Influence of Relay Chimney Design Parameters on Indoor Natural Smoke Exhaust Characteristics for Shanpian Dwelling: Numerical Simulation Study
Abstract
The Shanpian dwelling (SD), a traditional vernacular architecture in Northwest Yunnan, China, produces continuous smoke during domestic fire use due to open combustion, and the smoke is discharged through the chimney above the open firepit. However, the quantitative relationship between chimney dimensions and smoke extraction efficiency remains underexplored in existing research. This paper establishes a computational fluid dynamic (CFD) based numerical model for SD smoke flow, systematically investigating the impact of chimney design parameters on air changes per hour (ACH, h-1), indoor carbon dioxide concentration (ICDC, ppm), smoke extraction velocity rate (SEVR, m/s) and indoor average temperature of 1.5 m (IAT of 1.5 m, ℃). Results demonstrate that enlarging the chimney sectional area substantially enhances ACH (peaking at 54.97 h-1), yet exerts a negligible influence on flue gas velocity (the change amount is less than 0.25 m/s), suggesting air quality improvement primarily through volumetric flow augmentation rather than velocity elevation. The influence of the length and width of the chimney section on each evaluation index has a critical point (length is 0.75 m, width is 0.55 m). When the length or width of the section is lower than the critical point, its influence on each index is more significant. However, when it exceeds the critical point, its influence on each index gradually slows down. This paper summarizes the smoke flow patterns in SD, points out the linear relationship between indoor air quality and chimney area, and proposes an optimization suggestion that the chimney size should be larger than the firepit section, providing a scientific basis for the ventilation design of traditional dwellings.