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The complex hydrogeological conditions in karst areas complicate the heat transfer mechanisms in buried pipe heat exchangers. This study examines the impact of geological factors on heat exchanger performance and the temperature field of rock-soil mass (RSM). Five factors—flow direction and velocity of seepage (FDS and FVS), thickness of seepage layer (TSL), porosity of rock-soil mass (PRS), and inlet temperature (INT)—and four levels are selected. Using L16(45) orthogonal experiments, three performance indexes are evaluated: temperature difference between inlet and outlet (TDIO), heat exchange decay rate (HEDR), and thermal stacking rate (TSR). The GCGA algorithm scores each index comprehensively. Results show: (1) TDIO and TSR increase with INT; seepage benefits enhance heat transfer temperature difference by 14.2 % under the same INT; Higher TSL leads to a maximum TSR decrease of 33.01 % in the seepage zone's upper reaches under the same INT. (2) Increased seepage thickness amplifies its impact on heat transfer decay rate. (3) Key factors for TDIO, HEDR, and TSR are INT, TSL, and INT, respectively. These research findings can guide the design of GSHPs in regions with different hydrogeological conditions, based on the premise of enhancing the efficiency and operation duration of the system under continuous operation, thereby promoting the application of GSHPs. [ABSTRACT FROM AUTHOR]

The rapid development of the internet era has driven the construction of numerous data centers worldwide. In hot climate, data centers consume significant energy for cooling. Cold-mist direct evaporative cooling offers a natural cooling solution that can help reduce this energy consumption. This study investigates the temperature and relative humidity changes of natural high-temperature air after being cooled using a cold-mist direct evaporative cooling test bench. The effects of several control factors such as spray angle, spray flow rate, and air speed on the cold-mist direct evaporative cooling performance was systematically examined. The findings revealed that: (1) the optimal spray angle for cold-mist direct evaporative cooling treatment air is 65°; (2) high-temperature air between 27 °C and 37 °C can be cooled to 23.57 °C – 25.58 °C after cold-mist direct evaporative cooling treatment, with relative humidity levels of 67.0 % – 78.8 %, meeting the air supply requirements for data centers; (3) the proposed approach could reduce the data center energy consumption by 14 % – 41 %, while extending the annual natural cooling period by 3.16 % – 20.45 %. [ABSTRACT FROM AUTHOR]

With the cold-fog direct evaporative cooling (CDEC) technology, which uses the natural cooling sources, the cooling energy consumption of data centers can be reduced, and thus the cooling cost can be decreased significantly. There are only a few studies on the application of CDEC in data centers. In this paper, CDEC technology is proposed to provide cooling sources for a data center after cooling the high-temperature fresh air and circulated air from the data center. According to the results of experiments, it can be concluded that only when the relative humidity of high-temperature fresh air is lower than 40 %, the treated air meets the air supply requirements of the data center. otherwise, the circulated air need be treated by CDEC in order to ensure that the air temperature can be reduced to below 30 °C and the relative humidity be less than 80 %. Compared with general evaporative cooling, the efficiency can be improved by 2.07 %–28.50 % with CDEC. Besides, according to the orthogonal experiment, the sequence of various influencing factors on the CDEC is: air speed > spray flow rate > spray angle, which provides guidance for the optimization of application of CDEC in data centers. • Applying cold-fog direct evaporative cooling (CDEC) technology to data centers. • A cooling scheme for data center under a high-temperature climate is proposed. • FDEC can improve the utilization of natural cold sources in data centers. • FDEC is 2.07 %–28.5 % more efficient than general evaporative cooling. • This contributes to achieving free cooling for data centers throughout one year. [ABSTRACT FROM AUTHOR]

