https://doi.org/10.6110/KJACR.2025.37.7.315

Dahyuk Shin ; Kyungjin Bae ; Dongchan Lee ; Ohkyung Kwon

This study experimentally investigated effects of half-cycle time, hot water temperature, and cooling water temperature on the performance of a dehumidification-ventilation system with a heat exchanger coated with MOF-based Aluminum Fumarate. Performance indices, including average dehumidification rate, thermal coefficient of performance (COP), and dehumidification coefficient, were evaluated. The optimal half-cycle time was found to be 200 seconds for maximizing the average dehumidification rate and 300 seconds for efficiency indices. Higher hot water temperatures increased the average dehumidification rate, reaching 5.633 g/kgDA at 70℃, but reduced system efficiency. Meanwhile, lower cooling water temperatures improved all performance indices, with maximum values of 5.785 g/kgDA, 0.498 (kg/h)/W, and 0.416 observed for average dehumidification rate, thermal COP, and dehumidification coefficient, respectively, at 20℃. This study provides foundational data for optimizing operating conditions of DCHE systems.

https://doi.org/10.6110/KJACR.2025.37.7.324

Tae Hoon Woo ; Jun Hyun Nam ; Young Il Kim

This study examined the performance of a small diffusion absorption refrigerator (DAR) utilizing environmentally friendly refrigerants with variations in generator heat input. To mitigate ozone layer depletion primarily caused by halogenated refrigerants, organic refrigerants are gaining attention as environmentally sustainable alternatives. To evaluate performance, an experimental setup with a measurement system was constructed. A variable voltage generator was used to control the heating capacity of an electric heater supplying heat to the generator. Results indicated that the maximum coefficient of performance (COP) was achieved at a voltage of 180V and a power input of 51W. This outcome was attributed to characteristics of the two-phase flow regime in the bubble pump. Consequently, identifying optimal operating conditions is essential for maximizing efficiency of diffusion absorption refrigerators.

https://doi.org/10.6110/KJACR.2025.37.7.332

Chang Won Jang ; Dongwoo Kim ; Rin Yun

We simulated a heating system in an electrified apartment to optimize the intermediate temperature for a thermal energy storage tank and minimize energy consumption using TRNSYS. The system, designed for an apartment building with 50 households, consists of a cascade-type and a central supply-type heat pump system. To evaluate performance, we compared the energy consumption of both configurations. The optimization process divided the day into four 6-hour periods and was conducted over a one-month period (January). The highest intermediate temperature, 31℃, was observed between midnight and 6 AM when the heating load was at its peak, while the lowest temperature, 18℃, occurred from noon to 6 PM when the load was minimal. The minimum total energy consumption for January was determined to be 10,607.477 kWh.

https://doi.org/10.6110/KJACR.2025.37.7.342

Seungho Shin ; Jihyeon Cho ; Tageui Hong ; Yeonsook Heo

This study aims to analyze the economic profitability for an electrolysis-based hydrogen production system utilizing power grid supply in relation to international economic trend of hydrogen production. In detail, this study quantified key parameters of an electrolysis-based hydrogen production system impacting installation and operational cost and profit based on return on investment (ROI) via regression-based sensitivity analysis. In order to analyze the economic profitability of hydrogen production according to various energy market context, the electrolysis hydrogen production system was modeled in the TRNSYS program. Key parameters for sensitivity analysis were selected as follows: (1) hydrogen selling price, (2) industrial electricity cost, (3) discount rates from 15 countries. In this study, profit is expressed through the ROI, and key variables such as hydrogen production margin (HPM), system CAPEX ratio, system lifespan, and discount rate were calculated using a linear regression equation (R²: 0.95). As a result, HPM had the most significant impact on ROI (sensitivity: 39.44), while CAPEX and lifespan had minimal effects (sensitivity: 1.67, 1.27), and the discount rate had almost negligible impact (sensitivity: 0.007). These results quantified the impact of key parameters on hydrogen production system, hence this paper can support decision-making in the planning and investment of hydrogen production system.

https://doi.org/10.6110/KJACR.2025.37.7.351

Sowoo Park ; Doosam Song

This study proposes a new evaluation method for assessing the performance of a bidirectional heat recovery ventilation system equipped with a thermal storage element. The method reflects the system’s time-dependent operating characteristics and heat exchange behavior. The existing KS B 6879 standard, based on a steady-state dual-duct system and temperature-based calculation, is unsuitable for single-duct, alternating systems where supply and exhaust occur sequentially. To address this, a cycle-based heat exchange efficiency calculation method is introduced, using time-varying airflow and temperature data based on accumulated outdoor air load. Additionally, a heat recovery efficiency metric is defined to evaluate the thermal performance of the storage element by quantifying the net sensible heat stored and released, excluding duct heat exchange. Experimental results showed that the heat exchange efficiency was approximately 50%, and the heat recovery efficiency of the storage element was 62.72%. It was also observed that airflow delay and extended cycle intervals led to a gradual decline in performance. The proposed dual-index evaluation framework offers a more accurate assessment of such systems and provides a foundation for design, comparison, and optimization of various ventilation solutions.