https://doi.org/10.6110/KJACR.2026.38.7.357

Seongmin Choi ; Nayoung You ; Honghyun Cho

This study numerically investigates the thermal performance of a sensible thermal energy storage tank, focusing on the impact of diffuser geometry, using computational fluid dynamics (CFD). A rectangular, water-based storage tank was analyzed under a low-temperature charging condition, considering four diffuser configurations: Plate-type, H-type (hole), H-type (slot), and I-type. The results demonstrate that diffuser geometry significantly influences thermal stratification and charging performance. The Plate-type diffuser showed relatively stable stratification during the early and intermediate charging stages, but its performance declined in the late stage due to limited hot fluid discharge near the tank's upper corners. Conversely, the H-type (hole) diffuser achieved the fastest charging performance, reaching 99% SOC in 5573.5 seconds while maintaining stable stratification throughout the process. The I-type diffuser, however, led to excessive fluid mixing, resulting in degraded stratification and the slowest SOC increase. These findings indicate that, based on SOC performance, the H-type (hole) diffuser is the most effective configuration for enhancing charging performance in rectangular sensible thermal energy storage tanks.

https://doi.org/10.6110/KJACR.2026.38.7.366

Huijing Yan ; Doo Sam Song

The global pursuit of carbon neutrality by 2050 has positioned the electrification of heating systems as a critical strategy for reducing greenhouse gas emissions in the building sector. Heat pumps are particularly promising for green retrofits of public buildings, though their performance varies with regional climate. This study assesses the heating energy consumption, energy cost, and payback period when replacing conventional gas boilers with heat pump systems in an existing public daycare center across South Korea's central, southern, and Jeju regions. To ensure a consistent regional comparison, energy performance simulations were conducted using the ISO 13790?based Energy# model under identical building and operational conditions. The results indicate that heat pump application reduces annual heating energy consumption by approximately 73% and heating energy costs by about 33% compared to gas boilers. Economic analysis reveals a payback period of approximately 3.5 years in central regions and around 6 years in southern and Jeju regions, primarily due to variations in regional heating demand. These findings confirm the economic viability of adopting heat pumps and offer quantitative data to support region-specific deployment strategies for decarbonizing public buildings.

https://doi.org/10.6110/KJACR.2026.38.7.375

Byungki Jeon ; JaeHyeok Heo ; HongJin Joo ; DeukWon Kim ; JongKyu Kim

This study formulates the daily operation of building cooling systems as a time-coupled discrete scheduling problem to evaluate the applicability of the Quantum Approximate Optimization Algorithm (QAOA). The optimization objective is to minimize electricity costs while satisfying thermal comfort constraints during occupied hours, with hourly heat pump output levels defined as upper-level control variables. Initially, a baseline single-zone problem is examined, demonstrating that grid search, particle swarm optimization (PSO), and QAOA all converge to the same optimal solution. Subsequently, extended scenarios are introduced by gradually increasing the number of zones and thermal energy storage capacity. This allows for a comparison of the exploration characteristics of the algorithms under increasing physical system complexity. Simulation results indicate that, in these extended problems, PSO tends to concentrate search outcomes within limited regions of the cost?comfort space. In contrast, QAOA consistently identifies Pareto-optimal solutions across a broader cost range. These findings suggest that QAOA can be an effective alternative for discrete scheduling problems in building energy management, especially in situations with limited data dependency.

https://doi.org/10.6110/KJACR.2026.38.7.393

Jong Seok Yoon ; Young Il Kim

This study analyzed infiltration characteristics driven by thermal buoyancy during winter heating in a 604 m³ auditorium. Temperature, humidity, and CO₂ concentration were measured under five conditions: natural ventilation, and outdoor air damper opening ratios of 0% and 30% (both with and without heating). The lowest air change rate was observed during natural ventilation at 0.197 h?¹. With the outdoor air damper at 0%, the air change rate during heating was 1.127 h?¹, which was 0.351 h?¹ higher than the non-heating condition (0.776 h?¹). At a 30% damper opening, the air change rate during heating was 1.351 h?¹, an increase of 0.254 h?¹ compared to the non-heating condition (1.097 h?¹). This increase is attributed to the elevated indoor temperature during heating, which creates a density difference between indoor and outdoor air, leading to pressure differences. Consequently, the outdoor pressure becomes higher than the indoor pressure in the lower part of the building envelope, causing infiltration, while the outdoor pressure becomes lower in the upper part, resulting in exfiltration. An analytical model incorporating thermal buoyancy was developed to calculate infiltration through five doors and envelope cracks. The model's results showed excellent agreement with measurements, with errors of 0.14% at 0% opening and 0.26% at 30%. The proposed analytical model can effectively predict infiltration rates during heating operation.

https://doi.org/10.6110/KJACR.2026.38.7.404

Kyung Joo Cho ; Yo Sun Yun ; Sung Mo Sea ; Dae Hee Jan

This study examines score attainment patterns within the Energy and Environmental Pollution (EP) category of Korea's Green Standard for Energy and Environmental Design (G-SEED) certification system for residential buildings. We analyzed 3,018 newly constructed residential buildings?encompassing general and multi-family housing?that received preliminary G-SEED certification between 2017 and 2024. Certification records were reviewed based on building type and certification grade, focusing on average achieved scores, score distributions per assessment item, and the prevalence of high- and zero-score items within the EP category.Our results indicate that the mandatory "Energy Performance" item consistently achieved high scores and was crucial in differentiating certification grades, especially for higher-grade buildings. Conversely, optional items concerning renewable energy utilization and energy monitoring/management systems showed high zero-score ratios across both housing types. This suggests limited feasibility or insufficient institutional incentives for their adoption. Although renewable energy items contributed somewhat to grade differentiation in multi-family housing, their overall impact on total EP scores was marginal. These findings suggest that the current EP evaluation framework prioritizes compliance with minimum energy performance requirements over encouraging the broader adoption of advanced energy technologies and operational strategies. The study highlights structural limitations in the EP category's scoring structure and item composition, emphasizing the need to revise evaluation criteria. Such revisions should aim to strengthen performance differentiation and promote more effective energy and environmental outcomes in residential G-SEED certification.