• Research on ground source heat pump horizontal headers based on similarity principle. • The orthogonal test was designed and the sandbox test-bed was built. • Study the influence of multiple factors on ground source heat pump horizontal headers. • Study the effect of horizontal headers on the U-tube heat exchange. • Optimization methods for temperature control of horizontal headers are proposed and guiding practical projects through range analysis. The energy loss of ground source heat pump horizontal headers cannot be ignored. Based on the similarity theory and the principle of the orthogonal test, a sandbox experiment platform was built to study the temperature change rule of the horizontal header under the action of multiple factors and the influence of the temperature change on the U-tube heat exchange capacity. The results show that: (1) The influence degree of each factor on the horizontal header is as follows: buried depth > surface temperature > covering material > flow in the pipe; (2) Under the two extreme conditions, the temperature rise difference of the horizontal header water supply section is 0.25 ℃ and that of the return section is 0.29 ℃, the heat transfer difference of the water supply section is 91 W and that of the return section is 105 W and the heat exchange difference of the U-tube is 38.5 W; (3) The temperature rise in the return section of the horizontal header causes the loss of cold in the pipe, but the temperature rise in the water supply section promotes the heat exchange of the U-tube. Finally, the optimization methods and construction recommendations are put forward. [ABSTRACT FROM AUTHOR]

Air quality and thermal environment of mine refuge chamber (MRC) are very important to determine the physical safety of refugees. Accurately assessing the environmental load and taking reasonable measures are critical to achieve the environmental control goals of MRC. In order to evaluate the metabolic parameters of occupants and the effectiveness of environmental control measures in a MRC, in this research, 50 adult men entered a MRC laboratory for an 8-h test. During the test, the compressed O 2 cylinders and air purification devices were used to ensure the indoor air quality. The possibility of using chemical adsorbents to passively scrub CO 2 and the performance of dehumidification by mine compressed air (MCA) were also investigated by simulation experiments. The results indicated that: (1) The per capita metabolic rates of O 2 , CO 2 and heat during the refuge process are 0.34–0.37 L/min, 0.34 L/min and 117–128 W, respectively. (2) When Ca(OH) 2 particles are used as CO 2 adsorbent, the air purification device has both dehumidification and CO 2 scrubbing functions, and three air purification devices could make the CO 2 concentration below 0.8% with the relative humidity below 76%. When Ca(OH) 2 particles are packaged to passively scrub CO 2 , the amount of adsorbent may increase significantly. (3) When MCA is used for dehumidification in a MRC, the air volume of 0.15 m3/min per capita could maintain the relative humidity close to 60%. (4) In the early stage of disaster avoidance, the indoor ambient temperature rises rapidly within 1 h followed by a slight increase. • A large-scale comprehensive environmental experiment with 50 people has been carried out. • Main metabolic parameters of occupants in a MRC, including CO 2 , O 2 and heat are 0.34–0.37 L/min, 0.34 L/min and 117–128 W, respectively. • Three purification devices used in a 50-person MRC can maintain CO 2 concentration below 0.8% and below 76% RH. • Passive scrubbing CO 2 will significantly increase the amount of CO 2 adsorbent. • Air volume of 0.15 m3/min per capita can maintain the relative humidity close to 60%. [ABSTRACT FROM AUTHOR]

To address the challenges of prolonged cooling air supply for data centers (DCs) in high-temperature climates, a cooling ventilation system combining evaporative cooling with phase change energy storage (PCES) under natural air cooling is proposed. Based on the summer high-temperature meteorological conditions in Gui'an New District, Guizhou Province, China, experiments were conducted using single-factor impact analysis and orthogonal experiments. These experiments investigated the effects of several control parameters such as inlet air temperature, inlet speed, inlet humidity, and spray flow on the cooling performance of the integrated cooling device, confirming the feasibility and high efficiency of this technology for green DCs. The results indicate that: (1) After being treated for temperature and humidity through the spray and the phase change plate (PCP) at both ends, the air temperature can be lowered by about 7 °C on average, and the relative humidity can be reduced by about 35 % over an 8-h period. (2) The temperature difference between inlet and outlet increases with the increase of inlet air temperature and spray flow but decreases with the increase of inlet air speed and inlet air humidity. (3) Through orthogonal experiments, the major and minor factors affecting the cooling performance, in order of significance, are inlet air temperature > inlet speed > spray flow > inlet humidity. [ABSTRACT FROM AUTHOR]

