https://doi.org/10.6110/KJACR.2026.38.1.1

Chaewon Lim ; Insoo Oh ; Suh-hyun ; Kwon

As global warming intensifies, rising summer temperatures and extended cooling seasons have significantly increased the demand for cooling energy in residential buildings, particularly in multi-family housing. In response, South Korea has promoted Zero Energy Buildings (ZEBs) by enhancing regulations on insulation and window performance. However, the performance of cooling systems is only recommended, rather than strictly regulated, resulting in variations in efficiency and difficulties in quantifying energy savings. Heat pump-type air conditioners, commonly found in ZEBs, exhibit varying performance based on their manufacturing year and capacity. This study utilizes public datasets, including a high-efficiency equipment registry, to analyze the performance trends of electric air conditioners in Korea, focusing on year and capacity. A multiple linear regression model was developed, using Cooling Seasonal Performance Factor (CSPF) and power consumption as key variables. The data were cleaned and categorized into standard and network-connected types. The proposed model exhibited high predictive accuracy, effectively capturing CSPF improvements and efficiency changes based on capacity. This model is anticipated to aid in forecasting the energy-saving potential of high-efficiency cooling systems in ZEBs.

https://doi.org/10.6110/KJACR.2026.38.1.13

Jin Sub Kim ; Dong Hwan Shin ; Jaehwan Shim ; Kong Hoon Lee ; Sangho Sohn ; Wookyoung Kim ; Chanho Song

A high-temperature plate heat exchanger was developed for use in a high-temperature heat pump system operating at 300 °C, utilizing air as the working fluid. Most existing heat transfer correlations for plate heat exchangers are based on water-to-water experimental data, which can lead to performance prediction errors. This underscores the necessity for correlations specifically tailored for air-to-air heat exchangers. To address this, a prototype heat exchanger was constructed based on conventional water-to-water correlations, and performance tests were conducted by varying the inlet pressure between 131 and 517 kPa and the inlet mass flow rate from 0.187 to 0.436 kg/s. As the airflow rate increased, the heat transfer rate rose from 45.7 kW to 103.7 kW, while the heat exchanger effectiveness decreased from 89.1% to 85.4%. From these experimental results, a heat transfer correlation suitable for air-to-air plate heat exchangers was developed. This new correlation significantly reduced the error in heat exchanger effectiveness from 8.0% to 0.45% compared to the conventional water-to-water correlation. When designing high-temperature and low-temperature heat exchangers with 90% effectiveness using this new correlation, the 300 °C high-temperature heat pump system is predicted to achieve a coefficient of performance (COP) of 1.63.

https://doi.org/10.6110/KJACR.2026.38.1.26

Dong-Seon Kim ; Dae-Young Lee

An analytical model has been developed to predict the performance of desiccant wheels. This model is based on an approximate solution derived from a set of linearized governing equations, with the assumption that the desiccant temperature and moisture concentration change over time according to trigonometric functions. The model predicts the outlet conditions of air streams in a silica gel desiccant wheel under typical operating conditions, and the results are compared with those obtained from a numerical model. It is found that the maximum absolute error is ±1.5 K in dry bulb temperature and ±0.6 g/kg in humidity ratio within the ranges of 0.5≤Cr≤1, 1≤Ntu0≤5, 10-2≤Cr*≤10.

https://doi.org/10.6110/KJACR.2026.38.1.41

Chan Hee Han ; Mahdi Koushaeian ; Abdullah ; Hwa Yeong Lee ; Jun Jeong ; Jae Dong Chung

In this study, we integrated a double adsorption cycle structure with a flow control strategy to maintain a constant outlet temperature during the release phase and enhance thermal performance. We compared a single conventional cycle with two types of double cycles (Cascade) and analyzed how constant temperature output (CTO) affected useful energy storage density and heat output. Our analysis was based on a numerical model and included simulations that accounted for seasonal variations in feed water temperature. The results indicated that the Cascade system outperformed the Conventional system, with Cascade 2 achieving the highest performance. Under CTO conditions, Cascade 1 demonstrated the best performance, while Cascade 2 had the highest overall useful energy storage density. Additionally, when comparing our proposed system to phase change material (PCM) storage systems, we found that it offered a greater energy storage density than PCM.

https://doi.org/10.6110/KJACR.2026.38.1.55

Deokgeun Kim ; Hiki Hong ; Sungrag Lee

Geothermal heat pump (GHP) systems encounter several technical challenges during low-temperature operation, such as freeze-bursting of plate heat exchangers (HEX), a reduced coefficient of performance (COP), and difficulties in providing both chilled and hot water simultaneously. These issues stem from non-uniform circulation of the heat transfer fluid, low flow rates, and underutilization of the domestic hot water (DHW) HEX, leading to decreased system efficiency and potential breakdowns. This study proposes a high-efficiency GHP system utilizing a dual-load HEX, which can switch between series and parallel modes based on operational conditions. Furthermore, the total HEX area is effectively increased by incorporating the DHW HEX on both the heat source and load sides. The proposed system can consistently produce chilled water at 4℃ and hot water at 60℃, even under significant temperature differences, resulting in a reduction of return energy costs by up to 40%. Performance tests conducted in accordance with Korean industrial standards (KS) demonstrated excellent results, with a cooling COP of 5.1 and a heating COP of 3.4, indicating superior efficiency compared to conventional systems. These findings underscore the feasibility of a GHP system capable of simultaneously supplying hot and cold water while reducing return energy costs.