Design and practice of indoor gas leak diffusion simulation experiment based on CFD
[Objective]This study aims to design and implement a computational fluid dynamics(CFD)-based simulation experiment on residential indoor gas leakage dispersion,exploring the effects of different factors on the dispersion process.As urbanization accelerates and natural gas usage increases,indoor gas leakage accidents pose severe threats to residents'safety.Although on-site experiments are limited by safety concerns and costs,CFD simulations offer a powerful alternative.This experiment is designed to deepen students'understanding of gas leakage dispersion processes,help them master CFD techniques for engineering applications,and enhance their safety awareness and risk assessment skills.[Methods]A two-bedroom apartment layout was modeled using ICEM software to simulate realistic residential indoor gas leakage scenarios.ANSYS Fluent was used for numerical simulations,and four scenarios were designed to investigate the effects of ventilation,leakage rate,and gas type on dispersion patterns.The realizable k-ε turbulence model was used,with second-order upwind schemes for spatial discretization and the SIMPLE algorithm for pressure-velocity coupling.The scenarios included the following:(1)unventilated methane leakage at 0.2 g/s,(2)natural ventilation at an air change rate(ACH)of 2 h-1,(3)increased leakage rate of 0.4 g/s,and(4)liquid petroleum gas(LPG)leakage to compare dispersion patterns between different gas types.[Results]The study revealed significant insights into gas dispersion patterns under various conditions.In the unventilated methane leakage scenario(i.e.,0.2 g/s),kitchen concentrations reached the alarm threshold(i.e.,0.7%mass fraction)above 1.7 m height after 50 minutes.By the 5-hour mark,the kitchen ceiling concentration peaked at 2.67%,approaching the lower explosive limit.The introduction of ventilation(i.e.,2 h-1ACH)significantly altered the dispersion dynamics,reducing the kitchen's peak concentration by 62%compared to unventilated conditions after 2 hours of leakage.After 5 hours of ventilated leakage,only the upper part of the kitchen exceeded the alarm threshold.Increasing the leakage rate to 0.4 g/s resulted in a more rapid concentration buildup,with the alarm threshold in the kitchen reached after just 2 minutes.At the 1-hour mark,maximum concentrations were 57%higher than in the lower leakage rate scenario.LPG leakage(i.e.,0.2 g/s)exhibited distinctly different behavior due to its higher density.A significant vertical concentration gradient was observed in the kitchen,with higher concentration at the floor level.The lateral spread of LPG was also slower compared to that of methane.These findings have important implications for gas detector placement.For methane,detectors should be positioned just below the ceiling for fast response.Conversely,for LPG,floor-level detectors will be more efficient.[Conclusions]This CFD-based simulation experiment has provided valuable quantitative insights into indoor gas leakage dispersion under various conditions.The findings underscore the critical role of ventilation,leakage rate,and gas properties in determining dispersion patterns and concentration buildup.This study demonstrates the effectiveness of CFD simulations in analyzing complex indoor environments and has significant implications for residential gas safety management and accident prevention.By integrating such simulation experiments into engineering education,students can enhance their practical skills and prepare for real-world challenges in their future careers.The flexible experiment design allows for the exploration of multiple influencing factors,making it suitable for inquiry-based learning and fostering students'innovative thinking and research skills.
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