Search Results (31)

As mine mining extends to greater depths, the challenge of heat damage in high-temperature and high-humidity deep mines has emerged as a significant obstacle to the safe mining of deep mines. This paper reviews the causes of mine heat damage, evaluates heat damage mechanisms, and explores deep mine cooling technologies. Traditional deep mine cooling technologies employ mechanical refrigeration to cool air. While these technologies can mitigate heat damage, they are associated with issues including high energy consumption, insufficient dehumidification, and significant cold loss. To address the high energy consumption and fully utilize geothermal resources, heat pump technology and combined cooling, heating, and power technology are employed to recover waste heat from deep mines, thereby achieving efficient mine cooling and energy utilization. To enhance the effectiveness of air dehumidification, the integration of deep dehumidification with mine cooling technology addresses the high humidity ratio in mine working faces. To enhance the refrigeration capacity of the system, liquid-phase-change refrigeration technology is employed to boost the refrigeration capacity. For the future development of deep mine cooling technology, this paper identifies four key directions: the integration of diverse technologies, collaboration cooling and geothermal mining, deep dehumidification and cooling, and intelligent control. Full article

As global mineral resources at shallow depths continue to deplete, thermal hazards have emerged as a critical challenge in deep mining operations. Conventional localized cooling systems suffer from a fundamental inefficiency where their cooling capacity is rapidly dissipated by the main ventilation airstream. This study introduces the innovative concept of a “microclimatic circulation zone” implemented through a convection–radiation cooling system. The design incorporates a synergistic arrangement of dual fans and flow-guiding baffles that creates a semi-enclosed air circulation field surrounding the modular convection–radiation cooling apparatus, effectively preventing cooling capacity loss to the primary ventilation flow. The research develops comprehensive theoretical models characterizing both internal and external heat transfer mechanisms of the modular convection–radiation cooling system. Using Fluent computational fluid dynamics software, we constructed an integrated heat–moisture–flow coupled numerical model that identified optimal operating parameters: refrigerant velocity of 0.2 m/s, inlet airflow velocity of 0.45 m/s, and outlet aperture height of 70 mm. Performance evaluation conducted at a mining operation in Yunnan Province utilized the Wet Bulb Globe Temperature (WBGT) index as the assessment criterion. Results demonstrate that the enhanced microclimatic circulation system exhibits superior cooling retention capabilities, with a 19.83% increase in refrigeration power and merely 3% cooling capacity dissipation at a 7 m distance, compared to 19.23% in the conventional system. Thermal field analysis confirms that the improved configuration successfully establishes a stable microclimatic circulation zone with significantly more concentrated low-temperature regions. This effectively addresses the principal limitation of conventional systems where conditioned air is readily dispersed by the main ventilation current. The approach presented offers a novel technological pathway for localized thermal environment management in deep mining operations affected by heat stress conditions. Full article

As the core equipment in ship power systems, the accurate and real-time diagnosis of ship diesel engine faults directly affects navigation safety and operation efficiency. Existing methods (e.g., expert systems, traditional machine learning) can hardly cope with the complex failure modes and dynamic operation environment due to the problems of relying on artificial features and insufficient generalization ability. In this paper, we propose a BiLSTM-CRF-based knowledge graph construction method for ship diesel engine faults, aiming at integrating multi-source heterogeneous data through deep learning and knowledge graph technology, and mining the deep semantic associations among fault phenomena, causes, and solutions. The research framework covers data acquisition, ontology modeling, and knowledge extraction and storage, and the BiLSTM-CRF model is used to fuse bi-directional contextual features with label transfer probability to achieve high-precision entity recognition and relationship extraction. Finally, a scalable knowledge graph is constructed by Neo4j. Experiments show that the model significantly outperforms baseline methods such as HMM, CRF, and BiLSTM, and the graph visualization clearly presents the fault causality network, which supports knowledge reasoning and decision optimization. For example, “high exhaust temperature” can be related to potential causes such as “turbine failure” and “poor cooling”, and recommended measures can be taken. This method not only improves fault diagnosis accuracy and efficiency but also provides a novel method for intelligent ship health management. Full article

