Browsing by Author "Supervisor 2: Kim Young Suk, Ph.D"

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    Numerical Analysis of Heat Transfer and Thermal Efficiency in a Traditional Mongolian Ger: Influence of Chimney Geometry
    (German-Mongolian Institute for Resources and Technology (GMIT), 2026) Molomjamts, Oyunjargal; Supervisor 1: Sungchil Lee, Ph.D, P.E; Supervisor 2: Kim Young Suk, Ph.D
    This thesis presents a comparative computational fluid dynamics (CFD) investigation into the heat transfer performance of chimney geometries used in Mongolian traditional ger (yurt) heating systems. Using ANSYS Fluent 25 with a two-dimensional axisymmetric transient model incorporating the SST k-ω turbulence model and the Discrete Ordinates radiation model, ten simulation cases were conducted across three categories of geometric variation: chimney inner diameter (0.08 m to 0.12 m), number of external horizontal annular fins (5, 7, and 9), and coaxial cylindrical extension (0.2 m and 0.25 m). The model was validated against experimental field measurements of a coal-heated ger reported by Purev et al. (1) in 2022, achieving agreement within 0.79% at the reference monitoring point. Results for the diameter variation indicate a irregular relationship between chimney diameter and indoor temperature, with a minimum observed at 0.10 m and recovery at 0.12 m due to recirculation effects and increased stove radiation. Chimney wall heat flux increased consistently with diameter, while draft velocity decreased. For the annular fin configurations, contrary to classical fin theory, all finned cases reduced total heat transfer by approximately 60% relative to the bare cylinder baseline. This is attributed to the perpendicular orientation of horizontal fins obstructing buoyancy-driven natural convection and suppressing internal draft through a coupled thermal-fluid feedback mechanism. For the coaxial cylindrical extension, the 0.2 m diameter extension achieved a 16.9% improvement in total convective heat output over the baseline by adding sufficient dissipating surface area, while the 0.25 m extension reduced output by 29.0% due to excessive draft suppression. These results provide the first geometry-based numerical design investigation for ger chimneys, suggesting that the current MASM standard diameter of 0.10 m is thermally suboptimal (though, at the same time it could be the best configuration in the context of quality of indoor air) and that a well-sized coaxial extension represents the most promising configuration for enhancing ger heating efficiency.