Gas leakage accidents occur frequently in confined spaces, and heavy gases with a relative density greater than 1.15 among hazardous gases and greenhouse gases are commonly stored in confined spaces. However, atmospheric pollutant emission standards are becoming more stringent, and it is essential to remove heavy gas after accidents while reducing emissions to the atmosphere. This study proposes using a heavy gas collection tank (HGCT) to safeguard the internal environment and minimize emissions to the atmosphere. The capture efficiencies applicable to heavy-gas environments under different ventilation strategies are derived. This research analyzes the impact of the exhaust rate, leakage rate, density of heavy gas, and air supply modes on the indoor concentration distribution. The results demonstrate that the mass flow rate of heavy gas into the exhaust is positively correlated with the exhaust rate, but the gas from the exhaust system contains more air. The exhaust rate should be greater than four times the space volume per hour; otherwise, heavy gas above 1000 ppm accumulates to a height of 0.67 m at ground level. Finally, attachment ventilation as make-up air helps to reduce upstream heavy gas accumulation and reduces the extension of heavy gas along the room width. Combining an HGCT with floor slope and attachment ventilation achieves an efficiency of 96.28%. This study provides valuable insights and references for preventing hazardous heavy gas leakage.

The thermal buoyancy generated by the difference in air density in a building can drive hot-pressed natural ventilation, which is an energy-efficient means of ventilation used to obtain higher air quality. Therefore, the effect of a single-point heat source with limited sides at different heights on stratified flow was studied in a naturally ventilated room in this paper. Based on the classical plume diffusion law of an independent point heat source and the mirroring principle, a calculation model of the thermal stratification height with a restricted source elevated to different levels was derived and validated. The quantitative effects of the heat source height from the floor, the effective opening area and other factors on the natural ventilation of hot pressure were analyzed. A threshold x_T for the separation between a point source and a sidewall was defined to estimate whether the thermal plume was independent or restricted by a sidewall. And a method for calculating the threshold x_T was obtained. This research can provide a reference basis for designing natural ventilation for buildings with a restricted heat source at different levels to achieve a desired indoor environment.

In practical engineering, inclined building walls are often presented due to their functional and aesthetic needs. A reasonable air distribution design is essential for creating a satisfactory indoor environment in such buildings. In the present study, inclined walls with a variable inclination angle β were used as the research object to explore a novel air supply mode. Visualization experiments and numerical simulations were conducted to investigate the induced airflow, such as the airflow pattern, the airflow characteristics (maximum jet velocity decay and jet spreading rate) and the ventilation effect (vertical air temperature difference, draft rate, air diffusion performance index). The results show that the "air lake" phenomena occurred over the floor, which resembles the displacement ventilation to some extent. The proposed air supply mode has a good ventilation effect and could be applied to building spaces with inclined walls. The current study can be used as a reference for ventilation design in buildings with inclined walls.

Housing walls are often designed with a curved shape to improve their appearance and meet functional demands. The creation of a comfortable environment in an indoor space with curved walls poses a new challenge for air distribution design. This paper uses the brachistochrone curved wall as an example to explore the applicability of attachment ventilation mode in buildings with specially shaped enclosures. Experiments and numerical simulations were applied to investigate the airflow characteristics of this particular ventilation mode. For the attached air curtain ventilation based on a brachistochrone curved wall, the semi-empirical equations for the maximum jet velocity decay, maximum jet temperature decay, and jet spreading rate were obtained. The results show that the proposed air supply mode can be applied to the brachistochrone curved wall. The current study motivates further research on the design of ventilation systems in buildings with specially shaped enclosures.