As mining operations extend to greater depths, they encounter critical challenges, including increased distances and substantial energy losses. To address the challenges of cold-energy loss in deep mine cooling systems and improve the working environment for miners, a long-distance sleeve-type insulated pipe system was developed. This system aims to mitigate thermal energy loss caused by heat transfer between the pipe and surrounding soil throughout the water transport path from the source to the deep mine in boreholes. A heat transfer analysis model was developed to assess the impact of variables such as transport time, water flow rate, inlet temperature, and insulation materials on the temperature of cold water. The study reveals that the temperature of cold water increases rapidly during transportation before reaching a stable state. Implementing modifications such as increasing the inlet temperature, enhancing the water flow rate, or utilizing materials with lower thermal conductivity can effectively mitigate temperature rises. Additionally, the novel sleeve-type design enhanced the pipe’s pressure-bearing capacity, reduced the required pipe length by 4752 m and minimized energy loss compared to traditional systems. In practical applications, after 45 h, the supply and return water temperatures increased by 0.45 °C and 0.38 °C, respectively, while maintaining cooling energy loss below 12%. This innovative solution improves mine cooling efficiency and provides guidance to reduce cold-energy loss. Full article

In this study, a split Hopkinson pressure bar (SHPB) test system with real-time temperature control was developed, and dynamic tests on limestone taken from deep coal mines within real-time temperatures of 25 to 800 °C were carried out. Additionally, the scanning electron microscope (SEM), X-ray diffraction (XRD), and energy dispersion spectrum (EDS) tests were conducted to analyze the fracture mechanism of limestone at real-time temperatures. The results reveal that the dynamic compressive strength of limestone linearly declines with increasing temperatures; due to not being affected by thermal shock damage, its strength degradation is not significant after cooling to room temperature, whereas the dynamic elastic modulus exhibits a negative exponential nonlinear decrease with the increase in temperatures. The average strain rate has a positive correlation with the dynamic compressive strength of limestone, while the dynamic elastic modulus exhibits variations in accordance with the Boltzmann function and its relationship with the strain rate. The combined influence of strain rate and temperature on the dynamic compressive strength of limestone can be accurately described by a binary quadratic function. The mechanism of real-time action on limestone can be divided into three stages: when the temperature is between 25 and 200 °C, crystal micro-expansion leads to the densification of micropores, which leads to the increase in limestone strength. When the temperature is between 200 °C and 600 °C, the formation of microcracks induced by thermal stress and intergranular expansion results in a reduction in limestone strength. When the temperature is between 600 and 800 °C, in addition to the continued expansion of the intergranular resulting in the increase in the number of micro-cracks, the decomposition of dolomite at high temperatures leads to chemical deterioration and further reduction in the strength of limestone. Full article

With the increasing depletion of shallow resources, mining has gradually shifted to deeper levels, and the high-temperature problem of deep mining has restricted the efficient and safe development of mining. In this study, five types of thermal insulation materials for surrounding rocks with different ratios were produced using tailings, P.O.32.5 clinker, aluminum powder, glass beads, quick lime, and slaked lime as test materials. Based on the uniaxial compression test, the thermal constant analysis test, and numerical simulation analysis technology, the change rule of mortar compressive strength and thermal conductivity was analyzed, and the cooling effect of surrounding-rock thermal insulation materials with different ratios was discussed. The results showed that the compressive strength of the surrounding-rock thermal insulation materials ranged from 0.39 to 0.53 MPa, and the thermal conductivity ranged from 0.261 to 0.387 W/(K·m), with the compressive strength of ratio E being the largest and the thermal conductivity of ratio A being the lowest. In the numerical simulation analysis results, the thermal insulation layer thickness was taken as a value of 10 cm when, at this time, the best thermal insulation effect and economic benefits involved a temperature reduction of 0.9 K. In the case of changing the thermal conductivity and inlet wind speed, the original temperature of the rock temperature reduction was also very clear, with maximum reductions of 0.92 K, 0.92 K, and 1.42 K. Full article

With the continuous development of the mining industry and advancements in deep mining technology, mine environment optimization has become key to ensuring safety and improving the efficiency of mining. The high-temperature environment, particularly in deep mines, not only poses a serious threat to miners’ health but also significantly reduces operational efficiency. These issues have been determined based on the current application status and development trends of mine cooling technology, including traditional mechanical and non-mechanical cooling technologies, as well as emerging roadway insulation materials and mine cooling clothing applications. By comparing the advantages and disadvantages of each technology, the main challenges related to the use of current mine cooling technologies are pointed out, including the low energy efficiency ratio, high cost, and difficult implementation. Finally, this paper looks forward to the future development directions of mine cooling technologies, emphasizing the importance of intelligent, energy-saving, and environment-improving comprehensive system management and, in turn, promoting the progress and application of mine environment optimization technology and supporting safe and efficient deep mining. Full article

