https://doi.org/10.6110/KJACR.2024.36.12.577

Sang Ha Leigh ; Tae Ha Leigh ; Hyu San Jang ; Chan Kyu Kim ; SeungH yo Beak ; Myoung Souk Yeo

This study analyzed thermal performance of a horizontal mat-type ground heat exchanger (GHE) using capillary tubes through numerical simulations with TRNSYS 18. Although horizontal GHEs are cost-effective alternatives to vertical systems, they typically exhibit lower thermal performances and require more installation space. In consideration of these challenges, this research examined effects of installation depth and inlet fluid temperature on heat exchange efficiency. The TRNSYS 18 model validated against experimental data showed a high accuracy with relative errors between 2% and 5%. Simulations indicated that an increase in installation depth generally resulted in an improvement in heat exchange. However, this improvement stabilized beyond an optimal depth of approximately 7.5 m. In particular, an increase in depth from 1.5 to 4.5 m resulted in a 30% enhancement in heat exchange rate. The maximum performance was recorded at a depth of 7.5 m, with a slight decline of 1.63% to 3.33% observed at 10 m. It was found that higher inlet fluid temperatures reduced heat exchange efficiency due to a diminished temperature differential with the ground. This study concludes that a depth of approximately 4.5 m is needed to achieve a thermal exchange rate of 50 W/m², with 7.5 m providing optimal overall performance.

https://doi.org/10.6110/KJACR.2024.36.12.586

Yong-Il Kwon

Apartments in the city center are built at high densities and on high rises. They are installed with heat recovery unit and kitchen hood. Heating system and conditioners are also being installed to create a comfortable thermal environment. If outdoor air quality or temperature is not kept according to design conditions, windows that make up the exterior wall cannot be opened, creating a closed space. A heat recovery unit has a return diffuser and a supply diffuser. However, a kitchen hood only has an exhaust port. Much research has been conducted on how to supply makeup air for the kitchen hood in a closed space. Methods of supplying makeup air include a method of installing a supply diffuser adjacent to the kitchen hood and a method of installing a supply diffuser on ceiling surface between the kitchen and the living room. This study evaluated effects of makeup air of low velocity supplied to kitchen hood through a supply slot located around the exhaust hood and a window on the exterior wall on ventilation performance of a heat recovery unit. Results confirmed that the condition of supplying makeup air through the window using SVE4 improved exhaust efficiency of the kitchen hood and ventilation performance of the heat recovery unit.

https://doi.org/10.6110/KJACR.2024.36.12.594

Il Kwon Kim ; Hee Won Lim ; Wang Je Lee ; Kyung Ho Lee ; Song SeopL ee ; U Cheul Shin

To prevent economic losses caused by faults in solar thermal systems, continuous monitoring is essential for promptly detecting malfunctions and facilitating recovery. This study proposed a remote monitoring system equipped with simulation-based analysis of solar collector performance and fault detection algorithms validated through on-site testing. The predictive model employed ISO 24194:2022 equations for estimating collector array performance, while fault detection benchmarked the ratio of simulated to actual heat gains under normal operating conditions using Shewhart control charts. Results showed that Shewhart control charts accurately detected operational status of the solar system under various weather conditions. Despite occasional observations exceeding control limits due to weather fluctuations, normal operation resumed, distinguishing between transient deviations and persistent faults. The fault detection approach used in this study based solely on data suggests that if algorithms are implemented through open-source platforms, they could be seamlessly integrated into existing monitoring systems without incurring additional expenses.

https://doi.org/10.6110/KJACR.2024.36.12.606

Ji-Hyoung Kim ; Seon-In Kim ; Young-Joon Park ; Deuk-Woo Kim ; Eui-Jong Kim

The purpose of this study was to develop a multiple regression model for evaluating energy consumption in residential buildings, particularly apartment complexes. With growing concern over global warming and climate change, policies, research, and projects aimed at Net-zero are being implemented worldwide. South Korea is also enforcing the Building Energy Efficiency Certification system (BEEC). However, the BEEC evaluates building energy efficiency based on theoretical energy performance through Energy Use Intensity (EUI), which leads to discrepancies from actual energy usage and hinders precise and objective evaluations. To address this, this study proposed a multiple regression model that could utilize public data to classify building clusters and segment energy uses for a more accurate evaluation. The research process began with collecting public data on apartment complexes in Seoul. After preprocessing the data, clustering techniques were applied to group complexes with similar characteristics. Energy uses were divided into base, cooling, and heating. The model's performance was then quantitatively evaluated. Results of this study provide a complementary framework to BEEC for assessing energy consumption in apartment complexes. They could serve as baseline data for achieving carbon neutrality.

https://doi.org/10.6110/KJACR.2024.36.12.619

Sul Geon Choi

This study addresses strategies for optimizing cooling systems of smart greenhouses to tackle food security issues caused by climate change and population growth. In hot and humid regions like Indonesia, the need for smart greenhouses is increasing and the development of effective cooling systems is essential. This research emphasizes that the performance of air-cooled chillers is highly dependent on outdoor air temperatures. As outdoor air temperatures rise, the efficiency of a chiller decreases. The coefficient of performance (COP) of a chiller drops by about 2% for every 1℃ increase in outdoor air temperature, which leads to reduced cooling efficiency and energy performance. To address this issue, the study proposed the use of thermal energy storage (TES) systems. This strategy involves storing chilled water during the night and using it during the day to reduce cooling energy consumption. Results indicated that increasing the TES capacity to 45% could reduce annual energy consumption by up to 21%. Additionally, a TES capacity of 70% was found to be effective in reducing peak cooling loads of chillers. However, this study also shows that exceeding a 45% TES capacity could lead to increased energy consumption. In conclusion, to efficiently operate cooling systems in smart greenhouses in hot climates, it is crucial to set an optimal TES capacity and implement control strategies that account for changes in outdoor air temperatures.