquid was about 10.5 min under 25 L dual mode nitrogen pressurization, which is 1/12 of injection time after ground gasification; (4) Based on the temperature decrease trend measured at different positions, the cooling characteristics on liquid gasification jet path are quantified, and the calculation formula of temperature changing with time on the center line of liquid gasification jet is obtained. Through this new approach, the integration of vacuum insulated storage, safe mobile transportation, and continuous and rapid release with large flow can be achieved for the liquid carbon dioxide.

Thermal performance of densely populated underground buildings is normally influenced by various factors, including the surrounding rock (SR), ventilation, and indoor heat sources. It is recognized that little experimental studies on thermal control for the above building was reported. In this article, a full-size 50-person mine refuge chamber (MRC) was newly constructed to test the thermal performance under natural convection and ventilation. The heat ducts were used to simulate the heat released from human body. Experimental results indicated that: (1) the intensity of the heat transfer between rock and air increases with the rise in heat source rate and ventilation temperature (VT), while it decreases as the initial surrounding rock temperature (ISRT) increases; (2) when considering the joint temperature control of pre-cooled SR, it is recommended to reduce the VT linearly during the evacuation period in order to ensure the thermal safety of personnel. During the non-refuge period, the cold amount should be stored as far as possible into the shallow SR body to make full use of it; (3) to ensure the thermal safety of an MRC with a capacity of 30 people for 96 h, cooling measures are required when the ISRT exceeds 21.3 °C. In addition, when the ISRT reaches 27.6 °C, the per capita ventilation is 0.19 m3/min, and the temperature is 26 °C, which can also meet the requirements. This study provides experimental verification as a basis for future research on underground space temperature control considering the influence of SR.

Toxic and harmful gases may follow evacuees into the mine refuge chamber, endangering their life during the mine disaster. Gases from the outside environment are successfully kept out of the mine refuge chamber by air curtains. The effect of the air curtain installation position, jet velocity, angle, and structural parameters on the CO barrier efficiency is studied using numerical simulation of computational fluid dynamics (CFD) in this paper. The results are also used to show the influence of the above factors on the efficiency of the air curtain. The results show that: (1) increasing the air curtain jet speed does not always increase or even decrease the air curtain barrier efficiency. (2) The best CO barrier efficiency of 68.1% was obtained by an air curtain installed on the top side of the refuge door with a velocity of 22 m/s and a jet angle of 10°. (3) A mathematical relationship between air curtain structural parameters and barrier efficiency is developed to provide a reference for the design of air curtain pipeline structures.

Air quality is a basic requirement for the survival of miners in distress while waiting for rescue in a MRC (mine refuge chamber). The use of air purifying devices is an effective supplement for removing harmful gas in a MRC. Scholars have paid much attention to the structure of air purifying devices and purifying agents for MRCs, but research on the number and layout of purifying devices in MRC has attracted little attention. To determine a reasonable number and layout of purifying devices in a MRC, theoretical analysis was conducted on the relationship between harmful gas concentration and the number, as well as the operating parameters, of devices in the chamber. A configuration calculation formula for purifying devices in MRCs was thus obtained. By conducting five experiments in a MRC with capacity of 50 people, the influence of the number and layout of purifying devices in the chamber, on the CO2 concentration distribution, was studied. The results show that, when the number of personnel is constant, the final concentration of harmful gas in the MRC is only related to the air volume from the air purifying devices and the efficiency of the air purifying devices. When using air purifying devices to remove CO2 in the MRC, the maximum CO2 concentration difference between different measuring points was less than 0.15%. With increasing number of purifying devices, the harmful gas concentration decreases, and the distribution of harmful gas is more uniform. When using two purifying devices, one at either end of the MRC, the harmful gas concentration was more uniform than when both devices were located in parallel at one end. [ABSTRACT FROM AUTHOR]

Air curtain systems for mine refuge chambers prevent harmful gases in the tunnel from entering the chambers, but their barrier efficiency is affected by their structural parameters, installation location and air flow angle as well as the size of the chamber door. Previous studies focused on air curtain systems installed on the top of the door frames of the mine rescue capsule, but no studies have investigated air curtain systems installed on two or three sides of the door frames. To improve the barrier efficiency of air curtain systems for refuge chambers, this study conducted an experimental investigation of the effects of the structural parameters, installation location, and air flow angle on the barrier efficiency for a constant size of the door frame. The results demonstrate that air curtain systems with air curtains installed on two sides of the door frame behind the door wall that ejected air parallel to the door frame provided a relatively good barrier effect; an air curtain system that used pipeline air curtains with a nozzle diameter of 1 mm and a nozzle distance of 15 mm exhibited a relatively good barrier effect and a barrier efficiency of 55-60%. In air curtain systems that use air knives, the air knife gap should be 0.1-0.2 mm wide. Under reasonable parameters and installation conditions, there was no significant difference between the barrier effects against CO2 of air curtain systems that use pipeline air curtains and those that use air knives. [ABSTRACT FROM AUTHOR]