In accordance with the programme of closure works and the implementation of ecological spatial rehabilitation in the area of the Slovenian coal mine Trbovlje–Hrastnik (RTH), there is a great opportunity to exploit shallow geothermal energy from water and ground sources. In the RTH area, there is great energy potential in the utilisation of underground water and heat from the earth. In our research, we have focussed on the use of geothermal energy with heat pumps from groundwater (water/water system) and from ground collectors and wells up to a depth of 150 m (rock/water system). With the water/water system, we have an average of 2.7 MW of thermal energy available, with the rock/water system having 7.5 kW of thermal energy from a 150 m deep well. With the rock/water system in particular, the development of an industrial zone in the RTH area can also provide for a greater demand for thermal energy. The thermal energy obtained in this way is utilised via heat pumps to heat and cool commercial, residential and industrial buildings. The utilisation of shallow geothermal energy can make a major contribution to carbon neutrality, as the use of geothermal energy has no negative impact on the environment and causes no greenhouse gas emissions. The aim of the paper is to provide an overview of the methods used to analyse heat storage in aquifers of abandoned coal mines, to represent these storages in RTH with a basic mathematical–statistical inventory of what is happening in the aquifer, and to investigate the possibility of using shallow geothermal energy with the help of modelling the use of shallow geothermal energy. The results and analyses obtained can make an important scientific contribution to the use of geothermal energy from abandoned and closed mines. Full article

A high temperature is the key factor limiting the safe development of deep mine tunnels. By confronting the phenomenon of serious heat exchange between airflow and the surrounding rocks in the tunnel excavation area, a conceptual model of coupled cooling of auxiliary ventilation and partial thermal insulation is proposed. The performance of a coupled cooling system was investigated and optimized by using the scale model test with a 1:10 geometric scale and the orthogonal test. The results suggest that the average temperatures of the work zone and its central point decrease by 1.5 °C and 3.3 °C, respectively, while partial insulation layers are used. According to the sensitivity analysis for a single factor, as the ventilation duct outlet (VDO) moves away from the working face (WF), the temperature gradually increases, leading to a local high temperature area. When the ventilation duct height is arranged in the middle of the insulation layer, the cooling effect is optimal and the highest average temperature difference is 4.4 °C. The thermal equilibrium temperature can be further decreased by lengthening and thickening the insulation layer. In addition, the range analysis shows that the ventilation velocity has a greater impact on the thermal environment of the tunnel working area than the ventilation duct location and insulation layer length. The coupled cooling method can save on cooling capacity and effectively alleviate the high-temperature problems of the tunnel excavation area. Full article

Mine heat hazards have resulted in large amounts of high-quality coal resources in deep that cannot be mined. The mining industry is paying more and more attention to the extraction and utilization of geothermal energy in mines, while at the same time reducing the underground temperature to realize co-extraction of coal and heat. In addition, coal mines tend to burn large amounts of coal to heat mine buildings and provide hot water for workers’ daily baths, creating operating costs and increasing greenhouse gas emissions. Therefore, it is of great significance to investigate the feasibility of extracting geothermal energy to provide the daily heat load for mines. Currently, there is little research on the feasibility of geothermal energy extraction and utilization in productive mines instead of abandoned mines. In this study, according to the actual situation of Xinhu mine in eastern China, a combined geothermal water system and heat-pump heating system is proposed, aiming to effectively realize mine cooling and geothermal exploitation and utilization. The geothermal storage capacity in the area is analyzed, and an economic analysis is developed. The economic analysis indicates that the main factors affecting the feasibility of the system are the number of mine users, the distance from the geothermal production well to the mine buildings, and the coal price. The research shows that the economic efficiency of the system is better when the heating scale is larger and the distance is smaller. As coal prices rise, the combined geothermal water and heat-pump heating system will be more economical than traditional coal heating. If a mine has 2000 workers, the application of this system can prevent 334.584 t of CO₂ emissions per year. Full article

With the rapid progress in data mining, deep learning, and artificial intelligence, the demand for datacenters of various sizes increases globally. Datacenters typically require an environment with properly controlled temperature and humidity conditions for their proper operations. These needed environmental conditions are always provided by an air conditioning system. In humid and hot regions, both energy consumption and the splash of water condensate in using the fin-and-tube heat exchangers are of concern because reliability issues can occur. In this study, the effects of fin surface hydrophilic/hydrophobic coatings on the performance of the fin-and-tube heat exchangers, including the heat transfer rate, pressure drop, and water-condensate splash, were investigated experimentally. By varying the cooling air speeds and fin pitches, the results show that hydrophilic surface coating is an effective method in reducing both the pressure drop (thus saving energy) and the condensate splash, while not affecting the heat transfer rates significantly. The water splash reduction is achieved by both the increased air speed for splashing and a smaller amount of splashing. Water splash can even be completely eliminated if the airspeed was below about 3 m/s. In contrast, hydrophobic surface coating will increase both pressure drop and water splash; thus, should be applied with caution. Full article

