Experimental study on cooling of deep mine stoping faces using detachable gas-liquid two-phase gravity heat pipes

With the increasing depth of coal mining, cooling excavation faces has become a critical engineering issue requiring urgent resolution. Traditional deep mine cooling methods are subject to limitations such as centralized cooling via air coolers or water spray cooling applied to intake airflow in mining roadways. The former suffers from significant cooling capacity attenuation over distance along with high energy consumption, while the latter deteriorates the working environment due to excessive water usage and increased roadway humidity. Based on the concept of localized underground cooling, a targeted cooling method utilizing the superior thermal conductivity of heat pipes is proposed. Through integration of the structural parameters of the roadway space at Wutongzhuang Coal Mine, a modular, detachable gas–liquid two-phase gravity heat pipe device with a height under 1.5 m was designed and successfully developed. By deploying its upper section directly at the air intake point of the excavation face with position adjustable in sync with mining progress, the problem of cooling capacity decay over transmission distance is effectively resolved. To investigate the heat transfer characteristics, an experimental platform was established using a heat pump system as the heat exchange unit. With operational parameters from Wutongzhuang Mine set as the baseline and the control variable method adopted as the core research strategy, the influences of ambient temperature, circulating water flow rate (3.0–3.5 m³/h), inlet/outlet air velocity (1.5–2.0 m/s), and tube row spacing (400–600 mm) on the system’s thermal performance were systematically examined. Experimental results show that under stable conditions of 32 °C air temperature and 60 % relative humidity, the outlet air temperature can be reduced by more than 5 °C, with single-tube heat transfer capacity reaching 400–450 W. An economic analysis conducted for a Wutong Mine section requiring 859  kW of cooling capacity indicates that, compared with existing air cooling equipment, the heat pipe system reduces investment costs by 1.97 million RMB and cuts carbon emissions by 1 620 t over a 15-year operational period. Consequently, an innovative solution for deep mine heat hazard management is delivered, characterized by efficient heat transfer, dynamic deployability, and near-zero operating energy consumption, while a theoretical basis is provided for the design and implementation of heat pipe cooling systems in Wutong Mine and similar mining operations.