Some Effects on the Temperature of the Mine Air at the Heading Face

Currently, with the increase in mining output leading to deeper mining levels, the volume ofheading face serving production has also increased. The thermal environment tends to worsen whendigging deep due to the geothermal's effect, which increases the air temperature at the heading face.According to QCVN01/2011-BCT, the temperature at the heading face is not allowed to exceed 300C. Toensure this, in Vietnam today, mainly forced ventilation method uses local fans to provide a clean amountof air to ensure a favorable environment for workers. With the forced ventilation method, the duct positionis usually arranged on the side, and the distance from the duct mouth to the heading face is determined toensure that l < 6√s. In this study, a numerical simulation method by Ansys CFX software is applied tostudy the influence of several factors such as duct position, air temperature of duct, and roughnesscharacteristics of roadway on the temperature of the mine air at the heading face. The models are set upwith six duct positions and four air temperature of duct parameters. Model 1 (y =1.1 m) is better thanmodels 2 to 6 in terms of temperature distribution and the lowest temperature values. Four models havedifferent wind temperatures, and we can see the significant influence of the inlet air temperature of theduct on the thermal environment of the heading face. The results show that with the model T = 297.15K,the temperature value on the roadway length is guaranteed as specified < 303K. The result is a referencefor determining the duct position and cool for the high-temperature heading face.

Experimental investigation of bubble formation and motion mechanism near the moonpool

When a research ship sails at a high speed, there is relative motion between the ship and fluid. The ship is slammed by the fluid. To reduce the direct impact of the fluid, sonar is installed in the moonpool, and acoustic detection equipment is installed along the research ship bottom behind the moonpool. However, during high-speed sailing, a large number of bubbles form in the moonpool. Some bubbles escape from the moonpool and flow backward along the bottom of the ship. When a large number of bubbles are around the sonar and acoustic detection equipment, the equipment malfunctions. However, there have been few studies on bubble formation in the moonpool with sonar and distribution along the ship bottom behind the moonpool. Therefore, a related model was developed and prototype tests were carried out in this study. The appropriate similarity criteria were selected and verified to ensure the reliability of the experiment. Considering the influences of speed, sonar, moonpool shape, and draft, the reason and mechanism of bubble formation in a sonar moonpool were studied. An artificial ventilation method was used to simulate a real navigation environment. Because the bubbles are in a bright state under laser irradiation, the bubbles can be used as tracer particles. A high-speed camera captured illuminated bubbles. The distribution mechanism of bubbles along the ship bottom behind the moonpool was investigated using particle image velocimetry under the influence of the moonpool shape and sailing speed. The model experimental results agreed well with those of the prototype test. The air sucked into the water was the dominant factor in bubble formation in the moonpool. The bubbles were distributed in a W shape under the ship bottom.

VENTILATION METHOD FOR LONG BLIND DRIFTS WITH LONGITUDINAL BAFFLES

The study focuses on aerodynamic processes in long blind drifts ventilated owing to ejection effect generated thanks to construction of longitudinal baffles. The numerical modeling of air distribution at the junction with a blind drift with a longitudinal baffle is implemented in ANSYS. The change in the local air drag in case of forward and reverse air flows is shown. The velocity variation in air flow in a long blind drift with adjustment of ventilation efficiency by alteration of the opening angle of the longitudinal baffle flap is estimated. Based on the obtained results, the author shows that construction of longitudinal baffles allows efficient ventilation in long blind drifts owing to the ejection effect, without forced ventilation arrangement.

Research on the construction ventilation scheme of concealed subway station

With the development of underground transportation, in order to reduce the impact on the surrounding environment and traffic, Hejiaying subway island station adopts the concealed excavation method. During the construction process, considering the construction method, tunnel layout, ventilation requirements, and the construction working face as a multi-conductor cave, more stringent requirements are put forward for the construction ventilation of the tunnel. Through the combination of theoretical calculation and numerical simulation, a ventilation method suitable for the actual construction conditions at the site was developed. After applying the scheme to practice, the feasibility of the scheme was verified through the determination of field data, and the improvement of the construction environment for tunnel personnel was achieved, which has certain reference value for similar projects.

A review of common natural ventilation and evaporative cooling systems for Greenhouses and the Nigerian reality

Greenhouses simulate the "desired" environment for successful growth and development of plants. They, by design, achieve this desired environment by supplying the necessary climatic inputs needed by the plants to strive and at the same time exclude factors impeding the growth of plants, hence it is called a controlled environment. One of the common and most desired attribute of the greenhouse is its ability to provide effective cooling to the plants. This paper reviewed, extensively, the concept of evaporative cooling as applied in greenhouses. Factors like Vapor Pressure deficit (VPD), Relative Humidity, Ambient Temperature were also discussed with regards to its effects on the efficiency of the evaporative cooling system. The efficiencies of the Fan and Pad System and the Fog systems were reviewed and compared with their consequent dependence on factors like nozzle spacing, nozzle length, saturation efficiency of pad material etc. The Natural Ventilation method was also reviewed as a "stand alone " greenhouse cooling method and as an augmentation to other cooling systems. Factors like rate of air exchange, total area of vents, wind speed, vent opening angles etc. were also discussed in line with their effects on the effectiveness of the Natural ventilation method. The Nigerian Perspective on Greenhouses and its Cooling methods was also discussed with reference to local development of evaporative coolers as well as its importation, its affordability, management, availability and appliance to the Nigerian farming culture.

A COMPARISON OF MOUTH-TO-MOUTH, MOUTH-TO-POCKET FACE MASK AND BAG VALVE MASK VENTILATION DURING LIFEGUARDS’ CPR: A MANIKIN STUDY

Aim: To compare the effectiveness of ventilation of each of three methods: mouth-to-mouth ventilation using a foil face mask with a filter pad, mouth-to-mask technique with a pocket face mask and bag valve mask ventilation using a self-inflating bag and a face mask, performed during CPR by qualified non-medical rescuers. Material and methods: Ventilation effectiveness was assessed on manikin and compared for mouth-to-mouth, mouth-to-mask and bag valve mask ventilation method. 46 qualified non-medical rescuers-lifeguards participated in the study. Tidal Volume of 0,4-0,7L was considered as effective. The length of chest compressions pauses was recorded. The ventilation methods were also evaluated subjectively by participants in the questionnaire. Results: Effectiveness 90,75% vs. 92,38% vs. 69,5%; average number of effective rescue breaths: 7,26 vs. 7,39 vs. 5,65; average length of chest compressions pause: 7,7s vs. 8,1s vs. 9,9s for MTM, MPFM and BMV respectively. MPFM method was considered as the easiest, the second in terms of the difficulty in use was MTM, and BMV was described as the most difficult to use. Conclusions: Artificial ventilation using the pocket mask, in the course of resuscitation performed by one qualified non-medical rescuer, e.g. the water lifeguard, is an effective method ensuring adequate tidal volume and is more effective than mouth-to-mouth method and bag valve mask ventilation.