With the increasing depth of metal mining, thermal damage has become a serious problem that restricts mining. The thermal management system of refrigeration and ventilation is an indispensable technology in the mining of deep metal mines, which plays a key role in improving the thermal and humid environment of mines. Optimizing the performance of refrigeration and ventilation systems to reduce energy consumption has become a focus of researchers’ attention. Based on the heat current method, this research establishes the overall heat transfer and flow constraint model of the refrigeration and ventilation system, and proposes an iterative algorithm that combines the refrigerator energy consumption model and the artificial neural network model of heat exchangers. The Lagrange multiplier method is used to optimize the system with the goal of minimizing the total power consumption of the system. The results show that under 9.1 kW cooling load conditions, the total energy consumption of the system reduces by 16.5%, and the COP of the refrigerator increases by 11.6%. The optimization results provide significant guidance for the production and energy consumption reduction of the deep metal mines. Full article

Significant harm from heat has become a key restriction for deep metal mining with increasing mining depth. This paper proposes a refrigeration ventilation system for deep metal mines combined with an existing air cycling system and builds an experimental platform with six stope simulation boxes. Using the heat current method and the driving-resistance balance relationship, the heat transfer and flow constraints of the system were constructed. An artificial neural network was used to establish models of heat exchangers and refrigerators with historical experimental data. Combining the models of the system and stope simulation box, an algorithm that iterates the water outlet temperature of the evaporator and condenser of the refrigerator was proposed to design the coupled simulation model. The heat balance analysis and comparison of the air outlet temperatures of the stope, as well as the heat transfer rates of the heat exchangers with the experimental data, validated the coupled simulation model. Additionally, the effects of cooling fans and the air inlet temperature of the cooling tower were discussed, which provided a powerful modelling method for the coupled model of a refrigeration ventilation system, helps to reduce energy consumption, and improves the sustainability of mining production. Full article

Mechanical cooling of the entire mining tunnel, widely used in deep coal mines, has a significant energy-intensive consumption, particularly for intelligent mining tunnels. Therefore, localized cooling would benefit the intelligent mining industry. Current studies on the temperature, relative humidity, and air velocity under localized cooling for working protection are still unclear. A modified predicted heat strain model that is appropriate for warm and humid conditions is presented in this article and calculated using MATLAB. Results reveal that air temperature was the primary factor affecting underground miners’ safety. Increasing air velocity would improve the working environment when the thermal humidity index is lower than 32. Reducing total working time and wet bulb temperature would benefit underground miners’ security. For the cooling of intelligent mining tunnels, the recommended air velocity would be 2 m/s, and the maximum wet bulb temperature would be 28 °C for the 6-h working period and 26 °C for the 8-h working period. Results would be beneficial to the cooling of intelligent mining in China. Full article

Heat stress in deep hot mines is a factor that often determines the possibility of technical mining of natural resources. One of the solutions enabling miners to work in such mines is air cooling. Cooling systems vary, and their selection depends on the type of mine and the mining methods used. Limited air cooling capabilities exist in electric-powered coal mines. The main solution for air cooling is based on movable spot air coolers. Such systems commonly use surface or underground refrigeration plants. An underground refrigeration plant (URP) equipped with compressor chillers does not achieve more than 2.5–3.0 MW of cooling capacity due to the limited heat rejection capacity of return air streams in a typical coal mine. The method discussed in this paper, using mine water to discharge waste heat from the underground refrigeration plant, provides a measurable benefit for optimizing the mine air cooling system. The main purpose of this research is to study the feasibility and effect of water diversion from the actual mine drainage system to the underground refrigeration plant. The water drainage system in an underground mine is called the dewatering system of the mine. The heated water in the condensers of the chillers is directed back to the mine’s central dewatering system. The recovery from water discharged to the surface contributes to optimising energy consumption for a mine air cooling and the sustainable discharge of wastewater. In addition, using the total water flow from the mine dewatering system to reject heat in compressor chillers, compared with the traditional solution, can improve the cooling capacity of URP. These findings may provide beneficial guidance for practical applications in deep hot mines with small natural water inflow. Full article