• The advantages of compressed air coupled PCP cooling compared with compressed air cooling and PCP cooling are summarized. • The greater the heating power, the more difficult it is to control the ambient temperature of the chamber, and the larger the pressure air volume, the easier it is to control the ambient temperature of the chamber, but the temperature distribution will be uneven. • The arrangement of three rows contrasts the two rows and four rows to keep the chamber at the right temperature for a longer time. • The application of compressed air coupled PCP in the refuge chamber is optimized. Controlling the temperature is a prerequisite for ensuring the safety of evacuees in underground refuge chamber. Previous studies have only studied the use of pressurized air or phase change for temperature control in underground refuge chambers. Moreover, there are limitations to the application of the two cooling methods. Therefore, in this paper, the temperature control method of compressed-air coupling phase change is studied, and its application in underground refuge chambers is expanded. This article experimentally studied the temperature control characteristics of the three temperature control methods, namely compressed air, phase transition, and compressed air coupling phase transition, and the effects of heating rate, compressed air volume and arrangement on the application of compressed air coupled phase change in underground refuge chambers were studied by control variable method. The results show that: (1) The temperature difference between the compressed air coupled phase transition and the compressed air is nearly 2.5 °C lower than that of the phase change plate, and the compressed air and temperature rise rate is similar to that of the compressed air coupled phase change, with a difference of only 0.02 °C/h, but the compressed air coupled phase change has a lower head and foot temperature difference. (2) When the compressed air volume is 360 m3/h, the cooling effect of the compressed air coupling phase change is better, but the indoor temperature distribution is uneven due to the large wind speed. (3) The smaller the number of people, the easier it is to control the internal temperature of the chamber, and the more difficult it is to control the larger the number of people. (4) Among the arrangement of two rows, three rows and four rows, the three-row arrangement is more suitable for the underground refuge chamber. [ABSTRACT FROM AUTHOR]

[Display omitted] • Newly verify that the feasibility of SRLP for the REE recovery from florencite. • Highly efficient recovery of REE from sedimentary rare earth ores was achieved. • It was determined that roasting can convert florencite to soluble REE by H 2 SO 4. Simultaneous recovery of lanthanum (La), cerium (Ce), and niobium (Nd) from sedimentary rare earth ores (SREO) has been carried out by a hydrometallurgical process using a sulfation roasting - leaching process (SRLP). Response surface methodology (RSM) was used to optimize the process parameters. The optimum condition for rare earth elements (REE) recovery was determined to be roasting temperature 700 °C, roasting liquid/solid ratio (L/S) 1.35 mL/g, roasting time 15 min, leaching temperature 90 °C, leaching L/S 20 mL/g, and leaching time 4.24 h. The maximum predicted recoveries for La, Ce, and Nd were 80.93 %, 74.48 %, and 97.49 %, respectively. The leaching verification experiments showed that the % leaching under the optimal conditions were La 88.02 %, Ce 78.87 %, and Nd 89.75 %, respectively. The % leaching relative deviation between the experimental and predicted values was less than 10 %, confirming the reliability of the experiments. Mechanism analysis shows that after SRLP, the florencite and kaolinite in SREO are more likely to be selectively converted to aqueous solution by H 2 SO 4 , thus achieving the separation of La, Ce, and Nd from SREO. This provides a valuable reference for the recovery of REE from florencite-base rare earth ore. [ABSTRACT FROM AUTHOR]

Related research on refrigerant optimization based on the dynamic BOG has yet to be proposed. This study offers a new dynamic optimization method for boil-off gas (BOG) re-liquefaction system to improve the system's energy efficiency. The performance of C3MR (the propane precooling mixed refrigerant cycle) is analyzed based on the steady state model of leading liquefaction equipment in the process simulation in Aspen HYSYS software. And the principle of the energy consumption variation law of propane precooled compressor and mixed refrigerant compressor, based on the actual possible disturbance range obtained in the natural gas liquefaction process, is applied to construct the multi-objective optimization model with minimum energy consumption and maximum heat exchanger efficiency. Finally, the dynamic responses of disturbances were achieved and discussed with the aid of GA (Genetic Algorithm) and PSO (particle swarm optimization). The optimized performance of the dynamic liquefaction cycle is 34.8% better than the steady condition system in terms of energy efficiency, and the maximum energy consumption can be reduced by 50.60%. The advantage of the proposed optimization framework is its adaptability to other dynamic liquefaction processes. It has practical reference significance for the cost control of the BOG re-liquefaction recovery project. • A new dynamic optimization method for C3MR liquefaction. • A multi-objective optimization model with minimal energy consumption and high thermal efficiency is constructed. • Provides a theoretical basis for the optimization of dynamic liquefaction systems. [ABSTRACT FROM AUTHOR]