In the design of air conditioning and ventilation for an underground workshop, such as hydropower station underground powerhouse, mechanical ventilation was frequently applied to control air quality for large and mutually connected spaces of Dynamo floor, Generatrix floor, Hydraulic floor and Cochlea floor. In this paper, based upon the similarity criterion, the dimensionless yield criterion was used to explore the airflow effectiveness of large spaces mutually connected and a 1:50 small-scale model of the main powerhouse was built which was used to study and analyze the airflow distribution in large spaces mutually connected. A series of parameters was obtained from the experiment, and here we discussed following conditions: three air supply velocities: V/V₀=0.75, V/V₀=1 and V/V₀=1.25 (V₀ is the designed air velocity in this model) and three heat release rates: Q/Q₀=0.75, Q/Q₀=1 and Q/Q₀=1.25 (Q₀ is the designed heat load in this model). The environmental parameters of a workspace at different floors were acquired to study the effect of mechanical ventilation on the temperature field under different air velocities and heat release rates. The experimental results show that the heat release rate had a significant effect on the main power house temperature distribution. An appropriate air supply velocity could effectively optimize workplace temperature distribution under high-heat intensity environment. Energy efficiency coefficient and non-uniform temperature coefficient were predicted and the optimal design parameters (0.75V₀, 1Q₀) were recommended after 9 kinds of tests were conducted. The experimental research is helpful to the ventilation design of large and mutually connected spaces, such as Dynamo, Generatrix, Hydraulic and Cochlea floors in hydropower station underground powerhouse.

Fire in underground structures can result in devastating consequences in terms of both economic damage and loss of life. Hydro-electric plants are typically underground windowless structures. In an underground hydropower station, the busbar corridor connects the busbar layer in the main power plant with the main transformer chamber. This structure forms the channel that is crucial for electrical power transmission. In this paper, a computational method, Fire Dynamics Simulator (FDS), was carried out on a model of a two-story busbar corridor structure based on actual fire test results as a validation case. Twenty-four prediction conditions were taken into account to evaluate the original design of the exhausting system and optimize the busbar corridor modeled smoke control scheme. In those predictions five factors were varied: the heat release rate (HRR), the story height, the air change rate (ACH), the exhaust outlet positions and the airflow inlet positions. Since toxic compounds, especially carbon monoxide, endanger evacuating people in fire scenarios, the carbon monoxide (CO) concentration was reported and used throughout this study as an indicator of the safety of occupants in the corridor. Of the five varied factors it was found that the story height and the airflow inlets with natural ventilation influenced the smoke suppression and control. For the story height of 6.0 m, the filling time is 52 s more than the story height of 4.5 m. The CO concentration of opening set upstairs only is twice as much of the design condition. Opening set downstairs only can exhaust smoke faster for occupied area.

In order to clarify the air temperature distribution and air velocity distribution of a hydroelectric generating powerhouse in the mechanical ventilation mode, detailed ventilation experiments were conducted using a 1:20 small-scale model of a pumped-storage hydroelectric power station. In this model, we arranged fifty-seven circular inlets in double and triple rows to simulate the air supply pattern in a typical powerhouse. Six combinations of the inlets, and three air supply rates (28 m³/h, 56 m³/h, and 112 m³/h) were selected to determine the effect of the inlets’ arrangement and the air supply rates on the air distribution in the occupied zone of the powerhouse. A dimensionless method was adopted to process the acquired data of the air temperature and air velocity. The results revealed that the inlets’ arrangements and the air supply velocity had a significant influence on the air distribution in the powerhouse. Simultaneously, the ventilation efficiency of four heat sources was studied in the optimum case, i.e. the most effective air supply rate is 112 m³/h among the three tested values. The results of the experiments revealed that the air distribution was nearly independent of adjustable heat release rates. Our findings in this work may offer a significant advance in the understanding of ventilation system designs for hydroelectric powerhouses.

In Chinese commercial kitchens, a large amount of moisture and heat is produced and must be removed, which can require ventilation rates resulting in huge levels of energy consumption. Excessive airflow rates can increase unnecessary energy consumption and system life-cycle costs. For many middle and small scale commercial kitchens in China, the indoor, thermal environment is far worse than acceptable levels. The use of an efficient kitchen hood is essential to ensure a comfortable working environment and better energy conservation. In this study, many types of hood shapes and side panels were developed to improve the capture efficiency of traditional Chinese style cooking hoods. The arrangement of the exhaust ducts was also investigated. Basic site tests and computational fluid dynamics (CFD) analysis were conducted. The simulated results showed that increasing hood volume did not improve capture performance. However, side panels did improve the capture efficiency, especially at higher positions. In addition, when the exhaust opening was located at the rear of the hood, the hood capture efficiency improvement was enhanced.