Because of rapid urbanization, traffic problems, and other factors, underground spaces have been used more in the twenty-first century. Large underground spaces are required for underground city, metro, tunnel, mine, industrial and agricultural engineering, and civil air defense engineering. Underground spaces with varying thermal, ventilation, and lighting environments can face problems of comfort, health, and safety. High temperatures, high humidity, difficulty in flue gas emission, harmful microorganisms, radon, and physical and psychological problems are examples of issues. Air quality control technologies for underground spaces, such as ventilation, dehumidification, natural energy utilization, smoke extraction, and ventilation resistance reduction, are discussed. Ventilation for smoke-proofing/evacuation is also extensively addressed.
Face and neck cooling has been found effective in improving thermal comfort during exercise in the heat despite the fact that the surface area of human face and neck regions accounts for only 5.5% of the entire body. Presently very little documented research has been conducted to investigate cooling the face and neck only to improve indoor thermal comfort. In this study, 16 subjects (8 males and 8 females) used two highly energy efficient wearable face and neck cooling fans to improve occupant thermal comfort in two warm indoor conditions (30 and 32 °C). Results showed that both cooling fans could significantly reduce local skin temperatures at the forehead, face and neck regions. Local thermal sensation votes at the face and neck and the overall thermal sensation votes decreased obviously at 30°C and 32°C. Both cooling fans could raise the acceptable HVAC temperature setpoint to 32.0 °C, which will significantly reduce the energy consumption of HVAC.
Underground spaces were paid more attention in the 21st century. As a special underground space, the development of tunnels was even faster. The damage in tunnel, caused by fire and other hazards, is worse than that in spaces above ground due to construction characteristics of underground spaces. Hot smoke cannot be exhausted in time when a fire occurs in tunnel. Therefore, space temperature rises quickly and flashover occurs. Meanwhile, smoke will be accumulated because of poor ventilation. Incomplete combustion, and production of harmful gases such as CO were caused. This review regarding modelling and design methods, based on the characteristics of tunnel fires, summarizes earlier findings and proposes further study plans.
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