https://doi.org/10.6110/KJACR.2025.37.9.409

Doyun Lee ; Wonseok Oh

This study develops a CFD-based simulation model to evaluate microclimate conditions in vertical farming environments, specifically accounting for crop transpiration. Conventional simulation tools like EnergyPlus and TRNSYS rely on zone-level models that lack the spatial resolution necessary to capture microclimate variations near crops. Additionally, traditional CFD models often overlook transpiration, a crucial physiological process that affects energy and moisture exchange. To address these limitations, we created a CFD framework using STAR-CCM+, where crop canopies are modeled as porous media, and transpiration is applied at the cell level through a user-defined function (UDF). Leaf surface temperature is determined by solving coupled energy balance equations that incorporate radiation, sensible heat, and latent heat fluxes. The resulting heat and moisture sources are integrated with the airflow solver. Simulation results under varying inlet relative humidity (30% to 90%) indicate that higher humidity levels decrease transpiration, resulting in increased leaf and air temperatures. Conversely, lower humidity levels enhance transpiration, creating a cooling effect. The model effectively captures spatial heterogeneity in heat and moisture distribution across vertical farms. This transpiration-coupled CFD model serves as a valuable tool for analyzing plant-environment interactions and has practical applications in energy-efficient climate control and the development of smart farming systems.

https://doi.org/10.6110/KJACR.2025.37.9.422

Ilki Yoon ; Sowoo Park ; Doosam Song

This study evaluates changes in indoor particulate matter (PM) concentrations in school kitchens under various ventilation strategies using CONTAM simulation. The simulation includes seven ventilation scenarios based on outdoor PM concentration levels, encompassing natural ventilation, window-type natural ventilation systems, and mechanical ventilation systems, with varying supply-to-exhaust airflow ratios. The results indicate that natural ventilation alone is insufficient for maintaining effective indoor air quality. Specifically, high outdoor PM concentrations can significantly deteriorate indoor air quality when relying solely on natural ventilation. In contrast, mechanical ventilation, with supply airflow at least 60% of the exhaust airflow, effectively controls indoor PM concentrations. Increasing the supply airflow to 80% ensures compliance with indoor air quality standards, even under extreme outdoor conditions. These findings suggest that mechanical ventilation is crucial in high-load environments, such as school kitchens, and provide foundational data for optimizing ventilation system design.

https://doi.org/10.6110/KJACR.2025.37.9.436

Beungyong Park ; Minho Kim ; Sung Lok Do ; Suh-hyun Kwon

Radiant floor heating uses a boiler to warm water, which is then circulated through the floor to heat indoor spaces. Traditionally, a single-point thermostat controls the water temperature and flow rate, resulting in uneven heating and increased energy consumption. A recent study has introduced MRT sensing controller technology, which measures the average radiant temperature across the entire room to optimize heating and energy efficiency. Comparative experiments with the traditional system highlighted its advantages. MRT sensing control technology provides more consistent floor surface temperatures, enhancing indoor comfort. Positioned in the center of the room, it reduced energy consumption by approximately 10%, leading to cost savings and a more eco-friendly heating solution. In summary, MRT sensing control technology improves radiant floor heating by ensuring uniform comfort, lowering energy costs, optimizing boiler use, and promoting environmental sustainability, in line with the trend toward energy-efficient and environmentally responsible heating solutions.

https://doi.org/10.6110/KJACR.2025.37.9.446

Joo Hwan Ha ; Geun Sang Park ; Tae Sung Kim

This study examines the optimization of flow uniformity in a large-scale corona discharge gas reactor by assessing various baffle geometries and positions using Computational Fluid Dynamics (CFD). Three types of baffles (A, B, and C), each with different central blockage areas, were designed to evaluate their impact on internal velocity distribution across seven axial positions (0-300 mm). The Velocity Uniformity Index (UI) was used as a quantitative measure of flow uniformity. The results indicated that Baffle A, positioned at the 0 mm location, achieved the highest UI of 0.967, effectively flattening the velocity profile by reducing the differences between core and peripheral flows. Conversely, Baffle C, which has the largest central blockage, caused significant flow non-uniformity when placed in the front region, leading to excessive peripheral flow concentration and stagnation at the center. These findings emphasize that both the geometry and axial positioning of baffles are crucial for reactor performance and must be optimized together to achieve a balance between flow uniformity and pressure drop. The study offers practical insights for enhancing gas-phase reactor design through effective internal flow management.

https://doi.org/10.6110/KJACR.2025.37.9.452

Ja Kang Yang ; Sun Hyo Park ; Sang Ki Jin

This study investigates the current practices and challenges associated with calculating and paying indirect costs and pre-input costs in mechanical equipment construction projects. It also proposes institutional and practical measures for improvement. As the importance of mechanical equipment construction grows in response to national policies promoting carbon neutrality and energy efficiency, persistent structural issues hinder the accurate reflection of these costs in cost estimation systems, largely due to the complexity and long duration of such projects. Through literature reviews, legal analyses, and case surveys of construction professionals, this study identifies key issues, including the omission of indirect costs in design documents and the failure to pay these costs during project schedule extensions. Based on these findings, the study offers a comprehensive improvement strategy that includes short-, medium-, and long-term initiatives, such as revisions to cost breakdown sheets, development of response manuals, implementation of training programs, and amendments to relevant laws. The results of this study are expected to enhance transparency in cost estimation and promote fair contractual practices in mechanical construction, ultimately contributing to future institutional reforms.