• The structure of the mine ice storage cooling device (ISCD) has been optimized. • The transient temperature distribution and the evolution of the solid-liquid interface are studied. • The ISCD has the optimal heat transfer performance when the number of fins is eight. • The melting time is of ice shortened by 18.8 % compared with the ISCD without fins. The thermal performance of the ice-storage cooling device used in the underground mine refuge chamber is poor, which causes a waste of energy. Therefore, it is necessary to improve the heat transfer performance of ice latent heat storage devices. In the current work, the effects of fin height, fin thickness and number of fins on the heat transfer performance of the ice based latent heat energy storage device were numerically analyzed. The results show that: (i) when the number of fins is 8, the heat exchange characteristics of the ice-storage device reaches the best performance; (ii) increasing the number of fins and the height of the fins can increase the heat exchange area and improve the heat exchange performance; (iii) compared with the ice-storage device without fins, the cooling efficiency of the ice-storage device increased by 34.12 % and the melting rate increased by 9.3 % after the addition of fins. The addition of fins can improve the heat exchange efficiency of the ice-storage device, while promote the application of phase change energy storage technology in underground mine refuge chambers. [ABSTRACT FROM AUTHOR]

Temperature and humidity control in underground refuge chamber is an important issue in the case of power failure after a disaster. In this article, an ice storage air conditioner was newly developed for refuge chambers. A series of tests were conducted to investigate the ice storage, cooling, and dehumidification performance of the air conditioner. In addition, based on the orthogonal experimental principle, the effect of the key inlet air parameters such as speed, temperature and relative humidity on the cooling and dehumidification performance was analyzed in a systematic manner. Results show that: (i) the ice storage function could be completed by freezing the ice to below −15 °C within 60 h. After testing for 96 h, the outlet air temperature of the ice storage air conditioner is less than 23 °C; (ii) the effect of the inlet air parameters on the cooling and dehumidification performance could be found as velocity > temperature > relative humidity; (iii) the dehumidification efficiency of the ice storage air conditioner could decrease by 12.81%, while the cooling efficiency could decrease by 14.11% when the inlet air velocity increases from 5 m/s to 15 m/s. • An air conditioner combining ice storage and compressed air has been developed for refuge chamber. • The conditioner can meet the temperature control requirement of 15 people in a refuge chamber with an initial surrounding rock temperature of 30 °C. • The cooling and dehumidification performance of the conditioner is affected by velocity, temperature and relative humidity of inlet air in turn. • Suggestions for the practical engineering application of the air conditioner are given. [ABSTRACT FROM AUTHOR]

Acceptable temperature is very important for mine refuge chamber (MRC) to ensure the safety of occupants. A novel temperature control scheme combining cold source storage with mine compressed air (MCA) was proposed for MRCs. An experiment was conducted to explore the characteristics of temperature controlling in a MRC via the MCA. Effects of several main factors such as initial surrounding rock temperature (ISRT), ventilation temperature (VT), ventilation rate (VR) and heat rate (HR) on the performance of temperature controlling in the MRC were numerically studied. Results show that: (1) In the MRC, the heat transfer process between the air and walls will reach a dynamic equilibrium within 0.5 h; (2) The ambient temperature in the MRC increases linearly with the square root of time from 1 h to 96 h, the gradient increases with VT and HR but decreases with ISRT and VR; (3) Ventilation with rate of 0.3 m3/min per capita and temperature of 20 °C can meet the temperature control requirements of a MRC located in the sandstone layer with the ISRT of 32.2 °C. An empirical formula for predicting ambient temperature and a ventilation parameter calculation method for meeting the temperature control goal of the MRC are obtained. [ABSTRACT FROM AUTHOR]